Clinical safety of the ProMRI pacemaker system in patients subjected to head and lower lumbar 1.5-T magnetic resonance imaging scanning conditions.

PubMed

Bailey, William M; Rosenthal, Lawrence; Fananapazir, Lameh; Gleva, Marye; Mazur, Alexander; Rinaldi, C A; Kypta, Alexander; Merkely, Béla; Woodard, Pamela K

2015-06-01

Permanent cardiac pacemakers have historically been considered a contraindication to magnetic resonance imaging (MRI). The purpose of the ProMRI/ProMRI AFFIRM Study, which was a multicenter, prospective, single-arm, nonrandomized study, was to evaluate the clinical safety of the Biotronik ProMRI Pacemaker System under specific MRI conditions. The ProMRI Study (in the United States) and the ProMRI AFFIRM study (outside the United States) with identical design enrolled 272 patients with stable baseline pacing indices implanted with an Entovis or Evia pacemaker (DR-T or SR-T) and Setrox or Safio 53-cm or 60-cm lead. Device interrogation was performed at enrollment, pre-MRI and post-MRI scan, and 1 and 3 months post-MRI. End-points were (1) freedom from MRI- and pacing system-related serious adverse device effects (SADEs) through 1 month post-MRI, (2) freedom from atrial and ventricular MRI-induced pacing threshold increase (>0.5 V), and (3) freedom from P- and R-wave amplitude attenuation (<50%), or P wave <1.5 mV, or R wave <5.0 mV at 1 month post-MRI. Two hundred twenty-six patients completed the MRI and 1-month post-MRI follow-up. No adverse events related to the implanted system and the MRI procedure occurred, resulting in an SADE-free rate of 100.0% (229/229, P <.001). Freedom from atrial and ventricular pacing threshold increase was 99.0% (189/191, P = .003) and 100% (217/217, P <.001), respectively. Freedom from P- and R- wave amplitude attenuation was 99.4% (167/168, P <.001) and 99.5% (193/194, P <.001), respectively. The results of the ProMRI/ProMRI AFFIRM studies demonstrate the clinical safety and efficacy of the ProMRI pacemaker system in patients subjected to head and lower lumbar MRI conditions. Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Safety and utility of magnetic resonance imaging in patients with cardiac implantable electronic devices.

PubMed

Strom, Jordan B; Whelan, Jill B; Shen, Changyu; Zheng, Shuang Qi; Mortele, Koenraad J; Kramer, Daniel B

2017-08-01

Off-label magnetic resonance imaging (MRI) for patients with cardiac implantable electrical devices has been limited owing to concerns about safety and unclear diagnostic and prognostic utility. The purpose of this study was to define major and minor adverse events with off-label MRI scans. We prospectively evaluated patients with non-MRI-conditional cardiac implantable electrical devices referred for MRI scans under a strict clinical protocol. The primary safety outcome was incidence of major adverse events (loss of pacing, inappropriate shock or antitachycardia pacing, need for system revision, or death) or minor adverse events (inappropriate pacing, arrhythmias, power-on-reset events, heating at the generator site, or changes in device parameters at baseline or at 6 months). A total of 189 MRI scans were performed in 123 patients (63.1% [78] men; median age 70 ± 18.5 years; 56.9% [70] patients with implantable cardioverter-defibrillators; 33.3% [41] pacemaker-dependent patients) predominantly for brain or spinal conditions. A minority of scans (22.7% [43]) were performed for urgent or emergent indications. Major adverse events were rare: 1 patient with loss of pacing, no deaths, or system revisions (overall rate 0.5%; 95% confidence interval 0.01-2.91). Minor adverse events were similarly rare (overall rate 1.6%; 95% confidence interval 0.3-4.6). Nearly all studies (98.4% [186]) were interpretable, while 75.1% [142] were determined to change management according to the prespecified criteria. No clinically significant changes were observed in device parameters acutely after MRI or at 6 months as compared with baseline across all patient and device categories. Off-label MRI scans performed under a strict protocol demonstrated excellent short- and medium-term safety while providing interpretable imaging that frequently influenced clinical care. Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Safety and utility of magnetic resonance imaging in patients with cardiac implantable electronic devices

PubMed Central

Strom, Jordan B.; Whelan, Jill B.; Shen, Changyu; Zheng, Shuang Qi; Mortele, Koenraad J.; Kramer, Daniel B.

2017-01-01

BACKGROUND Off-label magnetic resonance imaging (MRI) for patients with cardiac implantable electrical devices has been limited owing to concerns about safety and unclear diagnostic and prognostic utility. OBJECTIVE The purpose of this study was to define major and minor adverse events with off-label MRI scans. METHODS We prospectively evaluated patients with non–MRI-conditional cardiac implantable electrical devices referred for MRI scans under a strict clinical protocol. The primary safety outcome was incidence of major adverse events (loss of pacing, inappropriate shock or antitachycardia pacing, need for system revision, or death) or minor adverse events (inappropriate pacing, arrhythmias, power-on-reset events, heating at the generator site, or changes in device parameters at baseline or at 6 months). RESULTS A total of 189 MRI scans were performed in 123 patients (63.1% [78] men; median age 70 ± 18.5 years; 37.0% [70] patients with implantable cardioverter-defibrillators; 21.8% [41] pacemaker-dependent patients) predominantly for brain or spinal conditions. A minority of scans (22.7% [43]) were performed for urgent or emergent indications. Major adverse events were rare: 1 patient with loss of pacing, no deaths, or system revisions (overall rate 0.5%; 95% confidence interval 0.01–2.91). Minor adverse events were similarly rare (overall rate 1.6%; 95% confidence interval 0.3–4.6). Nearly all studies (98.4% [186]) were interpretable, while 74.9% [142] were determined to change management according to the prespecified criteria. No clinically significant changes were observed in device parameters acutely after MRI or at 6 months as compared with baseline across all patient and device categories. CONCLUSION Off-label MRI scans performed under a strict protocol demonstrated excellent short- and medium-term safety while providing interpretable imaging that frequently influenced clinical care. PMID:28385671

A MR-conditional High-torque Pneumatic Stepper Motor for MRI-guided and Robot-assisted Intervention

PubMed Central

Chen, Yue; Kwok, Ka-Wai; Tse, Zion Tsz Ho

2015-01-01

Magnetic Resonance Imaging allows for visualizing detailed pathological and morphological changes of soft tissue. This increasingly attracts attention on MRI-guided intervention; hence, MR-conditional actuations have been widely investigated for development of image-guided and robot-assisted surgical devices under the MRI. This paper presents a simple design of MR-conditional stepper motor which can provide precise and high-torque actuation without adversely affecting the MR image quality. This stepper motor consists of two MR-conditional pneumatic cylinders and the corresponding supporting structures. Alternating the pressurized air can drive the motor to rotate each step in 3.6° with the motor coupled to a planetary gearbox. Experimental studies were conducted to validate its dynamics performance. Maximum 800mNm output torque can be achieved. The motor accuracy independently varied by two factors: motor operating speed and step size, was also investigated. The motor was tested within a Siemens 3T MRI scanner. The image artifact and the signal-to-noise ratio (SNR) were evaluated in order to study its MRI compliancy. The results show that the presented pneumatic stepper motor generated 2.35% SNR reduction in MR images and no observable artifact was presented besides the motor body itself. The proposed motor test also demonstrates a standard to evaluate the motor capability for later incorporation with motorized devices used in robot-assisted surgery under MRI. PMID:24957635

The Safety of Cardiac and Thoracic Magnetic Resonance Imaging in Patients with Cardiac Implantable Electronic Devices.

PubMed

Dandamudi, Sanjay; Collins, Jeremy D; Carr, James C; Mongkolwat, Pat; Rahsepar, Amir A; Tomson, Todd T; Verma, Nishant; Arora, Rishi; Chicos, Alex B; Kim, Susan S; Lin, Albert C; Passman, Rod S; Knight, Bradley P

2016-12-01

Studies reporting the safety of magnetic resonance imaging (MRI) in patients with a cardiac implantable electronic device (CIED) have mostly excluded examinations with the device in the magnet isocenter. The purpose of this study was to describe the safety of cardiac and thoracic spine MRI in patients with a CIED. The medical records of patients with a CIED who underwent a cardiac or thoracic spine MRI between January 2011 and December 2014 were reviewed. Devices were interrogated before and after imaging with reprogramming to asynchronous pacing in pacemaker-dependent patients. The clinical interpretability of the MRI and peak and average specific absorption rates (SARs, W/kg) achieved were determined. Fifty-eight patients underwent 51 cardiac and 11 thoracic spine MRI exams. Twenty-nine patients had a pacemaker and 29 had an implantable cardioverter defibrillator. Seventeen percent (n = 10) were pacemaker dependent. Fifty-one patients (89%) had non-MRI-conditional devices. There were no clinically significant changes in atrial and ventricular sensing, impedance, and threshold measurements. There were no episodes of device mode changes, arrhythmias, therapies delivered, electrical reset, or battery depletion. One study was prematurely discontinued due to a patient complaint of chest pain of which the etiology was not determined. Across all examinations, the average peak SAR was 2.0 ± 0.85 W/kg with an average SAR of 0.35 ± 0.37 W/kg. Artifact significantly limiting the clinical interpretation of the study was present in 33% of cardiac MRI studies. When a comprehensive CIED magnetic resonance safety protocol is followed, the risk of performing 1.5-T magnetic resonance studies with the device in the magnet isocenter, including in patients who are pacemaker dependent, is low. Copyright © 2016. Published by Elsevier Inc.

Novel magnetomechanical MR compatible vibrational device for producing kinesthetic illusion during fMRI.

PubMed

Carr, Sarah J; Borreggine, Kristin; Heilman, Jeremiah; Griswold, Mark; Walter, Benjamin L

2013-11-01

Functional MRI (fMRI) can provide insights into the functioning of the sensorimotor system, which is of particular interest in studying people with movement disorders or chronic pain conditions. This creates a demand for manipulanda that can fit and operate within the environment of a MRI scanner. Here, the authors present a magnetomechanical device that delivers a vibrotactile sensation to the skin with a force of approximately 9 N. MRI compatibility of the device was tested in a 3 T scanner using a phantom to simulate the head. Preliminary investigation into the effectiveness of the device at producing cortical and subcortical activity was also conducted with a group of seven healthy subjects. The vibration was applied to the right extensor carpi ulnaris tendon to induce a kinesthetic illusion of flexion and extension of the wrist. The MRI compatibility tests showed the device did not produce image artifacts and the generated electromagnetic field did not disrupt the static magnetic field of the scanner or its operation. The subject group results showed activity in the contralateral putamen, premotor cortex, and dorsal lateral prefrontal cortex. Ipsilaterally, there was increased activity in the superior and inferior parietal lobules. Areas that activated bilaterally included the thalamus, anterior cingulate, secondary somatosensory areas (S2), temporal lobes, and visual association areas. This device offers an effective tool with precise control over the vibratory stimulus, delivering higher forces than some other types of devices (e.g., piezoelectric actuators). It can be useful for investigating sensory systems and sensorimotor integration.

Assessing access to MRI of patients with magnetic resonance-conditional pacemaker and implantable cardioverter defibrillator systems: the Really ProMRI study design.

PubMed

Maglia, Giampiero; Curnis, Antonio; Brieda, Marco; Anaclerio, Matteo; Caccavo, Vincenzo; Bonfanti, Paolo; Melissano, Donato; Caravati, Fabrizio; Giovene, Lisa; Gargaro, Alessio

2015-10-01

Despite the fact that magnetic resonance (MR)-conditional pacemaker and lead systems have been introduced more than 5 years ago, it is still not clear whether they have actually facilitated the access of pacemaker patients to this important diagnostic tool. Factors limiting MR scans in daily practice in patients with MR-conditional cardiac implantable electronic device (CIED) systems may be related to organizational, cultural and sometimes legal aspects. The Really ProMRI registry is an ongoing survey designed to assess the annual rate of MR examinations in patients with MR-conditional implants, with either pacemakers or implantable cardioverter defibrillators, and to detect the main factors limiting MRI. The primary endpoint of the Really ProMRI registry is to assess the current access to MRI of patients with MR-conditional pacemaker or implantable cardioverter defibrillator systems during normal practice. Data in the literature reported a 17% annual incidence of medical conditions requiring MRI in CIED patients. The Really ProMRI registry has been designed to detect 4.5% absolute difference with an 80% statistical power, by recruiting 600 patients already implanted with MR-conditional CIED implant. Patients will be followed up for 1 year, during which they will be asked to refer any prescription, execution or denial of an MR examination by patient questionnaires and original source documents. The ongoing Really ProMRI registry will assess the actual rate of and factors limiting the access to MRI for patients with MR-conditional CIEDs.

Assessment of Safety and Interference Issues of Radio Frequency Identification Devices in 0.3 Tesla Magnetic Resonance Imaging and Computed Tomography

PubMed Central

Periyasamy, M.; Dhanasekaran, R.

2014-01-01

The objective of this study was to evaluate two issues regarding magnetic resonance imaging (MRI) including device functionality and image artifacts for the presence of radio frequency identification devices (RFID) in association with 0.3 Tesla at 12.7 MHz MRI and computed tomography (CT) scanning. Fifteen samples of RFID tags with two different sizes (wristband and ID card types) were tested. The tags were exposed to several MR-imaging conditions during MRI examination and X-rays of CT scan. Throughout the test, the tags were oriented in three different directions (axial, coronal, and sagittal) relative to MRI system in order to cover all possible situations with respect to the patient undergoing MRI and CT scanning, wearing a RFID tag on wrist. We observed that the tags did not sustain physical damage with their functionality remaining unaffected even after MRI and CT scanning, and there was no alternation in previously stored data as well. In addition, no evidence of either signal loss or artifact was seen in the acquired MR and CT images. Therefore, we can conclude that the use of this passive RFID tag is safe for a patient undergoing MRI at 0.3 T/12.7 MHz and CT Scanning. PMID:24701187

Evaluation of MRI issues for an access port with a radiofrequency identification (RFID) tag.

PubMed

Titterington, Blake; Shellock, Frank G

2013-10-01

A medical implant that contains metal, such as an RFID tag, must undergo proper MRI testing to ensure patient safety and to determine that the function of the RFID tag is not compromised by exposure to MRI conditions. Therefore, the objective of this investigation was to assess MRI issues for a new access port that incorporates an RFID tag. Samples of the access port with an RFID tag (Medcomp Power Injectable Port with CertainID; Medcomp, Harleysville, PA) were evaluated using standard protocols to assess magnetic field interactions (translational attraction and torque; 3-T), MRI-related heating (3-T), artifacts (3-T), and functional changes associated with different MRI conditions (nine samples, exposed to different MRI conditions at 1.5-T and 3-T). Magnetic field interactions were not substantial and will pose no hazards to patients. MRI-related heating was minimal (highest temperature change, 1.7°C; background temperature rise, 1.6°C). Artifacts were moderate in size in relation to the device. Exposures to MRI conditions at 1.5-T and 3-T did not alter or damage the functional aspects of the RFID tag. Based on the findings of the test, this new access port with an RFID tag is acceptable (or, MR conditional, using current MRI labeling terminology) for patients undergoing MRI examinations at 1.5-T/64-MHz and 3-T/128-MHz. Copyright © 2013 Elsevier Inc. All rights reserved.

Fast Room Temperature Very Low Field-Magnetic Resonance Imaging System Compatible with MagnetoEncephaloGraphy Environment

PubMed Central

Galante, Angelo; Sinibaldi, Raffaele; Conti, Allegra; De Luca, Cinzia; Catallo, Nadia; Sebastiani, Piero; Pizzella, Vittorio; Romani, Gian Luca; Sotgiu, Antonello; Della Penna, Stefania

2015-01-01

In recent years, ultra-low field (ULF)-MRI is being given more and more attention, due to the possibility of integrating ULF-MRI and Magnetoencephalography (MEG) in the same device. Despite the signal-to-noise ratio (SNR) reduction, there are several advantages to operating at ULF, including increased tissue contrast, reduced cost and weight of the scanners, the potential to image patients that are not compatible with clinical scanners, and the opportunity to integrate different imaging modalities. The majority of ULF-MRI systems are based, until now, on magnetic field pulsed techniques for increasing SNR, using SQUID based detectors with Larmor frequencies in the kHz range. Although promising results were recently obtained with such systems, it is an open question whether similar SNR and reduced acquisition time can be achieved with simpler devices. In this work a room-temperature, MEG-compatible very-low field (VLF)-MRI device working in the range of several hundred kHz without sample pre-polarization is presented. This preserves many advantages of ULF-MRI, but for equivalent imaging conditions and SNR we achieve reduced imaging time based on preliminary results using phantoms and ex-vivo rabbits heads. PMID:26630172

Mutual interferences and design principles for mechatronic devices in magnetic resonance imaging.

PubMed

Yu, Ningbo; Gassert, Roger; Riener, Robert

2011-07-01

Robotic and mechatronic devices that work compatibly with magnetic resonance imaging (MRI) are applied in diagnostic MRI, image-guided surgery, neurorehabilitation and neuroscience. MRI-compatible mechatronic systems must address the challenges imposed by the scanner's electromagnetic fields. We have developed objective quantitative evaluation criteria for device characteristics needed to formulate design guidelines that ensure MRI-compatibility based on safety, device functionality and image quality. The mutual interferences between an MRI system and mechatronic devices working in its vicinity are modeled and tested. For each interference, the involved components are listed, and a numerical measure for "MRI-compatibility" is proposed. These interferences are categorized into an MRI-compatibility matrix, with each element representing possible interactions between one part of the mechatronic system and one component of the electromagnetic fields. Based on this formulation, design principles for MRI-compatible mechatronic systems are proposed. Furthermore, test methods are developed to examine whether a mechatronic device indeed works without interferences within an MRI system. Finally, the proposed MRI-compatibility criteria and design guidelines have been applied to an actual design process that has been validated by the test procedures. Objective and quantitative MRI-compatibility measures for mechatronic and robotic devices have been established. Applying the proposed design principles, potential problems in safety, device functionality and image quality can be considered in the design phase to ensure that the mechatronic system will fulfill the MRI-compatibility criteria. New guidelines and test procedures for MRI instrument compatibility provide a rational basis for design and evaluation of mechatronic devices in various MRI applications. Designers can apply these criteria and use the tests, so that MRI-compatibility results can accrue to build an experiential database.

Wireless Mobile Technology to Improve Workflow and Feasibility of MR-Guided Percutaneous Interventions

PubMed Central

Rube, Martin A.; Holbrook, Andrew B.; Cox, Benjamin F.; Buciuc, Razvan; Melzer, Andreas

2015-01-01

Purpose A wireless interactive display and control device combined with a platform-independent web-based User Interface (UI) was developed to improve the workflow for interventional Magnetic Resonance Imaging (iMRI). Methods The iMRI-UI enables image acquisition of up to three independent slices using various pulse sequences with different contrast weighting. Pulse sequence, scan geometry and related parameters can be changed on the fly via the iMRI-UI using a tablet computer for improved lesion detection and interventional device targeting. The iMRI-UI was validated for core biopsies with a liver phantom (n=40) and Thiel soft-embalmed human cadavers (n=24) in a clinical 1.5T MRI scanner. Results The iMRI-UI components and setup were tested and found conditionally MRI-safe to use according to current ASTM standards. Despite minor temporary touchscreen interference at a close distance to the bore (<20 cm), no other issues regarding quality or imaging artefacts were observed. The 3D root-mean-square distance error was 2.8±1.0 (phantom) / 2.9±0.8 mm (cadaver) and overall procedure times ranged between 12–22 (phantom) / 20–55 minutes (cadaver). Conclusions The wireless iMRI-UI control setup enabled fast and accurate interventional biopsy needle placements along complex trajectories and improved the workflow for percutaneous interventions under MRI guidance in a preclinical trial. PMID:25179151

Low Field Squid MRI Devices, Components and Methods

NASA Technical Reports Server (NTRS)

Hahn, Inseob (Inventor); Penanen, Konstantin I. (Inventor); Eom, Byeong H. (Inventor)

2013-01-01

Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.

Low Field Squid MRI Devices, Components and Methods

NASA Technical Reports Server (NTRS)

Penanen, Konstantin I. (Inventor); Eom, Byeong H. (Inventor); Hahn, Inseob (Inventor)

2014-01-01

Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.

Low field SQUID MRI devices, components and methods

NASA Technical Reports Server (NTRS)

Penanen, Konstantin I. (Inventor); Eom, Byeong H. (Inventor); Hahn, Inseob (Inventor)

2011-01-01

Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.

Low field SQUID MRI devices, components and methods

NASA Technical Reports Server (NTRS)

Penanen, Konstantin I. (Inventor); Eom, Byeong H (Inventor); Hahn, Inseob (Inventor)

2010-01-01

Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.

A stereotactic method for image-guided transcranial magnetic stimulation validated with fMRI and motor-evoked potentials.

PubMed

Neggers, S F W; Langerak, T R; Schutter, D J L G; Mandl, R C W; Ramsey, N F; Lemmens, P J J; Postma, A

2004-04-01

Transcranial Magnetic Stimulation (TMS) delivers short magnetic pulses that penetrate the skull unattenuated, disrupting neural processing in a noninvasive, reversible way. To disrupt specific neural processes, coil placement over the proper site is critical. Therefore, a neural navigator (NeNa) was developed. NeNa is a frameless stereotactic device using structural and functional magnetic resonance imaging (fMRI) data to guide TMS coil placement. To coregister the participant's head to his MRI, 3D cursors are moved to anatomical landmarks on a skin rendering of the participants MRI on a screen, and measured at the head with a position measurement device. A method is proposed to calculate a rigid body transformation that can coregister both sets of coordinates under realistic noise conditions. After coregistration, NeNa visualizes in real time where the device is located with respect to the head, brain structures, and activated areas, enabling precise placement of the TMS coil over a predefined target region. NeNa was validated by stimulating 5 x 5 positions around the 'motor hotspot' (thumb movement area), which was marked on the scalp guided by individual fMRI data, while recording motor-evoked potentials (MEPs) from the abductor pollicis brevis (APB). The distance between the center of gravity (CoG) of MEP responses and the location marked on the scalp overlying maximum fMRI activation was on average less then 5 mm. The present results demonstrate that NeNa is a reliable method for image-guided TMS coil placement.

Performing magnetic resonance imaging in patients with implantable pacemakers and defibrillators: results of a European Heart Rhythm Association survey.

PubMed

Marinskis, Germanas; Bongiorni, Maria Grazia; Dagres, Nikolaos; Dobreanu, Dan; Lewalter, Thorsten; Blomström-Lundqvist, Carina

2012-12-01

The purpose of our survey was to evaluate the experience, current practice and attitudes of performing magnetic resonance imaging (MRI) studies in patients with cardiac implantable electronic devices. Fifty-one centre-members of European Heart Rhythm Association Research network have responded to the survey. According to the obtained data, 55.2% of responding centres do not perform MRI scans in patients with non-MRI-certified pacemakers and 65.8% in patients with such implantable cardioverter defibrillators (ICDs). Reported complication rate in patients with non-MRI-certified devices is low and conforms to the literature data. Experience with newer MRI-compatible pacemakers and ICDs is limited to single cases in most centres. This survey shows limited experience with performing MRI studies in patients with implanted pacemakers and ICDs. In concordance with available guidelines, most centres limit MRI scans in patients with non-MRI-certified devices. The implant numbers for MRI-certified devices and experience with performing MRI scans in these patients are still low.

[Microinjection Monitoring System Design Applied to MRI Scanning].

PubMed

Xu, Yongfeng

2017-09-30

A microinjection monitoring system applied to the MRI scanning was introduced. The micro camera probe was used to stretch into the main magnet for real-time video injection monitoring of injection tube terminal. The programming based on LabVIEW was created to analysis and process the real-time video information. The feedback signal was used for intelligent controlling of the modified injection pump. The real-time monitoring system can make the best use of injection under the condition that the injection device was away from the sample which inside the magnetic room and unvisible. 9.4 T MRI scanning experiment showed that the system in ultra-high field can work stability and doesn't affect the MRI scans.

A new vibrator to stimulate muscle proprioceptors in fMRI.

PubMed

Montant, Marie; Romaiguère, Patricia; Roll, Jean-Pierre

2009-03-01

Studying cognitive brain functions by functional magnetic resonance imaging (fMRI) requires appropriate stimulation devices that do not interfere with the magnetic fields. Since the emergence of fMRI in the 90s, a number of stimulation devices have been developed for the visual and auditory modalities. Only few devices, however, have been developed for the somesthesic modality. Here, we present a vibration device for studying somesthesia that is compatible with high magnetic field environments and that can be used in fMRI machines. This device consists of a poly vinyl chloride (PVC) vibrator containing a wind turbine and of a pneumatic apparatus that controls 1-6 vibrators simultaneously. Just like classical electromagnetic vibrators, our device stimulates muscle mechanoreceptors (muscle spindles) and generates reliable illusions of movement. We provide the fMRI compatibility data (phantom test), the calibration curve (vibration frequency as a function of air flow), as well as the results of a kinesthetic test (perceived speed of the illusory movement as a function of vibration frequency). This device was used successfully in several brain imaging studies using both fMRI and magnetoencephalography.

Magnetic Resonance Imaging With Cochlear Implant Magnet in Place: Safety and Imaging Quality.

PubMed

Carlson, Matthew L; Neff, Brian A; Link, Michael J; Lane, John I; Watson, Robert E; McGee, Kiaran P; Bernstein, Matt A; Driscoll, Colin L W

2015-07-01

To evaluate the safety and image quality of 1.5-T MRI in patients with cochlear implants and retained internal magnets. Retrospective case series from 2012 to 2014. Single tertiary academic referral center. All cochlear implant recipients undergoing 1.5-T MRI without internal magnet removal. MRI after tight headwrap application. Patient tolerance, complications, and characteristics of imaging artifact. Nineteen ears underwent a total of 34 MRI scans. Two patients did not tolerate imaging with the headwrap in place and required magnet removal before rescanning. One subject experienced two separate episodes of polarity reversal in the same device from physical realignment (i.e., flipping) of the internal magnet requiring surgical repositioning. Three patients were discovered to have canting of the internal magnet after imaging. In all three cases, the magnet could be reseated by applying gentle firm pressure to the scalp until the magnet "popped" back into place. These patients continue to use their device without difficulty and have not required surgical replacement. In patients receiving head MRI, the ipsilateral internal auditory canal and cerebellopontine angle could be visualized without difficulty in 94% of cases. There were no episodes of cochlear implant device failure or soft tissue complications. Under controlled conditions, 1.5-T MRI can be successfully performed in most patients without the need for cochlear implant magnet removal. In nearly all cases, imaging artifact does not impede evaluation of the ipsilateral skull base. Patients should be counseled regarding the risk of internal magnet movement that may occur in up to 15% of cases, even with tight headwrap application. If internal magnet polarity reversal occurs, a trial of reversing the external magnet can be considered. If canting or mild displacement of the internal magnet occurs, an attempt at reseating can be made by applying gentle firm pressure to the scalp over the internal magnet. If conservative measures fail, the magnet should be surgically repositioned to minimize interruption of device use and to prevent scalp complications.

Ensuring safety of implanted devices under MRI using reversed RF polarization.

PubMed

Overall, William R; Pauly, John M; Stang, Pascal P; Scott, Greig C

2010-09-01

Patients with long-wire medical implants are currently prevented from undergoing magnetic resonance imaging (MRI) scans due to the risk of radio frequency (RF) heating. We have developed a simple technique for determining the heating potential for these implants using reversed radio frequency (RF) polarization. This technique could be used on a patient-to-patient basis as a part of the standard prescan procedure to ensure that the subject's device does not pose a heating risk. By using reversed quadrature polarization, the MR scan can be sensitized exclusively to the potentially dangerous currents in the device. Here, we derive the physical principles governing the technique and explore the primary sources of inaccuracy. These principles are verified through finite-difference simulations and through phantom scans of implant leads. These studies demonstrate the potential of the technique for sensitively detecting potentially dangerous coupling conditions before they can do any harm. 2010 Wiley-Liss, Inc.

Numerical investigations of MRI RF field induced heating for external fixation devices

PubMed Central

2013-01-01

Background The magnetic resonance imaging (MRI) radio frequency (RF) field induced heating on external fixation devices can be very high in the vicinity of device screws. Such induced RF heating is related to device constructs, device placements, as well as the device insertion depth into human subjects. In this study, computational modeling is performed to determine factors associated with such induced heating. Methods Numerical modeling, based on the finite-difference time-domain (FDTD) method, is used to evaluate the temperature rises near external device screw tips inside the ASTM phantom for both 1.5-T and 3-T MRI systems. The modeling approach consists of 1) the development of RF coils for 1.5-T and 3-T, 2) the electromagnetic simulations of energy deposition near the screw tips of external fixation devices, and 3) the thermal simulations of temperature rises near the tips of these devices. Results It is found that changing insertion depth and screw spacing could largely affect the heating of these devices. In 1.5-T MRI system, smaller insertion depth and larger pin spacing will lead to higher temperature rise. However, for 3-T MRI system, the relation is not very clear when insertion depth is larger than 5 cm or when pin spacing became larger than 20 cm. The effect of connection bar material on device heating is also studied and the heating mechanism of the device is analysed. Conclusions Numerical simulation is used to study RF heating for external fixation devices in both 1.5-T and 3-T MRI coils. Typically, shallower insertion depth and larger pin spacing with conductive bar lead to higher RF heating. The heating mechanism is explained using induced current along the device and power decay inside ASTM phantom. PMID:23394173

Design and Application of a New Automated Fluidic Visceral Stimulation Device for Human fMRI Studies of Interoception

PubMed Central

Gassert, Roger; Wanek, Johann; Michels, Lars; Mehnert, Ulrich; Kollias, Spyros S.

2016-01-01

Mapping the brain centers that mediate the sensory-perceptual processing of visceral afferent signals arising from the body (i.e., interoception) is useful both for characterizing normal brain activity and for understanding clinical disorders related to abnormal processing of visceral sensation. Here, we report a novel closed-system, electrohydrostatically driven master–slave device that was designed and constructed for delivering controlled fluidic stimulations of visceral organs and inner cavities of the human body within the confines of a 3T magnetic resonance imaging (MRI) scanner. The design concept and performance of the device in the MRI environment are described. In addition, the device was applied during a functional MRI (fMRI) investigation of visceral stimulation related to detrusor distention in two representative subjects to verify its feasibility in humans. System evaluation tests demonstrate that the device is MR-compatible with negligible impact on imaging quality [static signal-to-noise ratio (SNR) loss <2.5% and temporal SNR loss <3.5%], and has an accuracy of 99.68% for flow rate and 99.27% for volume delivery. A precise synchronization of the stimulus delivery with fMRI slice acquisition was achieved by programming the proposed device to detect the 5 V transistor–transistor logic (TTL) trigger signals generated by the MRI scanner. The fMRI data analysis using the general linear model analysis with the standard hemodynamic response function showed increased activations in the network of brain regions that included the insula, anterior and mid-cingulate and lateral prefrontal cortices, and thalamus in response to increased distension pressure on viscera. The translation from manually operated devices to an MR-compatible and MR-synchronized device under automatic control represents a useful innovation for clinical neuroimaging studies of human interoception. PMID:27551646

Voltage-based device tracking in a 1.5 Tesla MRI during imaging: initial validation in swine models.

PubMed

Schmidt, Ehud J; Tse, Zion T H; Reichlin, Tobias R; Michaud, Gregory F; Watkins, Ronald D; Butts-Pauly, Kim; Kwong, Raymond Y; Stevenson, William; Schweitzer, Jeffrey; Byrd, Israel; Dumoulin, Charles L

2014-03-01

Voltage-based device-tracking (VDT) systems are commonly used for tracking invasive devices in electrophysiological cardiac-arrhythmia therapy. During electrophysiological procedures, electro-anatomic mapping workstations provide guidance by integrating VDT location and intracardiac electrocardiogram information with X-ray, computerized tomography, ultrasound, and MR images. MR assists navigation, mapping, and radiofrequency ablation. Multimodality interventions require multiple patient transfers between an MRI and the X-ray/ultrasound electrophysiological suite, increasing the likelihood of patient-motion and image misregistration. An MRI-compatible VDT system may increase efficiency, as there is currently no single method to track devices both inside and outside the MRI scanner. An MRI-compatible VDT system was constructed by modifying a commercial system. Hardware was added to reduce MRI gradient-ramp and radiofrequency unblanking pulse interference. VDT patches and cables were modified to reduce heating. Five swine cardiac VDT electro-anatomic mapping interventions were performed, navigating inside and thereafter outside the MRI. Three-catheter VDT interventions were performed at >12 frames per second both inside and outside the MRI scanner with <3 mm error. Catheters were followed on VDT- and MRI-derived maps. Simultaneous VDT and imaging was possible in repetition time >32 ms sequences with <0.5 mm errors, and <5% MRI signal-to-noise ratio (SNR) loss. At shorter repetition times, only intracardiac electrocardiogram was reliable. Radiofrequency heating was <1.5°C. An MRI-compatible VDT system is feasible. Copyright © 2013 Wiley Periodicals, Inc.

Voltage-based Device Tracking in a 1.5 Tesla MRI during Imaging: Initial validation in swine models

PubMed Central

Schmidt, Ehud J; Tse, Zion TH; Reichlin, Tobias R; Michaud, Gregory F; Watkins, Ronald D; Butts-Pauly, Kim; Kwong, Raymond Y; Stevenson, William; Schweitzer, Jeffrey; Byrd, Israel; Dumoulin, Charles L

2013-01-01

Purpose Voltage-based device-tracking (VDT) systems are commonly used for tracking invasive devices in electrophysiological (EP) cardiac-arrhythmia therapy. During EP procedures, electro-anatomic-mapping (EAM) workstations provide guidance by integrating VDT location and intra-cardiac-ECG information with X-ray, CT, Ultrasound, and MR images. MR assists navigation, mapping and radio-frequency-ablation. Multi-modality interventions require multiple patient transfers between an MRI and the X-ray/ultrasound EP suite, increasing the likelihood of patient-motion and image mis-registration. An MRI-compatible VDT system may increase efficiency, since there is currently no single method to track devices both inside and outside the MRI scanner. Methods An MRI-compatible VDT system was constructed by modifying a commercial system. Hardware was added to reduce MRI gradient-ramp and radio-frequency-unblanking-pulse interference. VDT patches and cables were modified to reduce heating. Five swine cardiac VDT EAM-mapping interventions were performed, navigating inside and thereafter outside the MRI. Results Three-catheter VDT interventions were performed at >12 frames-per-second both inside and outside the MRI scanner with <3mm error. Catheters were followed on VDT- and MRI-derived maps. Simultaneous VDT and imaging was possible in repetition-time (TR) >32 msec sequences with <0.5mm errors, and <5% MRI SNR loss. At shorter TRs, only intra-cardiac-ECG was reliable. RF Heating was <1.5C°. Conclusion An MRI-compatible VDT system is feasible. PMID:23580479

Real-Time MRI-Guided Endovascular Recanalization of Chronic Total Arterial Occlusion in a Swine Model

PubMed Central

Raval, Amish N.; Karmarkar, Parag V.; Guttman, Michael A.; Ozturk, Cengizhan; Sampath, Smita; DeSilva, Ranil; Aviles, Ronnier J.; Xu, Minnan; Wright, Victor J.; Schenke, William H.; Kocaturk, Ozgur; Dick, Alexander J.; Raman, Venkatesh K.; Atalar, Ergin; McVeigh, Elliot R.; Lederman, Robert J.

2006-01-01

Background Endovascular recanalization (guidewire traversal) of peripheral artery chronic total occlusion (CTO) can be challenging. X-Ray angiography resolves CTO poorly. Virtually “blind” device advancement during X-ray-guided interventions can lead to procedure failure, perforation and hemorrhage. Alternatively, magnetic resonance imaging (MRI) may delineate the artery within the occluded segment to enhance procedural safety and success. We hypothesized that real-time MRI (rtMRI) guided CTO recanalization can be accomplished in an animal model. Methods and Results Carotid artery CTO was created by balloon injury in 19 lipid overfed swine. After 6–8 weeks, two underwent direct necropsy analysis for histology, three underwent primary X-ray-guided CTO recanalization attempts, and the remaining 14 underwent rtMRI-guided recanalization attempts in a 1.5T interventional MRI system. rtMRI intervention used custom CTO catheters and guidewires that incorporated MRI receiver antennae to enhance device visibility. The mean length of the occluded segments was 13.3 ± 1.6cm. rtMRI-guided CTO recanalization was successful in 11/14 swine and only 1/3 swine using X-ray alone. After unsuccessful rtMRI (n = 3), X-ray-guided attempts also were all unsuccessful. Conclusions Recanalization of long CTO is feasible entirely using rtMRI guidance. Low profile clinical-grade devices will be required to translate this experience to humans. Endovascular recanalization of chronic total arterial occlusion (CTO) is challenging under conventional X-ray guidance because devices are advanced almost blindly. MRI can image CTO borders and luminal contents, and could potentially guide these procedures. We test the feasibility of real-time MRI guided wire traversal in a swine model of peripheral artery CTO using custom active MRI catheters. PMID:16490819

Towards Optical Coherence Tomography-based elastographic evaluation of human cartilage.

PubMed

Nebelung, Sven; Brill, Nicolai; Müller, Felix; Tingart, Markus; Pufe, Thomas; Merhof, Dorit; Schmitt, Robert; Jahr, Holger; Truhn, Daniel

2016-03-01

Optical Coherence Tomography (OCT) is an imaging technique that allows the surface and subsurface evaluation of semitransparent tissues by generating microscopic cross-sectional images in real time, to millimetre depths and at micrometre resolutions. As the differentiation of cartilage degeneration remains diagnostically challenging to standard imaging modalities, an OCT- and MRI-compatible indentation device for the assessment of cartilage functional properties was developed and validated in the present study. After describing the system design and performing its comprehensive validation, macroscopically intact human cartilage samples (n=5) were indented under control of displacement (δ1=202µm; δ2=405µm; δ3=607µm; δ4=810µm) and simultaneous OCT imaging through a transparent indenter piston in direct contact with the sample; thus, 3-D OCT datasets from surface and subsurface areas were obtained. OCT-based evaluation of loading-induced changes included qualitative assessment of image morphology and signal characteristics. For inter-method cross referencing, the device׳s compatibility with MRI as well as qualitative morphology changes under analogous indentation loading conditions were evaluated by a series of T2 weighted gradient echo sequences. Cartilage thickness measurements were performed using the needle-probe technique prior to OCT and MRI imaging, and subsequently referenced to sample thickness as determined by MRI and histology. Dynamic indentation testing was performed to determine Young׳s modulus for biomechanical reference purposes. Distinct differences in sample thickness as well as corresponding strains were found; however, no significant differences in cartilage thickness were found between the used techniques. Qualitative assessment of OCT and MRI images revealed either distinct or absent sample-specific patterns of morphological changes in relation to indentation loading. For OCT, the tissue area underneath the indenter piston could be qualitatively assessed and displayed in multiple reconstructions, while for MRI, T2 signal characteristics indicated the presence of water and related tissue pressurisation within the sample. In conclusion, the present indentation device has been developed, constructed and validated for qualitative assessment of human cartilage and its response to loading by OCT and MRI. Thereby, it may provide the basis for future quantitative approaches that measure loading-induced deformations within the tissue to generate maps of local tissue properties as well as investigate their relation to degeneration. Copyright © 2015 Elsevier Ltd. All rights reserved.

3 Tesla MRI of patients with a vagus nerve stimulator: initial experience using a T/R head coil under controlled conditions.

PubMed

Gorny, Krzysztof R; Bernstein, Matt A; Watson, Robert E

2010-02-01

To assess safety of clinical MRI of the head in patients with implanted model 100, 102, and 103 vagus nerve stimulation (VNS) Therapy Systems (Cyberonics, Inc., Houston, TX) in 3.0 Tesla MRI (GE Healthcare, Milwaukee, WI). The distributions of the radiofrequency B(1) (+)-field produced by the clinically used transmit/receive (T/R) head coil (Advanced Imaging Research Incorporated, Cleveland, OH) and body coil were measured in a head and shoulders phantom. These measurements were supplemented by temperature measurements on the lead tips and the implantable pulse generator (IPG) of the VNS devices in a head and torso phantom with the same two coils. Clinical 3T MRI head scans were then acquired under highly controlled conditions in a series of 17 patients implanted with VNS. Phantom studies showed only weak B(1) (+) fields at the location of the VNS IPG and leads for MRI scans using the T/R head coil. The MRI-related heating on a VNS scanned in vitro at 3T was also found to be minimal (0.4-0.8 degrees C at the leads, negligible at the IPG). The patient MRI examinations were completed successfully without any adverse incidents. No patient reported any heating, discomfort, or any other unusual sensation. Safe clinical MRI head scanning of patients with implanted VNS is shown to be feasible on a GE Signa Excite 3T MRI system using one specific T/R head coil. These results apply to this particular MRI system configuration. Extrapolation or generalization of these results to more general or less controlled imaging situations without supporting data of safety is highly discouraged.

ACTIVE DELIVERY CABLE TUNED TO DEVICE DEPLOYMENT STATE: ENHANCED VISIBILITY OF NITINOL OCCLUDERS DURING PRE-CLINICAL INTERVENTIONAL MRI

PubMed Central

Bell, Jamie A.; Saikus, Christina E.; Ratnayaka, Kanishka; Barbash, Israel M.; Faranesh, Anthony Z.; Franson, Dominique N.; Sonmez, Merdim; Slack, Michael C.; Lederman, Robert J.; Kocaturk, Ozgur

2012-01-01

Purpose To develop an active delivery system that enhances visualization of nitinol cardiac occluder devices during deployment under real-time MRI. Materials and Methods We constructed an active delivery cable incorporating a loopless antenna and a custom titanium microscrew to secure the occluder devices. The delivery cable was tuned and matched to 50Ω at 64 MHz with the occluder device attached. We used real-time balanced SSFP in a wide-bore 1.5T scanner. Device-related images were reconstructed separately and combined with surface-coil images. The delivery cable was tested in vitro in a phantom and in vivo in swine using a variety of nitinol cardiac occluder devices. Results In vitro, the active delivery cable provided little signal when the occluder device was detached and maximal signal with the device attached. In vivo, signal from the active delivery cable enabled clear visualization of occluder device during positioning and deployment. Device release resulted in decreased signal from the active cable. Post-mortem examination confirmed proper device placement. Conclusions The active delivery cable enhanced the MRI depiction of nitinol cardiac occluder devices during positioning and deployment, both in conventional and novel applications. We expect enhanced visibility to contribute to effectiveness and safety of new and emerging MRI-guided treatments. PMID:22707441

Measurement, time-stamping, and analysis of electrodermal activity in fMRI

NASA Astrophysics Data System (ADS)

Smyser, Christopher; Grabowski, Thomas J.; Rainville, Pierre; Bechara, Antione; Razavi, Mehrdad; Mehta, Sonya; Eaton, Brent L.; Bolinger, Lizann

2002-04-01

A low cost fMRI-compatible system was developed for detecting electrodermal activity without inducing image artifact. Subject electrodermal activity was measured on the plantar surface of the foot using a standard recording circuit. Filtered analog skin conductance responses (SCR) were recorded with a general purpose, time-stamping data acquisition system. A conditioning paradigm involving painful thermal stimulation was used to demonstrate SCR detection and investigate neural correlates of conditioned autonomic activity. 128x128 pixel EPI-BOLD images were acquired with a GE 1.5T Signa scanner. Image analysis was performed using voxel-wise multiple linear regression. The covariate of interest was generated by convolving stimulus event onset with a standard hemodynamic response function. The function was time-shifted to determine optimal activation. Significance was tested using the t-statistic. Image quality was unaffected by the device, and conditioned and unconditioned SCRs were successfully detected. Conditioned SCRs correlated significantly with activity in the right anterior insular cortex. The effect was more robust when responses were scaled by SCR amplitude. The ability to measure and time register SCRs during fMRI acquisition enables studies of cognitive processes marked by autonomic activity, including those involving decision-making, pain, emotion, and addiction.

Reversing the polarity of a cochlear implant magnet after magnetic resonance imaging.

PubMed

Jeon, Ju Hyun; Bae, Mi Ran; Chang, Jae Won; Choi, Jae Young

2012-08-01

The number of patients with cochlear implant (CI) has been rapidly increasing in recent years, and these patients show a growing need of examination by magnetic resonance imaging (MRI). However, the use of MRI on patients with CI is restricted by the internal magnet of the CI. Many studies have investigated the safety of performing 1.5T MRI on patients with CI, which is now being practiced in a clinical setting. We experienced a case in which the polarity of the cochlear implant magnet was reversed after the patient was examined using 1.5T MRI. The external device was attached to the internal device oppositely. We could not find displacement of the internal device, magnet, or electrode upon radiological evaluation. We came up with two possible mechanisms by which the polarity of the magnet reversed. The first possibility was that the magnetic field of MRI reversed the polarity of the magnet. The second was that the internal magnet was physically realigned while interacting with the MRI. We believe the second hypothesis to be more reliable. A removable magnet and a loose magnet boundary of a CI device may have allowed for physical reorientation of the internal magnet. Therefore, in order to avoid these complications, first, the internal magnet must not be aligned anti-parallel with the magnetic polarity of MRI. In the Siemens MRI, the vector of the magnetic field is downward, so implant site should be placed in facing upwards to minimize demagnetization. In the GE Medical Systems MRI, the vector of the magnetic field is upward, so the implant site should be placed facing downwards. Second, wearing of a commercial mold which is fixed to the internal device before performing MRI can be helpful. In addition, any removable internal magnets in a CI device should be removed before MRI, especially in the trunk. However, to ultimately solve this problem, the pocket of the internal magnet should be redesigned for safety. Copyright © 2011. Published by Elsevier Ireland Ltd.

Motion compensation for MRI-compatible patient-mounted needle guide device: estimation of targeting accuracy in MRI-guided kidney cryoablations

NASA Astrophysics Data System (ADS)

Tokuda, Junichi; Chauvin, Laurent; Ninni, Brian; Kato, Takahisa; King, Franklin; Tuncali, Kemal; Hata, Nobuhiko

2018-04-01

Patient-mounted needle guide devices for percutaneous ablation are vulnerable to patient motion. The objective of this study is to develop and evaluate a software system for an MRI-compatible patient-mounted needle guide device that can adaptively compensate for displacement of the device due to patient motion using a novel image-based automatic device-to-image registration technique. We have developed a software system for an MRI-compatible patient-mounted needle guide device for percutaneous ablation. It features fully-automated image-based device-to-image registration to track the device position, and a device controller to adjust the needle trajectory to compensate for the displacement of the device. We performed: (a) a phantom study using a clinical MR scanner to evaluate registration performance; (b) simulations using intraoperative time-series MR data acquired in 20 clinical cases of MRI-guided renal cryoablations to assess its impact on motion compensation; and (c) a pilot clinical study in three patients to test its feasibility during the clinical procedure. FRE, TRE, and success rate of device-to-image registration were mm, mm, and 98.3% for the phantom images. The simulation study showed that the motion compensation reduced the targeting error for needle placement from 8.2 mm to 5.4 mm (p  <  0.0005) in patients under general anesthesia (GA), and from 14.4 mm to 10.0 mm () in patients under monitored anesthesia care (MAC). The pilot study showed that the software registered the device successfully in a clinical setting. Our simulation study demonstrated that the software system could significantly improve targeting accuracy in patients treated under both MAC and GA. Intraprocedural image-based device-to-image registration was feasible.

Geographic Distribution of CT, MRI and PET Devices in Japan: A Longitudinal Analysis Based on National Census Data.

PubMed

Matsumoto, Masatoshi; Koike, Soichi; Kashima, Saori; Awai, Kazuo

2015-01-01

Japan has the most CT and MRI scanners per unit population in the world; however, the geographic distribution of these technologies is currently unknown. Moreover, nothing is known of the cause-effect relationship between the number of diagnostic imaging devices and their geographic distribution. Data on the number of CT, MRI and PET devices and that of their utilizations in all 1829 municipalities of Japan was generated, based on the Static Survey of Medical Institutions conducted by the government. The inter-municipality equity of the number of devices or utilizations was evaluated with Gini coefficient. Between 2005 and 2011, the number of CT, MRI and PET devices in Japan increased by 47% (8789 to 12945), 19% (5034 to 5990) and 70% (274 to 466), respectively. Gini coefficient of the number of devices was largest for PET and smallest for CT (p for PET-MRI difference <0.001; MRI-CT difference <0.001). For all three modalities, Gini coefficient steadily decreased (p for 2011-2005 difference: <0.001 for CT; 0.003 for MRI; and <0.001 for PET). The number of devices in old models (single-detector CT, MRI<1.5 tesla, and conventional PET) decreased, while that in new models (multi-detector CT, MRI≥1.5 tesla, and PET-CT) increased. Gini coefficient of the old models increased or remained unchanged (increase rate of 9%, 3%, and -1%; p for 2011-2008 difference <0.001, 0.072, and 0.562, respectively), while Gini coefficient of the new models decreased (-10%, -9%, and -10%; p for 2011-2008 difference <0.001, <0.001, and <0.001 respectively). Similar results were observed in terms of utilizations. The more abundant a modality, the more equal the modality's distribution. Any increase in the modality made its distribution more equal. The geographic distribution of the diagnostic imaging technology in Japan appears to be affected by spatial competition derived from a market force.

A wearable bluetooth LE sensor for patient monitoring during MRI scans.

PubMed

Vogt, Christian; Reber, Jonas; Waltisberg, Daniel; Buthe, Lars; Marjanovic, Josip; Munzenrieder, Niko; Pruessmann, Klaas P; Troster, Gerhard

2016-08-01

This paper presents a working prototype of a wearable patient monitoring device capable of recording the heart rate, blood oxygen saturation, surface temperature and humidity during an magnetic resonance imaging (MRI) experiment. The measured values are transmitted via Bluetooth low energy (LE) and displayed in real time on a smartphone on the outside of the MRI room. During 7 MRI image acquisitions of at least 1 min and a total duration of 25 min no Bluetooth data packets were lost. The raw measurements of the light intensity for the photoplethysmogram based heart rate measurement shows an increased noise floor by 50LSB (least significant bit) during the MRI operation, whereas the temperature and humidity readings are unaffected. The device itself creates a magnetic resonance (MR) signal loss with a radius of 14 mm around the device surface and shows no significant increase in image noise of an acquired MRI image due to its radio frequency activity. This enables continuous and unobtrusive patient monitoring during MRI scans.

MR-compatibility assessment of the first preclinical PET-MRI insert equipped with digital silicon photomultipliers.

PubMed

Wehner, J; Weissler, B; Dueppenbecker, P M; Gebhardt, P; Goldschmidt, B; Schug, D; Kiessling, F; Schulz, V

2015-03-21

PET (positron emission tomography) with its high sensitivity in combination with MRI (magnetic resonance imaging) providing anatomic information with good soft-tissue contrast is considered to be a promising hybrid imaging modality. However, the integration of a PET detector into an MRI system is a challenging task since the MRI system is a sensitive device for external disturbances and provides a harsh environment for electronic devices. Consequently, the PET detector has to be transparent for the MRI system and insensitive to electromagnetic disturbances. Due to the variety of MRI protocols imposing a wide range of requirements regarding the MR-compatibility, an extensive study is mandatory to reliably assess worst-case interference phenomena between the PET detector and the MRI scanner. We have built the first preclinical PET insert, designed for a clinical 3 T MRI, using digital silicon photomultipliers (digital SiPM, type DPC 3200-22, Philips Digital Photon Counting). Since no thorough interference investigation with this new digital sensor has been reported so far, we present in this work such a comprehensive MR-compatibility study. Acceptable distortion of the B0 field homogeneity (volume RMS = 0.08 ppm, peak-to-peak value = 0.71 ppm) has been found for the PET detector installed. The signal-to-noise ratio degradation stays between 2-15% for activities up to 21 MBq. Ghosting artifacts were only found for demanding EPI (echo planar imaging) sequences with read-out gradients in Z direction caused by additional eddy currents originated from the PET detector. On the PET side, interference mainly between the gradient system and the PET detector occurred: extreme gradient tests were executed using synthetic sequences with triangular pulse shape and maximum slew rate. Under this condition, a relative degradation of the energy (⩽10%) and timing (⩽15%) resolution was noticed. However, barely measurable performance deterioration occurred when morphological MRI protocols are conducted certifying that the overall PET performance parameters remain unharmed.

Ex-PRESS glaucoma filter: an MRI compatible metallic orbital foreign body imaged at 1.5 and 3T.

PubMed

Mabray, M C; Uzelac, A; Talbott, J F; Lin, S C; Gean, A D

2015-05-01

To report on the MRI compatibility of the Ex-PRESS glaucoma filtration device, a tiny metallic implant placed into the anterior chamber of the eye that is much smaller than traditional glaucoma shunts, and to educate the radiology community regarding its appearance. Seven patients with Ex-PRESS glaucoma filtration devices were identified that had undergone MRI at San Francisco General Hospital/University of California San Francisco Medical Center by searching and cross-referencing the radiology reporting system and the electronic medical record. MRI images were reviewed for artefact interfering with interpretation. Ophthalmology examinations were reviewed for evidence of complications. Eighteen individual MRI examinations were performed during 12 unique MRI events on these 7 patients. 13/18 individual MRI examinations and 7/12 MRI events were performed at 3 T with the others performed at 1.5 T. Mean time from Ex-PRESS implantation to MRI was 17.5 months. Mean time from MRI to first ophthalmology examination was 1.1 months and from MRI to latest ophthalmology examination was 6.6 months. Susceptibility artefact did not interfere with image interpretation and no complications related to MRI were encountered. The Ex-PRESS glaucoma filtration device appears to be safe for MRI at 1.5 and 3 T and does not produce significant susceptibility artefact to affect diagnostic interpretation adversely. Copyright © 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

75 FR 7282 - Circulatory System Devices Panel of the Medical Devices Advisory Committee; Notice of Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-18

... March 19, 2010, the committee will discuss, make recommendations and vote on a PMA for the REVO MRI Pacemaker System sponsored by Medtronic. The REVO MRI Pacing System is a pacemaker (with a standard pacing indication) that has been specifically designed to be safe for the MRI environment under certain MR scanning...

Spinal cord stimulation: a review of the safety literature and proposal for perioperative evaluation and management.

PubMed

Walsh, Kevin M; Machado, Andre G; Krishnaney, Ajit A

2015-08-01

There is currently no consensus on appropriate perioperative management of patients with spinal cord stimulator implants. Magnetic resonance imaging (MRI) is considered safe under strict labeling conditions. Electrocautery is generally not recommended in these patients but sometimes used despite known risks. The aim was to discuss the perioperative evaluation and management of patients with spinal cord stimulator implants. A literature review, summary of device labeling, and editorial were performed, regarding the safety of spinal cord stimulator devices in the perioperative setting. A literature review was performed, and the labeling of each Food and Drug Administration (FDA)-approved spinal cord stimulation system was reviewed. The literature review was performed using PubMed and the FDA website (www.fda.gov). Magnetic resonance imaging safety recommendations vary between the models. Certain systems allow for MRI of the brain to be performed, and only one system allows for MRI of the body to be performed, both under strict labeling conditions. Before an MRI is performed, it is imperative to ascertain that the system is intact, without any lead breaks or low impedances, as these can result in heating of the spinal cord stimulation (SCS) and injury to the patient. Monopolar electrocautery is generally not recommended for patients with SCS; however, in some circumstances, it is used when deemed required by the surgeon. When cautery is necessary, bipolar electrocautery is recommended. Modern electrocautery units are to be used with caution as there remains a risk of thermal injury to the tissue in contact with the SCS. As with MRI, electrocautery usage in patients with SCS systems with suspected breaks or abnormal impedances is unsafe and may cause injury to the patient. Spinal cord stimulation is increasingly used in patients with pain of spinal origin, particularly to manage postlaminectomy syndrome. Knowledge of the safety concerns of SCS and appropriate perioperative evaluation and management of the SCS system can reduce risks and improve surgical planning. Copyright © 2015 Elsevier Inc. All rights reserved.

fMRI brain mapping during motion capture and FES induced motor tasks: signal to noise ratio assessment.

PubMed

Gandolla, Marta; Ferrante, Simona; Casellato, Claudia; Ferrigno, Giancarlo; Molteni, Franco; Martegani, Alberto; Frattini, Tiziano; Pedrocchi, Alessandra

2011-10-01

Functional Electrical Stimulation (FES) is a well known clinical rehabilitation procedure, however the neural mechanisms that underlie this treatment at Central Nervous System (CNS) level are still not completely understood. Functional magnetic resonance imaging (fMRI) is a suitable tool to investigate effects of rehabilitative treatments on brain plasticity. Moreover, monitoring the effective executed movement is needed to correctly interpret activation maps, most of all in neurological patients where required motor tasks could be only partially accomplished. The proposed experimental set-up includes a 1.5 T fMRI scanner, a motion capture system to acquire kinematic data, and an electro-stimulation device. The introduction of metallic devices and of stimulation current in the MRI room could affect fMRI acquisitions so as to prevent a reliable activation maps analysis. What we are interested in is that the Blood Oxygenation Level Dependent (BOLD) signal, marker of neural activity, could be detected within a given experimental condition and set-up. In this paper we assess temporal Signal to Noise Ratio (SNR) as image quality index. BOLD signal change is about 1-2% as revealed by a 1.5 T scanner. This work demonstrates that, with this innovative set-up, in the main cortical sensorimotor regions 1% BOLD signal change can be detected at least in the 93% of the sub-volumes, and almost 100% of the sub-volumes are suitable for 2% signal change detection. The integrated experimental set-up will therefore allows to detect FES induced movements fMRI maps simultaneously with kinematic acquisitions so as to investigate FES-based rehabilitation treatments contribution at CNS level. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

Enabling Real-Time Volume Rendering of Functional Magnetic Resonance Imaging on an iOS Device.

PubMed

Holub, Joseph; Winer, Eliot

2017-12-01

Powerful non-invasive imaging technologies like computed tomography (CT), ultrasound, and magnetic resonance imaging (MRI) are used daily by medical professionals to diagnose and treat patients. While 2D slice viewers have long been the standard, many tools allowing 3D representations of digital medical data are now available. The newest imaging advancement, functional MRI (fMRI) technology, has changed medical imaging from viewing static to dynamic physiology (4D) over time, particularly to study brain activity. Add this to the rapid adoption of mobile devices for everyday work and the need to visualize fMRI data on tablets or smartphones arises. However, there are few mobile tools available to visualize 3D MRI data, let alone 4D fMRI data. Building volume rendering tools on mobile devices to visualize 3D and 4D medical data is challenging given the limited computational power of the devices. This paper describes research that explored the feasibility of performing real-time 3D and 4D volume raycasting on a tablet device. The prototype application was tested on a 9.7" iPad Pro using two different fMRI datasets of brain activity. The results show that mobile raycasting is able to achieve between 20 and 40 frames per second for traditional 3D datasets, depending on the sampling interval, and up to 9 frames per second for 4D data. While the prototype application did not always achieve true real-time interaction, these results clearly demonstrated that visualizing 3D and 4D digital medical data is feasible with a properly constructed software framework.

Evaluation of a magnetic resonance-compatible dentoalveolar tactile stimulus device.

PubMed

Moana-Filho, Estephan J; Nixdorf, Donald R; Bereiter, David A; John, Mike T; Harel, Noam

2010-10-28

Few methods exist to study central nervous system processes following dentoalveolar tactile stimulation using functional magnetic resonance imaging (fMRI), likely due to inherent technical difficulties. Our primary goal was to develop and perform feasibility testing of a novel device capable of delivering valid and reliable dentoalveolar stimuli at dental chair-side and during MRI. Details of a device designed to deliver dentoalveolar dynamic pressure stimuli are described. Device testing took place in three settings: a) laboratory testing to assess range of stimulus force intensities, b) dental chair-side to assess reliability, validity and discriminant ability in force-pain relationship; and c) MRI to evaluate magnetic compatibility and ability to evoke brain activation in painfree subjects similar to those described in the literature. A novel device capable of delivering valid and reliable dentoalveolar somatosensory stimulation was developed (ICC = 0.89, 0.78-1 [95% CI]). Psychophysical data analysis showed high discriminant ability in differentiating painfree controls from cases with chronic dentoalveolar pain related to deafferenting dental procedures (sensitivity = 100%, specificity = 86.7%, area under ROC curve = 0.99). FMRI results of dentoalveolar dynamic pressure pain in painfree subjects revealed activation of brain areas typically associated with acute pain processing including thalamus, primary/secondary somatosensory, insular and prefrontal cortex. A novel psychophysical method to deliver dynamic dentoalveolar pressure stimulation was developed and validated, allowing non-invasive MRI-based exploration of central nervous system function in response to intraoral somatosensation. The organization of the trigeminal system is unique as it provides somatosensory innervation to the face, masticatory and oral structures, the majority of the intracranial contents 1 and to specialized structures (tongue, nasal mucosa, auricle, tympanic membrane, cornea and part of the conjunctiva) 2. Somatic sensory information transmitted by the trigeminal nerve is crucial for normal orofacial function; however, the mechanisms of many chronic pain conditions affecting areas innervated by this sensory system are not well understood 345. The clinical presentation of chronic intraoral pain in the area of a tooth or in a site formally occupied by a tooth with no clinical or radiological signs of pathology, referred to as atypical odontalgia (AO) 67, is one such chronic pain condition of particular interest to dentists that is difficult to diagnose and manage. Recent research suggests both peripheral and central nervous system mechanisms being involved in AO pathophysiology 8910, but the majority of mechanism-based research of patients with AO has focused on the "peripheral aspect" 7.Functional magnetic resonance imaging (fMRI) is an established research technique to study the central aspects of pain 11. Of existing neuroimaging techniques, fMRI provides good spatial resolution of cortical and subcortical structures critical in the processing of nociception, acceptable temporal resolution, does not involve ionizing radiation, and can be performed using most MRI systems that already exist in research centers and the community. For these reasons, we sought to develop a protocol that allows us to use this tool to investigate the central mechanisms involved in the processes of intraoral pain arising from the dentoalveolar region. Using this device, our long-term objective is to improve our understanding of the underlying mechanisms of persistent dentoalveolar pain.In the past few years several studies used fMRI to investigate the human trigeminal system 1213, with a limited subset focusing on intraoral stimulation - specifically on the dentoalveolar processes, such as lip, tongue and teeth stimulation 14 or only teeth 151617. Some reasons for scarce literature on this topic may be the technical challenges involved in delivering facial/intraoral stimulation inside a MR scanner 1718: possibility of magnetic interference, detriment of image quality, subject discomfort and reduced working space between the subject's head and the radiofrequency coil. As a consequence a MR-compatible device would need to not only overcome these challenges but also be capable of delivering a controlled and reproducible stimuli 19, as reliability/reproducibility is a necessary feature of sensory testing 20.Existing MR-compatible methods of dentoalveolar stimulation are limited and do not adequately deliver stimuli across a range of non-painful to painful intensities and/or cannot be adjusted to reach posterior aspects of the dentoalveolar region. Therefore our goal was to develop and test the feasibility of a device able to: 1) provide reliable and valid dentoalveolar stimuli, 2) deliver such stimulation within the restricted space of an MR head coil, 3) be compatible for use within an MR environment, and 4) produce brain activation in painfree controls consistent to those observed by others using fMRI.

Advancements in Orthopedic Intervention: Retrograde Drilling and Bone Grafting of Osteochondral Lesions of the Knee Using Magnetic Resonance Imaging Guidance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seebauer, Christian J., E-mail: christian.seebauer@charite.d; Bail, Hermann J., E-mail: hermann-josef.bail@klinikum-nuernberg.d; Rump, Jens C., E-mail: jens.rump@charite.de

Computer-assisted surgery is currently a novel challenge for surgeons and interventional radiologists. Magnetic resonance imaging (MRI)-guided procedures are still evolving. In this experimental study, we describe and assess an innovative passive-navigation method for MRI-guided treatment of osteochondritis dissecans of the knee. A navigation principle using a passive-navigation device was evaluated in six cadaveric knee joint specimens for potential applicability in retrograde drilling and bone grafting of osteochondral lesions using MRI guidance. Feasibility and accuracy were evaluated in an open MRI scanner (1.0 T Philips Panorama HFO MRI System). Interactive MRI navigation allowed precise drilling and bone grafting of osteochondral lesionsmore » of the knee. All lesions were hit with an accuracy of 1.86 mm in the coronal plane and 1.4 mm the sagittal plane. Targeting of all lesions was possible with a single drilling. MRI allowed excellent assessment of correct positioning of the cancellous bone cylinder during bone grafting. The navigation device and anatomic structures could be clearly identified and distinguished throughout the entire drilling procedure. MRI-assisted navigation method using a passive navigation device is feasible for the treatment of osteochondral lesions of the knee under MRI guidance and allows precise and safe drilling without exposure to ionizing radiation. This method may be a viable alternative to other navigation principles, especially for pediatric and adolescent patients. This MRI-navigated method is also potentially applicable in many other MRI-guided interventions.« less

A simple device for respiratory gating for the MRI of laboratory animals.

PubMed

Burdett, N G; Carpenter, T A; Hall, L D

1993-01-01

Respiratory motion must be overcome if MRI of the abdomen, even at the lowest resolution, is to be performed satisfactorily. A simple and reliable respiratory gating device, based on the interruption of an infrared (IR) optical beam is described. This device has the advantage that gating is based on the position of the chest as opposed to its velocity, and that it can be used without degrading the radiofrequency isolation of a Faraday cage. Its use in animal MRI is illustrated by high resolution (200 microns) images of in vivo rat liver and kidney.

Neurofeedback and networks of depression

PubMed Central

Linden, David E. J.

2014-01-01

Recent advances in imaging technology and in the understanding of neural circuits relevant to emotion, motivation, and depression have boosted interest and experimental work in neuromodulation for affective disorders. Real-time functional magnetic resonance imaging (fMRI) can be used to train patients in the self regulation of these circuits, and thus complement existing neurofeedback technologies based on electroencephalography (EEG). EEG neurofeedback for depression has mainly been based on models of altered hemispheric asymmetry. fMRI-based neurofeedback (fMRI-NF) can utilize functional localizer scans that allow the dynamic adjustment of the target areas or networks for self-regulation training to individual patterns of emotion processing. An initial application of fMRI-NF in depression has produced promising clinical results, and further clinical trials are under way. Challenges lie in the design of appropriate control conditions for rigorous clinical trials, and in the transfer of neurofeedback protocols from the laboratory to mobile devices to enhance the sustainability of any clinical benefits. PMID:24733975

MR compatible positioning device for guiding a focused ultrasound system for the treatment of brain deseases.

PubMed

Mylonas, N; Damianou, C

2014-03-01

A prototype magnetic resonance imaging (MRI)-compatible positioning device that navigates a high intensity focused ultrasound (HIFU) transducer is presented. The positioning device has three user-controlled degrees of freedom that allow access to brain targets using a lateral coupling approach. The positioning device can be used for the treatment of brain cancer (thermal mode ultrasound) or ischemic stroke (mechanical mode ultrasound). The positioning device incorporates only MRI compatible materials such as piezoelectric motors, ABS plastic, brass screws, and brass rack and pinion. The robot has the ability to accurately move the transducer thus creating overlapping lesions in rabbit brain in vivo. The registration and repeatability of the system was evaluated using tissues in vitro and gel phantom and was also tested in vivo in the brain of a rabbit. A simple, cost effective, portable positioning device has been developed which can be used in virtually any clinical MRI scanner since it can be placed on the table of the MRI scanner. This system can be used to treat in the future patients with brain cancer and ischemic stroke. Copyright © 2013 John Wiley & Sons, Ltd.

Robot-assisted real-time magnetic resonance image-guided transcatheter aortic valve replacement.

PubMed

Miller, Justin G; Li, Ming; Mazilu, Dumitru; Hunt, Tim; Horvath, Keith A

2016-05-01

Real-time magnetic resonance imaging (rtMRI)-guided transcatheter aortic valve replacement (TAVR) offers improved visualization, real-time imaging, and pinpoint accuracy with device delivery. Unfortunately, performing a TAVR in a MRI scanner can be a difficult task owing to limited space and an awkward working environment. Our solution was to design a MRI-compatible robot-assisted device to insert and deploy a self-expanding valve from a remote computer console. We present our preliminary results in a swine model. We used an MRI-compatible robotic arm and developed a valve delivery module. A 12-mm trocar was inserted in the apex of the heart via a subxiphoid incision. The delivery device and nitinol stented prosthesis were mounted on the robot. Two continuous real-time imaging planes provided a virtual real-time 3-dimensional reconstruction. The valve was deployed remotely by the surgeon via a graphic user interface. In this acute nonsurvival study, 8 swine underwent robot-assisted rtMRI TAVR for evaluation of feasibility. Device deployment took a mean of 61 ± 5 seconds. Postdeployment necropsy was performed to confirm correlations between imaging and actual valve positions. These results demonstrate the feasibility of robotic-assisted TAVR using rtMRI guidance. This approach may eliminate some of the challenges of performing a procedure while working inside of an MRI scanner, and may improve the success of TAVR. It provides superior visualization during the insertion process, pinpoint accuracy of deployment, and, potentially, communication between the imaging device and the robotic module to prevent incorrect or misaligned deployment. Copyright © 2016 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

A Review of Numerical Simulation and Analytical Modeling for Medical Devices Safety in MRI

PubMed Central

Kabil, J.; Belguerras, L.; Trattnig, S.; Pasquier, C.; Missoffe, A.

2016-01-01

Summary Objectives To review past and present challenges and ongoing trends in numerical simulation for MRI (Magnetic Resonance Imaging) safety evaluation of medical devices. Methods A wide literature review on numerical and analytical simulation on simple or complex medical devices in MRI electromagnetic fields shows the evolutions through time and a growing concern for MRI safety over the years. Major issues and achievements are described, as well as current trends and perspectives in this research field. Results Numerical simulation of medical devices is constantly evolving, supported by calculation methods now well-established. Implants with simple geometry can often be simulated in a computational human model, but one issue remaining today is the experimental validation of these human models. A great concern is to assess RF heating on implants too complex to be traditionally simulated, like pacemaker leads. Thus, ongoing researches focus on alternative hybrids methods, both numerical and experimental, with for example a transfer function method. For the static field and gradient fields, analytical models can be used for dimensioning simple implants shapes, but limited for complex geometries that cannot be studied with simplifying assumptions. Conclusions Numerical simulation is an essential tool for MRI safety testing of medical devices. The main issues remain the accuracy of simulations compared to real life and the studies of complex devices; but as the research field is constantly evolving, some promising ideas are now under investigation to take up the challenges. PMID:27830244

Approaches to creating and controlling motion in MRI.

PubMed

Fischer, Gregory S; Cole, Gregory; Su, Hao

2011-01-01

Magnetic Resonance Imaging (MRI) can provide three dimensional (3D) imaging with excellent resolution and sensitivity making it ideal for guiding and monitoring interventions. The development of MRI-compatible interventional devices is complicated by factors including: the high magnetic field strength, the requirement that such devices should not degrade image quality, and the confined physical space of the scanner bore. Numerous MRI guided actuated devices have been developed or are currently being developed utilizing piezoelectric actuators as their primary means of mechanical energy generation to enable better interventional procedure performance. While piezoelectric actuators are highly desirable for MRI guided actuation for their precision, high holding force, and non-magnetic operation they are often found to cause image degradation on a large enough to scale to render live imaging unusable. This paper describes a newly developed piezoelectric actuator driver and control system designed to drive a variety of both harmonic and non-harmonic motors that has been demonstrated to be capable of operating both harmonic and non-harmonic piezoelectric actuators with less than 5% SNR loss under closed loop control. The proposed system device allows for a single controller to control any supported actuator and feedback sensor without any physical hardware changes.

Vibration and Noise in Magnetic Resonance Imaging of the Vocal Tract: Differences between Whole-Body and Open-Air Devices.

PubMed

Přibil, Jiří; Přibilová, Anna; Frollo, Ivan

2018-04-05

This article compares open-air and whole-body magnetic resonance imaging (MRI) equipment working with a weak magnetic field as regards the methods of its generation, spectral properties of mechanical vibration and acoustic noise produced by gradient coils during the scanning process, and the measured noise intensity. These devices are used for non-invasive MRI reconstruction of the human vocal tract during phonation with simultaneous speech recording. In this case, the vibration and noise have negative influence on quality of speech signal. Two basic measurement experiments were performed within the paper: mapping sound pressure levels in the MRI device vicinity and picking up vibration and noise signals in the MRI scanning area. Spectral characteristics of these signals are then analyzed statistically and compared visually and numerically.

Right ventricular functional analysis utilizing first pass radionuclide angiography for pre-operative ventricular assist device planning: a multi-modality comparison.

PubMed

Avery, Ryan; Day, Kevin; Jokerst, Clinton; Kazui, Toshinobu; Krupinski, Elizabeth; Khalpey, Zain

2017-10-10

Advanced heart failure treated with a left ventricular assist device is associated with a higher risk of right heart failure. Many advanced heart failures patients are treated with an ICD, a relative contraindication to MRI, prior to assist device placement. Given this limitation, left and right ventricular function for patients with an ICD is calculated using radionuclide angiography utilizing planar multigated acquisition (MUGA) and first pass radionuclide angiography (FPRNA), respectively. Given the availability of MRI protocols that can accommodate patients with ICDs, we have correlated the findings of ventricular functional analysis using radionuclide angiography to cardiac MRI, the reference standard for ventricle function calculation, to directly correlate calculated ejection fractions between these modalities, and to also assess agreement between available echocardiographic and hemodynamic parameters of right ventricular function. A retrospective review from January 2012 through May 2014 was performed to identify advanced heart failure patients who underwent both cardiac MRI and radionuclide angiography for ventricular functional analysis. Nine heart failure patients (8 men, 1 woman; mean age of 57.0 years) were identified. The average time between the cardiac MRI and radionuclide angiography exams was 38.9 days (range: 1 - 119 days). All patients undergoing cardiac MRI were scanned using an institutionally approved protocol for ICD with no device-related complications identified. A retrospective chart review of each patient for cardiomyopathy diagnosis, clinical follow-up, and echocardiogram and right heart catheterization performed during evaluation was also performed. The 9 patients demonstrated a mean left ventricular ejection fraction (LVEF) using cardiac MRI of 20.7% (12 - 40%). Mean LVEF using MUGA was 22.6% (12 - 49%). The mean right ventricular ejection fraction (RVEF) utilizing cardiac MRI was 28.3% (16 - 43%), and the mean RVEF calculated by FPRNA was 32.6% (9 - 56%). The mean discrepancy for LVEF between cardiac MRI and MUGA was 4.1% (0 - 9%), and correlation of calculated LVEF using cardiac MRI and MUGA demonstrated an R of 0.9. The mean discrepancy for RVEF between cardiac MRI and FPRNA was 12.0% (range: 2 - 24%) with a moderate correlation (R = 0.5). The increased discrepancies for RV analysis were statistically significant using an unpaired t-test (t = 3.19, p = 0.0061). Echocardiogram parameters of RV function, including TAPSE and FAC, were for available for all 9 patients and agreement with cardiac MRI demonstrated a kappa statistic for TAPSE of 0.39 (95% CI of 0.06 - 0.72) and for FAC of 0.64 (95% of 0.21 - 1.00). Heart failure patients are increasingly requiring left ventricular assist device placement; however, definitive evaluation of biventricular function is required due to the increased mortality rate associated with right heart failure after assist device placement. Our results suggest that FPRNA only has a moderate correlation with reference standard RVEFs calculated using cardiac MRI, which was similar to calculated agreements between cardiac MRI and echocardiographic parameters of right ventricular function. Given the need for identification of patients at risk for right heart failure, further studies are warranted to determine a more accurate estimate of RVEF for heart failure patients during pre-operative ventricular assist device planning.

A cryogen-free ultralow-field superconducting quantum interference device magnetic resonance imaging system.

PubMed

Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob

2014-09-01

Magnetic resonance imaging (MRI) at microtesla fields using superconducting quantum interference device (SQUID) detection has previously been demonstrated, and advantages have been noted. Although the ultralow-field SQUID MRI technique would not need the heavy superconducting magnet of conventional MRI systems, liquid helium required to cool the low-temperature detector still places a significant burden on its operation. We have built a prototype cryocooler-based SQUID MRI system that does not require a cryogen. The SQUID detector and the superconducting gradiometer were cooled down to 3.7 K and 4.3 K, respectively. We describe the prototype design, characterization, a phantom image, and areas of further improvements needed to bring the imaging performance to parity with conventional MRI systems.

Device for sectioning prostatectomy specimens to facilitate comparison between histology and in vivo MRI

PubMed Central

Drew, Bryn; Jones, Edward C.; Reinsberg, Stefan; Yung, Andrew C.; Goldenberg, S. Larry; Kozlowski, Piotr

2012-01-01

Purpose To develop a device for sectioning prostatectomy specimens that would facilitate comparison between histology and in vivo MRI. Materials and methods A multi-bladed cutting device was developed, which consists of an adjustable box capable of accommodating a prostatectomy specimen up to 85 mm in size in the lateral direction, a “plunger” tool to press on the excised gland from the top to prevent it from rolling or sliding during sectioning, and a multi-bladed knife assembly capable of holding up to 21 blades at 4 mm intervals. The device was tested on a formalin fixed piece of meat and subsequently used to section a prostatectomy specimen. Histology sections were compared with T2-weighted MR images acquired in vivo prior to the prostatectomy procedure. Results The prostatectomy specimen slices were very uniform in thickness with each face parallel to the other with no visible sawing marks on the sections by the blades after the cut. MRI and histology comparison showed good correspondence between the two images. Conclusion The developed device allows sectioning of prostatectomy specimens into parallel cuts at a specific orientation and fixed intervals. Such a device is useful in facilitating accurate correlation between histology and MRI data. PMID:20882632

Alleviating artifacts in 1H MRI thermometry by single scan spatiotemporal encoding.

PubMed

Schmidt, Rita; Frydman, Lucio

2013-10-01

Recent years have seen an increased interest in combining MRI thermometry with devices capable of destroying malignancies by heat ablation. Expected from the MR protocols are accurate and fast thermal characterizations, providing real time feedback on restricted tissue volumes and/or rapidly moving organs like liver. This article explores the potential advantages of relying on spatiotemporally encoded (SPEN) sequences for retrieving real-time thermometric images based on the water's proton resonance frequency (PRF) shifts. Hybrid spatiotemporal/k-space encoding single-scan MRI experiments were implemented on animal and human scanners, and their abilities to deliver single- and multi-slice real-time thermometric measurements based on PRF-derived phase maps in phantoms and in vivo, were compared against echo planar imaging (EPI) and gradient-echo counterparts. Under comparable acquisition conditions, SPEN exhibited advantages vis-à-vis EPI in terms of dealing with inhomogeneous magnetic field distortions, with shifts arising due to changes in the central frequency offsets, with PRF distributions, and for zooming into restricted fields-of-view without special pulse sequence provisions. This work confirms the ability of SPEN sequences, particularly when implemented under fully-refocused conditions, to exploit their built-in robustness to shift- and field-derived inhomogeneities for monitoring thermal changes in real-time under in vitro and in vivo conditions.

Diagnostic Value of MRI in Patients With Implanted Pacemakers and Implantable Cardioverter-Defibrillators Across a Cross Population: Does the Benefit Justify the Risk? A Proof of Concept Study.

PubMed

Samar, Huma; Yamrozik, June A; Williams, Ronald B; Doyle, Mark; Shah, Moneal; Bonnet, Christopher A; Biederman, Robert W W

2017-09-01

The objective of this study was to assess the diagnostic usefulness of thoracic and nonthoracic magnetic resonance imaging (MRI) imaging in patients with implantable cardiac devices (permanent pacemaker or implantable cardioverter-defibrillators [ICDs]) to determine if there was a substantial benefit to patients with regard to diagnosis and/or management. MRI is infrequently performed on patients with conventional pacemakers or ICDs. Multiple studies have documented the safety of MRI scans in patients with implanted devices, yet the diagnostic value of this approach has not been established. Evaluation data were acquired in 136 patients with implanted cardiac devices who underwent MRIs during a 10-year period at a single institution. Specific criteria were followed for all patients to objectively define if the diagnosis by MRI enhanced patient care; 4 questions were answered after scan interpretation by both MRI technologists and MRI physicians who performed the scan. 1) Did the primary diagnosis change? 2) Did the MRI provide additional information to the existing diagnosis? 3) Was the pre-MRI (tentative) diagnosis confirmed? 4) Did patient management change? If "Yes" was answered to any of the preceding questions, the MRI scan was considered to be of value to patient diagnosis and/or therapy. In 97% (n = 132) of patients, MR added value to patient diagnosis and management. In 49% (n = 67) of patients, MRI added additional valuable information to the primary diagnosis, and in 30% (n = 41) of patients, MRI changed the principle diagnosis and subsequent management of the patient. No safety issues were encountered, and no adverse effects of undergoing the MRI scan were noted in any patient. MRI in patients with implanted pacemakers and defibrillators added value to patient diagnosis and management, which justified the risk of the procedure. Published by Elsevier Inc.

Modern Pacemaker and Implantable Cardioverter/Defibrillator Systems Can Be Magnetic Resonance Imaging Safe

PubMed Central

Roguin, Ariel; Zviman, Menekhem M.; Meininger, Glenn R.; Rodrigues, E. Rene; Dickfeld, Timm M.; Bluemke, David A.; Lardo, Albert; Berger, Ronald D.; Calkins, Hugh; Halperin, Henry R.

2011-01-01

Background MRI has unparalleled soft-tissue imaging capabilities. The presence of devices such as pacemakers and implantable cardioverter/defibrillators (ICDs), however, is historically considered a contraindication to MRI. These devices are now smaller, with less magnetic material and improved electromagnetic interference protection. Our aim was to determine whether these modern systems can be used in an MR environment. Methods and Results We tested in vitro and in vivo lead heating, device function, force acting on the device, and image distortion at 1.5 T. Clinical MR protocols and in vivo measurements yielded temperature changes <0.5°C. Older (manufactured before 2000) ICDs were damaged by the MR scans. Newer ICD systems and most pacemakers, however, were not. The maximal force acting on newer devices was <100 g. Modern (manufactured after 2000) ICD systems were implanted in dogs (n=18), and after 4 weeks, 3- to 4-hour MR scans were performed (n=15). No device dysfunction occurred. The images were of high quality with distortion dependent on the scan sequence and plane. Pacing threshold and intracardiac electrogram amplitude were unchanged over the 8 weeks, except in 1 animal that, after MRI, had a transient (<12 hours) capture failure. Pathological data of the scanned animals revealed very limited necrosis or fibrosis at the tip of the lead area, which was not different from controls (n=3) not subjected to MRI. Conclusions These data suggest that certain modern pacemaker and ICD systems may indeed be MRI safe. This may have major clinical implications for current imaging practices. PMID:15277324

Isolating the auditory system from acoustic noise during functional magnetic resonance imaging: Examination of noise conduction through the ear canal, head, and bodya)

PubMed Central

Ravicz, Michael E.; Melcher, Jennifer R.

2007-01-01

Approaches were examined for reducing acoustic noise levels heard by subjects during functional magnetic resonance imaging (fMRI), a technique for localizing brain activation in humans. Specifically, it was examined whether a device for isolating the head and ear canal from sound (a “helmet”) could add to the isolation provided by conventional hearing protection devices (i.e., earmuffs and earplugs). Both subjective attenuation (the difference in hearing threshold with versus without isolation devices in place) and objective attenuation (difference in ear-canal sound pressure) were measured. In the frequency range of the most intense fMRI noise (1–1.4 kHz), a helmet, earmuffs, and earplugs used together attenuated perceived sound by 55–63 dB, whereas the attenuation provided by the conventional devices alone was substantially less: 30–37 dB for earmuffs, 25–28 dB for earplugs, and 39–41 dB for earmuffs and earplugs used together. The data enabled the clarification of the relative importance of ear canal, head, and body conduction routes to the cochlea under different conditions: At low frequencies (≤500 Hz), the ear canal was the dominant route of sound conduction to the cochlea for all of the device combinations considered. At higher frequencies (>500 Hz), the ear canal was the dominant route when either earmuffs or earplugs were worn. However, the dominant route of sound conduction was through the head when both earmuffs and earplugs were worn, through both ear canal and body when a helmet and earmuffs were worn, and through the body when a helmet, earmuffs, and earplugs were worn. It is estimated that a helmet, earmuffs, and earplugs together will reduce the most intense fMRI noise levels experienced by a subject to 60–65 dB SPL. Even greater reductions in noise should be achievable by isolating the body from the surrounding noise field. PMID:11206150

Mobile Device Applications for the Visualization of Functional Connectivity Networks and EEG Electrodes: iBraiN and iBraiNEEG.

PubMed

Rojas, Gonzalo M; Fuentes, Jorge A; Gálvez, Marcelo

2016-01-01

Multiple functional MRI (fMRI)-based functional connectivity networks were obtained by Yeo et al. (2011), and the visualization of these complex networks is a difficult task. Also, the combination of functional connectivity networks determined by fMRI with electroencephalography (EEG) data could be a very useful tool. Mobile devices are becoming increasingly common among users, and for this reason, we describe here two applications for Android and iOS mobile devices: one that shows in an interactive way the seven Yeo functional connectivity networks, and another application that shows the relative position of 10-20 EEG electrodes with Yeo's seven functional connectivity networks.

A cryogen-free ultralow-field superconducting quantum interference device magnetic resonance imaging system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob, E-mail: ihahn@caltech.edu

2014-09-15

Magnetic resonance imaging (MRI) at microtesla fields using superconducting quantum interference device (SQUID) detection has previously been demonstrated, and advantages have been noted. Although the ultralow-field SQUID MRI technique would not need the heavy superconducting magnet of conventional MRI systems, liquid helium required to cool the low-temperature detector still places a significant burden on its operation. We have built a prototype cryocooler-based SQUID MRI system that does not require a cryogen. The SQUID detector and the superconducting gradiometer were cooled down to 3.7 K and 4.3 K, respectively. We describe the prototype design, characterization, a phantom image, and areas ofmore » further improvements needed to bring the imaging performance to parity with conventional MRI systems.« less

Functional MRI using robotic MRI compatible devices for monitoring rehabilitation from chronic stroke in the molecular medicine era (Review)

PubMed Central

ASTRAKAS, LOUKAS G.; NAQVI, SYED HASSAN ABBAS; KATEB, BABAK; TZIKA, A. ARIA

2012-01-01

The number of individuals suffering from stroke is increasing daily, and its consequences are a major contributor to invalidity in today’s society. Stroke rehabilitation is relatively new, having been hampered from the longstanding view that lost functions were not recoverable. Nowadays, robotic devices, which aid by stimulating brain plasticity, can assist in restoring movement compromised by stroke-induced pathological changes in the brain which can be monitored by MRI. Multiparametric magnetic resonance imaging (MRI) of stroke patients participating in a training program with a novel Magnetic Resonance Compatible Hand-Induced Robotic Device (MR_CHIROD) could yield a promising biomarker that, ultimately, will enhance our ability to advance hand motor recovery following chronic stroke. Using state-of-the art MRI in conjunction with MR_CHIROD-assisted therapy can provide novel biomarkers for stroke patient rehabilitation extracted by a meta-analysis of data. Successful completion of such studies may provide a ground breaking method for the future evaluation of stroke rehabilitation therapies. Their results will attest to the effectiveness of using MR-compatible hand devices with MRI to provide accurate monitoring during rehabilitative therapy. Furthermore, such results may identify biomarkers of brain plasticity that can be monitored during stroke patient rehabilitation. The potential benefit for chronic stroke patients is that rehabilitation may become possible for a longer period of time after stroke than previously thought, unveiling motor skill improvements possible even after six months due to retained brain plasticity. PMID:22426741

A Prospective Evaluation of a Protocol for Magnetic Resonance Imaging of Patients With Implanted Cardiac Devices

PubMed Central

Nazarian, Saman; Hansford, Rozann; Roguin, Ariel; Goldsher, Dorith; Zviman, Menekhem M.; Lardo, Albert C.; Caffo, Brian S.; Frick, Kevin D.; Kraut, Michael A.; Kamel, Ihab R.; Calkins, Hugh; Berger, Ronald D.; Bluemke, David A.; Halperin, Henry R.

2015-01-01

Background Magnetic resonance imaging (MRI) is avoided in most patients with implanted cardiac devices because of safety concerns. Objective To define the safety of a protocol for MRI at the commonly used magnetic strength of 1.5 T in patients with implanted cardiac devices. Design Prospective nonrandomized trial. (ClinicalTrials.gov registration number: NCT01130896) Setting One center in the United States (94% of examinations) and one in Israel. Patients 438 patients with devices (54% with pacemakers and 46% with defibrillators) who underwent 555 MRI studies. Intervention Pacing mode was changed to asynchronous for pacemaker-dependent patients and to demand for others. Tachy-arrhythmia functions were disabled. Blood pressure, electrocardiography, oximetry, and symptoms were monitored by a nurse with experience in cardiac life support and device programming who had immediate backup from an electrophysiologist. Measurements Activation or inhibition of pacing, symptoms, and device variables. Results In 3 patients (0.7% [95% CI, 0% to 1.5%]), the device reverted to a transient back-up programming mode without long-term effects. Right ventricular (RV) sensing (median change, 0 mV [interquartile range {IQR}, −0.7 to 0 V]) and atrial and right and left ventricular lead impedances (median change, −2 Ω[IQR, −13 to 0 Ω], −4 Ω [IQR, −16 to 0 Ω], and −11 Ω [IQR, −40 to 0 Ω], respectively) were reduced immediately after MRI. At long-term follow-up (61% of patients), decreased RV sensing (median, 0 mV, [IQR, −1.1 to 0.3 mV]), decreased RV lead impedance (median, −3 Ω, [IQR, −29 to 15 Ω]), increased RV capture threshold (median, 0 V, IQR, [0 to 0.2 Ω]), and decreased battery voltage (median, −0.01 V, IQR, −0.04 to 0 V) were noted. The observed changes did not require device revision or reprogramming. Limitations Not all available cardiac devices have been tested. Long-term in-person or telephone follow-up was unavailable in 43 patients (10%), and some data were missing. Those with missing long-term capture threshold data had higher baseline right atrial and right ventricular capture thresholds and were more likely to have undergone thoracic imaging. Defibrillation threshold testing and random assignment to a control group were not performed. Conclusion With appropriate precautions, MRI can be done safely in patients with selected cardiac devices. Because changes in device variables and programming may occur, electrophysiologic monitoring during MRI is essential. Primary Funding Source National Institutes of Health. PMID:21969340

Simultaneous MRI and PET imaging of a rat brain

NASA Astrophysics Data System (ADS)

Raylman, Raymond R.; Majewski, Stan; Lemieux, Susan K.; Sendhil Velan, S.; Kross, Brian; Popov, Vladimir; Smith, Mark F.; Weisenberger, Andrew G.; Zorn, Carl; Marano, Gary D.

2006-12-01

Multi-modality imaging is rapidly becoming a valuable tool in the diagnosis of disease and in the development of new drugs. Functional images produced with PET fused with anatomical structure images created by MRI will allow the correlation of form with function. Our group is developing a system to acquire MRI and PET images contemporaneously. The prototype device consists of two opposed detector heads, operating in coincidence mode. Each MRI-PET detector module consists of an array of LSO detector elements coupled through a long fibre optic light guide to a single Hamamatsu flat panel position-sensitive photomultiplier tube (PSPMT). The use of light guides allows the PSPMTs to be positioned outside the bore of a 3T MRI scanner where the magnetic field is relatively small. To test the device, simultaneous MRI and PET images of the brain of a male Sprague Dawley rat injected with FDG were successfully obtained. The images revealed no noticeable artefacts in either image set. Future work includes the construction of a full ring PET scanner, improved light guides and construction of a specialized MRI coil to permit higher quality MRI imaging.

MRI information for commonly used otologic implants: review and update.

PubMed

Azadarmaki, Roya; Tubbs, Rhonda; Chen, Douglas A; Shellock, Frank G

2014-04-01

To review information on magnetic resonance imaging (MRI) issues for commonly used otologic implants. Manufacturing companies, National Library of Medicine's online database, and an additional online database (www.MRIsafety.com). A literature review of the National Library of Medicine's online database with focus on MRI issues for otologic implants was performed. The MRI information on implants provided by manufacturers was reviewed. Baha and Ponto Pro osseointegrated implants' abutment and fixture and the implanted magnet of the Sophono Alpha 1 and 2 abutment-free systems are approved for 3-Tesla magnetic resonance (MR) systems. The external processors of these devices are MR Unsafe. Of the implants tested, middle ear ossicular prostheses, including stapes prostheses, except for the 1987 McGee prosthesis, are MR Conditional for 1.5-Tesla (and many are approved for 3-Tesla) MR systems. Cochlear implants with removable magnets are approved for patients undergoing MRI at 1.5 Tesla after magnet removal. The MED-EL PULSAR, SONATA, CONCERT, and CONCERT PIN cochlear implants can be used in patients undergoing MRI at 1.5 Tesla with application of a protective bandage. The MED-EL COMBI 40+ can be used in 0.2-Tesla MR systems. Implants made from nonmagnetic and nonconducting materials are MR Safe. Knowledge of MRI guidelines for commonly used otologic implants is important. Guidelines on MRI issues approved by the US Food and Drug Administration are not always the same compared with other parts of the world. This monograph provides a current reference for physicians on MRI issues for commonly used otologic implants.

Review of MRI positioning devices for guiding focused ultrasound systems.

PubMed

Yiallouras, C; Damianou, C

2015-06-01

This article contains a review of positioning devices that are currently used in the area of magnetic resonance imaging (MRI) guided focused ultrasound surgery (MRgFUS). The paper includes an extensive review of literature published since the first prototype system was invented in 1991. The technology has grown into a fast developing area with application to any organ accessible to ultrasound. The initial design operated using hydraulic principles, while the latest technology incorporates piezoelectric motors. Although, in the beginning there were fears regarding MRI safety, during recent years, the deployment of MR-safe positioning devices in FUS has become routine. Many of these positioning devices are now undergoing testing in clinical trials. Existing MRgFUS systems have been utilized mostly in oncology (fibroids, brain, liver, kidney, bone, pancreas, eye, thyroid, and prostate). It is anticipated that, in the near future, there will be a positioning device for every organ that is accessible by focused ultrasound. Copyright © 2014 John Wiley & Sons, Ltd.

Real-time Magnetic Resonance Imaging Guidance for Cardiovascular Procedures

PubMed Central

Horvath, Keith A.; Li, Ming; Mazilu, Dumitru; Guttman, Michael A.; McVeigh, Elliot R.

2008-01-01

Magnetic resonance imaging (MRI) of the cardiovascular system has proven to be an invaluable diagnostic tool. Given the ability to allow for real-time imaging, MRI guidance of intraoperative procedures can provide superb visualization which can facilitate a variety of interventions and minimize the trauma of the operations as well. In addition to the anatomic detail, MRI can provide intraoperative assessment of organ and device function. Instruments and devices can be marked to enhance visualization and tracking. All of which is an advance over standard x-ray or ultrasonic imaging. PMID:18395633

Mobile Device Applications for the Visualization of Functional Connectivity Networks and EEG Electrodes: iBraiN and iBraiNEEG

PubMed Central

Rojas, Gonzalo M.; Fuentes, Jorge A.; Gálvez, Marcelo

2016-01-01

Multiple functional MRI (fMRI)-based functional connectivity networks were obtained by Yeo et al. (2011), and the visualization of these complex networks is a difficult task. Also, the combination of functional connectivity networks determined by fMRI with electroencephalography (EEG) data could be a very useful tool. Mobile devices are becoming increasingly common among users, and for this reason, we describe here two applications for Android and iOS mobile devices: one that shows in an interactive way the seven Yeo functional connectivity networks, and another application that shows the relative position of 10–20 EEG electrodes with Yeo’s seven functional connectivity networks. PMID:27807416

Depletion-Mode GaN HEMT Q-Spoil Switches for MRI Coils

PubMed Central

Lu, Jonathan Y.; Grafendorfer, Thomas; Zhang, Tao; Vasanawala, Shreyas; Robb, Fraser; Pauly, John M.; Scott, Greig C.

2017-01-01

Q-spoiling is the process of decoupling an MRI receive coil to protect the equipment and patient. Conventionally, Q-spoiling is performed using a PIN diode switch that draws significant current. In this work, a Q-spoiling technique using a depletion-mode Gallium Nitride HEMT device was developed for coil detuning at both 1.5 T and 3 T MRI. The circuits with conventional PIN diode Q-spoiling and the GaN HEMT device were implemented on surface coils. SNR was measured and compared for all surfaces coils. At both 1.5 T and 3 T, comparable SNR was achieved for all coils with the proposed technique and conventional Q-spoiling. The GaN HEMT device has significantly reduced the required power for Q-spoiling. The GaN HEMT device also provides useful safety features by detuning the coil when unpowered. PMID:27362895

Thermo-Acoustic Ultrasound for Detection of RF-Induced Device Lead Heating in MRI.

PubMed

Dixit, Neerav; Stang, Pascal P; Pauly, John M; Scott, Greig C

2018-02-01

Patients who have implanted medical devices with long conductive leads are often restricted from receiving MRI scans due to the danger of RF-induced heating near the lead tips. Phantom studies have shown that this heating varies significantly on a case-by-case basis, indicating that many patients with implanted devices can receive clinically useful MRI scans without harm. However, the difficulty of predicting RF-induced lead tip heating prior to scanning prevents numerous implant recipients from being scanned. Here, we demonstrate that thermo-acoustic ultrasound (TAUS) has the potential to be utilized for a pre-scan procedure assessing the risk of RF-induced lead tip heating in MRI. A system was developed to detect TAUS signals by four different TAUS acquisition methods. We then integrated this system with an MRI scanner and detected a peak in RF power absorption near the tip of a model lead when transmitting from the scanner's body coil. We also developed and experimentally validated simulations to characterize the thermo-acoustic signal generated near lead tips. These results indicate that TAUS is a promising method for assessing RF implant safety, and with further development, a TAUS pre-scan could allow many more patients to have access to MRI scans of significant clinical value.

Clinical safety of an MRI conditional implantable cardioverter defibrillator system: A prospective Monocenter ICD-Magnetic resonance Imaging feasibility study (MIMI).

PubMed

Kypta, Alexander; Blessberger, Hermann; Hoenig, Simon; Saleh, Karim; Lambert, Thomas; Kammler, Juergen; Fellner, Franz; Lichtenauer, Michael; Steinwender, Clemens

2016-03-01

The aim of this study was to evaluate the safety and efficacy of the Lumax 740(®) Implantable Cardioverter Defibrillator (ICD) system in patients undergoing a defined 1.5 Tesla (T) MRI. Between November 2013 and April 2014, eighteen patients (age range, 41-78 years; mean age, 64 years) implanted with a Lumax 740(®) ICD system for at least 6 weeks before an MRI were enrolled into this single-center feasibility study. The local ethics committee approved the study before patients gave written informed consent. Patients underwent defined MRI 1.5T of the brain and lower lumbar spine with three safety follow-up evaluations obtained during the 3-month study period. Data were analyzed descriptively. Study endpoints were the absence of either MRI and pacing system related serious adverse device effects (SADE), or of a ventricular pacing threshold increase >0.5V, or of an R-wave amplitude attenuation < 50%, or of an R-wave amplitude < 5.0 mV at 1-month follow-up. The assessment of safety and efficacy was supported by recording of all adverse events, changes in pacing threshold, R-wave sensing, pacing impedances and in battery status. Sixteen patients completed the MRI and the follow-up period. As no SADE occurred, the SADE free rate was 100%. Freedom from ventricular pacing threshold increase was 100% (16/16; 95%CI: 82.9%; 100.0%). There were no significant differences between baseline and follow-up measurements of sensing amplitudes (-0.58 ± 2.07 mV, P = 0.239, -0.41 ± 1.04 mV, P = 0.133, and -0.25 ± 1.36 mV, P = 0.724, for immediately after, 1 month and 3 months after MRI scan, respectively) and pacing thresholds (-0.047 ± 0.18 V, P = 0.317, -0.019 ± 0.11 V, P = 0.490, and 0.075 ± 0.19 V, P = 0.070, for immediately after, 1 month and 3 months after MRI scan, respectively). Lead impedances after the MRI scan were significantly lower as compared with baseline values (-22.8 ± 21.69 Ω, P = 0.001, -21.62 ± 39.71 Ω, P = 0.040, and -33.68 ± 57.73 Ω, P = 0.018, for immediately after, 1 month and 3 months after MRI scan, respectively). MRI scans in patients with MRI conditional ICD system (Lumax 740(®) ) are feasible and can be performed safely under defined conditions in a hospital setting. © 2015 Wiley Periodicals, Inc.

A novel anthropomorphic flow phantom for the quantitative evaluation of prostate DCE-MRI acquisition techniques

NASA Astrophysics Data System (ADS)

Knight, Silvin P.; Browne, Jacinta E.; Meaney, James F.; Smith, David S.; Fagan, Andrew J.

2016-10-01

A novel anthropomorphic flow phantom device has been developed, which can be used for quantitatively assessing the ability of magnetic resonance imaging (MRI) scanners to accurately measure signal/concentration time-intensity curves (CTCs) associated with dynamic contrast-enhanced (DCE) MRI. Modelling of the complex pharmacokinetics of contrast agents as they perfuse through the tumour capillary network has shown great promise for cancer diagnosis and therapy monitoring. However, clinical adoption has been hindered by methodological problems, resulting in a lack of consensus regarding the most appropriate acquisition and modelling methodology to use and a consequent wide discrepancy in published data. A heretofore overlooked source of such discrepancy may arise from measurement errors of tumour CTCs deriving from the imaging pulse sequence itself, while the effects on the fidelity of CTC measurement of using rapidly-accelerated sequences such as parallel imaging and compressed sensing remain unknown. The present work aimed to investigate these features by developing a test device in which ‘ground truth’ CTCs were generated and presented to the MRI scanner for measurement, thereby allowing for an assessment of the DCE-MRI protocol to accurately measure this curve shape. The device comprised a four-pump flow system wherein CTCs derived from prior patient prostate data were produced in measurement chambers placed within the imaged volume. The ground truth was determined as the mean of repeat measurements using an MRI-independent, custom-built optical imaging system. In DCE-MRI experiments, significant discrepancies between the ground truth and measured CTCs were found for both tumorous and healthy tissue-mimicking curve shapes. Pharmacokinetic modelling revealed errors in measured K trans, v e and k ep values of up to 42%, 31%, and 50% respectively, following a simple variation of the parallel imaging factor and number of signal averages in the acquisition protocol. The device allows for the quantitative assessment and standardisation of DCE-MRI protocols (both existing and emerging).

Objective assessment of olfactory function using functional magnetic resonance imaging.

PubMed

Toledano, Adolfo; Borromeo, Susana; Luna, Guillermo; Molina, Elena; Solana, Ana Beatriz; García-Polo, Pablo; Hernández, Juan Antonio; Álvarez-linera, Juan

2012-01-01

To show the results of a device that generates automated olfactory stimuli suitable for functional magnetic resonance imaging (fMRI) experiments. Ten normal volunteers, 5 women and 5 men, were studied. The system allows the programming of several sequences, providing the capability to synchronise the onset of odour presentation with acquisition by a trigger signal of the MRI scanner. The olfactometer is a device that allows selection of the odour, the event paradigm, the time of stimuli and the odour concentration. The paradigm used during fMRI scanning consisted of 15-s blocks. The odorant event took 2s with butanol, mint and coffee. We observed olfactory activity in the olfactory bulb, entorhinal cortex (4%), amygdala (2.5%) and temporo-parietal cortex, especially in the areas related to emotional integration. The device has demonstrated its effectiveness in stimulating olfactory areas and its capacity to adapt to fMRI equipment. Copyright © 2010 Elsevier España, S.L. All rights reserved.

3D conformal MRI-controlled transurethral ultrasound prostate therapy: validation of numerical simulations and demonstration in tissue-mimicking gel phantoms.

PubMed

Burtnyk, Mathieu; N'Djin, William Apoutou; Kobelevskiy, Ilya; Bronskill, Michael; Chopra, Rajiv

2010-11-21

MRI-controlled transurethral ultrasound therapy uses a linear array of transducer elements and active temperature feedback to create volumes of thermal coagulation shaped to predefined prostate geometries in 3D. The specific aims of this work were to demonstrate the accuracy and repeatability of producing large volumes of thermal coagulation (>10 cc) that conform to 3D human prostate shapes in a tissue-mimicking gel phantom, and to evaluate quantitatively the accuracy with which numerical simulations predict these 3D heating volumes under carefully controlled conditions. Eleven conformal 3D experiments were performed in a tissue-mimicking phantom within a 1.5T MR imager to obtain non-invasive temperature measurements during heating. Temperature feedback was used to control the rotation rate and ultrasound power of transurethral devices with up to five 3.5 × 5 mm active transducer elements. Heating patterns shaped to human prostate geometries were generated using devices operating at 4.7 or 8.0 MHz with surface acoustic intensities of up to 10 W cm(-2). Simulations were informed by transducer surface velocity measurements acquired with a scanning laser vibrometer enabling improved calculations of the acoustic pressure distribution in a gel phantom. Temperature dynamics were determined according to a FDTD solution to Pennes' BHTE. The 3D heating patterns produced in vitro were shaped very accurately to the prostate target volumes, within the spatial resolution of the MRI thermometry images. The volume of the treatment difference falling outside ± 1 mm of the target boundary was, on average, 0.21 cc or 1.5% of the prostate volume. The numerical simulations predicted the extent and shape of the coagulation boundary produced in gel to within (mean ± stdev [min, max]): 0.5 ± 0.4 [-1.0, 2.1] and -0.05 ± 0.4 [-1.2, 1.4] mm for the treatments at 4.7 and 8.0 MHz, respectively. The temperatures across all MRI thermometry images were predicted within -0.3 ± 1.6 °C and 0.1 ± 0.6 °C, inside and outside the prostate respectively, and the treatment time to within 6.8 min. The simulations also showed excellent agreement in regions of sharp temperature gradients near the transurethral and endorectal cooling devices. Conformal 3D volumes of thermal coagulation can be precisely matched to prostate shapes with transurethral ultrasound devices and active MRI temperature feedback. The accuracy of numerical simulations for MRI-controlled transurethral ultrasound prostate therapy was validated experimentally, reinforcing their utility as an effective treatment planning tool.

Occupational exposure to electromagnetic fields from medical sources

PubMed Central

STAM, Rianne; YAMAGUCHI-SEKINO, Sachiko

2017-01-01

High exposures to electromagnetic fields (EMF) can occur near certain medical devices in the hospital environment. A systematic assessment of medical occupational EMF exposure could help to clarify where more attention to occupational safety may be needed. This paper seeks to identify sources of high exposure for hospital workers and compare the published exposure data to occupational limits in the European Union. A systematic search for peer-reviewed publications was conducted via PubMed and Scopus databases. Relevant grey literature was collected via a web search. For each publication, the highest measured magnetic flux density or internal electric field strength per device and main frequency component was extracted. For low frequency fields, high action levels may be exceeded for magnetic stimulation, MRI gradient fields and movement in MRI static fields. For radiofrequency fields, the action levels may be exceeded near devices for diathermy, electrosurgery and hyperthermia and in the radiofrequency field inside MRI scanners. The exposure limit values for internal electric field may be exceeded for MRI and magnetic stimulation. For MRI and magnetic stimulation, practical measures can limit worker exposure. For diathermy, electrosurgery and hyperthermia, additional calculations are necessary to determine if SAR limits may be exceeded in some scenarios. PMID:29109357

Metallic artifact in MRI after removal of orthopedic implants.

PubMed

Bagheri, Mohammad Hadi; Hosseini, Mehrdad Mohammad; Emami, Mohammad Jafar; Foroughi, Amin Aiboulhassani

2012-03-01

The aim of the present study was to evaluate the metallic artifacts in MRI of the orthopedic patients after removal of metallic implants. From March to August 2009, 40 orthopedic patients operated for removal of orthopedic metallic implants were studied by post-operative MRI from the site of removal of implants. A grading scale of 0-3 was assigned for artifact in MR images whereby 0 was considered no artifact; and I-III were considered mild, moderate, and severe metallic artifacts, respectively. These grading records were correlated with other variables including the type, size, number, and composition of metallic devices; and the site and duration of orthopedic devices stay in the body. Metallic susceptibly artifacts were detected in MRI of 18 of 40 cases (45%). Screws and pins in removed hardware were the most important factors for causing artifacts in MRI. The artifacts were found more frequently in the patients who had more screws and pins in the removed implants. Gender, age, site of implantation of the device, length of the hardware, composition of the metallic implants (stainless steel versus titanium), and duration of implantation of the hardware exerted no effect in producing metallic artifacts after removal of implants. Short TE sequences of MRI (such as T1 weighted) showed fewer artifacts. Susceptibility of metallic artifacts is a frequent phenomenon in MRI of patients upon removal of metallic orthopedic implants. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Magnetic resonance imaging after anterior cruciate ligament reconstruction: A practical guide

PubMed Central

Grassi, Alberto; Bailey, James R; Signorelli, Cecilia; Carbone, Giuseppe; Tchonang Wakam, Andy; Lucidi, Gian Andrea; Zaffagnini, Stefano

2016-01-01

Anterior cruciate ligament (ACL) reconstruction is one of the most common orthopedic procedures performed worldwide. In this regard, magnetic resonance imaging (MRI) represents a useful pre-operative tool to confirm a disruption of the ACL and to assess for potential associated injuries. However, MRI is also valuable post-operatively, as it is able to identify, in a non-invasive way, a number of aspects and situations that could suggest potential problems to clinicians. Graft signal and integrity, correct tunnel placement, tunnel widening, and problems with fixation devices or the donor site could all compromise the surgical outcomes and potentially predict the failure of the ACL reconstruction. Furthermore, several anatomical features of the knee could be associated to worst outcomes or higher risk of failure. This review provides a practical guide for the clinician to evaluate the post-surgical ACL through MRI, and to analyze all the parameters and features directly or indirectly related to ACL reconstruction, in order to assess for normal or pathologic conditions. PMID:27795945

Haptic fMRI: combining functional neuroimaging with haptics for studying the brain's motor control representation.

PubMed

Menon, Samir; Brantner, Gerald; Aholt, Chris; Kay, Kendrick; Khatib, Oussama

2013-01-01

A challenging problem in motor control neuroimaging studies is the inability to perform complex human motor tasks given the Magnetic Resonance Imaging (MRI) scanner's disruptive magnetic fields and confined workspace. In this paper, we propose a novel experimental platform that combines Functional MRI (fMRI) neuroimaging, haptic virtual simulation environments, and an fMRI-compatible haptic device for real-time haptic interaction across the scanner workspace (above torso ∼ .65×.40×.20m(3)). We implement this Haptic fMRI platform with a novel haptic device, the Haptic fMRI Interface (HFI), and demonstrate its suitability for motor neuroimaging studies. HFI has three degrees-of-freedom (DOF), uses electromagnetic motors to enable high-fidelity haptic rendering (>350Hz), integrates radio frequency (RF) shields to prevent electromagnetic interference with fMRI (temporal SNR >100), and is kinematically designed to minimize currents induced by the MRI scanner's magnetic field during motor displacement (<2cm). HFI possesses uniform inertial and force transmission properties across the workspace, and has low friction (.05-.30N). HFI's RF noise levels, in addition, are within a 3 Tesla fMRI scanner's baseline noise variation (∼.85±.1%). Finally, HFI is haptically transparent and does not interfere with human motor tasks (tested for .4m reaches). By allowing fMRI experiments involving complex three-dimensional manipulation with haptic interaction, Haptic fMRI enables-for the first time-non-invasive neuroscience experiments involving interactive motor tasks, object manipulation, tactile perception, and visuo-motor integration.

An eight-year prospective controlled study about the safety and diagnostic value of cardiac and non-cardiac 1.5-T MRI in patients with a conventional pacemaker or a conventional implantable cardioverter defibrillator.

PubMed

Lupo, Pierpaolo; Cappato, Riccardo; Di Leo, Giovanni; Secchi, Francesco; Papini, Giacomo D E; Foresti, Sara; Ali, Hussam; De Ambroggi, Guido M G; Sorgente, Antonio; Epicoco, Gianluca; Cannaò, Paola M; Sardanelli, Francesco

2018-06-01

To investigate safety and diagnostic value of 1.5-T MRI in carriers of conventional pacemaker (cPM) or conventional implantable defibrillator (cICD). We prospectively compared cPM/cICD-carriers undergoing MRI (study group, SG), excluding those device-dependent or implanted <6 weeks before enrolment or prior to 01/01/2000, with cPM/cICD-carriers undergoing chest x-ray, CT or follow-up (reference group, RG). 142 MRI (55 cardiac) were performed in 120 patients with cPM (n=71) or cICD (n=71). In the RG 98 measurements were performed in 95 patients with cPM (n=40) or cICD (n=58). No adverse events were observed. No MRI prolonged/interrupted. All cPM/cICD were correctly reprogrammed after MRI without malfunctions. One temporary communication failure was observed in one cPM-carrier. Immediately after MRI, 12/14 device interrogation parameters did not change significantly (clinically negligible changes of battery voltage and cICD charging time), without significant variations for SG versus RG. Three-12 months after MRI, 9/11 device interrogation parameters did not change significantly (clinically negligible changes of battery impedance/voltage). Non-significant changes of three markers of myocardial necrosis. Non-cardiac MRI: 82/87 diagnostic without artefacts; 4/87 diagnostic with artefacts; 1/87 partially diagnostic. Cardiac MRI: in cPM-carriers, 14/15 diagnostic with artefacts, 1/15 partially diagnostic; in cICD-carriers, 9/40 diagnostic with artefacts, 22 partially diagnostic, nine non-diagnostic. A favourable risk-benefit ratio of 1.5-T MRI in cPM/cICD carriers was reported. • Cooperation between radiologists and cardiac electrophysiologists allowed safe 1.5-T MRI in cPM/cICD-carriers. • No adverse events for 142 MRI in 71 cPM-carriers and 71 cICD-carriers. • Ninety-nine per cent (86/87) of non-cardiac MRI in cPM/cICD-carriers were diagnostic. • All cPM-carrier cardiac MRIs had artefacts, 14 examinations diagnostic, 1 partially diagnostic. • Twenty-three per cent (9/40) of cardiac MRI in cICD-carriers were non-diagnostic.

Mechanical Validation of an MRI Compatible Stereotactic Neurosurgery Robot in Preparation for Pre-Clinical Trials.

PubMed

Nycz, Christopher J; Gondokaryono, Radian; Carvalho, Paulo; Patel, Nirav; Wartenberg, Marek; Pilitsis, Julie G; Fischer, Gregory S

2017-09-01

The use of magnetic resonance imaging (MRI) for guiding robotic surgical devices has shown great potential for performing precisely targeted and controlled interventions. To fully realize these benefits, devices must work safely within the tight confines of the MRI bore without negatively impacting image quality. Here we expand on previous work exploring MRI guided robots for neural interventions by presenting the mechanical design and assessment of a device for positioning, orienting, and inserting an interstitial ultrasound-based ablation probe. From our previous work we have added a 2 degree of freedom (DOF) needle driver for use with the aforementioned probe, revised the mechanical design to improve strength and function, and performed an evaluation of the mechanism's accuracy and effect on MR image quality. The result of this work is a 7-DOF MRI robot capable of positioning a needle tip and orienting it's axis with accuracy of 1.37 ± 0.06 mm and 0.79° ± 0.41°, inserting it along it's axis with an accuracy of 0.06 ± 0.07 mm , and rotating it about it's axis to an accuracy of 0.77° ± 1.31°. This was accomplished with no significant reduction in SNR caused by the robot's presence in the MRI bore, ≤ 10.3% reduction in SNR from running the robot's motors during a scan, and no visible paramagnetic artifacts.

First patients treated with a 1.5 T MRI-Linac: clinical proof of concept of a high-precision, high-field MRI guided radiotherapy treatment

NASA Astrophysics Data System (ADS)

Raaymakers, B. W.; Jürgenliemk-Schulz, I. M.; Bol, G. H.; Glitzner, M.; Kotte, A. N. T. J.; van Asselen, B.; de Boer, J. C. J.; Bluemink, J. J.; Hackett, S. L.; Moerland, M. A.; Woodings, S. J.; Wolthaus, J. W. H.; van Zijp, H. M.; Philippens, M. E. P.; Tijssen, R.; Kok, J. G. M.; de Groot-van Breugel, E. N.; Kiekebosch, I.; Meijers, L. T. C.; Nomden, C. N.; Sikkes, G. G.; Doornaert, P. A. H.; Eppinga, W. S. C.; Kasperts, N.; Kerkmeijer, L. G. W.; Tersteeg, J. H. A.; Brown, K. J.; Pais, B.; Woodhead, P.; Lagendijk, J. J. W.

2017-12-01

The integration of 1.5 T MRI functionality with a radiotherapy linear accelerator (linac) has been pursued since 1999 by the UMC Utrecht in close collaboration with Elekta and Philips. The idea behind this integrated device is to offer unrivalled, online and real-time, soft-tissue visualization of the tumour and the surroundings for more precise radiation delivery. The proof of concept of this device was given in 2009 by demonstrating simultaneous irradiation and MR imaging on phantoms, since then the device has been further developed and commercialized by Elekta. The aim of this work is to demonstrate the clinical feasibility of online, high-precision, high-field MRI guidance of radiotherapy using the first clinical prototype MRI-Linac. Four patients with lumbar spine bone metastases were treated with a 3 or 5 beam step-and-shoot IMRT plan. The IMRT plan was created while the patient was on the treatment table and based on the online 1.5 T MR images; pre-treatment CT was deformably registered to the online MRI to obtain Hounsfield values. Bone metastases were chosen as the first site as these tumors can be clearly visualized on MRI and the surrounding spine bone can be detected on the integrated portal imager. This way the portal images served as an independent verification of the MRI based guidance to quantify the geometric precision of radiation delivery. Dosimetric accuracy was assessed post-treatment from phantom measurements with an ionization chamber and film. Absolute doses were found to be highly accurate, with deviations ranging from 0.0% to 1.7% in the isocenter. The geometrical, MRI based targeting as confirmed using portal images was better than 0.5 mm, ranging from 0.2 mm to 0.4 mm. In conclusion, high precision, high-field, 1.5 T MRI guided radiotherapy is clinically feasible.

Knee MRI

MedlinePlus

... magnetic field of the MRI unit, metal and electronic items are not allowed in the exam room. ... tell the technologist if you have medical or electronic devices in your body. These objects may interfere ...

Shoulder MRI

MedlinePlus

... magnetic field of the MRI unit, metal and electronic items are not allowed in the exam room. ... tell the technologist if you have medical or electronic devices in your body. These objects may interfere ...

Magnetic Particle / Magnetic Resonance Imaging: In-Vitro MPI-Guided Real Time Catheter Tracking and 4D Angioplasty Using a Road Map and Blood Pool Tracer Approach.

PubMed

Salamon, Johannes; Hofmann, Martin; Jung, Caroline; Kaul, Michael Gerhard; Werner, Franziska; Them, Kolja; Reimer, Rudolph; Nielsen, Peter; Vom Scheidt, Annika; Adam, Gerhard; Knopp, Tobias; Ittrich, Harald

2016-01-01

In-vitro evaluation of the feasibility of 4D real time tracking of endovascular devices and stenosis treatment with a magnetic particle imaging (MPI) / magnetic resonance imaging (MRI) road map approach and an MPI-guided approach using a blood pool tracer. A guide wire and angioplasty-catheter were labeled with a thin layer of magnetic lacquer. For real time MPI a custom made software framework was developed. A stenotic vessel phantom filled with saline or superparamagnetic iron oxide nanoparticles (MM4) was equipped with bimodal fiducial markers for co-registration in preclinical 7T MRI and MPI. In-vitro angioplasty was performed inflating the balloon with saline or MM4. MPI data were acquired using a field of view of 37.3×37.3×18.6 mm3 and a frame rate of 46 volumes/sec. Analysis of the magnetic lacquer-marks on the devices were performed with electron microscopy, atomic absorption spectrometry and micro-computed tomography. Magnetic marks allowed for MPI/MRI guidance of interventional devices. Bimodal fiducial markers enable MPI/MRI image fusion for MRI based roadmapping. MRI roadmapping and the blood pool tracer approach facilitate MPI real time monitoring of in-vitro angioplasty. Successful angioplasty was verified with MPI and MRI. Magnetic marks consist of micrometer sized ferromagnetic plates mainly composed of iron and iron oxide. 4D real time MP imaging, tracking and guiding of endovascular instruments and in-vitro angioplasty is feasible. In addition to an approach that requires a blood pool tracer, MRI based roadmapping might emerge as a promising tool for radiation free 4D MPI-guided interventions.

Magnetic resonance imaging in patients with cardiac implanted electronic devices: focus on contraindications to magnetic resonance imaging protocols.

PubMed

Horwood, Laura; Attili, Anil; Luba, Frank; Ibrahim, El-Sayed H; Parmar, Hemant; Stojanovska, Jadranka; Gadoth-Goodman, Sharon; Fette, Carey; Oral, Hakan; Bogun, Frank

2017-05-01

Magnetic resonance imaging (MRI) has been reported to be safe in patients with cardiac implantable electronic devices (CIED) provided a specific protocol is followed. The objective of this study was to assess whether this is also true for patients excluded from published protocols. A total of 160 MRIs were obtained in 142 consecutive patients with CIEDs [106 patients had an implantable cardioverter defibrillator (ICD) and 36 had a pacemaker implanted] using an adapted, pre-specified protocol. A cardiac MRI was performed in 95 patients, and a spinal/brain MRI was performed in 47 patients. Forty-six patients (32%) had either abandoned leads (n = 10), and/or were pacemaker dependent with an implanted ICD (n = 19), had recently implanted CIEDs (n = 1), and/or had a CIED device with battery depletion (n = 2), and/or a component of the CIED was recalled or on advisory (n = 32). No major complications occurred. Some device parameters changed slightly, but significantly, right after or at 1-week post-MRI without requiring any reprogramming. In one patient with an ICD on advisory, the pacing rate changed inexplicably during one of his two MRIs from 90 to 50 b.p.m. Using a pre-specified protocol, cardiac and non-cardiac MRIs were performed in CIED patients with pacemaker dependency, abandoned leads, or depleted batteries without occurrence of major adverse events. Patients with devices on advisory need to be monitored carefully during MRI, especially if they are pacemaker dependent. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

Influence of geometric and material properties on artifacts generated by interventional MRI devices: Relevance to PRF-shift thermometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tatebe, Ken, E-mail: Ken.Tatebe@gmail.com; Ramsay, Elizabeth; Kazem, Mohammad

2016-01-15

Purpose: Magnetic resonance imaging (MRI) is capable of providing valuable real-time feedback during medical procedures, partly due to the excellent soft-tissue contrast available. Several technical hurdles still exist to seamless integration of medical devices with MRI due to incompatibility of most conventional devices with this imaging modality. In this study, the effect of local perturbations in the magnetic field caused by the magnetization of medical devices was examined using finite element analysis modeling. As an example, the influence of the geometric and material characteristics of a transurethral high-intensity ultrasound applicator on temperature measurements using proton resonance frequency (PRF)-shift thermometry wasmore » investigated. Methods: The effect of local perturbations in the magnetic field, caused by the magnetization of medical device components, was examined using finite element analysis modeling. The thermometry artifact generated by a transurethral ultrasound applicator was simulated, and these results were validated against analytic models and scans of an applicator in a phantom. Several parameters were then varied to identify which most strongly impacted the level of simulated thermometry artifact, which varies as the applicator moves over the course of an ablative high-intensity ultrasound treatment. Results: Key design parameters identified as having a strong influence on the magnitude of thermometry artifact included the susceptibility of materials and their volume. The location of components was also important, particularly when positioned to maximize symmetry of the device. Finally, the location of component edges and the inclination of the device relative to the magnetic field were also found to be important factors. Conclusions: Previous design strategies to minimize thermometry artifact were validated, and novel design strategies were identified that substantially reduce PRF-shift thermometry artifacts for a variety of device orientations. These new strategies are being incorporated into the next generation of applicators. The general strategy described in this study can be applied to the design of other interventional devices intended for use with MRI.« less

Magnetic Resonance Mediated Radiofrequency Ablation.

PubMed

Hue, Yik-Kiong; Guimaraes, Alexander R; Cohen, Ouri; Nevo, Erez; Roth, Abraham; Ackerman, Jerome L

2018-02-01

To introduce magnetic resonance mediated radiofrequency ablation (MR-RFA), in which the MRI scanner uniquely serves both diagnostic and therapeutic roles. In MR-RFA scanner-induced RF heating is channeled to the ablation site via a Larmor frequency RF pickup device and needle system, and controlled via the pulse sequence. MR-RFA was evaluated with simulation of electric and magnetic fields to predict the increase in local specific-absorption-rate (SAR). Temperature-time profiles were measured for different configurations of the device in agar phantoms and ex vivo bovine liver in a 1.5 T scanner. Temperature rise in MR-RFA was imaged using the proton resonance frequency method validated with fiber-optic thermometry. MR-RFA was performed on the livers of two healthy live pigs. Simulations indicated a near tenfold increase in SAR at the RFA needle tip. Temperature-time profiles depended significantly on the physical parameters of the device although both configurations tested yielded temperature increases sufficient for ablation. Resected livers from live ablations exhibited clear thermal lesions. MR-RFA holds potential for integrating RF ablation tumor therapy with MRI scanning. MR-RFA may add value to MRI with the addition of a potentially disposable ablation device, while retaining MRI's ability to provide real time procedure guidance and measurement of tissue temperature, perfusion, and coagulation.

Ultra-high magnetic resonance imaging (MRI): a potential examination for deep brain stimulation devices and the limitation study concerning MRI-related heating injury.

PubMed

Chen, Ying-Chuan; Li, Jun-Ju; Zhu, Guan-Yu; Shi, Lin; Yang, An-Chao; Jiang, Yin; Zhang, Xin; Zhang, Jian-Guo

2017-03-01

Nowadays, the patients with deep brain stimulation (DBS) devices are restricted to undertake 1.5T magnetic resonance imaging (MRI) according to the guideline. Nevertheless, we conducted an experiment to test pathological change near the leads in different field-strength MRI. Twenty-four male New Zealand rabbits were assigned to Group 1 (G1, n = 6, 7.0T, DBS), Group 2 (G2, n = 6, 3.0T, DBS), Group 3 (G3, n = 6, 1.5T, DBS), and Group 4 (G4, n = 6, 1.5T, paracentesis). DBS leads were implanted in G1, G2 and G3, targeting left nucleus ventralis posterior thalami. Paracentesis was performed in G4. 24 h after MRI scan, all animals were killed for examining pathological alternation (at different distance from lead) via transmission electron microscopy. Our results suggest that the severity of tissue injury correlates with the distance to electrode instead of field strength of MRI. Up to now, the reason for the restriction of MRI indicated no significantly different pathological change.

MRI of the Breast

MedlinePlus

... magnetic field of the MRI unit, metal and electronic items are not allowed in the exam room. ... tell the technologist if you have medical or electronic devices in your body. These objects may interfere ...

Magnetic resonance-guided motorized transcranial ultrasound system for blood-brain barrier permeabilization along arbitrary trajectories in rodents.

PubMed

Magnin, Rémi; Rabusseau, Fabien; Salabartan, Frédéric; Mériaux, Sébastien; Aubry, Jean-François; Le Bihan, Denis; Dumont, Erik; Larrat, Benoit

2015-01-01

Focused ultrasound combined with microbubble injection is capable of locally and transiently enhancing the permeability of the blood-brain barrier (BBB). Magnetic resonance imaging (MRI) guidance enables to plan, monitor, and characterize the BBB disruption. Being able to precisely and remotely control the permeabilization location is of great interest to perform reproducible drug delivery protocols. In this study, we developed an MR-guided motorized focused ultrasound (FUS) system allowing the transducer displacement within preclinical MRI scanners, coupled with real-time transfer and reconstruction of MRI images, to help ultrasound guidance. Capabilities of this new device to deliver large molecules to the brain on either single locations or along arbitrary trajectories were characterized in vivo on healthy rats and mice using 1.5 MHz ultrasound sonications combined with microbubble injection. The efficacy of BBB permeabilization was assessed by injecting a gadolinium-based MR contrast agent that does not cross the intact BBB. The compact motorized FUS system developed in this work fits into the 9-cm inner diameter of the gradient insert installed on our 7-T preclinical MRI scanners. MR images acquired after contrast agent injection confirmed that this device can be used to enhance BBB permeability along remotely controlled spatial trajectories of the FUS beam in both rats and mice. The two-axis motor stage enables reaching any region of interest in the rodent brain. The positioning error when targeting the same anatomical location on different animals was estimated to be smaller than 0.5 mm. Finally, this device was demonstrated to be useful for testing BBB opening at various acoustic pressures (0.2, 0.4, 0.7, and 0.9 MPa) in the same animal and during one single ultrasound session. Our system offers the unique possibility to move the transducer within a high magnetic field preclinical MRI scanner, thus enabling the delivery of large molecules to virtually any rodent brain area in a non-invasive manner. It results in time-saving and reproducibility and could be used to either deliver drugs over large parts of the brain or test different acoustic conditions on the same animal during the same session, therefore reducing physiological variability.

Magnetic Resonance Imaging (MRI) - Spine

MedlinePlus

... magnetic field of the MRI unit, metal and electronic items are not allowed in the exam room. ... tell the technologist if you have medical or electronic devices in your body. These objects may interfere ...

MRI of the Musculoskeletal System

MedlinePlus

... magnetic field of the MRI unit, metal and electronic items are not allowed in the exam room. ... tell the technologist if you have medical or electronic devices in your body. These objects may interfere ...

Plasma MRI Experiments at UW-Madison

NASA Astrophysics Data System (ADS)

Flanagan, K.; Clark, M.; Desangles, V.; Siller, R.; Wallace, J.; Weisberg, D.; Forest, C. B.

2015-11-01

Experiments for driving Keplerian-like flow profiles on both the Plasma Couette Experiment Upgrade (PCX-U) and the Wisconsin Plasma Astrophysics Laboratory (WiPAL) user facility are described. Instead of driving flow at the boundaries, as is typical in many liquid metal Couette experiments, a global drive is implemented. A large radial current is drawn across a small axial field generating torque across the whole profile. This global electrically driven flow is capable of producing profiles similar to Keplerian flow. PCX-U has been purposely constructed for MRI experiments, while similar experiments on the WiPAL device show the versatility of the user facility and provide a larger plasma volume. Numerical calculations show the predicted parameter spaces for exciting the MRI in these plasmas and the equilibrium flow profiles expected. In both devices, relevant MRI parameters appear to be within reach of typical operating characteristics.

Mechanical Validation of an MRI Compatible Stereotactic Neurosurgery Robot in Preparation for Pre-Clinical Trials

PubMed Central

Nycz, Christopher J; Gondokaryono, Radian; Carvalho, Paulo; Patel, Nirav; Wartenberg, Marek; Pilitsis, Julie G; Fischer, Gregory S

2018-01-01

The use of magnetic resonance imaging (MRI) for guiding robotic surgical devices has shown great potential for performing precisely targeted and controlled interventions. To fully realize these benefits, devices must work safely within the tight confines of the MRI bore without negatively impacting image quality. Here we expand on previous work exploring MRI guided robots for neural interventions by presenting the mechanical design and assessment of a device for positioning, orienting, and inserting an interstitial ultrasound-based ablation probe. From our previous work we have added a 2 degree of freedom (DOF) needle driver for use with the aforementioned probe, revised the mechanical design to improve strength and function, and performed an evaluation of the mechanism’s accuracy and effect on MR image quality. The result of this work is a 7-DOF MRI robot capable of positioning a needle tip and orienting it’s axis with accuracy of 1.37 ± 0.06mm and 0.79° ± 0.41°, inserting it along it’s axis with an accuracy of 0.06 ± 0.07mm, and rotating it about it’s axis to an accuracy of 0.77° ± 1.31°. This was accomplished with no significant reduction in SNR caused by the robot’s presence in the MRI bore, ≤ 10.3% reduction in SNR from running the robot’s motors during a scan, and no visible paramagnetic artifacts. PMID:29696097

Catheter tracking using continuous radial MRI.

PubMed

Rasche, V; Holz, D; Köhler, J; Proksa, R; Röschmann, P

1997-06-01

The guidance of minimally invasive procedures may become a very important future application of MRI. The guidance of interventions requires images of the anatomy as well as the information of the position of invasive devices used. This paper introduces continuous radial MRI for the simultaneous acquisition of the anatomic MR image and the position of one or more small RF-coils (mu-coils), which can be mounted on invasive devices such as catheters or biopsy needles. This approach allows the in-plane tracking of an invasive device without any prolongation of the overall acquisition time. The extension to three-dimensional position tracking is described. Phantom studies are presented demonstrating the capability of this technique for real-time automatic adjustment of the slice position to the current catheter position with a temporal resolution of 100 ms. Simultaneously the in-plane catheter position is depicted in the actually acquired MR image during continuous scanning.

A Magnetic Resonance Compatible Soft Wearable Robotic Glove for Hand Rehabilitation and Brain Imaging.

PubMed

Hong Kai Yap; Kamaldin, Nazir; Jeong Hoon Lim; Nasrallah, Fatima A; Goh, James Cho Hong; Chen-Hua Yeow

2017-06-01

In this paper, we present the design, fabrication and evaluation of a soft wearable robotic glove, which can be used with functional Magnetic Resonance imaging (fMRI) during the hand rehabilitation and task specific training. The soft wearable robotic glove, called MR-Glove, consists of two major components: a) a set of soft pneumatic actuators and b) a glove. The soft pneumatic actuators, which are made of silicone elastomers, generate bending motion and actuate finger joints upon pressurization. The device is MR-compatible as it contains no ferromagnetic materials and operates pneumatically. Our results show that the device did not cause artifacts to fMRI images during hand rehabilitation and task-specific exercises. This study demonstrated the possibility of using fMRI and MR-compatible soft wearable robotic device to study brain activities and motor performances during hand rehabilitation, and to unravel the functional effects of rehabilitation robotics on brain stimulation.

Network analysis of EEG related functional MRI changes due to medication withdrawal in focal epilepsy

PubMed Central

Hermans, Kees; Ossenblok, Pauly; van Houdt, Petra; Geerts, Liesbeth; Verdaasdonk, Rudolf; Boon, Paul; Colon, Albert; de Munck, Jan C.

2015-01-01

Anti-epileptic drugs (AEDs) have a global effect on the neurophysiology of the brain which is most likely reflected in functional brain activity recorded with EEG and fMRI. These effects may cause substantial inter-subject variability in studies where EEG correlated functional MRI (EEG–fMRI) is used to determine the epileptogenic zone in patients who are candidate for epilepsy surgery. In the present study the effects on resting state fMRI are quantified in conditions with AED administration and after withdrawal of AEDs. EEG–fMRI data were obtained from 10 patients in the condition that the patient was on the steady-state maintenance doses of AEDs as prescribed (condition A) and after withdrawal of AEDs (condition B), at the end of a clinically standard pre-surgical long term video-EEG monitoring session. Resting state networks (RSN) were extracted from fMRI. The epileptic component (ICE) was identified by selecting the RSN component with the largest overlap with the EEG–fMRI correlation pattern. Changes in RSN functional connectivity between conditions A and B were quantified. EEG–fMRI correlation analysis was successful in 30% and 100% of the cases in conditions A and B, respectively. Spatial patterns of ICEs are comparable in conditions A and B, except for one patient for whom it was not possible to identify the ICE in condition A. However, the resting state functional connectivity is significantly increased in the condition after withdrawal of AEDs (condition B), which makes resting state fMRI potentially a new tool to study AED effects. The difference in sensitivity of EEG–fMRI in conditions A and B, which is not related to the number of epileptic EEG events occurring during scanning, could be related to the increased functional connectivity in condition B. PMID:26137444

SU-F-I-15: Evaluation of a New MR-Compatible Respiratory Motion Device at 3T

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soliman, A; Sunnybrook Health Sciences Centre, Toronto, ON; Chugh, B

Purpose: Recent advances in MRI-guided radiotherapy has inspired the development of MRI-compatible motion devices that simulate patient periodic motion in the scanner, particularly respiratory motion. Most commercial devices rely on non MR-safe ferromagnetic stepper motors which are not practical for regular QA testing. This work evaluates the motion performance of a new fully MRI compatible respiratory motion device at 3T. Methods: The QUASAR™ MRI-compatible respiratory motion phantom has been recently developed by Modus QA Inc., London, ON, Canada. The prototype is constructed from diamagnetic materials with linear motion generated using MRI-compatible piezoelectric motors that can be safely inserted in themore » scanner bore. The tumor was represented by a fillable sphere and is attached to the linear motion generator. The spherical tumor-representative and its surroundings were filled with different concentrations of MnCl2 to produce realistic relaxation times. The motion was generated along the longitudinal (H/F) axis of the bore using sinusoidal reference waveform (amplitude = 15 mm, frequency 0.25 Hz). Imaging was then performed on 3T Philips Achieva using a 32-channel cardiac coil. Fast 2D spoiled gradient-echo was used with a spatial resolution of 1.8 × 1.8 mm{sup 2} and slice thickness of 4 mm. The motion waveform was then measured on the resultant image series by tracking the centroid of the sphere through the time series. This image-derived measured motion was compared to the software-generated reference waveform. Results: No visible distortions from the device were observed on the images. Excellent agreement between the measured and the reference waveforms were obtained. Negligible motion was observed in the lateral (R/L) direction. Conclusion: Our investigation demonstrates that this piezo-electric motor design is effective at simulating periodic motion and is a potential candidate for MRI-radiotherapy respiratory motion simulation. Future work should focus on evaluating non-sinusoidal waveforms, fast 3D pulse sequences, and perform dosimetric QA.« less

Magnetic resonance imaging safety in pacemaker and implantable cardioverter defibrillator patients: how far have we come?

PubMed Central

Nordbeck, Peter; Ertl, Georg; Ritter, Oliver

2015-01-01

Magnetic resonance imaging (MRI) has long been regarded a general contraindication in patients with cardiovascular implanted electronic devices such as cardiac pacemakers or cardioverter defibrillators (ICDs) due to the risk of severe complications and even deaths caused by interactions of the magnetic resonance (MR) surrounding and the electric devices. Over the last decade, a better understanding of the underlying mechanisms responsible for such potentially life-threatening complications as well as technical advances have allowed an increasing number of pacemaker and ICD patients to safely undergo MRI. This review lists the key findings from basic research and clinical trials over the last 20 years, and discusses the impact on current day clinical practice. With ‘MR-conditional’ devices being the new standard of care, MRI in pacemaker and ICD patients has been adopted to clinical routine today. However, specific precautions and specifications of these devices should be carefully followed if possible, to avoid patient risks which might appear with new MR technology and further increasing indications and patient numbers. PMID:25796053

A Magnetic Resonance Imaging-Conditional External Cardiac Defibrillator for Resuscitation Within the Magnetic Resonance Imaging Scanner Bore.

PubMed

Schmidt, Ehud J; Watkins, Ronald D; Zviman, Menekhem M; Guttman, Michael A; Wang, Wei; Halperin, Henry A

2016-10-01

Subjects undergoing cardiac arrest within a magnetic resonance imaging (MRI) scanner are currently removed from the bore and then from the MRI suite, before the delivery of cardiopulmonary resuscitation and defibrillation, potentially increasing the risk of mortality. This precludes many higher-risk (acute ischemic and acute stroke) patients from undergoing MRI and MRI-guided intervention. An MRI-conditional cardiac defibrillator should enable scanning with defibrillation pads attached and the generator ON, enabling application of defibrillation within the seconds of MRI after a cardiac event. An MRI-conditional external defibrillator may improve patient acceptance for MRI procedures. A commercial external defibrillator was rendered 1.5 Tesla MRI-conditional by the addition of novel radiofrequency filters between the generator and commercial disposable surface pads. The radiofrequency filters reduced emission into the MRI scanner and prevented cable/surface pad heating during imaging, while preserving all the defibrillator monitoring and delivery functions. Human volunteers were imaged using high specific absorption rate sequences to validate MRI image quality and lack of heating. Swine were electrically fibrillated (n=4) and thereafter defibrillated both outside and inside the MRI bore. MRI image quality was reduced by 0.8 or 1.6 dB, with the generator in monitoring mode and operating on battery or AC power, respectively. Commercial surface pads did not create artifacts deeper than 6 mm below the skin surface. Radiofrequency heating was within US Food and Drug Administration guidelines. Defibrillation was completely successful inside and outside the MRI bore. A prototype MRI-conditional defibrillation system successfully defibrillated in the MRI without degrading the image quality or increasing the time needed for defibrillation. It can increase patient acceptance for MRI procedures. © 2016 American Heart Association, Inc.

Portable MRI developed at Los Alamos

ScienceCinema

Espy, Michelle

2018-02-14

Scientists at Los Alamos National Laboratory are developing an ultra-low-field Magnetic Resonance Imaging (MRI) system that could be low-power and lightweight enough for forward deployment on the battlefield and to field hospitals in the World's poorest regions. "MRI technology is a powerful medical diagnostic tool," said Michelle Espy, the Battlefield MRI (bMRI) project leader, "ideally suited for imaging soft-tissue injury, particularly to the brain." But hospital-based MRI devices are big and expensive, and require considerable infrastructure, such as large quantities of cryogens like liquid nitrogen and helium, and they typically use a large amount of energy. "Standard MRI machines just can't go everywhere," said Espy. "Soldiers wounded in battle usually have to be flown to a large hospital and people in emerging nations just don't have access to MRI at all. We've been in contact with doctors who routinely work in the Third World and report that MRI would be extremely valuable in treating pediatric encephalopathy, and other serious diseases in children." So the Los Alamos team started thinking about a way to make an MRI device that could be relatively easy to transport, set up, and use in an unconventional setting. Conventional MRI machines use very large magnetic fields that align the protons in water molecules to then create magnetic resonance signals, which are detected by the machine and turned into images. The large magnetic fields create exceptionally detailed images, but they are difficult and expensive to make. Espy and her team wanted to see if images of sufficient quality could be made with ultra-low-magnetic fields, similar in strength to the Earth's magnetic field. To achieve images at such low fields they use exquisitely sensitive detectors called Superconducting Quantum Interference Devices, or SQUIDs. SQUIDs are among the most sensitive magnetic field detectors available, so interference with the signal is the primary stumbling block. "SQUIDs are so sensitive they'll respond to a truck driving by outside or a radio signal 50 miles away," said Al Urbaitis, a bMRI engineer. The team's first generation bMRI had to be built in a large metal housing in order to shield it from interference. Now the Los Alamos team is working in the open environment without the large metal housing using a lightweight series of wire coils that surround the bMRI system to compensate the Earth’s magnetic field. In the future, the field compensation system will also function similar to noise-cancelling headphones to eradicate invading magnetic field signals on-the-fly.

Portable MRI developed at Los Alamos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Espy, Michelle

Scientists at Los Alamos National Laboratory are developing an ultra-low-field Magnetic Resonance Imaging (MRI) system that could be low-power and lightweight enough for forward deployment on the battlefield and to field hospitals in the World's poorest regions. "MRI technology is a powerful medical diagnostic tool," said Michelle Espy, the Battlefield MRI (bMRI) project leader, "ideally suited for imaging soft-tissue injury, particularly to the brain." But hospital-based MRI devices are big and expensive, and require considerable infrastructure, such as large quantities of cryogens like liquid nitrogen and helium, and they typically use a large amount of energy. "Standard MRI machines justmore » can't go everywhere," said Espy. "Soldiers wounded in battle usually have to be flown to a large hospital and people in emerging nations just don't have access to MRI at all. We've been in contact with doctors who routinely work in the Third World and report that MRI would be extremely valuable in treating pediatric encephalopathy, and other serious diseases in children." So the Los Alamos team started thinking about a way to make an MRI device that could be relatively easy to transport, set up, and use in an unconventional setting. Conventional MRI machines use very large magnetic fields that align the protons in water molecules to then create magnetic resonance signals, which are detected by the machine and turned into images. The large magnetic fields create exceptionally detailed images, but they are difficult and expensive to make. Espy and her team wanted to see if images of sufficient quality could be made with ultra-low-magnetic fields, similar in strength to the Earth's magnetic field. To achieve images at such low fields they use exquisitely sensitive detectors called Superconducting Quantum Interference Devices, or SQUIDs. SQUIDs are among the most sensitive magnetic field detectors available, so interference with the signal is the primary stumbling block. "SQUIDs are so sensitive they'll respond to a truck driving by outside or a radio signal 50 miles away," said Al Urbaitis, a bMRI engineer. The team's first generation bMRI had to be built in a large metal housing in order to shield it from interference. Now the Los Alamos team is working in the open environment without the large metal housing using a lightweight series of wire coils that surround the bMRI system to compensate the Earth’s magnetic field. In the future, the field compensation system will also function similar to noise-cancelling headphones to eradicate invading magnetic field signals on-the-fly.« less

The Effect of Passive Movement for Paretic Ankle-Foot and Brain Activity in Post-Stroke Patients.

PubMed

Vér, Csilla; Emri, Miklós; Spisák, Tamás; Berényi, Ervin; Kovács, Kázmér; Katona, Péter; Balkay, László; Menyhárt, László; Kardos, László; Csiba, László

2016-01-01

This study aims at investigating the short-term efficacy of the continuous passive motion (CPM) device developed for the therapy of ankle-foot paresis and to investigate by fMRI the blood oxygen level-dependent responses (BOLD) during ankle passive movement (PM). Sixty-four stroke patients were investigated. Patients were assigned into 2 groups: 49 patients received both 15 min manual and 30 min device therapy (M + D), while the other group (n = 15) received only 15 min manual therapy (M). A third group of stroke patients (n = 12) was investigated by fMRI before and immediately after 30 min CPM device therapy. There was no direct relation between the fMRI group and the other 2 groups. All subjects were assessed using the Modified Ashworth Scale (MAS) and a goniometer. Mean MAS decreased, the ankle's mean plantar flexion and dorsiflexion passive range of motion (PROM) increased and the equinovalgus improved significantly in the M + D group. In the fMRI group, the PM of the paretic ankle increased BOLD responses; this was observed in the contralateral pre- and postcentral gyrus, superior temporal gyrus, central opercular cortex, and in the ipsilateral postcentral gyrus, frontal operculum cortex and cerebellum. Manual therapy with CPM device therapy improved the ankle PROM, equinovalgus and severity of spasticity. The ankle PM increased ipsi- and contralateral cortical activation. © 2016 S. Karger AG, Basel.

MRI of the Prostate

MedlinePlus

... cardiac defibrillators and pacemakers You should tell the technologist if you have medical or electronic devices in your body. These objects may interfere with the exam or potentially pose a risk, depending on their nature and the strength of the MRI ...

Thermal ablation system using high intensity focused ultrasound (HIFU) and guided by MRI

NASA Astrophysics Data System (ADS)

Damianou, C.; Ioannides, K.; HadjiSavas, V.; Milonas, N.; Couppis, A.; Iosif, D.; Komodromos, M.; Vrionides, F.

2009-04-01

In this paper magnetic resonance imaging (MRI) is investigated for monitoring lesions created by high intensity focused ultrasound (HIFU) in kidney, liver and brain in vitro and in vivo. Spherically focused transducers of 4 cm diameter, focusing at 10 cm and operating at 1 and 4 MHz were used. An MRI compatible positioning device was developed in order to scan the HIFU transducer. The MRI compatibility of the system was successfully demonstrated in a clinical high-field MRI scanner. The ability of the positioning device to accurately move the transducer thus creating discrete and overlapping lesions in biological tissue was tested successfully. A simple, cost effective, portable positioning device has been developed which can be used in virtually any clinical MRI scanner since it can be sited on the scanner's table. The propagation of HIFU can use either a lateral or superior-inferior approach. Both T1-w FSE and T2-w FSE imaged successfully lesions in kidney and liver. T1-w FSE and T2-w FSE and FLAIR shows better anatomical details in brain than T1-w FSE, but with T1-w FSE the contrast between lesion and brain is higher for both thermal and bubbly lesion. With this system we were able to create large lesions (by producing overlapping lesions). The length of the lesions in vivo brain was much higher than the length in vitro, proving that the penetration in the in vitro brain is limited by reflection due to trapped bubbles in the blood vessels.

[Mechanical Shimming Method and Implementation for Permanent Magnet of MRI System].

PubMed

Xue, Tingqiang; Chen, Jinjun

2015-03-01

A mechanical shimming method and device for permanent magnet of MRI system has been developed to meet its stringent homogeneity requirement without time-consuming passive shimming on site, installation and adjustment efficiency has been increased.

Magnetic susceptibility and magnetic resonance measurements of the moisture content and hydration condition of a magnetic mixture material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsukada, K., E-mail: tsukada@cc.okayama-u.ac.jp; Kusaka, T.; Saari, M. M.

2014-05-07

We developed a magnetic measurement method to measure the moisture content and hydration condition of mortar as a magnetic mixture material. Mortar is a mixture of Portland cement, sand, and water, and these materials exhibit different magnetic properties. The magnetization–magnetic field curves of these components and of mortars with different moisture contents were measured, using a specially developed high-temperature-superconductor superconducting quantum interference device. Using the differences in magnetic characteristics, the moisture content of mortar was measured at the ferromagnetic saturation region over 250 mT. A correlation between magnetic susceptibility and moisture content was successfully established. After Portland cement and water aremore » mixed, hydration begins. At the early stage of the hydration/gel, magnetization strength increased over time. To investigate the magnetization change, we measured the distribution between bound and free water in the mortar in the early stage by magnetic resonance imaging (MRI). The MRI results suggest that the amount of free water in mortar correlates with the change in magnetic susceptibility.« less

Clinical, CSF, and MRI findings in Devic's neuromyelitis optica.

PubMed Central

O'Riordan, J I; Gallagher, H L; Thompson, A J; Howard, R S; Kingsley, D P; Thompson, E J; McDonald, W I; Miller, D H

1996-01-01

OBJECTIVES: Since Devic's original description of neuromyelitis optica in 1894 there has been much debate regarding its aetiology. A specific cause has been identified in a minority of cases but in most the question has arisen whether or not Devic's neuromyelitis optica is a variant of multiple sclerosis. This study was undertaken to help clarify this issue. METHODS: Neuromyelitis optica was defined as (1) a severe transverse myelitis; (2) an acute unilateral or bilateral optic neuropathy; (3) no clinical involvement beyond the spinal cord or optic nerves, and (4) a monophasic or multiphasic illness. The clinical and autoantibody status was documented. Patients underwent CSF examination and MRI of brain and spinal cord. RESULTS: Twelve patients, with a mean age of presentation of 35.1 years, were seen. Eleven were women; vision was reduced to counting fingers or worse in 10 patients and seven became confined to a wheelchair. Examination of CSF showed local synthesis of oligoclonal bands in only two patients and a neutrophil pleocytosis in two. A possible aetiology was identified in five: a specific connective tissue disorder (two), pulmonary tuberculosis (one), and possible acute disseminated encephalomyelitis (two). Six had non-specific increases in various autoantibodies. Eleven patients underwent MRI of the brain and spinal cord. In 10 there were diffuse abnormalities involving cervical and thoracic cords with extensive swelling in the acute phase. Brain MRI was normal in five; in five there were multiple deep white matter lesions, and one patient had minor age related changes. CONCLUSION: It is proposed that Devic's neuromyelitis optica is a distinctive disorder with some clinical, CSF, and MRI features different from those found in classic multiple sclerosis. In most cases a specific aetiology is not identified, but an immunological mechanism of tissue damage seems likely. Images PMID:8774400

Ventricular Assist Device implant (AB 5000) prototype cannula: In vitro assessment of MRI issues at 3-Tesla

PubMed Central

Shellock, Frank G; Valencerina, Samuel

2008-01-01

Purpose To evaluate MRI issues at 3-Tesla for a ventricular assist device (VAD). Methods The AB5000 Ventricle with a prototype Nitinol wire-reinforced In-Flow Cannula and Out-Flow Cannula attached (Abiomed, Inc., Danvers, MA) was evaluated for magnetic field interactions, heating, and artifacts at 3-Tesla. MRI-related heating was assessed with the device in a gelled-saline-filled, head/torso phantom using a transmit/received RF body coil while performing MRI at a whole body averaged SAR of 3-W/kg for 15-min. Artifacts were assessed for the main metallic component of this VAD (atrial cannula) using T1-weighted, spin echo and gradient echo pulse sequences. Results The AB5000 Ventricle with the prototype In-Flow Cannula and Out-Flow Cannula attached showed relatively minor magnetic field interactions that will not cause movement in situ. Heating was not excessive (highest temperature change, +0.8°C). Artifacts may create issues for diagnostic imaging if the area of interest is in the same area or close to the implanted metallic component of this VAD (i.e., the venous cannula). Conclusion The results of this investigation demonstrated that it would be acceptable for a patient with this VAD (AB5000 Ventricle with a prototype Nitinol wire-reinforced In-Flow Cannula and Out-Flow Cannula attached) to undergo MRI at 3-Tesla or less. Notably, it is likely that the operation console for this device requires positioning a suitable distance (beyond the 100 Gauss line or in the MR control room) from the 3-Tesla MR system to ensure proper function of the VAD. PMID:18495028

Microcontroller based fibre-optic visual presentation system for multisensory neuroimaging.

PubMed

Kurniawan, Veldri; Klemen, Jane; Chambers, Christopher D

2011-10-30

Presenting visual stimuli in physical 3D space during fMRI experiments carries significant technical challenges. Certain types of multisensory visuotactile experiments and visuomotor tasks require presentation of visual stimuli in peripersonal space, which cannot be accommodated by ordinary projection screens or binocular goggles. However, light points produced by a group of LEDs can be transmitted through fibre-optic cables and positioned anywhere inside the MRI scanner. Here we describe the design and implementation of a microcontroller-based programmable digital device for controlling fibre-optically transmitted LED lights from a PC. The main feature of this device is the ability to independently control the colour, brightness, and timing of each LED. Moreover, the device was designed in a modular and extensible way, which enables easy adaptation for various experimental paradigms. The device was tested and validated in three fMRI experiments involving basic visual perception, a simple colour discrimination task, and a blocked multisensory visuo-tactile task. The results revealed significant lateralized activation in occipital cortex of all participants, a reliable response in ventral occipital areas to colour stimuli elicited by the device, and strong activations in multisensory brain regions in the multisensory task. Overall, these findings confirm the suitability of this device for presenting complex fibre-optic visual and cross-modal stimuli inside the scanner. Copyright © 2011 Elsevier B.V. All rights reserved.

An MRI-compatible hand sensory vibrotactile system.

PubMed

Wang, Fa; Lakshminarayanan, Kishor; Slota, Gregory P; Seo, Na Jin; Webster, John G

2015-01-01

Recently, the application of vibrotactile noise to the wrist or back of the hand has been shown to enhance fingertip tactile sensory perception (Enders et al 2013), supporting the potential for an assistive device worn at the wrist, that generates minute vibrations to help the elderly or patients with sensory deficit. However, knowledge regarding the detailed physiological mechanism behind this sensory improvement in the central nervous system, especially in the human brain, is limited, hindering progress in development and use of such assistive devices. To enable investigation of the impact of vibrotactile noise on sensorimotor brain activity in humans, a magnetic resonance imaging (MRI)-compatible vibrotactile system was developed to provide vibrotactile noise during an MRI of the brain. The vibrotactile system utilizes a remote (outside the MR room) signal amplifier which provides a voltage from -40 to +40 V to drive a 12 mm diameter piezoelectric vibrator (inside the MR room). It is portable and is found to be MRI-compatible which enables its use for neurologic investigation with MRI. The system was also found to induce an improvement in fingertip tactile sensation, consistent with the previous study.

Comprehensive MRI simulation methodology using a dedicated MRI scanner in radiation oncology for external beam radiation treatment planning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paulson, Eric S., E-mail: epaulson@mcw.edu; Erickson, Beth; Schultz, Chris

Purpose: The use of magnetic resonance imaging (MRI) in radiation oncology is expanding rapidly, and more clinics are integrating MRI into their radiation therapy workflows. However, radiation therapy presents a new set of challenges and places additional constraints on MRI compared to diagnostic radiology that, if not properly addressed, can undermine the advantages MRI offers for radiation treatment planning (RTP). The authors introduce here strategies to manage several challenges of using MRI for virtual simulation in external beam RTP. Methods: A total of 810 clinical MRI simulation exams were performed using a dedicated MRI scanner for external beam RTP ofmore » brain, breast, cervix, head and neck, liver, pancreas, prostate, and sarcoma cancers. Patients were imaged in treatment position using MRI-optimal immobilization devices. Radiofrequency (RF) coil configurations and scan protocols were optimized based on RTP constraints. Off-resonance and gradient nonlinearity-induced geometric distortions were minimized or corrected prior to using images for RTP. A multidisciplinary MRI simulation guide, along with window width and level presets, was created to standardize use of MR images during RTP. A quality assurance program was implemented to maintain accuracy and repeatability of MRI simulation exams. Results: The combination of a large bore scanner, high field strength, and circumferentially wrapped, flexible phased array RF receive coils permitted acquisition of thin slice images with high contrast-to-noise ratio (CNR) and image intensity uniformity, while simultaneously accommodating patient setup and immobilization devices. Postprocessing corrections and alternative acquisition methods were required to reduce or correct off-resonance and gradient nonlinearity induced geometric distortions. Conclusions: The methodology described herein contains practical strategies the authors have implemented through lessons learned performing clinical MRI simulation exams. In their experience, these strategies provide robust, high fidelity, high contrast MR images suitable for external beam RTP.« less

Radio-frequency energy quantification in magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Alon, Leeor

Mapping of radio frequency (RF) energy deposition has been challenging for 50+ years, especially, when scanning patients in the magnetic resonance imaging (MRI) environment. As result, electromagnetic simulation software is often used for estimating the specific absorption rate (SAR), the rate of RF energy deposition in tissue. The thesis work presents challenges associated with aligning information provided by electromagnetic simulation and MRI experiments. As result of the limitations of simulations, experimental methods for the quantification of SAR were established. A system for quantification of the total RF energy deposition was developed for parallel transmit MRI (a system that uses multiple antennas to excite and image the body). The system is capable of monitoring and predicting channel-by-channel RF energy deposition, whole body SAR and capable of tracking potential hardware failures that occur in the transmit chain and may cause the deposition of excessive energy into patients. Similarly, we demonstrated that local RF power deposition can be mapped and predicted for parallel transmit systems based on a series of MRI temperature mapping acquisitions. Resulting from the work, we developed tools for optimal reconstruction temperature maps from MRI acquisitions. The tools developed for temperature mapping paved the way for utilizing MRI as a diagnostic tool for evaluation of RF/microwave emitting device safety. Quantification of the RF energy was demonstrated for both MRI compatible and non-MRI-compatible devices (such as cell phones), while having the advantage of being noninvasive, of providing millimeter resolution and high accuracy.

Towards a Teleoperated Needle Driver Robot with Haptic Feedback for RFA of Breast Tumors under Continuous MRI1

PubMed Central

Kokes, Rebecca; Lister, Kevin; Gullapalli, Rao; Zhang, Bao; MacMillan, Alan; Richard, Howard; Desai, Jaydev P.

2009-01-01

Objective The purpose of this paper is to explore the feasibility of developing a MRI-compatible needle driver system for radiofrequency ablation (RFA) of breast tumors under continuous MRI imaging while being teleoperated by a haptic feedback device from outside the scanning room. The developed needle driver prototype was designed and tested for both tumor targeting capability as well as RFA. Methods The single degree-of-freedom (DOF) prototype was interfaced with a PHANToM haptic device controlled from outside the scanning room. Experiments were performed to demonstrate MRI-compatibility and position control accuracy with hydraulic actuation, along with an experiment to determine the PHANToM’s ability to guide the RFA tool to a tumor nodule within a phantom breast tissue model while continuously imaging within the MRI and receiving force feedback from the RFA tool. Results Hydraulic actuation is shown to be a feasible actuation technique for operation in an MRI environment. The design is MRI-compatible in all aspects except for force sensing in the directions perpendicular to the direction of motion. Experiments confirm that the user is able to detect healthy vs. cancerous tissue in a phantom model when provided with both visual (imaging) feedback and haptic feedback. Conclusion The teleoperated 1-DOF needle driver system presented in this paper demonstrates the feasibility of implementing a MRI-compatible robot for RFA of breast tumors with haptic feedback capability. PMID:19303805

3-T MRI safety assessments of magnetic dental attachments and castable magnetic alloys

PubMed Central

Miyata, K; Abe, Y; Ishii, T; Ishigami, T; Ohtani, K; Nagai, E; Ohyama, T; Umekawa, Y; Nakabayashi, S

2015-01-01

Objectives: To assess the safety of different magnetic dental attachments during 3-T MRI according to the American Society for Testing and Materials F2182-09 and F2052-06e1 standard testing methods and to develop a method to determine MRI compatibility by measuring magnetically induced torque. Methods: The temperature elevations, magnetically induced forces and torques of a ferromagnetic stainless steel keeper, a coping comprising a keeper and a cast magnetic alloy coping were measured on MRI systems. Results: The coping comprising a keeper demonstrated the maximum temperature increase (1.42 °C) for the whole-body-averaged specific absorption rate and was calculated as 2.1 W kg−1 with the saline phantom. All deflection angles exceeded 45°. The cast magnetic alloy coping had the greatest deflection force (0.33 N) during 3-T MRI and torque (1.015 mN m) during 0.3-T MRI. Conclusions: The tested devices showed minimal radiofrequency (RF)-induced heating in a 3-T MR environment, but the cast magnetic alloy coping showed a magnetically induced deflection force and torque approximately eight times that of the keepers. For safety, magnetic dental attachments should be inspected before and after MRI and large prostheses containing cast magnetic alloy should be removed. Although magnetic dental attachments may pose no great risk of RF-induced heating or magnetically induced torque during 3-T MRI, their magnetically induced deflection forces tended to exceed acceptable limits. Therefore, the inspection of such devices before and after MRI is important for patient safety. PMID:25785821

Remote NMR/MRI detection of laser polarized gases

DOEpatents

Pines, Alexander; Saxena, Sunil; Moule, Adam; Spence, Megan; Seeley, Juliette A.; Pierce, Kimberly L.; Han, Song-I; Granwehr, Josef

2006-06-13

An apparatus and method for remote NMR/MRI spectroscopy having an encoding coil with a sample chamber, a supply of signal carriers, preferably hyperpolarized xenon and a detector allowing the spatial and temporal separation of signal preparation and signal detection steps. This separation allows the physical conditions and methods of the encoding and detection steps to be optimized independently. The encoding of the carrier molecules may take place in a high or a low magnetic field and conventional NMR pulse sequences can be split between encoding and detection steps. In one embodiment, the detector is a high magnetic field NMR apparatus. In another embodiment, the detector is a superconducting quantum interference device. A further embodiment uses optical detection of Rb--Xe spin exchange. Another embodiment uses an optical magnetometer using non-linear Faraday rotation. Concentration of the signal carriers in the detector can greatly improve the signal to noise ratio.

An MR-compatible device for delivering smoked marijuana during functional imaging.

PubMed

Frederick, Blaise deB; Lindsey, Kimberly P; Nickerson, Lisa D; Ryan, Elizabeth T; Lukas, Scott E

2007-05-01

Smoking is the preferred method of administration for two of the most frequently abused drugs, marijuana and nicotine. The high temporal and spatial resolution of functional magnetic resonance imaging (fMRI) make it a natural choice for studying the neurobiological effects of smoked drugs if the challenges of smoking in a magnetic resonance (MR) scanner can be overcome. We report on a design for an MR-compatible smoking device that can be used for smoking marijuana (or tobacco) during fMRI examinations. Nine volunteers smoked marijuana cigarettes (3.51% Delta9-THC) on two occasions: with and without the device. The device allowed subjects to smoke while they lay in the scanner, while containing all smoke and odors. Plasma Delta9-THC, subjective reports of intoxication, and heart rate increases are reported, and were all similar in individuals smoking marijuana either with or without the device. The use of this device will help advance research studies on smoked drugs including marijuana, tobacco and crack cocaine.

ICNIRP Statement on Diagnostic Devices Using Non-ionizing Radiation: Existing Regulations and Potential Health Risks.

PubMed

2017-03-01

Use of non-ionizing radiation (NIR) for diagnostic purposes allows non-invasive assessment of the structure and function of the human body and is widely employed in medical care. ICNIRP has published previous statements about the protection of patients during medical magnetic resonance imaging (MRI), but diagnostic methods using other forms of NIR have not been considered. This statement reviews the range of diagnostic NIR devices currently used in clinical settings; documents the relevant regulations and policies covering patients and health care workers; reviews the evidence around potential health risks to patients and health care workers exposed to diagnostic NIR; and identifies situations of high NIR exposure from diagnostic devices in which patients or health care workers might not be adequately protected by current regulations. Diagnostic technologies were classified by the types of NIR that they employ. The aim was to describe the techniques in terms of general device categories which may encompass more specific devices or techniques with similar scientific principles. Relevant legally-binding regulations for protection of patients and workers and organizations responsible for those regulations were summarized. Review of the epidemiological evidence concerning health risks associated with exposure to diagnostic NIR highlighted a lack of data on potential risks to the fetus exposed to MRI during the first trimester, and on long-term health risks in workers exposed to MRI. Most of the relevant epidemiological evidence that is currently available relates to MRI or ultrasound. Exposure limits are needed for exposures from diagnostic technologies using optical radiation within the body. There is a lack of data regarding risk of congenital malformations following exposure to ultrasound in utero in the first trimester and also about the possible health effects of interactions between ultrasound and contrast media.

ICNIRP Statement on Diagnostic Devices Using Non-ionizing Radiation: Existing Regulations and Potential Health Risks

PubMed Central

2017-01-01

Abstract Use of non-ionizing radiation (NIR) for diagnostic purposes allows non-invasive assessment of the structure and function of the human body and is widely employed in medical care. ICNIRP has published previous statements about the protection of patients during medical magnetic resonance imaging (MRI), but diagnostic methods using other forms of NIR have not been considered. This statement reviews the range of diagnostic NIR devices currently used in clinical settings; documents the relevant regulations and policies covering patients and health care workers; reviews the evidence around potential health risks to patients and health care workers exposed to diagnostic NIR; and identifies situations of high NIR exposure from diagnostic devices in which patients or health care workers might not be adequately protected by current regulations. Diagnostic technologies were classified by the types of NIR that they employ. The aim was to describe the techniques in terms of general device categories which may encompass more specific devices or techniques with similar scientific principles. Relevant legally-binding regulations for protection of patients and workers and organizations responsible for those regulations were summarized. Review of the epidemiological evidence concerning health risks associated with exposure to diagnostic NIR highlighted a lack of data on potential risks to the fetus exposed to MRI during the first trimester, and on long-term health risks in workers exposed to MRI. Most of the relevant epidemiological evidence that is currently available relates to MRI or ultrasound. Exposure limits are needed for exposures from diagnostic technologies using optical radiation within the body. There is a lack of data regarding risk of congenital malformations following exposure to ultrasound in utero in the first trimester and also about the possible health effects of interactions between ultrasound and contrast media. PMID:28121732

Magnetic Resonance Safety

PubMed Central

Sammet, Steffen

2016-01-01

Magnetic Resonance Imaging (MRI) has a superior soft-tissue contrast compared to other radiological imaging modalities and its physiological and functional applications have led to a significant increase in MRI scans worldwide. A comprehensive MRI safety training to protect patients and other healthcare workers from potential bio-effects and risks of the magnetic fields in an MRI suite is therefore essential. The knowledge of the purpose of safety zones in an MRI suite as well as MRI appropriateness criteria is important for all healthcare professionals who will work in the MRI environment or refer patients for MRI scans. The purpose of this article is to give an overview of current magnetic resonance safety guidelines and discuss the safety risks of magnetic fields in an MRI suite including forces and torque of ferromagnetic objects, tissue heating, peripheral nerve stimulation and hearing damages. MRI safety and compatibility of implanted devices, MRI scans during pregnancy and the potential risks of MRI contrast agents will also be discussed and a comprehensive MRI safety training to avoid fatal accidents in an MRI suite will be presented. PMID:26940331

Design and Evaluation of a Cable-Driven fMRI-Compatible Haptic Interface to Investigate Precision Grip Control

PubMed Central

Vigaru, Bogdan; Sulzer, James; Gassert, Roger

2016-01-01

Our hands and fingers are involved in almost all activities of daily living and, as such, have a disproportionately large neural representation. Functional magnetic resonance imaging investigations into the neural control of the hand have revealed great advances, but the harsh MRI environment has proven to be a challenge to devices capable of delivering a large variety of stimuli necessary for well-controlled studies. This paper presents a fMRI-compatible haptic interface to investigate the neural mechanisms underlying precision grasp control. The interface, located at the scanner bore, is controlled remotely through a shielded electromagnetic actuation system positioned at the end of the scanner bed and then through a high stiffness, low inertia cable transmission. We present the system design, taking into account requirements defined by the biomechanics and dynamics of the human hand, as well as the fMRI environment. Performance evaluation revealed a structural stiffness of 3.3 N/mm, renderable forces up to 94 N, and a position control bandwidth of at least 19 Hz. MRI-compatibility tests showed no degradation in the operation of the haptic interface or the image quality. A preliminary fMRI experiment during a pilot study validated the usability of the haptic interface, illustrating the possibilities offered by this device. PMID:26441454

Assessment of EchoMRI-AH versus dual-energy X-ray absorptiometry by iDXA to measure human body composition.

PubMed

Marlatt, K L; Greenway, F L; Ravussin, E

2017-04-01

Comparison of percent fat mass across different body composition analysis devices is important given variation in technology accuracy and precision, as well as the growing need for cross-validation of devices often applied across longitudinal studies. We compared EchoMRI-AH and Lunar iDXA quantification of percent body fat (PBF) in 84 adults (43M, 41F), with the mean age 39.7±15.9 years and body mass index (BMI) 26.2±5.3 kg/m 2 . PBF correlated strongly between devices (r>0.95, P<0.0001). A prediction equation was derived in half of the subjects, and the other half were used to cross-validate the proposed equation (EchoMRI-AH PBF=[(0.94 × iDXA PBF)+(0.14 × Age)+(3.3 × Female)-8.83). The mean PBF difference (predicted-measured) in the validation group was not different from 0 (diff=0.27%, 95% confidence interval: -0.42-0.96, P=0.430). Bland-Altman plots showed a bias with higher measured PBF on EchoMRI-AH versus iDXA in all 84 subjects (β=0.13, P<0.0001). The proposed prediction equation was valid in our cross-validation sample, and it has the potential to be applied across multicenter studies.

fMRI-Compatible Electromagnetic Haptic Interface.

PubMed

Riener, R; Villgrattner, T; Kleiser, R; Nef, T; Kollias, S

2005-01-01

A new haptic interface device is suggested, which can be used for functional magnetic resonance imaging (fMRI) studies. The basic component of this 1 DOF haptic device are two coils that produce a Lorentz force induced by the large static magnetic field of the MR scanner. A MR-compatible optical angular encoder and a optical force sensor enable the implementation of different control architectures for haptic interactions. The challenge was to provide a large torque, and not to affect image quality by the currents applied in the device. The haptic device was tested in a 3T MR scanner. With a current of up to 1A and a distance of 1m to the focal point of the MR-scanner it was possible to generate torques of up to 4 Nm. Within these boundaries image quality was not affected.

Sequence design and software environment for real-time navigation of a wireless ferromagnetic device using MRI system and single echo 3D tracking.

PubMed

Chanu, A; Aboussouan, E; Tamaz, S; Martel, S

2006-01-01

Software architecture for the navigation of a ferromagnetic untethered device in a 1D and 2D phantom environment is briefly described. Navigation is achieved using the real-time capabilities of a Siemens 1.5 T Avanto MRI system coupled with a dedicated software environment and a specially developed 3D tracking pulse sequence. Real-time control of the magnetic core is executed through the implementation of a simple PID controller. 1D and 2D experimental results are presented.

Haptic fMRI: Reliability and performance of electromagnetic haptic interfaces for motion and force neuroimaging experiments.

PubMed

Menon, Samir; Zhu, Jack; Goyal, Deeksha; Khatib, Oussama

2017-07-01

Haptic interfaces compatible with functional magnetic resonance imaging (Haptic fMRI) promise to enable rich motor neuroscience experiments that study how humans perform complex manipulation tasks. Here, we present a large-scale study (176 scans runs, 33 scan sessions) that characterizes the reliability and performance of one such electromagnetically actuated device, Haptic fMRI Interface 3 (HFI-3). We outline engineering advances that ensured HFI-3 did not interfere with fMRI measurements. Observed fMRI temporal noise levels with HFI-3 operating were at the fMRI baseline (0.8% noise to signal). We also present results from HFI-3 experiments demonstrating that high resolution fMRI can be used to study spatio-temporal patterns of fMRI blood oxygenation dependent (BOLD) activation. These experiments include motor planning, goal-directed reaching, and visually-guided force control. Observed fMRI responses are consistent with existing literature, which supports Haptic fMRI's effectiveness at studying the brain's motor regions.

A Web-based searchable system to confirm magnetic resonance compatibility of implantable medical devices in Japan: a preliminary study.

PubMed

Fujiwara, Yasuhiro; Fujioka, Hitoshi; Watanabe, Tomoko; Sekiguchi, Maiko; Murakami, Ryuji

2017-09-01

Confirmation of the magnetic resonance (MR) compatibility of implanted medical devices (IMDs) is mandatory before conducting magnetic resonance imaging (MRI) examinations. In Japan, few such confirmation methods are in use, and they are time-consuming. This study aimed to develop a Web-based searchable MR safety information system to confirm IMD compatibility and to evaluate the usefulness of the system. First, MR safety information for intravascular stents and stent grafts sold in Japan was gathered by interviewing 20 manufacturers. These IMDs were categorized based on the descriptions available on medical package inserts as: "MR Safe," "MR Conditional," "MR Unsafe," "Unknown," and "No Medical Package Insert Available". An MR safety information database for implants was created based on previously proposed item lists. Finally, a Web-based searchable system was developed using this database. A questionnaire was given to health-care personnel in Japan to evaluate the usefulness of this system. Seventy-nine datasets were collected using information provided by 12 manufacturers and by investigating the medical packaging of the IMDs. Although the datasets must be updated by collecting data from other manufacturers, this system facilitates the easy and rapid acquisition of MR safety information for IMDs, thereby improving the safety of MRI examinations.

Real-Time MRI-Guided Cardiac Cryo-Ablation: A Feasibility Study.

PubMed

Kholmovski, Eugene G; Coulombe, Nicolas; Silvernagel, Joshua; Angel, Nathan; Parker, Dennis; Macleod, Rob; Marrouche, Nassir; Ranjan, Ravi

2016-05-01

MRI-based ablation provides an attractive capability of seeing ablation-related tissue changes in real time. Here we describe a real-time MRI-based cardiac cryo-ablation system. Studies were performed in canine model (n = 4) using MR-compatible cryo-ablation devices built for animal use: focal cryo-catheter with 8 mm tip and 28 mm diameter cryo-balloon. The main steps of MRI-guided cardiac cryo-ablation procedure (real-time navigation, confirmation of tip-tissue contact, confirmation of vessel occlusion, real-time monitoring of a freeze zone formation, and intra-procedural assessment of lesions) were validated in a 3 Tesla clinical MRI scanner. The MRI compatible cryo-devices were advanced to the right atrium (RA) and right ventricle (RV) and their position was confirmed by real-time MRI. Specifically, contact between catheter tip and myocardium and occlusion of superior vena cava (SVC) by the balloon was visually validated. Focal cryo-lesions were created in the RV septum. Circumferential ablation of SVC-RA junction with no gaps was achieved using the cryo-balloon. Real-time visualization of freeze zone formation was achieved in all studies when lesions were successfully created. The ablations and presence of collateral damage were confirmed by T1-weighted and late gadolinium enhancement MRI and gross pathological examination. This study confirms the feasibility of a MRI-based cryo-ablation system in performing cardiac ablation procedures. The system allows real-time catheter navigation, confirmation of catheter tip-tissue contact, validation of vessel occlusion by cryo-balloon, real-time monitoring of a freeze zone formation, and intra-procedural assessment of ablations including collateral damage. © 2016 Wiley Periodicals, Inc.

Small animal simultaneous PET/MRI: initial experiences in a 9.4 T microMRI

NASA Astrophysics Data System (ADS)

Harsha Maramraju, Sri; Smith, S. David; Junnarkar, Sachin S.; Schulz, Daniela; Stoll, Sean; Ravindranath, Bosky; Purschke, Martin L.; Rescia, Sergio; Southekal, Sudeepti; Pratte, Jean-François; Vaska, Paul; Woody, Craig L.; Schlyer, David J.

2011-04-01

We developed a non-magnetic positron-emission tomography (PET) device based on the rat conscious animal PET that operates in a small-animal magnetic resonance imaging (MRI) scanner, thereby enabling us to carry out simultaneous PET/MRI studies. The PET detector comprises 12 detector blocks, each being a 4 × 8 array of lutetium oxyorthosilicate crystals (2.22 × 2.22 × 5 mm3) coupled to a matching non-magnetic avalanche photodiode array. The detector blocks, housed in a plastic case, form a 38 mm inner diameter ring with an 18 mm axial extent. Custom-built MRI coils fit inside the positron-emission tomography (PET) device, operating in transceiver mode. The PET insert is integrated with a Bruker 9.4 T 210 mm clear-bore diameter MRI scanner. We acquired simultaneous PET/MR images of phantoms, of in vivo rat brain, and of cardiac-gated mouse heart using [11C]raclopride and 2-deoxy-2-[18F]fluoro-d-glucose PET radiotracers. There was minor interference between the PET electronics and the MRI during simultaneous operation, and small effects on the signal-to-noise ratio in the MR images in the presence of the PET, but no noticeable visual artifacts. Gradient echo and high-duty-cycle spin echo radio frequency (RF) pulses resulted in a 7% and a 28% loss in PET counts, respectively, due to high PET counts during the RF pulses that had to be gated out. The calibration of the activity concentration of PET data during MR pulsing is reproducible within less than 6%. Our initial results demonstrate the feasibility of performing simultaneous PET and MRI studies in adult rats and mice using the same PET insert in a small-bore 9.4 T MRI.

An optically coupled system for quantitative monitoring of MRI-induced RF currents into long conductors.

PubMed

Zanchi, Marta G; Venook, Ross; Pauly, John M; Scott, Greig C

2010-01-01

The currents induced in long conductors such as guidewires by the radio-frequency (RF) field in magnetic resonance imaging (MRI) are responsible for potentially dangerous heating of surrounding media, such as tissue. This paper presents an optically coupled system with the potential to quantitatively measure the RF currents induced on these conductors. The system uses a self shielded toroid transducer and active circuitry to modulate a high speed light-emitting-diode transmitter. Plastic fiber guides the light to a photodiode receiver and transimpedance amplifier. System validation included a series of experiments with bare wires that compared wire tip heating by fluoroptic thermometers with the RF current sensor response. Validations were performed on a custom whole body 64 MHz birdcage test platform and on a 1.5 T MRI scanner. With this system, a variety of phenomena were demonstrated including cable trap current attenuation, lossy dielectric Q-spoiling and even transverse electromagnetic wave node patterns. This system should find applications in studies of MRI RF safety for interventional devices such as pacemaker leads, and guidewires. In particular, variations of this device could potentially act as a realtime safety monitor during MRI guided interventions.

Quantifying Trust, Distrust, and Suspicion in Human-System Interactions

DTIC Science & Technology

2015-10-26

devices which require subjects to lie in restricted positions ( fMRI ), or to drink hazardous materials (PET), EEG and fNIRS can non-invasively measure... fMRI . Since fNIRS and fMRI both measure elements of the Blood Oxygen Level Dependent (BOLD) signal. Researchers have recently explored the...response inhibition load, verbal working memory load, and spatial working memory load [1, 7]. We have also successfully localized brain regions such as

[Devic disease: a rare cause of retrobulbar optic neuritis: a case report].

PubMed

Sempińska-Szewczyk, J; Weglewski, A; Juryńczyk, J; Cybulska, B

2000-01-01

A case of 58-year-old woman with recurrent retrobulbar optic neuritis (ron) and transverse myelitis is presented. The patient was admitted to the opthalmology unit because of acute right retrobulbar optic neuritis. In 1997 she complained of left retrobulbar optic neuritis. One year later transverse myelitis of thoracic spine with spastic paraparesis occurred. MRI examination showed T2 hyperintensive focus in the thoracic spine (Th8-Th9, probably demyelinisation). Nowadays MRI examination of the optic nerves and brain showed demyelinisation focus in the right optic nerve. There was no pathological changes in the brain. The diagnosis of Devic disease was established. Treatment with intravenous methyloprednisolon was administered with slight improvement. The pathology and clinical course of Devic disease are discussed.

Regulatory perspectives and research activities at the FDA on the use of phantoms with in vivo diagnostic devices

NASA Astrophysics Data System (ADS)

Agrawal, Anant; Gavrielides, Marios A.; Weininger, Sandy; Chakrabarti, Kish; Pfefer, Joshua

2008-02-01

For a number of years, phantoms have been used to optimize device parameters and validate performance in the primary medical imaging modalities (CT, MRI, PET/SPECT, ultrasound). Furthermore, the FDA under the Mammography Quality Standards Act (MQSA) requires image quality evaluation of mammography systems using FDA-approved phantoms. The oldest quantitative optical diagnostic technology, pulse oximetry, also benefits from the use of active phantoms known as patient simulators to validate certain performance characteristics under different clinically-relevant conditions. As such, guidance provided by the FDA to its staff and to industry on the contents of pre-market notification and approval submissions includes suggestions on how to incorporate the appropriate phantoms in establishing device effectiveness. Research at the FDA supports regulatory statements on the use of phantoms by investigating how phantoms can be designed, characterized, and utilized to determine critical device performance characteristics. These examples provide a model for how novel techniques in the rapidly growing field of optical diagnostics can use phantoms during pre- and post-market regulatory testing.

Advanced magnetic resonance imaging of neurodegenerative diseases.

PubMed

Agosta, Federica; Galantucci, Sebastiano; Filippi, Massimo

2017-01-01

Magnetic resonance imaging (MRI) is playing an increasingly important role in the study of neurodegenerative diseases, delineating the structural and functional alterations determined by these conditions. Advanced MRI techniques are of special interest for their potential to characterize the signature of each neurodegenerative condition and aid both the diagnostic process and the monitoring of disease progression. This aspect will become crucial when disease-modifying (personalized) therapies will be established. MRI techniques are very diverse and go from the visual inspection of MRI scans to more complex approaches, such as manual and automatic volume measurements, diffusion tensor MRI, and functional MRI. All these techniques allow us to investigate the different features of neurodegeneration. In this review, we summarize the most recent advances concerning the use of MRI in some of the most important neurodegenerative conditions, putting an emphasis on the advanced techniques.

Arm MRI scan

MedlinePlus

... MRI and often available in the emergency room. Alternative Names MRI - arm; Wrist MRI; MRI - wrist; Elbow ... any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should ...

Transabdominal high-intensity focused ultrasound therapy of the prostate and determination of the protective effect of rectal cooling: an experimental study using canine prostates.

PubMed

Yoo, Dong Hyun; Cho, Jeong Yeon; Kwak, Cheol; Lee, Jae Young; Moon, Kyung Chul; Kim, Seung Hyup

2013-08-01

The purpose of this study was to report our initial experience with transabdominal high-intensity focused ultrasound (HIFU) therapy of the canine prostate and to determine the protective effect of rectal cooling during HIFU therapy. Fifteen male dogs underwent transabdominal HIFU therapy of the prostate. Transabdominal HIFU was performed on 9 dogs without using a rectal cooling device, and the remaining 6 dogs underwent transabdominal HIFU with introduction of the rectal cooling device. Magnetic resonance imaging (MRI) was performed before, immediately after, and 1 week after the HIFU procedure. Rectal changes on MRI were classified into 4 grades (grades 0-3), and a comparison of the rectal change grades on MRI between the two groups was performed with the Mann-Whitney U test. The procedure failed for the first dog because of inadequate skin preparation. Of the remaining 14 dogs (8 without rectal cooling and 6 with rectal cooling), 4 showed focal signal changes in the prostate. The average rectal change grades on immediate postprocedural MRI were 2.63 for the non-rectal cooling group and 1.17 for the rectal cooling group (P = .0216). On 1-week follow-up MRI, the average grades were 1.20 for the non-rectal cooling group and 0.33 for the rectal cooling group (P = .1956). Transabdominal HIFU of the canine prostate was technically feasible, but the effect was limited because of anatomic and physiologic factors of the canine prostate. The rectal cooling device seems to have a protective effect on the rectum during the transabdominal HIFU procedure.

An RF dosimeter for independent SAR measurement in MRI scanners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian, Di; Bottomley, Paul A.; El-Sharkawy, AbdEl-Monem M.

2013-12-15

Purpose: The monitoring and management of radio frequency (RF) exposure is critical for ensuring magnetic resonance imaging (MRI) safety. Commercial MRI scanners can overestimate specific absorption rates (SAR) and improperly restrict clinical MRI scans or the application of new MRI sequences, while underestimation of SAR can lead to tissue heating and thermal injury. Accurate scanner-independent RF dosimetry is essential for measuring actual exposure when SAR is critical for ensuring regulatory compliance and MRI safety, for establishing RF exposure while evaluating interventional leads and devices, and for routine MRI quality assessment by medical physicists. However, at present there are no scanner-independentmore » SAR dosimeters. Methods: An SAR dosimeter with an RF transducer comprises two orthogonal, rectangular copper loops and a spherical MRI phantom. The transducer is placed in the magnet bore and calibrated to approximate the resistive loading of the scanner's whole-body birdcage RF coil for human subjects in Philips, GE and Siemens 3 tesla (3T) MRI scanners. The transducer loop reactances are adjusted to minimize interference with the transmit RF field (B{sub 1}) at the MRI frequency. Power from the RF transducer is sampled with a high dynamic range power monitor and recorded on a computer. The deposited power is calibrated and tested on eight different MRI scanners. Whole-body absorbed power vs weight and body mass index (BMI) is measured directly on 26 subjects. Results: A single linear calibration curve sufficed for RF dosimetry at 127.8 MHz on three different Philips and three GE 3T MRI scanners. An RF dosimeter operating at 123.2 MHz on two Siemens 3T scanners required a separate transducer and a slightly different calibration curve. Measurement accuracy was ∼3%. With the torso landmarked at the xiphoid, human adult whole‑body absorbed power varied approximately linearly with patient weight and BMI. This indicates that whole-body torso SAR is on average independent of the imaging subject, albeit with fluctuations. Conclusions: Our 3T RF dosimeter and transducers accurately measure RF exposure in body-equivalent loads and provide scanner-independent assessments of whole-body RF power deposition for establishing safety compliance useful for MRI sequence and device testing.« less

MR-guided endovascular interventions: a comprehensive review on techniques and applications.

PubMed

Kos, Sebastian; Huegli, Rolf; Bongartz, Georg M; Jacob, Augustinus L; Bilecen, Deniz

2008-04-01

The magnetic resonance (MR) guidance of endovascular interventions is probably one of the greatest challenges of clinical MR research. MR angiography is not only an imaging tool for the vasculature but can also simultaneously depict high tissue contrast, including the differentiation of the vascular wall and perivascular tissues, as well as vascular function. Several hurdles had to be overcome to allow MR guidance for endovascular interventions. MR hardware and sequence design had to be developed to achieve acceptable patient access and to allow real-time or near real-time imaging. The development of interventional devices, both applicable and safe for MR imaging (MRI), was also mandatory. The subject of this review is to summarize the latest developments in real-time MRI hardware, MRI, visualization tools, interventional devices, endovascular tracking techniques, actual applications and safety issues.

An MRI-Guided Telesurgery System Using a Fabry-Perot Interferometry Force Sensor and a Pneumatic Haptic Device.

PubMed

Su, Hao; Shang, Weijian; Li, Gang; Patel, Niravkumar; Fischer, Gregory S

2017-08-01

This paper presents a surgical master-slave teleoperation system for percutaneous interventional procedures under continuous magnetic resonance imaging (MRI) guidance. The slave robot consists of a piezoelectrically actuated 6-degree-of-freedom (DOF) robot for needle placement with an integrated fiber optic force sensor (1-DOF axial force measurement) using the Fabry-Perot interferometry (FPI) sensing principle; it is configured to operate inside the bore of the MRI scanner during imaging. By leveraging the advantages of pneumatic and piezoelectric actuation in force and position control respectively, we have designed a pneumatically actuated master robot (haptic device) with strain gauge based force sensing that is configured to operate the slave from within the scanner room during imaging. The slave robot follows the insertion motion of the haptic device while the haptic device displays the needle insertion force as measured by the FPI sensor. Image interference evaluation demonstrates that the telesurgery system presents a signal to noise ratio reduction of less than 17% and less than 1% geometric distortion during simultaneous robot motion and imaging. Teleoperated needle insertion and rotation experiments were performed to reach 10 targets in a soft tissue-mimicking phantom with 0.70 ± 0.35 mm Cartesian space error.

High ventricular lead impedance of a DDD pacemaker after cranial magnetic resonance imaging.

PubMed

Baser, Kazim; Guray, Umit; Durukan, Mine; Demirkan, Burcu

2012-09-01

Management of electromagnetic interference in the form of magnetic resonance imaging (MRI) in patients with pacemakers (PMs) may be challenging. Serious consequences, especially in PM-dependent patients, may be encountered. Changes in device programming, asynchronous pacing, heating of the lead tip(s), and increased thresholds or even device dislocation may be experienced. We report of a patient with a DDD PM who underwent an emergent MRI, after which there was an increase in ventricular impedance as well as increased cardiac biomarkers. ©2011, The Authors. Journal compilation ©2012 Wiley Periodicals, Inc.

[Low-field magnetic resonance imaging for rheumatoid arthritis].

PubMed

Ostendorf, B; Edelmann, E; Kellner, H; Scherer, A

2010-02-01

Magnetic resonance imaging (MRI) as a cross-sectional imaging procedure allows a three-dimensional representation of musculature, ligaments, tendons, capsules, synovial membranes, bones and cartilage with high resolution quality. An activity assessment is further possible by application of a contrast medium (gadolinium-DTPA) to differentiate between active and chronic inflammatory processes. Evidence of a bone marrow edema detected by MRI in patients with rheumatoid arthritis (RA) can be interpreted as a prognostic and predictive factor for the development of bone erosions. On the basis of these advantages MRI is being employed more and more in the early diagnosis of inflammatory joint diseases. Semi-quantitative scores for analysis and grading of findings have already been developed and are in clinical use. Because MRI technical performances are invariably reproducible they can be practically retrieved in the course of examination which is particularly relevant in rheumatology. Therapy response or progression can thus be adequately displayed. Open, dedicated low-field MRI with a low signal strength of 0.2 Tesla (T) has been known since the 90s and now represents new MRI examination options in rheumatology. Smaller devices with lower acquisition and maintenance expenses as well as considerably more convenience due to the device itself result in a higher subjective acceptability by the patients as well as objectively more data records of low-field MRI scans of RA, which underline the significance of this new technical method. The German Society for Rheumatology (DGRh), represented by the Committee for "Diagnostic Imaging", meets this development with the release of recommendations and standards for the procedures of low-field MRI and their scoring and summarizes the most important technical data and information on clinical indications.

The Potential for an Enhanced Role for MRI in Radiation-therapy Treatment Planning

PubMed Central

Metcalfe, P.; Liney, G. P.; Holloway, L.; Walker, A.; Barton, M.; Delaney, G. P.; Vinod, S.; Tomé, W.

2013-01-01

The exquisite soft-tissue contrast of magnetic resonance imaging (MRI) has meant that the technique is having an increasing role in contouring the gross tumor volume (GTV) and organs at risk (OAR) in radiation therapy treatment planning systems (TPS). MRI-planning scans from diagnostic MRI scanners are currently incorporated into the planning process by being registered to CT data. The soft-tissue data from the MRI provides target outline guidance and the CT provides a solid geometric and electron density map for accurate dose calculation on the TPS computer. There is increasing interest in MRI machine placement in radiotherapy clinics as an adjunct to CT simulators. Most vendors now offer 70 cm bores with flat couch inserts and specialised RF coil designs. We would refer to these devices as MR-simulators. There is also research into the future application of MR-simulators independent of CT and as in-room image-guidance devices. It is within the background of this increased interest in the utility of MRI in radiotherapy treatment planning that this paper is couched. The paper outlines publications that deal with standard MRI sequences used in current clinical practice. It then discusses the potential for using processed functional diffusion maps (fDM) derived from diffusion weighted image sequences in tracking tumor activity and tumor recurrence. Next, this paper reviews publications that describe the use of MRI in patient-management applications that may, in turn, be relevant to radiotherapy treatment planning. The review briefly discusses the concepts behind functional techniques such as dynamic contrast enhanced (DCE), diffusion-weighted (DW) MRI sequences and magnetic resonance spectroscopic imaging (MRSI). Significant applications of MR are discussed in terms of the following treatment sites: brain, head and neck, breast, lung, prostate and cervix. While not yet routine, the use of apparent diffusion coefficient (ADC) map analysis indicates an exciting future application for functional MRI. Although DW-MRI has not yet been routinely used in boost adaptive techniques, it is being assessed in cohort studies for sub-volume boosting in prostate tumors. PMID:23617289

Design and simulation of a 800 Mbit/s data link for magnetic resonance imaging wearables.

PubMed

Vogt, Christian; Buthe, Lars; Petti, Luisa; Cantarella, Giuseppe; Munzenrieder, Niko; Daus, Alwin; Troster, Gerhard

2015-08-01

This paper presents the optimization of electronic circuitry for operation in the harsh electro magnetic (EM) environment during a magnetic resonance imaging (MRI) scan. As demonstrator, a device small enough to be worn during the scan is optimized. Based on finite element method (FEM) simulations, the induced current densities due to magnetic field changes of 200 T s(-1) were reduced from 1 × 10(10) A m(-2) by one order of magnitude, predicting error-free operation of the 1.8V logic employed. The simulations were validated using a bit error rate test, which showed no bit errors during a MRI scan sequence. Therefore, neither the logic, nor the utilized 800 Mbit s(-1) low voltage differential swing (LVDS) data link of the optimized wearable device were significantly influenced by the EM interference. Next, the influence of ferro-magnetic components on the static magnetic field and consequently the image quality was simulated showing a MRI image loss with approximately 2 cm radius around a commercial integrated circuit of 1×1 cm(2). This was successively validated by a conventional MRI scan.

Positron emission tomography/magnetic resonance imaging (PET/MRI): An update and initial experience at HC-FMUSP.

PubMed

Queiroz, Marcelo A; Barbosa, Felipe de Galiza; Buchpiguel, Carlos Alberto; Cerri, Giovanni Guido

2018-01-01

The new technology of PET/MRI is a prototype of hybrid imaging, allowing for the combination of molecular data from PET scanning and morphofunctional information derived from MRI scanning. Recent advances regarding the technical aspects of this device, especially after the development of MRI-compatible silicon photomultipliers of PET, permitted an increase in the diagnostic performance of PET/MRI translated into dose reduction and higher imaging quality. Among several clinical applications, PET/MRI gains ground initially in oncology, where MRI per se plays an essential role in the assessment of primary tumors (which is limited in the case of PET/CT), including prostate, rectal and gynecological tumors. On the other hand, the evaluation of the lungs remains an enigma although new MRI sequences are being designed to overcome this. More clinical indications of PET/MRI are seen in the fields of neurology, cardiology and inflammatory processes, and the use of PET/MRI also opens perspectives for pediatric populations as it involves very low radiation exposure. Our review aimed to highlight the current indications of PET/MRI and discuss the challenges and perspectives of PET/MRI at HC-FMUSP.

Improved Hardware for Higher Spatial Resolution Strain-ENCoded (SENC) Breast MRI for Strain Measurements

PubMed Central

Harouni, Ahmed A.; Hossain, Jakir; Jacobs, Michael A.; Osman, Nael F.

2012-01-01

Introduction Early detection of breast lesions using mammography has resulted in lower mortality-rates. However, some breast lesions are mammography occult and magnetic resonance imaging (MRI) is recommended, but has lower specificity. It is possible to achieve higher specificity by using Strain-ENCoded (SENC) MRI and/or magnetic resonance elastography(MRE). SENC breast MRI can measure the strain properties of breast tissue. Similarly, MRE is used to measure elasticity (i.e., shear stiffness) of different tissue compositions interrogating the tissue mechanical properties. Reports have shown that malignant tumors are 3–13 times stiffer than normal tissue and benign tumors. Methods We have developed a Strain-ENCoded (SENC) breast hardware device capable of periodically compressing the breast, thus allowing for longer scanning time and measuring the strain characteristics of breast tissue. This hardware enabled us to use SENC MRI with high spatial resolution (1×1×5mm3) instead of Fast SENC(FSENC). Simple controls and multiple safety measures were added to ensure accurate, repeatable and safe in-vivo experiments. Results Phantom experiments showed that SENC breast MRI has higher SNR and CNR than FSENC under different scanning resolutions. Finally, the SENC breast device reproducibility measurements resulted in a difference of less than one mm with a 1% strain difference. Conclusion SENC breast MR images have higher SNR and CNR than FSENC images. Thus, combining SENC breast strain measurements with diagnostic breast MRI to differentiate benign from malignant lesions could potentially increase the specificity of diagnosis in the clinical setting. PMID:21440464

Design considerations for a novel MRI compatible manipulator for prostate cryoablation.

PubMed

Abdelaziz, S; Esteveny, L; Renaud, P; Bayle, B; Barbé, L; De Mathelin, M; Gangi, A

2011-11-01

Prostate carcinoma is a commonly diagnosed cancer in men. Nonsurgical treatment of early stage prostate cancer is an important alternative. The use of MRI for tumor cryoablation is of particular interest: it offers lower morbidity compared with other localized techniques. However, the current manual procedure is very time-consuming and has limited accuracy. A novel robotic assistant is therefore designed for prostate cancer cryotherapy treatment under MRI guidance to improve efficiency and accuracy. Gesture definition was achieved based on actions of interventional radiologists at University Hospital of Strasbourg. A transperineal approach with a semiautonomous prostatic cryoprobe localization procedure was developed where the needle axis is automatically positioned before manual insertion. The workflow was developed simultaneously with the robotic assistant used for needle positioning. The design and the associated workflow of an original wire-driven manipulator were developed. The device is compact and has a low weight: its overall dimensions in the scanner are 100 × 100 × 40 mm with a weight of 120 g. Very good MRI compatibility was demonstrated. A novel cryoablation procedure based on the use of a robotic assistant is proposed. The device design was presented with demonstration of MRI compatibility. Further developments include automatic registration and in vivo experimental testing.

A Simple fMRI Compatible Robotic Stimulator to Study the Neural Mechanisms of Touch and Pain.

PubMed

Riillo, F; Bagnato, C; Allievi, A G; Takagi, A; Fabrizi, L; Saggio, G; Arichi, T; Burdet, E

2016-08-01

This paper presents a simple device for the investigation of the human somatosensory system with functional magnetic imaging (fMRI). PC-controlled pneumatic actuation is employed to produce innocuous or noxious mechanical stimulation of the skin. Stimulation patterns are synchronized with fMRI and other relevant physiological measurements like electroencephalographic activity and vital physiological parameters. The system allows adjustable regulation of stimulation parameters and provides consistent patterns of stimulation. A validation experiment demonstrates that the system safely and reliably identifies clusters of functional activity in brain regions involved in the processing of pain. This new device is inexpensive, portable, easy-to-assemble and customizable to suit different experimental requirements. It provides robust and consistent somatosensory stimulation, which is of crucial importance to investigating the mechanisms of pain and its strong connection with the sense of touch.

Deep brain stimulation with a pre-existing cochlear implant: Surgical technique and outcome.

PubMed

Eddelman, Daniel; Wewel, Joshua; Wiet, R Mark; Metman, Leo V; Sani, Sepehr

2017-01-01

Patients with previously implanted cranial devices pose a special challenge in deep brain stimulation (DBS) surgery. We report the implantation of bilateral DBS leads in a patient with a cochlear implant. Technical nuances and long-term interdevice functionality are presented. A 70-year-old patient with advancing Parkinson's disease and a previously placed cochlear implant for sensorineural hearing loss was referred for placement of bilateral DBS in the subthalamic nucleus (STN). Prior to DBS, the patient underwent surgical removal of the subgaleal cochlear magnet, followed by stereotactic MRI, frame placement, stereotactic computed tomography (CT), and merging of imaging studies. This technique allowed for successful computational merging, MRI-guided targeting, and lead implantation with acceptable accuracy. Formal testing and programming of both the devices were successful without electrical interference. Successful DBS implantation with high resolution MRI-guided targeting is technically feasible in patients with previously implanted cochlear implants by following proper precautions.

MRI in ocular drug delivery

PubMed Central

Li, S. Kevin; Lizak, Martin J.; Jeong, Eun-Kee

2008-01-01

Conventional pharmacokinetic methods for studying ocular drug delivery are invasive and cannot be conveniently applied to humans. The advancement of MRI technology has provided new opportunities in ocular drug-delivery research. MRI provides a means to non-invasively and continuously monitor ocular drug-delivery systems with a contrast agent or compound labeled with a contrast agent. It is a useful technique in pharmacokinetic studies, evaluation of drug-delivery methods, and drug-delivery device testing. Although the current status of the technology presents some major challenges to pharmaceutical research using MRI, it has a lot of potential. In the past decade, MRI has been used to examine ocular drug delivery via the subconjunctival route, intravitreal injection, intrascleral injection to the suprachoroidal space, episcleral and intravitreal implants, periocular injections, and ocular iontophoresis. In this review, the advantages and limitations of MRI in the study of ocular drug delivery are discussed. Different MR contrast agents and MRI techniques for ocular drug-delivery research are compared. Ocular drug-delivery studies using MRI are reviewed. PMID:18186077

A novel manipulation method of human body ownership using an fMRI-compatible master-slave system.

PubMed

Hara, Masayuki; Salomon, Roy; van der Zwaag, Wietske; Kober, Tobias; Rognini, Giulio; Nabae, Hiroyuki; Yamamoto, Akio; Blanke, Olaf; Higuchi, Toshiro

2014-09-30

Bodily self-consciousness has become an important topic in cognitive neuroscience aiming to understand how the brain creates a unified sensation of the self in a body. Specifically, full body illusion (FBI) in which changes in bodily self-consciousness are experimentally introduced by using visual-tactile stimulation has led to improve understanding of these mechanisms. This paper introduces a novel approach to the classic FBI paradigm using a robotic master-slave system which allows us to examine interactions between action and the sense of body ownership in behavioral and MRI experiments. In the proposed approach, the use of the robotic master-slave system enables unique stimulation in which experimental participants can administer tactile cues on their own back using active self-touch. This active self-touch has never been employed in FBI experiments and it allows to test the role of sensorimotor integration and agency (the feeling of control over our actions) in FBI paradigms. The objective of this study is to propose a robotic-haptic platform allowing a new FBI paradigm including the active self-touch in MRI environments. This paper, first, describes the design concept and the performance of the prototype device in the fMRI environment (for 3T and 7T MRI scanners). In addition, the prototype device is applied to a classic FBI experiment, and we verify that the use of the prototype device succeeded in inducing the FBI. These results indicate that the proposed approach has a potential to drive advances in our understanding of human body ownership and agency by allowing novel manipulation and paradigms. Copyright © 2014 Elsevier B.V. All rights reserved.

Navigated MRI-guided liver biopsies in a closed-bore scanner: experience in 52 patients.

PubMed

Moche, Michael; Heinig, Susann; Garnov, Nikita; Fuchs, Jochen; Petersen, Tim-Ole; Seider, Daniel; Brandmaier, Philipp; Kahn, Thomas; Busse, Harald

2016-08-01

To evaluate clinical effectiveness and diagnostic efficiency of a navigation device for MR-guided biopsies of focal liver lesions in a closed-bore scanner. In 52 patients, 55 biopsies were performed. An add-on MR navigation system with optical instrument tracking was used for image guidance and biopsy device insertion outside the bore. Fast control imaging allowed visualization of the true needle position at any time. The biopsy workflow and procedure duration were recorded. Histological analysis and clinical course/outcome were used to calculate sensitivity, specificity and diagnostic accuracy. Fifty-four of 55 liver biopsies were performed successfully with the system. No major and four minor complications occurred. Mean tumour size was 23 ± 14 mm and the skin-to-target length ranged from 22 to 177 mm. In 39 cases, access path was double oblique. Sensitivity, specificity and diagnostic accuracy were 88 %, 100 % and 92 %, respectively. The mean procedure time was 51 ± 12 min, whereas the puncture itself lasted 16 ± 6 min. On average, four control scans were taken. Using this navigation device, biopsies of poorly visible and difficult accessible liver lesions could be performed safely and reliably in a closed-bore MRI scanner. The system can be easily implemented in clinical routine workflow. • Targeted liver biopsies could be reliably performed in a closed-bore MRI. • The navigation system allows for image guidance outside of the scanner bore. • Assisted MRI-guided biopsies are helpful for focal lesions with a difficult access. • Successful integration of the method in clinical workflow was shown. • Subsequent system installation in an existing MRI environment is feasible.

Static magnetic susceptibility of radiopaque NiTiPt and NiTiEr

NASA Astrophysics Data System (ADS)

Chovan, Drahomír; Gandhi, Abbasi; Butler, James; Tofail, Syed A. M.

2018-04-01

Magnetic properties of metallic alloys used in biomedical industry are important for the magnetic resonance imaging (MRI). If the alloys were to be used for long term implants or as guiding devices, safety of the patient as well as the medical staff has to be ensured. Strong response to the external magnetic field can cause mechanical damage to the patients body. In this paper we present magnetic susceptibility of nickel rich, ternary NiTiPt and NiTiEr to static magnetic field. We show that the magnetic susceptibility of these radiopaque alloys has values in low paramagnetic region comparable to the binary nickel-titanium. Furthermore, we studied the effect of the thermal and mechanical treatments on magnetic properties. Despite deviation from linear M (H) treated samples spanning small region around H = 0 , the linearity of the M (H) and χ =d M /d H values suggest that these ternary alloys are safe to use under MRI conditions.

Pelvis MRI scan

MedlinePlus

... and most often available in the emergency room. Alternative Names MRI - pelvis; MRI - hips; Pelvic MRI with ... any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should ...

A variable torque motor compatible with magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Roeck, W. W.; Ha, S.-H.; Farmaka, S.; Nalcioglu, O.

2009-04-01

High magnetic fields used in magnetic resonance imaging (MRI) do not allow the employment of conventional motors due to various incompatibility issues. This paper reports on a new motor that can operate in or near high field magnets used for MRI. The motor was designed to be operational with the MRI equipment and could be used in a rotating imaging gantry inside the magnet designed for dual modality imaging. Furthermore, it could also be used for image guided robotic interventional procedures inside a MRI system if so desired. The prototype motor was developed using magnetic resonance (MR) compatible materials, and its functionality with MR imaging was evaluated experimentally by measuring the performance of the motor and its effect on the MR image quality. Since in our application, namely, single photon emission tomography, the motor has to perform precise stepping of the gantry in small angular steps the most important parameter is the start-up torque. The experimental results showed that the motor has a start-up torque up to 1.37 Nm and rotates at 196 rpm when a constant voltage difference of 12 V is applied at a magnetic field strength of 1 T. The MR image quality was quantified by measuring the signal-to-noise of images acquired under different conditions. The results presented here indicate that the motor is MR compatible and could be used for rotating an imaging gantry or a surgical device inside the magnet.

Monitoring local heating around an interventional MRI antenna with RF radiometry

PubMed Central

Ertürk, M. Arcan; El-Sharkawy, AbdEl-Monem M.; Bottomley, Paul A.

2015-01-01

Purpose: Radiofrequency (RF) radiometry uses thermal noise detected by an antenna to measure the temperature of objects independent of medical imaging technologies such as magnetic resonance imaging (MRI). Here, an active interventional MRI antenna can be deployed as a RF radiometer to measure local heating, as a possible new method of monitoring device safety and thermal therapy. Methods: A 128 MHz radiometer receiver was fabricated to measure the RF noise voltage from an interventional 3 T MRI loopless antenna and calibrated for temperature in a uniformly heated bioanalogous gel phantom. Local heating (ΔT) was induced using the antenna for RF transmission and measured by RF radiometry, fiber-optic thermal sensors, and MRI thermometry. The spatial thermal sensitivity of the antenna radiometer was numerically computed using a method-of-moment electric field analyses. The gel’s thermal conductivity was measured by MRI thermometry, and the localized time-dependent ΔT distribution computed from the bioheat transfer equation and compared with radiometry measurements. A “H-factor” relating the 1 g-averaged ΔT to the radiometric temperature was introduced to estimate peak temperature rise in the antenna’s sensitive region. Results: The loopless antenna radiometer linearly tracked temperature inside a thermally equilibrated phantom up to 73 °C to within ±0.3 °C at a 2 Hz sample rate. Computed and MRI thermometric measures of peak ΔT agreed within 13%. The peak 1 g-average temperature was H = 1.36 ± 0.02 times higher than the radiometric temperature for any media with a thermal conductivity of 0.15–0.50 (W/m)/K, indicating that the radiometer can measure peak 1 g-averaged ΔT in physiologically relevant tissue within ±0.4 °C. Conclusions: Active internal MRI detectors can serve as RF radiometers at the MRI frequency to provide accurate independent measures of local and peak temperature without the artifacts that can accompany MRI thermometry or the extra space needed to accommodate alternative thermal transducers. A RF radiometer could be integrated in a MRI scanner to permit “self-monitoring” for assuring device safety and/or monitoring delivery of thermal therapy. PMID:25735295

A survey on abnormal uterine bleeding among radiographers with frequent MRI exposure using intrauterine contraceptive devices.

PubMed

Huss, A; Schaap, K; Kromhout, H

2018-02-01

Based on a previous case report of menometrorrhagia (prolonged/excessive uterine bleeding, occurring at irregular and/or frequent intervals) in MRI workers with intrauterine devices (IUDs), it was evaluated whether this association could be confirmed. A survey was performed among 381 female radiographers registered with their national association. Logistic regression was used to analyze associations of abnormal uterine bleeding with the frequency of working with MRI scanners, presence near the scanner/in the scanner room during image acquisition, and with scanner strength or type. A total of 68 women reported using IUDs, and 72 reported abnormal uterine bleeding. Compared with unexposed women not using IUDs, the odds ratio in women with IUDs working with MRI scanners was 2.09 (95% confidence interval 0.83-3.66). Associations were stronger if women working with MRI reported being present during image acquisition (odds ratio 3.43, 95% CI 1.26-9.34). Associations with scanner strength or type were not consistent. Radiographers using IUDs who are occupationally exposed to stray fields from MRI scanners report abnormal uterine bleeding more often than their co-workers without an IUD, or nonexposed co-workers with an IUD. In particular, radiographers present inside the scanner room during image acquisition showed an increased risk. Magn Reson Med 79:1083-1089, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Design of an fMRI-compatible optical touch stripe based on frustrated total internal reflection.

PubMed

Jarrahi, Behnaz; Wanek, Johann

2014-01-01

Previously we developed a low-cost, multi-configurable handheld response system, using a reflective-type intensity modulated fiber-optic sensor (FOS) to accurately gather participants' behavioral responses during functional magnetic resonance imaging (fMRI). Inspired by the popularity and omnipresence of the fingertip-based touch sensing user interface devices, in this paper we present the design of a prototype fMRI-compatible optical touch stripe (OTS) as an alternative configuration. The prototype device takes advantage of a proven frustrated total internal reflection (FTIR) technique. By using a custom-built wedge-shaped optically transparent acrylic prism as an optical waveguide, and a plano-concave lens to provide the required light beam profile, the position of a fingertip touching the surface of the wedge prism can be determined from the deflected light beams that become trapped within the prism by total internal reflection. To achieve maximum sensitivity, the optical design of the wedge prism and lens were optimized through a series of light beam simulations using WinLens 3D Basic software suite. Furthermore, OTS performance and MRI-compatibility were assessed on a 3.0 Tesla MRI scanner running echo planar imaging (EPI) sequences. The results show that the OTS can detect a touch signal at high spatial resolution (about 0.5 cm), and is well suited for use within the MRI environment with average time-variant signal-to-noise ratio (tSNR) loss < 3%.

[Principles of MR-guided interventions, surgery, navigation, and robotics].

PubMed

Melzer, A

2010-08-01

The application of magnetic resonance imaging (MRI) as an imaging technique in interventional and surgical techniques provides a new dimension of soft tissue-oriented precise procedures without exposure to ionizing radiation and nephrotoxic allergenic, iodine-containing contrast agents. The technical capabilities of MRI in combination with interventional devices and systems, navigation, and robotics are discussed.

MR-guided focused ultrasound robot for performing experiments on large animals

NASA Astrophysics Data System (ADS)

Mylonas, N.; Damianou, C.

2011-09-01

Introduction: In this paper an experimental MRI-guided focused ultrasound robot for large animals is presented. Materials and methods: A single element spherically focused transducer of 4 cm diameter, focusing at 10 cm and operating at 1 MHz was used. A positioning device was developed in order to scan the ultrasound transducer for performing MR-guided focused ultrasound experiments in large animals such as pig, sheep and dog. The positioning device incorporates only MRI compatible materials such as piezoelectric motors, Acrylonitrile Butadiene Styrene (ABS) plastic, brass screws, and brass pulleys. The system is manufactured automatically using a rapid prototyping system. Results: The system was tested successfully in a number of animals for various tasks (creation of single lesions, creation of overlapping lesions, and MR compatibility). Conclusions: A simple, cost effective, portable positioning device has been developed which can be used in virtually any clinical MRI scanner since it can be sited on the scanner's table. The propagation of HIFU can be via a lateral or superior-inferior approach. This system has the potential to be marketed as a cost effective solution for performing experiments in small and large animals.

Low dose intranasal oxytocin delivered with Breath Powered device dampens amygdala response to emotional stimuli: A peripheral effect-controlled within-subjects randomized dose-response fMRI trial.

PubMed

Quintana, Daniel S; Westlye, Lars T; Alnæs, Dag; Rustan, Øyvind G; Kaufmann, Tobias; Smerud, Knut T; Mahmoud, Ramy A; Djupesland, Per G; Andreassen, Ole A

2016-07-01

It is unclear if and how exogenous oxytocin (OT) reaches the brain to improve social behavior and cognition and what is the optimal dose for OT response. To better understand the delivery routes of intranasal OT administration to the brain and the dose-response, we compared amygdala response to facial stimuli by means of functional magnetic resonance imaging (fMRI) in four treatment conditions, including two different doses of intranasal OT using a novel Breath Powered device, intravenous (IV) OT, which provided similar concentrations of blood plasma OT, and placebo. We adopted a randomized, double-blind, double-dummy, crossover design, with 16 healthy male adults administering a single-dose of these four treatments. We observed a treatment effect on right amygdala activation during the processing of angry and happy face stimuli, with pairwise comparisons revealing reduced activation after the 8IU low dose intranasal treatment compared to placebo. These data suggest the dampening of amygdala activity in response to emotional stimuli occurs via direct intranasal delivery pathways rather than across the blood-brain barrier via systemically circulating OT. This trial is registered at the U.S. National Institutes of Health clinical trial registry (www.clinicaltrials.gov; NCT01983514) and as EudraCT no. 2013-001608-12. Copyright © 2016 Elsevier Ltd. All rights reserved.

Optical switches and switching methods

DOEpatents

Doty, Michael

2008-03-04

A device and method for collecting subject responses, particularly during magnetic imaging experiments and testing using a method such as functional MRI. The device comprises a non-metallic input device which is coupled via fiber optic cables to a computer or other data collection device. One or more optical switches transmit the subject's responses. The input device keeps the subject's fingers comfortably aligned with the switches by partially immobilizing the forearm, wrist, and/or hand of the subject. Also a robust nonmetallic switch, particularly for use with the input device and methods for optical switching.

Device localization and dynamic scan plane selection using a wireless MRI detector array

PubMed Central

Riffe, Matthew J.; Yutzy, Stephen R.; Jiang, Yun; Twieg, Michael D.; Blumenthal, Colin J.; Hsu, Daniel P.; Pan, Li; Gilson, Wesley D.; Sunshine, Jeffrey L.; Flask, Christopher A.; Duerk, Jeffrey L.; Nakamoto, Dean; Gulani, Vikas; Griswold, Mark A.

2013-01-01

Purpose A prototype wireless guidance device using single sideband amplitude modulation (SSB) is presented for a 1.5T MRI system. Methods The device contained three fiducial markers each mounted to an independent receiver coil equipped with wireless SSB technology. Acquiring orthogonal projections of these markers determined the position and orientation of the device, which was used to define the scan plane for a subsequent image acquisition. Device localization and scan plane update required approximately 30 ms, so it could be interleaved with high temporal resolution imaging. Since the wireless device is used for localization and doesn’t require full imaging capability, the design of the SSB wireless system was simplified by allowing an asynchronous clock between the transmitter and receiver. Results When coupled to a high readout bandwidth, the error caused by the lack of a shared frequency reference was quantified to be less than one pixel (0.78 mm) in the projection acquisitions. Image-guidance with the prototype was demonstrated with a phantom where a needle was successfully guided to a target and contrast was delivered. Conclusion The feasibility of active tracking with a wireless detector array is demonstrated. Wireless arrays could be incorporated into devices to assist in image-guided procedures. PMID:23900921

An fMRI compatible wrist robotic interface to study brain development in neonates.

PubMed

Allievi, A G; Melendez-Calderon, A; Arichi, T; Edwards, A D; Burdet, E

2013-06-01

A comprehensive understanding of the mechanisms that underlie brain development in premature infants and newborns is crucial for the identification of interventional therapies and rehabilitative strategies. fMRI has the potential to identify such mechanisms, but standard techniques used in adults cannot be implemented in infant studies in a straightforward manner. We have developed an MR safe wrist stimulating robot to systematically investigate the functional brain activity related to both spontaneous and induced wrist movements in premature babies using fMRI. We present the technical aspects of this development and the results of validation experiments. Using the device, the cortical activity associated with both active and passive finger movements were reliably identified in a healthy adult subject. In two preterm infants, passive wrist movements induced a well localized positive BOLD response in the contralateral somatosensory cortex. Furthermore, in a single preterm infant, spontaneous wrist movements were found to be associated with an adjacent cluster of activity, at the level of the infant's primary motor cortex. The described device will allow detailed and objective fMRI studies of somatosensory and motor system development during early human life and following neonatal brain injury.

Effects of resting state condition on reliability, trait specificity, and network connectivity of brain function measured with arterial spin labeled perfusion MRI.

PubMed

Li, Zhengjun; Vidorreta, Marta; Katchmar, Natalie; Alsop, David C; Wolf, Daniel H; Detre, John A

2018-06-01

Resting state fMRI (rs-fMRI) provides imaging biomarkers of task-independent brain function that can be associated with clinical variables or modulated by interventions such as behavioral training or pharmacological manipulations. These biomarkers include time-averaged regional brain function as manifested by regional cerebral blood flow (CBF) measured using arterial spin labeled (ASL) perfusion MRI and correlated temporal fluctuations of function across brain networks with either ASL or blood oxygenation level dependent (BOLD) fMRI. Resting-state studies are typically carried out using just one of several prescribed state conditions such as eyes closed (EC), eyes open (EO), or visual fixation on a cross-hair (FIX), which may affect the reliability and specificity of rs-fMRI. In this study, we collected test-retest ASL MRI data during 4 resting-state task conditions: EC, EO, FIX and PVT (low-frequency psychomotor vigilance task), and examined the effects of these task conditions on reliability and reproducibility as well as trait specificity of regional brain function. We also acquired resting-state BOLD fMRI under FIX and compared the network connectivity reliabilities between the four ASL conditions and the BOLD FIX condition. For resting-state ASL data, EC provided the highest CBF reliability, reproducibility, trait specificity, and network connectivity reliability, followed by EO, while FIX was lowest on all of these measures. PVT demonstrated lower CBF reliability, reproducibility and trait specificity than EO and EC. Overall network connectivity reliability was comparable between ASL and BOLD. Our findings confirm ASL CBF as a reliable, stable, and consistent measure of resting-state regional brain function and support the use of EC or EO over FIX and PVT as the resting-state condition. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

MRI of the stomach: a pictorial review with a focus on oncological applications and gastric motility.

PubMed

Sheybani, Arman; Menias, Christine O; Luna, Antonio; Fowler, Kathryn J; Hara, Amy Kiyo; Silva, Alvin C; Yano, Motoyo; Sandrasegaran, Kumar

2015-04-01

The purpose of this pictorial review is to demonstrate gastric pathology seen on magnetic resonance imaging (MRI) and discuss the essential MRI sequences for the evaluation of benign and malignant gastric pathologies. Common tumors of the stomach, polyposis syndromes, iatrogenic conditions, as well as other conditions of the stomach will be reviewed. The utility of MRI in the evaluation of patients with gastric malignancies and disorders of gastric motility will also be discussed.

Impact of imaging landmark on the risk of MRI-related heating near implanted medical devices like cardiac pacemaker leads.

PubMed

Nordbeck, Peter; Ritter, Oliver; Weiss, Ingo; Warmuth, Marcus; Gensler, Daniel; Burkard, Natalie; Herold, Volker; Jakob, Peter M; Ertl, Georg; Ladd, Mark E; Quick, Harald H; Bauer, Wolfgang R

2011-01-01

Implanted medical devices such as cardiac pacemakers pose a potential hazard in magnetic resonance imaging. Electromagnetic fields have been shown to cause severe radio frequency-induced tissue heating in some cases. Imaging exclusion zones have been proposed as an instrument to reduce patient risk. The purpose of this study was to further assess the impact of the imaging landmark on the risk for unintended implant heating by measuring the radio frequency-induced electric fields in a body phantom under several imaging conditions at 1.5T. The results show that global radio frequency-induced coupling is highest with the torso centered along the superior-inferior direction of the transmit coil. The induced E-fields inside the body shift when changing body positioning, reducing both global and local radio frequency coupling if body and/or conductive implant are moved out from the transmit coil center along the z-direction. Adequate selection of magnetic resonance imaging landmark can significantly reduce potential hazards in patients with implanted medical devices. © 2010 Wiley-Liss, Inc.

A novel conduit-based coaptation device for primary nerve repair.

PubMed

Bamba, Ravinder; Riley, D Colton; Kelm, Nathaniel D; Cardwell, Nancy; Pollins, Alonda C; Afshari, Ashkan; Nguyen, Lyly; Dortch, Richard D; Thayer, Wesley P

2018-06-01

Conduit-based nerve repairs are commonly used for small nerve gaps, whereas primary repair may be performed if there is no tension on nerve endings. We hypothesize that a conduit-based nerve coaptation device will improve nerve repair outcomes by avoiding sutures at the nerve repair site and utilizing the advantages of a conduit-based repair. The left sciatic nerves of female Sprague-Dawley rats were transected and repaired using a novel conduit-based device. The conduit-based device group was compared to a control group of rats that underwent a standard end-to-end microsurgical repair of the sciatic nerve. Animals underwent behavioral assessments at weekly intervals post-operatively using the sciatic functional index (SFI) test. Animals were sacrificed at four weeks to obtain motor axon counts from immunohistochemistry. A sub-group of animals were sacrificed immediately post repair to obtain MRI images. SFI scores were superior in rats which received conduit-based repairs compared to the control group. Motor axon counts distal to the injury in the device group at four weeks were statistically superior to the control group. MRI tractography was used to demonstrate repair of two nerves using the novel conduit device. A conduit-based nerve coaptation device avoids sutures at the nerve repair site and leads to improved outcomes in a rat model. Conduit-based nerve repair devices have the potential to standardize nerve repairs while improving outcomes.

Piezoelectric actuator design for MR elastography: implementation and vibration issues.

PubMed

Tse, Zion Tsz Ho; Chan, Yum Ji; Janssen, Henning; Hamed, Abbi; Young, Ian; Lamperth, Michael

2011-09-01

MR elastography (MRE) is an emerging technique for tumor diagnosis. MRE actuation devices require precise mechanical design and radiofrequency engineering to achieve the required mechanical vibration performance and MR compatibility. A method of designing a general-purpose, compact and inexpensive MRE actuator is presented. It comprises piezoelectric bimorphs arranged in a resonant structure designed to operate at its resonant frequency for maximum vibration amplitude. An analytical model was established to understand the device vibration characteristics. The model-predicted performance was validated in experiments, showing its accuracy in predicting the actuator resonant frequency with an error < 4%. The device MRI compatibility was shown to cause minimal interference to a 1.5 tesla MRI scanner, with maximum signal-to-noise ratio reduction of 7.8% and generated artefact of 7.9 mm in MR images. A piezoelectric MRE actuator is proposed, and its implementation, vibration issues and future work are discussed. Copyright © 2011 John Wiley & Sons, Ltd.

MRI-only treatment planning: benefits and challenges

NASA Astrophysics Data System (ADS)

Owrangi, Amir M.; Greer, Peter B.; Glide-Hurst, Carri K.

2018-03-01

Over the past decade, the application of magnetic resonance imaging (MRI) has increased, and there is growing evidence to suggest that improvements in the accuracy of target delineation in MRI-guided radiation therapy may improve clinical outcomes in a variety of cancer types. However, some considerations should be recognized including patient motion during image acquisition and geometric accuracy of images. Moreover, MR-compatible immobilization devices need to be used when acquiring images in the treatment position while minimizing patient motion during the scan time. Finally, synthetic CT images (i.e. electron density maps) and digitally reconstructed radiograph images should be generated from MRI images for dose calculation and image guidance prior to treatment. A short review of the concepts and techniques that have been developed for implementation of MRI-only workflows in radiation therapy is provided in this document.

Suture versus FasT-Fix all-inside meniscus repair at time of anterior cruciate ligament reconstruction.

PubMed

Choi, Nam-Hong; Kim, Byeong-Yeon; Hwang Bo, Byung-Hun; Victoroff, Brian N

2014-10-01

To compare meniscal healing and functional outcomes after all-inside meniscal repair between sutures and meniscal fixation devices. Sixty patients with a tear within the red-red or red-white zones of the posterior horn of the medial or lateral meniscus in conjunction with an anterior cruciate ligament (ACL) tear were included in this study. Meniscal repairs were performed with sutures in 35 patients and the FasT-Fix device (Smith & Nephew Endoscopy, Andover, MA) in 25 patients concomitantly with hamstring ACL reconstruction. Postoperative evaluations included Lysholm knee score, Tegner activity scale, Lachman and pivot-shift tests, and KT-1000 arthrometer (MEDmetric, San Diego, CA) testing. Follow-up magnetic resonance imaging (MRI) scans were obtained postoperatively for all patients to evaluate meniscal healing. The mean follow-up period was 47.2 months. In the suture group, 31 patients (86.1%) were asymptomatic and 4 (13.9%) were symptomatic. In the FasT-Fix group, 20 patients (80%) were asymptomatic and 5 (20%) were symptomatic. Postoperative functional evaluation and knee stability showed no statistically significant difference between the 2 groups. Follow-up MRI showed that 26 menisci (74.3%) were healed, 3 menisci (8.6%) were partially healed, and 6 menisci (17.1%) were not healed in the suture group. In the FasT-Fix group, 15 menisci (64%) were healed, 7 menisci (24%) were partially healed, and 3 menisci (12%) were not healed. Follow-up MRI showed no statistically significant difference between the 2 groups. In the FasT-Fix group, follow-up MRI showed a newly developed cyst posterior to the medial meniscus in 2 patients. A new tear anterior to the previous tear was found in 1 patient. In the suture group, follow-up MRI showed no cysts or new tears. All-inside meniscal repairs using either sutures or the FasT-Fix device showed satisfactory results in patients with concomitant hamstring ACL reconstruction. There was no statistically significant difference in meniscal healing evaluated by MRI and functional outcomes between the 2 techniques. Level III, retrospective comparative study. Copyright © 2014 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Monitoring local heating around an interventional MRI antenna with RF radiometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ertürk, M. Arcan; El-Sharkawy, AbdEl-Monem M.; Bottomley, Paul A., E-mail: bottoml@mri.jhu.edu

Purpose: Radiofrequency (RF) radiometry uses thermal noise detected by an antenna to measure the temperature of objects independent of medical imaging technologies such as magnetic resonance imaging (MRI). Here, an active interventional MRI antenna can be deployed as a RF radiometer to measure local heating, as a possible new method of monitoring device safety and thermal therapy. Methods: A 128 MHz radiometer receiver was fabricated to measure the RF noise voltage from an interventional 3 T MRI loopless antenna and calibrated for temperature in a uniformly heated bioanalogous gel phantom. Local heating (ΔT) was induced using the antenna for RFmore » transmission and measured by RF radiometry, fiber-optic thermal sensors, and MRI thermometry. The spatial thermal sensitivity of the antenna radiometer was numerically computed using a method-of-moment electric field analyses. The gel’s thermal conductivity was measured by MRI thermometry, and the localized time-dependent ΔT distribution computed from the bioheat transfer equation and compared with radiometry measurements. A “H-factor” relating the 1 g-averaged ΔT to the radiometric temperature was introduced to estimate peak temperature rise in the antenna’s sensitive region. Results: The loopless antenna radiometer linearly tracked temperature inside a thermally equilibrated phantom up to 73 °C to within ±0.3 °C at a 2 Hz sample rate. Computed and MRI thermometric measures of peak ΔT agreed within 13%. The peak 1 g-average temperature was H = 1.36 ± 0.02 times higher than the radiometric temperature for any media with a thermal conductivity of 0.15–0.50 (W/m)/K, indicating that the radiometer can measure peak 1 g-averaged ΔT in physiologically relevant tissue within ±0.4 °C. Conclusions: Active internal MRI detectors can serve as RF radiometers at the MRI frequency to provide accurate independent measures of local and peak temperature without the artifacts that can accompany MRI thermometry or the extra space needed to accommodate alternative thermal transducers. A RF radiometer could be integrated in a MRI scanner to permit “self-monitoring” for assuring device safety and/or monitoring delivery of thermal therapy.« less

[4D-MRI using the synchronized sampling method (SSM)].

PubMed

Shimada, Yasuhiro; Fujimoto, Ichirou; Takemoto, Hironori; Takano, Sayoko; Masaki, Shinobu; Honda, Kiyoshi; Takeo, Kazuhiro

2002-12-01

A synchronized sampling method (SSM) was developed for the study of voluntary movements by combining the electrocardiographic (ECG) gating method with an external triggering device, and four-dimensional magnetic resonance imaging (4D-MRI) at a rate of 30 frames per second was accomplished by volumetric imaging with the SSM. This method was first applied to the motion imaging of articulatory organs during repetitions of a Japanese five-vowel sequence, and the dynamic change in vocal tract area function was demonstrated with sufficient temporal resolution. This paper describes the methodology, applicability, and limitations of 4D-MRI with the SSM.

Numerical evaluation of heating in the human head due to magnetic resonance imaging (MRI)

NASA Astrophysics Data System (ADS)

Nguyen, Uyen; Brown, Steve; Chang, Isaac; Krycia, Joe; Mirotznik, Mark S.

2003-06-01

In this paper we present a numerical model for evaluating tissue heating during magnetic resonance imaging (MRI). Our method, which included a detailed anatomical model of a human head, calculated both the electromagnetic power deposition and the associated temperature elevations during a MRI head examination. Numerical studies were conducted using a realistic birdcage coil excited at frequencies ranging from 63 MHz to 500 MHz. The model was validated both experimentally and analytically. The experimental validation was performed at the MR test facility located at the FDA's Center for Devices and Radiological Health (CDRH).

MRI Scans

MedlinePlus

Magnetic resonance imaging (MRI) uses a large magnet and radio waves to look at organs and structures inside your body. Health care professionals use MRI scans to diagnose a variety of conditions, from torn ...

Magnetic resonance imaging. Application to family practice.

PubMed

Goh, R H; Somers, S; Jurriaans, E; Yu, J

1999-09-01

To review indications, contraindications, and risks of using magnetic resonance imaging (MRI) in order to help primary care physicians refer patients appropriately for MRI, screen for contraindications to using MRI, and educate patients about MRI. Recommendations are based on classic textbooks, the policies of our MRI group, and a literature search using MEDLINE with the MeSH headings magnetic resonance imaging, brain, musculoskeletal, and spine. The search was limited to human, English-language, and review articles. Evidence in favour of using MRI for imaging the head, spine, and joints is well established. For cardiac, abdominal, and pelvic conditions, MRI has been shown useful for certain indications, usually to complement other modalities. For demonstrating soft tissue conditions, MRI is better than computed tomography (CT), but CT shows bone and acute bleeding better. Therefore, patients with trauma or suspected intracranial bleeding should have CT. Tumours, congenital abnormalities, vascular structures, and the cervical or thoracic spine show better on MRI. Either modality can be used for lower back pain. Cardiac, abdominal, and pelvic abnormalities should be imaged with ultrasound or CT before MRI. Contraindications for MRI are mainly metallic implants or shrapnel, severe claustrophobia, or obesity. With the increasing availability of MRI scanners in Canada, better understanding of the indications, contraindications, and risks will be helpful for family physicians and their patients.

Design of a Teleoperated Needle Steering System for MRI-guided Prostate Interventions

PubMed Central

Seifabadi, Reza; Iordachita, Iulian; Fichtinger, Gabor

2013-01-01

Accurate needle placement plays a key role in success of prostate biopsy and brachytherapy. During percutaneous interventions, the prostate gland rotates and deforms which may cause significant target displacement. In these cases straight needle trajectory is not sufficient for precise targeting. Although needle spinning and fast insertion may be helpful, they do not entirely resolve the issue. We propose robot-assisted bevel-tip needle steering under MRI guidance as a potential solution to compensate for the target displacement. MRI is chosen for its superior soft tissue contrast in prostate imaging. Due to the confined workspace of the MRI scanner and the requirement for the clinician to be present inside the MRI room during the procedure, we designed a MRI-compatible 2-DOF haptic device to command the needle steering slave robot which operates inside the scanner. The needle steering slave robot was designed to be integrated with a previously developed pneumatically actuated transperineal robot for MRI-guided prostate needle placement. We describe design challenges and present the conceptual design of the master and slave robots and the associated controller. PMID:24649480

Wide-bore 1.5 T MRI-guided deep brain stimulation surgery: initial experience and technique comparison.

PubMed

Sillay, Karl A; Rusy, Deborah; Buyan-Dent, Laura; Ninman, Nancy L; Vigen, Karl K

2014-12-01

We report results of the initial experience with magnetic resonance image (MRI)-guided implantation of subthalamic nucleus (STN) deep brain stimulating (DBS) electrodes at the University of Wisconsin after having employed frame-based stereotaxy with previously available MR imaging techniques and microelectrode recording for STN DBS surgeries. Ten patients underwent MRI-guided DBS implantation of 20 electrodes between April 2011 and March 2013. The procedure was performed in a purpose-built intraoperative MRI suite configured specifically to allow MRI-guided DBS, using a wide-bore (70 cm) MRI system. Trajectory guidance was accomplished with commercially available system consisting of an MR-visible skull-mounted aiming device and a software guidance system processing intraoperatively acquired iterative MRI scans. A total of 10 patients (5 male, 5 female)-representative of the Parkinson Disease (PD) population-were operated on with standard technique and underwent 20 electrode placements under MRI-guided bilateral STN-targeted DBS placement. All patients completed the procedure with electrodes successfully placed in the STN. Procedure time improved with experience. Our initial experience confirms the safety of MRI-guided DBS, setting the stage for future investigations combining physiology and MRI guidance. Further follow-up is required to compare the efficacy of the MRI-guided surgery cohort to that of traditional frame-based stereotaxy. Copyright © 2014 Elsevier B.V. All rights reserved.

A Cinematic Magnetic Resonance Imaging Study of Milk of Magnesia Laxative and an Antiflatulent Diet to Reduce Intrafraction Prostate Motion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nichol, Alan M.; Warde, Padraig R.; Lockwood, Gina A.

Purpose: To determine the reduction of prostate motion during a typical radiotherapy (RT) fraction from a bowel regimen comprising an antiflatulent diet and daily milk of magnesia. Methods and Materials: Forty-two patients with T1c-T2c prostate cancer voided the bladder and rectum before three cinematic magnetic resonance imaging scans obtained every 9 s for 9 min in a vacuum immobilization device. The MRIs were at baseline without bowel regimen (MRI-BL), before CT planning with bowel regimen (MRI-CT), and before a randomly assigned RT fraction (1-42) with bowel regimen (MRI-RT). A single observer tracked displacement of the posterior midpoint (PM) of themore » prostate. The primary endpoints were comparisons of the proportion of time that the PM was displaced >3 mm (PTPM3) from its initial position, and the secondary endpoints were comparisons of the reduction of initial rectal area, with and without the bowel regimen. Results: The mean rectal area was: 13.5 cm{sup 2} at MRI-BL, 12.7 cm{sup 2} at MRI-CT, and 12.3 cm{sup 2} at MRI-RT (MRI-BL vs. MRI-CT, p = 0.11; MRI-BL vs. MRI-CT, p = 0.07). Moving rectal gas alone (56%) and moving gas and stool (18%) caused 74% of intrafraction prostate motion. The PTPM3 was 11.3% at MRI-BL, 4.8% at MRI-CT, and 12.0% at MRI-RT (MRI-BL vs. MRI-CT, p = 0.12; MRI-BL vs. MRI-RT, p = 0.89). Conclusion: For subjects voiding their rectum before imaging, an antiflatulent diet and milk of magnesia laxative did not significantly reduce initial rectal area or intrafraction prostate motion.« less

Equilibrium and stability of flow-dominated Plasmas in the Big Red Ball

NASA Astrophysics Data System (ADS)

Siller, Robert; Flanagan, Kenneth; Peterson, Ethan; Milhone, Jason; Mirnov, Vladimir; Forest, Cary

2017-10-01

The equilibrium and linear stability of flow-dominated plasmas are studied numerically using a spectral techniques to model MRI and dynamo experiments in the Big Red Ball device. The equilibrium code solves for steady-state magnetic fields and plasma flows subject to boundary conditions in a spherical domain. It has been benchmarked with NIMROD (non-ideal MHD with rotation - open discussion), Two different flow scenarios are studied. The first scenario creates a differentially rotating toroidal flow that is peaked at the center. This is done to explore the onset of the magnetorotational instability (MRI) in a spherical geometry. The second scenario creates a counter-rotating von Karman-like flow in the presence of a weak magnetic field. This is done to explore the plasma dynamo instability in the limit of a weak applied field. Both scenarios are numerically modeled as axisymmetric flow to create a steady-state equilibrium solution, the stability and normal modes are studied in the lowest toroidal mode number. The details of the observed flow, and the structure of the fastest growing modes will be shown. DoE, NSF.

A numerical model for aggregations formation and magnetic driving of spherical particles based on OpenFOAM®.

PubMed

Karvelas, E G; Lampropoulos, N K; Sarris, I E

2017-04-01

This work presents a numerical model for the formation of particle aggregations under the influence of a permanent constant magnetic field and their driving process under a gradient magnetic field, suitably created by a Magnetic Resonance Imaging (MRI) device. The model is developed in the OpenFOAM platform and it is successfully compared to the existing experimental and numerical results in terms of aggregates size and their motion in water solutions. Furthermore, several series of simulations are performed for two common types of particles of different diameter in order to verify their aggregation and flow behaviour, under various constant and gradient magnetic fields in the usual MRI working range. Moreover, the numerical model is used to measure the mean length of aggregations, the total time needed to form and their mean velocity under different permanent and gradient magnetic fields. The present model is found to predict successfully the size, velocity and distribution of aggregates. In addition, our simulations showed that the mean length of aggregations is proportional to the permanent magnetic field magnitude and particle diameter according to the relation : l¯ a =7.5B 0 d i 3/2 . The mean velocity of the aggregations is proportional to the magnetic gradient, according to : u¯ a =6.63G˜B 0 and seems to reach a steady condition after a certain period of time. The mean time needed for particles to aggregate is proportional to permanent magnetic field magnitude, scaled by the relationship : t¯ a ∝7B 0 . A numerical model to predict the motion of magnetic particles for medical application is developed. This model is found suitable to predict the formation of aggregations and their motion under the influence of permanent and gradient magnetic fields, respectively, that are produced by an MRI device. The magnitude of the external constant magnetic field is the most important parameter for the aggregations formation and their driving. Copyright © 2017 Elsevier B.V. All rights reserved.

The performance of interventional loopless MRI antennae at higher magnetic field strengths

PubMed Central

El-Sharkawy, AbdEl-Monem M.; Qian, Di; Bottomley, Paul A.

2008-01-01

Interventional, “loopless antenna” MRI detectors are currently limited to 1.5 T. This study investigates whether loopless antennae offer signal-to-noise ratio (SNR) and field-of-view (FOV) advantages at higher fields, and whether device heating can be controlled within safe limits. The absolute SNR performance of loopless antennae from 0.5 to 5 T is investigated both analytically, using electromagnetic (EM) dipole antenna theory, and numerically with the EM method of moments, and found to vary almost quadratically with field strength depending on the medium’s electrical properties, the noise being dominated by direct sample conduction losses. The prediction is confirmed by measurements of the absolute SNR of low-loss loopless antennae fabricated for 1.5, 3, and 4.7 T, immersed in physiologically comparable saline. Gains of 3.8±0.2- and 9.7±0.3-fold in SNR, and approximately 10- and 50-fold gains in the useful FOV area are observed at 3 and 4.7 T, respectively, compared to 1.5 T. Heat testing of a 3 T biocompatible nitinol-antenna fabricated with a redesigned decoupling circuit shows maximum heating of ∼1 °C for MRI operating at high MRI exposure levels. Experiments in the rabbit aorta confirm the SNR and FOV advantages of the 3 T antenna versus an equivalent commercial 1.5 T device in vivo. This work is the first to study the performance of experimental internal MRI detectors above 1.5 T. The large SNR and FOV gains realized present a major opportunity for high-resolution imaging of vascular pathology and MRI-guided intervention. PMID:18561676

Interrater and intrarater agreements of magnetic resonance imaging findings in the lumbar spine: significant variability across degenerative conditions.

PubMed

Fu, Michael C; Buerba, Rafael A; Long, William D; Blizzard, Daniel J; Lischuk, Andrew W; Haims, Andrew H; Grauer, Jonathan N

2014-10-01

Magnetic resonance imaging (MRI) is frequently used in the evaluation of degenerative conditions in the lumbar spine. The relative interrater and intrarater agreements of MRI findings across different pathologic conditions are underexplored, as most studies are focused on specific findings. The purpose of this study was to characterize the interrater and intrarater agreements of MRI findings used to assess the degenerative lumbar spine. A retrospective diagnostic study at a large academic medical center was undertaken with a panel of orthopedic surgeons and musculoskeletal radiologists to assess lumbar MRIs using standardized criteria. Seventy-five subjects who underwent routine lumbar spine MRI at our institution were included. Each MRI study was assessed for 10 lumbar degenerative findings using standardized criteria. Lumbar vertebral levels were assessed independently, where applicable, for a total of 52 data points collected per study. T2-weighted axial and sagittal MRI sequences were presented in random order to the four reviewers (two orthopedic spine surgeons and two musculoskeletal radiologists) independently to determine interrater agreement. The first 10 studies were reevaluated at the end to determine intrarater agreement. Images were assessed using standardized and pilot-tested criteria to assess disc degeneration, stenosis, and other degenerative changes. Interrater and intrarater absolute percent agreements were calculated. To highlight the most clinically important MRI disagreements, a modified agreement analysis was also performed (in which disagreements between the lowest two severity grades for applicable conditions were ignored). Fleiss kappa coefficients for interrater agreement were determined. The overall absolute and modified interrater agreements were 76.9% and 93.5%, respectively. The absolute and modified intrarater agreements were 81.3% and 92.7%, respectively. Average Fleiss kappa coefficient was 0.431, suggesting moderate overall agreement. However, when stratified by condition, absolute interrater agreement ranged from 65.1% to 92.0%. Disc hydration, disc space height, and bone marrow changes exhibited the lowest absolute interrater agreements. The absolute intrarater agreement had a narrower range, from 74.5% to 91.5%. Fleiss kappa coefficients ranged from fair-to-substantial agreement (0.282-0.618). Even in a study using standardized evaluation criteria, there was significant variability in the interrater and intrarater agreements of MRI in assessing different degenerative conditions of the lumbar spine. Clinicians should be aware of the condition-specific diagnostic limitations of MRI interpretation. Copyright © 2014 Elsevier Inc. All rights reserved.

Biomedical Investigations with Laser-Polarized Noble Gas Magnetic Resonance

NASA Technical Reports Server (NTRS)

Walsworth, Ronald L.

2003-01-01

We pursued advanced technology development of laser-polarized noble gas nuclear magnetic resonance (NMR) as a novel biomedical imaging tool for ground-based and eventually space-based application. This new multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI)-e.g., of lung ventilation-as well as studies of tissue perfusion. In addition, laser-polarized noble gases (3He and 129Xe) do not require a large magnetic field for sensitive detection, opening the door to practical MRI at very low magnetic fields with an open, lightweight, and low-power device. We pursued two technology development specific aims: (1) development of low-field (less than 0.01 T) noble gas MRI of humans; and (2) development of functional MRI of the lung using laser-polarized noble gas and related techniques.

Visualization and appearance of artifacts of leadless pacemaker systems in cardiac MRI : An experimental ex vivo study.

PubMed

Edlinger, Christoph; Granitz, Marcel; Paar, Vera; Jung, Christian; Pfeil, Alexander; Eder, Sarah; Wernly, Bernhard; Kammler, Jürgen; Hergan, Klaus; Hoppe, Uta C; Steinwender, Clemens; Lichtenauer, Michael; Kypta, Alexander

2018-05-23

Leadless pacemaker systems are an important upcoming device in clinical rhythmology. Currently two different products are available with the Micra system (Medtronic) being the most used in the clinical setting to date. The possibility to perform magnetic resonance imaging (MRI) is an important feature of modern pacemaker devices. Even though the Micra system is suitable for MRI, little is yet known about its impact on artifacts within the images. The aim of our ex vivo study was to perform cardiac MRI to quantify the artifacts and to evaluate if artifacts limit or inhibit the assessment of the surrounding myocardium. After ex vivo implantation of the leadless pacemaker (LP) in a porcine model, hearts were filled with saline solution and fixed on wooden sticks on a plastic container. The model was examined at 1.5 T and at 3 T using conventional sequences and T2 mapping sequences. In addition, conventional X‑rays and computed tomography (CT) scans were performed. Correct implantation of the LP could be performed in all hearts. In almost all MRI sequences the right ventricle and the septal region surrounding the (LP) were altered by an artifact and therefore would sustain limited assessment; however, the rest of the myocardium remained free of artifacts and evaluable for common radiologic diagnoses. A characteristic shamrock-shaped artifact was generated which appeared to be even more intense in magnitude and brightness when using 3 T compared to 1.5 T. The use of the Micra system in cardiac MRI appeared to be feasible. In our opinion, it will still be possible to make important clinical cardiac MRI diagnoses (the detection of major ischemic areas or inflammatory processes) in patients using the Micra system. We suggest the use of 1.5 T as the preferred method in clinical practice.

Comparison of two bioelectrical impedance analysis devices with dual energy X-ray absorptiometry and magnetic resonance imaging in the estimation of body composition.

PubMed

Wang, Ji-Guang; Zhang, Yi; Chen, Han-E; Li, Yan; Cheng, Xiao-Guang; Xu, Li; Guo, Zhe; Zhao, Xing-Shan; Sato, Tetsuya; Cao, Qi-Yun; Chen, Ke-Min; Li, Biao

2013-01-01

We compared a 4-limb bioelectrical impedance analysis (BIA) system, HBF 359 (Omron), and a 2-limb foot-to-foot device, BC 532 (Tanita), with the standard dual energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) methods for the measurement of body fat percentage (BF), skeletal muscle mass percentage (SMM, or fat-free mass [FFM] for BC 532), and visceral fat level (VF). Body composition was measured in 200 healthy volunteers (100 men and 100 women, mean age 48 years) by HBF 359 and BC 532 and by DXA and MRI. The agreement was assessed by correlation analysis and paired t-test. The correlation coefficients between BIA and DXA or MRI ranged from 0.71 to 0.89 for BF, SMM, and VF by HBF 359 and from 0.77 to 0.90 for BF, FFM, and VF by BC 532 in all subjects and in men and women separately (p < 0.001 for all). Compared with DXA, HBF 359 significantly (p < 0.001) underestimated BF by -5.8% in men and -9.6% in women. Compared with MRI, the corresponding underestimatons (negative) or overestimations (positive) by HBF 359 in men and women were, respectively, +1.9% (p = 0.02) and +1.7% (p = 0.10) for SMM, and +13.3% (p < 0.001) and -8.5% (p = 0.006), for VF. The corresponding values by BC 532 in men and women were -10.7 and -6.2% for BF, -1.4 and -2.5% for FFM, and +20.4 and -18.0% for VF. The BIA devices are accurate in the estimation of body composition, especially skeletal muscle mass or FFM.

First magnetic resonance imaging-guided aortic stenting and cava filter placement using a polyetheretherketone-based magnetic resonance imaging-compatible guidewire in swine: proof of concept.

PubMed

Kos, Sebastian; Huegli, Rolf; Hofmann, Eugen; Quick, Harald H; Kuehl, Hilmar; Aker, Stephanie; Kaiser, Gernot M; Borm, Paul J A; Jacob, Augustinus L; Bilecen, Deniz

2009-05-01

The purpose of this study was to demonstrate feasibility of percutaneous transluminal aortic stenting and cava filter placement under magnetic resonance imaging (MRI) guidance exclusively using a polyetheretherketone (PEEK)-based MRI-compatible guidewire. Percutaneous transluminal aortic stenting and cava filter placement were performed in 3 domestic swine. Procedures were performed under MRI-guidance in an open-bore 1.5-T scanner. The applied 0.035-inch guidewire has a PEEK core reinforced by fibres, floppy tip, hydrophilic coating, and paramagnetic markings for passive visualization. Through an 11F sheath, the guidewire was advanced into the abdominal (swine 1) or thoracic aorta (swine 2), and the stents were deployed. The guidewire was advanced into the inferior vena cava (swine 3), and the cava filter was deployed. Postmortem autopsy was performed. Procedural success, guidewire visibility, pushability, and stent support were qualitatively assessed by consensus. Procedure times were documented. Guidewire guidance into the abdominal and thoracic aortas and the inferior vena cava was successful. Stent deployments were successful in the abdominal (swine 1) and thoracic (swine 2) segments of the descending aorta. Cava filter positioning and deployment was successful. Autopsy documented good stent and filter positioning. Guidewire visibility through applied markers was rated acceptable for aortic stenting and good for venous filter placement. Steerability, pushability, and device support were good. The PEEK-based guidewire allows either percutaneous MRI-guided aortic stenting in the thoracic and abdominal segments of the descending aorta and filter placement in the inferior vena cava with acceptable to good device visibility and offers good steerability, pushability, and device support.

First Magnetic Resonance Imaging-Guided Aortic Stenting and Cava Filter Placement Using a Polyetheretherketone-Based Magnetic Resonance Imaging-Compatible Guidewire in Swine: Proof of Concept

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kos, Sebastian, E-mail: skos@gmx.d; Huegli, Rolf; Hofmann, Eugen

The purpose of this study was to demonstrate feasibility of percutaneous transluminal aortic stenting and cava filter placement under magnetic resonance imaging (MRI) guidance exclusively using a polyetheretherketone (PEEK)-based MRI-compatible guidewire. Percutaneous transluminal aortic stenting and cava filter placement were performed in 3 domestic swine. Procedures were performed under MRI-guidance in an open-bore 1.5-T scanner. The applied 0.035-inch guidewire has a PEEK core reinforced by fibres, floppy tip, hydrophilic coating, and paramagnetic markings for passive visualization. Through an 11F sheath, the guidewire was advanced into the abdominal (swine 1) or thoracic aorta (swine 2), and the stents were deployed. Themore » guidewire was advanced into the inferior vena cava (swine 3), and the cava filter was deployed. Postmortem autopsy was performed. Procedural success, guidewire visibility, pushability, and stent support were qualitatively assessed by consensus. Procedure times were documented. Guidewire guidance into the abdominal and thoracic aortas and the inferior vena cava was successful. Stent deployments were successful in the abdominal (swine 1) and thoracic (swine 2) segments of the descending aorta. Cava filter positioning and deployment was successful. Autopsy documented good stent and filter positioning. Guidewire visibility through applied markers was rated acceptable for aortic stenting and good for venous filter placement. Steerability, pushability, and device support were good. The PEEK-based guidewire allows either percutaneous MRI-guided aortic stenting in the thoracic and abdominal segments of the descending aorta and filter placement in the inferior vena cava with acceptable to good device visibility and offers good steerability, pushability, and device support.« less

The inclusion of functional connectivity information into fMRI-based neurofeedback improves its efficacy in the reduction of cigarette cravings.

PubMed

Kim, Dong-Youl; Yoo, Seung-Schik; Tegethoff, Marion; Meinlschmidt, Gunther; Lee, Jong-Hwan

2015-08-01

Real-time fMRI (rtfMRI) neurofeedback (NF) facilitates volitional control over brain activity and the modulation of associated mental functions. The NF signals of traditional rtfMRI-NF studies predominantly reflect neuronal activity within ROIs. In this study, we describe a novel rtfMRI-NF approach that includes a functional connectivity (FC) component in the NF signal (FC-added rtfMRI-NF). We estimated the efficacy of the FC-added rtfMRI-NF method by applying it to nicotine-dependent heavy smokers in an effort to reduce cigarette craving. ACC and medial pFC as well as the posterior cingulate cortex and precuneus are associated with cigarette craving and were chosen as ROIs. Fourteen heavy smokers were randomly assigned to receive one of two types of NF: traditional activity-based rtfMRI-NF or FC-added rtfMRI-NF. Participants received rtfMRI-NF training during two separate visits after overnight smoking cessation, and cigarette craving score was assessed. The FC-added rtfMRI-NF resulted in greater neuronal activity and increased FC between the targeted ROIs than the traditional activity-based rtfMRI-NF and resulted in lower craving score. In the FC-added rtfMRI-NF condition, the average of neuronal activity and FC was tightly associated with craving score (Bonferroni-corrected p = .028). However, in the activity-based rtfMRI-NF condition, no association was detected (uncorrected p > .081). Non-rtfMRI data analysis also showed enhanced neuronal activity and FC with FC-added NF than with activity-based NF. These results demonstrate that FC-added rtfMRI-NF facilitates greater volitional control over brain activity and connectivity and greater modulation of mental function than activity-based rtfMRI-NF.

Stem cell therapy: MRI guidance and monitoring.

PubMed

Kraitchman, Dara L; Gilson, Wesley D; Lorenz, Christine H

2008-02-01

With the recent advances in magnetic resonance (MR) labeling of cellular therapeutics, it is natural that interventional MRI techniques for targeting would be developed. This review provides an overview of the current methods of stem cell labeling and the challenges that are created with respect to interventional MRI administration. In particular, stem cell therapies will require specialized, MR-compatible devices as well as integration of graphical user interfaces with pulse sequences designed for interactive, real-time delivery in many organs. Specific applications that are being developed will be reviewed as well as strategies for future translation to the clinical realm. (Copyright) 2008 Wiley-Liss, Inc.

The role of magnetic resonance imaging techniques in evaluation and management of the idiopathic inflammatory myopathies.

PubMed

Day, Jessica; Patel, Sandy; Limaye, Vidya

2017-04-01

Magnetic resonance imaging (MRI) is an important tool in the evaluation of neuromuscular disorders. MRI accurately demonstrates muscle oedema, atrophy, subcutaneous pathology and fatty infiltration and also highlights the distribution of muscle involvement. This review examines the role of MRI in evaluation of the idiopathic inflammatory myopathies (IIMs), a heterogeneous group of autoimmune conditions characterised by muscle inflammation and a variety of extra-muscular manifestations. MRI has a clear role in aiding diagnosis of these conditions, guiding muscle biopsy, differentiating subtypes of IIM using a pattern-based approach, and monitoring disease activity in a longitudinal fashion. Whole body MRI is an emerging technique that offers several advantages over regional MRI, but is not currently widely available. We will also consider newer MRI techniques which provide detailed information regarding the metabolism, function and structure of muscle, although their use is restricted to research purposes at present. Copyright © 2017 Elsevier Inc. All rights reserved.

Gradiometer Using Middle Loops as Sensing Elements in a Low-Field SQUID MRI System

NASA Technical Reports Server (NTRS)

Penanen, Konstantin; Hahn, Inseob; Ho Eom, Byeong

2009-01-01

A new gradiometer scheme uses middle loops as sensing elements in lowfield superconducting quantum interference device (SQUID) magnetic resonance imaging (MRI). This design of a second order gradiometer increases its sensitivity and makes it more uniform, compared to the conventional side loop sensing scheme with a comparable matching SQUID. The space between the two middle loops becomes the imaging volume with the enclosing cryostat built accordingly.

Fetal tracheolaryngeal airway obstruction: prenatal evaluation by sonography and MRI

PubMed Central

Courtier, Jesse; Poder, Liina; Wang, Zhen J.; Westphalen, Antonio C.; Yeh, Benjamin M.

2010-01-01

We reviewed the sonographic and MRI findings of tracheolaryngeal obstruction in the fetus. Conditions that can cause tracheolaryngeal obstruction include extrinsic causes such as lymphatic malformation, cervical teratoma and vascular rings and intrinsic causes such as congenital high airway obstruction syndrome (CHAOS). Accurate distinction of these conditions by sonography or MRI can help facilitate parental counseling and management, including the decision to utilize the ex utero intrapartum treatment (EXIT) procedure. PMID:20737145

Image-Based Computational Fluid Dynamics in Blood Vessel Models: Toward Developing a Prognostic Tool to Assess Cardiovascular Function Changes in Prolonged Space Flights

NASA Technical Reports Server (NTRS)

Chatzimavroudis, George P.; Spirka, Thomas A.; Setser, Randolph M.; Myers, Jerry G.

2004-01-01

One of NASA's objectives is to be able to perform a complete, pre-flight, evaluation of cardiovascular changes in astronauts scheduled for prolonged space missions. Computational fluid dynamics (CFD) has shown promise as a method for estimating cardiovascular function during reduced gravity conditions. For this purpose, MRI can provide geometrical information, to reconstruct vessel geometries, and measure all spatial velocity components, providing location specific boundary conditions. The objective of this study was to investigate the reliability of MRI-based model reconstruction and measured boundary conditions for CFD simulations. An aortic arch model and a carotid bifurcation model were scanned in a 1.5T Siemens MRI scanner. Axial MRI acquisitions provided images for geometry reconstruction (slice thickness 3 and 5 mm; pixel size 1x1 and 0.5x0.5 square millimeters). Velocity acquisitions provided measured inlet boundary conditions and localized three-directional steady-flow velocity data (0.7-3.0 L/min). The vessel walls were isolated using NIH provided software (ImageJ) and lofted to form the geometric surface. Constructed and idealized geometries were imported into a commercial CFD code for meshing and simulation. Contour and vector plots of the velocity showed identical features between the MRI velocity data, the MRI-based CFD data, and the idealized-geometry CFD data, with less than 10% differences in the local velocity values. CFD results on models reconstructed from different MRI resolution settings showed insignificant differences (less than 5%). This study illustrated, quantitatively, that reliable CFD simulations can be performed with MRI reconstructed models and gives evidence that a future, subject-specific, computational evaluation of the cardiovascular system alteration during space travel is feasible.

A method for safety testing of radiofrequency/microwave-emitting devices using MRI.

PubMed

Alon, Leeor; Cho, Gene Y; Yang, Xing; Sodickson, Daniel K; Deniz, Cem M

2015-11-01

Strict regulations are imposed on the amount of radiofrequency (RF) energy that devices can emit to prevent excessive deposition of RF energy into the body. In this study, we investigated the application of MR temperature mapping and 10-g average specific absorption rate (SAR) computation for safety evaluation of RF-emitting devices. Quantification of the RF power deposition was shown for an MRI-compatible dipole antenna and a non-MRI-compatible mobile phone via phantom temperature change measurements. Validation of the MR temperature mapping method was demonstrated by comparison with physical temperature measurements and electromagnetic field simulations. MR temperature measurements alongside physical property measurements were used to reconstruct 10-g average SAR. The maximum temperature change for a dipole antenna and the maximum 10-g average SAR were 1.83°C and 12.4 W/kg, respectively, for simulations and 1.73°C and 11.9 W/kg, respectively, for experiments. The difference between MR and probe thermometry was <0.15°C. The maximum temperature change and the maximum 10-g average SAR for a cell phone radiating at maximum output for 15 min was 1.7°C and 0.54 W/kg, respectively. Information acquired using MR temperature mapping and thermal property measurements can assess RF/microwave safety with high resolution and fidelity. © 2014 Wiley Periodicals, Inc.

A Method for Safety Testing of Radiofrequency/Microwave-Emitting Devices Using MRI

PubMed Central

Alon, Leeor; Cho, Gene Y.; Yang, Xing; Sodickson, Daniel K.; Deniz, Cem M.

2015-01-01

Purpose Strict regulations are imposed on the amount of radiofrequency (RF) energy that devices can emit to prevent excessive deposition of RF energy into the body. In this study, we investigated the application of MR temperature mapping and 10-g average specific absorption rate (SAR) computation for safety evaluation of RF-emitting devices. Methods Quantification of the RF power deposition was shown for an MRI-compatible dipole antenna and a non–MRI-compatible mobile phone via phantom temperature change measurements. Validation of the MR temperature mapping method was demonstrated by comparison with physical temperature measurements and electromagnetic field simulations. MR temperature measurements alongside physical property measurements were used to reconstruct 10-g average SAR. Results The maximum temperature change for a dipole antenna and the maximum 10-g average SAR were 1.83° C and 12.4 W/kg, respectively, for simulations and 1.73° C and 11.9 W/kg, respectively, for experiments. The difference between MR and probe thermometry was <0.15° C. The maximum temperature change and the maximum 10-g average SAR for a cell phone radiating at maximum output for 15 min was 1.7° C and 0.54 W/kg, respectively. Conclusion Information acquired using MR temperature mapping and thermal property measurements can assess RF/microwave safety with high resolution and fidelity. PMID:25424724

Magnetic resonance imaging in evaluating workers' compensation patients.

PubMed

Babbel, Daniel; Rayan, Ghazi

2012-04-01

We studied the utility of magnetic resonance imaging (MRI) studies for workers' compensation patients with hand conditions in which the referring doctor obtained the images. We compared the MRI findings with the eventual clinical findings. We also investigated the approximate cost of these MRI studies. We retrospectively reviewed the charts of all workers' compensation patients seen in a hand and upper extremity practice over the course of 3 years. We selected patients who had MRI studies of the affected upper extremities before referral to the senior author (G.R.). We reviewed the charts for information regarding demographics, referral diagnoses, MRI diagnoses made by the radiologist, the area of the upper extremity studied, and eventual clinical diagnoses by the senior author. We made a determination as to whether a hand surgeon could have adequately diagnosed and treated the patients' conditions without the imaging studies. We also investigated the cost associated with these MRIs. We included 62 patients with a total of 67 MRI scans in this study. The MRI studies did not contribute to clinically diagnosing the patients' conditions in any of the cases we reviewed. The hand surgeon's clinical diagnosis disagreed with the radiologist's MRI diagnosis in 63% of patients. The MRI was unnecessary to arrive at the clinical diagnosis and did not influence the treatment offered for any of the 62 patients. The total cost for the 67 non-contrast MRI studies was approximately $53,000. Costly imaging studies are frequently done to determine the validity of a patient's reported problems; unfortunately, these tests are frequently unnecessary and waste resources. Magnetic resonance imaging scans may not be the standard for accurate diagnosis and can misdirect care. Therapeutic III. Copyright © 2012 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Urography

MedlinePlus

... magnetic field of the MRI unit, metal and electronic items are not allowed in the exam room. ... tell the technologist if you have medical or electronic devices in your body. These objects may interfere ...

Attenuation correction in emission tomography using the emission data—A review

PubMed Central

Li, Yusheng

2016-01-01

The problem of attenuation correction (AC) for quantitative positron emission tomography (PET) had been considered solved to a large extent after the commercial availability of devices combining PET with computed tomography (CT) in 2001; single photon emission computed tomography (SPECT) has seen a similar development. However, stimulated in particular by technical advances toward clinical systems combining PET and magnetic resonance imaging (MRI), research interest in alternative approaches for PET AC has grown substantially in the last years. In this comprehensive literature review, the authors first present theoretical results with relevance to simultaneous reconstruction of attenuation and activity. The authors then look back at the early history of this research area especially in PET; since this history is closely interwoven with that of similar approaches in SPECT, these will also be covered. We then review algorithmic advances in PET, including analytic and iterative algorithms. The analytic approaches are either based on the Helgason–Ludwig data consistency conditions of the Radon transform, or generalizations of John’s partial differential equation; with respect to iterative methods, we discuss maximum likelihood reconstruction of attenuation and activity (MLAA), the maximum likelihood attenuation correction factors (MLACF) algorithm, and their offspring. The description of methods is followed by a structured account of applications for simultaneous reconstruction techniques: this discussion covers organ-specific applications, applications specific to PET/MRI, applications using supplemental transmission information, and motion-aware applications. After briefly summarizing SPECT applications, we consider recent developments using emission data other than unscattered photons. In summary, developments using time-of-flight (TOF) PET emission data for AC have shown promising advances and open a wide range of applications. These techniques may both remedy deficiencies of purely MRI-based AC approaches in PET/MRI and improve standalone PET imaging. PMID:26843243

Attenuation correction in emission tomography using the emission data—A review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berker, Yannick, E-mail: berker@mail.med.upenn.edu; Li, Yusheng

2016-02-15

The problem of attenuation correction (AC) for quantitative positron emission tomography (PET) had been considered solved to a large extent after the commercial availability of devices combining PET with computed tomography (CT) in 2001; single photon emission computed tomography (SPECT) has seen a similar development. However, stimulated in particular by technical advances toward clinical systems combining PET and magnetic resonance imaging (MRI), research interest in alternative approaches for PET AC has grown substantially in the last years. In this comprehensive literature review, the authors first present theoretical results with relevance to simultaneous reconstruction of attenuation and activity. The authors thenmore » look back at the early history of this research area especially in PET; since this history is closely interwoven with that of similar approaches in SPECT, these will also be covered. We then review algorithmic advances in PET, including analytic and iterative algorithms. The analytic approaches are either based on the Helgason–Ludwig data consistency conditions of the Radon transform, or generalizations of John’s partial differential equation; with respect to iterative methods, we discuss maximum likelihood reconstruction of attenuation and activity (MLAA), the maximum likelihood attenuation correction factors (MLACF) algorithm, and their offspring. The description of methods is followed by a structured account of applications for simultaneous reconstruction techniques: this discussion covers organ-specific applications, applications specific to PET/MRI, applications using supplemental transmission information, and motion-aware applications. After briefly summarizing SPECT applications, we consider recent developments using emission data other than unscattered photons. In summary, developments using time-of-flight (TOF) PET emission data for AC have shown promising advances and open a wide range of applications. These techniques may both remedy deficiencies of purely MRI-based AC approaches in PET/MRI and improve standalone PET imaging.« less

Non-invasive methods for the determination of body and carcass composition in livestock: dual-energy X-ray absorptiometry, computed tomography, magnetic resonance imaging and ultrasound: invited review.

PubMed

Scholz, A M; Bünger, L; Kongsro, J; Baulain, U; Mitchell, A D

2015-07-01

The ability to accurately measure body or carcass composition is important for performance testing, grading and finally selection or payment of meat-producing animals. Advances especially in non-invasive techniques are mainly based on the development of electronic and computer-driven methods in order to provide objective phenotypic data. The preference for a specific technique depends on the target animal species or carcass, combined with technical and practical aspects such as accuracy, reliability, cost, portability, speed, ease of use, safety and for in vivo measurements the need for fixation or sedation. The techniques rely on specific device-driven signals, which interact with tissues in the body or carcass at the atomic or molecular level, resulting in secondary or attenuated signals detected by the instruments and analyzed quantitatively. The electromagnetic signal produced by the instrument may originate from mechanical energy such as sound waves (ultrasound - US), 'photon' radiation (X-ray-computed tomography - CT, dual-energy X-ray absorptiometry - DXA) or radio frequency waves (magnetic resonance imaging - MRI). The signals detected by the corresponding instruments are processed to measure, for example, tissue depths, areas, volumes or distributions of fat, muscle (water, protein) and partly bone or bone mineral. Among the above techniques, CT is the most accurate one followed by MRI and DXA, whereas US can be used for all sizes of farm animal species even under field conditions. CT, MRI and US can provide volume data, whereas only DXA delivers immediate whole-body composition results without (2D) image manipulation. A combination of simple US and more expensive CT, MRI or DXA might be applied for farm animal selection programs in a stepwise approach.

Combined ultrasound and MR imaging to guide focused ultrasound therapies in the brain

NASA Astrophysics Data System (ADS)

Arvanitis, Costas D.; Livingstone, Margaret S.; McDannold, Nathan

2013-07-01

Several emerging therapies with potential for use in the brain, harness effects produced by acoustic cavitation—the interaction between ultrasound and microbubbles either generated during sonication or introduced into the vasculature. Systems developed for transcranial MRI-guided focused ultrasound (MRgFUS) thermal ablation can enable their clinical translation, but methods for real-time monitoring and control are currently lacking. Acoustic emissions produced during sonication can provide information about the location, strength and type of the microbubble oscillations within the ultrasound field, and they can be mapped in real-time using passive imaging approaches. Here, we tested whether such mapping can be achieved transcranially within a clinical brain MRgFUS system. We integrated an ultrasound imaging array into the hemisphere transducer of the MRgFUS device. Passive cavitation maps were obtained during sonications combined with a circulating microbubble agent at 20 targets in the cingulate cortex in three macaques. The maps were compared with MRI-evident tissue effects. The system successfully mapped microbubble activity during both stable and inertial cavitation, which was correlated with MRI-evident transient blood-brain barrier disruption and vascular damage, respectively. The location of this activity was coincident with the resulting tissue changes within the expected resolution limits of the system. While preliminary, these data clearly demonstrate, for the first time, that it is possible to construct maps of stable and inertial cavitation transcranially, in a large animal model, and under clinically relevant conditions. Further, these results suggest that this hybrid ultrasound/MRI approach can provide comprehensive guidance for targeted drug delivery via blood-brain barrier disruption and other emerging ultrasound treatments, facilitating their clinical translation. We anticipate that it will also prove to be an important research tool that will further the development of a broad range of microbubble-enhanced therapies.

Magnet dislocation: an increasing and serious complication following MRI in patients with cochlear implants.

PubMed

Hassepass, F; Stabenau, V; Arndt, S; Beck, R; Bulla, S; Grauvogel, T; Aschendorff, A

2014-07-01

Cochlear implantation (CI) represents the gold standard in the treatment of children born deaf and postlingually deafened adults. Initial magnetic resonance imaging (MRI) was contraindicated in CI users. Meanwhile, there are specific recommendations concerning MRI compatibility depending on the type of CI system and the device manufacturer. Some CI systems are even approved for MRI with the internal magnet left in place. The aim of this study was to analyze all magnet revision surgeries in CI patients at one CI center and the relationship to MRI scans over time. Between 2000 and 2013, a total of 2027 CIs were implanted. The number of magnet dislocation (MD) surgeries and their causes was assessed retrospectively. In total 12 cases of MD resulting from an MRI scan (0.59 %) were observed, accounting for 52.2 % of all magnetic revision surgeries. As per the labeling, it was considered safe to leave the internal magnet in place during MRI while following specific manufacturer recommendations: MRI intensity of 1.5 Tesla (T) and compression head bandage during examination. A compression head bandage in a 1.5 T MRI unit does not safely prevent MD and the related serious complications in CI recipients. We recommend a Stenvers view radiograph after MRI with the internal magnet in place for early identification of MD, at least in the case of pain during or after MRI examination. MRI in CI patients should be indicated with restraint and patients should be explicitly informed about the possible risks. Recommendations regarding MRI compatibility and the handling of CI patients issued with MRI for the most common CI systems are summarized. © Georg Thieme Verlag KG Stuttgart · New York.

Simultaneous PET-MRI in Oncology: A Solution Looking for a Problem?

PubMed Central

Yankeelov, Thomas E.; Peterson, Todd E.; Abramson, Richard G.; Garcia-Izquierdo, David; Arlinghaus, Lori R.; Li, Xia; Atuegwu, Nkiruka C.; Catana, Ciprian; Manning, H. Charles; Fayad, Zahi A.; Gore, John C.

2012-01-01

With the recent development of integrated positron emission tomography-magnetic resonance imaging (PET-MRI) scanners, new possibilities for quantitative molecular imaging of cancer are realized. However, the practical advantages and potential clinical benefits of the ability to record PET and MRI data simultaneously must be balanced against the substantial costs and other requirements of such devices. In this review we highlight several of the key areas where integrated PET-MRI measurements, obtained simultaneously, are anticipated to have a significant impact on clinical and/or research studies. These areas include the use of MR-based motion corrections and/or a priori anatomical information for improved reconstruction of PET data; improved arterial input function characterization for PET kinetic modeling; the use of dual-modality contrast agents; and patient comfort and practical convenience. For widespread acceptance, a compelling case could be made if the combination of quantitative MRI and specific PET biomarkers significantly improves our ability to assess tumor status and response to therapy, and some likely candidates are now emerging. We consider the relative advantages and disadvantages afforded by PET-MRI and summarize current opinions and evidence as to the likely value of PET-MRI in the management of cancer. PMID:22795930

MR Enterography

MedlinePlus

... magnetic field of the MRI unit, metal and electronic items are not allowed in the exam room. ... tell the technologist if you have medical or electronic devices in your body. These objects may interfere ...

SQUIDs vs. Faraday coils for ultlra-low field nuclear magnetic resonance: experimental and simulation comparison

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matlashov, Andrei N; Espy, Michelle A; Kraus, Robert H

2010-01-01

Nuclear magnetic resonance (NMR) methods are widely used in medicine, chemistry and industry. One application area is magnetic resonance imaging or MRI. Recently it has become possible to perform NMR and MRI in ultra-low field (ULF) regime that requires measurement field strengths only of the order of 1 Gauss. These techniques exploit the advantages offered by superconducting quantum interference devices or SQUIDs. Our group at LANL has built SQUID based MRI systems for brain imaging and for liquid explosives detection at airports security checkpoints. The requirement for liquid helium cooling limits potential applications of ULF MRI for liquid identification andmore » security purposes. Our experimental comparative investigation shows that room temperature inductive magnetometers provide enough sensitivity in the 3-10 kHz range and can be used for fast liquid explosives detection based on ULF NMR/MRI technique. We describe an experimental and computer simulation comparison of the world's first multichannel SQUID based and Faraday coils based instruments that are capable of performing ULF MRI for liquids identification.« less

Development of an MRI-compatible digital SiPM detector stack for simultaneous PET/MRI.

PubMed

Düppenbecker, Peter M; Weissler, Bjoern; Gebhardt, Pierre; Schug, David; Wehner, Jakob; Marsden, Paul K; Schulz, Volkmar

2016-02-01

Advances in solid-state photon detectors paved the way to combine positron emission tomography (PET) and magnetic resonance imaging (MRI) into highly integrated, truly simultaneous, hybrid imaging systems. Based on the most recent digital SiPM technology, we developed an MRI-compatible PET detector stack, intended as a building block for next generation simultaneous PET/MRI systems. Our detector stack comprises an array of 8 × 8 digital SiPM channels with 4 mm pitch using Philips Digital Photon Counting DPC 3200-22 devices, an FPGA for data acquisition, a supply voltage control system and a cooling infrastructure. This is the first detector design that allows the operation of digital SiPMs simultaneously inside an MRI system. We tested and optimized the MRI-compatibility of our detector stack on a laboratory test bench as well as in combination with a Philips Achieva 3 T MRI system. Our design clearly reduces distortions of the static magnetic field compared to a conventional design. The MRI static magnetic field causes weak and directional drift effects on voltage regulators, but has no direct impact on detector performance. MRI gradient switching initially degraded energy and timing resolution. Both distortions could be ascribed to voltage variations induced on the bias and the FPGA core voltage supply respectively. Based on these findings, we improved our detector design and our final design shows virtually no energy or timing degradations, even during heavy and continuous MRI gradient switching. In particular, we found no evidence that the performance of the DPC 3200-22 digital SiPM itself is degraded by the MRI system.

Biomedical Investigations with Laser-Polarized Noble Gas Magnetic Resonance

NASA Technical Reports Server (NTRS)

Walsworth, Ronald L.

2001-01-01

We are developing laser-polarized noble gas nuclear magnetic resonance (NMR) as a novel biomedical imaging tool for ground-based and eventually space-based application. This emerging multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI) (e.g., of lung ventilation) as well as studies of tissue perfusion. In addition, laser-polarized noble gases (He-3 and Xe-129) do not require a large magnetic field for sensitive detection, opening the door to practical MRI at very low magnetic fields with an open, lightweight, and low-power device. We are pursuing two specific aims in this research. The first aim is to develop a low-field (< 0.01 T) instrument for noble gas MRI of humans, and the second aim is to develop functional MRI of the lung using laser-polarized Xe-129 and related techniques.

Diagnosis and management of transfusion iron overload: The role of imaging

PubMed Central

Wood, John C.

2010-01-01

The characterization of iron stores is important to prevent and treat iron overload. Serum markers such as ferritin, serum iron, iron binding capacity, transferrin saturation, and nontransferrin-bound iron can be used to follow trends in iron status; however, variability in these markers limits predictive power for any given individual. Liver iron represents the best single marker of total iron balance. Measures of liver iron include biopsy, superconducting quantum interference device, computer tomography, and magnetic resonance imaging (MRI). MRI is the most accurate and widely available noninvasive tool to assess liver iron. The main advantages of MRI include a low-rate of variability between measurements and the ability to assess iron loading in endocrine tissues, the heart and the liver. This manuscript describes the principles, validation, and clinical utility of MRI for tissue iron estimation. PMID:17963249

Compact Intraoperative MRI: Stereotactic Accuracy and Future Directions.

PubMed

Markowitz, Daniel; Lin, Dishen; Salas, Sussan; Kohn, Nina; Schulder, Michael

2017-01-01

Intraoperative imaging must supply data that can be used for accurate stereotactic navigation. This information should be at least as accurate as that acquired from diagnostic imagers. The aim of this study was to compare the stereotactic accuracy of an updated compact intraoperative MRI (iMRI) device based on a 0.15-T magnet to standard surgical navigation on a 1.5-T diagnostic scan MRI and to navigation with an earlier model of the same system. The accuracy of each system was assessed using a water-filled phantom model of the brain. Data collected with the new system were compared to those obtained in a previous study assessing the older system. The accuracy of the new iMRI was measured against standard surgical navigation on a 1.5-T MRI using T1-weighted (W) images. The mean error with the iMRI using T1W images was lower than that based on images from the 1.5-T scan (1.24 vs. 2.43 mm). T2W images from the newer iMRI yielded a lower navigation error than those acquired with the prior model (1.28 vs. 3.15 mm). Improvements in magnet design can yield progressive increases in accuracy, validating the concept of compact, low-field iMRI. Avoiding the need for registration between image and surgical space increases navigation accuracy. © 2017 S. Karger AG, Basel.

A delivery device for presentation of tactile stimuli during functional magnetic resonance imaging.

PubMed

Dykes, Robert W; Miqueé, Aline; Xerri, Christian; Zennou-Azogui, Yoh'i; Rainville, Constant; Dumoulin, André; Marineau, Daniel

2007-01-30

We describe a novel stimulus delivery system designed to present tactile stimuli to a subject in the tunnel of a magnetic resonance imaging (MRI) system. Using energy from an air-driven piston to turn a wheel, the device advances a conveyor belt with a pre-determined sequence of stimuli that differ in their spatial features into the tunnel of the MRI. The positioning of one or several stimulus objects in a window near the subject's hand is controlled by a photoelectric device that detects periodic openings in the conveyor belt. Using this electric signal to position each presentation avoids cumulative positioning errors and provides a signal related to the progression of the experiment. We used a series of shapes that differed in their spatial features but the device could carry stimuli with a diversity of shapes and textures. This flexibility allows the experimenter to design a wide variety of psychophysical experiments in the haptic world and possibly to compare and contrast these stimuli with the cognitive treatment of similar stimuli delivered to the other senses. Appropriate experimental design allows separation of motor, sensory and memory storage phases of mental processes.

A magnetic compatible supernumerary robotic finger for functional magnetic resonance imaging (fMRI) acquisitions: Device description and preliminary results.

PubMed

Hussain, Irfan; Santarnecchi, Emiliano; Leo, Andrea; Ricciardi, Emiliano; Rossi, Simone; Prattichizzo, Domenico

2017-07-01

The Supernumerary robotic limbs are a recently introduced class of wearable robots that, differently from traditional prostheses and exoskeletons, aim at adding extra effectors (i.e., arms, legs, or fingers) to the human user, rather than substituting or enhancing the natural ones. However, it is still undefined whether the use of supernumerary robotic limbs could specifically lead to neural modifications in brain dynamics. The illusion of owning the part of body has been already proven in many experimental observations, such as those relying on multisensory integration (e.g., rubber hand illusion), prosthesis and even on virtual reality. In this paper we present a description of a novel magnetic compatible supernumerary robotic finger together with preliminary observations from two functional magnetic resonance imaging (fMRI) experiments, in which brain activity was measured before and after a period of training with the robotic device, and during the use of the novel MRI-compatible version of the supernumerary robotic finger. Results showed that the usage of the MR-compatible robotic finger is safe and does not produce artifacts on MRI images. Moreover, the training with the supernumerary robotic finger recruits a network of motor-related cortical regions (i.e. primary and supplementary motor areas), hence the same motor network of a fully physiological voluntary motor gestures.

SQUIDs vs. Induction Coils for Ultra-Low Field Nuclear Magnetic Resonance: Experimental and Simulation Comparison

PubMed Central

Matlashov, Andrei N.; Schultz, Larry J.; Espy, Michelle A.; Kraus, Robert H.; Savukov, Igor M.; Volegov, Petr L.; Wurden, Caroline J.

2011-01-01

Nuclear magnetic resonance (NMR) is widely used in medicine, chemistry and industry. One application area is magnetic resonance imaging (MRI). Recently it has become possible to perform NMR and MRI in the ultra-low field (ULF) regime requiring measurement field strengths of the order of only 1 Gauss. This technique exploits the advantages offered by superconducting quantum interference devices or SQUIDs. Our group has built SQUID based MRI systems for brain imaging and for liquid explosives detection at airport security checkpoints. The requirement for liquid helium cooling limits potential applications of ULF MRI for liquid identification and security purposes. Our experimental comparative investigation shows that room temperature inductive magnetometers may provide enough sensitivity in the 3–10 kHz range and can be used for fast liquid explosives detection based on ULF NMR technique. We describe experimental and computer-simulation results comparing multichannel SQUID based and induction coils based instruments that are capable of performing ULF MRI for liquid identification. PMID:21747638

A review of magnetic resonance imaging compatible manipulators in surgery.

PubMed

Elhawary, H; Zivanovic, A; Davies, B; Lampérth, M

2006-04-01

Developments in magnetic resonance imaging (MRI), coupled with parallel progress in the field of computer-assisted surgery, mean that an ideal environment has been created for the development of MRI-compatible robotic systems and manipulators, capable of enhancing many types of surgical procedure. However, MRI does impose severe restrictions on mechatronic devices to be used in or around the scanners. In this article a review of the developments in the field of MRI-compatible surgical manipulators over the last decade is presented. The manipulators developed make use of different methods of actuation, but they can be reduced to four main groups: actuation transmitted through hydraulics, pneumatic actuators, ultrasonic motors based on the piezoceramic principle and remote manual actuation. Progress has been made concerning material selection, position sensing, and different actuation techniques, and design strategies have been implemented to overcome the multiple restrictions imposed by the MRI environment. Most systems lack the clinical validation needed to continue on to commercial products.

Voluntary Enhancement of Neural Signatures of Affiliative Emotion Using fMRI Neurofeedback

PubMed Central

Moll, Jorge; Weingartner, Julie H.; Bado, Patricia; Basilio, Rodrigo; Sato, João R.; Melo, Bruno R.; Bramati, Ivanei E.; de Oliveira-Souza, Ricardo; Zahn, Roland

2014-01-01

In Ridley Scott’s film “Blade Runner”, empathy-detection devices are employed to measure affiliative emotions. Despite recent neurocomputational advances, it is unknown whether brain signatures of affiliative emotions, such as tenderness/affection, can be decoded and voluntarily modulated. Here, we employed multivariate voxel pattern analysis and real-time fMRI to address this question. We found that participants were able to use visual feedback based on decoded fMRI patterns as a neurofeedback signal to increase brain activation characteristic of tenderness/affection relative to pride, an equally complex control emotion. Such improvement was not observed in a control group performing the same fMRI task without neurofeedback. Furthermore, the neurofeedback-driven enhancement of tenderness/affection-related distributed patterns was associated with local fMRI responses in the septohypothalamic area and frontopolar cortex, regions previously implicated in affiliative emotion. This demonstrates that humans can voluntarily enhance brain signatures of tenderness/affection, unlocking new possibilities for promoting prosocial emotions and countering antisocial behavior. PMID:24847819

Less head motion during MRI under task than resting-state conditions.

PubMed

Huijbers, Willem; Van Dijk, Koene R A; Boenniger, Meta M; Stirnberg, Rüdiger; Breteler, Monique M B

2017-02-15

Head motion reduces data quality of neuroimaging data. In three functional magnetic resonance imaging (MRI) experiments we demonstrate that people make less head movements under task than resting-state conditions. In Experiment 1, we observed less head motion during a memory encoding task than during the resting-state condition. In Experiment 2, using publicly shared data from the UCLA Consortium for Neuropsychiatric Phenomics LA5c Study, we again found less head motion during several active task conditions than during a resting-state condition, although some task conditions also showed comparable motion. In the healthy controls, we found more head motion in men than in women and more motion with increasing age. When comparing clinical groups, we found that patients with a clinical diagnosis of bipolar disorder, or schizophrenia, move more compared to healthy controls or patients with ADHD. Both these experiments had a fixed acquisition order across participants, and we could not rule out that a first or last scan during a session might be particularly prone to more head motion. Therefore, we conducted Experiment 3, in which we collected several task and resting-state fMRI runs with an acquisition order counter-balanced. The results of Experiment 3 show again less head motion during several task conditions than during rest. Together these experiments demonstrate that small head motions occur during MRI even with careful instruction to remain still and fixation with foam pillows, but that head motion is lower when participants are engaged in a cognitive task. These finding may inform the choice of functional runs when studying difficult-to-scan populations, such as children or certain patient populations. Our findings also indicate that differences in head motion complicate direct comparisons of measures of functional neuronal networks between task and resting-state fMRI because of potential differences in data quality. In practice, a task to reduce head motion might be especially useful when acquiring structural MRI data such as T1/T2-weighted and diffusion MRI in research and clinical settings. Copyright © 2016 Elsevier Inc. All rights reserved.

Aphasia

MedlinePlus

... of speech-generating applications on mobile devices like tablets can also provide an alternative way to communicate ... on using advanced imaging methods, such as functional magnetic resonance imaging (fMRI), to explore how language is processed in ...

Diffusion tensor and volumetric magnetic resonance imaging using an MR-compatible hand-induced robotic device suggests training-induced neuroplasticity in patients with chronic stroke

PubMed Central

LAZARIDOU, ASIMINA; ASTRAKAS, LOUKAS; MINTZOPOULOS, DIONYSSIOS; KHANICHEH, AZADEH; SINGHAL, ANEESH B.; MOSKOWITZ, MICHAEL A.; ROSEN, BRUCE; TZIKA, ARIA A.

2013-01-01

Stroke is the third leading cause of mortality and a frequent cause of long-term adult impairment. Improved strategies to enhance motor function in individuals with chronic disability from stroke are thus required. Post-stroke therapy may improve rehabilitation and reduce long-term disability; however, objective methods for evaluating the specific impact of rehabilitation are rare. Brain imaging studies on patients with chronic stroke have shown evidence for reorganization of areas showing functional plasticity after a stroke. In this study, we hypothesized that brain mapping using a novel magnetic resonance (MR)-compatible hand device in conjunction with state-of-the-art magnetic resonance imaging (MRI) can serve as a novel biomarker for brain plasticity induced by rehabilitative motor training in patients with chronic stroke. This hypothesis is based on the premises that robotic devices, by stimulating brain plasticity, can assist in restoring movement compromised by stroke-induced pathological changes in the brain and that these changes can then be monitored by advanced MRI. We serially examined 15 healthy controls and 4 patients with chronic stroke. We employed a combination of diffusion tensor imaging (DTI) and volumetric MRI using a 3-tesla (3T) MRI system using a 12-channel Siemens Tim coil and a novel MR-compatible hand-induced robotic device. DTI data revealed that the number of fibers and the average tract length significantly increased after 8 weeks of hand training by 110% and 64%, respectively (p<0.001). New corticospinal tract (CST) fibers projecting progressively closer to the motor cortex appeared during training. Volumetric data analysis showed a statistically significant increase in the cortical thickness of the ventral postcentral gyrus areas of patients after training relative to pre-training cortical thickness (p<0.001). We suggest that rehabilitation is possible for a longer period of time after stroke than previously thought, showing that structural plasticity is possible even after 6 months due to retained neuroplasticity. Our study is an example of personalized medicine using advanced neuroimaging methods in conjunction with robotics in the molecular medicine era. PMID:23982596

Integrated microchip incorporating atomic magnetometer and microfluidic channel for NMR and MRI

DOEpatents

Ledbetter, Micah P [Oakland, CA; Savukov, Igor M [Los Alamos, NM; Budker, Dmitry [El Cerrito, CA; Shah, Vishal K [Plainsboro, NJ; Knappe, Svenja [Boulder, CO; Kitching, John [Boulder, CO; Michalak, David J [Berkeley, CA; Xu, Shoujun [Houston, TX; Pines, Alexander [Berkeley, CA

2011-08-09

An integral microfluidic device includes an alkali vapor cell and microfluidic channel, which can be used to detect magnetism for nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). Small magnetic fields in the vicinity of the vapor cell can be measured by optically polarizing and probing the spin precession in the small magnetic field. This can then be used to detect the magnetic field of in encoded analyte in the adjacent microfluidic channel. The magnetism in the microfluidic channel can be modulated by applying an appropriate series of radio or audio frequency pulses upstream from the microfluidic chip (the remote detection modality) to yield a sensitive means of detecting NMR and MRI.

A dual-mode hemispherical sparse array for 3D passive acoustic mapping and skull localization within a clinical MRI guided focused ultrasound device

NASA Astrophysics Data System (ADS)

Crake, Calum; Brinker, Spencer T.; Coviello, Christian M.; Livingstone, Margaret S.; McDannold, Nathan J.

2018-03-01

Previous work has demonstrated that passive acoustic imaging may be used alongside MRI for monitoring of focused ultrasound therapy. However, past implementations have generally made use of either linear arrays originally designed for diagnostic imaging or custom narrowband arrays specific to in-house therapeutic transducer designs, neither of which is fully compatible with clinical MR-guided focused ultrasound (MRgFUS) devices. Here we have designed an array which is suitable for use within an FDA-approved MR-guided transcranial focused ultrasound device, within the bore of a 3 Tesla clinical MRI scanner. The array is constructed from 5  ×  0.4 mm piezoceramic disc elements arranged in pseudorandom fashion on a low-profile laser-cut acrylic frame designed to fit between the therapeutic elements of a 230 kHz InSightec ExAblate 4000 transducer. By exploiting thickness and radial resonance modes of the piezo discs the array is capable of both B-mode imaging at 5 MHz for skull localization, as well as passive reception at the second harmonic of the therapy array for detection of cavitation and 3D passive acoustic imaging. In active mode, the array was able to perform B-mode imaging of a human skull, showing the outer skull surface with good qualitative agreement with MR imaging. Extension to 3D showed the array was able to locate the skull within  ±2 mm/2° of reference points derived from MRI, which could potentially allow registration of a patient to the therapy system without the expense of real-time MRI. In passive mode, the array was able to resolve a point source in 3D within a  ±10 mm region about each axis from the focus, detect cavitation (SNR ~ 12 dB) at burst lengths from 10 cycles to continuous wave, and produce 3D acoustic maps in a flow phantom. Finally, the array was used to detect and map cavitation associated with microbubble activity in the brain in nonhuman primates.

Breast MRI: EUSOBI recommendations for women's information.

PubMed

Mann, Ritse M; Balleyguier, Corinne; Baltzer, Pascal A; Bick, Ulrich; Colin, Catherine; Cornford, Eleanor; Evans, Andrew; Fallenberg, Eva; Forrai, Gabor; Fuchsjäger, Michael H; Gilbert, Fiona J; Helbich, Thomas H; Heywang-Köbrunner, Sylvia H; Camps-Herrero, Julia; Kuhl, Christiane K; Martincich, Laura; Pediconi, Federica; Panizza, Pietro; Pina, Luis J; Pijnappel, Ruud M; Pinker-Domenig, Katja; Skaane, Per; Sardanelli, Francesco

2015-12-01

This paper summarizes information about breast MRI to be provided to women and referring physicians. After listing contraindications, procedure details are described, stressing the need for correct scheduling and not moving during the examination. The structured report including BI-RADS® categories and further actions after a breast MRI examination are discussed. Breast MRI is a very sensitive modality, significantly improving screening in high-risk women. It also has a role in clinical diagnosis, problem solving, and staging, impacting on patient management. However, it is not a perfect test, and occasionally breast cancers can be missed. Therefore, clinical and other imaging findings (from mammography/ultrasound) should also be considered. Conversely, MRI may detect lesions not visible on other imaging modalities turning out to be benign (false positives). These risks should be discussed with women before a breast MRI is requested/performed. Because breast MRI drawbacks depend upon the indication for the examination, basic information for the most important breast MRI indications is presented. Seventeen notes and five frequently asked questions formulated for use as direct communication to women are provided. The text was reviewed by Europa Donna-The European Breast Cancer Coalition to ensure that it can be easily understood by women undergoing MRI. • Information on breast MRI concerns advantages/disadvantages and preparation to the examination • Claustrophobia, implantable devices, allergic predisposition, and renal function should be checked • Before menopause, scheduling on day 7-14 of the cycle is preferred • During the examination, it is highly important that the patient keeps still • Availability of prior examinations improves accuracy of breast MRI interpretation.

Development and preliminary evaluation of an ultrasonic motor actuated needle guide for 3T MRI-guided transperineal prostate interventions

NASA Astrophysics Data System (ADS)

Song, Sang-Eun; Tokuda, Junichi; Tuncali, Kemal; Tempany, Clare; Hata, Nobuhiko

2012-02-01

Image guided prostate interventions have been accelerated by Magnetic Resonance Imaging (MRI) and robotic technologies in the past few years. However, transrectal ultrasound (TRUS) guided procedure still remains as vast majority in clinical practice due to engineering and clinical complexity of the MRI-guided robotic interventions. Subsequently, great advantages and increasing availability of MRI have not been utilized at its maximum capacity in clinic. To benefit patients from the advantages of MRI, we developed an MRI-compatible motorized needle guide device "Smart Template" that resembles a conventional prostate template to perform MRI-guided prostate interventions with minimal changes in the clinical procedure. The requirements and specifications of the Smart Template were identified from our latest MRI-guided intervention system that has been clinically used in manual mode for prostate biopsy. Smart Template consists of vertical and horizontal crossbars that are driven by two ultrasonic motors via timing-belt and mitergear transmissions. Navigation software that controls the crossbar position to provide needle insertion positions was also developed. The software can be operated independently or interactively with an open-source navigation software, 3D Slicer, that has been developed for prostate intervention. As preliminary evaluation, MRI distortion and SNR test were conducted. Significant MRI distortion was found close to the threaded brass alloy components of the template. However, the affected volume was limited outside the clinical region of interest. SNR values over routine MRI scan sequences for prostate biopsy indicated insignificant image degradation during the presence of the robotic system and actuation of the ultrasonic motors.

A Look from the Inside

NASA Technical Reports Server (NTRS)

2004-01-01

NASA's Hubble Space Telescope has given the world amazing images of the distant stars, planets, and galaxies. The cutting-edge imaging technology that enhances the Hubble images also extends its benefits to life here on Earth, from deciphering previously unreadable portions of the Dead Sea Scrolls to improving digital mammographies for advanced cancer detection. This imaging technology is now helping physicians to perform micro-invasive arthroscopic surgery, which is the visual examination of an interior joint such as the knee. In 1997, NASA's Glenn Research Center signed a Space Act Agreement with Micro Medical Devices, Inc. (MMD), a medical device engineering company that licenses miniature surgical devices. At that time, MMD was in the process of developing a new micro-endoscope. This tool enables surgeons to view what is happening inside the body on a screen, eliminating the need for a more invasive diagnostic procedure. The images from the micro-endoscope needed to be extremely clear, a challenge with the tool s small size. The images also needed to be viewed in real time to allow surgeons to see what was happening in the body at that very moment. MMD established Clear Image Technology, LLC, of Elyria, Ohio, to commercialize the miniature endoscope. Clear Image Technology then partnered with Arthrotek, Inc., a sports medicine subsidiary of Biomet, Inc., to introduce the tool to the commercial market as the InnerVue[TM] Diagnostic Scope System. The InnerVue system is designed for use in a diagnostic environment, such as an office or outpatient service, to evaluate conditions within a joint. While the InnerVue scope is primarily being applied to the knee and shoulder, other small joints such as the wrist, elbow, and ankle are being investigated. A physician can use the system alone or in conjunction with magnetic resonance imaging (MRI) to determine the next treatment step for each patient. The procedure can be more accurate than MRI, particularly with diagnosing cartilage and articular surface damage and assessing arthritis severity.

A Rare Complication of Cochlear Implantation After Magnetic Resonance Imaging: Reversion of the Magnet.

PubMed

Öztürk, Erkan; Doruk, Can; Orhan, Kadir Serkan; Çelik, Mehmet; Polat, Beldan; Güldiken, Yahya

2017-06-01

Cochlear implants are mechanical devices used for patients with severe sensory-neural hearing loss, which has an inner magnet. It is proven that 1.5 Tesla magnetic resonance imaging (MRI) scanners are safe to use in patients with cochlear implant. In our patient, the authors aim to introduce a rare complication caused after a 1.5 Tesla MRI scanning and the management of this situation; the reversion of the magnet of the implant without displacement and significance of surgery in management.

Prototype positron emission tomography insert with electro-optical signal transmission for simultaneous operation with MRI.

PubMed

Olcott, Peter; Kim, Ealgoo; Hong, Keyjo; Lee, Brian J; Grant, Alexander M; Chang, Chen-Ming; Glover, Gary; Levin, Craig S

2015-05-07

The simultaneous acquisition of PET and MRI data shows promise to provide powerful capabilities to study disease processes in human subjects, guide the development of novel treatments, and monitor therapy response and disease progression. A brain-size PET detector ring insert for an MRI system is being developed that, if successful, can be inserted into any existing MRI system to enable simultaneous PET and MRI images of the brain to be acquired without mutual interference. The PET insert uses electro-optical coupling to relay all the signals from the PET detectors out of the MRI system using analog modulated lasers coupled to fiber optics. Because the fibers use light instead of electrical signals, the PET detector can be electrically decoupled from the MRI making it partially transmissive to the RF field of the MRI. The SiPM devices and low power lasers were powered using non-magnetic MRI compatible batteries. Also, the number of laser-fiber channels in the system was reduced using techniques adapted from the field of compressed sensing. Using the fact that incoming PET data is sparse in time and space, electronic circuits implementing constant weight codes uniquely encode the detector signals in order to reduce the number of electro-optical readout channels by 8-fold. Two out of a total of sixteen electro-optical detector modules have been built and tested with the entire RF-shielded detector gantry for the PET ring insert. The two detectors have been tested outside and inside of a 3T MRI system to study mutual interference effects and simultaneous performance with MRI. Preliminary results show that the PET insert is feasible for high resolution simultaneous PET/MRI imaging for applications in the brain.

Prototype positron emission tomography insert with electro-optical signal transmission for simultaneous operation with MRI

NASA Astrophysics Data System (ADS)

Olcott, Peter; Kim, Ealgoo; Hong, Keyjo; Lee, Brian J.; Grant, Alexander M.; Chang, Chen-Ming; Glover, Gary; Levin, Craig S.

2015-05-01

The simultaneous acquisition of PET and MRI data shows promise to provide powerful capabilities to study disease processes in human subjects, guide the development of novel treatments, and monitor therapy response and disease progression. A brain-size PET detector ring insert for an MRI system is being developed that, if successful, can be inserted into any existing MRI system to enable simultaneous PET and MRI images of the brain to be acquired without mutual interference. The PET insert uses electro-optical coupling to relay all the signals from the PET detectors out of the MRI system using analog modulated lasers coupled to fiber optics. Because the fibers use light instead of electrical signals, the PET detector can be electrically decoupled from the MRI making it partially transmissive to the RF field of the MRI. The SiPM devices and low power lasers were powered using non-magnetic MRI compatible batteries. Also, the number of laser-fiber channels in the system was reduced using techniques adapted from the field of compressed sensing. Using the fact that incoming PET data is sparse in time and space, electronic circuits implementing constant weight codes uniquely encode the detector signals in order to reduce the number of electro-optical readout channels by 8-fold. Two out of a total of sixteen electro-optical detector modules have been built and tested with the entire RF-shielded detector gantry for the PET ring insert. The two detectors have been tested outside and inside of a 3T MRI system to study mutual interference effects and simultaneous performance with MRI. Preliminary results show that the PET insert is feasible for high resolution simultaneous PET/MRI imaging for applications in the brain.

Development of an MRI-compatible digital SiPM detector stack for simultaneous PET/MRI

PubMed Central

Düppenbecker, Peter M; Weissler, Bjoern; Gebhardt, Pierre; Schug, David; Wehner, Jakob; Marsden, Paul K; Schulz, Volkmar

2016-01-01

Abstract Advances in solid-state photon detectors paved the way to combine positron emission tomography (PET) and magnetic resonance imaging (MRI) into highly integrated, truly simultaneous, hybrid imaging systems. Based on the most recent digital SiPM technology, we developed an MRI-compatible PET detector stack, intended as a building block for next generation simultaneous PET/MRI systems. Our detector stack comprises an array of 8 × 8 digital SiPM channels with 4 mm pitch using Philips Digital Photon Counting DPC 3200-22 devices, an FPGA for data acquisition, a supply voltage control system and a cooling infrastructure. This is the first detector design that allows the operation of digital SiPMs simultaneously inside an MRI system. We tested and optimized the MRI-compatibility of our detector stack on a laboratory test bench as well as in combination with a Philips Achieva 3 T MRI system. Our design clearly reduces distortions of the static magnetic field compared to a conventional design. The MRI static magnetic field causes weak and directional drift effects on voltage regulators, but has no direct impact on detector performance. MRI gradient switching initially degraded energy and timing resolution. Both distortions could be ascribed to voltage variations induced on the bias and the FPGA core voltage supply respectively. Based on these findings, we improved our detector design and our final design shows virtually no energy or timing degradations, even during heavy and continuous MRI gradient switching. In particular, we found no evidence that the performance of the DPC 3200-22 digital SiPM itself is degraded by the MRI system. PMID:28458919

A Computer Vision System forLocating and Identifying Internal Log Defects Using CT Imagery

Treesearch

Dongping Zhu; Richard W. Conners; Frederick Lamb; Philip A. Araman

1991-01-01

A number of researchers have shown the ability of magnetic resonance imaging (MRI) and computer tomography (CT) imaging to detect internal defects in logs. However, if these devices are ever to play a role in the forest products industry, automatic methods for analyzing data from these devices must be developed. This paper reports research aimed at developing a...

MRI-guided procedures in various regions of the body using a robotic assistance system in a closed-bore scanner: preliminary clinical experience and limitations.

PubMed

Moche, Michael; Zajonz, Dirk; Kahn, Thomas; Busse, Harald

2010-04-01

To present the clinical setup and workflow of a robotic assistance system for image-guided interventions in a conventional magnetic resonance imaging (MRI) environment and to report our preliminary clinical experience with percutaneous biopsies in various body regions. The MR-compatible, servo-pneumatically driven, robotic device (Innomotion) fits into the 60-cm bore of a standard MR scanner. The needle placement (n = 25) accuracy was estimated by measuring the 3D deviation between needle tip and prescribed target point in a phantom. Percutaneous biopsies in six patients and different body regions were planned by graphically selecting entry and target points on intraoperatively acquired roadmap MR data. For insertion depths between 29 and 95 mm, the average 3D needle deviation was 2.2 +/- 0.7 mm (range 0.9-3.8 mm). Patients with a body mass index of up to approximately 30 kg/m(2) fitted into the bore with the device. Clinical work steps and limitations are reported for the various applications. All biopsies were diagnostic and could be completed without any major complications. Median planning and intervention times were 25 (range 20-36) and 44 (36-68) minutes, respectively. Preliminary clinical results in a standard MRI environment suggest that the presented robotic device provides accurate guidance for percutaneous procedures in various body regions. Shorter procedure times may be achievable by optimizing technical and workflow aspects. (c) 2010 Wiley-Liss, Inc.

Magnetic resonance imaging - A troubleshooter in obstetric emergencies: A pictorial review

PubMed Central

Gupta, Rohini; Bajaj, Sunil Kumar; Kumar, Nishith; Chandra, Ranjan; Misra, Ritu Nair; Malik, Amita; Thukral, Brij Bhushan

2016-01-01

The application of magnetic resonance imaging (MRI) in pregnancy faced initial skepticism of physicians because of fetal safety concerns. The perceived fetal risk has been found to be unwarranted and of late, the modality has attained acceptability. Its role in diagnosing fetal anomalies is well recognized and following its safety certification in pregnancy, it is finding increasing utilization during pregnancy and puerperium. However, the use of MRI in maternal emergency obstetric conditions is relatively limited as it is still evolving. In early gestation, ectopic implantation is one of the major life-threatening conditions that are frequently encountered. Although ultrasound (USG) is the accepted mainstay modality, the diagnostic predicament persists in many cases. MRI has a role where USG is indeterminate, particularly in the extratubal ectopic pregnancy. Later in gestation, MRI can be a useful adjunct in placental disorders like previa, abruption, and adhesion. It is a good problem-solving tool in adnexal masses such as ovarian torsion and degenerated fibroid, which have a higher incidence during pregnancy. Catastrophic conditions like uterine rupture can also be preoperatively and timely diagnosed. MRI has a definite role to play in postpartum and post-abortion life-threatening conditions, e.g., retained products of conception, and gestational trophoblastic disease, especially when USG is inconclusive or inadequate. PMID:27081223

An optimized microfabricated platform for the optical generation and detection of hyperpolarized 129Xe

PubMed Central

Kennedy, Daniel J.; Seltzer, Scott J.; Jiménez-Martínez, Ricardo; Ring, Hattie L.; Malecek, Nicolas S.; Knappe, Svenja; Donley, Elizabeth A.; Kitching, John; Bajaj, Vikram S.; Pines, Alexander

2017-01-01

Low thermal-equilibrium nuclear spin polarizations and the need for sophisticated instrumentation render conventional nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) incompatible with small-scale microfluidic devices. Hyperpolarized 129Xe gas has found use in the study of many materials but has required very large and expensive instrumentation. Recently a microfabricated device with modest instrumentation demonstrated all-optical hyperpolarization and detection of 129Xe gas. This device was limited by 129Xe polarizations less than 1%, 129Xe NMR signals smaller than 20 nT, and transport of hyperpolarized 129Xe over millimeter lengths. Higher polarizations, versatile detection schemes, and flow of 129Xe over larger distances are desirable for wider applications. Here we demonstrate an ultra-sensitive microfabricated platform that achieves 129Xe polarizations reaching 7%, NMR signals exceeding 1 μT, lifetimes up to 6 s, and simultaneous two-mode detection, consisting of a high-sensitivity in situ channel with signal-to-noise of 105 and a lower-sensitivity ex situ detection channel which may be useful in a wider variety of conditions. 129Xe is hyperpolarized and detected in locations more than 1 cm apart. Our versatile device is an optimal platform for microfluidic magnetic resonance in particular, but equally attractive for wider nuclear spin applications benefitting from ultra-sensitive detection, long coherences, and simple instrumentation. PMID:28266629

An optimized microfabricated platform for the optical generation and detection of hyperpolarized 129Xe

DOE PAGES

Kennedy, Daniel J.; Seltzer, Scott J.; Jiménez-Martínez, Ricardo; ...

2017-03-07

Low thermal-equilibrium nuclear spin polarizations and the need for sophisticated instrumentation render conventional nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) incompatible with small-scale microfluidic devices. Hyperpolarized 129Xe gas has found use in the study of many materials but has required very large and expensive instrumentation. Recently a microfabricated device with modest instrumentation demonstrated all-optical hyperpolarization and detection of 129Xe gas. This device was limited by 129Xe polarizations less than 1%, 129Xe NMR signals smaller than 20 nT, and transport of hyperpolarized 129Xe over millimeter lengths. Higher polarizations, versatile detection schemes, and flow of 129Xe over larger distances are desirablemore » for wider applications. Here we demonstrate an ultra-sensitive microfabricated platform that achieves 129Xe polarizations reaching 7%, NMR signals exceeding 1 μT, lifetimes up to 6 s, and simultaneous two-mode detection, consisting of a high-sensitivity in situ channel with signal-to-noise of 10 5 and a lower-sensitivity ex situ detection channel which may be useful in a wider variety of conditions. 129Xe is hyperpolarized and detected in locations more than 1 cm apart. Our versatile device is an optimal platform for microfluidic magnetic resonance in particular, but equally attractive for wider nuclear spin applications benefitting from ultra-sensitive detection, long coherences, and simple instrumentation.« less

Robotic-assisted real-time MRI-guided TAVR: from system deployment to in vivo experiment in swine model.

PubMed

Chan, Joshua L; Mazilu, Dumitru; Miller, Justin G; Hunt, Timothy; Horvath, Keith A; Li, Ming

2016-10-01

Real-time magnetic resonance imaging (rtMRI) guidance provides significant advantages during transcatheter aortic valve replacement (TAVR) as it provides superior real-time visualization and accurate device delivery tracking. However, performing a TAVR within an MRI scanner remains difficult due to a constrained procedural environment. To address these concerns, a magnetic resonance (MR)-compatible robotic system to assist in TAVR deployments was developed. This study evaluates the technical design and interface considerations of an MR-compatible robotic-assisted TAVR system with the purpose of demonstrating that such a system can be developed and executed safely and precisely in a preclinical model. An MR-compatible robotic surgical assistant system was built for TAVR deployment. This system integrates a 5-degrees of freedom (DoF) robotic arm with a 3-DoF robotic valve delivery module. A user interface system was designed for procedural planning and real-time intraoperative manipulation of the robot. The robotic device was constructed of plastic materials, pneumatic actuators, and fiber-optical encoders. The mechanical profile and MR compatibility of the robotic system were evaluated. The system-level error based on a phantom model was 1.14 ± 0.33 mm. A self-expanding prosthesis was successfully deployed in eight Yorkshire swine under rtMRI guidance. Post-deployment imaging and necropsy confirmed placement of the stent within 3 mm of the aortic valve annulus. These phantom and in vivo studies demonstrate the feasibility and advantages of robotic-assisted TAVR under rtMRI guidance. This robotic system increases the precision of valve deployments, diminishes environmental constraints, and improves the overall success of TAVR.

Direct Percutaneous Left Ventricular Access and Port Closure

PubMed Central

Barbash, Israel M.; Saikus, Christina E.; Faranesh, Anthony Z.; Ratnayaka, Kanishka; Kocaturk, Ozgur; Chen, Marcus Y.; Bell, Jamie A.; Virmani, Renu; Schenke, William H.; Hansen, Michael S.; Slack, Michael C.; Lederman, Robert J.

2012-01-01

Objectives This study sought to evaluate feasibility of nonsurgical transthoracic catheter-based left ventricular (LV) access and closure. Background Implanting large devices, such as mitral or aortic valve prostheses, into the heart requires surgical exposure and repair. Reliable percutaneous direct transthoracic LV access and closure would allow new nonsurgical therapeutic procedures. Methods Percutaneous direct LV access was performed in 19 swine using real-time magnetic resonance imaging (MRI) and an “active” MRI needle antenna to deliver an 18-F introducer sheath. The LV access ports were closed percutaneously using a commercial ventricular septal defect occluder and an “active” MRI delivery cable for enhanced visibility. We used “permissive pericardial tamponade” (temporary fluid instillation to separate the 2 pericardial layers) to avoid pericardial entrapment by the epicardial disk. Techniques were developed in 8 animals, and 11 more were followed up to 3 months by MRI and histopathology. Results Imaging guidance allowed 18-F sheath access and closure with appropriate positioning of the occluder inside the transmyocardial tunnel. Of the survival cohort, immediate hemostasis was achieved in 8 of 11 patients. Failure modes included pericardial entrapment by the epicardial occluder disk (n = 2) and a true-apex entry site that prevented hemostatic apposition of the endocardial disk (n = 1). Reactive pericardial effusion (192 ± 118 ml) accumulated 5 ± 1 days after the procedure, requiring 1-time drainage. At 3 months, LV function was preserved, and the device was endothelialized. Conclusions Direct percutaneous LV access and closure is feasible using real-time MRI. A commercial occluder achieved hemostasis without evident deleterious effects on the LV. Having established the concept, further clinical development of this approach appears realistic. PMID:22192372

Design and evaluation of an innovative MRI-compatible Braille stimulator with high spatial and temporal resolution.

PubMed

Debowska, Weronika; Wolak, Tomasz; Soluch, Pawel; Orzechowski, Mateusz; Kossut, Malgorzata

2013-02-15

Neural correlates of Braille reading have been widely studied with different neuroimaging techniques. Nevertheless, the exact brain processes underlying this unique activity are still unknown, due to suboptimal accuracy of imaging and/or stimuli delivery methods. To study somatosensory perception effectively, the stimulation must reflect parameters of the natural stimulus and must be applied with precise timing. In functional magnetic resonance imaging (fMRI) providing these characteristics requires technologically advanced solutions and there have been several successful direct tactile stimulation devices designed that allow investigation of somatotopic organization of brain sensory areas. They may, however, be of limited applicability in studying brain mechanisms related to such distinctive tactile activity as Braille reading. In this paper we describe the design and experimental evaluation of an innovative MRI-compatible Braille Character Stimulator (BCS) enabling precise and stable delivery of standardized Braille characters with high temporal resolution. Our device is fully programmable, flexible in stimuli delivery and can be easily implemented in any research unit. The Braille Character Stimulator was tested with a same-different discrimination task on Braille characters during an event-related fMRI experiment in eleven right-handed sighted adult subjects. The results show significant activations in several cortical areas, including bilateral primary (SI) and secondary somatosensory (SII) cortices, bilateral premotor and supplementary motor areas, inferior frontal gyri, inferior temporal gyri and precuneus, as well as contralateral (to the stimulated hand) thalamus. The results validate the use of the BCS as a method of effective stimuli application in fMRI studies, in both sighted and visually impaired subjects. Copyright © 2012 Elsevier B.V. All rights reserved.

Development of an MR-compatible hand exoskeleton that is capable of providing interactive robotic rehabilitation during fMRI imaging.

PubMed

Kim, Sangjoon J; Kim, Yeongjin; Lee, Hyosang; Ghasemlou, Pouya; Kim, Jung

2018-02-01

Following advances in robotic rehabilitation, there have been many efforts to investigate the recovery process and effectiveness of robotic rehabilitation procedures through monitoring the activation status of the brain. This work presents the development of a two degree-of-freedom (DoF) magnetic resonance (MR)-compatible hand device that can perform robotic rehabilitation procedures inside an fMRI scanner. The device is capable of providing real-time monitoring of the joint angle, angular velocity, and joint force produced by the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of four fingers. For force measurement, a custom reflective optical force sensor was developed and characterized in terms of accuracy error, hysteresis, and repeatability in the MR environment. The proposed device consists of two non-magnetic ultrasonic motors to provide assistive and resistive forces to the MCP and PIP joints. With actuation and sensing capabilities, both non-voluntary-passive movements and active-voluntary movements can be implemented. The MR compatibility of the device was verified via the analysis of the signal-to-noise ratio (SNR) of MR images of phantoms. SNR drops of 0.25, 2.94, and 11.82% were observed when the device was present but not activated, when only the custom force sensor was activated, and when both the custom force sensor and actuators were activated, respectively.

Low-Cost High-Performance MRI

NASA Astrophysics Data System (ADS)

Sarracanie, Mathieu; Lapierre, Cristen D.; Salameh, Najat; Waddington, David E. J.; Witzel, Thomas; Rosen, Matthew S.

2015-10-01

Magnetic Resonance Imaging (MRI) is unparalleled in its ability to visualize anatomical structure and function non-invasively with high spatial and temporal resolution. Yet to overcome the low sensitivity inherent in inductive detection of weakly polarized nuclear spins, the vast majority of clinical MRI scanners employ superconducting magnets producing very high magnetic fields. Commonly found at 1.5-3 tesla (T), these powerful magnets are massive and have very strict infrastructure demands that preclude operation in many environments. MRI scanners are costly to purchase, site, and maintain, with the purchase price approaching $1 M per tesla (T) of magnetic field. We present here a remarkably simple, non-cryogenic approach to high-performance human MRI at ultra-low magnetic field, whereby modern under-sampling strategies are combined with fully-refocused dynamic spin control using steady-state free precession techniques. At 6.5 mT (more than 450 times lower than clinical MRI scanners) we demonstrate (2.5 × 3.5 × 8.5) mm3 imaging resolution in the living human brain using a simple, open-geometry electromagnet, with 3D image acquisition over the entire brain in 6 minutes. We contend that these practical ultra-low magnetic field implementations of MRI (<10 mT) will complement traditional MRI, providing clinically relevant images and setting new standards for affordable (<$50,000) and robust portable devices.

"Low-field" intraoperative MRI: a new scenario, a new adaptation.

PubMed

Iturri-Clavero, F; Galbarriatu-Gutierrez, L; Gonzalez-Uriarte, A; Tamayo-Medel, G; de Orte, K; Martinez-Ruiz, A; Castellon-Larios, K; Bergese, S D

2016-11-01

To describe the adaptation of Cruces University Hospital to the use of intraoperative magnetic resonance imaging (ioMRI), and how the acquisition and use of this technology would impact the day-to-day running of the neurosurgical suite. With the approval of the ethics committee, an observational, prospective study was performed from June 2012 to April 2014, which included 109 neurosurgical procedures with the assistance of ioMRI. These were performed using the Polestar N-30 system (PSN30; Medtronic Navigation, Louisville, CO), which was integrated into the operating room. A total of 159 procedures were included: 109 cranial surgeries assisted with ioMRI and 50 control cases (no ioMRI use). There were no statistical significant differences when anaesthetic time (p=0.587) and surgical time (p=0.792) were compared; however, an important difference was shown in duration of patient positioning (p<0.0009) and total duration of the procedure (p<0.0009) between both groups. The introduction of ioMRI is necessary for most neurosurgical suites; however, a few things need to be taken into consideration when adapting to it. Increase procedure time, the use of specific MRI-safe devices, as well as a checklist for each patient to minimise risks, should be taken into consideration. Published by Elsevier Ltd.

Wireless Medical Devices for MRI-Guided Interventions

NASA Astrophysics Data System (ADS)

Venkateswaran, Madhav

Wireless techniques can play an important role in next-generation, image-guided surgical techniques with integration strategies being the key. We present our investigations on three wireless applications. First, we validate a position and orientation independent method to noninvasively monitor wireless power delivery using current perturbation measurements of switched load modulation of the RF carrier. This is important for safe and efficient powering without using bulky batteries or invasive cables. Use of MRI transmit RF pulses for simultaneous powering is investigated in the second part. We develop system models for the MRI transmit chain, wireless powering circuits and a typical load. Detailed analysis and validation of nonlinear and cascaded modeling strategies are performed, useful for decoupled optimization of the harvester coil and RF-DC converter. MRI pulse sequences are investigated for suitability for simultaneous powering. Simulations indicate that a 1.8V, 2 mA load can be powered with a 100% duty cycle using a 30° fGRE sequence, despite the RF duty cycle being 44 mW for a 30° flip angle, consistent with model predictions. Investigations on imaging artifacts indicates that distortion is mostly restricted to within the physical span of the harvester coil in the imaging volume, with the homogeneous B1+ transmit field providing positioning flexibility to minimize this for simultaneous powering. The models are potentially valuable in designing wireless powering solutions for implantable devices with simultaneous real-time imaging in MRI-guided surgical suites. Finally in the last section, we model endovascular MRI coil coupling during RF transmit. FEM models for a series-resonant multimode coil and quadrature birdcage coil fields are developed and computationally efficient, circuit and full-wave simulations are used to model inductive coupling. The Bloch Siegert B1 mapping sequence is used for validating at 24, 28 and 34 microT background excitation. Quantitative performance metrics are successfully predicted and the role of simulation in geometric optimization is demonstrated. In a pig study, we demonstrate navigation of a catheter, with tip-tracking and high-resolution intravascular imaging, through the vasculature into the heart, followed by contextual visualization. A potentially significant application is in MRI-guided cardiac ablation procedures.

Sub-pixel localisation of passive micro-coil fiducial markers in interventional MRI.

PubMed

Rea, Marc; McRobbie, Donald; Elhawary, Haytham; Tse, Zion T H; Lamperth, Michael; Young, Ian

2009-04-01

Electromechanical devices enable increased accuracy in surgical procedures, and the recent development of MRI-compatible mechatronics permits the use of MRI for real-time image guidance. Integrated imaging of resonant micro-coil fiducials provides an accurate method of tracking devices in a scanner with increased flexibility compared to gradient tracking. Here we report on the ability of ten different image-processing algorithms to track micro-coil fiducials with sub-pixel accuracy. Five algorithms: maximum pixel, barycentric weighting, linear interpolation, quadratic fitting and Gaussian fitting were applied both directly to the pixel intensity matrix and to the cross-correlation matrix obtained by 2D convolution with a reference image. Using images of a 3 mm fiducial marker and a pixel size of 1.1 mm, intensity linear interpolation, which calculates the position of the fiducial centre by interpolating the pixel data to find the fiducial edges, was found to give the best performance for minimal computing power; a maximum error of 0.22 mm was observed in fiducial localisation for displacements up to 40 mm. The inherent standard deviation of fiducial localisation was 0.04 mm. This work enables greater accuracy to be achieved in passive fiducial tracking.

Accurate and simple method for quantification of hepatic fat content using magnetic resonance imaging: a prospective study in biopsy-proven nonalcoholic fatty liver disease.

PubMed

Hatta, Tomoko; Fujinaga, Yasunari; Kadoya, Masumi; Ueda, Hitoshi; Murayama, Hiroaki; Kurozumi, Masahiro; Ueda, Kazuhiko; Komatsu, Michiharu; Nagaya, Tadanobu; Joshita, Satoru; Kodama, Ryo; Tanaka, Eiji; Uehara, Tsuyoshi; Sano, Kenji; Tanaka, Naoki

2010-12-01

To assess the degree of hepatic fat content, simple and noninvasive methods with high objectivity and reproducibility are required. Magnetic resonance imaging (MRI) is one such candidate, although its accuracy remains unclear. We aimed to validate an MRI method for quantifying hepatic fat content by calibrating MRI reading with a phantom and comparing MRI measurements in human subjects with estimates of liver fat content in liver biopsy specimens. The MRI method was performed by a combination of MRI calibration using a phantom and double-echo chemical shift gradient-echo sequence (double-echo fast low-angle shot sequence) that has been widely used on a 1.5-T scanner. Liver fat content in patients with nonalcoholic fatty liver disease (NAFLD, n = 26) was derived from a calibration curve generated by scanning the phantom. Liver fat was also estimated by optical image analysis. The correlation between the MRI measurements and liver histology findings was examined prospectively. Magnetic resonance imaging measurements showed a strong correlation with liver fat content estimated from the results of light microscopic examination (correlation coefficient 0.91, P < 0.001) regardless of the degree of hepatic steatosis. Moreover, the severity of lobular inflammation or fibrosis did not influence the MRI measurements. This MRI method is simple and noninvasive, has excellent ability to quantify hepatic fat content even in NAFLD patients with mild steatosis or advanced fibrosis, and can be performed easily without special devices.

A conditional Granger causality model approach for group analysis in functional MRI

PubMed Central

Zhou, Zhenyu; Wang, Xunheng; Klahr, Nelson J.; Liu, Wei; Arias, Diana; Liu, Hongzhi; von Deneen, Karen M.; Wen, Ying; Lu, Zuhong; Xu, Dongrong; Liu, Yijun

2011-01-01

Granger causality model (GCM) derived from multivariate vector autoregressive models of data has been employed for identifying effective connectivity in the human brain with functional MR imaging (fMRI) and to reveal complex temporal and spatial dynamics underlying a variety of cognitive processes. In the most recent fMRI effective connectivity measures, pairwise GCM has commonly been applied based on single voxel values or average values from special brain areas at the group level. Although a few novel conditional GCM methods have been proposed to quantify the connections between brain areas, our study is the first to propose a viable standardized approach for group analysis of an fMRI data with GCM. To compare the effectiveness of our approach with traditional pairwise GCM models, we applied a well-established conditional GCM to pre-selected time series of brain regions resulting from general linear model (GLM) and group spatial kernel independent component analysis (ICA) of an fMRI dataset in the temporal domain. Datasets consisting of one task-related and one resting-state fMRI were used to investigate connections among brain areas with the conditional GCM method. With the GLM detected brain activation regions in the emotion related cortex during the block design paradigm, the conditional GCM method was proposed to study the causality of the habituation between the left amygdala and pregenual cingulate cortex during emotion processing. For the resting-state dataset, it is possible to calculate not only the effective connectivity between networks but also the heterogeneity within a single network. Our results have further shown a particular interacting pattern of default mode network (DMN) that can be characterized as both afferent and efferent influences on the medial prefrontal cortex (mPFC) and posterior cingulate cortex (PCC). These results suggest that the conditional GCM approach based on a linear multivariate vector autoregressive (MVAR) model can achieve greater accuracy in detecting network connectivity than the widely used pairwise GCM, and this group analysis methodology can be quite useful to extend the information obtainable in fMRI. PMID:21232892

Axisymmetric magnetorotational instability in ideal and viscous laboratory plasmas

NASA Astrophysics Data System (ADS)

Mikhailovskii, A. B.; Lominadze, J. G.; Churikov, A. P.; Erokhin, N. N.; Pustovitov, V. D.; Konovalov, S. V.

2008-10-01

The original analysis of the axisymmetric magnetorotational instability (MRI) by Velikhov (Sov. Phys. JETP 9, 995 (1959)) and Chandrasekhar (Proc. Nat. Acad. Sci. 46, 253 (1960)), applied to the ideally conducting magnetized medium in the laboratory conditions and restricted to the incompressible approximation, is extended by allowing for the compressibility. Thereby, two additional driving mechanisms of MRI are revealed in addition to the standard drive due to the negative medium rotation frequency gradient (the Velikhov effect). One is due to the squared medium pressure gradient and another is a combined effect of the pressure and density gradients. For laboratory applications, the expression for the MRI boundary with all the above driving mechanisms and the stabilizing magnetoacoustic effect is derived. The effects of parallel and perpendicular viscosities on the MRI in the laboratory plasma are investigated. It is shown that, for strong viscosity, there is a family of MRI driven for the same condition as the ideal one. It is also revealed that the presence of strong viscosity leads to additional family of instabilities called the viscosity-driven MRI. Then the parallel-viscositydriven MRI looks as an overstability (oscillatory instability) possessing both the growth rate and the real part of oscillation frequency, while the perpendicular-viscosity MRI is the aperiodical instability.

Attention and Semantic Processing during Speech: An fMRI Study

ERIC Educational Resources Information Center

Rama, Pia; Relander-Syrjanen, Kristiina; Carlson, Synnove; Salonen, Oili; Kujala, Teija

2012-01-01

This fMRI study was conducted to investigate whether language semantics is processed even when attention is not explicitly directed to word meanings. In the "unattended" condition, the subjects performed a visual detection task while hearing semantically related and unrelated word pairs. In the "phoneme" condition, the subjects made phoneme…

Interpersonal touch suppresses visual processing of aversive stimuli

PubMed Central

Kawamichi, Hiroaki; Kitada, Ryo; Yoshihara, Kazufumi; Takahashi, Haruka K.; Sadato, Norihiro

2015-01-01

Social contact is essential for survival in human society. A previous study demonstrated that interpersonal contact alleviates pain-related distress by suppressing the activity of its underlying neural network. One explanation for this is that attention is shifted from the cause of distress to interpersonal contact. To test this hypothesis, we conducted a functional MRI (fMRI) study wherein eight pairs of close female friends rated the aversiveness of aversive and non-aversive visual stimuli under two conditions: joining hands either with a rubber model (rubber-hand condition) or with a close friend (human-hand condition). Subsequently, participants rated the overall comfortableness of each condition. The rating result after fMRI indicated that participants experienced greater comfortableness during the human-hand compared to the rubber-hand condition, whereas aversiveness ratings during fMRI were comparable across conditions. The fMRI results showed that the two conditions commonly produced aversive-related activation in both sides of the visual cortex (including V1, V2, and V5). An interaction between aversiveness and hand type showed rubber-hand-specific activation for (aversive > non-aversive) in other visual areas (including V1, V2, V3, and V4v). The effect of interpersonal contact on the processing of aversive stimuli was negatively correlated with the increment of attentional focus to aversiveness measured by a pain-catastrophizing scale. These results suggest that interpersonal touch suppresses the processing of aversive visual stimuli in the occipital cortex. This effect covaried with aversiveness-insensitivity, such that aversive-insensitive individuals might require a lesser degree of attentional capture to aversive-stimulus processing. As joining hands did not influence the subjective ratings of aversiveness, interpersonal touch may operate by redirecting excessive attention away from aversive characteristics of the stimuli. PMID:25904856

Magnetic resonance-compatible robotic and mechatronics systems for image-guided interventions and rehabilitation: a review study.

PubMed

Tsekos, Nikolaos V; Khanicheh, Azadeh; Christoforou, Eftychios; Mavroidis, Constantinos

2007-01-01

The continuous technological progress of magnetic resonance imaging (MRI), as well as its widespread clinical use as a highly sensitive tool in diagnostics and advanced brain research, has brought a high demand for the development of magnetic resonance (MR)-compatible robotic/mechatronic systems. Revolutionary robots guided by real-time three-dimensional (3-D)-MRI allow reliable and precise minimally invasive interventions with relatively short recovery times. Dedicated robotic interfaces used in conjunction with fMRI allow neuroscientists to investigate the brain mechanisms of manipulation and motor learning, as well as to improve rehabilitation therapies. This paper gives an overview of the motivation, advantages, technical challenges, and existing prototypes for MR-compatible robotic/mechatronic devices.

MRI compatible optrodes for simultaneous LFP and optogenetic fMRI investigation of seizure-like afterdischarges

PubMed Central

Duffy, Ben A; Choy, ManKin; Chuapoco, Miguel R; Madsen, Michael; Lee, Jin Hyung

2017-01-01

In preclinical studies, implanted electrodes can cause severe degradation of MRI images and hence are seldom used for chronic studies employing functional magnetic resonance imaging. In this study, we developed carbon fiber optrodes (optical fiber and electrode hybrid devices), which can be utilised in chronic longitudinal studies aiming to take advantage of emerging optogenetic technologies, and compared them with the more widely used tungsten optrodes. We find that optrodes constructed using small diameter (~130 μm) carbon fiber electrodes cause significantly reduced artifact on functional MRI images compared those made with 50 μm diameter tungsten wire and at the same time the carbon electrodes have lower impedance, which leads to higher quality intracranial LFP recordings. In order to validate this approach, we use these devices to study optogenetically-induced seizure-like afterdischarges in rats sedated with dexmedetomidine and compare these to sub (seizure) threshold stimulations in the same animals. The results indicate that seizure-like afterdischarges involve several extrahippocampal brain regions that are not recruited by subthreshold optogenetic stimulation of the hippocampus at 20 Hz. Subthreshold stimulation led to activation of the entire ipsilateral hippocampus, whereas afterdischarges additionally produced activations in the contralateral hippocampal formation, septum, neocortex, cerebellum, nucleus accumbens, and thalamus. Although we demonstrate just one application, given the ease of fabrication, we anticipate that carbon fiber optrodes could be utilised in a variety of studies that could benefit from longitudinal optogenetic functional magnetic resonance imaging. PMID:26208873

In Vitro Magnetic Resonance Imaging Evaluation of Fragmented, Open-Coil, Percutaneous Peripheral Nerve Stimulation Leads.

PubMed

Shellock, Frank G; Zare, Armaan; Ilfeld, Brian M; Chae, John; Strother, Robert B

2018-04-01

Percutaneous peripheral nerve stimulation (PNS) is an FDA-cleared pain treatment. Occasionally, fragments of the lead (MicroLead, SPR Therapeutics, LLC, Cleveland, OH, USA) may be retained following lead removal. Since the lead is metallic, there are associated magnetic resonance imaging (MRI) risks. Therefore, the objective of this investigation was to evaluate MRI-related issues (i.e., magnetic field interactions, heating, and artifacts) for various lead fragments. Testing was conducted using standardized techniques on lead fragments of different lengths (i.e., 50, 75, and 100% of maximum possible fragment length of 12.7 cm) to determine MRI-related problems. Magnetic field interactions (i.e., translational attraction and torque) and artifacts were tested for the longest lead fragment at 3 Tesla. MRI-related heating was evaluated at 1.5 Tesla/64 MHz and 3 Tesla/128 MHz with each lead fragment placed in a gelled-saline filled phantom. Temperatures were recorded on the lead fragments while using relatively high RF power levels. Artifacts were evaluated using T1-weighted, spin echo, and gradient echo (GRE) pulse sequences. The longest lead fragment produced only minor magnetic field interactions. For the lead fragments evaluated, physiologically inconsequential MRI-related heating occurred at 1.5 Tesla/64 MHz while under certain 3 Tesla/128 MHz conditions, excessive temperature elevations may occur. Artifacts extended approximately 7 mm from the lead fragment on the GRE pulse sequence, suggesting that anatomy located at a position greater than this distance may be visualized on MRI. MRI may be performed safely in patients with retained lead fragments at 1.5 Tesla using the specific conditions of this study (i.e., MR Conditional). Due to possible excessive temperature rises at 3 Tesla, performing MRI at that field strength is currently inadvisable. © 2017 International Neuromodulation Society.

Unimodal Versus Bimodal EEG-fMRI Neurofeedback of a Motor Imagery Task.

PubMed

Perronnet, Lorraine; Lécuyer, Anatole; Mano, Marsel; Bannier, Elise; Lotte, Fabien; Clerc, Maureen; Barillot, Christian

2017-01-01

Neurofeedback is a promising tool for brain rehabilitation and peak performance training. Neurofeedback approaches usually rely on a single brain imaging modality such as EEG or fMRI. Combining these modalities for neurofeedback training could allow to provide richer information to the subject and could thus enable him/her to achieve faster and more specific self-regulation. Yet unimodal and multimodal neurofeedback have never been compared before. In the present work, we introduce a simultaneous EEG-fMRI experimental protocol in which participants performed a motor-imagery task in unimodal and bimodal NF conditions. With this protocol we were able to compare for the first time the effects of unimodal EEG-neurofeedback and fMRI-neurofeedback versus bimodal EEG-fMRI-neurofeedback by looking both at EEG and fMRI activations. We also propose a new feedback metaphor for bimodal EEG-fMRI-neurofeedback that integrates both EEG and fMRI signal in a single bi-dimensional feedback (a ball moving in 2D). Such a feedback is intended to relieve the cognitive load of the subject by presenting the bimodal neurofeedback task as a single regulation task instead of two. Additionally, this integrated feedback metaphor gives flexibility on defining a bimodal neurofeedback target. Participants were able to regulate activity in their motor regions in all NF conditions. Moreover, motor activations as revealed by offline fMRI analysis were stronger during EEG-fMRI-neurofeedback than during EEG-neurofeedback. This result suggests that EEG-fMRI-neurofeedback could be more specific or more engaging than EEG-neurofeedback. Our results also suggest that during EEG-fMRI-neurofeedback, participants tended to regulate more the modality that was harder to control. Taken together our results shed first light on the specific mechanisms of bimodal EEG-fMRI-neurofeedback and on its added-value as compared to unimodal EEG-neurofeedback and fMRI-neurofeedback.

Unimodal Versus Bimodal EEG-fMRI Neurofeedback of a Motor Imagery Task

PubMed Central

Perronnet, Lorraine; Lécuyer, Anatole; Mano, Marsel; Bannier, Elise; Lotte, Fabien; Clerc, Maureen; Barillot, Christian

2017-01-01

Neurofeedback is a promising tool for brain rehabilitation and peak performance training. Neurofeedback approaches usually rely on a single brain imaging modality such as EEG or fMRI. Combining these modalities for neurofeedback training could allow to provide richer information to the subject and could thus enable him/her to achieve faster and more specific self-regulation. Yet unimodal and multimodal neurofeedback have never been compared before. In the present work, we introduce a simultaneous EEG-fMRI experimental protocol in which participants performed a motor-imagery task in unimodal and bimodal NF conditions. With this protocol we were able to compare for the first time the effects of unimodal EEG-neurofeedback and fMRI-neurofeedback versus bimodal EEG-fMRI-neurofeedback by looking both at EEG and fMRI activations. We also propose a new feedback metaphor for bimodal EEG-fMRI-neurofeedback that integrates both EEG and fMRI signal in a single bi-dimensional feedback (a ball moving in 2D). Such a feedback is intended to relieve the cognitive load of the subject by presenting the bimodal neurofeedback task as a single regulation task instead of two. Additionally, this integrated feedback metaphor gives flexibility on defining a bimodal neurofeedback target. Participants were able to regulate activity in their motor regions in all NF conditions. Moreover, motor activations as revealed by offline fMRI analysis were stronger during EEG-fMRI-neurofeedback than during EEG-neurofeedback. This result suggests that EEG-fMRI-neurofeedback could be more specific or more engaging than EEG-neurofeedback. Our results also suggest that during EEG-fMRI-neurofeedback, participants tended to regulate more the modality that was harder to control. Taken together our results shed first light on the specific mechanisms of bimodal EEG-fMRI-neurofeedback and on its added-value as compared to unimodal EEG-neurofeedback and fMRI-neurofeedback. PMID:28473762

Focused tight dressing does not prevent cochlear implant magnet migration under 1.5 Tesla MRI.

PubMed

Cuda, D; Murri, A; Succo, G

2013-04-01

We report a retrospective case of inner magnet migration, which occurred after 1.5 Tesla MRI scanning in an adult recipient of a bilateral cochlear implant (CI) despite a focused head dressing. The patient, bilaterally implanted with Nucleus 5 CIs (Cochlear LTD, Sydney, Australia), underwent a 1.5 Tesla cholangio-MRI scan for biliary duct pathology. In subsequent days, a focal skin alteration appeared over the left inner coil. Plain skull radiographs showed partial magnet migration on the left side. Surgical exploration confirmed magnet twisting; the magnet was effectively repositioned. Left CI performance was restored to pre-migration level. The wound healed without complications. Thus, focused dressing does not prevent magnet migration in CI recipients undergoing 1.5 Tesla MRI. All patients should be counselled on this potential complication. A minor surgical procedure is required to reposition the magnet. Nevertheless, timely diagnosis is necessary to prevent skin breakdown and subsequent device contamination. Plain skull radiograph is very effective in identifying magnet twisting; it should be performed systematically after MRI or minimally on all suspected cases.

Evolution of the magnetorotational instability on initially tangled magnetic fields

NASA Astrophysics Data System (ADS)

Bhat, Pallavi; Ebrahimi, Fatima; Blackman, Eric G.; Subramanian, Kandaswamy

2017-12-01

The initial magnetic field of previous magnetorotational instability (MRI) simulations has always included a significant system-scale component, even if stochastic. However, it is of conceptual and practical interest to assess whether the MRI can grow when the initial field is turbulent. The ubiquitous presence of turbulent or random flows in astrophysical plasmas generically leads to a small-scale dynamo (SSD), which would provide initial seed turbulent velocity and magnetic fields in the plasma that becomes an accretion disc. Can the MRI grow from these more realistic initial conditions? To address this, we supply a standard shearing box with isotropically forced SSD generated magnetic and velocity fields as initial conditions and remove the forcing. We find that if the initially supplied fields are too weak or too incoherent, they decay from the initial turbulent cascade faster than they can grow via the MRI. When the initially supplied fields are sufficient to allow MRI growth and sustenance, the saturated stresses, large-scale fields and power spectra match those of the standard zero net flux MRI simulation with an initial large-scale vertical field.

Cognition, emotion and reward networks associated with sex differences for romantic appraisals.

PubMed

Yin, Jie; Zou, Zhiling; Song, Hongwen; Zhang, Zhuo; Yang, Bo; Huang, Xiting

2018-02-12

Romantic love is a cross-culturally universal phenomenon that serves as a commitment device for motivating pair bonding in human beings. Women and men may experience different feelings when viewing the same warm, romantic scenes. To determine which brain systems may be involved in romance perception and examine possible sex differences, we scanned 16 women and 16 men who were intensely in love, using functional MRI. Participants were required to rate the romance level of 60 pictures showing romantic events that may frequently occur during romantic relationship formation. The results showed that greater brain activation was found for men in the insula, PCC (posterior cingulate cortex), and prefrontal gyrus compared with women, primarily under the High-romance condition. In addition, enhanced functional connectivity between the brain regions involved in the High-romance condition in contrast to the Low-romance condition was only found for men. These data suggest that men and women differ in the processing of romantic information and that it may be  more effortful for men to perceive and evaluate romance degree.

Temperature Control at DBS Electrodes using Heat Sink: Experimentally Validated FEM Model of DBS lead Architecture

PubMed Central

Elwassif, Maged M.; Datta, Abhishek; Rahman, Asif; Bikson, Marom

2012-01-01

There is a growing interest in the use of Deep Brain Stimulation for the treatment of medically refractory movement disorders and other neurological and psychiatric conditions. The extent of temperature increases around DBS electrodes during normal operation (joule heating and increased metabolic activity) or coupling with an external source (e.g. MRI) remains poorly understood and methods to mitigate temperature increases are being actively investigated. We developed a heat transfer finite element method simulation of DBS incorporating the realistic architecture of Medtronic 3389 leads. The temperature changes were analyzed considering different electrode configurations, stimulation protocols, and tissue properties. The heat-transfer model results were then validated using micro-thermocouple measurements during DBS lead stimulation in a saline bath. FEM results indicate that lead design (materials and geometry) may have a central role in controlling temperature rise by conducting heat. We show how modifying lead design can effectively control temperature increases. The robustness of this heat-sink approach over complimentary heat-mitigation technologies follows from several features: 1) it is insensitive to the mechanisms of heating (e.g. nature of magnetic coupling); 2) does not interfere with device efficacy; and 3) can be practically implemented in a broad range of implanted devices without modifying the normal device operations or the implant procedure. PMID:22764359

The Weakly Nonlinear Magnetorotational Instability in a Global, Cylindrical Taylor–Couette Flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, S. E.; Oishi, Jeffrey S., E-mail: seclark@astro.columbia.edu

We conduct a global, weakly nonlinear analysis of the magnetorotational instability (MRI) in a Taylor–Couette flow. This is a multiscale, perturbative treatment of the nonideal, axisymmetric MRI near threshold, subject to realistic radial boundary conditions and cylindrical geometry. We analyze both the standard MRI, initialized by a constant vertical background magnetic field, and the helical MRI, with an azimuthal background field component. This is the first weakly nonlinear analysis of the MRI in a global Taylor–Couette geometry, as well as the first weakly nonlinear analysis of the helical MRI. We find that the evolution of the amplitude of the standardmore » MRI is described by a real Ginzburg–Landau equation (GLE), whereas the amplitude of the helical MRI takes the form of a complex GLE. This suggests that the saturated state of the helical MRI may itself be unstable on long spatial and temporal scales.« less

Clinical Nononcologic Applications of PET/CT and PET/MRI in Musculoskeletal, Orthopedic, and Rheumatologic Imaging.

PubMed

Gholamrezanezhad, Ali; Basques, Kyle; Batouli, Ali; Matcuk, George; Alavi, Abass; Jadvar, Hossein

2018-06-01

With improvements in PET/CT and PET/MRI over the last decade, as well as increased understanding of the pathophysiology of musculoskeletal diseases, there is an emerging potential for PET as a primary or complementary modality in the management of rheumatologic and orthopedic conditions. We discuss the role of PET/CT and PET/MRI in nononcologic musculoskeletal disorders, including inflammatory and infectious conditions and postoperative complications. There is great potential for an increased role for PET to serve as a primary or complementary modality in the management of orthopedic and rheumatologic disorders.

Inventory of MRI applications and workers exposed to MRI-related electromagnetic fields in the Netherlands.

PubMed

Schaap, Kristel; Christopher-De Vries, Yvette; Slottje, Pauline; Kromhout, Hans

2013-12-01

This study aims to characterise and quantify the population that is occupationally exposed to electromagnetic fields (EMF) from magnetic resonance imaging (MRI) devices and to identify factors that determine the probability and type of exposure. A questionnaire survey was used to collect information about scanners, procedures, historical developments and employees working with or near MRI scanners in clinical and research MRI departments in the Netherlands. Data were obtained from 145 MRI departments. A rapid increase in the use of MRI and field strength of the scanners was observed and quantified. The strongest magnets were employed by academic hospitals and research departments. Approximately 7000 individuals were reported to be working inside an MRI scanner room and were thus considered to have high probability of occupational exposure to static magnetic fields (SMF). Fifty-four per cent was exposed to SMF at least one day per month. The largest occupationally exposed group were radiographers (n ~ 1700). Nine per cent of the 7000 involved workers were regularly present inside a scanner room during image acquisition, when exposure to additional types of EMF is considered a possibility. This practice was most prevalent among workers involved in scanning animals. The data illustrate recent trends and historical developments in magnetic resonance imaging and provide an extensive characterisation of the occupationally exposed population. A considerable number of workers are potentially exposed to MRI-related EMF. Type and frequency of potential exposure depend on the job performed, as well as the type of workplace. Copyright © 2013 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

Evaluation of an internet-based animated preparatory video for children undergoing non-sedated MRI.

PubMed

McGlashan, Hannah L; Dineen, Rob A; Szeszak, Sofia; Whitehouse, William P; Chow, Gabriel; Love, Andrew; Langmack, Gill; Wharrad, Heather

2018-05-10

We evaluate the value of an internet-based educational animated video designed to prepare children for MRI scans, and whether this video reduces scan-related anxiety in children with a neurological disorder, and healthy controls. Participants completed a pre- and post-scan questionnaire evaluating participant online viewing behaviour, understanding of the MRI procedure, anxiety regarding the MRI, impact of animation in preparing the child and whether the child's expectation of the MRI scan matched their experience. 21 children were recruited (12 healthy controls) ranging in age from 6.5 to 11.5 years. The animation was successfully accessed by participants on a range of digital devices and had high levels of approval. Children who viewed the animation had a good understanding of the MRI procedure and low anxiety levels prior to the scan, and reported that their expectations broadly matched the real-life MRI experience. Children reported that the animation positively impacted on their preparation with similar ratings before and after the scan, and the impact on preparation was rated greater by younger children. There were no group differences between healthy children and those with the neurological disorder for ratings of anxiety, impact on preparation and expectation of the experience. This evaluation demonstrates accessibility, acceptability and relevance of internet-based educational animation for typically developing children, and children with a neurodisability aged 6 to 11 years, with positive impact on preparation for MRI. Advances in knowledge: The internet-based educational animation provides a widely accessible tool to support preparation of children for non-sedated MRI.

Preclinical Feasibility of a Technology Framework for MRI-guided Iliac Angioplasty

PubMed Central

Rube, Martin A.; Fernandez-Gutierrez, Fabiola; Cox, Benjamin F.; Holbrook, Andrew B.; Houston, J. Graeme; White, Richard D.; McLeod, Helen; Fatahi, Mahsa; Melzer, Andreas

2015-01-01

Purpose Interventional MRI has significant potential for image guidance of iliac angioplasty and related vascular procedures. A technology framework with in-room image display, control, communication and MRI-guided intervention techniques was designed and tested for its potential to provide safe, fast and efficient MRI-guided angioplasty of the iliac arteries. Methods A 1.5T MRI scanner was adapted for interactive imaging during endovascular procedures using new or modified interventional devices such as guidewires and catheters. A perfused vascular phantom was used for testing. Pre-, intra- and post-procedural visualization and measurement of vascular morphology and flow was implemented. A detailed analysis of X-Ray fluoroscopic angiography workflow was conducted and applied. Two interventional radiologists and one physician in training performed 39 procedures. All procedures were timed and analyzed. Results MRI-guided iliac angioplasty procedures were successfully performed with progressive adaptation of techniques and workflow. The workflow, setup and protocol enabled a reduction in table time for a dedicated MRI-guided procedure to 6 min 33 s with a mean procedure time of 9 min 2 s, comparable to the mean procedure time of 8 min 42 s for the standard X-Ray guided procedure. Conclusions MRI-guided iliac vascular interventions were found to be feasible and practical using this framework and optimized workflow. In particular the real-time flow analysis was found to be helpful for pre- and post-interventional assessments. Design optimization of the catheters and in vivo experiments are required before clinical evaluation. PMID:25102933

Knee MRI scan

MedlinePlus

... CT scan of the knee Knee x-ray Alternative Names MRI - knee; Magnetic resonance imaging - knee Patient ... any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should ...

An RF-induced voltage sensor for investigating pacemaker safety in MRI.

PubMed

Barbier, Thérèse; Piumatti, Roberto; Hecker, Bertrand; Odille, Freddy; Felblinger, Jacques; Pasquier, Cédric

2014-12-01

Magnetic resonance imaging (MRI) is inadvisable for patients with pacemakers, as radiofrequency (RF) voltages induced in the pacemaker leads may cause the device to malfunction. Our goal is to develop a sensor to measure such RF-induced voltages during MRI safety tests. A sensor was designed (16.6 cm(2)) for measuring voltages at the connection between the pacemaker lead and its case. The induced voltage is demodulated, digitized, and transferred by optical fibres. The sensor was calibrated on the bench using RF pulses of known amplitude and duration. Then the sensor was tested during MRI scanning at 1.5 T in a saline gel filled phantom. Bench tests showed measurement errors below 5% with a (-40 V; +40 V) range, a precision of 0.06 V, and a temporal resolution of 24.2 μs. In MRI tests, variability in the measured voltages was below 3.7% for 996 measurements with different sensors and RF exposure. Coupling between the sensor and the MRI electromagnetic environment was estimated with a second sensor connected and was below 6.2%. For a typical clinical MRI sequence, voltages around ten Vp were detected. We have built an accurate and reproducible tool for measuring RF-induced voltages in pacemaker leads during MR safety investigations. The sensor might also be used with other conducting cables including those used for electrocardiography and neurostimulation.

Reducing Field Distortion in Magnetic Resonance Imaging

NASA Technical Reports Server (NTRS)

Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob

2010-01-01

A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T

Combined PET/MR: The Real Work Has Just Started. Summary Report of the Third International Workshop on PET/MR Imaging; February 17-21, 2014, Tübingen, Germany.

PubMed

Bailey, D L; Antoch, G; Bartenstein, P; Barthel, H; Beer, A J; Bisdas, S; Bluemke, D A; Boellaard, R; Claussen, C D; Franzius, C; Hacker, M; Hricak, H; la Fougère, C; Gückel, B; Nekolla, S G; Pichler, B J; Purz, S; Quick, H H; Sabri, O; Sattler, B; Schäfer, J; Schmidt, H; van den Hoff, J; Voss, S; Weber, W; Wehrl, H F; Beyer, T

2015-06-01

This paper summarises the proceedings and discussions at the third annual workshop held in Tübingen, Germany, dedicated to the advancement of the technical, scientific and clinical applications of combined PET/MRI systems in humans. Two days of basic scientific and technical instructions with "hands-on" tutorials were followed by 3 days of invited presentations from active researchers in this and associated fields augmented by round-table discussions and dialogue boards with specific themes. These included the use of PET/MRI in paediatric oncology and in adult neurology, oncology and cardiology, the development of multi-parametric analyses, and efforts to standardise PET/MRI examinations to allow pooling of data for evaluating the technology. A poll taken on the final day demonstrated that over 50 % of those present felt that while PET/MRI technology underwent an inevitable slump after its much-anticipated initial launch, it was now entering a period of slow, progressive development, with new key applications emerging. In particular, researchers are focusing on exploiting the complementary nature of the physiological (PET) and biochemical (MRI/MRS) data within the morphological framework (MRI) that these devices can provide. Much of the discussion was summed up on the final day when one speaker commented on the state of PET/MRI: "the real work has just started".

Neural correlates of text-based emoticons: a preliminary fMRI study.

PubMed

Kim, Ko Woon; Lee, Sang Won; Choi, Jeewook; Kim, Tae Min; Jeong, Bumseok

2016-08-01

Like nonverbal cues in oral interactions, text-based emoticons, which are textual portrayals of a writer's facial expressions, are commonly used in electronic device-mediated communication. Little is known, however, about how text-based emoticons are processed in the human brain. With this study, we investigated whether the text-based emoticons are processed as face expressions using fMRI. During fMRI scan, subjects were asked to respond by pressing a button, indicating whether text-based emoticons represented positive or negative emotions. Voxel-wise analyses were performed to compare the responses and contrasted with emotional versus scrambled emoticons and among emoticons with different emotions. To explore processing strategies for text-based emoticons, brain activity in the bilateral occipital and fusiform face areas were compared. In the voxel-wise analysis, both emotional and scrambled emoticons were processed mainly in the bilateral fusiform gyri, inferior division of lateral occipital cortex, inferior frontal gyri, dorsolateral prefrontal cortex (DLPFC), dorsal anterior cingulate cortex (dACC), and parietal cortex. In a percent signal change analysis, the right occipital and fusiform face areas showed significantly higher activation than left ones. In comparisons among emoticons, sad one showed significant BOLD signal decrease in the dACC, the left AIC, the bilateral thalamus, and the precuneus as compared with other conditions. The results of this study imply that people recognize text-based emoticons as pictures representing face expressions. Even though text-based emoticons contain emotional meaning, they are not associated with the amygdala while previous studies using emotional stimuli documented amygdala activation.

MRI induced torque and demagnetization in retention magnets for a bone conduction implant.

PubMed

Jansson, Karl-Johan Fredén; Håkansson, Bo; Reinfeldt, Sabine; Taghavi, Hamidreza; Eeg-Olofsson, Måns

2014-06-01

Performing magnetic resonance imaging (MRI) examinations in patients who use implantable medical devices involve safety risks both for the patient and the implant. Hearing implants often use two permanent magnets, one implanted and one external, for the retention of the external transmitter coil to the implanted receiver coil to achieve an optimal signal transmission. The implanted magnet is subjected to both demagnetization and torque, magnetically induced by the MRI scanner. In this paper, demagnetization and a comparison between measured and simulated induced torque is studied for the retention magnet used in a bone conduction implant (BCI) system. The torque was measured and simulated in a uniform static magnetic field of 1.5 T. The magnetic field was generated by a dipole electromagnet and permanent magnets with two different types of coercive fields were tested. Demagnetization and maximum torque for the high coercive field magnets was 7.7% ± 2.5% and 0.20 ± 0.01 Nm, respectively and 71.4% ± 19.1% and 0.18 ± 0.01 Nm for the low coercive field magnets, respectively. The simulated maximum torque was 0.34 Nm, deviating from the measured torque in terms of amplitude, mainly related to an insufficient magnet model. The BCI implant with high coercive field magnets is believed to be magnetic resonance (MR) conditional up to 1.5 T if a compression band is used around the skull to fix the implant. This is not approved and requires further investigations, and if removal of the implant is needed, the surgical operation is expected to be simple.

Radiotherapy treatment planning: benefits of CT-MR image registration and fusion in tumor volume delineation.

PubMed

Djan, Igor; Petrović, Borislava; Erak, Marko; Nikolić, Ivan; Lucić, Silvija

2013-08-01

Development of imaging techniques, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET), made great impact on radiotherapy treatment planning by improving the localization of target volumes. Improved localization allows better local control of tumor volumes, but also minimizes geographical misses. Mutual information is obtained by registration and fusion of images achieved manually or automatically. The aim of this study was to validate the CT-MRI image fusion method and compare delineation obtained by CT versus CT-MRI image fusion. The image fusion software (XIO CMS 4.50.0) was applied to delineate 16 patients. The patients were scanned on CT and MRI in the treatment position within an immobilization device before the initial treatment. The gross tumor volume (GTV) and clinical target volume (CTV) were delineated on CT alone and on CT+MRI images consecutively and image fusion was obtained. Image fusion showed that CTV delineated on a CT image study set is mainly inadequate for treatment planning, in comparison with CTV delineated on CT-MRI fused image study set. Fusion of different modalities enables the most accurate target volume delineation. This study shows that registration and image fusion allows precise target localization in terms of GTV and CTV and local disease control.

Daily Tracking of Glioblastoma Resection Cavity, Cerebral Edema, and Tumor Volume with MRI-Guided Radiation Therapy.

PubMed

Mehta, Shahil; Gajjar, Shefali R; Padgett, Kyle R; Asher, David; Stoyanova, Radka; Ford, John C; Mellon, Eric A

2018-03-19

Radiation therapy (RT) plays a critical role in the treatment of glioblastoma. Studies of brain imaging during RT for glioblastoma have demonstrated changes in the brain during RT. However, frequent or daily utilization of standalone magnetic resonance imaging (MRI) scans during RT have limited feasibility. The recent release of the tri-cobalt-60 MRI-guided RT (MR-IGRT) device (ViewRay MRIdian, Cleveland, OH) allows for daily brain MRI for the RT setup. Daily MRI of three postoperative patients undergoing RT and temozolomide for glioblastoma over a six-week course allowed for the identification of changes to the cavity, edema, and visible tumor on a daily basis. The volumes and dimensions of the resection cavities, edema, and T2-hyperintense tumor were measured. A general trend of daily decreases in cavity measurements was observed in all patients. For the one patient with edema, a trend of daily increases followed by a trend of daily decreases were observed. These results suggest that daily MRI could be used for onboard resimulation and adaptive RT for future fluctuations in the sizes of brain tumors, cavities, or cystic components. This could improve tumor targeting and reduce RT of healthy brain tissue.

Daily Tracking of Glioblastoma Resection Cavity, Cerebral Edema, and Tumor Volume with MRI-Guided Radiation Therapy

PubMed Central

Mehta, Shahil; Gajjar, Shefali R; Padgett, Kyle R; Asher, David; Stoyanova, Radka; Ford, John C

2018-01-01

Radiation therapy (RT) plays a critical role in the treatment of glioblastoma. Studies of brain imaging during RT for glioblastoma have demonstrated changes in the brain during RT. However, frequent or daily utilization of standalone magnetic resonance imaging (MRI) scans during RT have limited feasibility. The recent release of the tri-cobalt-60 MRI-guided RT (MR-IGRT) device (ViewRay MRIdian, Cleveland, OH) allows for daily brain MRI for the RT setup. Daily MRI of three postoperative patients undergoing RT and temozolomide for glioblastoma over a six-week course allowed for the identification of changes to the cavity, edema, and visible tumor on a daily basis. The volumes and dimensions of the resection cavities, edema, and T2-hyperintense tumor were measured. A general trend of daily decreases in cavity measurements was observed in all patients. For the one patient with edema, a trend of daily increases followed by a trend of daily decreases were observed. These results suggest that daily MRI could be used for onboard resimulation and adaptive RT for future fluctuations in the sizes of brain tumors, cavities, or cystic components. This could improve tumor targeting and reduce RT of healthy brain tissue. PMID:29796358

Preparation of an Au-Pt alloy free from artifacts in magnetic resonance imaging.

PubMed

Kodama, Tomonobu; Nakai, Ryusuke; Goto, Kenji; Shima, Kunihiro; Iwata, Hiroo

2017-12-01

When magnetic resonance imaging (MRI) is performed on patients carrying metallic implants, artifacts can disturb the images around the implants, often making it difficult to interpret them appropriately. However, metallic materials are and will be indispensable as raw materials for medical devices because of their electric conductivity, visibility under X-ray fluoroscopy, and other favorable features. What is now desired is to develop a metallic material which causes no artifacts during MRI. In the present study, we prepared a single-phase and homogeneous Au-Pt alloys (Au; diamagnetic metal, and Pt; paramagnetic metal) by the processing of thermal treatment. Volume magnetic susceptibility was measured with a SQUID Flux Meter and MRI artifact was evaluated using a 1.5-T scanner. After final thermal treatment, an entirely recrystallized homogeneous organization was noted. The Au-35Pt alloy was shown to have a volume magnetic susceptibility of -8.8ppm, causing almost free from artifacts during MRI. We thus prepared an Au-35Pt alloy which had a magnetic susceptibility very close to that of living tissue and caused much fewer artifacts during MRI. It is promising as a material for spinal cages, intracranial electrodes, cerebral aneurysm embolization coils, markers for MRI and so on. Copyright © 2017 Elsevier Inc. All rights reserved.

Magnetic resonance imaging evaluation of intervertebral test spacers: an experimental comparison of magnesium versus titanium and carbon fiber reinforced polymers as biomaterials.

PubMed

Ernstberger, T; Buchhorn, G; Heidrich, G

2010-03-01

Intervertebral spacers are made of different materials, which can affect the postfusion magnetic resonance imaging (MRI) scans. Susceptibility artifacts, especially for metallic implants, can decrease the image quality. This study aimed to determine whether magnesium as a lightweight and biocompatible metal is suitable as a biomaterial for spinal implants based on its MRI artifacting behavior. To compare artifacting behaviors, we implanted into one porcine cadaveric spine different test spacers made of magnesium, titanium, and CFRP. All test spacers were scanned using two T1-TSE MRI sequences. The artifact dimensions were traced on all scans and statistically analyzed. The total artifact volume and median artifact area of the titanium spacers were statistically significantly larger than magnesium spacers (P < 0.001), while magnesium and CFRP spacers produced almost identical artifacting behaviors (P > 0.05). Our results suggest that spinal implants made with magnesium alloys will behave more like CFRP devices in MRI scans.

Spatiotemporal Quantification of Local Drug Delivery Using MRI

PubMed Central

Giers, Morgan B.; McLaren, Alex C.; Plasencia, Jonathan D.; McLemore, Ryan; Caplan, Michael R.

2013-01-01

Controlled release formulations for local, in vivo drug delivery are of growing interest to device manufacturers, research scientists, and clinicians; however, most research characterizing controlled release formulations occurs in vitro because the spatial and temporal distribution of drug delivery is difficult to measure in vivo. In this work, in vivo magnetic resonance imaging (MRI) of local drug delivery was performed to visualize and quantify the time resolved distribution of MRI contrast agents. Three-dimensional T 1 maps (generated from T 1-weighted images with varied T R) were processed using noise-reducing filtering. A segmented region of contrast, from a thresholded image, was converted to concentration maps using the equation 1/T 1 = 1/T 1,0 + R 1 C, where T 1,0 and T 1 are the precontrast and postcontrast T 1 map values, respectively. In this technique, a uniform estimated value for T 1,0 was used. Error estimations were performed for each step. The practical usefulness of this method was assessed using comparisons between devices located in different locations both with and without contrast. The method using a uniform T 1,0, requiring no registration of pre- and postcontrast image volumes, was compared to a method using either affine or deformation registrations. PMID:23710248

Development of a multi-scale and multi-modality imaging system to characterize tumours and their microenvironment in vivo

NASA Astrophysics Data System (ADS)

Rouffiac, Valérie; Ser-Leroux, Karine; Dugon, Emilie; Leguerney, Ingrid; Polrot, Mélanie; Robin, Sandra; Salomé-Desnoulez, Sophie; Ginefri, Jean-Christophe; Sebrié, Catherine; Laplace-Builhé, Corinne

2015-03-01

In vivo high-resolution imaging of tumor development is possible through dorsal skinfold chamber implantable on mice model. However, current intravital imaging systems are weakly tolerated along time by mice and do not allow multimodality imaging. Our project aims to develop a new chamber for: 1- long-term micro/macroscopic visualization of tumor (vascular and cellular compartments) and tissue microenvironment; and 2- multimodality imaging (photonic, MRI and sonography). Our new experimental device was patented in March 2014 and was primarily assessed on 75 mouse engrafted with 4T1-Luc tumor cell line, and validated in confocal and multiphoton imaging after staining the mice vasculature using Dextran 155KDa-TRITC or Dextran 2000kDa-FITC. Simultaneously, a universal stage was designed for optimal removal of respiratory and cardiac artifacts during microscopy assays. Experimental results from optical, ultrasound (Bmode and pulse subtraction mode) and MRI imaging (anatomic sequences) showed that our patented design, unlike commercial devices, improves longitudinal monitoring over several weeks (35 days on average against 12 for the commercial chamber) and allows for a better characterization of the early and late tissue alterations due to tumour development. We also demonstrated the compatibility for multimodality imaging and the increase of mice survival was by a factor of 2.9, with our new skinfold chamber. Current developments include: 1- defining new procedures for multi-labelling of cells and tissue (screening of fluorescent molecules and imaging protocols); 2- developing ultrasound and MRI imaging procedures with specific probes; 3- correlating optical/ultrasound/MRI data for a complete mapping of tumour development and microenvironment.

Design and development of novel MRI compatible zirconium- ruthenium alloys with ultralow magnetic susceptibility.

PubMed

Li, H F; Zhou, F Y; Li, L; Zheng, Y F

2016-04-19

In the present study, novel MRI compatible zirconium-ruthenium alloys with ultralow magnetic susceptibility were developed for biomedical and therapeutic devices under MRI diagnostics environments. The results demonstrated that alloying with ruthenium into pure zirconium would significantly increase the strength and hardness properties. The corrosion resistance of zirconium-ruthenium alloys increased significantly. High cell viability could be found and healthy cell morphology observed when culturing MG 63 osteoblast-like cells and L-929 fibroblast cells with zirconium-ruthenium alloys, whereas the hemolysis rates of zirconium-ruthenium alloys are <1%, much lower than 5%, the safe value for biomaterials according to ISO 10993-4 standard. Compared with conventional biomedical 316L stainless steel, Co-Cr alloys and Ti-based alloys, the magnetic susceptibilities of the zirconium-ruthenium alloys (1.25 × 10(-6) cm(3)·g(-1)-1.29 × 10(-6) cm(3)·g(-1) for zirconium-ruthenium alloys) are ultralow, about one-third that of Ti-based alloys (Ti-6Al-4V, ~3.5 × 10(-6) cm(3)·g(-1), CP Ti and Ti-6Al-7Nb, ~3.0 × 10(-6) cm(3)·g(-1)), and one-sixth that of Co-Cr alloys (Co-Cr-Mo, ~7.7 × 10(-6) cm(3)·g(-1)). Among the Zr-Ru alloy series, Zr-1Ru demonstrates enhanced mechanical properties, excellent corrosion resistance and cell viability with lowest magnetic susceptibility, and thus is the optimal Zr-Ru alloy system as therapeutic devices under MRI diagnostics environments.

Government health policy and the diffusion of new medical devices.

PubMed Central

Hillman, B J

1986-01-01

The combination of absent financial incentives, aspects of physicians' clinical training, and the uncertainty surrounding the appropriate application of expensive new medical devices have been the most significant factors in promoting their wasteful diffusion and use. This presentation summarizes the forces that have resulted in regulatory and reimbursement initiatives to make more efficient the acquisition and utilization of new medical devices. The case histories of computed tomography (CT) and magnetic resonance imaging (MRI) serve as a paradigm demonstrating why such initiatives have thus far proved ineffectual. More effective would be to abandon distinctions between inpatient and outpatient reimbursement for using new medical devices and to improve the relationship between reimbursement and technology assessment. PMID:3818311

Combined Ultrasound and MR Imaging to Guide Focused Ultrasound Therapies in the Brain

PubMed Central

Arvanitis, Costas D.; Livingstone, Margaret S.; McDannold, Nathan

2013-01-01

Purpose Several emerging therapies with potential for use in the brain harness effects produced by acoustic cavitation – the interaction between ultrasound and microbubbles either generated during sonication or introduced into the vasculature. Systems developed for transcranial MRI-guided focused ultrasound (MRgFUS) thermal ablation can enable their clinical translation, but methods for real-time monitoring and control are currently lacking. Acoustic emissions produced during sonication can provide information about the location, strength, and type of the microbubble oscillations within the ultrasound field, and they can be mapped in real-time using passive imaging approaches. Here, we tested whether such mapping can be achieved transcranially within a clinical brain MRgFUS system. Materials and Methods We integrated an ultrasound imaging array into the hemisphere transducer of the MRgFUS device. Passive cavitation maps were obtained during sonications combined with a circulating microbubble agent at 20 targets in the cingulate cortex in three macaques. The maps were compared with MRI-evident tissue effects. Results The system successfully mapped microbubble activity during both stable and inertial cavitation, which was correlated with MRI-evident transient blood-brain barrier disruption and vascular damage, respectively. The location of this activity was coincident with the resulting tissue changes within the expected resolution limits of the system. Conclusion While preliminary, these data clearly demonstrate, for the first time, that is possible to construct maps of stable and inertial cavitation transcranially, in a large animal model, and under clinically relevant conditions. Further, these results suggest that this hybrid ultrasound/MRI approach can provide comprehensive guidance for targeted drug delivery via blood-brain barrier disruption and other emerging ultrasound treatments, facilitating their clinical translation. We anticipate it will also prove to be an important research tool that will further the development of a broad range of microbubble-enhanced therapies. PMID:23788054

Neural correlates of the popular music phenomenon: evidence from functional MRI and PET imaging.

PubMed

Chen, Qiaozhen; Zhang, Ying; Hou, Haifeng; Du, Fenglei; Wu, Shuang; Chen, Lin; Shen, Yehua; Chao, Fangfang; Chung, June-Key; Zhang, Hong; Tian, Mei

2017-06-01

Music can induce different emotions. However, its neural mechanism remains unknown. The aim of this study was to use functional magnetic resonance imaging (fMRI) and position emission tomography (PET) imaging for mapping of neural changes under the most popular music in healthy volunteers. Blood-oxygen-level-dependent (BOLD) fMRI and monoamine receptor PET imaging with 11 C-N-methylspiperone ( 11 C-NMSP) were conducted under the popular music Gangnam Style and light music A Comme Amour in healthy subjects. PET and fMRI images were analyzed by using the Statistical Parametric Mapping software (SPM). Significantly increased fMRI BOLD signals were found in the bilateral superior temporal cortices, left cerebellum, left putamen and right thalamus cortex. Monoamine receptor availability was increased significantly in the left superior temporal gyrus and left putamen, but decreased in the bilateral superior occipital cortices under the Gangnam Style compared with the light music condition. Significant positive correlation was found between 11 C-NMSP binding and fMRI BOLD signals in the left temporal cortex. Furthermore, increased 11 C-NMSP binding in the left putamen was positively correlated with the mood arousal level score under the Gangnam Style condition. Popular music Gangnam Style can arouse pleasure experience and strong emotional response. The left putamen is positively correlated with the mood arousal level score under the Gangnam Style condition. Our results revealed characteristic patterns of brain activity associated with Gangnam Style, and may also provide more general insights into the music-induced emotional processing.

Lung parenchymal analysis on dynamic MRI in thoracic insufficiency syndrome to assess changes following surgical intervention

NASA Astrophysics Data System (ADS)

Jagadale, Basavaraj N.; Udupa, Jayaram K.; Tong, Yubing; Wu, Caiyun; McDonough, Joseph; Torigian, Drew A.; Campbell, Robert M.

2018-02-01

General surgeons, orthopedists, and pulmonologists individually treat patients with thoracic insufficiency syndrome (TIS). The benefits of growth-sparing procedures such as Vertical Expandable Prosthetic Titanium Rib (VEPTR)insertionfor treating patients with TIS have been demonstrated. However, at present there is no objective assessment metricto examine different thoracic structural components individually as to their roles in the syndrome, in contributing to dynamics and function, and in influencing treatment outcome. Using thoracic dynamic MRI (dMRI), we have been developing a methodology to overcome this problem. In this paper, we extend this methodology from our previous structural analysis approaches to examining lung tissue properties. We process the T2-weighted dMRI images through a series of steps involving 4D image construction of the acquired dMRI images, intensity non-uniformity correction and standardization of the 4D image, lung segmentation, and estimation of the parameters describing lung tissue intensity distributions in the 4D image. Based on pre- and post-operative dMRI data sets from 25 TIS patients (predominantly neuromuscular and congenital conditions), we demonstrate how lung tissue can be characterized by the estimated distribution parameters. Our results show that standardized T2-weighted image intensity values decrease from the pre- to post-operative condition, likely reflecting improved lung aeration post-operatively. In both pre- and post-operative conditions, the intensity values decrease also from end-expiration to end-inspiration, supporting the basic premise of our results.

Resting-State Functional Connectivity-Based Biomarkers and Functional MRI-Based Neurofeedback for Psychiatric Disorders: A Challenge for Developing Theranostic Biomarkers.

PubMed

Yamada, Takashi; Hashimoto, Ryu-Ichiro; Yahata, Noriaki; Ichikawa, Naho; Yoshihara, Yujiro; Okamoto, Yasumasa; Kato, Nobumasa; Takahashi, Hidehiko; Kawato, Mitsuo

2017-10-01

Psychiatric research has been hampered by an explanatory gap between psychiatric symptoms and their neural underpinnings, which has resulted in poor treatment outcomes. This situation has prompted us to shift from symptom-based diagnosis to data-driven diagnosis, aiming to redefine psychiatric disorders as disorders of neural circuitry. Promising candidates for data-driven diagnosis include resting-state functional connectivity MRI (rs-fcMRI)-based biomarkers. Although biomarkers have been developed with the aim of diagnosing patients and predicting the efficacy of therapy, the focus has shifted to the identification of biomarkers that represent therapeutic targets, which would allow for more personalized treatment approaches. This type of biomarker (i.e., "theranostic biomarker") is expected to elucidate the disease mechanism of psychiatric conditions and to offer an individualized neural circuit-based therapeutic target based on the neural cause of a condition. To this end, researchers have developed rs-fcMRI-based biomarkers and investigated a causal relationship between potential biomarkers and disease-specific behavior using functional MRI (fMRI)-based neurofeedback on functional connectivity. In this review, we introduce a recent approach for creating a theranostic biomarker, which consists mainly of 2 parts: (1) developing an rs-fcMRI-based biomarker that can predict diagnosis and/or symptoms with high accuracy, and (2) the introduction of a proof-of-concept study investigating the relationship between normalizing the biomarker and symptom changes using fMRI-based neurofeedback. In parallel with the introduction of recent studies, we review rs-fcMRI-based biomarker and fMRI-based neurofeedback, focusing on the technological improvements and limitations associated with clinical use. © The Author 2017. Published by Oxford University Press on behalf of CINP.

Resting-State Functional Connectivity-Based Biomarkers and Functional MRI-Based Neurofeedback for Psychiatric Disorders: A Challenge for Developing Theranostic Biomarkers

PubMed Central

Yamada, Takashi; Hashimoto, Ryu-ichiro; Yahata, Noriaki; Ichikawa, Naho; Yoshihara, Yujiro; Okamoto, Yasumasa; Kato, Nobumasa; Takahashi, Hidehiko

2017-01-01

Abstract Psychiatric research has been hampered by an explanatory gap between psychiatric symptoms and their neural underpinnings, which has resulted in poor treatment outcomes. This situation has prompted us to shift from symptom-based diagnosis to data-driven diagnosis, aiming to redefine psychiatric disorders as disorders of neural circuitry. Promising candidates for data-driven diagnosis include resting-state functional connectivity MRI (rs-fcMRI)-based biomarkers. Although biomarkers have been developed with the aim of diagnosing patients and predicting the efficacy of therapy, the focus has shifted to the identification of biomarkers that represent therapeutic targets, which would allow for more personalized treatment approaches. This type of biomarker (i.e., “theranostic biomarker”) is expected to elucidate the disease mechanism of psychiatric conditions and to offer an individualized neural circuit-based therapeutic target based on the neural cause of a condition. To this end, researchers have developed rs-fcMRI-based biomarkers and investigated a causal relationship between potential biomarkers and disease-specific behavior using functional MRI (fMRI)-based neurofeedback on functional connectivity. In this review, we introduce a recent approach for creating a theranostic biomarker, which consists mainly of 2 parts: (1) developing an rs-fcMRI-based biomarker that can predict diagnosis and/or symptoms with high accuracy, and (2) the introduction of a proof-of-concept study investigating the relationship between normalizing the biomarker and symptom changes using fMRI-based neurofeedback. In parallel with the introduction of recent studies, we review rs-fcMRI-based biomarker and fMRI-based neurofeedback, focusing on the technological improvements and limitations associated with clinical use. PMID:28977523

Mapping the Brain.

ERIC Educational Resources Information Center

Begley, Sharon; And Others

1992-01-01

Describes powerful new devices that "peer" through skull and "see" brain at work allowing neuroscientists to pursue the well springs of thought and emotion in their search for the origins of intelligence and language. Discusses the following scanning technologies: Magnetic Resonance Imaging (MRI), Positron Emission Tomography…

Potential applications of microtesla magnetic resonance imaging detected using a superconducting quantum interference device

NASA Astrophysics Data System (ADS)

Myers, Whittier Ryan

This dissertation describes magnetic resonance imaging (MRI) of protons performed in a precession field of 132 muT. In order to increase the signal-to-noise ratio (SNR), a pulsed 40-300 mT magnetic field prepolarizes the sample spins and an untuned second-order superconducting gradiometer coupled to a low transition temperature superconducting quantum interference device (SQUID) detects the subsequent 5.6-kHz spin precession. Imaging sequences including multiple echoes and partial Fourier reconstruction are developed. Calculating the SNR of prepolarized SQUID-detected MRI shows that three-dimensional Fourier imaging yields higher SNR than slice-selection imaging. An experimentally demonstrated field-cycling pulse sequence and post-processing algorithm mitigate image artifacts caused by concomitant gradients in low-field MRI. The magnetic field noise of SQUID untuned detection is compared to the noise of SQUID tuned detection, conventional Faraday detection, and the Nyquist noise generated by conducting biological samples. A second-generation microtesla MRI system employing a low-noise SQUID is constructed to increase SNR. A 2.4-m cubic, eddy-current shield with 6-mm thick aluminum walls encloses the experiment to attenuate external noise. The measured noise is 0.75 fT Hz 1/2 referred to the bottom gradiometer loop. Solenoids wound from 30-strand braided wire to decrease Nyquist noise and cooled by either liquid nitrogen or water polarize the spins. Copper wire coils wound on wooden supports produce the imaging magnetic fields and field gradients. Water phantom images with 0.8 x 0.8 x 10 mm3 resolution have a SNR of 6. Three-dimensional 1.6 x 1.9 x 14 mm3 images of bell peppers and 3 x 3 x 26 mm3 in vivo images of the human arm are presented. Since contrast based on the transverse spin relaxation rate (T1 ) is enhanced at low magnetic fields, microtesla MRI could potentially be used for tumor imaging. The measured T1 of ex vivo normal and cancerous prostate tissue differ significantly at 132 muT. A single-sided MRI system designed for prostate imaging could achieve 3 x 3 x 5 mm3 resolution in 8 minutes. Existing SQUID-based magnetoencephalography (MEG) systems could be used as microtesla MRI detectors. A commercial 275-channel MEG system could acquire 6-minute brain images with (4 mm)3 resolution and SNR 16.

Subclinical ischemic events in patients undergoing carotid artery stent placement: comparison of proximal and distal protection techniques.

PubMed

Aytac, Emrah; Gürkaş, Erdem; Akpinar, Cetin Kursad; Saleem, Muhammad A; Qureshi, Adnan I

2017-10-01

To determine the relative effectiveness of proximal and distal protection in prevention of cerebral ischemic events during carotid artery stent (CAS) placement using diffusion-weighted MRI (DW-MRI). We analyzed data from patients who had undergone DW-MRI before and within 24 hours of CAS for symptomatic internal carotid artery (ICA) stenosis (with last ischemic events within 3 months). The study was performed prospectively; patients were not randomized, and were treated either with a proximal balloon occlusion system (Mo.Ma; Invatec, Roncadelle, Italy) or filter-type distal protection device (Spider device; ev3, Plymouth, Minnesota, USA). Of the 45 patients (mean age±SD: 66.9±9.8 years; 73.3% were men) who underwent CAS, 19 had proximal protection and 26 distal protection. New ischemic lesions were detected in 26/45 patients on DW-MRI scans obtained within 24 hours after CAS. The proportion of patients with new lesions on DW-MRI at 24 hours was not different between the two groups (47.4% vs 65.4% for proximal and distal protection, respectively). The mean number of new ischemic lesions on post-CAS DW-MRI was non-significantly higher in patients who underwent CAS with distal protection (2.80±3.54 for proximal protection vs 4.96±5.11 for distal protection; p=0.12). The proportion of patients with new lesions >1 cm did not differ between the two groups (5.3% for proximal protection vs 11.5% for distal protection; p=0.62). There was no difference in the rates of ischemic stroke between patients who underwent CAS treatment using proximal and distal protection (5.3% vs 7.7%; p=1.000). We found a relatively high rate of new ischemic lesions in patients undergoing CAS with cerebral protection. There was no difference in the proportion of patients with new lesions between patients treated using distal protection and those treated using proximal protection. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

The effect of heart failure and left ventricular assist device treatment on right ventricular mechanics: a computational study.

PubMed

Park, Jun I K; Heikhmakhtiar, Aulia Khamas; Kim, Chang Hyun; Kim, Yoo Seok; Choi, Seong Wook; Song, Kwang Soup; Lim, Ki Moo

2018-05-22

Although it is important to analyze the hemodynamic factors related to the right ventricle (RV) after left ventricular assist device (LVAD) implantation, previous studies have focused only on the alteration of the ventricular shape and lack quantitative analysis of the various hemodynamic parameters. Therefore, we quantitatively analyzed various hemodynamic parameters related to the RV under normal, heart failure (HF), and HF incorporated with continuous flow LVAD therapy by using a computational model. In this study, we combined a three-dimensional finite element electromechanical model of ventricles, which is based on human ventricular morphology captured by magnetic resonance imaging (MRI) with a lumped model of the circulatory system and continuous flow LVAD function in order to construct an integrated model of an LVAD implanted-cardiovascular system. To induce systolic dysfunction, the magnitude of the calcium transient function under HF condition was reduced to 70% of the normal value, and the time constant was reduced by 30% of the normal value. Under the HF condition, the left ventricular end systolic pressure decreased, the left ventricular end diastolic pressure increased, and the pressure in the right atrium (RA), RV, and pulmonary artery (PA) increased compared with the normal condition. The LVAD therapy decreased the end-systolic pressure of the LV by 41%, RA by 29%, RV by 53%, and PA by 71%, but increased the right ventricular ejection fraction by 52% and cardiac output by 40%, while the stroke work was reduced by 67% compared with the HF condition without LVAD. The end-systolic ventricular tension and strain decreased with the LVAD treatment. LVAD enhances CO and mechanical unloading of the LV as well as those of the RV and prevents pulmonary hypertension which can be induced by HF.

Does Low-Field Intraoperative Magnetic Resonance Improve the Results of Endoscopic Pituitary Surgery? Experience of the Implementation of a New Device in a Referral Center.

PubMed

García, Sergio; Reyes, Luis; Roldán, Pedro; Torales, Jorge; Halperin, Irene; Hanzu, Felicia; Langdon, Cristobal; Alobid, Isam; Enseñat, Joaquim

2017-06-01

To assess the contribution of low-field intraoperative magnetic resonance (iMRI) to endoscopic pituitary surgery. We analyzed a prospective series of patients undergoing endoscopic endonasal surgery for pituitary macroadenomas assisted with a low-field iMRI (PoleStarN30, 0.15 T [Medtronic]). Clinical, radiologic, and surgical variables were analyzed and compared with our fully endoscopic historic cohort operated on without iMRI assistance. A bibliographic review of pituitary surgery assisted with iMRI was conducted. Thirty patients (57% female; mean age, 55 years) were prospectively analyzed. The most frequent tumor subtype was nonfunctioning macroadenoma (50%). The average Knosp grade was 2.3 and mean tumor size was 18 mm. Surgical and positioning time were 102 and 47 minutes, respectively. Hospital stay and complication rates were similar to our historical cohort for pituitary surgery. Mean follow-up was 10 months. Complete resection (CR) was achieved in 83% of patients. Seven patients (23%) benefited from iMRI assistance and achieved a CR in their surgeries. All patients except 1 experienced hormonal activity remission. iMRI sensitivity and specificity was 0.8 and 1, respectively. Although not statistically significant, CR rates were globally 11.5% superior in iMRI series compared with our historical cohort. This difference was independent of cavernous sinus invasiveness grade (CR rate increased 12.5% for Knosp grade 0-2 and 8.1% for Knosp grade 3-4). Low-field iMRI is a useful and safe assistance even in advanced surgical techniques such as endoscopy. Its contribution is limited by the intrinsic features of the tumor. Further randomized studies are required to confirm the cost-effectiveness of iMRI in pituitary surgery. Copyright © 2017 Elsevier Inc. All rights reserved.

Brain activation patterns elicited by the 'Faces Symbol Test' -- a pilot fMRI study.

PubMed

Grabner, Rh; Popotnig, F; Ropele, S; Neuper, C; Gorani, F; Petrovic, K; Ebner, F; Strasser-Fuchs, S; Fazekas, F; Enzinger, C

2008-04-01

The Faces Symbol Test (FST) has recently been proposed as a brief and patient-friendly screening instrument for the assessment of cognitive dysfunction in patients with multiple sclerosis (MS). However, in contrast to well-established MS screening tests such as the Paced Auditory Serial Addition Test, the neural correlates of the FST have not been investigated so far. In the present study, we developed a functional MRI (fMRI) version of the FST to provide first data on brain regions and networks involved in this test. A sample of 19 healthy participants completed a version of the FST adapted for fMRI, requiring matching of faces and symbols in a multiple choice test and two further experimental conditions drawing on cognitive subcomponents (face matching and symbol matching). Imaging data showed a differential involvement of a fronto-parieto-occipital network in the three conditions. The most demanding FST condition elicited brain activation patterns related with sustained attention and executive control. These results suggest that the FST recruits brain networks critical for higher-order cognitive functions often impaired in MS patients.

Initial tests of a prototype MRI-compatible PET imager

NASA Astrophysics Data System (ADS)

Raylman, Raymond R.; Majewski, Stan; Lemieux, Susan; Velan, S. Sendhil; Kross, Brain; Popov, Vladimir; Smith, Mark F.; Weisenberger, Andrew G.; Wojcik, Randy

2006-12-01

Multi-modality imaging is rapidly becoming a valuable tool in the diagnosis of disease and in the development of new drugs. Functional images produced with PET fused with anatomical structure images created by MRI, will allow the correlation of form with function. Our group (a collaboration of West Virginia University and Jefferson Lab) is developing a system to acquire MRI and PET images contemporaneously. The prototype device consists of two opposed detector heads, operating in coincidence mode with an active FOV of 5×5×4 cm 3. Each MRI-PET detector module consists of an array of LSO detector elements (2.5×2.5×15 mm 3) coupled through a long fiber optic light guide to a single Hamamatsu flat panel PSPMT. The fiber optic light guide is made of a glued assembly of 2 mm diameter acrylic fibers with a total length of 2.5 m. The use of a light guides allows the PSPMTs to be positioned outside the bore of the 3 T General Electric MRI scanner used in the tests. Photon attenuation in the light guides resulted in an energy resolution of ˜60% FWHM, interaction of the magnetic field with PSPMT further reduced energy resolution to ˜85% FWHM. Despite this effect, excellent multi-plane PET and MRI images of a simple disk phantom were acquired simultaneously. Future work includes improved light guides, optimized magnetic shielding for the PSPMTs, construction of specialized coils to permit high-resolution MRI imaging, and use of the system to perform simultaneous PET and MRI or MR-spectroscopy .

Functional-anatomic study of episodic retrieval using fMRI. I. Retrieval effort versus retrieval success.

PubMed

Buckner, R L; Koutstaal, W; Schacter, D L; Wagner, A D; Rosen, B R

1998-04-01

A number of recent functional imaging studies have identified brain areas activated during tasks involving episodic memory retrieval. The identification of such areas provides a foundation for targeted hypotheses regarding the more specific contributions that these areas make to episodic retrieval. As a beginning effort toward such an endeavor, whole-brain functional magnetic resonance imaging (fMRI) was used to examine 14 subjects during episodic word recognition in a block-designed fMRI experiment. Study conditions were manipulated by presenting either shallow or deep encoding tasks. This manipulation yielded two recognition conditions that differed with regard to retrieval effort and retrieval success: shallow encoding yielded low levels of recognition success with high levels of retrieval effort, and deep encoding yielded high levels of recognition success with low levels of effort. Many brain areas were activated in common by these two recognition conditions compared to a low-level fixation condition, including left and right prefrontal regions often detected during PET episodic retrieval paradigms (e.g., R. L. Buckner et al., 1996, J. Neurosci. 16, 6219-6235) thereby generalizing these findings to fMRI. Characterization of the activated regions in relation to the separate recognition conditions showed (1) bilateral anterior insular regions and a left dorsal prefrontal region were more active after shallow encoding, when retrieval demanded greatest effort, and (2) right anterior prefrontal cortex, which has been implicated in episodic retrieval, was most active during successful retrieval after deep encoding. We discuss these findings in relation to component processes involved in episodic retrieval and in the context of a companion study using event-related fMRI.

Squid detected NMR and MRI at ultralow fields

DOEpatents

Clarke, John [Berkeley, CA; McDermott, Robert [Louisville, CO; Pines, Alexander [Berkeley, CA; Trabesinger, Andreas Heinz [CH-8006 Zurich, CH

2007-05-15

Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

Squid detected NMR and MRI at ultralow fields

DOEpatents

Clarke, John; McDermott, Robert; Pines, Alexander; Trabesinger, Andreas Heinz

2006-05-30

Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

Squid detected NMR and MRI at ultralow fields

DOEpatents

Clarke, John [Berkeley, CA; Pines, Alexander [Berkeley, CA; McDermott, Robert F [Monona, WI; Trabesinger, Andreas H [London, GB

2008-12-16

Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

SQUID detected NMR and MRI at ultralow fields

DOEpatents

Clarke, John; McDermott, Robert; Pines, Alexander; Trabesinger, Andreas Heinz

2006-10-03

Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

Threats to ultra-high-field MRI

NASA Astrophysics Data System (ADS)

Le Bihan, Denis

2009-08-01

In 2004 the European Commission (EC) adopted a directive restricting occupational exposure to electromagnetic fields. This directive (2004/40/CE), which examines the possible health risks of the electromagnetic fields from mobile phones, Wi-Fi, Bluetooth and other devices, concluded that upper limits on radiation and applied electromagnetic fields are necessary to prevent workers from suffering any undue acute health effects. But although not initially intended, the biggest impact of the directive could be on magnetic resonance imaging (MRI), which is used in hospitals worldwide to produce images of unrivalled quality of the brain and other soft tissues.

Real-time magnetic resonance imaging-guided transcatheter aortic valve replacement.

PubMed

Miller, Justin G; Li, Ming; Mazilu, Dumitru; Hunt, Tim; Horvath, Keith A

2016-05-01

To demonstrate the feasibility of Real-time magnetic resonance imaging (rtMRI) guided transcatheter aortic valve replacement (TAVR) with an active guidewire and an MRI compatible valve delivery catheter system in a swine model. The CoreValve system was minimally modified to be MRI-compatible by replacing the stainless steel components with fluoroplastic resin and high-density polyethylene components. Eight swine weighing 60-90 kg underwent rtMRI-guided TAVR with an active guidewire through a left subclavian approach. Two imaging planes (long-axis view and short-axis view) were used simultaneously for real-time imaging during implantation. Successful deployment was performed without rapid ventricular pacing or cardiopulmonary bypass. Postdeployment images were acquired to evaluate the final valve position in addition to valvular and cardiac function. Our results show that the CoreValve can be easily and effectively deployed through a left subclavian approach using rtMRI guidance, a minimally modified valve delivery catheter system, and an active guidewire. This method allows superior visualization before deployment, thereby allowing placement of the valve with pinpoint accuracy. rtMRI has the added benefit of the ability to perform immediate postprocedural functional assessment, while eliminating the morbidity associated with radiation exposure, rapid ventricular pacing, contrast media renal toxicity, and a more invasive procedure. Use of a commercially available device brings this rtMRI-guided approach closer to clinical reality. Copyright © 2016 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

Segmentation precision of abdominal anatomy for MRI-based radiotherapy

PubMed Central

Noel, Camille E.; Zhu, Fan; Lee, Andrew Y.; Yanle, Hu; Parikh, Parag J.

2014-01-01

The limited soft tissue visualization provided by computed tomography, the standard imaging modality for radiotherapy treatment planning and daily localization, has motivated studies on the use of magnetic resonance imaging (MRI) for better characterization of treatment sites, such as the prostate and head and neck. However, no studies have been conducted on MRI-based segmentation for the abdomen, a site that could greatly benefit from enhanced soft tissue targeting. We investigated the interobserver and intraobserver precision in segmentation of abdominal organs on MR images for treatment planning and localization. Manual segmentation of 8 abdominal organs was performed by 3 independent observers on MR images acquired from 14 healthy subjects. Observers repeated segmentation 4 separate times for each image set. Interobserver and intraobserver contouring precision was assessed by computing 3-dimensional overlap (Dice coefficient [DC]) and distance to agreement (Hausdorff distance [HD]) of segmented organs. The mean and standard deviation of intraobserver and interobserver DC and HD values were DCintraobserver = 0.89 ± 0.12, HDintraobserver = 3.6 mm ± 1.5, DCinterobserver = 0.89 ± 0.15, and HDinterobserver = 3.2 mm ± 1.4. Overall, metrics indicated good interobserver/intraobserver precision (mean DC > 0.7, mean HD < 4 mm). Results suggest that MRI offers good segmentation precision for abdominal sites. These findings support the utility of MRI for abdominal planning and localization, as emerging MRI technologies, techniques, and onboard imaging devices are beginning to enable MRI-based radiotherapy. PMID:24726701

Segmentation precision of abdominal anatomy for MRI-based radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noel, Camille E.; Zhu, Fan; Lee, Andrew Y.

2014-10-01

The limited soft tissue visualization provided by computed tomography, the standard imaging modality for radiotherapy treatment planning and daily localization, has motivated studies on the use of magnetic resonance imaging (MRI) for better characterization of treatment sites, such as the prostate and head and neck. However, no studies have been conducted on MRI-based segmentation for the abdomen, a site that could greatly benefit from enhanced soft tissue targeting. We investigated the interobserver and intraobserver precision in segmentation of abdominal organs on MR images for treatment planning and localization. Manual segmentation of 8 abdominal organs was performed by 3 independent observersmore » on MR images acquired from 14 healthy subjects. Observers repeated segmentation 4 separate times for each image set. Interobserver and intraobserver contouring precision was assessed by computing 3-dimensional overlap (Dice coefficient [DC]) and distance to agreement (Hausdorff distance [HD]) of segmented organs. The mean and standard deviation of intraobserver and interobserver DC and HD values were DC{sub intraobserver} = 0.89 ± 0.12, HD{sub intraobserver} = 3.6 mm ± 1.5, DC{sub interobserver} = 0.89 ± 0.15, and HD{sub interobserver} = 3.2 mm ± 1.4. Overall, metrics indicated good interobserver/intraobserver precision (mean DC > 0.7, mean HD < 4 mm). Results suggest that MRI offers good segmentation precision for abdominal sites. These findings support the utility of MRI for abdominal planning and localization, as emerging MRI technologies, techniques, and onboard imaging devices are beginning to enable MRI-based radiotherapy.« less

Real-time MRI guidance of cardiac interventions.

PubMed

Campbell-Washburn, Adrienne E; Tavallaei, Mohammad A; Pop, Mihaela; Grant, Elena K; Chubb, Henry; Rhode, Kawal; Wright, Graham A

2017-10-01

Cardiac magnetic resonance imaging (MRI) is appealing to guide complex cardiac procedures because it is ionizing radiation-free and offers flexible soft-tissue contrast. Interventional cardiac MR promises to improve existing procedures and enable new ones for complex arrhythmias, as well as congenital and structural heart disease. Guiding invasive procedures demands faster image acquisition, reconstruction and analysis, as well as intuitive intraprocedural display of imaging data. Standard cardiac MR techniques such as 3D anatomical imaging, cardiac function and flow, parameter mapping, and late-gadolinium enhancement can be used to gather valuable clinical data at various procedural stages. Rapid intraprocedural image analysis can extract and highlight critical information about interventional targets and outcomes. In some cases, real-time interactive imaging is used to provide a continuous stream of images displayed to interventionalists for dynamic device navigation. Alternatively, devices are navigated relative to a roadmap of major cardiac structures generated through fast segmentation and registration. Interventional devices can be visualized and tracked throughout a procedure with specialized imaging methods. In a clinical setting, advanced imaging must be integrated with other clinical tools and patient data. In order to perform these complex procedures, interventional cardiac MR relies on customized equipment, such as interactive imaging environments, in-room image display, audio communication, hemodynamic monitoring and recording systems, and electroanatomical mapping and ablation systems. Operating in this sophisticated environment requires coordination and planning. This review provides an overview of the imaging technology used in MRI-guided cardiac interventions. Specifically, this review outlines clinical targets, standard image acquisition and analysis tools, and the integration of these tools into clinical workflow. 1 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2017;46:935-950. © 2017 International Society for Magnetic Resonance in Medicine.

Electromyography as a recording system for eyeblink conditioning with functional magnetic resonance imaging.

PubMed

Knuttinen, M-G; Parrish, T B; Weiss, C; LaBar, K S; Gitelman, D R; Power, J M; Mesulam, M-M; Disterhoft, J F

2002-10-01

This study was designed to develop a suitable method of recording eyeblink responses while conducting functional magnetic resonance imaging (fMRI). Given the complexity of this behavioral setup outside of the magnet, this study sought to adapt and further optimize an approach to eyeblink conditioning that would be suitable for conducting event-related fMRI experiments. This method involved the acquisition of electromyographic (EMG) signals from the orbicularis oculi of the right eye, which were subsequently amplified and converted into an optical signal outside of the head coil. This optical signal was converted back into an electrical signal once outside the magnet room. Electromyography (EMG)-detected eyeblinks were used to measure responses in a delay eyeblink conditioning paradigm. Our results indicate that: (1) electromyography is a sensitive method for the detection of eyeblinks during fMRI; (2) minimal interactions or artifacts of the EMG signal were created from the magnetic resonance pulse sequence; and (3) no electromyography-related artifacts were detected in the magnetic resonance images. Furthermore, an analysis of the functional data showed areas of activation that have previously been shown in positron emission tomography studies of human eyeblink conditioning. Our results support the strength of this behavioral setup as a suitable method to be used in association with fMRI.

RESCUE - Reduction of MRI SNR Degradation by Using an MR-Synchronous Low-Interference PET Acquisition Technique

NASA Astrophysics Data System (ADS)

Gebhardt, Pierre; Wehner, Jakob; Weissler, Bjoern; Frach, Thomas; Marsden, Paul K.; Schulz, Volkmar

2015-06-01

Devices aiming at combined Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) to enable simultaneous PET/MR image acquisition have to fulfill demanding requirements to avoid mutual magneticas well as electromagnetic-field-related interferences which lead to image quality degradation. Particularly Radio-Frequency (RF)-field-related interferences between PET and MRI may lead to MRI SNR reduction, thereby deteriorating MR image quality. RF shielding of PET electronics is therefore commonly applied to reduce RF emission and lower the potential coupling into MRI RF coil(s). However, shields introduce eddy-current-induced MRI field distortions and should thus be minimized or ideally omitted. Although the MRI noise floor increase caused by a PET system might be acceptable for many MRI applications, some MRI protocols, such as fast or high-resolution MRI scans, typically suffer from low SNR and might need more attention regarding RF silence to preserve the intrinsic MRI SNR. For such cases, we propose RESCUE, an MRI-synchronously-gated PET data acquisition technique: By interrupting the PET acquisition during MR signal receive phases, PET-related RF emission may be minimized, leading to MRI SNR preservation. Our PET insert Hyperion IID using Philips Digital Photon Counting (DPC) sensors serves as the platform to demonstrate RESCUE. To make the DPC sensor suitable for RESCUE to be applied for many MRI sequences with acquisition time windows in the range of a few milliseconds, we present in this paper a new technique which enables rapid DPC sensor operation interruption by dramatically lowering the overhead time to interrupt and restart the sensor operation. Procedures to enter and leave gated PET data acquisition may imply sensitivity losses which add to the ones occurring during MRI RF acquisition. For the case of our PET insert, the new DPC quick-interruption technique yields a PET sensitivity loss reduction by a factor of 78 when compared to the loss introduced with the standard start/stop procedure. For instance, PET sensitivity losses related to overhead time are 2.9% in addition to the loss related to PET gating being equal to the MRI RF acquisition duty cycle (14.7%) for an exemplary T1-weighted 3D-FFE MRI sequence. MRI SNR measurement results obtained with one Singles Detection Module (SDM) using no RF shield demonstrate a noise floor reduction by a factor of 2.1, getting close to the noise floor level of the SNR reference scan (SDM off-powered) when RESCUE was active.

Finger Position Alters the Median Nerve Properties within the Carpal Tunnel: A Pre-Post MRI Comparison Study

PubMed Central

Nadar, Mohammed Shaban; Dashti, Mohsen H.; Cherian, Jigimon

2013-01-01

Purpose The purpose of this study was to compare the properties of the median nerve and the flexor retinaculum within the carpal tunnel with Magnetic Resonance Imaging (MRI) under two conditions: (a) fingers extended, and (b) fingers in an isometric squeeze grip. Methods Thirty-Four volunteers participated in this experimental study. The flexor retinaculum and median nerve characteristics were measured during both conditions using MRI. Results The isometric squeeze grip condition resulted in significant palmar bowing of the flexor retinaculum (t = 7.67, p<.001), a significant flattening-ratio of the median nerve (t = 4.308, p<.001), and no significant decrease in the cross-sectional area of the median nerve (t = 2.508, p = 0.017). Conclusion The isometric squeeze grip condition resulted in anatomical deformations within the carpal tunnel, possibly explained by the lumbrical muscles incursion into the carpal tunnel during finger flexion. PMID:24265763

Muscle MRI in female carriers of dystrophinopathy.

PubMed

Tasca, G; Monforte, M; Iannaccone, E; Laschena, F; Ottaviani, P; Silvestri, G; Masciullo, M; Mirabella, M; Servidei, S; Ricci, E

2012-09-01

Duchenne muscular dystrophy carriers represent a rare condition that needs to be recognized because of the possible implications for prenatal diagnosis. Muscle biopsy is currently the diagnostic instrument of choice in sporadic patients. We wanted to verify whether muscle magnetic resonance imaging (MRI) could identify a pattern of involvement suggestive of this condition and whether it was similar to that reported in Duchenne and Becker muscular dystrophy. Evaluation of pelvic and lower limb MRI scans of 12 dystrophinopathy carriers was performed. We found a frequent involvement of the quadratus femoris, gluteus maximus and medius, biceps femoris long head, adductor magnus, vasti and paraspinal muscles, whilst the popliteus, iliopsoas, recti abdominis, sartorius, and gracilis were relatively spared. Asymmetry was a major feature on MRI; it could be detected significantly more often than with sole clinical examination and even in patients without weakness. The pattern we describe here is similar to that reported in Duchenne and Becker muscular dystrophy, although asymmetry represents a major distinctive feature. Muscle MRI was more sensitive than clinical examination for detecting single muscle involvement and asymmetry. Further studies are needed to verify the consistency of this pattern in larger cohorts and to assess whether muscle MRI can improve diagnostic accuracy in carriers with normal dystrophin staining on muscle biopsy. © 2012 The Author(s) European Journal of Neurology © 2012 EFNS.

MRI CRITERIA FOR THE DIAGNOSIS OF MULTIPLE SCLEROSIS: MAGNIMS CONSENSUS GUIDELINES

PubMed Central

Filippi, M.; Rocca, M.A.; Ciccarelli, O.; De Stefano, N.; Evangelou, N.; Kappos, L.; Rovira, A.; Sastre-Garriga, J.; Tintorè, M.; Frederiksen, J.L.; Gasperini, C.; Palace, J.; Reich, D.S.; Banwell, B.; Montalban, X.; Barkhof, F.

2016-01-01

Summary In patients presenting with a clinically isolated syndrome (CIS), magnetic resonance imaging (MRI) can support and substitute clinical information for multiple sclerosis (MS) diagnosis demonstrating disease dissemination in space (DIS) and time (DIT) and helping to rule out other conditions that can mimic MS. From their inclusion in the diagnostic work-up for MS in 2001, several modifications of MRI diagnostic criteria have been proposed, in the attempt to simplify lesion-count models for demonstrating DIS, change the timing of MRI scanning for demonstrating DIT, and increase the value of spinal cord imaging. Since the last update of these criteria, new data regarding the application of MRI for demonstrating DIS and DIT have become available and improvement in MRI technology has occurred. State-of-the-art MRI findings in these patients were discussed in a MAGNIMS workshop, the goal of which was to provide an evidence-based and expert-opinion consensus on diagnostic MRI criteria modifications. PMID:26822746

Variability comparison of simultaneous brain near-infrared spectroscopy (NIRS) and functional MRI (fMRI) during visual stimulation

PubMed Central

Minati, Ludovico; Visani, Elisa; Dowell, Nick G; Medford, Nick; Critchley, Hugo D

2011-01-01

Brain near-infrared spectroscopy (NIRS) is emerging as a potential alternative to functional MRI (fMRI). To date, no study has explicitly compared the two techniques in terms of measurement variability, a key parameter dictating attainable statistical power. Here, NIRS and fMRI were simultaneously recorded during event-related visual stimulation. Inter-subject coefficients of variation (CVs) for peak response amplitude were considerably larger for NIRS than fMRI, but inter-subject CVs for response latency and intra-subject CVs for response amplitude were overall comparable. Our results may represent an optimistic estimate of the CVs of NIRS measurements, as optode positioning was guided by structural MRI, which is normally unavailable. We conclude that fMRI may be preferable to NIRS for group comparisons, but NIRS is equally powerful when comparing conditions within participants. The discrepancy between inter- and intra-subject CVs is likely related to variability in head anatomy and tissue properties which may be better accounted for by emerging NIRS technology. PMID:21780948

Breaking down the barriers: fMRI applications in pain, analgesia and analgesics

PubMed Central

Borsook, David; Becerra, Lino R

2006-01-01

This review summarizes functional magnetic resonance imaging (fMRI) findings that have informed our current understanding of pain, analgesia and related phenomena, and discusses the potential role of fMRI in improved therapeutic approaches to pain. It is divided into 3 main sections: (1) fMRI studies of acute and chronic pain. Physiological studies of pain have found numerous regions of the brain to be involved in the interpretation of the 'pain experience'; studies in chronic pain conditions have identified a significant CNS component; and fMRI studies of surrogate models of chronic pain are also being used to further this understanding. (2) fMRI studies of endogenous pain processing including placebo, empathy, attention or cognitive modulation of pain. (3) The use of fMRI to evaluate the effects of analgesics on brain function in acute and chronic pain. fMRI has already provided novel insights into the neurobiology of pain. These insights should significantly advance therapeutic approaches to chronic pain. PMID:16982005

T2-weighted four dimensional magnetic resonance imaging with result-driven phase sorting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yilin; Yin, Fang-Fang; Cai, Jing, E-mail: jing.cai@duke.edu

2015-08-15

Purpose: T2-weighted MRI provides excellent tumor-to-tissue contrast for target volume delineation in radiation therapy treatment planning. This study aims at developing a novel T2-weighted retrospective four dimensional magnetic resonance imaging (4D-MRI) phase sorting technique for imaging organ/tumor respiratory motion. Methods: A 2D fast T2-weighted half-Fourier acquisition single-shot turbo spin-echo MR sequence was used for image acquisition of 4D-MRI, with a frame rate of 2–3 frames/s. Respiratory motion was measured using an external breathing monitoring device. A phase sorting method was developed to sort the images by their corresponding respiratory phases. Besides, a result-driven strategy was applied to effectively utilize redundantmore » images in the case when multiple images were allocated to a bin. This strategy, selecting the image with minimal amplitude error, will generate the most representative 4D-MRI. Since we are using a different image acquisition mode for 4D imaging (the sequential image acquisition scheme) with the conventionally used cine or helical image acquisition scheme, the 4D dataset sufficient condition was not obviously and directly predictable. An important challenge of the proposed technique was to determine the number of repeated scans (N{sub R}) required to obtain sufficient phase information at each slice position. To tackle this challenge, the authors first conducted computer simulations using real-time position management respiratory signals of the 29 cancer patients under an IRB-approved retrospective study to derive the relationships between N{sub R} and the following factors: number of slices (N{sub S}), number of 4D-MRI respiratory bins (N{sub B}), and starting phase at image acquisition (P{sub 0}). To validate the authors’ technique, 4D-MRI acquisition and reconstruction were simulated on a 4D digital extended cardiac-torso (XCAT) human phantom using simulation derived parameters. Twelve healthy volunteers were involved in an IRB-approved study to investigate the feasibility of this technique. Results: 4D data acquisition completeness (C{sub p}) increases as NR increases in an inverse-exponential fashion (C{sub p} = 100 − 99 × exp(−0.18 × N{sub R}), when N{sub B} = 6, fitted using 29 patients’ data). The N{sub R} required for 4D-MRI reconstruction (defined as achieving 95% completeness, C{sub p} = 95%, N{sub R} = N{sub R,95}) is proportional to N{sub B} (N{sub R,95} ∼ 2.86 × N{sub B}, r = 1.0), but independent of N{sub S} and P{sub 0}. Simulated XCAT 4D-MRI showed a clear pattern of respiratory motion. Tumor motion trajectories measured on 4D-MRI were comparable to the average input signal, with a mean relative amplitude error of 2.7% ± 2.9%. Reconstructed 4D-MRI for healthy volunteers illustrated clear respiratory motion on three orthogonal planes, with minimal image artifacts. The artifacts were presumably caused by breathing irregularity and incompleteness of data acquisition (95% acquired only). The mean relative amplitude error between critical structure trajectory and average breathing curve for 12 healthy volunteers is 2.5 ± 0.3 mm in superior–inferior direction. Conclusions: A novel T2-weighted retrospective phase sorting 4D-MRI technique has been developed and successfully applied on digital phantom and healthy volunteers.« less

Intrathecal Pump Exposure to Electromagnetic Interference: A Report of Device Interrogation following Multiple ECT Sessions.

PubMed

Bicket, Mark C; Hanna, George M

2016-02-01

Intrathecal drug delivery systems represent an increasingly common treatment modality for patients with a variety of conditions, including chronic pain and spasticity. Pumps rely on electronic programming to properly control and administer highly concentrated medications. Electromagnetic interference (EMI) is a known exposure that may cause a potential patient safety issue stemming from direct patient injury, pump damage, or changes to pump operation or flow rate. The objective of our case report was to describe an approach to evaluating a patient with a pump prior to and following exposure to EMI from electroconvulsive therapy (ECT), as well as to document findings from device interrogations associated with this event. Case report. Academic university-based pain management center. We present the case of a patient with an intrathecal pump who underwent multiple exposures to EMI in the form of 42 ECT sessions. Interrogation of the intrathecal drug delivery system revealed no safety issues following ECT sessions. At no time were error messages, unintentional changes in event logs, unintentional changes in pump settings, or evidence of pump stall or over-infusion noted. Communication with multiple entities (patient, family, consulting physicians, and device manufacturer) and maintaining vigilance through device interrogation both before and after EMI exposure are appropriate safeguards to mitigate the risk and detect potential adverse events of EMI with intrathecal drug delivery systems. Given the infrequent reports of device exposure to ECT, best practices may be derived from experience with EMI exposure from magnetic resonance imaging (MRI). Although routine EMI exposure to intrathecal drug delivery systems should be avoided, we describe one patient with repeated exposure to ECT without apparent complication.

Design and implementation of a MRI compatible and dynamic phantom simulating the motion of a tumor in the liver under the breathing cycle

NASA Astrophysics Data System (ADS)

Geelhand de Merxem, Arnould; Lechien, Vianney; Thibault, Tanguy; Dasnoy, Damien; Macq, Benoît

2017-11-01

In the context of cancer treatment by proton therapy, research is carried out on the use magnetic resonance imaging (MRI) to perform real-time tracking of tumors during irradiation. The purpose of this combination is to reduce the irradiation of healthy tissues surrounding the tumor, while using a non-ionizing imaging method. Therefore, it is necessary to validate the tracking algorithms on real-time MRI sequences by using physical simulators, i.e. a phantom. Our phantom is a device representing a liver with hepatocellular carcinoma, a stomach and a pancreas close to the anatomy and the magnetic properties of the human body, animated by a motion similar to the one induced by the respiration. Many anatomical or mobile phantoms already exist, but the purpose here is to combine a reliable representation of the abdominal organs with the creation and the evaluation of a programmable movement in the same device, which makes it unique. The phantom is composed of surrogate organs made of CAGN gels. These organs are placed in a transparent box filled with water and attached to an elastic membrane. A programmable electro-pneumatic system creates a movement, similarly to a human diaphragm, by inflating and deflating the membrane. The average relaxation times of the synthetic organs belongs to a range corresponding to the human organs values (T1 = [458.7-1660] ms, T2 = [39.3-89.1] ms). The displacement of the tumor is tracked in real time by a camera inside the MRI. The amplitude of the movement varies from 12.8 to 20.1 mm for a periodic and repeatable movement. Irregular breath patterns can be created with a maximum amplitude of 40 mm.

Radiofrequency heating of metallic dental devices during 3.0 T MRI

PubMed Central

Hasegawa, M; Miyata, K; Abe, Y; Ishigami, T

2013-01-01

Objectives: To estimate the risk of injury from radiofrequency (RF) heating of metallic dental devices in use during 3.0 T MRI. Methods: The whole-body specific absorption rate (WB-SAR) was calculated on the basis of saline temperature elevation under the maximum RF irradiation for 15 min to determine the operation parameters for the heating test. The temperature changes of three types of three-unit bridges, a full-arch fixed dental prosthesis and an orthodontic appliance in use during MRI with a 3.0 T MR system (Magnetom® Verio; Siemens AG, Erlangen, Germany) were then tested in accordance with the American Society for Testing and Materials F2182-09 standardized procedure under the maximum RF heating during 15 min RF irradiation. Results: The system console-predicted WB-SAR was approximately 1.4 W kg−1 and that measured with a saline phantom was 2.1 W kg−1. In the assessment of RF heating, the highest temperature increase was +1.80 °C in the bridges, +1.59 °C in the full-arch fixed dental prosthesis and +2.61 °C in the orthodontic appliance. Conclusions: The relatively minor RF heating of dental casting material-based prostheses in Magnetom Verio systems in the normal operating mode should not pose a risk to patients. However, orthodontic appliances may exhibit RF heating above the industrial standard (CENELEC standard prEN45502-2-3); therefore, the wire should be removed from the bracket or a spacer should be used between the appliance and the oral mucosa during MRI. PMID:23520391

Design and development of novel MRI compatible zirconium- ruthenium alloys with ultralow magnetic susceptibility

PubMed Central

Li, H.F.; Zhou, F.Y.; Li, L.; Zheng, Y.F.

2016-01-01

In the present study, novel MRI compatible zirconium-ruthenium alloys with ultralow magnetic susceptibility were developed for biomedical and therapeutic devices under MRI diagnostics environments. The results demonstrated that alloying with ruthenium into pure zirconium would significantly increase the strength and hardness properties. The corrosion resistance of zirconium-ruthenium alloys increased significantly. High cell viability could be found and healthy cell morphology observed when culturing MG 63 osteoblast-like cells and L-929 fibroblast cells with zirconium-ruthenium alloys, whereas the hemolysis rates of zirconium-ruthenium alloys are <1%, much lower than 5%, the safe value for biomaterials according to ISO 10993-4 standard. Compared with conventional biomedical 316L stainless steel, Co–Cr alloys and Ti-based alloys, the magnetic susceptibilities of the zirconium-ruthenium alloys (1.25 × 10−6 cm3·g−1–1.29 × 10−6 cm3·g−1 for zirconium-ruthenium alloys) are ultralow, about one-third that of Ti-based alloys (Ti–6Al–4V, ~3.5 × 10−6 cm3·g−1, CP Ti and Ti–6Al–7Nb, ~3.0 × 10−6 cm3·g−1), and one-sixth that of Co–Cr alloys (Co–Cr–Mo, ~7.7 × 10−6 cm3·g−1). Among the Zr–Ru alloy series, Zr–1Ru demonstrates enhanced mechanical properties, excellent corrosion resistance and cell viability with lowest magnetic susceptibility, and thus is the optimal Zr–Ru alloy system as therapeutic devices under MRI diagnostics environments. PMID:27090955

MRI-guided and CT-guided cervical nerve root infiltration therapy: a cost comparison.

PubMed

Maurer, M H; Froeling, V; Röttgen, R; Bretschneider, T; Hartwig, T; Disch, A C; de Bucourt, M; Hamm, B; Streitparth, F

2014-06-01

To evaluate and compare the costs of MRI-guided and CT-guided cervical nerve root infiltration for the minimally invasive treatment of radicular neck pain. Between September 2009 and April 2012, 22 patients (9 men, 13 women; mean age: 48.2 years) underwent MRI-guided (1.0 Tesla, Panorama HFO, Philips) single-site periradicular cervical nerve root infiltration with 40 mg triamcinolone acetonide. A further 64 patients (34 men, 30 women; mean age: 50.3 years) were treated under CT fluoroscopic guidance (Somatom Definition 64, Siemens). The mean overall costs were calculated as the sum of the prorated costs of equipment use (purchase, depreciation, maintenance, and energy costs), personnel costs and expenditure for disposables that were identified for MRI- and CT-guided procedures. Additionally, the cost of ultrasound guidance was calculated. The mean intervention time was 24.9 min. (range: 12 - 36 min.) for MRI-guided infiltration and 19.7 min. (range: 5 - 54 min.) for CT-guided infiltration. The average total costs per patient were EUR 240 for MRI-guided interventions and EUR 124 for CT-guided interventions. These were (MRI/CT guidance) EUR 150/60 for equipment use, EUR 46/40 for personnel, and EUR 44/25 for disposables. The mean overall cost of ultrasound guidance was EUR 76. Cervical nerve root infiltration using MRI guidance is still about twice as expensive as infiltration using CT guidance. However, since it does not involve radiation exposure for patients and personnel, MRI-guided nerve root infiltration may become a promising alternative to the CT-guided procedure, especially since a further price decrease is expected for MRI devices and MR-compatible disposables. In contrast, ultrasound remains the less expensive method for nerve root infiltration guidance. © Georg Thieme Verlag KG Stuttgart · New York.

Application unit for the administration of contrast gases for pulmonary magnetic resonance imaging: optimization of ventilation distribution for (3) He-MRI.

PubMed

Güldner, M; Becker, St; Wolf, U; Düber, C; Friesenecker, A; Gast, K K; Heil, W; Hoffmann, C; Karpuk, S; Otten, E W; Rivoire, J; Salhi, Z; Scholz, A; Schreiber, L M; Terekhov, M

2015-09-01

MRI of lung airspaces using gases with MR-active nuclei ((3) He, (129) Xe, and (19) F) is an important area of research in pulmonary imaging. The volume-controlled administration of gas mixtures is important for obtaining quantitative information from MR images. State-of-the-art gas administration using plastic bags (PBs) does not allow for a precise determination of both the volume and timing of a (3) He bolus. A novel application unit (AU) was built according to the requirements of the German medical devices law. Integrated spirometers enable the monitoring of the inhaled gas flow. The device is particularly suited for hyperpolarized (HP) gases (e.g., storage and administration with minimal HP losses). The setup was tested in a clinical trial (n = 10 healthy volunteers) according to the German medicinal products law using static and dynamic ventilation HP-(3) He MRI. The required specifications for the AU were successfully realized. Compared to PB-administration, better reproducibility of gas intrapulmonary distribution was observed when using the AU for both static and dynamic ventilation imaging. The new AU meets the special requirements for HP gases, which are storage and administration with minimal losses. Our data suggest that gas AU-administration is superior to manual modes for determining the key parameters of dynamic ventilation measurements. © 2014 Wiley Periodicals, Inc.

Instrumentation and method for measuring NIR light absorbed in tissue during MR imaging in medical NIRS measurements

NASA Astrophysics Data System (ADS)

Myllylä, Teemu S.; Sorvoja, Hannu S. S.; Nikkinen, Juha; Tervonen, Osmo; Kiviniemi, Vesa; Myllylä, Risto A.

2011-07-01

Our goal is to provide a cost-effective method for examining human tissue, particularly the brain, by the simultaneous use of functional magnetic resonance imaging (fMRI) and near-infrared spectroscopy (NIRS). Due to its compatibility requirements, MRI poses a demanding challenge for NIRS measurements. This paper focuses particularly on presenting the instrumentation and a method for the non-invasive measurement of NIR light absorbed in human tissue during MR imaging. One practical method to avoid disturbances in MR imaging involves using long fibre bundles to enable conducting the measurements at some distance from the MRI scanner. This setup serves in fact a dual purpose, since also the NIRS device will be less disturbed by the MRI scanner. However, measurements based on long fibre bundles suffer from light attenuation. Furthermore, because one of our primary goals was to make the measuring method as cost-effective as possible, we used high-power light emitting diodes instead of more expensive lasers. The use of LEDs, however, limits the maximum output power which can be extracted to illuminate the tissue. To meet these requirements, we improved methods of emitting light sufficiently deep into tissue. We also show how to measure NIR light of a very small power level that scatters from the tissue in the MRI environment, which is characterized by strong electromagnetic interference. In this paper, we present the implemented instrumentation and measuring method and report on test measurements conducted during MRI scanning. These measurements were performed in MRI operating rooms housing 1.5 Tesla-strength closed MRI scanners (manufactured by GE) in the Dept. of Diagnostic Radiology at the Oulu University Hospital.

Conceptual design of a cryogen-free μMRI device

NASA Astrophysics Data System (ADS)

Authelet, G.; Poirier-Quinot, M.; Ginefri, J.-C.; Bonelli, A.; Baudouy, B.

2017-12-01

To perform Micro Magnetic Resonance Imaging (mMRI) analysis on small regions such as skins, articulations or small animals, the required spatial resolution implies to dramatically improve the sensitivity of the detection. One way to go is to use small radio-frequency superconducting coil that allow, among others, increasing significantly the signal-to-noise ratio. The RF probe, constituted of an optimized YBaCuO film coil cooled below nitrogen temperature, must be located no further than few millimeters from the biological region to be imaged in a clinical MRI magnet. To fulfill the medical environment and constraints, a cryogen-free cooling scheme has been developed to maintain the superconducting coil at the working temperature. The cryogenic design is based on a pulse tube cryocooler and solid thermal links inserted in a non-magnetic cryostat to avoid creating any electromagnetic perturbations to the MRI magnet and the measurements. We report here the conceptual design of the cryogenic system with the required thermal performances, the corresponding layout and architecture of the system as well as the main technical challenges met for the construction.

Development of Ferrite-Based Temperature Sensors for Magnetic Resonance Imaging: A Study of Cu1 -xZnxFe2O4

NASA Astrophysics Data System (ADS)

Alghamdi, N. A.; Hankiewicz, J. H.; Anderson, N. R.; Stupic, K. F.; Camley, R. E.; Przybylski, M.; Żukrowski, J.; Celinski, Z.

2018-05-01

We investigate the use of Cu1 -xZnxFe2O4 ferrites (0.60

Parallel transmit excitation at 1.5 T based on the minimization of a driving function for device heating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gudino, N., E-mail: natalia.gudino@nih.gov; Sonmez, M.; Nielles-Vallespin, S.

2015-01-15

Purpose: To provide a rapid method to reduce the radiofrequency (RF) E-field coupling and consequent heating in long conductors in an interventional MRI (iMRI) setup. Methods: A driving function for device heating (W) was defined as the integration of the E-field along the direction of the wire and calculated through a quasistatic approximation. Based on this function, the phases of four independently controlled transmit channels were dynamically changed in a 1.5 T MRI scanner. During the different excitation configurations, the RF induced heating in a nitinol wire immersed in a saline phantom was measured by fiber-optic temperature sensing. Additionally, amore » minimization of W as a function of phase and amplitude values of the different channels and constrained by the homogeneity of the RF excitation field (B{sub 1}) over a region of interest was proposed and its results tested on the benchtop. To analyze the validity of the proposed method, using a model of the array and phantom setup tested in the scanner, RF fields and SAR maps were calculated through finite-difference time-domain (FDTD) simulations. In addition to phantom experiments, RF induced heating of an active guidewire inserted in a swine was also evaluated. Results: In the phantom experiment, heating at the tip of the device was reduced by 92% when replacing the body coil by an optimized parallel transmit excitation with same nominal flip angle. In the benchtop, up to 90% heating reduction was measured when implementing the constrained minimization algorithm with the additional degree of freedom given by independent amplitude control. The computation of the optimum phase and amplitude values was executed in just 12 s using a standard CPU. The results of the FDTD simulations showed similar trend of the local SAR at the tip of the wire and measured temperature as well as to a quadratic function of W, confirming the validity of the quasistatic approach for the presented problem at 64 MHz. Imaging and heating reduction of the guidewire were successfully performed in vivo with the proposed hardware and phase control. Conclusions: Phantom and in vivo data demonstrated that additional degrees of freedom in a parallel transmission system can be used to control RF induced heating in long conductors. A novel constrained optimization approach to reduce device heating was also presented that can be run in just few seconds and therefore could be added to an iMRI protocol to improve RF safety.« less

Finite volume analysis of temperature effects induced by active MRI implants with cylindrical symmetry: 1. Properly working devices.

PubMed

Busch, Martin H J; Vollmann, Wolfgang; Schnorr, Jörg; Grönemeyer, Dietrich H W

2005-04-08

Active Magnetic Resonance Imaging implants are constructed as resonators tuned to the Larmor frequency of a magnetic resonance system with a specific field strength. The resonating circuit may be embedded into or added to the normal metallic implant structure. The resonators build inductively coupled wireless transmit and receive coils and can amplify the signal, normally decreased by eddy currents, inside metallic structures without affecting the rest of the spin ensemble. During magnetic resonance imaging the resonators generate heat, which is additional to the usual one described by the specific absorption rate. This induces temperature increases of the tissue around the circuit paths and inside the lumen of an active implant and may negatively influence patient safety. This investigation provides an overview of the supplementary power absorbed by active implants with a cylindrical geometry, corresponding to vessel implants such as stents, stent grafts or vena cava filters. The knowledge of the overall absorbed power is used in a finite volume analysis to estimate temperature maps around different implant structures inside homogeneous tissue under worst-case assumptions. The "worst-case scenario" assumes thermal heat conduction without blood perfusion inside the tissue around the implant and mostly without any cooling due to blood flow inside vessels. The additional power loss of a resonator is proportional to the volume and the quality factor, as well as the field strength of the MRI system and the specific absorption rate of the applied sequence. For properly working devices the finite volume analysis showed only tolerable heating during MRI investigations in most cases. Only resonators transforming a few hundred mW into heat may reach temperature increases over 5 K. This requires resonators with volumes of several ten cubic centimeters, short inductor circuit paths with only a few 10 cm and a quality factor above ten. Using MR sequences, for which the MRI system manufacturer declares the highest specific absorption rate of 4 W/kg, vascular implants with a realistic construction, size and quality factor do not show temperature increases over a critical value of 5 K. The results show dangerous heating for the assumed "worst-case scenario" only for constructions not acceptable for vascular implants. Realistic devices are safe with respect to temperature increases. However, this investigation discusses only properly working devices. Ruptures or partial ruptures of the wires carrying the electric current of the resonance circuits or other defects can set up a power source inside an extremely small volume. The temperature maps around such possible "hot spots" should be analyzed in an additional investigation.

In Vitro Assessment of Spray Deposition Patterns in a Pediatric (12 Year-Old) Nasal Cavity Model.

PubMed

Sawant, Namita; Donovan, Maureen D

2018-03-26

Nasal sprays available for the treatment of cold and allergy symptoms currently use identical formulations and devices for adults as well as for children. Due to the obvious differences between the nasal airway dimensions of a child and those of an adult, the performance of nasal sprays in children was evaluated. Deposition patterns of nasal sprays administered to children were tested using a nasal cast based on MRI images obtained from a 12 year old child's nasal cavity. Test formulations emitting a range of spray patterns were investigated by actuating the device into the pediatric nasal cast under controlled conditions. The results showed that the nasal sprays impacted in the anterior region of the 12 year old child's nasal cavity, and only limited spray entered the turbinate region - the effect site for most topical drugs and the primary absorptive region for systemically absorbed drugs. Differences in deposition patterns following the administration of nasal sprays to adults and children may lead to differences in efficacy between these populations. Greater anterior deposition in children may result in decreased effectiveness, greater anterior dosage form loss, and the increased potential for patient non-compliance.

Improved accuracy and precision of tracer kinetic parameters by joint fitting to variable flip angle and dynamic contrast enhanced MRI data.

PubMed

Dickie, Ben R; Banerji, Anita; Kershaw, Lucy E; McPartlin, Andrew; Choudhury, Ananya; West, Catharine M; Rose, Chris J

2016-10-01

To improve the accuracy and precision of tracer kinetic model parameter estimates for use in dynamic contrast enhanced (DCE) MRI studies of solid tumors. Quantitative DCE-MRI requires an estimate of precontrast T1 , which is obtained prior to fitting a tracer kinetic model. As T1 mapping and tracer kinetic signal models are both a function of precontrast T1 it was hypothesized that its joint estimation would improve the accuracy and precision of both precontrast T1 and tracer kinetic model parameters. Accuracy and/or precision of two-compartment exchange model (2CXM) parameters were evaluated for standard and joint fitting methods in well-controlled synthetic data and for 36 bladder cancer patients. Methods were compared under a number of experimental conditions. In synthetic data, joint estimation led to statistically significant improvements in the accuracy of estimated parameters in 30 of 42 conditions (improvements between 1.8% and 49%). Reduced accuracy was observed in 7 of the remaining 12 conditions. Significant improvements in precision were observed in 35 of 42 conditions (between 4.7% and 50%). In clinical data, significant improvements in precision were observed in 18 of 21 conditions (between 4.6% and 38%). Accuracy and precision of DCE-MRI parameter estimates are improved when signal models are fit jointly rather than sequentially. Magn Reson Med 76:1270-1281, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Endometrial stromal sarcoma mimicking submucosal myoma protruding to the vagina: MRI findings.

PubMed

Chien, J C W; Hsieh, S C; Lee, R C; Chen, C Y; Cheng, C J; Chan, W P

2005-01-01

A 46-year-old woman complained of persistent abnormal vaginal bleeding over ten days. Her intrauterine device had been removed two years before. Soon after, she suffered from menorrhagia and metrorrhagia. An incidental finding of severe anemia was also noted. In this admission, our initial T2-weighted magnetic resonance imaging (MRI) revealed a well-demarcated mass predominantly in the uterine cavity. The mass was depicted by an isointense signal relative to the myometrium on T1-weighted images, high signal intensity on T2-weighted images, and slightly heterogeneous enhancement on post-contrast images. The patient refused surgery. After two years, follow-up MRI showed a pedunculated mass protruding into the upper third of the vagina with a stalk connecting to the posterior wall of the uterine cavity, simulating submucosal myoma. Histological diagnosis was compatible with low-grade endometrial stromal sarcoma.

CT and MRI slice separation evaluation by LabView developed software.

PubMed

Acri, Giuseppe; Testagrossa, Barbara; Sestito, Angela; Bonanno, Lilla; Vermiglio, Giuseppe

2018-02-01

The efficient use of Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) equipment necessitates establishing adequate quality-control (QC) procedures. In particular, the accuracy of slice separation, during multislices acquisition, requires scan exploration of phantoms containing test objects. To simplify such procedures, a novel phantom and a computerised LabView-based procedure have been devised, enabling determination the midpoint of full width at half maximum (FWHM) in real time while the distance from the profile midpoint of two progressive images is evaluated and measured. The results were compared with those obtained by processing the same phantom images with commercial software. To validate the proposed methodology the Fisher test was conducted on the resulting data sets. In all cases, there was no statistically significant variation between the commercial procedure and the LabView one, which can be used on any CT and MRI diagnostic devices. Copyright © 2017. Published by Elsevier GmbH.

Inflection Points in Magnetic Resonance Imaging Technology-35 Years of Collaborative Research and Development.

PubMed

Wood, Michael L; Griswold, Mark A; Henkelman, Mark; Hennig, Jürgen

2015-09-01

The technology for clinical magnetic resonance imaging (MRI) has advanced with remarkable speed and in such a manner reflecting the influence of 3 forces-collaboration between disciplines, collaboration between academia and industry, and the enabling of software applications by hardware. The forces are evident in the key developments from the past and emerging trends for the future highlighted in this review article. These developments are associated with MRI system attributes, such as wider, shorter, and stronger magnets; specialty magnets and hybrid devices; k space; and the notion that magnetic field gradients perform a Fourier transform on the spatial distribution of magnetization, phased-array coils and parallel imaging, the user interface, the wide range of contrast possible, and applications that exploit motion-induced phase shifts. An attempt is made to show connections between these developments and how the 3 forces mentioned previously will continue to shape the technology used so productively in clinical MRI.

Analysis of a simulation algorithm for direct brain drug delivery

PubMed Central

Rosenbluth, Kathryn Hammond; Eschermann, Jan Felix; Mittermeyer, Gabriele; Thomson, Rowena; Mittermeyer, Stephan; Bankiewicz, Krystof S.

2011-01-01

Convection enhanced delivery (CED) achieves targeted delivery of drugs with a pressure-driven infusion through a cannula placed stereotactically in the brain. This technique bypasses the blood brain barrier and gives precise distributions of drugs, minimizing off-target effects of compounds such as viral vectors for gene therapy or toxic chemotherapy agents. The exact distribution is affected by the cannula positioning, flow rate and underlying tissue structure. This study presents an analysis of a simulation algorithm for predicting the distribution using baseline MRI images acquired prior to inserting the cannula. The MRI images included diffusion tensor imaging (DTI) to estimate the tissue properties. The algorithm was adapted for the devices and protocols identified for upcoming trials and validated with direct MRI visualization of Gadolinium in 20 infusions in non-human primates. We found strong agreement between the size and location of the simulated and gadolinium volumes, demonstrating the clinical utility of this surgical planning algorithm. PMID:21945468

MR-based real time path planning for cardiac operations with transapical access.

PubMed

Yeniaras, Erol; Navkar, Nikhil V; Sonmez, Ahmet E; Shah, Dipan J; Deng, Zhigang; Tsekos, Nikolaos V

2011-01-01

Minimally invasive surgeries (MIS) have been perpetually evolving due to their potential high impact on improving patient management and overall cost effectiveness. Currently, MIS are further strengthened by the incorporation of magnetic resonance imaging (MRI) for amended visualization and high precision. Motivated by the fact that real-time MRI is emerging as a feasible modality especially for guiding interventions and surgeries in the beating heart; in this paper we introduce a real-time path planning algorithm for intracardiac procedures. Our approach creates a volumetric safety zone inside a beating heart and updates it on-the-fly using real-time MRI during the deployment of a robotic device. In order to prove the concept and assess the feasibility of the introduced method, a realistic operational scenario of transapical aortic valve replacement in a beating heart is chosen as the virtual case study.

Length matters: Improved high field EEG-fMRI recordings using shorter EEG cables.

PubMed

Assecondi, Sara; Lavallee, Christina; Ferrari, Paolo; Jovicich, Jorge

2016-08-30

The use of concurrent EEG-fMRI recordings has increased in recent years, allowing new avenues of medical and cognitive neuroscience research; however, currently used setups present problems with data quality and reproducibility. We propose a compact experimental setup for concurrent EEG-fMRI at 4T and compare it to a more standard reference setup. The compact setup uses short EEG cables connecting to the amplifiers, which are placed right at the back of the head RF coil on a form-fitting extension force-locked to the patient MR bed. We compare the two setups in terms of sensitivity to MR-room environmental noise, interferences between measuring devices (EEG or fMRI), and sensitivity to functional responses in a visual stimulation paradigm. The compact setup reduces the system sensitivity to both external noise and MR-induced artefacts by at least 60%, with negligible EEG noise induced from the mechanical vibrations of the cryogenic cooling compression pump. The compact setup improved EEG data quality and the overall performance of MR-artifact correction techniques. Both setups were similar in terms of the fMRI data, with higher reproducibility for cable placement within the scanner in the compact setup. This improved compact setup may be relevant to MR laboratories interested in reducing the sensitivity of their EEG-fMRI experimental setup to external noise sources, setting up an EEG-fMRI workplace for the first time, or for creating a more reproducible configuration of equipment and cables. Implications for safety and ergonomics are discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

3D printing of MRI compatible components: why every MRI research group should have a low-budget 3D printer.

PubMed

Herrmann, Karl-Heinz; Gärtner, Clemens; Güllmar, Daniel; Krämer, Martin; Reichenbach, Jürgen R

2014-10-01

To evaluate low budget 3D printing technology to create MRI compatible components. A 3D printer is used to create customized MRI compatible components, a loop-coil platform and a multipart mouse fixation. The mouse fixation is custom fit for a dedicated coil and facilitates head fixation with bite bar, anesthetic gas supply and biomonitoring sensors. The mouse fixation was tested in a clinical 3T scanner. All parts were successfully printed and proved MR compatible. Both design and printing were accomplished within a few days and the final print results were functional with well defined details and accurate dimensions (Δ<0.4mm). MR images of the mouse head clearly showed reduced motion artifacts, ghosting and signal loss when using the fixation. We have demonstrated that a low budget 3D printer can be used to quickly progress from a concept to a functional device at very low production cost. While 3D printing technology does impose some restrictions on model geometry, additive printing technology can create objects with complex internal structures that can otherwise not be created by using lathe technology. Thus, we consider a 3D printer a valuable asset for MRI research groups. Copyright © 2014 IPEM. Published by Elsevier Ltd. All rights reserved.

Image Quality of Cardiac Magnetic Resonance Imaging in Patients With an Implantable Cardioverter Defibrillator System Designed for the Magnetic Resonance Imaging Environment.

PubMed

Schwitter, Juerg; Gold, Michael R; Al Fagih, Ahmed; Lee, Sung; Peterson, Michael; Ciuffo, Allen; Zhang, Yan; Kristiansen, Nina; Kanal, Emanuel; Sommer, Torsten

2016-05-01

Recently, magnetic resonance (MR)-conditional implantable cardioverter defibrillator (ICD) systems have become available. However, associated cardiac MR image (MRI) quality is unknown. The goal was to evaluate the image quality performance of various cardiac MR sequences in a multicenter trial of patients implanted with an MR-conditional ICD system. The Evera-MRI trial enrolled 275 patients in 42 centers worldwide. There were 263 patients implanted with an Evera-MRI single- or dual-chamber ICD and randomized to controls (n=88) and MRI (n=175), 156 of whom underwent a protocol-required MRI (9-12 weeks post implant). Steady-state-free-precession (SSFP) and fast-gradient-echo (FGE) sequences were acquired in short-axis and horizontal long-axis orientations. Qualitative and quantitative assessment of image quality was performed by using a 7-point scale (grades 1-3: good quality, grades 6-7: nondiagnostic) and measuring ICD- and lead-related artifact size. Good to moderate image quality (grades 1-5) was obtained in 53% and 74% of SSFP and FGE acquisitions, respectively, covering the left ventricle, and in 69% and 84%, respectively, covering the right ventricle. Odds for better image quality were greater for right ventricle versus left ventricle (odds ratio, 1.8; 95% confidence interval, 1.5-2.2; P<0.0001) and greater for FGE versus SSFP (odds ratio, 3.5; 95% confidence interval, 2.5-4.8; P<0.0001). Compared with SSFP, ICD-related artifacts on FGE were smaller (141±65 versus 75±57 mm, respectively; P<0.0001). Lead artifacts were much smaller than ICD artifacts (P<0.0001). FGE yields good to moderate quality in 74% of left ventricle and 84% of right ventricle acquisitions and performs better than SSFP in patients with an MRI-conditional ICD system. In these patients, cardiac MRI can offer diagnostic information in most cases. URL: http://www.clinicaltrials.gov. Unique identifier: NCT02117414. © 2016 American Heart Association, Inc.

MRI as a tool for evaluation of oral controlled release dosage forms.

PubMed

Dorożyński, Przemysław P; Kulinowski, Piotr; Młynarczyk, Anna; Stanisz, Greg J

2012-02-01

The magnetic resonance imaging (MRI) studies of controlled-release (CR) dosage forms can be roughly divided into two groups. The first comprises studies performed in static conditions (small solvent volumes and ambient temperature). Such studies have provided insight into molecular phenomena in hydrating polymeric matrices. The second group covers research performed in dynamic conditions (medium flow or stirring) related to drug dissolution. An important issue is supplementation of the MRI results with data obtained by complementary techniques, such as X-ray microtomography (μCT). As we discuss here, an understanding of the mechanism underlying the release of the drug from the dosage form will lead to the development of detailed, molecularly defined, CR dosage forms. Copyright © 2011 Elsevier Ltd. All rights reserved.

Prenatal magnetic resonance imaging: towards optimized patient information.

PubMed

Leithner, K; Pörnbacher, S; Assem-Hilger, E; Krampl-Bettelheim, E; Prayer, D

2009-08-01

To investigate the perception of fetal magnetic resonance imaging (MRI) by women confronted with the necessity of a targeted prenatal examination because of suspicion of an abnormality, in order to develop a pre-scan information leaflet tailored to the information requirements of these women. Sixty-two women were assessed by qualitative interview immediately before and after scanning. Data were analyzed by means of a qualitative content analysis. The transcribed interviews were coded within established categories, including knowledge of the purpose of the exam, understanding of the procedure, expectation of the baby's reaction, satisfaction with pre-information, experience of fetal MRI, distressing conditions during scanning, anxiety and suggestions for improvement of the scanning procedure. Pre-scan interviews indicated 66% of our sample to be well-informed about the purpose of fetal MRI. A realistic, detailed description of the examination was given by 37%. Only 32% expected the scanning to be safe for their baby. Despite the overall good tolerance of fetal MRI (63%), post-scan interviews revealed that 58% of women had experienced anxiety during MRI, which was partly due to the fearful perception of intensified fetal body movements during scanning. The quality of the pre-information leaflet was rated as sufficiently informative by 68% of the women. Suggestions for improvement were centered on physical conditions, the presence of the partner during scanning, and the availability of pre-scan briefings. Based on women's needs, detailed information about the fetal MRI procedure should be provided, containing clear-cut explanations about the purpose, course, method and possible distressing conditions. A leaflet describing these details should be given to women by the referring physician well in advance of the examination, and the woman given the opportunity to discuss unclear points.

Validation of Shared and Specific Independent Component Analysis (SSICA) for Between-Group Comparisons in fMRI

PubMed Central

Maneshi, Mona; Vahdat, Shahabeddin; Gotman, Jean; Grova, Christophe

2016-01-01

Independent component analysis (ICA) has been widely used to study functional magnetic resonance imaging (fMRI) connectivity. However, the application of ICA in multi-group designs is not straightforward. We have recently developed a new method named “shared and specific independent component analysis” (SSICA) to perform between-group comparisons in the ICA framework. SSICA is sensitive to extract those components which represent a significant difference in functional connectivity between groups or conditions, i.e., components that could be considered “specific” for a group or condition. Here, we investigated the performance of SSICA on realistic simulations, and task fMRI data and compared the results with one of the state-of-the-art group ICA approaches to infer between-group differences. We examined SSICA robustness with respect to the number of allowable extracted specific components and between-group orthogonality assumptions. Furthermore, we proposed a modified formulation of the back-reconstruction method to generate group-level t-statistics maps based on SSICA results. We also evaluated the consistency and specificity of the extracted specific components by SSICA. The results on realistic simulated and real fMRI data showed that SSICA outperforms the regular group ICA approach in terms of reconstruction and classification performance. We demonstrated that SSICA is a powerful data-driven approach to detect patterns of differences in functional connectivity across groups/conditions, particularly in model-free designs such as resting-state fMRI. Our findings in task fMRI show that SSICA confirms results of the general linear model (GLM) analysis and when combined with clustering analysis, it complements GLM findings by providing additional information regarding the reliability and specificity of networks. PMID:27729843

Volume estimation of brain abnormalities in MRI data

NASA Astrophysics Data System (ADS)

Suprijadi, Pratama, S. H.; Haryanto, F.

2014-02-01

The abnormality of brain tissue always becomes a crucial issue in medical field. This medical condition can be recognized through segmentation of certain region from medical images obtained from MRI dataset. Image processing is one of computational methods which very helpful to analyze the MRI data. In this study, combination of segmentation and rendering image were used to isolate tumor and stroke. Two methods of thresholding were employed to segment the abnormality occurrence, followed by filtering to reduce non-abnormality area. Each MRI image is labeled and then used for volume estimations of tumor and stroke-attacked area. The algorithms are shown to be successful in isolating tumor and stroke in MRI images, based on thresholding parameter and stated detection accuracy.

The role of fMRI in drug development

PubMed Central

Carmichael, Owen; Schwarz, Adam J.; Chatham, Christopher H.; Scott, David; Turner, Jessica A.; Upadhyay, Jaymin; Coimbra, Alexandre; Goodman, James A.; Baumgartner, Richard; English, Brett A.; Apolzan, John W.; Shankapal, Preetham; Hawkins, Keely R.

2017-01-01

Functional magnetic resonance imaging (fMRI) has been known for over a decade to have the potential to greatly enhance the process of developing novel therapeutic drugs for prevalent health conditions. However, the use of fMRI in drug development continues to be relatively limited because of a variety of technical, biological, and strategic barriers that continue to limit progress. Here, we briefly review the roles that fMRI can have in the drug development process and the requirements it must meet to be useful in this setting. We then provide an update on our current understanding of the strengths and limitations of fMRI as a tool for drug developers and recommend activities to enhance its utility. PMID:29154758

Experimental evaluation of ballistic hazards in imaging diagnostic center.

PubMed

Karpowicz, Jolanta; Gryz, Krzysztof

2013-04-01

Serious hazards for human health and life and devices in close proximity to the magnetic resonance scanners (MRI scanners) include the effects of being hit by ferromagnetic objects attracted by static magnetic field (SMF) produced by scanner magnet - the so-called ballistic hazards classified among indirect electromagnetic hazards. International safety guidelines and technical literature specify different SMF threshold values regarding ballistic hazards - e.g. 3 mT (directive 2004/40/EC, EN 60601-2-33), and 30 mT (BMAS 2009, directive proposal 2011). Investigations presented in this article were performed in order to experimentally verify SMF threshold for ballistic hazards near MRI scanners used in Poland. Investigations were performed with the use of a laboratory source of SMF (0-30 mT) and MRI scanners of various types. The levels of SMF in which metal objects of various shapes and 0.4-500 g mass are moved by the field influence were investigated. The distance from the MRI scanners (0.2-3T) where hazards may occur were also investigated. Objects investigated under laboratory conditions were moved by SMF of 2.2-15 mT magnetic flux density when they were freely suspended, but were moved by the SMF of 5.6-22 mT when they were placed on a smooth surface. Investigated objects were moved in fields of 3.5-40 mT by MRI scanners. Distances from scanner magnet cover, where ballistic hazards might occur are: up to 0.5 m for 0.2-0.3T scanners; up to 1.3 m for 0.5T scanners; up to 2.0 m for 1.5T scanners and up to 2.5 m for 3T scanners (at the front and back of the magnet). It was shown that SMF of 3 mT magnetic flux density should be taken as the threshold for ballistic hazards. Such level is compatible with SMF limit value regarding occupational safety and health-protected areas/zones, where according to the Polish labor law the procedures of work environment inspection and prevention measures regarding indirect electromagnetic hazards should be applied. Presented results do not support the increase up to 30 mT of the SMF limit for protected area.

Nanotechnology and cancer: improving real-time monitoring and staging of bladder cancer with multimodal mesoporous silica nanoparticles.

PubMed

Sweeney, Sean K; Luo, Yi; O'Donnell, Michael A; Assouline, Jose

Despite being one of the most common cancers, bladder cancer is largely inefficiently and inaccurately staged and monitored. Current imaging methods detect cancer only when it has reached "visible" size and has significantly disrupted the structure of the organ. By that time, thousands of cells will have proliferated and perhaps metastasized. Repeated biopsies and scans are necessary to determine the effect of therapy on cancer growth. In this report, we describe a novel approach based on multimodal nanoparticle contrast agent technology and its application to a preclinical animal model of bladder cancer. The innovation relies on the engineering core of mesoporous silica with specific scanning contrast properties and surface modification that include fluorescence and magnetic resonance imaging (MRI) contrast. The overall dimensions of the nano-device are preset at 80-180 nm, depending on composition with a pore size of 2 nm. To facilitate and expedite discoveries, we combined a well-known model of bladder cancer and our novel technology. We exposed nanoparticles to MB49 murine bladder cancer cells in vitro and found that 70 % of the cells were labeled by nanoparticles as measured by flow cytometry. The in vivo mouse model for bladder cancer is particularly well suited for T1- and T2-weighted MRI. Under our experimental conditions, we demonstrate that the nanoparticles considerably improve tumor definition in terms of volumetric, intensity and structural characteristics. Important bladder tumor parameters can be ascertained, non-invasively, repetitively, and with great accuracy. Furthermore, since the particles are not biodegradable, repetitive injection is not required. This feature allows follow-up diagnostic evaluations during cancer treatment. Changes in MRI signals show that in situ uptake of free particles has predilection to tumor cells relative to normal bladder epithelium. The particle distribution within the tumors was corroborated by fluorescent microscopy of sections of excised bladders. In addition, MRI imaging revealed fibrous finger-like projections into the tumors where particles insinuated themselves deeply. This morphological characteristic was confirmed by fluorescence microscopy. These findings may present new options for therapeutic intervention. Ultimately, the combination of real-time and repeated MRI evaluation of the tumors enhanced by nanoparticle contrast may have the potential for translation into human clinical studies for tumor staging, therapeutic monitoring, and drug delivery.

Nanoscale NMR spectroscopy and imaging of multiple nuclear species.

PubMed

DeVience, Stephen J; Pham, Linh M; Lovchinsky, Igor; Sushkov, Alexander O; Bar-Gill, Nir; Belthangady, Chinmay; Casola, Francesco; Corbett, Madeleine; Zhang, Huiliang; Lukin, Mikhail; Park, Hongkun; Yacoby, Amir; Walsworth, Ronald L

2015-02-01

Nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) provide non-invasive information about multiple nuclear species in bulk matter, with wide-ranging applications from basic physics and chemistry to biomedical imaging. However, the spatial resolution of conventional NMR and MRI is limited to several micrometres even at large magnetic fields (>1 T), which is inadequate for many frontier scientific applications such as single-molecule NMR spectroscopy and in vivo MRI of individual biological cells. A promising approach for nanoscale NMR and MRI exploits optical measurements of nitrogen-vacancy (NV) colour centres in diamond, which provide a combination of magnetic field sensitivity and nanoscale spatial resolution unmatched by any existing technology, while operating under ambient conditions in a robust, solid-state system. Recently, single, shallow NV centres were used to demonstrate NMR of nanoscale ensembles of proton spins, consisting of a statistical polarization equivalent to ∼100-1,000 spins in uniform samples covering the surface of a bulk diamond chip. Here, we realize nanoscale NMR spectroscopy and MRI of multiple nuclear species ((1)H, (19)F, (31)P) in non-uniform (spatially structured) samples under ambient conditions and at moderate magnetic fields (∼20 mT) using two complementary sensor modalities.

MRI findings in 6 cases of children by inadvertent ingestion of diphenoxylate-atropine.

PubMed

Xiao, Lianxiang; Lin, Xiangtao; Cao, Jinfeng; Wang, Xueyu; Wu, Lebin

2011-09-01

Compound diphenoxylate (diphenoxylate-atropine) poisoning can cause toxic encephalopathy in children, and magnetic resonance imaging (MRI) of the brain in this condition has not been reported. This study is to analyze brain MRI findings and to investigate the relations between MRI features and possible pathophysiological changes in children. Six children accidentally swallowed compound diphenoxylate, 4 males, 2 females, aged 20-46 months, average 33 months. Quantity of ingested diphenoxylate-atropine was from 6 to 30 tablets, each tablet contains diphenoxylate 2.5mg and atropine 0.025 mg. These patients were referred to our hospital within 24h after diphenoxylate-atropine ingestion, and underwent brain MRI scan within 24-72 h after emergency treatment. The characteristics of conventional MRI were analyzed. These pediatric patients had various symptoms of opioid intoxication and atropine toxicity. Brain MRI showed abnormal low signal intensity on T1-weighted images (T1WI) and abnormal high signal intensity on T2-weighted images (T2WI) and fluid-attenuated inversion recovery (FLAIR) imaging in bilateral in all cases; abnormal high signal intensity on T1WI, T2WI and FLAIR in 4 cases. Encephalomalacia was observed in 3 cases during follow-up. In the early stage of compound diphenoxylate poisoning in children, multiple extensive edema-necrosis and hemorrhagic-necrosis focus were observed in basic nucleus, pallium and cerebellum, these resulted in the corresponding brain dysfunction with encephalomalacia. MRI scan in the early stage in this condition may provide evidences of brain impairment, and is beneficial for the early diagnosis, treatment and prognosis assessment. Crown Copyright © 2010. Published by Elsevier Ireland Ltd. All rights reserved.

Reproducibility and Temporal Structure in Weekly Resting-State fMRI over a Period of 3.5 Years

PubMed Central

Choe, Ann S.; Jones, Craig K.; Joel, Suresh E.; Muschelli, John; Belegu, Visar; Caffo, Brian S.; Lindquist, Martin A.; van Zijl, Peter C. M.; Pekar, James J.

2015-01-01

Resting-state functional MRI (rs-fMRI) permits study of the brain’s functional networks without requiring participants to perform tasks. Robust changes in such resting state networks (RSNs) have been observed in neurologic disorders, and rs-fMRI outcome measures are candidate biomarkers for monitoring clinical trials, including trials of extended therapeutic interventions for rehabilitation of patients with chronic conditions. In this study, we aim to present a unique longitudinal dataset reporting on a healthy adult subject scanned weekly over 3.5 years and identify rs-fMRI outcome measures appropriate for clinical trials. Accordingly, we assessed the reproducibility, and characterized the temporal structure of, rs-fMRI outcome measures derived using independent component analysis (ICA). Data was compared to a 21-person dataset acquired on the same scanner in order to confirm that the values of the single-subject RSN measures were within the expected range as assessed from the multi-participant dataset. Fourteen RSNs were identified, and the inter-session reproducibility of outcome measures—network spatial map, temporal signal fluctuation magnitude, and between-network connectivity (BNC)–was high, with executive RSNs showing the highest reproducibility. Analysis of the weekly outcome measures also showed that many rs-fMRI outcome measures had a significant linear trend, annual periodicity, and persistence. Such temporal structure was most prominent in spatial map similarity, and least prominent in BNC. High reproducibility supports the candidacy of rs-fMRI outcome measures as biomarkers, but the presence of significant temporal structure needs to be taken into account when such outcome measures are considered as biomarkers for rehabilitation-style therapeutic interventions in chronic conditions. PMID:26517540

fMRI during natural sleep as a method to study brain function during early childhood.

PubMed

Redcay, Elizabeth; Kennedy, Daniel P; Courchesne, Eric

2007-12-01

Many techniques to study early functional brain development lack the whole-brain spatial resolution that is available with fMRI. We utilized a relatively novel method in which fMRI data were collected from children during natural sleep. Stimulus-evoked responses to auditory and visual stimuli as well as stimulus-independent functional networks were examined in typically developing 2-4-year-old children. Reliable fMRI data were collected from 13 children during presentation of auditory stimuli (tones, vocal sounds, and nonvocal sounds) in a block design. Twelve children were presented with visual flashing lights at 2.5 Hz. When analyses combined all three types of auditory stimulus conditions as compared to rest, activation included bilateral superior temporal gyri/sulci (STG/S) and right cerebellum. Direct comparisons between conditions revealed significantly greater responses to nonvocal sounds and tones than to vocal sounds in a number of brain regions including superior temporal gyrus/sulcus, medial frontal cortex and right lateral cerebellum. The response to visual stimuli was localized to occipital cortex. Furthermore, stimulus-independent functional connectivity MRI analyses (fcMRI) revealed functional connectivity between STG and other temporal regions (including contralateral STG) and medial and lateral prefrontal regions. Functional connectivity with an occipital seed was localized to occipital and parietal cortex. In sum, 2-4 year olds showed a differential fMRI response both between stimulus modalities and between stimuli in the auditory modality. Furthermore, superior temporal regions showed functional connectivity with numerous higher-order regions during sleep. We conclude that the use of sleep fMRI may be a valuable tool for examining functional brain organization in young children.

The influence of FMRI lie detection evidence on juror decision-making.

PubMed

McCabe, David P; Castel, Alan D; Rhodes, Matthew G

2011-01-01

In the current study, we report on an experiment examining whether functional magnetic resonance imaging (fMRI) lie detection evidence would influence potential jurors' assessment of guilt in a criminal trial. Potential jurors (N = 330) read a vignette summarizing a trial, with some versions of the vignette including lie detection evidence indicating that the defendant was lying about having committed the crime. Lie detector evidence was based on evidence from the polygraph, fMRI (functional brain imaging), or thermal facial imaging. Results showed that fMRI lie detection evidence led to more guilty verdicts than lie detection evidence based on polygraph evidence, thermal facial imaging, or a control condition that did not include lie detection evidence. However, when the validity of the fMRI lie detection evidence was called into question on cross-examination, guilty verdicts were reduced to the level of the control condition. These results provide important information about the influence of lie detection evidence in legal settings. Copyright © 2011 John Wiley & Sons, Ltd.

The neural basis of parallel saccade programming: an fMRI study.

PubMed

Hu, Yanbo; Walker, Robin

2011-11-01

The neural basis of parallel saccade programming was examined in an event-related fMRI study using a variation of the double-step saccade paradigm. Two double-step conditions were used: one enabled the second saccade to be partially programmed in parallel with the first saccade while in a second condition both saccades had to be prepared serially. The intersaccadic interval, observed in the parallel programming (PP) condition, was significantly reduced compared with latency in the serial programming (SP) condition and also to the latency of single saccades in control conditions. The fMRI analysis revealed greater activity (BOLD response) in the frontal and parietal eye fields for the PP condition compared with the SP double-step condition and when compared with the single-saccade control conditions. By contrast, activity in the supplementary eye fields was greater for the double-step condition than the single-step condition but did not distinguish between the PP and SP requirements. The role of the frontal eye fields in PP may be related to the advanced temporal preparation and increased salience of the second saccade goal that may mediate activity in other downstream structures, such as the superior colliculus. The parietal lobes may be involved in the preparation for spatial remapping, which is required in double-step conditions. The supplementary eye fields appear to have a more general role in planning saccade sequences that may be related to error monitoring and the control over the execution of the correct sequence of responses.

The Visible Heart® project and free-access website 'Atlas of Human Cardiac Anatomy'.

PubMed

Iaizzo, Paul A

2016-12-01

Pre- and post-evaluations of implantable cardiac devices require innovative and critical testing in all phases of the design process. The Visible Heart ® Project was successfully launched in 1997 and 3 years later the Atlas of Human Cardiac Anatomy website was online. The Visible Heart ® methodologies and Atlas website can be used to better understand human cardiac anatomy, disease states and/or to improve cardiac device design throughout the development process. To date, Visible ® Heart methodologies have been used to reanimate 75 human hearts, all considered non-viable for transplantation. The Atlas is a unique free-access website featuring novel images of functional and fixed human cardiac anatomies from >400 human heart specimens. Furthermore, this website includes education tutorials on anatomy, physiology, congenital heart disease and various imaging modalities. For instance, the Device Tutorial provides examples of commonly deployed devices that were present at the time of in vitro reanimation or were subsequently delivered, including: leads, catheters, valves, annuloplasty rings, leadless pacemakers and stents. Another section of the website displays 3D models of vasculature, blood volumes, and/or tissue volumes reconstructed from computed tomography (CT) and magnetic resonance images (MRI) of various heart specimens. A new section allows the user to interact with various heart models. Visible Heart ® methodologies have enabled our laboratory to reanimate 75 human hearts and visualize functional cardiac anatomies and device/tissue interfaces. The website freely shares all images, video clips and CT/MRI DICOM files in honour of the generous gifts received from donors and their families. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For Permissions, please email: journals.permissions@oup.com.

Safety and performance of a novel embolic deflection device in patients undergoing transcatheter aortic valve replacement: results from the DEFLECT I study.

PubMed

Baumbach, Andreas; Mullen, Michael; Brickman, Adam M; Aggarwal, Suneil K; Pietras, Cody G; Forrest, John K; Hildick-Smith, David; Meller, Stephanie M; Gambone, Louise; den Heijer, Peter; Margolis, Pauliina; Voros, Szilard; Lansky, Alexandra J

2015-05-01

This study aimed to evaluate the safety and performance of the TriGuard™ Embolic Deflection Device (EDD), a nitinol mesh filter positioned in the aortic arch across all three major cerebral artery take-offs to deflect emboli away from the cerebral circulation, in patients undergoing transcatheter aortic valve replacement (TAVR). The prospective, multicentre DEFLECT I study (NCT01448421) enrolled 37 consecutive subjects undergoing TAVR with the TriGuard EDD. Subjects underwent clinical and cognitive follow-up to 30 days; cerebral diffusion-weighted magnetic resonance imaging (DW-MRI) was performed pre-procedure and at 4±2 days post procedure. The device performed as intended with successful cerebral coverage in 80% (28/35) of cases. The primary safety endpoint (in-hospital EDD device- or EDD procedure-related cardiovascular mortality, major stroke disability, life-threatening bleeding, distal embolisation, major vascular complications, or need for acute cardiac surgery) occurred in 8.1% of subjects (VARC-defined two life-threatening bleeds and one vascular complication). The presence of new cerebral ischaemic lesions on post-procedure DW-MRI (n=28) was similar to historical controls (82% vs. 76%, p=NS). However, an exploratory analysis found that per-patient total lesion volume was 34% lower than reported historical data (0.2 vs. 0.3 cm3), and 89% lower in patients with complete (n=17) versus incomplete (n=10) cerebral vessel coverage (0.05 vs. 0.45 cm3, p=0.016). Use of the first-generation TriGuard EDD during TAVR is safe, and device performance was successful in 80% of cases during the highest embolic-risk portions of the TAVR procedure. The potential of the TriGuard EDD to reduce total cerebral ischaemic burden merits further randomised investigation.

The Effects of Day-to-Day Variability of Physiological Data on Operator Functional State Classification

DTIC Science & Technology

2013-03-01

fMRI data (e.g. Kamitami & Tong, 2005). This approach has been remarkably successful in classifying mental workload in complex tasks (Berka, et al...1991). These previous studies relied upon spectral comparison rather than classification. In previous research examining the stability of fMRI ...chose to focus on electrophysiology, as the collection conditions may be more carefully controlled across days than fMRI and it is more amenable to

Structural Brain Atlases: Design, Rationale, and Applications in Normal and Pathological Cohorts

PubMed Central

Mandal, Pravat K.; Mahajan, Rashima; Dinov, Ivo D.

2015-01-01

Structural magnetic resonance imaging (MRI) provides anatomical information about the brain in healthy as well as in diseased conditions. On the other hand, functional MRI (fMRI) provides information on the brain activity during performance of a specific task. Analysis of fMRI data requires the registration of the data to a reference brain template in order to identify the activated brain regions. Brain templates also find application in other neuroimaging modalities, such as diffusion tensor imaging and multi-voxel spectroscopy. Further, there are certain differences (e.g., brain shape and size) in the brains of populations of different origin and during diseased conditions like in Alzheimer’s disease (AD), population and disease-specific brain templates may be considered crucial for accurate registration and subsequent analysis of fMRI as well as other neuroimaging data. This manuscript provides a comprehensive review of the history, construction and application of brain atlases. A chronological outline of the development of brain template design, starting from the Talairach and Tournoux atlas to the Chinese brain template (to date), along with their respective detailed construction protocols provides the backdrop to this manuscript. The manuscript also provides the automated workflow-based protocol for designing a population-specific brain atlas from structural MRI data using LONI Pipeline graphical workflow environment. We conclude by discussing the scope of brain templates as a research tool and their application in various neuroimaging modalities. PMID:22647262

Technical Note: Experimental results from a prototype high-field inline MRI-linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liney, G. P., E-mail: gary.liney@sswahs.nsw.gov.au

Purpose: The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid magnetic resonance imaging (MRI)-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-linac system. This work describes results from a prototype experimental system to demonstrate the feasibility of a high field inline MR-linac. Methods: The magnet is a 1.5 T MRI system (Sonata, Siemens Healthcare) was located in a purpose built radiofrequency (RF) cage enablingmore » shielding from and close proximity to a linear accelerator with inline (and future perpendicular) orientation. A portable linear accelerator (Linatron, Varian) was installed together with a multileaf collimator (Millennium, Varian) to provide dynamic field collimation and the whole assembly built onto a stainless-steel rail system. A series of MRI-linac experiments was performed to investigate (1) image quality with beam on measured using a macropodine (kangaroo) ex vivo phantom; (2) the noise as a function of beam state measured using a 6-channel surface coil array; and (3) electron contamination effects measured using Gafchromic film and an electronic portal imaging device (EPID). Results: (1) Image quality was unaffected by the radiation beam with the macropodine phantom image with the beam on being almost identical to the image with the beam off. (2) Noise measured with a surface RF coil produced a 25% elevation of background intensity when the radiation beam was on. (3) Film and EPID measurements demonstrated electron focusing occurring along the centerline of the magnet axis. Conclusions: A proof-of-concept high-field MRI-linac has been built and experimentally characterized. This system has allowed us to establish the efficacy of a high field inline MRI-linac and study a number of the technical challenges and solutions.« less

MRI Evaluation and Safety in the Developing Brain

PubMed Central

Tocchio, Shannon; Kline-Fath, Beth; Kanal, Emanuel; Schmithorst, Vincent J.; Panigrahy, Ashok

2015-01-01

Magnetic resonance imaging (MRI) evaluation of the developing brain has dramatically increased over the last decade. Faster acquisitions and the development of advanced MRI sequences such as magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), perfusion imaging, functional MR imaging (fMRI), and susceptibility weighted imaging (SWI), as well as the use of higher magnetic field strengths has made MRI an invaluable tool for detailed evaluation of the developing brain. This article will provide an overview of the use and challenges associated with 1.5T and 3T static magnetic fields for evaluation of the developing brain. This review will also summarize the advantages, clinical challenges and safety concerns specifically related to MRI in the fetus and newborn, including the implications of increased magnetic field strength, logistics related to transporting and monitoring of neonates during scanning, sedation considerations and a discussion of current technologies such as MRI-conditional neonatal incubators and dedicated small-foot print neonatal intensive care unit (NICU) scanners. PMID:25743582

MRI evaluation and safety in the developing brain.

PubMed

Tocchio, Shannon; Kline-Fath, Beth; Kanal, Emanuel; Schmithorst, Vincent J; Panigrahy, Ashok

2015-03-01

Magnetic resonance imaging (MRI) evaluation of the developing brain has dramatically increased over the last decade. Faster acquisitions and the development of advanced MRI sequences, such as magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), perfusion imaging, functional MR imaging (fMRI), and susceptibility-weighted imaging (SWI), as well as the use of higher magnetic field strengths has made MRI an invaluable tool for detailed evaluation of the developing brain. This article will provide an overview of the use and challenges associated with 1.5-T and 3-T static magnetic fields for evaluation of the developing brain. This review will also summarize the advantages, clinical challenges, and safety concerns specifically related to MRI in the fetus and newborn, including the implications of increased magnetic field strength, logistics related to transporting and monitoring of neonates during scanning, and sedation considerations, and a discussion of current technologies such as MRI conditional neonatal incubators and dedicated small-foot print neonatal intensive care unit (NICU) scanners. Copyright © 2015 Elsevier Inc. All rights reserved.

MRI abnormalities of peripheral nerve and muscle are common in amyotrophic lateral sclerosis and share features with multifocal motor neuropathy

PubMed Central

Staff, Nathan P.; Amrami, Kimberly K.; Howe, Benjamin M.

2015-01-01

Introduction MRI of peripheral nerve and muscle in patients with ALS may be performed to investigate alternative diagnoses including multifocal motor neuropathy (MMN). MRI findings of peripheral nerve and muscle are not well described in these conditions, making interpretation of results difficult. Methods We examined systematically the peripheral nerve and muscle MRI findings in patients with ALS (n=60) and MMN (n=8). Results In patients with ALS and MMN, abnormal MRIs were common (85% and 75%, respectively) but did not correlate with disease severity. Peripheral nerve MRI abnormalities were similar in frequency (ALS: 58% vs. MMN: 63%) with most changes being of mild-to-moderate severity. Muscle MRI changes were more common in ALS (57% vs. 33%), and no muscle atrophy was seen in patients with MMN. Discussion MRI abnormalities of peripheral nerve and muscle in ALS and MMN are common and share some features. PMID:25736373

Comparison of block and event-related experimental designs in diffusion-weighted functional MRI.

PubMed

Williams, Rebecca J; McMahon, Katie L; Hocking, Julia; Reutens, David C

2014-08-01

To compare diffusion-weighted functional magnetic resonance imaging (DfMRI), a novel alternative to the blood oxygenation level-dependent (BOLD) contrast, in a functional MRI experiment. Nine participants viewed contrast reversing (7.5 Hz) black-and-white checkerboard stimuli using block and event-related paradigms. DfMRI (b = 1800 mm/s(2)) and BOLD sequences were acquired. Four parameters describing the observed signal were assessed: percent signal change, spatial extent of the activation, the Euclidean distance between peak voxel locations, and the time-to-peak of the best fitting impulse response for different paradigms and sequences. The BOLD conditions showed a higher percent signal change relative to DfMRI; however, event-related DfMRI showed the strongest group activation (t = 21.23, P < 0.0005). Activation was more diffuse and spatially closer to the BOLD response for DfMRI when the block design was used. DfMRIevent showed the shortest TTP (4.4 ± 0.88 sec). The hemodynamic contribution to DfMRI may increase with the use of block designs. © 2013 Wiley Periodicals, Inc.

Technical Note: Quantitative dynamic contrast-enhanced MRI of a 3-dimensional artificial capillary network.

PubMed

Gaass, Thomas; Schneider, Moritz Jörg; Dietrich, Olaf; Ingrisch, Michael; Dinkel, Julien

2017-04-01

Variability across devices, patients, and time still hinders widespread recognition of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) as quantitative biomarker. The purpose of this work was to introduce and characterize a dedicated microchannel phantom as a model for quantitative DCE-MRI measurements. A perfusable, MR-compatible microchannel network was constructed on the basis of sacrificial melt-spun sugar fibers embedded in a block of epoxy resin. Structural analysis was performed on the basis of light microscopy images before DCE-MRI experiments. During dynamic acquisition the capillary network was perfused with a standard contrast agent injection system. Flow-dependency, as well as inter- and intrascanner reproducibility of the computed DCE parameters were evaluated using a 3.0 T whole-body MRI. Semi-quantitative and quantitative flow-related parameters exhibited the expected proportionality to the set flow rate (mean Pearson correlation coefficient: 0.991, P < 2.5e-5). The volume fraction was approximately independent from changes of the applied flow rate through the phantom. Repeatability and reproducibility experiments yielded maximum intrascanner coefficients of variation (CV) of 4.6% for quantitative parameters. All evaluated parameters were well in the range of known in vivo results for the applied flow rates. The constructed phantom enables reproducible, flow-dependent, contrast-enhanced MR measurements with the potential to facilitate standardization and comparability of DCE-MRI examinations. © 2017 American Association of Physicists in Medicine.

Radiological assessment of placement of the hysteroscopically inserted Essure permanent birth control device.

PubMed

Lorente Ramos, R M; Azpeitia Armán, J; Aparicio Rodríguez-Miñón, P; Salazar Arquero, F J; Albillos Merino, J C

2015-01-01

Essure is a permanent birth control device that is inserted through the cervix by hysteroscopy. The device is placed in the fallopian tubes, where it causes occlusion by stimulating fibrosis. Patients can be followed up with plain-film X-rays, hysterosalpingography, and ultrasonography, although the devices can also be identified incidentally on CT and MRI. The follow-up of Essure is based on checking the criteria for appropriate positioning and correct functioning (tubal occlusion) and on diagnosing complications. The most common complications are perforation, migration (toward the uterine or peritoneal cavity), and occlusion failure. In hysterosalpingography, vascular intravasation is the most common cause of diagnostic error. Radiologists need to know how to recognize the device on different imaging techniques, how to check that it is correctly placed and functioning, and how to diagnose complications. Copyright © 2014 SERAM. Published by Elsevier España, S.L.U. All rights reserved.

KneeTex: an ontology-driven system for information extraction from MRI reports.

PubMed

Spasić, Irena; Zhao, Bo; Jones, Christopher B; Button, Kate

2015-01-01

In the realm of knee pathology, magnetic resonance imaging (MRI) has the advantage of visualising all structures within the knee joint, which makes it a valuable tool for increasing diagnostic accuracy and planning surgical treatments. Therefore, clinical narratives found in MRI reports convey valuable diagnostic information. A range of studies have proven the feasibility of natural language processing for information extraction from clinical narratives. However, no study focused specifically on MRI reports in relation to knee pathology, possibly due to the complexity of knee anatomy and a wide range of conditions that may be associated with different anatomical entities. In this paper we describe KneeTex, an information extraction system that operates in this domain. As an ontology-driven information extraction system, KneeTex makes active use of an ontology to strongly guide and constrain text analysis. We used automatic term recognition to facilitate the development of a domain-specific ontology with sufficient detail and coverage for text mining applications. In combination with the ontology, high regularity of the sublanguage used in knee MRI reports allowed us to model its processing by a set of sophisticated lexico-semantic rules with minimal syntactic analysis. The main processing steps involve named entity recognition combined with coordination, enumeration, ambiguity and co-reference resolution, followed by text segmentation. Ontology-based semantic typing is then used to drive the template filling process. We adopted an existing ontology, TRAK (Taxonomy for RehAbilitation of Knee conditions), for use within KneeTex. The original TRAK ontology expanded from 1,292 concepts, 1,720 synonyms and 518 relationship instances to 1,621 concepts, 2,550 synonyms and 560 relationship instances. This provided KneeTex with a very fine-grained lexico-semantic knowledge base, which is highly attuned to the given sublanguage. Information extraction results were evaluated on a test set of 100 MRI reports. A gold standard consisted of 1,259 filled template records with the following slots: finding, finding qualifier, negation, certainty, anatomy and anatomy qualifier. KneeTex extracted information with precision of 98.00 %, recall of 97.63 % and F-measure of 97.81 %, the values of which are in line with human-like performance. KneeTex is an open-source, stand-alone application for information extraction from narrative reports that describe an MRI scan of the knee. Given an MRI report as input, the system outputs the corresponding clinical findings in the form of JavaScript Object Notation objects. The extracted information is mapped onto TRAK, an ontology that formally models knowledge relevant for the rehabilitation of knee conditions. As a result, formally structured and coded information allows for complex searches to be conducted efficiently over the original MRI reports, thereby effectively supporting epidemiologic studies of knee conditions.

Feasibility of MR-Temperature Mapping of Ultrasonic Heating from a CMUT

PubMed Central

Wong, Serena H.; Watkins, Ronald D.; Kupnik, Mario; Butts-Pauly, Kim; Khuri-Yakub, Butrus T.

2014-01-01

In the last decade, high intensity focused ultrasound (HIFU) has gained popularity as a minimally-invasive and non-invasive therapeutic tool for treatment of cancers, arrhythmias, and other medical conditions. HIFU therapy is often guided by magnetic resonance imaging (MRI), which provides anatomical images for therapeutic device placement, temperature maps for treatment guidance, and post-operative evaluation of the region of interest. While piezoelectric transducers are dominantly used for MR-guided HIFU, capacitive micromachined ultrasonic transducers (CMUTs) show competitive advantages such as ease of fabrication, integration with electronics, improved efficiency, and reduction of self-heating. In this paper, we will show our first results of an unfocused CMUT transducer monitored by MR-temperature maps. This 2.51 mm by 2.32 mm, unfocused CMUT heated a HIFU phantom by 14°C in 2.5 min. This temperature rise was successfully monitored by MR thermometry in a 3.0 T General Electric scanner. PMID:18467225

The neural correlates of self-referential memory encoding and retrieval in schizophrenia.

PubMed

Jimenez, Amy M; Lee, Junghee; Wynn, Jonathan K; Green, Michael F

2018-01-31

Enhanced memory for self-oriented information is known as the self-referential memory (SRM) effect. fMRI studies of the SRM effect have focused almost exclusively on encoding, revealing selective engagement of the medial prefrontal cortex (mPFC) during "self" relative to other processing conditions. Other critical areas for self-processing include ventrolateral prefrontal cortex (vlPFC), temporo-parietal junction (TPJ) and posterior cingulate/precuneus (PCC/PC). Previous behavioral studies show that individuals with schizophrenia fail to benefit from this memory boost. However, the neural correlates of this deficit, at either encoding or retrieval, are unknown. Twenty individuals with schizophrenia and 16 healthy controls completed an event-related fMRI SRM paradigm. During encoding, trait adjectives were judged in terms of structural features ("case" condition), social desirability ("other" condition), or as self-referential ("self" condition). Participants then completed an unexpected recognition test (retrieval phase). We examined BOLD activation during both encoding and retrieval within mPFC, vlPFC, TPJ, and PCC/PC regions-of-interest (ROIs). During encoding, fMRI data indicated both groups had greater activation during the "self" relative to the "other" condition across ROIs. Controls showed this primarily in mPFC whereas patients showed this in PCC/PC. During retrieval, fMRI data indicated controls showed differentiation across ROIs between "self" and "other" conditions, but patients did not. Results suggest regional differences in the neural processing of self-referential information in individuals with schizophrenia, perhaps because representation of the self is not as well established in patients relative to controls. The current study presents novel findings that add to the literature implicating impaired self-oriented processing in schizophrenia. Published by Elsevier Ltd.

Real-time functional magnetic resonance imaging neurofeedback in motor neurorehabilitation.

PubMed

Linden, David E J; Turner, Duncan L

2016-08-01

Recent developments in functional magnetic resonance imaging (fMRI) have catalyzed a new field of translational neuroscience. Using fMRI to monitor the aspects of task-related changes in neural activation or brain connectivity, investigators can offer feedback of simple or complex neural signals/patterns back to the participant on a quasireal-time basis [real-time-fMRI-based neurofeedback (rt-fMRI-NF)]. Here, we introduce some background methodology of the new developments in this field and give a perspective on how they may be used in neurorehabilitation in the future. The development of rt-fMRI-NF has been used to promote self-regulation of activity in several brain regions and networks. In addition, and unlike other noninvasive techniques, rt-fMRI-NF can access specific subcortical regions and in principle any region that can be monitored using fMRI including the cerebellum, brainstem and spinal cord. In Parkinson's disease and stroke, rt-fMRI-NF has been demonstrated to alter neural activity after the self-regulation training was completed and to modify specific behaviours. Future exploitation of rt-fMRI-NF could be used to induce neuroplasticity in brain networks that are involved in certain neurological conditions. However, currently, the use of rt-fMRI-NF in randomized, controlled clinical trials is in its infancy.

Research diagnostic criteria for temporomandibular disorders (RDC/TMD): development of image analysis criteria and examiner reliability for image analysis.

PubMed

Ahmad, Mansur; Hollender, Lars; Anderson, Quentin; Kartha, Krishnan; Ohrbach, Richard; Truelove, Edmond L; John, Mike T; Schiffman, Eric L

2009-06-01

As part of the Multisite Research Diagnostic Criteria For Temporomandibular Disorders (RDC/TMD) Validation Project, comprehensive temporomandibular joint diagnostic criteria were developed for image analysis using panoramic radiography, magnetic resonance imaging (MRI), and computerized tomography (CT). Interexaminer reliability was estimated using the kappa (kappa) statistic, and agreement between rater pairs was characterized by overall, positive, and negative percent agreement. Computerized tomography was the reference standard for assessing validity of other imaging modalities for detecting osteoarthritis (OA). For the radiologic diagnosis of OA, reliability of the 3 examiners was poor for panoramic radiography (kappa = 0.16), fair for MRI (kappa = 0.46), and close to the threshold for excellent for CT (kappa = 0.71). Using MRI, reliability was excellent for diagnosing disc displacements (DD) with reduction (kappa = 0.78) and for DD without reduction (kappa = 0.94) and good for effusion (kappa = 0.64). Overall percent agreement for pairwise ratings was >or=82% for all conditions. Positive percent agreement for diagnosing OA was 19% for panoramic radiography, 59% for MRI, and 84% for CT. Using MRI, positive percent agreement for diagnoses of any DD was 95% and of effusion was 81%. Negative percent agreement was >or=88% for all conditions. Compared with CT, panoramic radiography and MRI had poor and marginal sensitivity, respectively, but excellent specificity in detecting OA. Comprehensive image analysis criteria for the RDC/TMD Validation Project were developed, which can reliably be used for assessing OA using CT and for disc position and effusion using MRI.

Passive Ventricular Mechanics Modelling Using MRI of Structure and Function

PubMed Central

Wang, V.Y.; Lam, H.I.; Ennis, D.B.; Young, A.A.; Nash, M.P.

2009-01-01

Patients suffering from dilated cardiomyopathy or myocardial infarction can develop left ventricular (LV) diastolic impairment. The LV remodels its structure and function to adapt to pathophysiological changes in geometry and loading conditions and this remodeling process can alter the passive ventricular mechanics. In order to better understand passive ventricular mechanics, a LV finite element model was developed to incorporate physiological and mechanical information derived from in vivo magnetic resonance imaging (MRI) tissue tagging, in vivo LV cavity pressure recording and ex vivo diffusion tensor MRI (DTMRI) of a canine heart. MRI tissue tagging enables quantitative evaluation of cardiac mechanical function with high spatial and temporal resolution, whilst the direction of maximum water diffusion (the primary eigenvector) in each voxel of a DTMRI directly correlates with the myocardial fibre orientation. This model was customized to the geometry of the canine LV during diastasis by fitting the segmented epicardial and endocardial surface data from tagged MRI using nonlinear finite element fitting techniques. Myofibre orientations, extracted from DTMRI of the same heart, were incorporated into this geometric model using a free form deformation methodology. Pressure recordings, temporally synchronized to the tissue tagging MRI data, were used to simulate the LV deformation during diastole. Simulation of the diastolic LV mechanics allowed us to estimate the stiffness of the passive LV myocardium based on kinematic data obtained from tagged MRI. This integrated physiological model will allow more insight into the regional passive diastolic mechanics of the LV on an individualized basis, thereby improving our understanding of the underlying structural basis of mechanical dysfunction in pathological conditions. PMID:18982680

Evaluation of magnetic resonance imaging issues for a wirelessly powered lead used for epidural, spinal cord stimulation.

PubMed

Shellock, Frank G; Audet-Griffin, Annabelle J

2014-06-01

The objective of this investigation was to evaluate magnetic resonance imaging (MRI) issues (magnetic field interactions, MRI-related heating, and artifacts) for a wirelessly powered lead used for spinal cord stimulation (SCS). A newly developed, wirelessly powered lead (Freedom-4, Stimwave Technologies Inc., Scottsdale, AZ, USA) underwent evaluation for magnetic field interactions (translational attraction and torque) at 3 Tesla, MRI-related heating at 1.5 Tesla/64 MHz and 3 Tesla/128 MHz, and artifacts at 3 Tesla using standardized techniques. MRI-related heating tests were conducted by placing the lead in a gelled-saline-filled phantom and performing MRI procedures using relatively high levels of radiofrequency energy. Artifacts were characterized using T1-weighted, spin echo (SE), and gradient echo (GRE) pulse sequences. The lead exhibited minor magnetic field interactions (2 degree deflection angle and no torque). Heating was not substantial under 1.5 Tesla/64 MHz (highest temperature change, 2.3°C) and 3 Tesla/128 MHz (highest temperature change, 2.2°C) MRI conditions. Artifacts were moderate in size relative to the size and shape of the lead. These findings demonstrated that it is acceptable for a patient with this wirelessly powered lead used for SCS to undergo MRI under the conditions utilized in this investigation and according to other necessary guidelines. Artifacts seen on magnetic resonance images may pose possible problems if the area of interest is in the same area or close to this lead. © 2013 International Neuromodulation Society.

Passive ventricular mechanics modelling using MRI of structure and function.

PubMed

Wang, V Y; Lam, H I; Ennis, D B; Young, A A; Nash, M P

2008-01-01

Patients suffering from dilated cardiomyopathy or myocardial infarction can develop left ventricular (LV) diastolic impairment. The LV remodels its structure and function to adapt to pathophysiological changes in geometry and loading conditions and this remodeling process can alter the passive ventricular mechanics. In order to better understand passive ventricular mechanics, a LV finite element model was developed to incorporate physiological and mechanical information derived from in vivo magnetic resonance imaging (MRI) tissue tagging, in vivo LV cavity pressure recording and ex vivo diffusion tensor MRI (DTMRI) of a canine heart. MRI tissue tagging enables quantitative evaluation of cardiac mechanical function with high spatial and temporal resolution, whilst the direction of maximum water diffusion (the primary eigenvector) in each voxel of a DTMRI directly correlates with the myocardial fibre orientation. This model was customized to the geometry of the canine LV during diastasis by fitting the segmented epicardial and endocardial surface data from tagged MRI using nonlinear finite element fitting techniques. Myofibre orientations, extracted from DTMRI of the same heart, were incorporated into this geometric model using a free form deformation methodology. Pressure recordings, temporally synchronized to the tissue tagging MRI data, were used to simulate the LV deformation during diastole. Simulation of the diastolic LV mechanics allowed us to estimate the stiffness of the passive LV myocardium based on kinematic data obtained from tagged MRI. This integrated physiological model will allow more insight into the regional passive diastolic mechanics of the LV on an individualized basis, thereby improving our understanding of the underlying structural basis of mechanical dysfunction in pathological conditions.

ACCRETION DISK DYNAMO AS THE TRIGGER FOR X-RAY BINARY STATE TRANSITIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Begelman, Mitchell C.; Armitage, Philip J.; Reynolds, Christopher S., E-mail: mitch@jila.colorado.edu

2015-08-20

Magnetohydrodynamic accretion disk simulations suggest that much of the energy liberated by the magnetorotational instability (MRI) can be channeled into large-scale toroidal magnetic fields through dynamo action. Under certain conditions, this field can dominate over gas and radiation pressure in providing vertical support against gravity, even close to the midplane. Using a simple model for the creation of this field, its buoyant rise, and its coupling to the gas, we show how disks could be driven into this magnetically dominated state and deduce the resulting vertical pressure and density profiles. Applying an established criterion for MRI to operate in themore » presence of a toroidal field, we show that magnetically supported disks can have two distinct MRI-active regions, separated by a “dead zone” where local MRI is suppressed, but where magnetic energy continues to flow upward from the dynamo region below. We suggest that the relative strengths of the MRI zones, and the local poloidal flux, determine the spectral states of X-ray binaries. Specifically, “intermediate” and “hard” accretion states occur when MRI is triggered in the hot, upper zone of the corona, while disks in “soft” states do not develop the upper MRI zone. We discuss the conditions under which various transitions should take place and speculate on the relationship of dynamo activity to the various types of quasi-periodic oscillations that sometimes appear in the hard spectral components. The model also explains why luminous accretion disks in the “soft” state show no signs of the thermal/viscous instability predicted by standard α-models.« less

SU-C-213-07: Fabrication and Testing of a 3D-Printed Small Animal Rectal Cooling Device to Evaluate Local Hypothermia as a Radioprotector During Prostate SBRT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hrycushko, B; Chopra, R; Futch, C

Purpose: The protective effects of induced or even accidental hypothermia on the human body are widespread with several medical uses currently under active research. In vitro experiments using human cell lines have shown hypothermia provides a radioprotective effect that becomes more pronounced at large, single-fraction doses common to SBRT treatments. Relevant to prostate SBRT, this work details the fabrication and testing of a 3D-printed cooling device to facilitate the investigation of the radioprotective effect of local hypothermia on the rat rectum. Methods: A 3cm long, two-channel rectal cooling device was designed in SOLIDWORKS CAD for 3D printing. The water intakemore » nozzle is connected to a 1mm diameter brass pipe from which water flows and circulates back around to the exit nozzle. Both nozzles are connected by plastic tubing to a water chiller pump. Following leak-proof testing, fiber optic temperature probes were used to evaluate the temperature over time when placed adjacent to the cooling device within a rat rectum. MRI thermometry characterized the relative temperature distribution in concentric ROIs surrounding the probe. CBCT images from a small-animal irradiator were evaluated for imaging artifacts which could affect Monte Carlo dose calculations during treatment planning. Results: The rectal temperature adjacent to the cooling device decreased from body temperature (37°C) to 15°C in 10–20 minutes from device insertion. Rectal temperature was maintained at 15±3°C during active cooling. MRI thermometry tests revealed a steep temperature gradient with increasing distance from the cooling device, with the desired temperature range maintained within the surrounding few millimeters. Conclusion: A 3D printed rectal cooling device was fabricated for the purpose of inducing local hypothermia in rat rectums. Rectal cooling capabilities were characterized in-vivo to facilitate an investigation of the radioprotective effect of hypothermia for late rectal toxicity following a single large dose of radiation. Funding support provided by RSNA research seed grant.« less

Machine-Specific Magnetic Resonance Imaging Quality Control Procedures for Stereotactic Radiosurgery Treatment Planning

PubMed Central

Taghizadeh, Somayeh; Yang, Claus Chunli; R. Kanakamedala, Madhava; Morris, Bart; Vijayakumar, Srinivasan

2017-01-01

Purpose Magnetic resonance (MR) images are necessary for accurate contouring of intracranial targets, determination of gross target volume and evaluation of organs at risk during stereotactic radiosurgery (SRS) treatment planning procedures. Many centers use magnetic resonance imaging (MRI) simulators or regular diagnostic MRI machines for SRS treatment planning; while both types of machine require two stages of quality control (QC), both machine- and patient-specific, before use for SRS, no accepted guidelines for such QC currently exist. This article describes appropriate machine-specific QC procedures for SRS applications. Methods and materials We describe the adaptation of American College of Radiology (ACR)-recommended QC tests using an ACR MRI phantom for SRS treatment planning. In addition, commercial Quasar MRID3D and Quasar GRID3D phantoms were used to evaluate the effects of static magnetic field (B0) inhomogeneity, gradient nonlinearity, and a Leksell G frame (SRS frame) and its accessories on geometrical distortion in MR images. Results QC procedures found in-plane distortions (Maximum = 3.5 mm, Mean = 0.91 mm, Standard deviation = 0.67 mm, >2.5 mm (%) = 2) in X-direction (Maximum = 2.51 mm, Mean = 0.52 mm, Standard deviation = 0.39 mm, > 2.5 mm (%) = 0) and in Y-direction (Maximum = 13. 1 mm , Mean = 2.38 mm, Standard deviation = 2.45 mm, > 2.5 mm (%) = 34) in Z-direction and < 1 mm distortion at a head-sized region of interest. MR images acquired using a Leksell G frame and localization devices showed a mean absolute deviation of 2.3 mm from isocenter. The results of modified ACR tests were all within recommended limits, and baseline measurements have been defined for regular weekly QC tests. Conclusions With appropriate QC procedures in place, it is possible to routinely obtain clinically useful MR images suitable for SRS treatment planning purposes. MRI examination for SRS planning can benefit from the improved localization and planning possible with the superior image quality and soft tissue contrast achieved under optimal conditions. PMID:29487771

Machine-Specific Magnetic Resonance Imaging Quality Control Procedures for Stereotactic Radiosurgery Treatment Planning.

PubMed

Fatemi, Ali; Taghizadeh, Somayeh; Yang, Claus Chunli; R Kanakamedala, Madhava; Morris, Bart; Vijayakumar, Srinivasan

2017-12-18

Purpose Magnetic resonance (MR) images are necessary for accurate contouring of intracranial targets, determination of gross target volume and evaluation of organs at risk during stereotactic radiosurgery (SRS) treatment planning procedures. Many centers use magnetic resonance imaging (MRI) simulators or regular diagnostic MRI machines for SRS treatment planning; while both types of machine require two stages of quality control (QC), both machine- and patient-specific, before use for SRS, no accepted guidelines for such QC currently exist. This article describes appropriate machine-specific QC procedures for SRS applications. Methods and materials We describe the adaptation of American College of Radiology (ACR)-recommended QC tests using an ACR MRI phantom for SRS treatment planning. In addition, commercial Quasar MRID 3D and Quasar GRID 3D phantoms were used to evaluate the effects of static magnetic field (B 0 ) inhomogeneity, gradient nonlinearity, and a Leksell G frame (SRS frame) and its accessories on geometrical distortion in MR images. Results QC procedures found in-plane distortions (Maximum = 3.5 mm, Mean = 0.91 mm, Standard deviation = 0.67 mm, >2.5 mm (%) = 2) in X-direction (Maximum = 2.51 mm, Mean = 0.52 mm, Standard deviation = 0.39 mm, > 2.5 mm (%) = 0) and in Y-direction (Maximum = 13. 1 mm , Mean = 2.38 mm, Standard deviation = 2.45 mm, > 2.5 mm (%) = 34) in Z-direction and < 1 mm distortion at a head-sized region of interest. MR images acquired using a Leksell G frame and localization devices showed a mean absolute deviation of 2.3 mm from isocenter. The results of modified ACR tests were all within recommended limits, and baseline measurements have been defined for regular weekly QC tests. Conclusions With appropriate QC procedures in place, it is possible to routinely obtain clinically useful MR images suitable for SRS treatment planning purposes. MRI examination for SRS planning can benefit from the improved localization and planning possible with the superior image quality and soft tissue contrast achieved under optimal conditions.

Cognitive dissonance induction in everyday life: An fMRI study.

PubMed

de Vries, Jan; Byrne, Mark; Kehoe, Elizabeth

2015-01-01

This functional magnetic resonance imaging (fMRI) study explored the neural substrates of cognitive dissonance during dissonance "induction." A novel task was developed based on the results of a separate item selection study (n = 125). Items were designed to generate dissonance by prompting participants to reflect on everyday personal experiences that were inconsistent with values they had expressed support for. One experimental condition (dissonance) and three control conditions (justification, consonance, and non-self-related inconsistency) were used for comparison. Items of all four types were presented to each participant (n = 14) in a randomized design. The fMRI analysis used a whole-brain approach focusing on the moments dissonance was induced. Results showed that in comparison with the control conditions the dissonance experience led to higher levels of activation in several brain regions. Specifically dissonance was associated with increased neural activation in key brain regions including the anterior cingulate cortex (ACC), anterior insula, inferior frontal gyrus, and precuneus. This supports current perspectives that emphasize the role of anterior cingulate and insula in dissonance processing. Less extensive activation in the prefrontal cortex than in some previous studies is consistent with this study's emphasis on dissonance induction, rather than reduction. This article also contains a short review and comparison with other fMRI studies of cognitive dissonance.

Preclinical evaluation of an MRI-compatible pneumatic robot for angulated needle placement in transperineal prostate interventions.

PubMed

Tokuda, Junichi; Song, Sang-Eun; Fischer, Gregory S; Iordachita, Iulian I; Seifabadi, Reza; Cho, Nathan B; Tuncali, Kemal; Fichtinger, Gabor; Tempany, Clare M; Hata, Nobuhiko

2012-11-01

To evaluate the targeting accuracy of a small profile MRI-compatible pneumatic robot for needle placement that can angulate a needle insertion path into a large accessible target volume. We extended our MRI-compatible pneumatic robot for needle placement to utilize its four degrees-of-freedom (4-DOF) mechanism with two parallel triangular structures and support transperineal prostate biopsies in a closed-bore magnetic resonance imaging (MRI) scanner. The robot is designed to guide a needle toward a lesion so that a radiologist can manually insert it in the bore. The robot is integrated with navigation software that allows an operator to plan angulated needle insertion by selecting a target and an entry point. The targeting error was evaluated while the angle between the needle insertion path and the static magnetic field was between -5.7° and 5.7° horizontally and between -5.7° and 4.3° vertically in the MRI scanner after sterilizing and draping the device. The robot positioned the needle for angulated insertion as specified on the navigation software with overall targeting error of 0.8 ± 0.5mm along the horizontal axis and 0.8 ± 0.8mm along the vertical axis. The two-dimensional root-mean-square targeting error on the axial slices as containing the targets was 1.4mm. Our preclinical evaluation demonstrated that the MRI-compatible pneumatic robot for needle placement with the capability to angulate the needle insertion path provides targeting accuracy feasible for clinical MRI-guided prostate interventions. The clinical feasibility has to be established in a clinical study.

Quantitative analysis of skeletal muscle mass in patients with rheumatic diseases under glucocorticoid therapy--comparison among bioelectrical impedance analysis, computed tomography, and magnetic resonance imaging.

PubMed

Hosono, Osamu; Yoshikawa, Noritada; Shimizu, Noriaki; Kiryu, Shigeru; Uehara, Masaaki; Kobayashi, Hiroshi; Matsumiya, Ryo; Kuribara, Akiko; Maruyama, Takako; Tanaka, Hirotoshi

2015-03-01

To determine the availability of bioelectrical impedance analysis (BIA), computed tomography (CT), and magnetic resonance imaging (MRI) for measurement of skeletal muscle mass in patients with rheumatic diseases and quantitatively assess skeletal muscle loss after glucocorticoid (GC) treatment. The data from 22 patients with rheumatic diseases were retrospectively obtained. The muscle mass of body segments was measured with a BIA device in terms of skeletal muscle mass index (SMI). Cross-sectional area (CSA) was obtained from CT and MRI scans at the mid-thigh level using the image analysis program. We further assessed the data of three different measurements before and after GC treatment in 7 patients with rheumatic diseases. SMI of whole body was significantly correlated with estimated muscle volume and mid-thigh muscle CSA with CT and MRI (p < 0.01). Significant correlations between SMI and mid-thigh muscle CSA of each leg were also found (p < 0.01). All the three measurements were negatively correlated with GC dosage (p < 0.01). Significant decline in mid-thigh muscle CSA with CT and MRI was found after GC treatment in 7 patients (p < 0.02). Those patients showed significant decline in SMI of whole body after GC treatment, but not in SMI of each leg. On the other hand, significant correlations between mid-thigh muscle CSA with CT and MRI were found before and after GC treatment (p < 0.01). GC-related skeletal muscle loss could be quantitatively assessed with BIA, CT, or MRI in patients with rheumatic diseases, and CT and MRI appeared to be more accurate than BIA.

MRI-guided brain PET image filtering and partial volume correction

NASA Astrophysics Data System (ADS)

Yan, Jianhua; Chu-Shern Lim, Jason; Townsend, David W.

2015-02-01

Positron emission tomography (PET) image quantification is a challenging problem due to limited spatial resolution of acquired data and the resulting partial volume effects (PVE), which depend on the size of the structure studied in relation to the spatial resolution and which may lead to over or underestimation of the true tissue tracer concentration. In addition, it is usually necessary to perform image smoothing either during image reconstruction or afterwards to achieve a reasonable signal-to-noise ratio. Typically, an isotropic Gaussian filtering (GF) is used for this purpose. However, the noise suppression is at the cost of deteriorating spatial resolution. As hybrid imaging devices such as PET/MRI have become available, the complementary information derived from high definition morphologic images could be used to improve the quality of PET images. In this study, first of all, we propose an MRI-guided PET filtering method by adapting a recently proposed local linear model and then incorporate PVE into the model to get a new partial volume correction (PVC) method without parcellation of MRI. In addition, both the new filtering and PVC are voxel-wise non-iterative methods. The performance of the proposed methods were investigated with simulated dynamic FDG brain dataset and 18F-FDG brain data of a cervical cancer patient acquired with a simultaneous hybrid PET/MR scanner. The initial simulation results demonstrated that MRI-guided PET image filtering can produce less noisy images than traditional GF and bias and coefficient of variation can be further reduced by MRI-guided PET PVC. Moreover, structures can be much better delineated in MRI-guided PET PVC for real brain data.

Multiparametric MRI of intracranial aneurysms treated with the Woven EndoBridge (WEB): a case of Faraday's cage?

PubMed

Nawka, Marie Teresa; Sedlacik, Jan; Frölich, Andreas; Bester, Maxim; Fiehler, Jens; Buhk, Jan-Hendrik

2018-02-10

To evaluate multiparametric MRI including non-contrast and contrast-enhanced morphological and angiographic techniques for intracranial aneurysms treated with the single-layer Woven EndoBridge (WEB) embolization system applying simultaneous digital subtraction angiography (DSA) as the reference of standard. We retrospectively identified all patients with incidental and acute ruptured intracranial aneurysms treated with a WEB device (WEB SL and WEB SLS) between March 2014 and June 2016 in our neurovascular center with early (within 7 days) postinterventional multiparametric MRI as well as mid-term (5-8 months) follow-up MRI and DSA available. Occlusion rates were recorded both in DSA and MR angiography (MRA). In MRI, signal intensities within the WEB as well as in the occluded dome distal to the WEB, if present, were measured by region-of-interest (ROI) analysis. Twenty-five patients fulfilled the inclusion criteria. Rates of complete/adequate occlusion at mid-term follow-up were 84% with both MRA and DSA. A strong signal loss within the WEB was observed in all MR sequences at initial and follow-up examinations. ROI analysis did not reveal significant differences in non-contrast (P=0.946) and contrast-enhanced imaging (P=0.377). A T1-hyperintense thrombus in the non-WEB-carrying dome was a frequent observation. Signal intensity measurements in multiparametric MRI suggest that neither contrast-enhanced MRA nor morphological sequences are capable of revealing reliable information on the WEB lumen, presumably due to radio frequency shielding. MRI is therefore not suitable for confirming complete thrombus formation within the WEB. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Techniques for Interventional MRI Guidance in Closed-Bore Systems.

PubMed

Busse, Harald; Kahn, Thomas; Moche, Michael

2018-02-01

Efficient image guidance is the basis for minimally invasive interventions. In comparison with X-ray, computed tomography (CT), or ultrasound imaging, magnetic resonance imaging (MRI) provides the best soft tissue contrast without ionizing radiation and is therefore predestined for procedural control. But MRI is also characterized by spatial constraints, electromagnetic interactions, long imaging times, and resulting workflow issues. Although many technical requirements have been met over the years-most notably magnetic resonance (MR) compatibility of tools, interventional pulse sequences, and powerful processing hardware and software-there is still a large variety of stand-alone devices and systems for specific procedures only.Stereotactic guidance with the table outside the magnet is common and relies on proper registration of the guiding grids or manipulators to the MR images. Instrument tracking, often by optical sensing, can be added to provide the physicians with proper eye-hand coordination during their navigated approach. Only in very short wide-bore systems, needles can be advanced at the extended arm under near real-time imaging. In standard magnets, control and workflow may be improved by remote operation using robotic or manual driving elements.This work highlights a number of devices and techniques for different interventional settings with a focus on percutaneous, interstitial procedures in different organ regions. The goal is to identify technical and procedural elements that might be relevant for interventional guidance in a broader context, independent of the clinical application given here. Key challenges remain the seamless integration into the interventional workflow, safe clinical translation, and proper cost effectiveness.

Quantitative nuclear magnetic resonance to measure body composition in infants and children

USDA-ARS?s Scientific Manuscript database

Quantitative Nuclear Magnetic Resonance (QMR) is being used in human adults to obtain measures of total body fat (FM) with high precision. The current study assessed a device specially designed to accommodate infants and children between 3 and 50 kg (EchoMRI-AH™). Body composition of 113 infants and...

Technical Note: Independent component analysis for quality assurance in functional MRI.

PubMed

Astrakas, Loukas G; Kallistis, Nikolaos S; Kalef-Ezra, John A

2016-02-01

Independent component analysis (ICA) is an established method of analyzing human functional MRI (fMRI) data. Here, an ICA-based fMRI quality control (QC) tool was developed and used. ICA-based fMRI QC tool to be used with a commercial phantom was developed. In an attempt to assess the performance of the tool relative to preexisting alternative tools, it was used seven weeks before and eight weeks after repair of a faulty gradient amplifier of a non-state-of-the-art MRI unit. More specifically, its performance was compared with the AAPM 100 acceptance testing and quality assurance protocol and two fMRI QC protocols, proposed by Freidman et al. ["Report on a multicenter fMRI quality assurance protocol," J. Magn. Reson. Imaging 23, 827-839 (2006)] and Stocker et al. ["Automated quality assurance routines for fMRI data applied to a multicenter study," Hum. Brain Mapp. 25, 237-246 (2005)], respectively. The easily developed and applied ICA-based QC protocol provided fMRI QC indices and maps equally sensitive to fMRI instabilities with the indices and maps of other established protocols. The ICA fMRI QC indices were highly correlated with indices of other fMRI QC protocols and in some cases theoretically related to them. Three or four independent components with slow varying time series are detected under normal conditions. ICA applied on phantom measurements is an easy and efficient tool for fMRI QC. Additionally, it can protect against misinterpretations of artifact components as human brain activations. Evaluating fMRI QC indices in the central region of a phantom is not always the optimal choice.

Evaluation of an image-based tracking workflow with Kalman filtering for automatic image plane alignment in interventional MRI.

PubMed

Neumann, M; Cuvillon, L; Breton, E; de Matheli, M

2013-01-01

Recently, a workflow for magnetic resonance (MR) image plane alignment based on tracking in real-time MR images was introduced. The workflow is based on a tracking device composed of 2 resonant micro-coils and a passive marker, and allows for tracking of the passive marker in clinical real-time images and automatic (re-)initialization using the microcoils. As the Kalman filter has proven its benefit as an estimator and predictor, it is well suited for use in tracking applications. In this paper, a Kalman filter is integrated in the previously developed workflow in order to predict position and orientation of the tracking device. Measurement noise covariances of the Kalman filter are dynamically changed in order to take into account that, according to the image plane orientation, only a subset of the 3D pose components is available. The improved tracking performance of the Kalman extended workflow could be quantified in simulation results. Also, a first experiment in the MRI scanner was performed but without quantitative results yet.

Targeted brain activation using an MR-compatible wrist torque measurement device and isometric motor tasks during functional magnetic resonance imaging.

PubMed

Vlaar, Martijn P; Mugge, Winfred; Groot, Paul F C; Sharifi, Sarvi; Bour, Lo J; van der Helm, Frans C T; van Rootselaar, Anne-Fleur; Schouten, Alfred C

2016-07-01

Dedicated pairs of isometric wrist flexion tasks, with and without visual feedback of the exerted torque, were designed to target activation of the CBL and BG in healthy subjects during functional magnetic resonance imaging (fMRI). Selective activation of the cerebellum (CBL) and basal ganglia (BG), often implicated in movement disorders such as tremor and dystonia, may help identify pathological changes and expedite diagnosis. A prototyped MR-compatible wrist torque measurement device, free of magnetic and conductive materials, allowed safe execution of tasks during fMRI without causing artifacts. A significant increase of activity in CBL and BG was found in healthy volunteers during a constant torque task with visual feedback compared to a constant torque task without visual feedback. This study shows that specific pairs of motor tasks using MR-compatible equipment at the wrist allow for targeted activation of CBL and BG, paving a new way for research into the pathophysiology of movement disorders. Copyright © 2016 Elsevier Inc. All rights reserved.

A feasibility study for compressed sensing combined phase contrast MR angiography reconstruction

NASA Astrophysics Data System (ADS)

Lee, Dong-Hoon; Hong, Cheol-Pyo; Lee, Man-Woo; Han, Bong-Soo

2012-02-01

Phase contrast magnetic resonance angiography (PC MRA) is a technique for flow velocity measurement and vessels visualization, simultaneously. The PC MRA takes long scan time because each flow encoding gradients which are composed bipolar gradient type need to reconstruct the angiography image. Moreover, it takes more image acquisition time when we use the PC MRA at the low-tesla MRI system. In this study, we studied and evaluation of feasibility for CS MRI reconstruction combined PC MRA which data acquired by low-tesla MRI system. We used non-linear reconstruction algorithm which named Bregman iteration for CS image reconstruction and validate the usefulness of CS combined PC MRA reconstruction technique. The results of CS reconstructed PC MRA images provide similar level of image quality between fully sampled reconstruction data and sparse sampled reconstruction using CS technique. Although our results used half of sampling ratio and do not used specification hardware device or performance which are improving the temporal resolution of MR image acquisition such as parallel imaging reconstruction using phased array coil or non-cartesian trajectory, we think that CS combined PC MRA technique will be helpful to increase the temporal resolution and at low-tesla MRI system.

Development of a superconducting bulk magnet for NMR and MRI.

PubMed

Nakamura, Takashi; Tamada, Daiki; Yanagi, Yousuke; Itoh, Yoshitaka; Nemoto, Takahiro; Utumi, Hiroaki; Kose, Katsumi

2015-10-01

A superconducting bulk magnet composed of six vertically stacked annular single-domain c-axis-oriented Eu-Ba-Cu-O crystals was energized to 4.74 T using a conventional superconducting magnet for high-resolution NMR spectroscopy. Shim coils, gradient coils, and radio frequency coils for high resolution NMR and MRI were installed in the 23 mm-diameter room-temperature bore of the bulk magnet. A 6.9 ppm peak-to-peak homogeneous region suitable for MRI was achieved in the central cylindrical region (6.2 mm diameter, 9.1 mm length) of the bulk magnet by using a single layer shim coil. A 21 Hz spectral resolution that can be used for high resolution NMR spectroscopy was obtained in the central cylindrical region (1.3 mm diameter, 4 mm length) of the bulk magnet by using a multichannel shim coil. A clear 3D MR image dataset of a chemically fixed mouse fetus with (50 μm)(3) voxel resolution was obtained in 5.5 h. We therefore concluded that the cryogen-free superconducting bulk magnet developed in this study is useful for high-resolution desktop NMR, MRI and mobile NMR device. Copyright © 2015 Elsevier Inc. All rights reserved.

Ultra-low field MRI food inspection system prototype

NASA Astrophysics Data System (ADS)

Kawagoe, Satoshi; Toyota, Hirotomo; Hatta, Junichi; Ariyoshi, Seiichiro; Tanaka, Saburo

2016-11-01

We develop an ultra-low field (ULF) magnetic resonance imaging (MRI) system using a high-temperature superconducting quantum interference device (HTS-SQUID) for food inspection. A two-dimensional (2D)-MR image is reconstructed from the grid processing raw data using the 2D fast Fourier transform method. In a previous study, we combined an LC resonator with the ULF-MRI system to improve the detection area of the HTS-SQUID. The sensitivity was improved, but since the experiments were performed in a semi-open magnetically shielded room (MSR), external noise was a problem. In this study, we develop a compact magnetically shielded box (CMSB), which has a small open window for transfer of a pre-polarized sample. Experiments were performed in the CMSB and 2D-MR images were compared with images taken in the semi-open MSR. A clear image of a disk-shaped water sample is obtained, with an outer dimension closer to that of the real sample than in the image taken in the semi-open MSR. Furthermore, the 2D-MR image of a multiple cell water sample is clearly reconstructed. These results show the applicability of the ULF-MRI system in food inspection.

The Feasibility of Integrating Elastography Measurements into MRI-Guided Transurethral Ultrasound Therapy

NASA Astrophysics Data System (ADS)

Arani, Arvin; Huang, Yuexi; Bronskill, Michael; Chopra, Rajiv

2009-04-01

MRI-guided transurethral ultrasound therapy is being developed as a minimally invasive treatment for localized prostate cancer. The capability to identify target regions prior to therapy would provide an integrated diagnostic and therapeutic solution to the management of this disease. The objective of this project is to evaluate the feasibility of performing elastography using a transurethral actuator. Shear waves were generated in the prostate by vibrating the transurethral actuator longitudinally and resolving the tissue displacements with a 1.5 Tesla MRI. A piezoelectric actuator was used to vibrate the transurethral device with an amplitude of 32 um at frequencies of 100 and 250 Hz. GRE imaging sequences with displacement encoded along the direction of vibration were acquired transverse and parallel to the rod to visualize the dynamics of wave propagation. Experiments were performed in phantoms (8% gelatin) and in a canine model (n = 5). Vibration was achieved in the MRI without significant loss of SNR in the images. The shear waves produced in the gel were cylindrical in nature, and extended along the length of the rod. Shear wave propagation in the canine prostate gland was observed at 100 and 250 Hz, and shear modulus values agreed with previously published values.

The rf coil as a sensitive motion detector for magnetic resonance imaging.

PubMed

Buikman, D; Helzel, T; Röschmann, P

1988-01-01

A new sensor principle for detection of patient movement in magnetic resonance imaging has been successfully applied for the reduction of motion artifacts. It uses a device that is already present in every MRI system, namely the rf coil. Patient movement within the coil causes changes in the rf impedance match of the coil, which can be measured as variations in the reflected rf power. The principle used for the detection of respiratory and cardiac motion is described, and experimental results measured with several coil arrangements are given. Images are presented which were acquired with respiratory gating derived from the rf body coil of a 2 Tesla whole body MRI system.

Optical measurement of cerebral hemodynamics and oxygen metabolism in neonates with congenital heart defects

NASA Astrophysics Data System (ADS)

Durduran, Turgut; Zhou, Chao; Buckley, Erin M.; Kim, Meeri N.; Yu, Guoqiang; Choe, Regine; Gaynor, J. William; Spray, Thomas L.; Durning, Suzanne M.; Mason, Stefanie E.; Montenegro, Lisa M.; Nicolson, Susan C.; Zimmerman, Robert A.; Putt, Mary E.; Wang, Jiongjiong; Greenberg, Joel H.; Detre, John A.; Yodh, Arjun G.; Licht, Daniel J.

2010-05-01

We employ a hybrid diffuse correlation spectroscopy (DCS) and near-infrared spectroscopy (NIRS) monitor for neonates with congenital heart disease (n=33). The NIRS-DCS device measured changes during hypercapnia of oxyhemoglobin, deoxyhemoglobin, and total hemoglobin concentrations; cerebral blood flow (rCBFDCS); and oxygen metabolism (rCMRO2). Concurrent measurements with arterial spin-labeled magnetic resonance imaging (rCBFASL-MRI, n=12) cross-validate rCBFDCS against rCBFASL-MRI, showing good agreement (R=0.7, p=0.01). The study demonstrates use of NIRS-DCS on a critically ill neonatal population, and the results indicate that the optical technology is a promising clinical method for monitoring this population.

FRIEND Engine Framework: a real time neurofeedback client-server system for neuroimaging studies

PubMed Central

Basilio, Rodrigo; Garrido, Griselda J.; Sato, João R.; Hoefle, Sebastian; Melo, Bruno R. P.; Pamplona, Fabricio A.; Zahn, Roland; Moll, Jorge

2015-01-01

In this methods article, we present a new implementation of a recently reported FSL-integrated neurofeedback tool, the standalone version of “Functional Real-time Interactive Endogenous Neuromodulation and Decoding” (FRIEND). We will refer to this new implementation as the FRIEND Engine Framework. The framework comprises a client-server cross-platform solution for real time fMRI and fMRI/EEG neurofeedback studies, enabling flexible customization or integration of graphical interfaces, devices, and data processing. This implementation allows a fast setup of novel plug-ins and frontends, which can be shared with the user community at large. The FRIEND Engine Framework is freely distributed for non-commercial, research purposes. PMID:25688193

NMR and MRI apparatus and method

DOEpatents

Clarke, John; Kelso, Nathan; Lee, SeungKyun; Moessle, Michael; Myers, Whittier; McDermott, Robert; ten Haken, Bernard; Pines, Alexander; Trabesinger, Andreas

2007-03-06

Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. Additional signal to noise benefits are obtained by use of a low noise polarization coil, comprising litz wire or superconducting materials. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

CONTROL LIMITER DEVICE

DOEpatents

DeShong, J.A.

1960-03-01

A control-limiting device for monltoring a control system is described. The system comprises a conditionsensing device, a condition-varying device exerting a control over the condition, and a control means to actuate the condition-varying device. A control-limiting device integrates the total movement or other change of the condition-varying device over any interval of time during a continuum of overlapping periods of time, and if the tothl movement or change of the condition-varying device exceeds a preset value, the control- limiting device will switch the control of the operated apparatus from automatic to manual control.

Strategies to minimize sedation in pediatric body magnetic resonance imaging.

PubMed

Jaimes, Camilo; Gee, Michael S

2016-05-01

The high soft-tissue contrast of MRI and the absence of ionizing radiation make it a valuable tool for assessment of body pathology in children. Infants and young children are often unable to cooperate with awake MRI so sedation or general anesthesia might be required. However, given recent data on the costs and potential risks of anesthesia in young children, there is a need to try to decrease or avoid sedation in this population when possible. Child life specialists in radiology frequently use behavioral techniques and audiovisual support devices, and they practice with children and families using mock scanners to improve child compliance with MRI. Optimization of the MR scanner environment is also important to create a child-friendly space. If the child can remain inside the MRI scanner, a variety of emerging techniques can reduce the effect of involuntary motion. Using sequences with short acquisition times such as single-shot fast spin echo and volumetric gradient echo can decrease artifacts and improve image quality. Breath-holding, respiratory triggering and signal averaging all reduce respiratory motion. Emerging techniques such as radial and multislice k-space acquisition, navigator motion correction, as well as parallel imaging and compressed sensing reconstruction methods can further accelerate acquisition and decrease motion. Collaboration among radiologists, anesthesiologists, technologists, child life specialists and families is crucial for successful performance of MRI in young children.

Noninvasive in vivo tracking of mesenchymal stem cells and evaluation of cell therapeutic effects in a murine model using a clinical 3.0 T MRI.

PubMed

Drey, Florian; Choi, Yeong-Hoon; Neef, Klaus; Ewert, Birgit; Tenbrock, Arne; Treskes, Philipp; Bovenschulte, Henning; Liakopoulos, Oliver J; Brenkmann, Meike; Stamm, Christof; Wittwer, Thorsten; Wahlers, Thorsten

2013-01-01

Cardiac cell therapy with mesenchymal stem cells (MSCs) represents a promising treatment approach for end-stage heart failure. However, little is known about the underlying mechanisms and the fate of the transplanted cells. The objective of the presented work is to determine the feasibility of magnetic resonance imaging (MRI) and in vivo monitoring after transplantation into infarcted mouse hearts using a clinical 3.0 T MRI device. The labeling procedure of bone marrow-derived MSCs with micron-sized paramagnetic iron oxide particles (MPIOs) did not affect the viability of the cells and their cell type-defining properties when compared to unlabeled cells. Using a clinical 3.0 T MRI scanner equipped with a dedicated small animal solenoid coil, 10(5) labeled MSCs could be detected and localized in the mouse hearts for up to 4 weeks after intramyocardial transplantation. Weekly ECG-gated scans using T1-weighted sequences were performed, and left ventricular function was assessed. Histological analysis of hearts confirmed the survival of labeled MSCs in the target area up to 4 weeks after transplantation. In conclusion, in vivo tracking of labeled MSCs using a clinical 3.0 T MRI scanner is feasible. In combination with assessment of heart function, this technology allows the monitoring of the therapeutic efficacy of regenerative therapies in a small animal model.

Artefacts in multimodal imaging of titanium, zirconium and binary titanium–zirconium alloy dental implants: an in vitro study

PubMed Central

Schöllchen, Maximilian; Aarabi, Ghazal; Assaf, Alexandre T; Rendenbach, Carsten; Beck-Broichsitter, Benedicta; Semmusch, Jan; Sedlacik, Jan; Heiland, Max; Fiehler, Jens; Siemonsen, Susanne

2017-01-01

Objectives: To analyze and evaluate imaging artefacts induced by zirconium, titanium and titanium–zirconium alloy dental implants. Methods: Zirconium, titanium and titanium–zirconium alloy implants were embedded in gelatin and MRI, CT and CBCT were performed. Standard protocols were used for each modality. For MRI, line–distance profiles were plotted to quantify the accuracy of size determination. For CT and CBCT, six shells surrounding the implant were defined every 0.5 cm from the implant surface and histogram parameters were determined for each shell. Results: While titanium and titanium–zirconium alloy induced extensive signal voids in MRI owing to strong susceptibility, zirconium implants were clearly definable with only minor distortion artefacts. For titanium and titanium–zirconium alloy, the MR signal was attenuated up to 14.1 mm from the implant. In CT, titanium and titanium–zirconium alloy resulted in less streak artefacts in comparison with zirconium. In CBCT, titanium–zirconium alloy induced more severe artefacts than zirconium and titanium. Conclusions: MRI allows for an excellent image contrast and limited artefacts in patients with zirconium implants. CT and CBCT examinations are less affected by artefacts from titanium and titanium–zirconium alloy implants compared with MRI. The knowledge about differences of artefacts through different implant materials and image modalities might help support clinical decisions for the choice of implant material or imaging device in the clinical setting. PMID:27910719

Artefacts in multimodal imaging of titanium, zirconium and binary titanium-zirconium alloy dental implants: an in vitro study.

PubMed

Smeets, Ralf; Schöllchen, Maximilian; Gauer, Tobias; Aarabi, Ghazal; Assaf, Alexandre T; Rendenbach, Carsten; Beck-Broichsitter, Benedicta; Semmusch, Jan; Sedlacik, Jan; Heiland, Max; Fiehler, Jens; Siemonsen, Susanne

2017-02-01

To analyze and evaluate imaging artefacts induced by zirconium, titanium and titanium-zirconium alloy dental implants. Zirconium, titanium and titanium-zirconium alloy implants were embedded in gelatin and MRI, CT and CBCT were performed. Standard protocols were used for each modality. For MRI, line-distance profiles were plotted to quantify the accuracy of size determination. For CT and CBCT, six shells surrounding the implant were defined every 0.5 cm from the implant surface and histogram parameters were determined for each shell. While titanium and titanium-zirconium alloy induced extensive signal voids in MRI owing to strong susceptibility, zirconium implants were clearly definable with only minor distortion artefacts. For titanium and titanium-zirconium alloy, the MR signal was attenuated up to 14.1 mm from the implant. In CT, titanium and titanium-zirconium alloy resulted in less streak artefacts in comparison with zirconium. In CBCT, titanium-zirconium alloy induced more severe artefacts than zirconium and titanium. MRI allows for an excellent image contrast and limited artefacts in patients with zirconium implants. CT and CBCT examinations are less affected by artefacts from titanium and titanium-zirconium alloy implants compared with MRI. The knowledge about differences of artefacts through different implant materials and image modalities might help support clinical decisions for the choice of implant material or imaging device in the clinical setting.

SU-E-T-368: Effect of a Strong Magnetic Field On Select Radiation Dosimeters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mathis, M; Wen, Z; Tailor, R

Purpose: To determine the effect of a strong magnetic field on TLD-100, OSLD (Al{sub 2}O{sub 2}:C), and PRESAGE dosimetry devices. This study will help to determine which types of dosimeters can be used for quality assurance and in-vivo dosimetry measurements in a magnetic resonance imaginglinear accelerator (MRI-linac) system. Methods: The dosimeters were separated into two categories which were either exposed or not exposed to a strong magnetic field. In each category a set of dosimeters was irradiated with 0, 2, or 6 Gy. To expose the dosimeters to a magnetic field the samples in that category were place in amore » Bruker small animal magnetic resonance scanner at a field strength slightly greater than 2.5 T for at least 1 hour preirradiation and at least 1 hour post-irradiation. Irradiations were performed with a 6 MV x-ray beam from a Varian TrueBeam linac with 10×10 cm{sup 2} field at a 600 MU/min dose rate. The samples that received no radiation dose were used as control detectors. Results: The readouts of the dosimeters which were not exposed to a strong magnetic field were compared with the measurements of the dosimetry devices which were exposed to a magnetic field. No significant differences (less than 2% difference) in the performance of TLD, OSLD, or PRESAGE dosimeters due to exposure to a strong magnetic field were observed. Conclusion: Exposure to a strong magnetic field before and after irradiation does not appear to change the dosimetric properties of TLD, OSLD, or PRESAGE which indicates that these dosimeters have potential for use in quality assurance and in-vivo dosimetry in a MRI-linac. We plan to further test the effect of magnetic fields on these devices by irradiating them in the presence of a magnetic fields similar to those produced by a MRI-linac system. Elekta-MD Anderson Cancer Center Research Agreement.« less

Single-shot turbo spin echo acquisition for in vivo cardiac diffusion MRI.

PubMed

Edalati, Masoud; Lee, Gregory R; Hui Wang; Taylor, Michael D; Li, Yu Y

2016-08-01

Diffusion MRI offers the ability to noninvasively characterize the microstructure of myocardium tissue and detect disease related pathology in cardiovascular examination. This study investigates the feasibility of in vivo cardiac diffusion MRI under free-breathing condition. A high-speed imaging technique, correlation imaging, is used to enable single-shot turbo spin echo for free-breathing cardiac data acquisition. The obtained in vivo cardiac diffusion-weighted images illustrate robust image quality and minor geometry distortions. The resultant diffusion scalar maps show reliable quantitative values consistent with those previously published in the literature. It is demonstrated that this technique has the potential for in vivo free-breathing cardiac diffusion MRI.

[Magnetic resonance imaging of tibial periostitis].

PubMed

Meyer, X; Boscagli, G; Tavernier, T; Aczel, F; Weber, F; Legros, R; Charlopain, P; Martin, J P

1998-01-01

Tibial periostitis frequently occurs in athletes. We present our experience with MRI in a series of 7 patients (11 legs) with this condition. The clinical presentation and scintigraphic scanning suggested the diagnosis. MRI exploration of 11 legs demonstrated a high band-like juxta-osseous signal enhancement of SE and IR T2 weighted sequences in 6 cases, a signal enhancement after i.v. contrast administration in 4. Tibial periostitis is a clinical diagnosis and MRI and scintigraphic findings can be used to assure the differential diagnosis in difficult cases with stress fracture. MRI can visualize juxta-osseous edematous and inflammatory reactions and an increased signal would appear to be characteristic when the band-like image is fixed to the periosteum.

Structural and functional network connectivity breakdown in Alzheimer’s disease studied with magnetic resonance imaging techniques.

PubMed

Filippi, Massimo; Agosta, Federica

2011-01-01

Patients with Alzheimer’s disease (AD) experience a brain network breakdown, reflecting disconnection at both the structural and functional system level. Resting-state (RS) functional MRI (fMRI) studies demonstrated that the regional coherence of the fMRI signal is significantly altered in patients with AD and amnestic mild cognitive impairment. Diffusion tensor (DT) MRI has made it possible to track fiber bundle projections across the brain, revealing a substantially abnormal interplay of “critical” white matter tracts in these conditions. The observed agreement between the results of RS fMRI and DT MRI tractography studies in healthy individuals is encouraging and offers interesting hypotheses to be tested in patients with AD, a MCI, and other dementias in order to improve our understanding of their pathobiology in vivo. In this review,we describe the major findings obtained in AD using RS fMRI and DT MRI tractography, and discuss how the relationship between structure and function of the brain networks in AD may be better understood through the application of MR-based technology. This research endeavor holds a great promise in clarifying the mechanisms of cognitive decline in complex chronic neurodegenerative disorders.

Correlation of probability scores of placenta accreta on magnetic resonance imaging with hemorrhagic morbidity.

PubMed

Lim, Grace; Horowitz, Jeanne M; Berggruen, Senta; Ernst, Linda M; Linn, Rebecca L; Hewlett, Bradley; Kim, Jennifer; Chalifoux, Laurie A; McCarthy, Robert J

2016-11-01

To evaluate the hypothesis that assigning grades to magnetic resonance imaging (MRI) findings of suspected placenta accreta will correlate with hemorrhagic outcomes. We chose a single-center, retrospective, observational design. Nulliparous or multiparous women who had antenatal placental MRI performed at a tertiary level academic hospital were included. Cases with antenatal placental MRI were included and compared with cases without MRI performed. Two radiologists assigned a probability score for accreta to each study. Estimated blood loss and transfusion requirements were compared among groups by the Kruskal-Wallis H test. Thirty-five cases had placental MRI performed. MRI performance was associated with higher blood loss compared with the non-MRI group (2600 [1400-4500]mL vs 900[600-1500]mL, P<.001). There was no difference in estimated blood loss (P=.31) or transfusion (P=.57) among the MRI probability groups. In cases of suspected placenta accreta, probability scores for antenatal placental MRI may not be associated with increasing degrees of hemorrhage. Continued research is warranted to determine the effectiveness of assigning probability scores for antenatal accreta imaging studies, combined with clinical indices of suspicion, in assisting with antenatal multidisciplinary team planning for operative management of this morbid condition. Copyright © 2016 Elsevier Inc. All rights reserved.

Sources and implications of whole-brain fMRI signals in humans

PubMed Central

Power, Jonathan D; Plitt, Mark; Laumann, Timothy O; Martin, Alex

2016-01-01

Whole-brain fMRI signals are a subject of intense interest: variance in the global fMRI signal (the spatial mean of all signals in the brain) indexes subject arousal, and psychiatric conditions such as schizophrenia and autism have been characterized by differences in the global fMRI signal. Further, vigorous debates exist on whether global signals ought to be removed from fMRI data. However, surprisingly little research has focused on the empirical properties of whole-brain fMRI signals. Here we map the spatial and temporal properties of the global signal, individually, in 1000+ fMRI scans. Variance in the global fMRI signal is strongly linked to head motion, to hardware artifacts, and to respiratory patterns and their attendant physiologic changes. Many techniques used to prepare fMRI data for analysis fail to remove these uninteresting kinds of global signal fluctuations. Thus, many studies include, at the time of analysis, prominent global effects of yawns, breathing changes, and head motion, among other signals. Such artifacts will mimic dynamic neural activity and will spuriously alter signal covariance throughout the brain. Methods capable of isolating and removing global artifactual variance while preserving putative “neural” variance are needed; this paper adopts no position on the topic of global signal regression. PMID:27751941

Characteristic findings of magnetic resonance imaging (MRI) and computed tomography (CT) for severe chronic laminitis in a Thoroughbred horse

PubMed Central

YAMADA, Kazutaka; INUI, Tomohiro; ITOH, Megumi; YANAGAWA, Masashi; SATO, Fumio; TOMINARI, Masataka; MIZOBE, Fumiaki; KISHIMOTO, Miori; SASAKI, Naoki

2017-01-01

ABSTRACT A Thoroughbred horse with severe chronic laminitis of both forelimbs was evaluated on the same day with magnetic resonance imaging (MRI) and computed tomography (CT). Both MRI and CT revealed loss of the dorsal aspect of the cortical bone of the 3rd phalanx and sclerosis. CT reflected the status of the horny layer and bone of the affected feet, while MRI depicted inflammation of the laminar corium, together with tendon edema. On the 3-dimensional CT venogram, vessels were visualized in both the right and left forelimbs, although there was a difference in the vasculature of the coronary plexus and circumflex vessels between the right and left forelimbs. A combination of both MRI and CT provides detailed information regarding pathological conditions. PMID:28955162

Finite volume analysis of temperature effects induced by active MRI implants with cylindrical symmetry: 1. Properly working devices

PubMed Central

Busch, Martin HJ; Vollmann, Wolfgang; Schnorr, Jörg; Grönemeyer, Dietrich HW

2005-01-01

Background Active Magnetic Resonance Imaging implants are constructed as resonators tuned to the Larmor frequency of a magnetic resonance system with a specific field strength. The resonating circuit may be embedded into or added to the normal metallic implant structure. The resonators build inductively coupled wireless transmit and receive coils and can amplify the signal, normally decreased by eddy currents, inside metallic structures without affecting the rest of the spin ensemble. During magnetic resonance imaging the resonators generate heat, which is additional to the usual one described by the specific absorption rate. This induces temperature increases of the tissue around the circuit paths and inside the lumen of an active implant and may negatively influence patient safety. Methods This investigation provides an overview of the supplementary power absorbed by active implants with a cylindrical geometry, corresponding to vessel implants such as stents, stent grafts or vena cava filters. The knowledge of the overall absorbed power is used in a finite volume analysis to estimate temperature maps around different implant structures inside homogeneous tissue under worst-case assumptions. The "worst-case scenario" assumes thermal heat conduction without blood perfusion inside the tissue around the implant and mostly without any cooling due to blood flow inside vessels. Results The additional power loss of a resonator is proportional to the volume and the quality factor, as well as the field strength of the MRI system and the specific absorption rate of the applied sequence. For properly working devices the finite volume analysis showed only tolerable heating during MRI investigations in most cases. Only resonators transforming a few hundred mW into heat may reach temperature increases over 5 K. This requires resonators with volumes of several ten cubic centimeters, short inductor circuit paths with only a few 10 cm and a quality factor above ten. Using MR sequences, for which the MRI system manufacturer declares the highest specific absorption rate of 4 W/kg, vascular implants with a realistic construction, size and quality factor do not show temperature increases over a critical value of 5 K. Conclusion The results show dangerous heating for the assumed "worst-case scenario" only for constructions not acceptable for vascular implants. Realistic devices are safe with respect to temperature increases. However, this investigation discusses only properly working devices. Ruptures or partial ruptures of the wires carrying the electric current of the resonance circuits or other defects can set up a power source inside an extremely small volume. The temperature maps around such possible "hot spots" should be analyzed in an additional investigation. PMID:15819973

The power of using functional fMRI on small rodents to study brain pharmacology and disease

PubMed Central

Jonckers, Elisabeth; Shah, Disha; Hamaide, Julie; Verhoye, Marleen; Van der Linden, Annemie

2015-01-01

Functional magnetic resonance imaging (fMRI) is an excellent tool to study the effect of pharmacological modulations on brain function in a non-invasive and longitudinal manner. We introduce several blood oxygenation level dependent (BOLD) fMRI techniques, including resting state (rsfMRI), stimulus-evoked (st-fMRI), and pharmacological MRI (phMRI). Respectively, these techniques permit the assessment of functional connectivity during rest as well as brain activation triggered by sensory stimulation and/or a pharmacological challenge. The first part of this review describes the physiological basis of BOLD fMRI and the hemodynamic response on which the MRI contrast is based. Specific emphasis goes to possible effects of anesthesia and the animal’s physiological conditions on neural activity and the hemodynamic response. The second part of this review describes applications of the aforementioned techniques in pharmacologically induced, as well as in traumatic and transgenic disease models and illustrates how multiple fMRI methods can be applied successfully to evaluate different aspects of a specific disorder. For example, fMRI techniques can be used to pinpoint the neural substrate of a disease beyond previously defined hypothesis-driven regions-of-interest. In addition, fMRI techniques allow one to dissect how specific modifications (e.g., treatment, lesion etc.) modulate the functioning of specific brain areas (st-fMRI, phMRI) and how functional connectivity (rsfMRI) between several brain regions is affected, both in acute and extended time frames. Furthermore, fMRI techniques can be used to assess/explore the efficacy of novel treatments in depth, both in fundamental research as well as in preclinical settings. In conclusion, by describing several exemplary studies, we aim to highlight the advantages of functional MRI in exploring the acute and long-term effects of pharmacological substances and/or pathology on brain functioning along with several methodological considerations. PMID:26539115

Design of a 3T preamplifier which stability is insensitive to coil loading

NASA Astrophysics Data System (ADS)

Cao, Xueming; Fischer, Elmar; Korvink, Jan G.; Gruschke, Oliver; Hennig, Jürgen; Zaitsev, Maxim

2016-04-01

In MRI (magnetic resonance imaging), preamplifiers are needed to amplify signals obtained from MRI receiver coils. Under various loading conditions of the corresponding receiver coils, preamplifiers see different source impedance at their input and may become unstable. Therefore preamplifiers which stability is not sensitive to coil loading are desirable. In this article, a coil-loading-insensitive preamplifier for MRI is presented, derived from an unstable preamplifier. Different approaches to improve stability were used during this derivation. Since a very low noise factor is essential for MRI preamplifiers, noise contributions from passive components in the MRI preamplifier have to be considered during the stabilization process. As a result, the initially unstable preamplifier became stable with regard to coil loading, while other MRI requirements, as the extremely low noise factor, were still fulfilled. The newly designed preamplifier was manufactured, characterized and tested in the MRI spectrometer. Compared to a commercially available preamplifier, the newly designed preamplifier has similar imaging performance but other advantages like smaller size and better stability. Furthermore, presented stabilization approaches can be generalized to stabilize other unstable low-noise amplifiers.

An MRI-compatible platform for one-dimensional motion management studies in MRI.

PubMed

Nofiele, Joris; Yuan, Qing; Kazem, Mohammad; Tatebe, Ken; Torres, Quinn; Sawant, Amit; Pedrosa, Ivan; Chopra, Rajiv

2016-08-01

Abdominal MRI remains challenging because of respiratory motion. Motion compensation strategies are difficult to compare clinically because of the variability across human subjects. The goal of this study was to evaluate a programmable system for one-dimensional motion management MRI research. A system comprised of a programmable motorized linear stage and computer was assembled and tested in the MRI environment. Tests of the mutual interference between the platform and a whole-body MRI were performed. Organ trajectories generated from a high-temporal resolution scan of a healthy volunteer were used in phantom tests to evaluate the effects of motion on image quality and quantitative MRI measurements. No interference between the motion platform and the MRI was observed, and reliable motion could be produced across a wide range of imaging conditions. Motion-related artifacts commensurate with motion amplitude, frequency, and waveform were observed. T2 measurement of a kidney lesion in an abdominal phantom showed that its value decreased by 67% with physiologic motion, but could be partially recovered with navigator-based motion-compensation. The motion platform can produce reliable linear motion within a whole-body MRI. The system can serve as a foundation for a research platform to investigate and develop motion management approaches for MRI. Magn Reson Med 76:702-712, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Sparse and optimal acquisition design for diffusion MRI and beyond

PubMed Central

Koay, Cheng Guan; Özarslan, Evren; Johnson, Kevin M.; Meyerand, M. Elizabeth

2012-01-01

Purpose: Diffusion magnetic resonance imaging (MRI) in combination with functional MRI promises a whole new vista for scientists to investigate noninvasively the structural and functional connectivity of the human brain—the human connectome, which had heretofore been out of reach. As with other imaging modalities, diffusion MRI data are inherently noisy and its acquisition time-consuming. Further, a faithful representation of the human connectome that can serve as a predictive model requires a robust and accurate data-analytic pipeline. The focus of this paper is on one of the key segments of this pipeline—in particular, the development of a sparse and optimal acquisition (SOA) design for diffusion MRI multiple-shell acquisition and beyond. Methods: The authors propose a novel optimality criterion for sparse multiple-shell acquisition and quasimultiple-shell designs in diffusion MRI and a novel and effective semistochastic and moderately greedy combinatorial search strategy with simulated annealing to locate the optimum design or configuration. The goal of the optimality criteria is threefold: first, to maximize uniformity of the diffusion measurements in each shell, which is equivalent to maximal incoherence in angular measurements; second, to maximize coverage of the diffusion measurements around each radial line to achieve maximal incoherence in radial measurements for multiple-shell acquisition; and finally, to ensure maximum uniformity of diffusion measurement directions in the limiting case when all the shells are coincidental as in the case of a single-shell acquisition. The approach taken in evaluating the stability of various acquisition designs is based on the condition number and the A-optimal measure of the design matrix. Results: Even though the number of distinct configurations for a given set of diffusion gradient directions is very large in general—e.g., in the order of 10232 for a set of 144 diffusion gradient directions, the proposed search strategy was found to be effective in finding the optimum configuration. It was found that the square design is the most robust (i.e., with stable condition numbers and A-optimal measures under varying experimental conditions) among many other possible designs of the same sample size. Under the same performance evaluation, the square design was found to be more robust than the widely used sampling schemes similar to that of 3D radial MRI and of diffusion spectrum imaging (DSI). Conclusions: A novel optimality criterion for sparse multiple-shell acquisition and quasimultiple-shell designs in diffusion MRI and an effective search strategy for finding the best configuration have been developed. The results are very promising, interesting, and practical for diffusion MRI acquisitions. PMID:22559620

Self-Referential Processing of Negative Stimuli within the Ventral Anterior Cingulate Gyrus and Right Amygdala

ERIC Educational Resources Information Center

Yoshimura, Shinpei; Ueda, Kazutaka; Suzuki, Shin-ichi; Onoda, Keiichi; Okamoto, Yasumasa; Yamawaki, Shigeto

2009-01-01

Neural activity associated with self-referential processing of emotional stimuli was investigated using whole brain functional magnetic resonance imaging (fMRI). Fifteen healthy subjects underwent fMRI scanning while making judgments about positive and negative trait words in four conditions (self-reference, other-reference, semantic processing,…

Simultaneous PET/MR imaging of the brain: feasibility of cerebral blood flow measurements with FAIR-TrueFISP arterial spin labeling MRI.

PubMed

Stegger, Lars; Martirosian, Petros; Schwenzer, Nina; Bisdas, Sotirios; Kolb, Armin; Pfannenberg, Christina; Claussen, Claus D; Pichler, Bernd; Schick, Fritz; Boss, Andreas

2012-11-01

Hybrid positron emission tomography/magnetic resonance imaging (PET/MRI) with simultaneous data acquisition promises a comprehensive evaluation of cerebral pathophysiology on a molecular, anatomical, and functional level. Considering the necessary changes to the MR scanner design the feasibility of arterial spin labeling (ASL) is unclear. To evaluate whether cerebral blood flow imaging with ASL is feasible using a prototype PET/MRI device. ASL imaging of the brain with Flow-sensitive Alternating Inversion Recovery (FAIR) spin preparation and true fast imaging in steady precession (TrueFISP) data readout was performed in eight healthy volunteers sequentially on a prototype PET/MRI and a stand-alone MR scanner with 128 × 128 and 192 × 192 matrix sizes. Cerebral blood flow values for gray matter, signal-to-noise and contrast-to-noise ratios, and relative signal change were compared. Additionally, the feasibility of ASL as part of a clinical hybrid PET/MRI protocol was demonstrated in five patients with intracerebral tumors. Blood flow maps showed good delineation of gray and white matter with no discernible artifacts. The mean blood flow values of the eight volunteers on the PET/MR system were 51 ± 9 and 51 ± 7 mL/100 g/min for the 128 × 128 and 192 × 192 matrices (stand-alone MR, 57 ± 2 and 55 ± 5, not significant). The value for signal-to-noise (SNR) was significantly higher for the PET/MRI system using the 192 × 192 matrix size (P < 0.01), the relative signal change (δS) was significantly lower for the 192 × 192 matrix size (P = 0.02). ASL imaging as part of a clinical hybrid PET/MRI protocol could successfully be accomplished in all patients in diagnostic image quality. ASL brain imaging is feasible with a prototype hybrid PET/MRI scanner, thus adding to the value of this novel imaging technique.

Using Brain Imaging for Lie Detection: Where Science, Law and Research Policy Collide.

PubMed

Langleben, Daniel D; Moriarty, Jane Campbell

2013-05-01

Progress in the use of functional magnetic resonance imaging (fMRI) of the brain to evaluate deception and differentiate lying from truth-telling has created anticipation of a breakthrough in the search for technology-based methods of lie detection. In the last few years, litigants have attempted to introduce fMRI lie detection evidence in courts. This article weighs in on the interdisciplinary debate about the admissibility of such evidence, identifying the missing pieces of the scientific puzzle that need to be completed if fMRI-based lie detection is to meet the standards of either legal reliability or general acceptance. We believe that the Daubert's "known error rate" is the key concept linking the legal and scientific standards. We posit that properly-controlled clinical trials are the most convincing means to determine the error rates of fMRI-based lie detection and confirm or disprove the relevance of the promising laboratory research on this topic. This article explains the current state of the science and provides an analysis of the case law in which litigants have sought to introduce fMRI lie detection. Analyzing the myriad issues related to fMRI lie detection, the article identifies the key limitations of the current neuroimaging of deception science as expert evidence and explores the problems that arise from using scientific evidence before it is proven scientifically valid and reliable. We suggest that courts continue excluding fMRI lie detection evidence until this potentially useful form of forensic science meets the scientific standards currently required for adoption of a medical test or device. Given a multitude of stakeholders and, the charged and controversial nature and the potential societal impact of this technology, goodwill and collaboration of several government agencies may be required to sponsor impartial and comprehensive clinical trials that will guide the development of forensic fMRI technology.

Let's go out of the breast: prevalence of extra-mammary findings and their characterization on breast MRI.

PubMed

Moschetta, Marco; Telegrafo, Michele; Rella, Leonarda; Stabile Ianora, Amato Antonio; Angelelli, Giuseppe

2014-06-01

The aim of this study is to assess the prevalence, the site and the nature of extra-mammary findings on breast magnetic resonance imaging (MRI) and to determine its accuracy in the characterization of the discovered lesions. A retrospective review of 308 female patients (mean age 50 ± 20) who underwent breast MRI with 1.5T device was performed. 125 out of 308 (40.5%) had a positive personal history of breast cancer (pre-operative n=80; follow-up n=45), while the remaining 183 without history of breast cancer (high familiar risk for breast cancer n=80; dense breast n=103). All incidental findings were characterized by means of additional imaging (US; Bone scintigraphy-MRI; CT-PET-CT). 59 incidental findings were found in 53/308 (17%) examined patients. 9/59 incidental findings (15%) were confirmed to be malignant while the remaining 50/59 (84%) benign. The most common site was the liver (33/59; 55.8%), followed by the lung (6/59; 10.1%), bone (6/59; 10.1%), diaphragm (6/59; 10.1%) spleen (3/59; 5%), kidney (2/59; 3.4%), gall bladder (1/5; 1.5%), ascending aorta (1/59; 1.5%), thyroid (1/59; 1.5%). The incidence of malignant incidental findings resulted to be higher in the group of patients with personal breast cancer (36%) than in the other one (8%). By comparing MRI findings with the additional definitive imaging tools, breast MRI allowed a correct diagnosis in 58/59 cases with a diagnostic accuracy value of 98%. Incidental extramammary findings on breast MRI are common. Benign lesions represent the most frequent findings, however malignant ones need to be searched especially in patients with personal history of breast cancer because they could influence the clinical patient management. Breast MRI can characterize incidental findings with high accuracy value. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Using Brain Imaging for Lie Detection: Where Science, Law and Research Policy Collide

PubMed Central

Langleben, Daniel D.; Moriarty, Jane Campbell

2012-01-01

Progress in the use of functional magnetic resonance imaging (fMRI) of the brain to evaluate deception and differentiate lying from truth-telling has created anticipation of a breakthrough in the search for technology-based methods of lie detection. In the last few years, litigants have attempted to introduce fMRI lie detection evidence in courts. This article weighs in on the interdisciplinary debate about the admissibility of such evidence, identifying the missing pieces of the scientific puzzle that need to be completed if fMRI-based lie detection is to meet the standards of either legal reliability or general acceptance. We believe that the Daubert’s “known error rate” is the key concept linking the legal and scientific standards. We posit that properly-controlled clinical trials are the most convincing means to determine the error rates of fMRI-based lie detection and confirm or disprove the relevance of the promising laboratory research on this topic. This article explains the current state of the science and provides an analysis of the case law in which litigants have sought to introduce fMRI lie detection. Analyzing the myriad issues related to fMRI lie detection, the article identifies the key limitations of the current neuroimaging of deception science as expert evidence and explores the problems that arise from using scientific evidence before it is proven scientifically valid and reliable. We suggest that courts continue excluding fMRI lie detection evidence until this potentially useful form of forensic science meets the scientific standards currently required for adoption of a medical test or device. Given a multitude of stakeholders and, the charged and controversial nature and the potential societal impact of this technology, goodwill and collaboration of several government agencies may be required to sponsor impartial and comprehensive clinical trials that will guide the development of forensic fMRI technology. PMID:23772173

fMRI neurofeedback of amygdala response to aversive stimuli enhances prefrontal-limbic brain connectivity.

PubMed

Paret, Christian; Ruf, Matthias; Gerchen, Martin Fungisai; Kluetsch, Rosemarie; Demirakca, Traute; Jungkunz, Martin; Bertsch, Katja; Schmahl, Christian; Ende, Gabriele

2016-01-15

Down-regulation of the amygdala with real-time fMRI neurofeedback (rtfMRI NF) potentially allows targeting brain circuits of emotion processing and may involve prefrontal-limbic networks underlying effective emotion regulation. Little research has been dedicated to the effect of rtfMRI NF on the functional connectivity of the amygdala and connectivity patterns in amygdala down-regulation with neurofeedback have not been addressed yet. Using psychophysiological interaction analysis of fMRI data, we present evidence that voluntary amygdala down-regulation by rtfMRI NF while viewing aversive pictures was associated with increased connectivity of the right amygdala with the ventromedial prefrontal cortex (vmPFC) in healthy subjects (N=16). In contrast, a control group (N=16) receiving sham feedback did not alter amygdala connectivity (Group×Condition t-contrast: p<.05 at cluster-level). Task-dependent increases in amygdala-vmPFC connectivity were predicted by picture arousal (β=.59, p<.05). A dynamic causal modeling analysis with Bayesian model selection aimed at further characterizing the underlying causal structure and favored a bottom-up model assuming predominant information flow from the amygdala to the vmPFC (xp=.90). The results were complemented by the observation of task-dependent alterations in functional connectivity of the vmPFC with the visual cortex and the ventrolateral PFC in the experimental group (Condition t-contrast: p<.05 at cluster-level). Taken together, the results underscore the potential of amygdala fMRI neurofeedback to influence functional connectivity in key networks of emotion processing and regulation. This may be beneficial for patients suffering from severe emotion dysregulation by improving neural self-regulation. Copyright © 2015 Elsevier Inc. All rights reserved.

RF HEATING OF MRI-ASSISTED CATHETER STEERING COILS FOR INTERVENTIONAL MRI

PubMed Central

Settecase, Fabio; Hetts, Steven W.; Martin, Alastair J.; Roberts, Timothy P. L.; Bernhardt, Anthony F.; Evans, Lee; Malba, Vincent; Saeed, Maythem; Arenson, Ronald L.; Kucharzyk, Walter; Wilson, Mark W.

2010-01-01

RATIONALE AND OBJECTIVES To assess magnetic resonance imaging (MRI) radiofrequency (RF) related heating of conductive wire coils used in magnetically steerable endovascular catheters. MATERIALS AND METHODS A 3-axis microcoil was fabricated onto a 1.8 Fr catheter tip. In vitro testing was performed in a 1.5 T MRI system using an agarose gel filled vessel phantom, a transmit/receive body RF coil and a steady state free precession (SSFP) pulse sequence, and a fluoroptic thermometry system. Temperature was measured without simulated blood flow at varying distances from magnet isocenter and varying flip angles. Additional experiments were performed with laser-lithographed single-axis microcoil-tipped microcatheters in air and in a saline bath with varied grounding of the microcoil wires. Preliminary in vivo evaluation of RF heating was performed in pigs at 1.5 T with coil-tipped catheters in various positions in the common carotid arteries with SSFP pulse sequence on and off, and under physiologic flow and zero flow conditions. RESULTS In tissue-mimicking agarose gel, RF heating resulted in a maximal temperature increase of 0.35°C after 15 minutes of imaging, 15 cm from magnet isocenter. For a single axis microcoil, maximal temperature increases were 0.73-1.91°C in air and 0.45-0.55°C in saline. In vivo, delayed contrast enhanced MRI revealed no evidence of vascular injury and histopathological sections from the common carotid arteries confirmed the lack of vascular damage. CONCLUSIONS Microcatheter tip microcoils for endovascular catheter steering in MRI experience minimal RF heating under the conditions tested. These data provide the basis for further in vivo testing of this promising technology for endovascular interventional MRI. PMID:21075019

MRI-based comparative study of different mild cognitive impairment subtypes: protocol for an observational case-control study.

PubMed

Yu, Yang; Zhao, Weina; Li, Siou; Yin, Changhao

2017-03-08

Amnestic mild cognitive impairment (aMCI) and vascular mild cognitive impairment (VaMCI) comprise the 2 main types of mild cognitive impairment (MCI). The first condition generally progresses to Alzheimer's disease, whereas the second is likely to develop into vascular dementia (VD). The brain structure and function of patients with MCI differ from those of normal elderly individuals. However, whether brain structures or functions differ between these 2 MCI subtypes has not been studied. This study is designed to analyse neuroimages of brain in patients with VaMCI and aMCI using multimodality MRI (structural MRI (sMRI), functional MRI and diffusion tensor imaging (DTI)). In this study, 80 participants diagnosed with aMCI, 80 participants diagnosed with VaMCI, and 80 age-matched, gender-matched and education-matched normal controls (NCs) will be recruited to the Hongqi Hospital of Mudanjiang Medical University, Heilongjiang, China. All participants will undergo neuroimaging and neuropsychological evaluations. The primary outcome measures will be (1) microstructural alterations revealed by multimodal MRIs, including sMRI, resting-state functional MRI and DTI; and (2) a neuropsychological evaluation, including the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Auditory Verbal Learning Test (AVLT), Memory and Executive Screening (MES), trail making test, Stroop colour naming condition and Clinical Dementia Rating (CDR) scale, to evaluate global cognition, memory function, attention, visuospatial skills, processing speed, executive function and emotion, respectively. NCT02706210; Pre-results. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Evaluation of a signal intensity mask in the interpretation of functional MR imaging activation maps.

PubMed

Strigel, Roberta M; Moritz, Chad H; Haughton, Victor M; Badie, Behnam; Field, Aaron; Wood, David; Hartman, Michael; Rowley, Howard A

2005-03-01

The purpose of this study was to determine the incidence of susceptibility artifacts on functional MR imaging (fMRI) studies and their effect on fMRI readings. We hypothesized that the availability of the signal intensity maps (SIMs) changes the interpretation of fMRI studies in which susceptibility artifacts affected eloquent brain regions. We reviewed 152 consecutive clinical fMRI studies performed with a SIM. The SIM consisted of the initial echo-planar images (EPI) in each section thresholded to eliminate signal intensity from outside the brain and then overlaid on anatomic images. The cause of the artifact was then determined by examining the images. Cases with a susceptibility artifact in eloquent brain were included in a blinded study read by four readers, first without and then with the SIM. For each reader, the number of times the interpretation changed on viewing the SIM was counted. Of 152 patients, 44% had signal intensity loss involving cerebral cortex and 18% involving an eloquent brain region. Causes of the artifacts were: surgical site artifact, blood products, dental devices, calcium, basal ganglia calcifications, ICP monitors, embolization materials, and air. When provided with the SIM, readers changed interpretations in 8-38% of patient cases, depending on reader experience and size and location of susceptibility artifact. Patients referred for clinical fMRI have a high incidence of susceptibility artifacts, whose presence and size can be determined by inspection of the SIM but not anatomic images. The availability of the SIM may affect interpretation of the fMRI.

Targeted endomyocardial injections of therapeutic cells using x-ray fused with MRI guidance

NASA Astrophysics Data System (ADS)

Gutiérrez, Luis F.; de Silva, Ranil; McVeigh, Elliot R.; Ozturk, Cengizhan; Lederman, Robert J.

2006-03-01

The utility of X-ray fused with MRI (XFM) using external fiducial markers to perform targeted endomyocardial injections in infarcted hearts of swine was tested. Endomyocardial injections of feridex-labeled mesenchymal stromal cells (Fe-MSC) were performed in the previously infarcted hearts of 12 Yucatan miniswine (33-67 kg). Animals had pre-injection cardiac MRI, XFM-guided endomyocardial injection of Fe-MSC suspension spiked with tissue dye, and post-injection MRI. 24 hours later, after euthanasia, the hearts were excised, sliced and stained with TTC. During the injection procedure, operators were provided with 3D surfaces of endocardium, epicardium, myocardial wall thickness and infarct registered with live XF images to facilitate device navigation and choice of injection location. 130 injections were performed in hearts where diastolic wall thickness ranged from 2.6 to 17.7 mm. Visual inspection of the pattern of dye staining on TTC stained heart slices correlated (r=0.98) with XFM-derived injection locations mapped onto delayed hyperenhancement MRI and the susceptibility artifacts seen on the post-injection T2*-weighted gradient echo MRI. The in vivo target registration error was 3.17+/-2.61 mm (n=64) and 75% of injections were within 4 mm of the predicted location. 3D to 2D registration of XF and MR images using external fiducial markers enables accurate targeted endomyocardial injection in a swine model of myocardial infarction. The present data suggest that the safety and efficacy of this approach for performing targeted endomyocardial delivery should be evaluated further clinically.

Investigating the neural correlates of smoking: Feasibility and results of combining electronic cigarettes with fMRI.

PubMed

Wall, Matthew B; Mentink, Alexander; Lyons, Georgina; Kowalczyk, Oliwia S; Demetriou, Lysia; Newbould, Rexford D

2017-09-12

Cigarette addiction is driven partly by the physiological effects of nicotine, but also by the distinctive sensory and behavioural aspects of smoking, and understanding the neural effects of such processes is vital. There are many practical difficulties associated with subjects smoking in the modern neuroscientific laboratory environment, however electronic cigarettes obviate many of these issues, and provide a close simulation of smoking tobacco cigarettes. We have examined the neural effects of 'smoking' electronic cigarettes with concurrent functional Magnetic Resonance Imaging (fMRI). The results demonstrate the feasibility of using these devices in the MRI environment, and show brain activation in a network of cortical (motor cortex, insula, cingulate, amygdala) and sub-cortical (putamen, thalamus, globus pallidus, cerebellum) regions. Concomitant relative deactivations were seen in the ventral striatum and orbitofrontal cortex. These results reveal the brain processes involved in (simulated) smoking for the first time, and validate a novel approach to the study of smoking, and addiction more generally.

Liquid-state carbon-13 hyperpolarization generated in an MRI system for fast imaging

PubMed Central

Schmidt, A. B.; Berner, S.; Schimpf, W.; Müller, C.; Lickert, T.; Schwaderlapp, N.; Knecht, S.; Skinner, J. G.; Dost, A.; Rovedo, P.; Hennig, J.; von Elverfeldt, D.; Hövener, J. -B.

2017-01-01

Hyperpolarized (HP) tracers dramatically increase the sensitivity of magnetic resonance imaging (MRI) to monitor metabolism non-invasively and in vivo. Their production, however, requires an extra polarizing device (polarizer) whose complexity, operation and cost can exceed that of an MRI system itself. Furthermore, the lifetime of HP tracers is short and some of the enhancement is lost during transfer to the application site. Here, we present the production of HP tracers in water without an external polarizer: by Synthesis Amid the Magnet Bore, A Dramatically Enhanced Nuclear Alignment (SAMBADENA) is achieved within seconds, corresponding to a hyperpolarization of ∼20%. As transfer of the tracer is no longer required, SAMBADENA may permit a higher polarization at the time of detection at a fraction of the cost and complexity of external polarizers. This development is particularly promising in light of the recently extended portfolio of biomedically relevant para-hydrogen-tracers and may lead to new diagnostic applications. PMID:28262691

Simulation of arthroscopic surgery using MRI data

NASA Technical Reports Server (NTRS)

Heller, Geoffrey; Genetti, Jon

1994-01-01

With the availability of Magnetic Resonance Imaging (MRI) technology in the medical field and the development of powerful graphics engines in the computer world the possibility now exists for the simulation of surgery using data obtained from an actual patient. This paper describes a surgical simulation system which will allow a physician or a medical student to practice surgery on a patient without ever entering an operating room. This could substantially lower the cost of medial training by providing an alternative to the use of cadavers. This project involves the use of volume data acquired by MRI which are converted to polygonal form using a corrected marching cubes algorithm. The data are then colored and a simulation of surface response based on springy structures is performed in real time. Control for the system is obtained through the use of an attached analog-to-digital unit. A remote electronic device is described which simulates an imaginary tool having features in common with both arthroscope and laparoscope.

Finite element analysis of gradient z-coil induced eddy currents in a permanent MRI magnet.

PubMed

Li, Xia; Xia, Ling; Chen, Wufan; Liu, Feng; Crozier, Stuart; Xie, Dexin

2011-01-01

In permanent magnetic resonance imaging (MRI) systems, pulsed gradient fields induce strong eddy currents in the conducting structures of the magnet body. The gradient field for image encoding is perturbed by these eddy currents leading to MR image distortions. This paper presents a comprehensive finite element (FE) analysis of the eddy current generation in the magnet conductors. In the proposed FE model, the hysteretic characteristics of ferromagnetic materials are considered and a scalar Preisach hysteresis model is employed. The developed FE model was applied to study gradient z-coil induced eddy currents in a 0.5 T permanent MRI device. The simulation results demonstrate that the approach could be effectively used to investigate eddy current problems involving ferromagnetic materials. With the knowledge gained from this eddy current model, our next step is to design a passive magnet structure and active gradient coils to reduce the eddy current effects. Copyright © 2010 Elsevier Inc. All rights reserved.

Diagnosis of deep endometriosis: clinical examination, ultrasonography, magnetic resonance imaging, and other techniques.

PubMed

Bazot, Marc; Daraï, Emile

2017-12-01

The aim of the present review was to evaluate the contribution of clinical examination and imaging techniques, mainly transvaginal sonography and magnetic resonance imaging (MRI) to diagnose deep infiltrating (DE) locations using prisma statement recommendations. Clinical examination has a relative low sensitivity and specificity to diagnose DE. Independently of DE locations, for all transvaginal sonography techniques a pooled sensitivity and specificity of 79% and 94% are observed approaching criteria for a triage test. Whatever the protocol and MRI devices, the pooled sensitivity and specificity for pelvic endometriosis diagnosis were 94% and 77%, respectively. For rectosigmoid endometriosis, pooled sensitivity and specificity of MRI were 92% and 96%, respectively fulfilling criteria of replacement test. In conclusion, advances in imaging techniques offer high sensitivity and specificity to diagnose DE with at least triage value and for rectosigmoid endometriosis replacement value imposing a revision of the concept of laparoscopy as the gold standard. Copyright © 2017 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

Characterization of thalamocortical association using amplitude and connectivity of fMRI in mild traumatic brain injury

PubMed Central

Zhou, Yongxia; Lui, Yvonne W; Zuo, Xi-Nian; Milham, Michael P.; Reaume, Joseph; Grossman, Robert I.; Ge, Yulin

2013-01-01

Purpose To examine thalamic and cortical injuries using fractional amplitude of low-frequency fluctuations (fALFF) and functional connectivity MRI (fcMRI) based on resting state (RS) and task-related fMRI in patients with mild traumatic brain injury (MTBI). Materials and Methods Twenty-seven patients and 27 age-matched controls were recruited. 3T fMRI at RS and finger tapping task were used to assess fALFF and fcMRI patterns. fALFF was computed with filtering (0.01-0.08Hz) and scaling after preprocessing. fcMRI was performed using a standard seed-based correlation method, and delayed fcMRI (coherence) in frequency domain were also performed between thalamus and cortex. Results In comparison with controls, MTBI patients exhibited significantly decreased fALFF in the thalamus (and frontal/temporal sub segments) and cortical frontal and temporal lobes; as well as decreased thalamo-thalamo and thalamo-frontal/thalamo-temporal fcMRI at rest based on RS-fMRI (corrected P<0.05). This thalamic and cortical disruption also existed at task-related condition in patients. Conclusion The decreased fALFF (i.e. lower neuronal activity) in the thalamus and its segments provides additional evidence of thalamic injury in patients with MTBI. Our findings of fALFF and fcMRI changes during motor task and resting state may offer insights into the underlying cause and primary location of disrupted thalamo-cortical networks after MTBI. PMID:24014176

MRI-based decision tree model for diagnosis of biliary atresia.

PubMed

Kim, Yong Hee; Kim, Myung-Joon; Shin, Hyun Joo; Yoon, Haesung; Han, Seok Joo; Koh, Hong; Roh, Yun Ho; Lee, Mi-Jung

2018-02-23

To evaluate MRI findings and to generate a decision tree model for diagnosis of biliary atresia (BA) in infants with jaundice. We retrospectively reviewed features of MRI and ultrasonography (US) performed in infants with jaundice between January 2009 and June 2016 under approval of the institutional review board, including the maximum diameter of periportal signal change on MRI (MR triangular cord thickness, MR-TCT) or US (US-TCT), visibility of common bile duct (CBD) and abnormality of gallbladder (GB). Hepatic subcapsular flow was reviewed on Doppler US. We performed conditional inference tree analysis using MRI findings to generate a decision tree model. A total of 208 infants were included, 112 in the BA group and 96 in the non-BA group. Mean age at the time of MRI was 58.7 ± 36.6 days. Visibility of CBD, abnormality of GB and MR-TCT were good discriminators for the diagnosis of BA and the MRI-based decision tree using these findings with MR-TCT cut-off 5.1 mm showed 97.3 % sensitivity, 94.8 % specificity and 96.2 % accuracy. MRI-based decision tree model reliably differentiates BA in infants with jaundice. MRI can be an objective imaging modality for the diagnosis of BA. • MRI-based decision tree model reliably differentiates biliary atresia in neonatal cholestasis. • Common bile duct, gallbladder and periportal signal changes are the discriminators. • MRI has comparable performance to ultrasonography for diagnosis of biliary atresia.

Effects of nonspatial selective and divided visual attention on fMRI BOLD responses.

PubMed

Weerda, Riklef; Vallines, Ignacio; Thomas, James P; Rutschmann, Roland M; Greenlee, Mark W

2006-09-01

Using an uncertainty paradigm and functional magnetic resonance imaging (fMRI) we studied the effect of nonspatial selective and divided visual attention on the activity of specific areas of human extrastriate visual cortex. The stimuli were single ovals that differed from an implicit standard oval in either colour or width. The subjects' task was to classify the current stimulus as one of two possible alternatives per stimulus dimension. Three different experimental conditions were conducted: "colour-certainty", "shape-certainty" and "uncertainty". In all experimental conditions, the stimulus differed in only one stimulus dimension per trial. In the two certainty conditions, the subjects knew in advance which dimension this would be. During the uncertainty condition they had no such previous knowledge and had to monitor both dimensions simultaneously. Statistical analysis of the fMRI data (with SPM2) revealed a modest effect of the attended stimulus dimension on the neural activity in colour sensitive area V4 (more activity during attention to colour) and in shape sensitive area LOC (more activity during attention to shape). Furthermore, cortical areas known to be related to attention and working memory processes (e.g., lateral prefrontal and posterior parietal cortex) exhibit higher activity during the condition of divided attention ("uncertainty") than during that of selective attention ("certainty").

Task-specific Aspects of Goal-directed Word Generation Identified via Simultaneous EEG-fMRI.

PubMed

Shapira-Lichter, Irit; Klovatch, Ilana; Nathan, Dana; Oren, Noga; Hendler, Talma

2016-09-01

Generating words according to a given rule relies on retrieval-related search and postretrieval control processes. Using fMRI, we recently characterized neural patterns of word generation in response to episodic, semantic, and phonemic cues by comparing free recall of wordlists, category fluency, and letter fluency [Shapira-Lichter, I., Oren, N., Jacob, Y., Gruberger, M., & Hendler, T. Portraying the unique contribution of the default mode network to internally driven mnemonic processes. Proceedings of the National Academy of Sciences, U.S.A., 110, 4950-4955, 2013]. Distinct selectivity for each condition was evident, representing discrete aspects of word generation-related memory retrieval. For example, the precuneus, implicated in processing spatiotemporal information, emerged as a key contributor to the episodic condition, which uniquely requires this information. Gamma band is known to play a central role in memory, and increased gamma power has been observed before word generation. Yet, gamma modulation in response to task demands has not been investigated. To capture the task-specific modulation of gamma power, we analyzed the EEG data recorded simultaneously with the aforementioned fMRI, focusing on the activity locked to and immediately preceding word articulation. Transient increases in gamma power were identified in a parietal electrode immediately before episodic and semantic word generation, however, within a different time frame relative to articulation. Gamma increases were followed by an alpha-theta decrease in the episodic condition, a gamma decrease in the semantic condition. This pattern indicates a task-specific modulation of the gamma signal corresponding to the specific demands of each word generation task. The gamma power and fMRI signal from the precuneus were correlated during the episodic condition, implying the existence of a common cognitive construct uniquely required for this task, possibly the reactivation or processing of spatiotemporal information.

Effect of intra-articular administration of superparamagnetic iron oxide nanoparticles (SPIONs) for MRI assessment of the cartilage barrier in a large animal model

PubMed Central

Hall, Sarah; Xia, Xin-Rui; Schwarz, Tobias

2017-01-01

Early diagnosis of cartilage disease at a time when changes are limited to depletion of extracellular matrix components represents an important diagnostic target to reduce patient morbidity. This report is to present proof of concept for nanoparticle dependent cartilage barrier imaging in a large animal model including the use of clinical magnetic resonance imaging (MRI). Conditioned (following matrix depletion) and unconditioned porcine metacarpophalangeal cartilage was evaluated on the basis of fluorophore conjugated 30 nm and 80 nm spherical gold nanoparticle permeation and multiphoton laser scanning and bright field microscopy after autometallographic particle enhancement. Consequently, conditioned and unconditioned joints underwent MRI pre- and post-injection with 12 nm superparamagnetic iron oxide nanoparticles (SPIONs) to evaluate particle permeation in the context of matrix depletion and use of a clinical 1.5 Tesla MRI scanner. To gauge the potential pro-inflammatory effect of intra-articular nanoparticle delivery co-cultures of equine synovium and cartilage tissue were exposed to an escalating dose of SPIONs and IL-6, IL-10, IFN-γ and PGE2 were assessed in culture media. The chemotactic potential of growth media samples was subsequently assessed in transwell migration assays on isolated equine neutrophils. Results demonstrate an increase in MRI signal following conditioning of porcine joints which suggests that nanoparticle dependent compositional cartilage imaging is feasible. Tissue culture and neutrophil migration assays highlight a dose dependent inflammatory response following SPION exposure which at the imaging dose investigated was not different from controls. The preliminary safety and imaging data support the continued investigation of nanoparticle dependent compositional cartilage imaging. To our knowledge, this is the first report in using SPIONs as intra-articular MRI contrast agent for studying cartilage barrier function, which could potentially lead to a new diagnostic technique for early detection of cartilage disease. PMID:29287105

Prosepective Study to Evaluate Rate and Frequency of Perturbations of Implanted Programmable Hakim Codman Valve After 1.5-Tesla Magnetic Resonance Imaging.

PubMed

Capitanio, Jody Filippo; Venier, Alice; Mazzeo, Lucio Aniello; Barzaghi, Lina Raffaella; Acerno, Stefania; Mortini, Pietro

2016-04-01

Exposure to magnetic fields may alter the settings of programmable ventriculoperitoneal shunt valves or even cause permanent damages to these devices. There is little information about this topic, none on live patients. To investigate the effects of 1.5-tesla magnetic resonance imaging (MRI) on Hakim-Codman (HC) pressure programmable valves implanted in our hospital. A single-center prospective study to assess the rate of perturbations of HC programmable valve implanted. One hundred consecutive patients implanted for different clinical reasons between 2008 and 2012 were examined. A conventional skull x-ray before and after a standard MRI on 1.5 tesla. We evaluated before and after results, analyzed modification rate, and verified eventual damages to the implanted devices. Implanted HC valves are extremely handy and durable, even if they are likely to change often due to the exposure to magnetic fields. None of the patients complained of heating effects. Oscillations range from 10-30 mm H2O with a patient who reached 50 mm H2O and 1 who reached 60 mm H2O. Global alteration rate was 40%: 10 patients (10%) experienced a 10 mm H2O change; 14 patients (14%) had a 20 mm H2O change; 6 patients (6%) had a 30 mm H2O change; 8 patients (8%) had a 40 mm H2O change; 1 patient had a 50 mm H2O change; and 1 patient had a 60 mm H2O change. HC valves presented a variable perturbation rate, with an alteration rate of 40% with 1.5-telsa MRI. We have not observed malfunctioning hardware as a result of magnetic influence. We claim ​ a cranial x-ray immediately after the MRI because of a high risk (40%) of decalibration, especially in patients with low ventricles compliance. Copyright © 2016 Elsevier Inc. All rights reserved.

Effect of color visualization and display hardware on the visual assessment of pseudocolor medical images

PubMed Central

Zabala-Travers, Silvina; Choi, Mina; Cheng, Wei-Chung

2015-01-01

Purpose: Even though the use of color in the interpretation of medical images has increased significantly in recent years, the ad hoc manner in which color is handled and the lack of standard approaches have been associated with suboptimal and inconsistent diagnostic decisions with a negative impact on patient treatment and prognosis. The purpose of this study is to determine if the choice of color scale and display device hardware affects the visual assessment of patterns that have the characteristics of functional medical images. Methods: Perfusion magnetic resonance imaging (MRI) was the basis for designing and performing experiments. Synthetic images resembling brain dynamic-contrast enhanced MRI consisting of scaled mixtures of white, lumpy, and clustered backgrounds were used to assess the performance of a rainbow (“jet”), a heated black-body (“hot”), and a gray (“gray”) color scale with display devices of different quality on the detection of small changes in color intensity. The authors used a two-alternative, forced-choice design where readers were presented with 600 pairs of images. Each pair consisted of two images of the same pattern flipped along the vertical axis with a small difference in intensity. Readers were asked to select the image with the highest intensity. Three differences in intensity were tested on four display devices: a medical-grade three-million-pixel display, a consumer-grade monitor, a tablet device, and a phone. Results: The estimates of percent correct show that jet outperformed hot and gray in the high and low range of the color scales for all devices with a maximum difference in performance of 18% (confidence intervals: 6%, 30%). Performance with hot was different for high and low intensity, comparable to jet for the high range, and worse than gray for lower intensity values. Similar performance was seen between devices using jet and hot, while gray performance was better for handheld devices. Time of performance was shorter with jet. Conclusions: Our findings demonstrate that the choice of color scale and display hardware affects the visual comparative analysis of pseudocolor images. Follow-up studies in clinical settings are being considered to confirm the results with patient images. PMID:26127048

Prostate cancer localization with multispectral MRI using cost-sensitive support vector machines and conditional random fields.

PubMed

Artan, Yusuf; Haider, Masoom A; Langer, Deanna L; van der Kwast, Theodorus H; Evans, Andrew J; Yang, Yongyi; Wernick, Miles N; Trachtenberg, John; Yetik, Imam Samil

2010-09-01

Prostate cancer is a leading cause of cancer death for men in the United States. Fortunately, the survival rate for early diagnosed patients is relatively high. Therefore, in vivo imaging plays an important role for the detection and treatment of the disease. Accurate prostate cancer localization with noninvasive imaging can be used to guide biopsy, radiotherapy, and surgery as well as to monitor disease progression. Magnetic resonance imaging (MRI) performed with an endorectal coil provides higher prostate cancer localization accuracy, when compared to transrectal ultrasound (TRUS). However, in general, a single type of MRI is not sufficient for reliable tumor localization. As an alternative, multispectral MRI, i.e., the use of multiple MRI-derived datasets, has emerged as a promising noninvasive imaging technique for the localization of prostate cancer; however almost all studies are with human readers. There is a significant inter and intraobserver variability for human readers, and it is substantially difficult for humans to analyze the large dataset of multispectral MRI. To solve these problems, this study presents an automated localization method using cost-sensitive support vector machines (SVMs) and shows that this method results in improved localization accuracy than classical SVM. Additionally, we develop a new segmentation method by combining conditional random fields (CRF) with a cost-sensitive framework and show that our method further improves cost-sensitive SVM results by incorporating spatial information. We test SVM, cost-sensitive SVM, and the proposed cost-sensitive CRF on multispectral MRI datasets acquired from 21 biopsy-confirmed cancer patients. Our results show that multispectral MRI helps to increase the accuracy of prostate cancer localization when compared to single MR images; and that using advanced methods such as cost-sensitive SVM as well as the proposed cost-sensitive CRF can boost the performance significantly when compared to SVM.

MRI and arthroscopy correlations of the elbow: a case-based approach.

PubMed

Abrams, Geoffrey D; Stoller, David W; Safran, Marc R

2012-01-01

The number of elbow arthroscopies and indications for the procedure have increased significantly since the advent of modern elbow arthroscopy in the 1980s. In addition to the patient history, physical examination, and plain radiography, MRI is an important tool for the clinician in diagnosing several pathologies within and around the elbow. Understanding the pathophysiology and clinical presentation and being familiar with the MRI characteristics of a variety of elbow conditions will assist the physician in making an accurate diagnosis and help guide appropriate treatment.

Numerical predictions of hemodynamics following surgeries in cerebral aneurysms

NASA Astrophysics Data System (ADS)

Rayz, Vitaliy; Lawton, Michael; Boussel, Loic; Leach, Joseph; Acevedo, Gabriel; Halbach, Van; Saloner, David

2014-11-01

Large cerebral aneurysms present a danger of rupture or brain compression. In some cases, clinicians may attempt to change the pathological hemodynamics in order to inhibit disease progression. This can be achieved by changing the vascular geometry with an open surgery or by deploying a stent-like flow diverter device. Patient-specific CFD models can help evaluate treatment options by predicting flow regions that are likely to become occupied by thrombus (clot) following the procedure. In this study, alternative flow scenarios were modeled for several patients who underwent surgical treatment. Patient-specific geometries and flow boundary conditions were obtained from magnetic resonance angiography and velocimetry data. The Navier-Stokes equations were solved with a finite volume solver Fluent. A porous media approach was used to model flow-diverter devices. The advection-diffusion equation was solved in order to simulate contrast agent transport and the results were used to evaluate flow residence time changes. Thrombus layering was predicted in regions characterized by reduced velocities and shear stresses as well as increased flow residence time. The simulations indicated surgical options that could result in occlusion of vital arteries with thrombus. Numerical results were compared to experimental and clinical MRI data. The results demonstrate that image-based CFD models may help improve the outcome of surgeries in cerebral aneurysms. acknowledge R01HL115267.

Diagnostic concordance between mobile interfaces and conventional workstations for emergency imaging assessment.

PubMed

Venson, José Eduardo; Bevilacqua, Fernando; Berni, Jean; Onuki, Fabio; Maciel, Anderson

2018-05-01

Mobile devices and software are now available with sufficient computing power, speed and complexity to allow for real-time interpretation of radiology exams. In this paper, we perform a multivariable user study that investigates concordance of image-based diagnoses provided using mobile devices on the one hand and conventional workstations on the other hand. We performed a between-subjects task-analysis using CT, MRI and radiography datasets. Moreover, we investigated the adequacy of the screen size, image quality, usability and the availability of the tools necessary for the analysis. Radiologists, members of several teams, participated in the experiment under real work conditions. A total of 64 studies with 93 main diagnoses were analyzed. Our results showed that 56 cases were classified with complete concordance (87.69%), 5 cases with almost complete concordance (7.69%) and 1 case (1.56%) with partial concordance. Only 2 studies presented discordance between the reports (3.07%). The main reason to explain the cause of those disagreements was the lack of multiplanar reconstruction tool in the mobile viewer. Screen size and image quality had no direct impact on the mobile diagnosis process. We concluded that for images from emergency modalities, a mobile interface provides accurate interpretation and swift response, which could benefit patients' healthcare. Copyright © 2018 Elsevier B.V. All rights reserved.

76 FR 31965 - Medical Devices; Availability of Safety and Effectiveness Summaries for Premarket Approval...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-02

.... ENDURANT STENT GRAFT SYSTEM. FDA-2011-M-0040 P100010 Medtronic Cryocath, ARCTIC FRONT December 17, 2010. LP.... Vascular. LX VASCULAR STENT SYSTEMS. FDA-2011-M-0039 P070026 Depuy, Inc......... CERAMAX CERAMIC HIP.... EXPANDABLE RENAL STENT SYSTEM. FDA-2011-M-0056 P090013 Medtronic, Inc..... REVO MRI SURESCAN IPG February 8...

Competitive Advantage of PET/MRI

PubMed Central

Jadvar, Hossein; Colletti, Patrick M.

2013-01-01

Multimodality imaging has made great strides in the imaging evaluation of patients with a variety of diseases. Positron emission tomography/computed tomography (PET/CT) is now established as the imaging modality of choice in many clinical conditions, particularly in oncology. While the initial development of combined PET/magnetic resonance imaging (PET/MRI) was in the preclinical arena, hybrid PET/MR scanners are now available for clinical use. PET/MRI combines the unique features of MRI including excellent soft tissue contrast, diffusion-weighted imaging, dynamic contrast-enhanced imaging, fMRI and other specialized sequences as well as MR spectroscopy with the quantitative physiologic information that is provided by PET. Most evidence for the potential clinical utility of PET/MRI is based on studies performed with side-by-side comparison or software-fused MRI and PET images. Data on distinctive utility of hybrid PET/MRI are rapidly emerging. There are potential competitive advantages of PET/MRI over PET/CT. In general, PET/MRI may be preferred over PET/CT where the unique features of MRI provide more robust imaging evaluation in certain clinical settings. The exact role and potential utility of simultaneous data acquisition in specific research and clinical settings will need to be defined. It may be that simultaneous PET/MRI will be best suited for clinical situations that are disease-specific, organ-specific, related to diseases of the children or in those patients undergoing repeated imaging for whom cumulative radiation dose must be kept as low as reasonably achievable. PET/MRI also offers interesting opportunities for use of dual modality probes. Upon clear definition of clinical utility, other important and practical issues related to business operational model, clinical workflow and reimbursement will also be resolved. PMID:23791129

Competitive advantage of PET/MRI.

PubMed

Jadvar, Hossein; Colletti, Patrick M

2014-01-01

Multimodality imaging has made great strides in the imaging evaluation of patients with a variety of diseases. Positron emission tomography/computed tomography (PET/CT) is now established as the imaging modality of choice in many clinical conditions, particularly in oncology. While the initial development of combined PET/magnetic resonance imaging (PET/MRI) was in the preclinical arena, hybrid PET/MR scanners are now available for clinical use. PET/MRI combines the unique features of MRI including excellent soft tissue contrast, diffusion-weighted imaging, dynamic contrast-enhanced imaging, fMRI and other specialized sequences as well as MR spectroscopy with the quantitative physiologic information that is provided by PET. Most evidence for the potential clinical utility of PET/MRI is based on studies performed with side-by-side comparison or software-fused MRI and PET images. Data on distinctive utility of hybrid PET/MRI are rapidly emerging. There are potential competitive advantages of PET/MRI over PET/CT. In general, PET/MRI may be preferred over PET/CT where the unique features of MRI provide more robust imaging evaluation in certain clinical settings. The exact role and potential utility of simultaneous data acquisition in specific research and clinical settings will need to be defined. It may be that simultaneous PET/MRI will be best suited for clinical situations that are disease-specific, organ-specific, related to diseases of the children or in those patients undergoing repeated imaging for whom cumulative radiation dose must be kept as low as reasonably achievable. PET/MRI also offers interesting opportunities for use of dual modality probes. Upon clear definition of clinical utility, other important and practical issues related to business operational model, clinical workflow and reimbursement will also be resolved. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Mild Jugular Compression Collar Ameliorated Changes in Brain Activation of Working Memory after One Soccer Season in Female High School Athletes.

PubMed

Yuan, Weihong; Dudley, Jonathan; Barber Foss, Kim D; Ellis, Jonathan D; Thomas, Staci; Galloway, Ryan T; DiCesare, Christopher A; Leach, James L; Adams, Janet; Maloney, Thomas; Gadd, Brooke; Smith, David; Epstein, Jeff N; Grooms, Dustin R; Logan, Kelsey; Howell, David R; Altaye, Mekibib; Myer, Gregory D

2018-06-01

Recent neuroimaging studies have suggested that repetitive subconcussive head impacts, even after only one sport season, may lead to pre- to post-season structural and functional alterations in male high school football athletes. However, data on female athletes are limited. In the current investigation, we aimed to (1) assess the longitudinal pre- to post-season changes in functional MRI (fMRI) of working memory and working memory performance, (2) quantify the association between the pre- to post-season change in fMRI of working memory and the exposure to head impact and working memory performance, and (3) assess whether wearing a neck collar designed to reduce intracranial slosh via mild compression of the jugular veins can ameliorate the changes in fMRI brain activation observed in the female high school athletes who did not wear collars after a full soccer season. A total of 48 female high school soccer athletes (age range: 14.00-17.97 years) were included in the study. These athletes were assigned to the non-collar group (n = 21) or to the collar group (n = 27). All athletes undewent MRI at both pre-season and post-season. In each session, a fMRI verbal N-Back task was used to engage working memory. A significant pre- to post-season increase in fMRI blood oxygen level dependent (BOLD) signal was demonstrated when performing the N-back working memory task in the non-collar group but not in the collar group, despite the comparable exposure to head impacts during the season between the two groups. The collar group demonstrated significantly smaller pre- to post-season change in fMRI BOLD signal than the non-collar group, suggesting a potential protective effect from the collar device. Significant correlations were also found between the pre- to post-season increase in fMRI brain activation and the decrease in task accuracy in the non-collar group, indicating an association between the compensatory mechanism in underlying neurophysiology and the alteration in the behavioral outcomes.

Study of MRI in stratified viscous plasma configuration

NASA Astrophysics Data System (ADS)

Carlevaro, Nakia; Montani, Giovanni; Renzi, Fabrizio

2017-02-01

We analyze the morphology of the magneto-rotational instability (MRI) for a stratified viscous plasma disk configuration in differential rotation, taking into account the so-called corotation theorem for the background profile. In order to select the intrinsic Alfvénic nature of MRI, we deal with an incompressible plasma and we adopt a formulation of the local perturbation analysis based on the use of the magnetic flux function as a dynamical variable. Our study outlines, as consequence of the corotation condition, a marked asymmetry of the MRI with respect to the equatorial plane, particularly evident in a complete damping of the instability over a positive critical height on the equatorial plane. We also emphasize how such a feature is already present (although less pronounced) even in the ideal case, restoring a dependence of the MRI on the stratified morphology of the gravitational field.

MRI findings in an infant with vaccine-associated paralytic poliomyelitis.

PubMed

Ferraz-Filho, José Roberto Lopes; dos Santos Torres, Ulysses; de Oliveira, Eduardo Portela; Souza, Antonio Soares

2010-12-01

Although acute flaccid paralysis is a manifestation observed in several neurologic and muscular disorders, vaccine-associated paralytic poliomyelitis (VAPP) is an exceedingly rare etiology. In the clinical setting of acute flaccid paralysis, MRI is useful in differentiating between VAPP and other conditions. Additionally, MRI can assess the extent of lesions. However, reports on MRI findings in VAPP are scarce in the pediatric radiology literature. We report a Brazilian infant who developed VAPP 40 days after receiving the first dose of oral polio vaccine (OPV). MR images of the cervical and thoracic spinal cord showed lesions involving the anterior horn cell, with increased signal intensity on T2-weighted sequences. We would like to emphasize the importance of considering VAPP as a differential diagnosis in patients with acute flaccid paralysis and an MRI showing involvement of medulla oblongata or spinal cord, particularly in countries where OPV is extensively administered.

The benefits of the Atlas of Human Cardiac Anatomy website for the design of cardiac devices.

PubMed

Spencer, Julianne H; Quill, Jason L; Bateman, Michael G; Eggen, Michael D; Howard, Stephen A; Goff, Ryan P; Howard, Brian T; Quallich, Stephen G; Iaizzo, Paul A

2013-11-01

This paper describes how the Atlas of Human Cardiac Anatomy website can be used to improve cardiac device design throughout the process of development. The Atlas is a free-access website featuring novel images of both functional and fixed human cardiac anatomy from over 250 human heart specimens. This website provides numerous educational tutorials on anatomy, physiology and various imaging modalities. For instance, the 'device tutorial' provides examples of devices that were either present at the time of in vitro reanimation or were subsequently delivered, including leads, catheters, valves, annuloplasty rings and stents. Another section of the website displays 3D models of the vasculature, blood volumes and/or tissue volumes reconstructed from computed tomography and magnetic resonance images of various heart specimens. The website shares library images, video clips and computed tomography and MRI DICOM files in honor of the generous gifts received from donors and their families.

Positive Contrast Visualization of Nitinol Devices using Susceptibility Gradient Mapping

PubMed Central

Vonken, Evert-jan P.A.; Schär, Michael; Stuber, Matthias

2008-01-01

MRI visualization of devices is traditionally based on the signal loss due to T2* effects originating from the local susceptibility differences. To visualize nitinol devices with positive contrast a recently introduced post processing method is adapted to map the induced susceptibility gradients. This method operates on regular gradient echo MR images and maps the shift in k-space in a (small) neighborhood of every voxel by Fourier analysis followed by a center of mass calculation. The quantitative map of the local shifts generates the positive contrast image of the devices, while areas without susceptibility gradients render a background with noise only. The positive signal response of this method depends only on the choice of the voxel neighborhood size. The properties of the method are explained and the visualization of a nitinol wire and two stents are shown for illustration. PMID:18727096

Re-Evaluating Dissociations between Implicit and Explicit Category Learning: An Event-Related fMRI Study

ERIC Educational Resources Information Center

Gureckis, Todd M.; James, Thomas W.; Nosofsky, Robert M.

2011-01-01

Recent fMRI studies have found that distinct neural systems may mediate perceptual category learning under implicit and explicit learning conditions. In these previous studies, however, different stimulus-encoding processes may have been associated with implicit versus explicit learning. The present design was aimed at decoupling the influence of…

Role of the hippocampus and orbitofrontal cortex during the disambiguation of social cues in working memory

PubMed Central

Ross, Robert S.; LoPresti, Matthew L.; Schon, Karin; Stern, Chantal E.

2013-01-01

Human social interactions are complex behaviors requiring the concerted effort of multiple neural systems to track and monitor the individuals around us. Cognitively, adjusting our behavior based on changing social cues such as facial expressions relies on working memory and the ability to disambiguate, or separate, representations of overlapping stimuli resulting from viewing the same individual with different facial expressions. We conducted an fMRI experiment examining brain regions contributing to the encoding, maintenance and retrieval of overlapping identity information during working memory using a delayed match-to-sample (DMS) task. In the overlapping condition, two faces from the same individual with different facial expressions were presented at sample. In the non-overlapping condition, the two sample faces were from two different individuals with different expressions. fMRI activity was assessed by contrasting the overlapping and non-overlapping condition at sample, delay, and test. The lateral orbitofrontal cortex showed increased fMRI signal in the overlapping condition in all three phases of the DMS task and increased functional connectivity with the hippocampus when encoding overlapping stimuli. The hippocampus showed increased fMRI signal at test. These data suggest lateral orbitofrontal cortex helps encode and maintain representations of overlapping stimuli in working memory while the orbitofrontal cortex and hippocampus contribute to the successful retrieval of overlapping stimuli. We suggest the lateral orbitofrontal cortex and hippocampus play a role in encoding, maintaining, and retrieving social cues, especially when multiple interactions with an individual need to be disambiguated in a rapidly changing social context in order to make appropriate social responses. PMID:23640112

Pathological findings of uterine tumors preoperatively diagnosed as red degeneration of leiomyoma by MRI.

PubMed

Nakai, Go; Yamada, Takashi; Hamada, Takamitsu; Atsukawa, Natsuko; Tanaka, Yoshikazu; Yamamoto, Kiyohito; Higashiyama, Akira; Juri, Hiroshi; Nakamoto, Atsushi; Yamamoto, Kazuhiro; Hirose, Yoshinobu; Ohmichi, Masahide; Narumi, Yoshifumi

2017-07-01

Venous infarction of a leiomyoma is known as red degeneration of leiomyoma (RDL) and can be a cause of acute abdomen. Although magnetic resonance imaging (MRI) is the only modality that can depict the inner condition of a leiomyoma, the typical MR findings of RDL are sometimes identified incidentally even in asymptomatic patients. The purpose of this study is to clarify common pathological findings of uterine tumors preoperatively diagnosed as RDL by MRI. We diagnosed 28 cases of RDL by MRI from March 2007 to April 2015. The ten lesions subjected to pathological analysis after resection were included in the study and reviewed by a gynecological pathologist. The average time from MRI to operation was 4.7 months. The typical beefy-red color was not observed on the cut surface of the tumor except in one tumor resected during the acute phase. All lesions diagnosed as RDL by MRI had common pathological findings consistent with red degeneration of leiomyoma, including coagulative necrosis. Other common pathological features of RDL besides extensive coagulative necrosis appear to be a lack of inflammatory cell infiltrate or hemorrhage in the entire lesion. Although RDL is known to cause acute abdomen, its typical MR findings can be observed even in asymptomatic patients in a condition that manifests long after red degeneration. The characteristic pathological findings in both the acute phase and the chronic phase that we found in this study, along with radiology reports, will be helpful references for gynecologists and pathologists in suspecting a history of red degeneration and confirming the diagnosis.

Development of an apparatus and methodology for conducting functional magnetic resonance imaging (fMRI) with pharmacological stimuli in conscious rhesus monkeys.

PubMed

Murnane, Kevin Sean; Howell, Leonard Lee

2010-08-15

Functional magnetic resonance imaging (fMRI) is a technique with significant potential to advance our understanding of multiple brain systems. However, when human subjects undergo fMRI studies they are typically conscious whereas pre-clinical fMRI studies typically utilize anesthesia, which complicates comparisons across studies. Therefore, we have developed an apparatus suitable for imaging conscious rhesus monkeys. In order to minimize subject stress and spatial motion, each subject was acclimated to the necessary procedures over several months. The effectiveness of this process was then evaluated, in fully trained subjects, by quantifying objective physiological measures. These physiological metrics were stable both within and across sessions and did not differ from when these same subjects were immobilized using standard primate handling procedures. Subject motion and blood oxygenation level dependent (BOLD) fMRI measurements were then evaluated by scanning subjects under three different conditions: the absence of stimulation, presentation of a visual stimulus, or administration of intravenous (i.v.) cocaine (0.3mg/kg). Spatial motion differed neither by condition nor along the three principal axes. In addition, maximum translational and rotational motion never exceeded one half of the voxel size (0.75 mm) or 1.5 degrees, respectively. Furthermore, the localization of changes in blood oxygenation closely matched those reported in previous studies using similar stimuli. These findings document the feasibility of fMRI data collection in conscious rhesus monkeys using these procedures and allow for the further study of the neural effects of psychoactive drugs. (c) 2010 Elsevier B.V. All rights reserved.

Hybrid cardiac imaging using PET/MRI: a joint position statement by the European Society of Cardiovascular Radiology (ESCR) and the European Association of Nuclear Medicine (EANM).

PubMed

Nensa, Felix; Bamberg, Fabian; Rischpler, Christoph; Menezes, Leon; Poeppel, Thorsten D; la Fougère, Christian; Beitzke, Dietrich; Rasul, Sazan; Loewe, Christian; Nikolaou, Konstantin; Bucerius, Jan; Kjaer, Andreas; Gutberlet, Matthias; Prakken, Niek H; Vliegenthart, Rozemarijn; Slart, Riemer H J A; Nekolla, Stephan G; Lassen, Martin L; Pichler, Bernd J; Schlosser, Thomas; Jacquier, Alexis; Quick, Harald H; Schäfers, Michael; Hacker, Marcus

2018-05-02

Positron emission tomography (PET) and magnetic resonance imaging (MRI) have both been used for decades in cardiovascular imaging. Since 2010, hybrid PET/MRI using sequential and integrated scanner platforms has been available, with hybrid cardiac PET/MR imaging protocols increasingly incorporated into clinical workflows. Given the range of complementary information provided by each method, the use of hybrid PET/MRI may be justified and beneficial in particular clinical settings for the evaluation of different disease entities. In the present joint position statement, we critically review the role and value of integrated PET/MRI in cardiovascular imaging, provide a technical overview of cardiac PET/MRI and practical advice related to the cardiac PET/MRI workflow, identify cardiovascular applications that can potentially benefit from hybrid PET/MRI, and describe the needs for future development and research. In order to encourage its wide dissemination, this article is freely accessible on the European Radiology and European Journal of Hybrid Imaging web sites. • Studies and case-reports indicate that PET/MRI is a feasible and robust technology. • Promising fields of application include a variety of cardiac conditions. • Larger studies are required to demonstrate its incremental and cost-effective value. • The translation of novel radiopharmaceuticals and MR-sequences will provide exciting new opportunities.

In-Bore MR-Guided Biopsy Systems and Utility of PI-RADS.

PubMed

Fütterer, Jurgen J; Moche, Michael; Busse, Harald; Yakar, Derya

2016-06-01

A diagnostic dilemma exists in cases wherein a patient with clinical suspicion for prostate cancer has a negative transrectal ultrasound-guided biopsy session. Although transrectal ultrasound-guided biopsy is the standard of care, a paradigm shift is being observed. In biopsy-naive patients and patients with at least 1 negative biopsy session, multiparametric magnetic resonance imaging (MRI) is being utilized for tumor detection and subsequent targeting. Several commercial devices are now available for targeted prostate biopsy ranging from transrectal ultrasound-MR fusion biopsy to in bore MR-guided biopsy. In this review, we will give an update on the current status of in-bore MRI-guided biopsy systems and discuss value of prostate imaging-reporting and data system (PIRADS).

[An old woman with sudden pareses and blindness].

PubMed

Arntzen, Kjell Arne; Albretsen, Claus; Bajic, Radoslav

2007-03-01

We present a patient with Posterior Reversible Encephalopathy Syndrome (PRES). A 74-year-old woman was admitted with sepsis, which originated from erysipelas on her neck the following day. She developed respiratory obstruction due to oedema, septic shock, disseminated intravascular coagulation (DIC), acute renal failure and atrial fibrillation. She responded well to treatment and improved rapidly, despite of her serious condition. When she had almost fully recovered after 15 days, her general condition worsened, and she developed confusion, blindness and pareses. MRI showed vasogenic oedema in the parietooccipital regions of the brain and in the cerebellum, consistent with PRES. PRES is a clinical and radiological diagnosis consisting of headache, confusion, cortical blindness, convulsions and sometimes pareses. MRI of the cerebrum with diffusion-weighted imaging (DWI) and Apparent Diffusion Coefficient (ADC) map are decisive to the diagnosis, and usually shows a characteristic bilateral vasogenic oedema in the parietooccipital region. This can distinguish PRES from brain infarction, which shows a cytotoxic oedema on MRI. We discuss our patient in the light of different conditions leading to PRES, possible pathophysiological factors and treatment options.

NASA Robotic Neurosurgery Testbed

NASA Technical Reports Server (NTRS)

Mah, Robert

1997-01-01

The detection of tissue interface (e.g., normal tissue, cancer, tumor) has been limited clinically to tactile feedback, temperature monitoring, and the use of a miniature ultrasound probe for tissue differentiation during surgical operations, In neurosurgery, the needle used in the standard stereotactic CT or MRI guided brain biopsy provides no information about the tissue being sampled. The tissue sampled depends entirely upon the accuracy with which the localization provided by the preoperative CT or MRI scan is translated to the intracranial biopsy site. In addition, no information about the tissue being traversed by the needle (e.g., a blood vessel) is provided. Hemorrhage due to the biopsy needle tearing a blood vessel within the brain is the most devastating complication of stereotactic CT/MRI guided brain biopsy. A robotic neurosurgery testbed has been developed at NASA Ames Research Center as a spin-off of technologies from space, aeronautics and medical programs. The invention entitled "Robotic Neurosurgery Leading to Multimodality Devices for Tissue Identification" is nearing a state ready for commercialization. The devices will: 1) improve diagnostic accuracy and precision of general surgery, with near term emphasis on stereotactic brain biopsy, 2) automate tissue identification, with near term emphasis on stereotactic brain biopsy, to permit remote control of the procedure, and 3) reduce morbidity for stereotactic brain biopsy. The commercial impact from this work is the potential development of a whole new generation of smart surgical tools to increase the safety, accuracy and efficiency of surgical procedures. Other potential markets include smart surgical tools for tumor ablation in neurosurgery, general exploratory surgery, prostate cancer surgery, and breast cancer surgery.

NASA Robotic Neurosurgery Testbed

NASA Technical Reports Server (NTRS)

Mah, Robert

1997-01-01

The detection of tissue interface (e.g., normal tissue, cancer, tumor) has been limited clinically to tactile feedback, temperature monitoring, and the use of a miniature ultrasound probe for tissue differentiation during surgical operations. In neurosurgery, the needle used in the standard stereotactic CT (Computational Tomography) or MRI (Magnetic Resonance Imaging) guided brain biopsy provides no information about the tissue being sampled. The tissue sampled depends entirely upon the accuracy with which the localization provided by the preoperative CT or MRI scan is translated to the intracranial biopsy site. In addition, no information about the tissue being traversed by the needle (e.g., a blood vessel) is provided. Hemorrhage due to the biopsy needle tearing a blood vessel within the brain is the most devastating complication of stereotactic CT/MRI guided brain biopsy. A robotic neurosurgery testbed has been developed at NASA Ames Research Center as a spin-off of technologies from space, aeronautics and medical programs. The invention entitled 'Robotic Neurosurgery Leading to Multimodality Devices for Tissue Identification' is nearing a state ready for commercialization. The devices will: 1) improve diagnostic accuracy and precision of general surgery, with near term emphasis on stereotactic brain biopsy, 2) automate tissue identification, with near term emphasis on stereotactic brain biopsy, to permit remote control of the procedure, and 3) reduce morbidity for stereotactic brain biopsy. The commercial impact from this work is the potential development of a whole new generation of smart surgical tools to increase the safety, accuracy and efficiency of surgical procedures. Other potential markets include smart surgical tools for tumor ablation in neurosurgery, general exploratory surgery, prostate cancer surgery, and breast cancer surgery.

Fetal cerebral imaging - ultrasound vs. MRI: an update.

PubMed

Blondiaux, Eléonore; Garel, Catherine

2013-11-01

The purpose of this article is to analyze the advantages and limitations of prenatal ultrasonography (US) and magnetic resonance imaging (MRI) in the evaluation of the fetal brain. These imaging modalities should not be seen as competitive but rather as complementary. There are wide variations in the world regarding screening policies, technology, skills, and legislation about termination of pregnancy, and these variations markedly impact on the way of using prenatal imaging. According to the contribution expected from each technique and to local working conditions, one should choose the most appropriate imaging modality on a case-by-case basis. The advantages and limitations of US and MRI in the setting of fetal brain imaging are displayed. Different anatomical regions (midline, ventricles, subependymal area, cerebral parenchyma, pericerebral space, posterior fossa) and pathological conditions are analyzed and illustrated in order to compare the respective contribution of each technique. An accurate prenatal diagnosis of cerebral abnormalities is of utmost importance for prenatal counseling.

Single-task fMRI overlap predicts concurrent multitasking interference.

PubMed

Nijboer, Menno; Borst, Jelmer; van Rijn, Hedderik; Taatgen, Niels

2014-10-15

There is no consensus regarding the origin of behavioral interference that occurs during concurrent multitasking. Some evidence points toward a multitasking locus in the brain, while other results imply that interference is the consequence of task interactions in several brain regions. To investigate this issue, we conducted a functional MRI (fMRI) study consisting of three component tasks, which were performed both separately and in combination. The results indicated that no specific multitasking area exists. Instead, different patterns of activation across conditions could be explained by assuming that the interference is a result of task interactions. Additionally, similarity in single-task activation patterns correlated with a decrease in accuracy during dual-task conditions. Taken together, these results support the view that multitasking interference is not due to a bottleneck in a single "multitasking" brain region, but is a result of interactions between concurrently running processes. Copyright © 2014 Elsevier Inc. All rights reserved.

Functional magnetic resonance imaging.

PubMed

Buchbinder, Bradley R

2016-01-01

Functional magnetic resonance imaging (fMRI) maps the spatiotemporal distribution of neural activity in the brain under varying cognitive conditions. Since its inception in 1991, blood oxygen level-dependent (BOLD) fMRI has rapidly become a vital methodology in basic and applied neuroscience research. In the clinical realm, it has become an established tool for presurgical functional brain mapping. This chapter has three principal aims. First, we review key physiologic, biophysical, and methodologic principles that underlie BOLD fMRI, regardless of its particular area of application. These principles inform a nuanced interpretation of the BOLD fMRI signal, along with its neurophysiologic significance and pitfalls. Second, we illustrate the clinical application of task-based fMRI to presurgical motor, language, and memory mapping in patients with lesions near eloquent brain areas. Integration of BOLD fMRI and diffusion tensor white-matter tractography provides a road map for presurgical planning and intraoperative navigation that helps to maximize the extent of lesion resection while minimizing the risk of postoperative neurologic deficits. Finally, we highlight several basic principles of resting-state fMRI and its emerging translational clinical applications. Resting-state fMRI represents an important paradigm shift, focusing attention on functional connectivity within intrinsic cognitive networks. © 2016 Elsevier B.V. All rights reserved.

Flow in cerebral aneurysms: 4D Flow MRI measurements and CFD models

NASA Astrophysics Data System (ADS)

Rayz, Vitaliy; Schnell, Susanne

2017-11-01

4D Flow MRI is capable of measuring blood flow in vivo, providing time-resolved velocity fields in 3D. The dynamic range of the 4D Flow MRI is determined by a velocity sensitivity parameter (venc), set above the expected maximum velocity, which can result in noisy data for slow flow regions. A dual-venc 4D flow MRI technique, where both low- and high-venc data are acquired, can improve velocity-to-noise ratio and, therefore, quantification of clinically-relevant hemodynamic metrics. In this study, patient-specific CFD simulations were used to evaluate the advantages of the dual-venc approach for assessment of the flow in cerebral aneurysms. The flow in 2 cerebral aneurysms was measured in vivo with dual-venc 4D Flow MRI and simulated with CFD, using the MRI data to prescribe flow boundary conditions. The flow fields obtained with computations were compared to those measured with a single- and dual-venc 4D Flow MRI. The numerical models resolved small flow structures near the aneurysmal wall, that were not detected with a single-venc acquisition. Comparison of the numerical and imaging results shows that the dual-venc approach can improve the accuracy of the 4D Flow MRI measurements in regions characterized by high-velocity jets and slow recirculating flows.

Distinguishing the Magnetorotational Instability (MRI) from Magnetized Ekman Flows in the PPPL MRI Experiment

NASA Astrophysics Data System (ADS)

Gilson, Erik; Caspary, Kyle; Goodman, Jeremy; Ji, Hantao; Schartman, Ethan; Wei, Xing

2015-11-01

Results are presented from initial experiments on the upgraded Magnetorotational Instability (MRI) experiment that uses GaInSn as the working fluid and now operates with conductive end caps to improve the coupling of angular momentum to the fluid to increase the saturation amplitude of the MRI signal. Measurements of the fluid velocity field and perturbed magnetic field over a range of magnetic Reynolds numbers, Rm , and Lundquist numbers, S, are compared with results from the SFEMaNS code in order to separate the effects of MRI on the system from effects such as Ekman flows and Shercliff layer instabilities. The MRI can be identified by observing its growth rate, noting the relative magnitudes and spatial distributions of the perturbed radial flow velocity ur and radial magnetic field Br, and measuring the scaling of ur and Br with Rm . The clear identification of the onset of MRI in the apparatus is complicated by the geometry and boundary conditions creating an imperfect supercritical pitchfork bifurcation. Nevertheless, a stability diagram can be created that shows that MRI is a weak-field instability that occurs only below a certain value of the normalized magnetic field S / Rm but above a threshold where viscous effects damps the growth of the instability.

TU-EF-BRA-01: NMR and Proton Density MRI of the 1D Patient

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolbarst, A.

NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm.more » MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common applications of MRI exploit its capability to detect and image distinct movements of fluids: MR angiography (MRA), which rivals CT angiography but often requires no contrast medium, monitors the bulk flow of blood; functional MRI ( f MRI), distinguishes the perfusion of oxygenated blood from that of de-oxygenated, and lights up parts of the brain that are activated by a stimulus, rather like PET; and diffusion tensor imaging (DTI) indicates the diffusion of free water along tracts of axons, thereby bringing nerve trunks into view. There are variants on all of these themes, and on others as well. Magnetic Resonance Spectroscopy (MRS), for example, can perform non-invasive ‘virtual biopsies’ that allow identification of certain cancers and other lesions. And an MRI-guided needle biopsy can sample brain tissue from a region only millimeters in dimensions. MRI, however, involves deeper and more complex aspects of physics, technology, and biology than do most other imaging modalities, and it is widely considered to be correspondingly more difficult to learn. We could probably cover all of this rather comprehensively if we had 50 hours available rather than 2 ̶ but, to paraphrase a former Secretary of Defense, you tell your story in the time you have allotted. The four presenters and another physicist, Kevin King from GE, have combined their efforts to co-author a single slide show that describes essentials of MRI as simply as possible. It is obviously far from thorough, but hopefully it will succeed in explaining some of the basics in a simplified but still valid fashion; in providing a taste of the numerous capabilities and complexities of the modality; and in whetting your appetite to learn more. Part I. NMR, and Proton Density MRI of the 1D Patient (Wolbarst), begins with an introductory case study that illustrates a half dozen ways in which MRI provides valuable clinical information. It then explores the nuclear magnetic resonance (NMR) phenomenon, which underlies MRI. NMR can be introduced with either of two approaches. In the first, one thinks (loosely) of the nuclei of hydrogen atoms as (rotating and charged and therefore) magnetic objects, whose spin-axes tend to align in a strong external magnetic field, much like a compass needle. As with the Bohr atom, this spin-up/spin-down picture is a highly abridged version of the full quantum mechanical treatment, but still it leads to some useful, legitimate pictures of the NMR process occurring within a voxel: When RF photons of the correct (Larmor) frequency elevate protons in a fixed magnetic field out of their lower-energy spin state into the upper, the NMR phenomenon is indicated by the detectable absorption of RF power. With the addition of a linear gradient field along a multi-voxel, one-dimensional patient/phantom, as well, we can determine the water content of each compartment – an example of a real MRI study, albeit in 1D. Part I concludes with a discussion of the net magnetization at position x, m0(x), under conditions of dynamic thermal equilibrium, which leads into: Part II. Net Voxel Magnetization, m(x,t); T1-MRI; The MRI Device (Lemen), investigates the biophysics of the form of proton spin relaxation process characterized by the time T1. It then moves on to the creation of an MR image that displays the spatial variation in the values of this clinically relevant parameter, again in 1D. Finally, the design and workings of a clinical MRI machine are sketched, in preparation for: Part III. ‘Classical’ NMR; FID Imaging in 1D via k-Space (Yanasak) presents the second standard approach to NMR and MRI, the classical model. It focuses on the time dependence of the net nuclear magnetization, m(x,t), the overall magnetic field generated by the cohort of protons in the voxel at position x. Quite remarkably, this nuclear net magnetization itself acts in a strong magnetic field like a gyroscope in a gravitational field. This tack is better for explaining Free Induction Decay (FID), which involves a brief introduction to the Fourier transform and k-space. This leads to conventional Spin-Echo (S-E) reconstruction techniques for creating clinical images from raw data, and sets the stage for: Part IV. Spin-Echo; S-E / Spin Warp in a 2D Slice (Price) discusses application of the S- E sequence of radiofrequency pulses and gradient magnetic fields to the 1D patient. T2 is introduced but not explained. This Part also considers how to manipulate the image acquisition parameters so as to generate clinical pictures with contrast dominated by spatial variations in PD, T1, or T2. We conclude by demonstrating the spin-warp approach to imaging in 2D with a simple 2×2, 4-voxel example. Much of this material is presented in more detail in the chapter “MRI of the One-dimensional Patient, Part I”, in Advances in Medical Physics, Vol 5 (2014). Copies are on display at the Medical Physics Publishing booth. Learning Objectives: The participant will learn about the processes of NMR and T1 spin relaxation in a tissue voxel in a uniform magnetic field. The participant will learn about combining spin-up/spin-down NMR and T1 processes with a linear gradient to effect frequency-encoding of voxel spatial position. This approach can be used to create proton density and T1 MRI maps, respectively, of the contents of multi-voxel 1D phantoms. The participant will learn about how the ‘classical’ model of NMR it can generate Free Induction Decay (FID) images of 1D phantoms, which involves the use of the Fourier transform in k-space. This can lead simply into standard Spin-Echo images. The participant will learn about extending Spin-Echo imaging into 2 and more dimensions.« less

Feasibility of an intracranial EEG-fMRI protocol at 3T: risk assessment and image quality.

PubMed

Boucousis, Shannon M; Beers, Craig A; Cunningham, Cameron J B; Gaxiola-Valdez, Ismael; Pittman, Daniel J; Goodyear, Bradley G; Federico, Paolo

2012-11-15

Integrating intracranial EEG (iEEG) with functional MRI (iEEG-fMRI) may help elucidate mechanisms underlying the generation of seizures. However, the introduction of iEEG electrodes in the MR environment has inherent risk and data quality implications that require consideration prior to clinical use. Previous studies of subdural and depth electrodes have confirmed low risk under specific circumstances at 1.5T and 3T. However, no studies have assessed risk and image quality related to the feasibility of a full iEEG-fMRI protocol. To this end, commercially available platinum subdural grid/strip electrodes (4×5 grid or 1×8 strip) and 4 or 6-contact depth electrodes were secured to the surface of a custom-made phantom mimicking the conductivity of the human brain. Electrode displacement, temperature increase of electrodes and surrounding phantom material, and voltage fluctuations in electrode contacts were measured in a GE Discovery MR750 3T MR scanner during a variety of imaging sequences, typical of an iEEG-fMRI protocol. An electrode grid was also used to quantify the spatial extent of susceptibility artifact. The spatial extent of susceptibility artifact in the presence of an electrode was also assessed for typical imaging parameters that maximize BOLD sensitivity at 3T (TR=1500 ms; TE=30 ms; slice thickness=4mm; matrix=64×64; field-of-view=24 cm). Under standard conditions, all electrodes exhibited no measurable displacement and no clinically significant temperature increase (<1°C) during scans employed in a typical iEEG-fMRI experiment, including 60 min of continuous fMRI. However, high SAR sequences, such as fast spin-echo (FSE), produced significant heating in almost all scenarios (>2.0°C) that in some cases exceeded 10°C. Induced voltages in the frequency range that could elicit neuronal stimulation (<10 kHz) were well below the threshold of 100 mV. fMRI signal intensity was significantly reduced within 20mm of the electrodes for the imaging parameters used in this study. Thus, for the conditions tested, a full iEEG-fMRI protocol poses a low risk at 3T; however, fMRI sensitivity may be reduced immediately adjacent to the electrodes. In addition, high SAR sequences must be avoided. Copyright © 2012 Elsevier Inc. All rights reserved.

An Investigation of the Relationship Between fMRI and ERP Source Localized Measurements of Brain Activity during Face Processing

PubMed Central

Richards, Todd; Webb, Sara Jane; Murias, Michael; Merkle, Kristen; Kleinhans, Natalia M.; Johnson, L. Clark; Poliakov, Andrew; Aylward, Elizabeth; Dawson, Geraldine

2013-01-01

Brain activity patterns during face processing have been extensively explored with functional magnetic resonance imaging (fMRI) and event-related potentials (ERPs). ERP source localization adds a spatial dimension to the ERP time series recordings, which allows for a more direct comparison and integration with fMRI findings. The goals for this study were (1) to compare the spatial descriptions of neuronal activity during face processing obtained with fMRI and ERP source localization using low-resolution electro-magnetic tomography (LORETA), and (2) to use the combined information from source localization and fMRI to explore how the temporal sequence of brain activity during face processing is summarized in fMRI activation maps. fMRI and high-density ERP data were acquired in separate sessions for 17 healthy adult males for a face and object processing task. LORETA statistical maps for the comparison of viewing faces and viewing houses were coregistered and compared to fMRI statistical maps for the same conditions. The spatial locations of face processing-sensitive activity measured by fMRI and LORETA were found to overlap in a number of areas including the bilateral fusiform gyri, the right superior, middle and inferior temporal gyri, and the bilateral precuneus. Both the fMRI and LORETA solutions additionally demon-strated activity in regions that did not overlap. fMRI and LORETA statistical maps of face processing-sensitive brain activity were found to converge spatially primarily at LORETA solution latencies that were within 18 ms of the N170 latency. The combination of data from these techniques suggested that electrical brain activity at the latency of the N170 is highly represented in fMRI statistical maps. PMID:19322649

Mapping (and modeling) physiological movements during EEG-fMRI recordings: the added value of the video acquired simultaneously.

PubMed

Ruggieri, Andrea; Vaudano, Anna Elisabetta; Benuzzi, Francesca; Serafini, Marco; Gessaroli, Giuliana; Farinelli, Valentina; Nichelli, Paolo Frigio; Meletti, Stefano

2015-01-15

During resting-state EEG-fMRI studies in epilepsy, patients' spontaneous head-face movements occur frequently. We tested the usefulness of synchronous video recording to identify and model the fMRI changes associated with non-epileptic movements to improve sensitivity and specificity of fMRI maps related to interictal epileptiform discharges (IED). Categorization of different facial/cranial movements during EEG-fMRI was obtained for 38 patients [with benign epilepsy with centro-temporal spikes (BECTS, n=16); with idiopathic generalized epilepsy (IGE, n=17); focal symptomatic/cryptogenic epilepsy (n=5)]. We compared at single subject- and at group-level the IED-related fMRI maps obtained with and without additional regressors related to spontaneous movements. As secondary aim, we considered facial movements as events of interest to test the usefulness of video information to obtain fMRI maps of the following face movements: swallowing, mouth-tongue movements, and blinking. Video information substantially improved the identification and classification of the artifacts with respect to the EEG observation alone (mean gain of 28 events per exam). Inclusion of physiological activities as additional regressors in the GLM model demonstrated an increased Z-score and number of voxels of the global maxima and/or new BOLD clusters in around three quarters of the patients. Video-related fMRI maps for swallowing, mouth-tongue movements, and blinking were comparable to the ones obtained in previous task-based fMRI studies. Video acquisition during EEG-fMRI is a useful source of information. Modeling physiological movements in EEG-fMRI studies for epilepsy will lead to more informative IED-related fMRI maps in different epileptic conditions. Copyright © 2014 Elsevier B.V. All rights reserved.

Adaptive suppression of power line interference in ultra-low field magnetic resonance imaging in an unshielded environment

NASA Astrophysics Data System (ADS)

Huang, Xiaolei; Dong, Hui; Qiu, Yang; Li, Bo; Tao, Quan; Zhang, Yi; Krause, Hans-Joachim; Offenhäusser, Andreas; Xie, Xiaoming

2018-01-01

Power-line harmonic interference and fixed-frequency noise peaks may cause stripe-artifacts in ultra-low field (ULF) magnetic resonance imaging (MRI) in an unshielded environment and in a conductively shielded room. In this paper we describe an adaptive suppression method to eliminate these artifacts in MRI images. This technique utilizes spatial correlation of the interference from different positions, and is realized by subtracting the outputs of the reference channel(s) from those of the signal channel(s) using wavelet analysis and the least squares method. The adaptive suppression method is first implemented to remove the image artifacts in simulation. We then experimentally demonstrate the feasibility of this technique by adding three orthogonal superconducting quantum interference device (SQUID) magnetometers as reference channels to compensate the output of one 2nd-order gradiometer. The experimental results show great improvement in the imaging quality in both 1D and 2D MRI images at two common imaging frequencies, 1.3 kHz and 4.8 kHz. At both frequencies, the effective compensation bandwidth is as high as 2 kHz. Furthermore, we examine the longitudinal relaxation times of the same sample before and after compensation, and show that the MRI properties of the sample did not change after applying adaptive suppression. This technique can effectively increase the imaging bandwidth and be applied to ULF MRI detected by either SQUIDs or Faraday coil in both an unshielded environment and a conductively shielded room.

Navigation concepts for magnetic resonance imaging-guided musculoskeletal interventions.

PubMed

Busse, Harald; Kahn, Thomas; Moche, Michael

2011-08-01

Image-guided musculoskeletal (MSK) interventions are a widely used alternative to open surgical procedures for various pathological findings in different body regions. They traditionally involve one of the established x-ray imaging techniques (radiography, fluoroscopy, computed tomography) or ultrasound scanning. Over the last decades, magnetic resonance imaging (MRI) has evolved into one of the most powerful diagnostic tools for nearly the whole body and has therefore been increasingly considered for interventional guidance as well.The strength of MRI for MSK applications is a combination of well-known general advantages, such as multiplanar and functional imaging capabilities, wide choice of tissue contrasts, and absence of ionizing radiation, as well as a number of MSK-specific factors, for example, the excellent depiction of soft-tissue tumors, nonosteolytic bone changes, and bone marrow lesions. On the downside, the magnetic resonance-compatible equipment needed, restricted space in the magnet, longer imaging times, and the more complex workflow have so far limited the number of MSK procedures under MRI guidance.Navigation solutions are generally a natural extension of any interventional imaging system, in particular, because powerful hardware and software for image processing have become routinely available. They help to identify proper access paths, provide accurate feedback on the instrument positions, facilitate the workflow in an MRI environment, and ultimately contribute to procedural safety and success.The purposes of this work were to describe some basic concepts and devices for MRI guidance of MSK procedures and to discuss technical and clinical achievements and challenges for some selected implementations.

Exploratory study on the effects of a robotic hand rehabilitation device on changes in grip strength and brain activity after stroke.

PubMed

Pinter, Daniela; Pegritz, Sandra; Pargfrieder, Christa; Reiter, Gudrun; Wurm, Walter; Gattringer, Thomas; Linderl-Madrutter, Regina; Neuper, Claudia; Fazekas, Franz; Grieshofer, Peter; Enzinger, Christian

2013-01-01

The brain mechanisms underlying successful recovery of hand fuenction after stroke are still not fully understood, although functional MRI (fMRI) studies underline the importance of neuronal plasticity. We explored potential changes in brain activity in 7 patients with subacute to chronic stroke (69 ± 8 years) with moderate- to high-grade distal paresis of the upper limb (Motricity Index: 59.4) after standardized robotic finger-hand rehabilitation training, in addition to conventional rehabilitation therapy for 3 weeks. Behavioral and fMRI assessments were carried out before and after training to characterize changes in brain activity and behavior. The Motricity Index (pre: 59.4, post: 67.2, P < .05) and grip force (pre: 7.26, post: 11.87, P < .05) of the paretic hand increased significantly after rehabilitation. On fMRI, active movement of the affected (left) hand resulted in contralesional (ie, ipsilateral) activation of the primary sensorimotor cortex prior to rehabilitation. After rehabilitation, activation appeared "normalized," including the ipsilesional primary sensorimotor cortex and supplementary motor area (SMA). No changes and no abnormalities of activation maps were seen during movement of the unaffected hand. Subsequent region-of-interest analyses showed no significant ipsilesional activation increases after rehabilitation. Despite behavioral improvements, we failed to identify consistent patterns of functional reorganization in our sample. This warrants caution in the use of fMRI as a tool to explore neural plasticity in heterogeneous samples lacking sufficient statistical power.

Evaluation of dose delivery accuracy of gamma knife using MRI polymer gel dosimeter in an inhomogeneous phantom

NASA Astrophysics Data System (ADS)

Pourfallah T, A.; Alam N, Riahi; M, Allahverdi; M, Ay; M, Zahmatkesh

2009-05-01

Polymer gel dosimetry is still the only dosimetry method for directly measuring three-dimensional dose distributions. MRI Polymer gel dosimeters are tissue equivalent and can act as a phantom material. Because of high dose response sensitivity, the MRI was chosen as readout device. In this study dose profiles calculated with treatment-planning software (LGP) and measurements with the MR polymer gel dosimeter for single-shot irradiations were compared. A custom-built 16 cm diameter spherical plexiglas head phantom was used in this study. Inside the phantom, there is a cubic cutout for insertion of gel phantoms and another cutout for inserting the inhomogeneities. The phantoms were scanned with a 1.5T MRI (Siemens syngo MR 2004A 4VA25A) scanner. The multiple spin-echo sequence with 32 echoes was used for the MRI scans. Calibration relations between the spin-spin relaxation rate and the absorbed dose were obtained by using small cylindrical vials, which were filled with the PAGAT polymer gel from the same batch as for the spherical phantom. 1D and 2D data obtained using gel dosimeter for homogeneous and inhomogeneous phantoms were compared with dose obtained using LGP calculation. The distance between relative isodose curves obtained for homogeneous phantom and heterogeneous phantoms exceed the accepted total positioning error (>±2mm). The findings of this study indicate that dose measurement using PAGAT gel dosimeter can be used for verifying dose delivering accuracy in GK unit in presence of inhomogeneities.

Technological Advances in Deep Brain Stimulation.

PubMed

Ughratdar, Ismail; Samuel, Michael; Ashkan, Keyoumars

2015-01-01

Functional and stereotactic neurosurgery has always been regarded as a subspecialty based on and driven by technological advances. However until recently, the fundamentals of deep brain stimulation (DBS) hardware and software design had largely remained stagnant since its inception almost three decades ago. Recent improved understanding of disease processes in movement disorders as well clinician and patient demands has resulted in new avenues of development for DBS technology. This review describes new advances both related to hardware and software for neuromodulation. New electrode designs with segmented contacts now enable sophisticated shaping and sculpting of the field of stimulation, potentially allowing multi-target stimulation and avoidance of side effects. To avoid lengthy programming sessions utilising multiple lead contacts, new user-friendly software allows for computational modelling and individualised directed programming. Therapy delivery is being improved with the next generation of smaller profile, longer-lasting, re-chargeable implantable pulse generators (IPGs). These include IPGs capable of delivering constant current stimulation or personalised closed-loop adaptive stimulation. Post-implantation Magnetic Resonance Imaging (MRI) has long been an issue which has been partially overcome with 'MRI conditional devices' and has enabled verification of DBS lead location. Surgical technique is considering a shift from frame-based to frameless stereotaxy or greater role for robot assisted implantation. The challenge for these contemporary techniques however, will be in demonstrating equivalent safety and accuracy to conventional methods. We also discuss potential future direction utilising wireless technology allowing for miniaturisation of hardware.

Neuroaging through the Lens of the Resting State Networks

PubMed Central

2018-01-01

Resting state functional magnetic resonance imaging (rs-fMRI) allows studying spontaneous brain activity in absence of task, recording changes of Blood Oxygenation Level Dependent (BOLD) signal. rs-fMRI enables identification of brain networks also called Resting State Networks (RSNs) including the most studied Default Mode Network (DMN). The simplicity and speed of execution make rs-fMRI applicable in a variety of normal and pathological conditions. Since it does not require any task, rs-fMRI is particularly useful for protocols on patients, children, and elders, increasing participant's compliance and reducing intersubjective variability due to the task performance. rs-fMRI has shown high sensitivity in identification of RSNs modifications in several diseases also in absence of structural modifications. In this narrative review, we provide the state of the art of rs-fMRI studies about physiological and pathological aging processes. First, we introduce the background of resting state; then we review clinical findings provided by rs-fMRI in physiological aging, Mild Cognitive Impairment (MCI), Alzheimer Dementia (AD), and Late Life Depression (LLD). Finally, we suggest future directions in this field of research and its potential clinical applications. PMID:29568755

Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI) Combined with Positron Emission Tomography-Computed Tomography (PET-CT) and Video-Electroencephalography (VEEG) Have Excellent Diagnostic Value in Preoperative Localization of Epileptic Foci in Children with Epilepsy.

PubMed

Wang, Gui-Bin; Long, Wei; Li, Xiao-Dong; Xu, Guang-Yin; Lu, Ji-Xiang

2017-01-01

BACKGROUND To investigate the effect that dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has on surgical decision making relative to video-electroencephalography (VEEG) and positron emission tomography-computed tomography (PET-CT), and if the differences in these variables translates to differences in surgical outcomes. MATERIAL AND METHODS A total of 166 children with epilepsy undergoing preoperative DCE-MRI, VEEG, and PET-CT examinations, surgical resection of epileptic foci, and intraoperative electrocorticography (ECoG) monitoring were enrolled. All children were followed up for 12 months and grouped by Engles prognostic classification for epilepsy. Based on intraoperative ECoG as gold standard, the diagnostic values of DCE-MRI, VEEG, PET-CT, DCE-MRI combined with VEEG, DCE-MRI combined with PET-CT, and combined application of DCE-MRI, VEEG, and PET-CT in preoperative localization for epileptic foci were evaluated. RESULTS The sensitivity of DCE-MRI, VEEG, and PET-CT was 59.64%, 76.51%, and 93.98%, respectively; the accuracy of DCE-MRI, VEEG, PET-CT, DCE-MRI combined with VEEG, and DCE-MRI combined with PET-CT was 57.58%, 67.72%, 91.03%, 91.23%, and 96.49%, respectively. Localization accuracy rate of the combination of DCE-MRI, VEEG, and PET-CT was 98.25% (56/57), which was higher than that of DCE-MRI combined with VEEG and of DCE-MRI combined with PET-CT. No statistical difference was found in the accuracy rate of localization between these three combined techniques. During the 12-month follow-up, children were grouped into Engles grade I (n=106), II (n=31), III (n=21), and IV (n=8) according to postoperative conditions. CONCLUSIONS All DCE-MRI combined with VEEG, DCE-MRI combined with PET-CT, and DCE-MRI combined with VEEG and PET-CT examinations have excellent accuracy in preoperative localization of epileptic foci and present excellent postoperative efficiency, suggesting that these combined imaging methods are suitable for serving as the reference basis in preoperative localization of epileptic foci in children with epilepsy.

Low-field and high-field magnetic resonance contrast imaging of magnetoferritin as a pathological model system of iron accumulation

NASA Astrophysics Data System (ADS)

Strbak, Oliver; Balejcikova, Lucia; Baciak, Ladislav; Kovac, Jozef; Masarova-Kozelova, Marta; Krafcik, Andrej; Dobrota, Dusan; Kopcansky, Peter

2017-09-01

Various pathological processes including neurodegenerative disorders are associated with the accumulation of iron, while it is believed that a precursor of iron accumulation is ferritin. Physiological ferritin is due to low relaxivity, which results in only weak detection by magnetic resonance imaging (MRI) techniques. On the other hand, pathological ferritin is associated with disrupted iron homeostasis and structural changes in the mineral core, and should increase the hypointensive artefacts in MRI. On the basis of recent findings in respect to the pathological ferritin structure, we prepared the magnetoferritin particles as a possible pathological ferritin model system. The particles were characterised with dynamic light scattering, as well as with superconducting quantum interference device measurements. With the help of low-field (0.2 T) and high-field (4.7 T) MRI standard T 2-weighted protocols we found that it is possible to clearly distinguish between native ferritin as a physiological model system, and magnetoferritin as a pathological model system. Surprisingly, the T 2-weighted short TI inversion recovery protocol at low-field system showed the optimum contrast differentiation. Such findings are highly promising for exploiting the use of iron accumulation as a noninvasive diagnostics tool of pathological processes, where the magnetoferritin particles could be utilised as MRI iron quantification calibration samples.

New concepts and materials for the manufacturing of MR-compatible guide wires.

PubMed

Brecher, Christian; Emonts, Michael; Brack, Alexander; Wasiak, Christian; Schütte, Adrian; Krämer, Nils; Bruhn, Robin

2014-04-01

This paper shows the development of a new magnetic resonance imaging (MRI)-compatible guide wire made from fiber-reinforced plastics. The basic material of the developed guide wire is manufactured using a specially developed micro-pullwinding technology, which allows the adjustment of tensile, bending, and torsional stiffness independent from each other. Additionally, the micro-pullwinding technology provides the possibility to vary the stiffness along the length of the guide wire in a continuous process. With the possibilities of this technology, the mechanical properties of the guide wire were precisely adjusted for the intended usage in MRI-guided interventions. The performance of the guide wire regarding the mechanical properties was investigated. It could be shown, that the mechanical properties could be changed independently from each other by varying the process parameters. Especially, the torsional stiffness could be significantly improved with only a minor influence on bending and tensile properties. The precise influence of the variation of the winding angle on the mechanical and geometrical properties has to be further investigated. The usability of the guide wire as well as its visibility in MRI was investigated by radiologists. With the micro-pullwinding technology, a continuous manufacturing technique for highly stressable, MRI-safe profiles is available and can be the trigger for a new class of medical devices.

Effects of inaccuracies in arterial path length measurement on differences in MRI and tonometry measured pulse wave velocity.

PubMed

Weir-McCall, Jonathan R; Khan, Faisel; Cassidy, Deirdre B; Thakur, Arsh; Summersgill, Jennifer; Matthew, Shona Z; Adams, Fiona; Dove, Fiona; Gandy, Stephen J; Colhoun, Helen M; Belch, Jill Jf; Houston, J Graeme

2017-05-10

Carotid-femoral pulse wave velocity (cf-PWV) and aortic PWV measured using MRI (MRI-PWV) show good correlation, but with a significant and consistent bias across studies. The aim of the current study was to evaluate whether the differences between cf.-PWV and MRI-PWV can be accounted for by inaccuracies of currently used distance measurements. One hundred fourteen study participants were recruited into one of 4 groups: Type 2 diabetes melltus (T2DM) with cardiovascular disease (CVD) (n = 23), T2DM without CVD (n = 41), CVD without T2DM (n = 25) and a control group (n = 25). All participants underwent cf.-PWV, cardiac MRI and whole body MR angiography(WB-MRA). 90 study participants also underwent aortic PWV using MRI. cf.-PWV EXT was performed using a SphygmoCor device (Atcor Medical, West Ryde, Australia). The true intra-arterial pathlength was measured using the WB-MRA and then used to recalculate the cf.-PWV EXT to give a cf.-PWV MRA . Distance measurements were significantly lower on WB-MRA than on external tape measure (mean diff = -85.4 ± 54.0 mm,p < 0.001). MRI-PWV was significantly lower than cf.-PWV EXT (MRI-PWV = 8.1 ± 2.9 vs. cf.-PWV EXT  = 10.9 ± 2.7 ms -1 ,p < 0.001). When cf.-PWV was recalculated using the inter-arterial distance from WB-MRA, this difference was significantly reduced but not lost (MRI-PWV = 8.1 ± 2.9 ms -1 vs. cf.-PWV MRA 9.1 ± 2.1 ms -1 , mean diff = -0.96 ± 2.52 ms -1 ,p = 0.001). Recalculation of the PWV increased correlation with age and pulse pressure. Differences in cf.-PWV and MRI PWV can be predominantly but not entirely explained by inaccuracies introduced by the use of simple surface measurements to represent the convoluted arterial path between the carotid and femoral arteries.

WE-G-BRD-09: Novel MRI Compatible Electron Accelerator for MRI-Linac Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whelan, B; Keall, P; Gierman, S

Purpose: MRI guided radiotherapy is a rapidly growing field; however current linacs are not designed to operate in MRI fringe fields. As such, current MRI- Linac systems require magnetic shielding, impairing MR image quality and system flexibility. Here, we present a bespoke electron accelerator concept with robust operation in in-line magnetic fields. Methods: For in-line MRI-Linac systems, electron gun performance is the major constraint on accelerator performance. To overcome this, we propose placing a cathode directly within the first accelerating cavity. Such a configuration is used extensively in high energy particle physics, but not previously for radiotherapy. Benchmarked computational modellingmore » (CST, Darmstadt, Germany) was employed to design and assess a 5.5 cell side coupled accelerator with a temperature limited thermionic cathode in the first accelerating cell. This simulation was coupled to magnetic fields from a 1T MRI model to assess robustness in magnetic fields for Source to Isocenter Distance between 1 and 2 meters. Performance was compared to a conventional electron gun based system in the same magnetic field. Results: A temperature limited cathode (work function 1.8eV, temperature 1245K, emission constant 60A/K/cm{sup 2}) will emit a mean current density of 24mA/mm{sup 2} (Richardson’s Law). We modeled a circular cathode with radius 2mm and mean current 300mA. Capture efficiency of the device was 43%, resulting in target current of 130 mA. The electron beam had a FWHM of 0.2mm, and mean energy of 5.9MeV (interquartile spread of 0.1MeV). Such an electron beam is suitable for radiotherapy, comparing favourably to conventional systems. This model was robust to operation the MRI fringe field, with a maximum current loss of 6% compared to 85% for the conventional system. Conclusion: The bespoke electron accelerator is robust to operation in in-line magnetic fields. This will enable MRI-Linacs with no accelerator magnetic shielding, and minimise painstaking optimisation of the MRI fringe field. This work was supported by US (NIH) and Australian (NHMRC & Cancer Institute NSW) government research funding. In addition, I would like to thank cancer institute NSW and the Ingham Institute for scholarship support.« less

The Usefulness of Zone Division Using Belt Partition at the Entry Zone of MRI Machine Room: An Analysis of the Restrictive Effect of Dangerous Action Using a Questionnaire.

PubMed

Funada, Tatsuro; Shibuya, Tsubasa

2016-08-01

The American College of Radiology recommends dividing magnetic resonance imaging (MRI) machine rooms into four zones depending on the education level. However, structural limitations restrict us to apply such recommendation in most of the Japanese facilities. This study examines the effectiveness of the usage of a belt partition to create the zonal division by a questionnaire survey including three critical parameters. They are, the influence of individuals' background (relevance to MRI, years of experience, individuals' post, occupation [i.e., nurse or nursing assistant], outpatient section or ward), the presence or absence of a door or belt partition (opening or closing), and any four personnel scenarios that may be encountered during a visit to an MRI site (e.g., from visiting the MRI site to receive a patient) . In this survey, the influence of dangerous action is uncertain on individuals' backgrounds (maximum odds ratio: 6.3, 95% CI: 1.47-27.31) and the scenarios of personnel (maximum risk ratio: 2.4, 95% CI: 1.16-4.85). Conversely, the presence of the door and belt partition influences significantly (maximum risk ratio: 17.4, 95% CI: 7.94-17.38). For that reason, we suggest that visual impression has a strong influence on an individuals' actions. Even if structural limitations are present, zonal division by belt partition will provide a visual deterrent. Then, the partitioned zone will serve as a buffer zone. We conclude that if the belt partition is used properly, it is an inexpensive and effective safety management device for MRI rooms.

Methods of the pharmacological imaging of the cannabinoid system (PhICS) study: towards understanding the role of the brain endocannabinoid system in human cognition.

PubMed

van Hell, Hendrika H; Bossong, Matthijs G; Jager, Gerry; Kahn, René S; Ramsey, Nick F

2011-03-01

Various lines of (pre)clinical research indicate that cannabinoid agents carry the potential for therapeutic application to reduce symptoms in several psychiatric disorders. However, direct testing of the involvement of cannabinoid brain systems in psychiatric syndromes is essential for further development. In the Pharmacological Imaging of the Cannabinoid System (PhICS) study, the involvement of the endocannabinoid system in cognitive brain function is assessed by comparing acute effects of the cannabinoid agonist Δ9-tetrahydrocannabinol (THC) on brain function between healthy controls and groups of psychiatric patients showing cognitive dysfunction. This article describes the objectives and methods of the PhICS study and presents preliminary results of the administration procedure on subjective and neurophysiological parameters. Core elements in the methodology of PhICS are the administration method (THC is administered by inhalation using a vaporizing device) and a comprehensive use of pharmacological magnetic resonance imaging (phMRI) combining several types of MRI scans including functional MRI (fMRI), Arterial Spin Labeling (ASL) to measure brain perfusion, and resting-state fMRI. Additional methods like neuropsychological testing further specify the exact role of the endocannabinoid system in regulating cognition. Preliminary results presented in this paper indicate robust behavioral and subjective effects of THC. In addition, fMRI paradigms demonstrate activation of expected networks of brain regions in the cognitive domains of interest. The presented administration and assessment protocol provides a basis for further research on the involvement of the endocannabionoid systems in behavior and in psychopathology, which in turn may lead to development of therapeutic opportunities of cannabinoid ligands. Copyright © 2011 John Wiley & Sons, Ltd.

An MRI Scan of the nucleus

NASA Astrophysics Data System (ADS)

Hoffman, Calem

2017-09-01

In the pursuit of a global description of nuclei, extensive experimental studies on short-lived isotopes have provided a wealth of new empirical information. Such data has been used to test theoretical concepts and in the development of innovative ideas. More directly, a novel device at Argonne National Laboratory, the HELIcal Orbit Spectrometer (HELIOS), was focused on providing detailed single-particle information on the malleability of the nuclear magic numbers. Once thought as immovable pillars in nuclear structure, the shell-gaps in nuclei defining magic numbers of nucleons are now well-known to evolve as proton-to-neutron ratios change. And, determination of the underlying components of the nuclear force driving the evolution is at the forefront of nuclear structure research. Additionally, the HELIOS device mentioned above also carries its own aura being that it is formed by a decommissioned MRI solenoid magnet. In this talk recent highlights and advancements in our description of nuclear shell evolution will be the focus along with a few sidestepping comments on the life-cycle and interplay between basic research and the applications of nuclear physics. This material is based upon work supported by the U.S. Department of Energy, Office of Science, under Contract Number DE-AC02-06CH11357.

The Perfect Neuroimaging-Genetics-Computation Storm: Collision of Petabytes of Data, Millions of Hardware Devices and Thousands of Software Tools

PubMed Central

Dinov, Ivo D.; Petrosyan, Petros; Liu, Zhizhong; Eggert, Paul; Zamanyan, Alen; Torri, Federica; Macciardi, Fabio; Hobel, Sam; Moon, Seok Woo; Sung, Young Hee; Jiang, Zhiguo; Labus, Jennifer; Kurth, Florian; Ashe-McNalley, Cody; Mayer, Emeran; Vespa, Paul M.; Van Horn, John D.; Toga, Arthur W.

2013-01-01

The volume, diversity and velocity of biomedical data are exponentially increasing providing petabytes of new neuroimaging and genetics data every year. At the same time, tens-of-thousands of computational algorithms are developed and reported in the literature along with thousands of software tools and services. Users demand intuitive, quick and platform-agnostic access to data, software tools, and infrastructure from millions of hardware devices. This explosion of information, scientific techniques, computational models, and technological advances leads to enormous challenges in data analysis, evidence-based biomedical inference and reproducibility of findings. The Pipeline workflow environment provides a crowd-based distributed solution for consistent management of these heterogeneous resources. The Pipeline allows multiple (local) clients and (remote) servers to connect, exchange protocols, control the execution, monitor the states of different tools or hardware, and share complete protocols as portable XML workflows. In this paper, we demonstrate several advanced computational neuroimaging and genetics case-studies, and end-to-end pipeline solutions. These are implemented as graphical workflow protocols in the context of analyzing imaging (sMRI, fMRI, DTI), phenotypic (demographic, clinical), and genetic (SNP) data. PMID:23975276

Magnetic resonance imaging of athletic pubalgia and the sports hernia: current understanding and practice.

PubMed

Khan, Waseem; Zoga, Adam C; Meyers, William C

2013-02-01

Magnetic resonance imaging (MRI) has become the standard imaging modality for activity-related groin pain. Lesions, including rectus abdominis/adductor aponeurosis injury and osteitis pubis, can be accurately identified and delineated in patients with clinical conditions termed athletic pubalgia, core injury, and sports hernia. A dedicated noncontrast athletic pubalgia MRI protocol is easy to implement and should be available at musculoskeletal MR imaging centers. This article will review pubic anatomy, imaging considerations, specific lesions, and common MRI findings encountered in the setting of musculoskeletal groin pain. Copyright © 2013 Elsevier Inc. All rights reserved.

Regional myocardial oxygen tension: 19F MRI of sequestered perfluorocarbon.

PubMed

Shukla, H P; Mason, R P; Bansal, N; Antich, P P

1996-06-01

A novel noninvasive method of measuring local myocardial oxygen tension (pO2) in the perfused rat heart using 19F MRI is demonstrated. Tissue pO2 was determined on the basis of the 19F spin-lattice relaxation rate (R1) of perflubron (perfluorooctyl bromide) sequestered in the heart after IV infusion of an emulsion. Spectroscopic measurement of R1 was previously used to measure a global weighted average of oxygen status. 19F MRI now provides 3D spatial resolution indicating local cardiac pO2 under normally perfused, globally ischemic, and regionally ischemic conditions.

Magnetic resonance imaging for the ophthalmologist: A primer

PubMed Central

Simha, Arathi; Irodi, Aparna; David, Sarada

2012-01-01

Magnetic resonance imaging (MRI) and computerized tomography (CT) have added a new dimension in the diagnosis and management of ocular and orbital diseases. Although CT is more widely used, MRI is the modality of choice in select conditions and can be complimentary to CT in certain situations. The diagnostic yield is best when the ophthalmologist and radiologist work together. Ophthalmologists should be able to interpret these complex imaging modalities as better clinical correlation is then possible. In this article, we attempt to describe the basic principles of MRI and its interpretation, avoiding confusing technical terms. PMID:22824600

Correlation of oxygenation and perfusion sensitive MRI with invasive micro probe measurements in healthy mice brain.

PubMed

Sedlacik, Jan; Reitz, Matthias; Bolar, Divya S; Adalsteinsson, Elfar; Schmidt, Nils O; Fiehler, Jens

2015-03-01

The non-invasive assessment of (patho-)physiological parameters such as, perfusion and oxygenation, is of great importance for the characterization of pathologies e.g., tumors, which may be helpful to better predict treatment response and potential outcome. To better understand the influence of physiological parameters on the investigated oxygenation and perfusion sensitive MRI methods, MRI measurements were correlated with subsequent invasive micro probe measurements during free breathing conditions of air, air+10% CO2 and 100% O2 in healthy mice brain. MRI parameters were the irreversible (R2), reversible (R2') and effective (R2*) transverse relaxation rates, venous blood oxygenation level assessed by quantitative blood oxygenation level dependent (qBOLD) method and cerebral blood flow (CBF) assessed by arterial spin labeling (ASL) using a 7 T small animal MRI scanner. One to two days after MRI, tissue perfusion and pO2 were measured by Laser-Doppler flowmetry and fluorescence quenching micro probes, respectively. The tissue pO2 values were converted to blood oxygen saturation by using the Hill equation. The animals were anesthetized by intra peritoneal injection of ketamine-xylazine-acepromazine (10-2-0.3 mg/ml · kg). Results for normal/hypercapnia/hyperoxia conditions were: R2[s(∧)-1] = 20.7/20.4/20.1, R2*[s(∧)-1] = 31.6/29.6/25.9, R2'[s-(∧)1] = 10.9/9.2/5.7, qBOLD venous blood oxygenation level = 0.43/0.51/0.56, CBF[ml · min(∧)-1 · 100 g(∧)-1] = 70.6/105.5/81.8, Laser-Doppler flowmetry[a.u.] = 89.2/120.2/90.6 and pO2[mmHg] = 6.3/32.3/46.7. All parameters were statistically significantly different with P < 0.001 between all breathing conditions. All MRI and the corresponding micro probe measurements were also statistically significantly (P ≤ 0.03) correlated with each other. However, converting the tissue pO2 to blood oxygen saturation = 0.02/0.34/0.63, showed only very limited agreement with the qBOLD venous blood oxygenation level. We found good correlation between MRI and micro probe measurements. However, direct conversion of tissue pO2 to blood oxygen saturation by using the Hill equation is very limited. Furthermore, adverse effects of anesthesia and trauma due to micro probe insertion are strong confounding factors and need close attention for study planning and conduction of experiments. Investigation of the correlation of perfusion and oxygenation sensitive MRI methods with micro probe measurements in pathologic tissue such as tumors is now of compelling interest. Copyright © 2014. Published by Elsevier GmbH.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, Petra L., E-mail: Petra.Williams@phnt.swest.nhs.uk; Coote, Jacky M.; Watkinson, Anthony F.

Uterine leiomyomata, or fibroids, although benign, cause debilitating symptoms in many women. Symptoms are often nonspecific and may be the presenting complaint in a number of other conditions. Furthermore, because the presence of fibroids may be coincident with other symptomatic conditions that result in similar complaints, there may be diagnostic difficulty and consequent difficulty in planning therapeutic strategy. Uterine artery embolization (UAE) is a safe and effective treatment for symptomatic fibroids and is increasingly being performed. Magnetic resonance imaging (MRI) evaluation before and after treatment is routine practice with the potential to significantly alter management in up to a fifthmore » of patients. It is well recognized that significant incidental findings may be demonstrated during imaging investigations, and in particular that abnormalities that are not directly related to the clinical question may be overlooked. Radiologists evaluating pre-UAE MRI studies must be aware of the MRI appearances of gynecological pathologies that may cause similar symptoms or that may affect the success or complication rates of UAE, and they must also be wary of 'satisfaction of search,' reviewing imaging thoroughly so that relevant other pathologies are not missed. We demonstrate the appearances of coincidental pathologies found on pre-UAE MRI, with the potential to change patient management.« less

Quantitative evaluation of sputtering induced surface roughness and its influence on AES depth profiles of polycrystalline Ni/Cu multilayer thin films

NASA Astrophysics Data System (ADS)

Yan, X. L.; Coetsee, E.; Wang, J. Y.; Swart, H. C.; Terblans, J. J.

2017-07-01

The polycrystalline Ni/Cu multilayer thin films consisting of 8 alternating layers of Ni and Cu were deposited on a SiO2 substrate by means of electron beam evaporation in a high vacuum. Concentration-depth profiles of the as-deposited multilayered Ni/Cu thin films were determined with Auger electron spectroscopy (AES) in combination with Ar+ ion sputtering, under various bombardment conditions with the samples been stationary as well as rotating in some cases. The Mixing-Roughness-Information depth (MRI) model used for the fittings of the concentration-depth profiles accounts for the interface broadening of the experimental depth profiling. The interface broadening incorporates the effects of atomic mixing, surface roughness and information depth of the Auger electrons. The roughness values extracted from the MRI model fitting of the depth profiling data agrees well with those measured by atomic force microscopy (AFM). The ion sputtering induced surface roughness during the depth profiling was accordingly quantitatively evaluated from the fitted MRI parameters with sample rotation and stationary conditions. The depth resolutions of the AES depth profiles were derived directly from the values determined by the fitting parameters in the MRI model.

Splenomegaly Segmentation using Global Convolutional Kernels and Conditional Generative Adversarial Networks

PubMed Central

Huo, Yuankai; Xu, Zhoubing; Bao, Shunxing; Bermudez, Camilo; Plassard, Andrew J.; Liu, Jiaqi; Yao, Yuang; Assad, Albert; Abramson, Richard G.; Landman, Bennett A.

2018-01-01

Spleen volume estimation using automated image segmentation technique may be used to detect splenomegaly (abnormally enlarged spleen) on Magnetic Resonance Imaging (MRI) scans. In recent years, Deep Convolutional Neural Networks (DCNN) segmentation methods have demonstrated advantages for abdominal organ segmentation. However, variations in both size and shape of the spleen on MRI images may result in large false positive and false negative labeling when deploying DCNN based methods. In this paper, we propose the Splenomegaly Segmentation Network (SSNet) to address spatial variations when segmenting extraordinarily large spleens. SSNet was designed based on the framework of image-to-image conditional generative adversarial networks (cGAN). Specifically, the Global Convolutional Network (GCN) was used as the generator to reduce false negatives, while the Markovian discriminator (PatchGAN) was used to alleviate false positives. A cohort of clinically acquired 3D MRI scans (both T1 weighted and T2 weighted) from patients with splenomegaly were used to train and test the networks. The experimental results demonstrated that a mean Dice coefficient of 0.9260 and a median Dice coefficient of 0.9262 using SSNet on independently tested MRI volumes of patients with splenomegaly.

Comparing cerebral perfusion in Alzheimer's disease and Parkinson's disease dementia: an ASL-MRI study.

PubMed

Le Heron, Campbell J; Wright, Sarah L; Melzer, Tracy R; Myall, Daniel J; MacAskill, Michael R; Livingston, Leslie; Keenan, Ross J; Watts, Richard; Dalrymple-Alford, John C; Anderson, Tim J

2014-06-01

Emerging evidence suggests that Alzheimer's disease (AD) and Parkinson's disease dementia (PDD) share neurodegenerative mechanisms. We sought to directly compare cerebral perfusion in these two conditions using arterial spin labeling magnetic resonance imaging (ASL-MRI). In total, 17 AD, 20 PDD, and 37 matched healthy controls completed ASL and structural MRI, and comprehensive neuropsychological testing. Alzheimer's disease and PDD perfusion was analyzed by whole-brain voxel-based analysis (to assess absolute blood flow), a priori specified region of interest analysis, and principal component analysis (to generate a network differentiating the two groups). Corrections were made for cerebral atrophy, age, sex, education, and MRI scanner software version. Analysis of absolute blood flow showed no significant differences between AD and PDD. Comparing each group with controls revealed an overlapping, posterior pattern of hypoperfusion, including posterior cingulate gyrus, precuneus, and occipital regions. The perfusion network that differentiated AD and PDD groups identified relative differences in medial temporal lobes (AD

[Factors for Degaussing of a Cochlear Implant Magnet in the MR Scanner].

PubMed

Koganezawa, Takumi; Uchiyama, Naoko; Teshigawara, Mai; Ogura, Akio

This study examined the conditions influencing degauss of the magnet using magnetic resonance imaging (MRI). Poly methyl methacrylate (PMMA) was used to fix the measurement magnets to the MRI bed at angles from 0° to 180° for the magnetic flux vector of static magnetic field. The PMMA was moved in the MRI magnetic field. Magnetic flux density was measured before and after bed movement, and the rate of degauss was calculated. The contents examined are as follows: (1) the angle of the magnetic flux vector of the measurement magnets for the magnetic flux vector of the static magnetic field, (2) the number of movements, (3) moving velocity, and (4) the movement on the spatial gradient of magnetic field. Mann-Whitney U test was used for statistical analysis of the data. In conclusion, the effect of the angle of the magnetic flux vector of the implant magnet was high under the conditions of degauss in this study. Therefore, during the MRI examination of a patient with a cochlear implant magnet, the operators identified the directions of the magnetic flux vector and static magnetic field of the implant magnet.

TU-EF-BRA-02: Longitudinal Proton Spin Relaxation and T1-Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemen, L.

NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm.more » MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common applications of MRI exploit its capability to detect and image distinct movements of fluids: MR angiography (MRA), which rivals CT angiography but often requires no contrast medium, monitors the bulk flow of blood; functional MRI ( f MRI), distinguishes the perfusion of oxygenated blood from that of de-oxygenated, and lights up parts of the brain that are activated by a stimulus, rather like PET; and diffusion tensor imaging (DTI) indicates the diffusion of free water along tracts of axons, thereby bringing nerve trunks into view. There are variants on all of these themes, and on others as well. Magnetic Resonance Spectroscopy (MRS), for example, can perform non-invasive ‘virtual biopsies’ that allow identification of certain cancers and other lesions. And an MRI-guided needle biopsy can sample brain tissue from a region only millimeters in dimensions. MRI, however, involves deeper and more complex aspects of physics, technology, and biology than do most other imaging modalities, and it is widely considered to be correspondingly more difficult to learn. We could probably cover all of this rather comprehensively if we had 50 hours available rather than 2 ̶ but, to paraphrase a former Secretary of Defense, you tell your story in the time you have allotted. The four presenters and another physicist, Kevin King from GE, have combined their efforts to co-author a single slide show that describes essentials of MRI as simply as possible. It is obviously far from thorough, but hopefully it will succeed in explaining some of the basics in a simplified but still valid fashion; in providing a taste of the numerous capabilities and complexities of the modality; and in whetting your appetite to learn more. Part I. NMR, and Proton Density MRI of the 1D Patient (Wolbarst), begins with an introductory case study that illustrates a half dozen ways in which MRI provides valuable clinical information. It then explores the nuclear magnetic resonance (NMR) phenomenon, which underlies MRI. NMR can be introduced with either of two approaches. In the first, one thinks (loosely) of the nuclei of hydrogen atoms as (rotating and charged and therefore) magnetic objects, whose spin-axes tend to align in a strong external magnetic field, much like a compass needle. As with the Bohr atom, this spin-up/spin-down picture is a highly abridged version of the full quantum mechanical treatment, but still it leads to some useful, legitimate pictures of the NMR process occurring within a voxel: When RF photons of the correct (Larmor) frequency elevate protons in a fixed magnetic field out of their lower-energy spin state into the upper, the NMR phenomenon is indicated by the detectable absorption of RF power. With the addition of a linear gradient field along a multi-voxel, one-dimensional patient/phantom, as well, we can determine the water content of each compartment – an example of a real MRI study, albeit in 1D. Part I concludes with a discussion of the net magnetization at position x, m0(x), under conditions of dynamic thermal equilibrium, which leads into: Part II. Net Voxel Magnetization, m(x,t); T1-MRI; The MRI Device (Lemen), investigates the biophysics of the form of proton spin relaxation process characterized by the time T1. It then moves on to the creation of an MR image that displays the spatial variation in the values of this clinically relevant parameter, again in 1D. Finally, the design and workings of a clinical MRI machine are sketched, in preparation for: Part III. ‘Classical’ NMR; FID Imaging in 1D via k-Space (Yanasak) presents the second standard approach to NMR and MRI, the classical model. It focuses on the time dependence of the net nuclear magnetization, m(x,t), the overall magnetic field generated by the cohort of protons in the voxel at position x. Quite remarkably, this nuclear net magnetization itself acts in a strong magnetic field like a gyroscope in a gravitational field. This tack is better for explaining Free Induction Decay (FID), which involves a brief introduction to the Fourier transform and k-space. This leads to conventional Spin-Echo (S-E) reconstruction techniques for creating clinical images from raw data, and sets the stage for: Part IV. Spin-Echo; S-E / Spin Warp in a 2D Slice (Price) discusses application of the S- E sequence of radiofrequency pulses and gradient magnetic fields to the 1D patient. T2 is introduced but not explained. This Part also considers how to manipulate the image acquisition parameters so as to generate clinical pictures with contrast dominated by spatial variations in PD, T1, or T2. We conclude by demonstrating the spin-warp approach to imaging in 2D with a simple 2×2, 4-voxel example. Much of this material is presented in more detail in the chapter “MRI of the One-dimensional Patient, Part I”, in Advances in Medical Physics, Vol 5 (2014). Copies are on display at the Medical Physics Publishing booth. Learning Objectives: The participant will learn about the processes of NMR and T1 spin relaxation in a tissue voxel in a uniform magnetic field. The participant will learn about combining spin-up/spin-down NMR and T1 processes with a linear gradient to effect frequency-encoding of voxel spatial position. This approach can be used to create proton density and T1 MRI maps, respectively, of the contents of multi-voxel 1D phantoms. The participant will learn about how the ‘classical’ model of NMR it can generate Free Induction Decay (FID) images of 1D phantoms, which involves the use of the Fourier transform in k-space. This can lead simply into standard Spin-Echo images. The participant will learn about extending Spin-Echo imaging into 2 and more dimensions.« less

TU-EF-BRA-04: Into 2, 3, and 4 Dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yanasak, N.

NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm.more » MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common applications of MRI exploit its capability to detect and image distinct movements of fluids: MR angiography (MRA), which rivals CT angiography but often requires no contrast medium, monitors the bulk flow of blood; functional MRI ( f MRI), distinguishes the perfusion of oxygenated blood from that of de-oxygenated, and lights up parts of the brain that are activated by a stimulus, rather like PET; and diffusion tensor imaging (DTI) indicates the diffusion of free water along tracts of axons, thereby bringing nerve trunks into view. There are variants on all of these themes, and on others as well. Magnetic Resonance Spectroscopy (MRS), for example, can perform non-invasive ‘virtual biopsies’ that allow identification of certain cancers and other lesions. And an MRI-guided needle biopsy can sample brain tissue from a region only millimeters in dimensions. MRI, however, involves deeper and more complex aspects of physics, technology, and biology than do most other imaging modalities, and it is widely considered to be correspondingly more difficult to learn. We could probably cover all of this rather comprehensively if we had 50 hours available rather than 2 ̶ but, to paraphrase a former Secretary of Defense, you tell your story in the time you have allotted. The four presenters and another physicist, Kevin King from GE, have combined their efforts to co-author a single slide show that describes essentials of MRI as simply as possible. It is obviously far from thorough, but hopefully it will succeed in explaining some of the basics in a simplified but still valid fashion; in providing a taste of the numerous capabilities and complexities of the modality; and in whetting your appetite to learn more. Part I. NMR, and Proton Density MRI of the 1D Patient (Wolbarst), begins with an introductory case study that illustrates a half dozen ways in which MRI provides valuable clinical information. It then explores the nuclear magnetic resonance (NMR) phenomenon, which underlies MRI. NMR can be introduced with either of two approaches. In the first, one thinks (loosely) of the nuclei of hydrogen atoms as (rotating and charged and therefore) magnetic objects, whose spin-axes tend to align in a strong external magnetic field, much like a compass needle. As with the Bohr atom, this spin-up/spin-down picture is a highly abridged version of the full quantum mechanical treatment, but still it leads to some useful, legitimate pictures of the NMR process occurring within a voxel: When RF photons of the correct (Larmor) frequency elevate protons in a fixed magnetic field out of their lower-energy spin state into the upper, the NMR phenomenon is indicated by the detectable absorption of RF power. With the addition of a linear gradient field along a multi-voxel, one-dimensional patient/phantom, as well, we can determine the water content of each compartment – an example of a real MRI study, albeit in 1D. Part I concludes with a discussion of the net magnetization at position x, m0(x), under conditions of dynamic thermal equilibrium, which leads into: Part II. Net Voxel Magnetization, m(x,t); T1-MRI; The MRI Device (Lemen), investigates the biophysics of the form of proton spin relaxation process characterized by the time T1. It then moves on to the creation of an MR image that displays the spatial variation in the values of this clinically relevant parameter, again in 1D. Finally, the design and workings of a clinical MRI machine are sketched, in preparation for: Part III. ‘Classical’ NMR; FID Imaging in 1D via k-Space (Yanasak) presents the second standard approach to NMR and MRI, the classical model. It focuses on the time dependence of the net nuclear magnetization, m(x,t), the overall magnetic field generated by the cohort of protons in the voxel at position x. Quite remarkably, this nuclear net magnetization itself acts in a strong magnetic field like a gyroscope in a gravitational field. This tack is better for explaining Free Induction Decay (FID), which involves a brief introduction to the Fourier transform and k-space. This leads to conventional Spin-Echo (S-E) reconstruction techniques for creating clinical images from raw data, and sets the stage for: Part IV. Spin-Echo; S-E / Spin Warp in a 2D Slice (Price) discusses application of the S- E sequence of radiofrequency pulses and gradient magnetic fields to the 1D patient. T2 is introduced but not explained. This Part also considers how to manipulate the image acquisition parameters so as to generate clinical pictures with contrast dominated by spatial variations in PD, T1, or T2. We conclude by demonstrating the spin-warp approach to imaging in 2D with a simple 2×2, 4-voxel example. Much of this material is presented in more detail in the chapter “MRI of the One-dimensional Patient, Part I”, in Advances in Medical Physics, Vol 5 (2014). Copies are on display at the Medical Physics Publishing booth. Learning Objectives: The participant will learn about the processes of NMR and T1 spin relaxation in a tissue voxel in a uniform magnetic field. The participant will learn about combining spin-up/spin-down NMR and T1 processes with a linear gradient to effect frequency-encoding of voxel spatial position. This approach can be used to create proton density and T1 MRI maps, respectively, of the contents of multi-voxel 1D phantoms. The participant will learn about how the ‘classical’ model of NMR it can generate Free Induction Decay (FID) images of 1D phantoms, which involves the use of the Fourier transform in k-space. This can lead simply into standard Spin-Echo images. The participant will learn about extending Spin-Echo imaging into 2 and more dimensions.« less

TU-EF-BRA-00: MR Basics I

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm.more » MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common applications of MRI exploit its capability to detect and image distinct movements of fluids: MR angiography (MRA), which rivals CT angiography but often requires no contrast medium, monitors the bulk flow of blood; functional MRI (f MRI), distinguishes the perfusion of oxygenated blood from that of de-oxygenated, and lights up parts of the brain that are activated by a stimulus, rather like PET; and diffusion tensor imaging (DTI) indicates the diffusion of free water along tracts of axons, thereby bringing nerve trunks into view. There are variants on all of these themes, and on others as well. Magnetic Resonance Spectroscopy (MRS), for example, can perform non-invasive ‘virtual biopsies’ that allow identification of certain cancers and other lesions. And an MRI-guided needle biopsy can sample brain tissue from a region only millimeters in dimensions. MRI, however, involves deeper and more complex aspects of physics, technology, and biology than do most other imaging modalities, and it is widely considered to be correspondingly more difficult to learn. We could probably cover all of this rather comprehensively if we had 50 hours available rather than 2 ̶ but, to paraphrase a former Secretary of Defense, you tell your story in the time you have allotted. The four presenters and another physicist, Kevin King from GE, have combined their efforts to co-author a single slide show that describes essentials of MRI as simply as possible. It is obviously far from thorough, but hopefully it will succeed in explaining some of the basics in a simplified but still valid fashion; in providing a taste of the numerous capabilities and complexities of the modality; and in whetting your appetite to learn more. Part I. NMR, and Proton Density MRI of the 1D Patient (Wolbarst), begins with an introductory case study that illustrates a half dozen ways in which MRI provides valuable clinical information. It then explores the nuclear magnetic resonance (NMR) phenomenon, which underlies MRI. NMR can be introduced with either of two approaches. In the first, one thinks (loosely) of the nuclei of hydrogen atoms as (rotating and charged and therefore) magnetic objects, whose spin-axes tend to align in a strong external magnetic field, much like a compass needle. As with the Bohr atom, this spin-up/spin-down picture is a highly abridged version of the full quantum mechanical treatment, but still it leads to some useful, legitimate pictures of the NMR process occurring within a voxel: When RF photons of the correct (Larmor) frequency elevate protons in a fixed magnetic field out of their lower-energy spin state into the upper, the NMR phenomenon is indicated by the detectable absorption of RF power. With the addition of a linear gradient field along a multi-voxel, one-dimensional patient/phantom, as well, we can determine the water content of each compartment – an example of a real MRI study, albeit in 1D. Part I concludes with a discussion of the net magnetization at position x, m0(x), under conditions of dynamic thermal equilibrium, which leads into: Part II. Net Voxel Magnetization, m(x,t); T1-MRI; The MRI Device (Lemen), investigates the biophysics of the form of proton spin relaxation process characterized by the time T1. It then moves on to the creation of an MR image that displays the spatial variation in the values of this clinically relevant parameter, again in 1D. Finally, the design and workings of a clinical MRI machine are sketched, in preparation for: Part III. ‘Classical’ NMR; FID Imaging in 1D via k-Space (Yanasak) presents the second standard approach to NMR and MRI, the classical model. It focuses on the time dependence of the net nuclear magnetization, m(x,t), the overall magnetic field generated by the cohort of protons in the voxel at position x. Quite remarkably, this nuclear net magnetization itself acts in a strong magnetic field like a gyroscope in a gravitational field. This tack is better for explaining Free Induction Decay (FID), which involves a brief introduction to the Fourier transform and k-space. This leads to conventional Spin-Echo (S-E) reconstruction techniques for creating clinical images from raw data, and sets the stage for: Part IV. Spin-Echo; S-E / Spin Warp in a 2D Slice (Price) discusses application of the S- E sequence of radiofrequency pulses and gradient magnetic fields to the 1D patient. T2 is introduced but not explained. This Part also considers how to manipulate the image acquisition parameters so as to generate clinical pictures with contrast dominated by spatial variations in PD, T1, or T2. We conclude by demonstrating the spin-warp approach to imaging in 2D with a simple 2×2, 4-voxel example. Much of this material is presented in more detail in the chapter “MRI of the One-dimensional Patient, Part I”, in Advances in Medical Physics, Vol 5 (2014). Copies are on display at the Medical Physics Publishing booth. Learning Objectives: The participant will learn about the processes of NMR and T1 spin relaxation in a tissue voxel in a uniform magnetic field. The participant will learn about combining spin-up/spin-down NMR and T1 processes with a linear gradient to effect frequency-encoding of voxel spatial position. This approach can be used to create proton density and T1 MRI maps, respectively, of the contents of multi-voxel 1D phantoms. The participant will learn about how the ‘classical’ model of NMR it can generate Free Induction Decay (FID) images of 1D phantoms, which involves the use of the Fourier transform in k-space. This can lead simply into standard Spin-Echo images. The participant will learn about extending Spin-Echo imaging into 2 and more dimensions.« less

TU-EF-BRA-03: Free Induction Decay (without the Decay) and Spin-Echo Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Price, R.

NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm.more » MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common applications of MRI exploit its capability to detect and image distinct movements of fluids: MR angiography (MRA), which rivals CT angiography but often requires no contrast medium, monitors the bulk flow of blood; functional MRI ( f MRI), distinguishes the perfusion of oxygenated blood from that of de-oxygenated, and lights up parts of the brain that are activated by a stimulus, rather like PET; and diffusion tensor imaging (DTI) indicates the diffusion of free water along tracts of axons, thereby bringing nerve trunks into view. There are variants on all of these themes, and on others as well. Magnetic Resonance Spectroscopy (MRS), for example, can perform non-invasive ‘virtual biopsies’ that allow identification of certain cancers and other lesions. And an MRI-guided needle biopsy can sample brain tissue from a region only millimeters in dimensions. MRI, however, involves deeper and more complex aspects of physics, technology, and biology than do most other imaging modalities, and it is widely considered to be correspondingly more difficult to learn. We could probably cover all of this rather comprehensively if we had 50 hours available rather than 2 ̶ but, to paraphrase a former Secretary of Defense, you tell your story in the time you have allotted. The four presenters and another physicist, Kevin King from GE, have combined their efforts to co-author a single slide show that describes essentials of MRI as simply as possible. It is obviously far from thorough, but hopefully it will succeed in explaining some of the basics in a simplified but still valid fashion; in providing a taste of the numerous capabilities and complexities of the modality; and in whetting your appetite to learn more. Part I. NMR, and Proton Density MRI of the 1D Patient (Wolbarst), begins with an introductory case study that illustrates a half dozen ways in which MRI provides valuable clinical information. It then explores the nuclear magnetic resonance (NMR) phenomenon, which underlies MRI. NMR can be introduced with either of two approaches. In the first, one thinks (loosely) of the nuclei of hydrogen atoms as (rotating and charged and therefore) magnetic objects, whose spin-axes tend to align in a strong external magnetic field, much like a compass needle. As with the Bohr atom, this spin-up/spin-down picture is a highly abridged version of the full quantum mechanical treatment, but still it leads to some useful, legitimate pictures of the NMR process occurring within a voxel: When RF photons of the correct (Larmor) frequency elevate protons in a fixed magnetic field out of their lower-energy spin state into the upper, the NMR phenomenon is indicated by the detectable absorption of RF power. With the addition of a linear gradient field along a multi-voxel, one-dimensional patient/phantom, as well, we can determine the water content of each compartment – an example of a real MRI study, albeit in 1D. Part I concludes with a discussion of the net magnetization at position x, m0(x), under conditions of dynamic thermal equilibrium, which leads into: Part II. Net Voxel Magnetization, m(x,t); T1-MRI; The MRI Device (Lemen), investigates the biophysics of the form of proton spin relaxation process characterized by the time T1. It then moves on to the creation of an MR image that displays the spatial variation in the values of this clinically relevant parameter, again in 1D. Finally, the design and workings of a clinical MRI machine are sketched, in preparation for: Part III. ‘Classical’ NMR; FID Imaging in 1D via k-Space (Yanasak) presents the second standard approach to NMR and MRI, the classical model. It focuses on the time dependence of the net nuclear magnetization, m(x,t), the overall magnetic field generated by the cohort of protons in the voxel at position x. Quite remarkably, this nuclear net magnetization itself acts in a strong magnetic field like a gyroscope in a gravitational field. This tack is better for explaining Free Induction Decay (FID), which involves a brief introduction to the Fourier transform and k-space. This leads to conventional Spin-Echo (S-E) reconstruction techniques for creating clinical images from raw data, and sets the stage for: Part IV. Spin-Echo; S-E / Spin Warp in a 2D Slice (Price) discusses application of the S- E sequence of radiofrequency pulses and gradient magnetic fields to the 1D patient. T2 is introduced but not explained. This Part also considers how to manipulate the image acquisition parameters so as to generate clinical pictures with contrast dominated by spatial variations in PD, T1, or T2. We conclude by demonstrating the spin-warp approach to imaging in 2D with a simple 2×2, 4-voxel example. Much of this material is presented in more detail in the chapter “MRI of the One-dimensional Patient, Part I”, in Advances in Medical Physics, Vol 5 (2014). Copies are on display at the Medical Physics Publishing booth. Learning Objectives: The participant will learn about the processes of NMR and T1 spin relaxation in a tissue voxel in a uniform magnetic field. The participant will learn about combining spin-up/spin-down NMR and T1 processes with a linear gradient to effect frequency-encoding of voxel spatial position. This approach can be used to create proton density and T1 MRI maps, respectively, of the contents of multi-voxel 1D phantoms. The participant will learn about how the ‘classical’ model of NMR it can generate Free Induction Decay (FID) images of 1D phantoms, which involves the use of the Fourier transform in k-space. This can lead simply into standard Spin-Echo images. The participant will learn about extending Spin-Echo imaging into 2 and more dimensions.« less

[Exposure to static magnetic field and health hazards during the operation of magnetic resonance scanners].

PubMed

Karpowicz, Jolanta; Gryz, Krzysztof; Politański, Piotr; Zmyślony, Marek

2011-01-01

Magnetic resonance imaging (MRI) scanners belong to the most modern imaging diagnostic devices, which involve workers' exposure to static magnetic fields (SMF) during the preparation and performance of MRI examinations. This paper presents the data on workers' exposure to SMF in the vicinity of MRI scanners and the analysis of SMF-related biological effects and health hazards to find out whether softening the legislative requirements concerning protection against SMF exposure of workers involved in MRI diagnostics is justified. Measurements in the vicinity of 1.5 T MRI magnets showed that exposure to SMF by various scanners depends on both SMF of magnets and scanners design, as well as on work organization. In a routine examination of one patient the radiographer is exposed to SMF exceeding 0.5 mT for app. 1.5-7 min, and up to 1.3 min to SMF exceeding 70 mT. In examinations of patients who need more attention, the duration of exposure may be significantly longer. The mean values (B mean) of exposure to SMF are 5.6-85 mT (mean 30 +/- 19 mT, N = 16). These data demonstrate that only well designed procedures, proper organization of workplace and awareness of workers how to attend the patients without being exposed to strong SMF allow for meeting the requirements of labor law concerning workers' exposure to SMF. The analysis of the available literature on biological effects of SMF has disclosed the lack of data on health effects of many years exposure of workers and the abundance of data demonstrating the biological activity of SMF. Therefore, a radical softening of legislative requirements concerning the exposure of workers' head or trunk is premature, and what is more, it is not indispensable for the development of MRI diagnostic. Such an action should be preceded by extensive international investigations on the health status of workers exposed to electromagnetic fields by MRI scanners.

Distortion products in auditory fMRI research: Measurements and solutions.

PubMed

Norman-Haignere, Sam; McDermott, Josh H

2016-04-01

Nonlinearities in the cochlea can introduce audio frequencies that are not present in the sound signal entering the ear. Known as distortion products (DPs), these added frequencies complicate the interpretation of auditory experiments. Sound production systems also introduce distortion via nonlinearities, a particular concern for fMRI research because the Sensimetrics earphones widely used for sound presentation are less linear than most high-end audio devices (due to design constraints). Here we describe the acoustic and neural effects of cochlear and earphone distortion in the context of fMRI studies of pitch perception, and discuss how their effects can be minimized with appropriate stimuli and masking noise. The amplitude of cochlear and Sensimetrics earphone DPs were measured for a large collection of harmonic stimuli to assess effects of level, frequency, and waveform amplitude. Cochlear DP amplitudes were highly sensitive to the absolute frequency of the DP, and were most prominent at frequencies below 300 Hz. Cochlear DPs could thus be effectively masked by low-frequency noise, as expected. Earphone DP amplitudes, in contrast, were highly sensitive to both stimulus and DP frequency (due to prominent resonances in the earphone's transfer function), and their levels grew more rapidly with increasing stimulus level than did cochlear DP amplitudes. As a result, earphone DP amplitudes often exceeded those of cochlear DPs. Using fMRI, we found that earphone DPs had a substantial effect on the response of pitch-sensitive cortical regions. In contrast, cochlear DPs had a small effect on cortical fMRI responses that did not reach statistical significance, consistent with their lower amplitudes. Based on these findings, we designed a set of pitch stimuli optimized for identifying pitch-responsive brain regions using fMRI. These stimuli robustly drive pitch-responsive brain regions while producing minimal cochlear and earphone distortion, and will hopefully aid fMRI researchers in avoiding distortion confounds. Copyright © 2016 Elsevier Inc. All rights reserved.

Distortion Products in Auditory fMRI Research: Measurements and Solutions

PubMed Central

Norman-Haignere, Sam; McDermott, Josh H.

2016-01-01

Nonlinearities in the cochlea can introduce audio frequencies that are not present in the sound signal entering the ear. Known as distortion products (DPs), these added frequencies complicate the interpretation of auditory experiments. Sound production systems also introduce distortion via nonlinearities, a particular concern for fMRI research because the Sensimetrics earphones widely used for sound presentation are less linear than most high-end audio devices (due to design constraints). Here we describe the acoustic and neural effects of cochlear and earphone distortion in the context of fMRI studies of pitch perception, and discuss how their effects can be minimized with appropriate stimuli and masking noise. The amplitude of cochlear and Sensimetrics earphone DPs were measured for a large collection of harmonic stimuli to assess effects of level, frequency, and waveform amplitude. Cochlear DP amplitudes were highly sensitive to the absolute frequency of the DP, and were most prominent at frequencies below 300 Hz. Cochlear DPs could thus be effectively masked by low-frequency noise, as expected. Earphone DP amplitudes, in contrast, were highly sensitive to both stimulus and DP frequency (due to prominent resonances in the earphone’s transfer function), and their levels grew more rapidly with increasing stimulus level than did cochlear DP amplitudes. As a result, earphone DP amplitudes often exceeded those of cochlear DPs. Using fMRI, we found that earphone DPs had a substantial effect on the response of pitch-sensitive cortical regions. In contrast, cochlear DPs had a small effect on cortical fMRI responses that did not reach statistical significance, consistent with their lower amplitudes. Based on these findings, we designed a set of pitch stimuli optimized for identifying pitch-responsive brain regions using fMRI. These stimuli robustly drive pitch-responsive brain regions while producing minimal cochlear and earphone distortion, and will hopefully aid fMRI researchers in avoiding distortion confounds. PMID:26827809

MR appearance of the temporal evolution and resolution of spontaneous osteonecrosis of the knee: a case report.

PubMed

Geijer, Mats; Jureus, Jan; Hanni, Mari; Shalabi, Adel

2017-02-01

Spontaneous osteonecrosis of the knee (SONK) is a feared condition of unknown cause, in its classic form appearing in the medial femoral condyle in middle-aged or elderly subjects. Diagnosis with radiography is notoriously difficult with a long latency before typical changes appear. Magnetic resonance imaging (MRI) is regarded as a diagnostic tool with the possibility to give an earlier diagnosis with improved chances for treatment. However, also with MRI there may be an initial diagnostic blind spot before typical changes appear. Little is known about the temporal evolution of the MRI changes. In the current case report, a case of SONK is reported where serial imaging with MRI was performed, from initial symptoms to eventual resolution after almost three years.

MR appearance of the temporal evolution and resolution of spontaneous osteonecrosis of the knee: a case report

PubMed Central

Jureus, Jan; Hanni, Mari; Shalabi, Adel

2017-01-01

Spontaneous osteonecrosis of the knee (SONK) is a feared condition of unknown cause, in its classic form appearing in the medial femoral condyle in middle-aged or elderly subjects. Diagnosis with radiography is notoriously difficult with a long latency before typical changes appear. Magnetic resonance imaging (MRI) is regarded as a diagnostic tool with the possibility to give an earlier diagnosis with improved chances for treatment. However, also with MRI there may be an initial diagnostic blind spot before typical changes appear. Little is known about the temporal evolution of the MRI changes. In the current case report, a case of SONK is reported where serial imaging with MRI was performed, from initial symptoms to eventual resolution after almost three years. PMID:28203389

Blood oxygenation level-dependent MRI for assessment of renal oxygenation

PubMed Central

Neugarten, Joel; Golestaneh, Ladan

2014-01-01

Blood oxygen level-dependent magnetic resonance imaging (BOLD MRI) has recently emerged as an important noninvasive technique to assess intrarenal oxygenation under physiologic and pathophysiologic conditions. Although this tool represents a major addition to our armamentarium of methodologies to investigate the role of hypoxia in the pathogenesis of acute kidney injury and progressive chronic kidney disease, numerous technical limitations confound interpretation of data derived from this approach. BOLD MRI has been utilized to assess intrarenal oxygenation in numerous experimental models of kidney disease and in human subjects with diabetic and nondiabetic chronic kidney disease, acute kidney injury, renal allograft rejection, contrast-associated nephropathy, and obstructive uropathy. However, confidence in conclusions based on data derived from BOLD MRI measurements will require continuing advances and technical refinements in the use of this technique. PMID:25473304

Clinical Applications of Resting State Functional Connectivity

PubMed Central

Fox, Michael D.; Greicius, Michael

2010-01-01

During resting conditions the brain remains functionally and metabolically active. One manifestation of this activity that has become an important research tool is spontaneous fluctuations in the blood oxygen level-dependent (BOLD) signal of functional magnetic resonance imaging (fMRI). The identification of correlation patterns in these spontaneous fluctuations has been termed resting state functional connectivity (fcMRI) and has the potential to greatly increase the translation of fMRI into clinical care. In this article we review the advantages of the resting state signal for clinical applications including detailed discussion of signal to noise considerations. We include guidelines for performing resting state research on clinical populations, outline the different areas for clinical application, and identify important barriers to be addressed to facilitate the translation of resting state fcMRI into the clinical realm. PMID:20592951

21 CFR 882.5235 - Aversive conditioning device.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Aversive conditioning device. 882.5235 Section 882.5235 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES NEUROLOGICAL DEVICES Neurological Therapeutic Devices § 882.5235 Aversive conditioning...