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1

Distinguishing Pseudomeningocele, Epidural Hematoma, and Postoperative Infection on Postoperative MRI.  

PubMed

STUDY DESIGN:: Retrospective case series. OBJECTIVE:: To identify specific MRI characteristics of epidural fluid collections associated with infection, hematoma, or cerebrospinal fluid. SUMMARY OF BACKGROUND DATA:: Interpretation of postoperative MRI can be challenging after lumbar fusion. The purpose of this study was to identify specific MRI characteristics of epidural fluid collections associated with infection, hematoma, or cerebrospinal fluid (CSF). METHODS:: The study population includes consecutive patients between 2006 and 2010 who had MRIs performed within two weeks after elective surgery for evaluation of possible CSF fluid collection, hematoma, or infection. Patients with known previous infection (discitis/osteomyelitis) or inadequate MRIs were excluded from the study. Medical records were reviewed to determine the diagnosis (infection, hematoma, or pseudomeningocele) underlying the fluid collection. MRIs were retrospectively evaluated by a musculoskeletal radiologist and orthopedic spine attending who were blinded to the pathological diagnosis for characteristics of the fluid collection. MRI characteristics include location of lesion: osseous involvement, disk location, anterior versus posterior versus antero-posterior, soft tissue involvement, iliopsoas involvement. Characteristics of the lesion include volume of lesion, loculation, satellite lesions, multiple loci, destructive characteristics, mass effect upon thecal sac. Enhancement was scored based upon the following variables: rim enhancement, smooth versus irregular, thin versus thick, heterogeneity, diffuse enhancement, nonenhancement, rim thickness. General fluid collection intensity and complexity on T1, T2, and T1 post-contrast images was scored as high, medium, low. Chi square test was used to compare the incidence of imaging characteristics between patient groups (infection, hematoma, and CSF). RESULTS:: Thirty three patients were identified who met inclusion criteria. There were 13 (39%) with infection, 9 (27%) with hematoma, and 11 (33%) with CSF collection. Factors that were associated with infection were osseous involvement (R 0.392, P=0.024) and destructive characteristics (R 0.461, P=0.007). Factors that were correlated with hematoma include mass effect (R 0.515, P=0.002) and high T1 signal intensity (R 0.411, P=0.019), absence of thecal sac communication (R -0.389, P=0.025), and absence of disk involvement (-0.346, P=0.048). Pseudomeningocele was associated with thecal sac communication (R 0.404, P=0.02), absence of mass effect (-0.48, P=0.005), low T1 signal (-0.364, P=0.04), and low T2 complexity (R-0.479, P-0.005). CONCLUSION:: Specific characteristics of the postoperative MRI can be used to distinguish infection from noninfectious fluid collections. The strongest predictors of infection were osseous involvement and destructive bony changes. Hematoma was associated with mass effect on the thecal sac, high T1 signal intensity, and absence of communication and absence of disk involvement. CSF collections were distinguished by absence of mass effect, low T2 signal complexity, low T1 signal intensity, and communication with the thecal sac. PMID:23563334

Radcliff, Kristen E; Morrison, William B; Kepler, Christopher; Moore, Jeffrey; Sidhu, Gursukhman; Gendelberg, David; Miller, Luciano; Sonagli, Marcos; Vaccaro, Alexander R

2013-04-01

2

Distinguishing Grammatical Constructions with fMRI Pattern Analysis  

ERIC Educational Resources Information Center

All linguistic and psycholinguistic theories aim to provide psychologically valid analyses of particular grammatical patterns and the relationships that hold among them. Until recently, no tools were available to distinguish neural correlates of particular grammatical constructions that shared the same content words, propositional meaning, and…

Allen, Kachina; Pereira, Francisco; Botvinick, Matthew; Goldberg, Adele E.

2012-01-01

3

Integrated speech enhancement for functional MRI environment.  

PubMed

This paper presents an integrated speech enhancement (SE) method for the noisy MRI environment. We show that the performance of SE system improves considerably when the speech signal dominated by MRI acoustic noise at very low SNR is enhanced in two successive stages using two-channel SE methods followed by a single-channel post processing SE algorithm. Actual MRI noisy speech data are used in our experiments showing the improved performance of the proposed SE method. PMID:19964964

Pathak, Nishank; Milani, Ali A; Panahi, Issa; Briggs, Richard

2009-01-01

4

Distinguishing breast cancer cells using surface-enhanced Raman scattering.  

PubMed

The detection and identification of epidermal growth factor receptor 2 (HER2)-positive breast cancer cells is crucial for the clinic therapy of breast cancer. For the aim of the detection, a novel surface-enhanced Raman scattering (SERS) probe for distinguishing breast cancers at different HER2 statuses is reported in this paper. In such a probe, anti-HER2 antibody-conjugated silver nanoparticles have been synthesized for specific targeting of HER2-positive breast cancer cells. More importantly, different from the previously reported SERS probe for targeting cancer cells, p-mercaptobenzoic acid is utilized as both the Raman reporter and the conjugation agent for attaching antibody molecules, which leads to a much simplified structure. For investigating the ability of such a probe to distinguish breast cancer cells, SKBR3 and MCF7 cells were chosen as two model systems, which are HER2-positive- and HER2-negative-expressing cells, respectively. The experimental results reveal that SKBR3 cells exhibit much stronger SERS signals than MCF7 cells, indicating that the probe could be utilized to distinguish breast cancer cells at different HER2 statuses. This kind of SERS probe holds a potential for a direct detection of living breast cancer cells with the advantages of easy fabrication, high SERS sensitivity, and biocompatibility. PMID:22124755

Yang, Jing; Wang, Zhuyuan; Zong, Shenfei; Song, Chunyuan; Zhang, Ruohu; Cui, Yiping

2011-11-29

5

Central nervous system infectious diseases mimicking multiple sclerosis: recognizing distinguishable features using MRI.  

PubMed

The current diagnostic criteria for multiple sclerosis (MS) confirm the relevant role of magnetic resonance imaging (MRI), supporting the possibility of characterizing the dissemination in space (DIS) and the dissemination in time (DIT) in a single scan. To maintain the specificity of these criteria, it is necessary to determine whether T2/FLAIR visible lesions and the gadolinium enhancement can be attributed to diseases that mimic MS. Several diseases are included in the MS differential diagnosis list, including diseases with exacerbation, remitting periods and numerous treatable infectious diseases, which can mimic the MRI features of MS. We discuss the most relevant imaging features in several infectious diseases that resemble MS and examine the primary spatial distributions of lesions and the gadolinium enhancement patterns related to MS. Recognizing imaging "red flags" can be useful for the proper diagnostic evaluation of suspected cases of MS, facilitating the correct differential diagnosis by assessing the combined clinical, laboratory and MR imaging information. PMID:24141516

Rocha, Antônio José da; Littig, Ingrid Aguiar; Nunes, Renato Hoffmann; Tilbery, Charles Peter

2013-09-01

6

MRI nerve root enhancement in Krabbe disease  

Microsoft Academic Search

Krabbe disease is characterized by abnormal breakdown and turnover of myelin, leading to extensive demyelination in both the peripheral and central nervous systems. A 7-month-old infant with early-onset Krabbe disease had deceptively normal head images, but spinal MRI demonstrated abnormal gadolinium enhancement of the lumbosacral sacral nerve roots and cauda equina such as that seen in Guillain-Barré syndrome. Abnormal enhancement

Elza Vasconcellos; Michelle Smith

1998-01-01

7

Enhancement of Ovarian Malignancy on Clinical Contrast Enhanced MRI Studies  

PubMed Central

Purpose. To assess if there is a significant difference in enhancement of high grade serous carcinoma of the ovary compared with other ovarian malignancies on clinically performed contrast enhanced MRI studies. Methods. In this institutional-review–board-approved study, two radiologists reviewed contrast enhanced MRI scans in 37 patients with ovarian cancer. Readers measured the signal intensity (SI) of ovarian mass and gluteal fat pre- and postcontrast administration. Percentage enhancement (PE) was calculated as [(post-pre)/precontrast SI] × 100. Results. Pathology revealed 19 patients with unilateral and 18 patients with bilateral malignancies for a total of 55 malignant ovaries-high grade serous carcinoma in 25/55 ovaries (45%), other epithelial carcinomas in 12 ovaries (22%), nonepithelial cancers in 8 ovaries (14%), and borderline tumors in 10 ovaries (18%). Enhancement of high grade serous carcinoma was not significantly different from other invasive ovarian malignancies (Reader 1 P = 0.865; Reader 2 P = 0.353). Enhancement of invasive ovarian malignancies was more than borderline tumors but did not reach statistical significance (Reader 1P = 0.102; Reader 2 P = 0.072). Conclusion. On clinically performed contrast enhanced MRI studies, enhancement of high grade serous ovarian carcinoma is not significantly different from other ovarian malignancies.

Pannu, Harpreet K.; Ma, Weining; Zabor, Emily Craig; Moskowitz, Chaya S.; Barakat, Richard R.; Hricak, Hedvig

2013-01-01

8

Distinguishing the Processing of Gestures from Signs in Deaf Individuals: An fMRI Study  

PubMed Central

Manual gestures occur on a continuum from co-speech gesticulations to conventionalized emblems to language signs. Our goal in the present study was to understand the neural bases of the processing of gestures along such a continuum. We studied four types of gestures, varying along linguistic and semantic dimensions: linguistic and meaningful American Sign Language (ASL), non-meaningful pseudo-ASL, meaningful emblematic, and nonlinguistic, non-meaningful made-up gestures. Pre-lingually deaf, native signers of ASL participated in the fMRI study and performed two tasks while viewing videos of the gestures: a visuo-spatial (identity) discrimination task and a category discrimination task. We found that the categorization task activated left ventral middle and inferior frontal gyrus, among other regions, to a greater extent compared to the visual discrimination task, supporting the idea of semantic-level processing of the gestures. The reverse contrast resulted in enhanced activity of bilateral intraparietal sulcus, supporting the idea of featural-level processing (analogous to phonological-level processing of speech sounds) of the gestures. Regardless of the task, we found that brain activation patterns for the nonlinguistic, non-meaningful gestures were the most different compared to the ASL gestures. The activation patterns for the emblems were most similar to those of the ASL gestures and those of the pseudo-ASL were most similar to the nonlinguistic, non-meaningful gestures. The fMRI results provide partial support for the conceptualization of different gestures as belonging to a continuum and the variance in the fMRI results was best explained by differences in the processing of gestures along the semantic dimension.

Husain, Fatima T.; Patkin, Debra J.; Thai-Van, Hung; Braun, Allen R.; Horwitz, Barry

2009-01-01

9

Can Asperger syndrome be distinguished from autism? An anatomic likelihood meta-analysis of MRI studies  

PubMed Central

Background The question of whether Asperger syndrome can be distinguished from autism has attracted much debate and may even incur delay in diagnosis and intervention. Accordingly, there has been a proposal for Asperger syndrome to be subsumed under autism in the forthcoming Diagnostic and Statistical Manual of Mental Disorders, fifth edition, in 2013. One approach to resolve this question has been to adopt the criterion of absence of clinically significant language or cognitive delay — essentially, the “absence of language delay.” To our knowledge, this is the first meta-analysis of magnetic resonance imaging (MRI) studies of people with autism to compare absence with presence of language delay. It capitalizes on the voxel-based morphometry (VBM) approach to systematically explore the whole brain for anatomic correlates of delay and no delay in language acquisition in people with autism spectrum disorders. Methods We conducted a systematic search for VBM MRI studies of grey matter volume in people with autism. Studies with a majority (at least 70%) of participants with autism diagnoses and a history of language delay were assigned to the autism group (n = 151, control n = 190). Those with a majority (at least 70%) of individuals with autism diagnoses and no language delay were assigned to the Asperger syndrome group (n = 149, control n = 214). We entered study coordinates into anatomic likelihood estimation meta-analysis software with sampling size weighting to compare grey matter summary maps driven by Asperger syndrome or autism. Results The summary autism grey matter map showed lower volumes in the cerebellum, right uncus, dorsal hippocampus and middle temporal gyrus compared with controls; grey matter volumes were greater in the bilateral caudate, prefrontal lobe and ventral temporal lobe. The summary Asperger syndrome map indicated lower grey matter volumes in the bilateral amygdala/hippocampal gyrus and prefrontal lobe, left occipital gyrus, right cerebellum, putamen and precuneus compared with controls; grey matter volumes were greater in more limited regions, including the bilateral inferior parietal lobule and the left fusiform gyrus. Both Asperger syndrome and autism studies reported volume increase in clusters in the ventral temporal lobe of the left hemisphere. Limitations We assigned studies to autism and Asperger syndrome groups for separate analyses of the data and did not carry out a direct statistical group comparison. In addition, studies available for analysis did not capture the entire spectrum, therefore we cannot be certain that our findings apply to a wider population than that sampled. Conclusion Whereas grey matter differences in people with Asperger syndrome compared with controls are sparser than those reported in studies of people with autism, the distribution and direction of differences in each category are distinctive.

Yu, Kevin K.; Cheung, Charlton; Chua, Siew E.; McAlonan, Grainne M.

2011-01-01

10

T2* and FSE MRI distinguishes four subtypes of neurodegeneration with brain iron accumulation  

PubMed Central

Background: Neurodegeneration with brain iron accumulation (NBIA) defines a group of genetic disorders characterized by brain iron deposition and associated with neuronal death. The known causes of NBIA include pantothenate kinase-associated neurodegeneration (PKAN), neuroferritinopathy, infantile neuroaxonal dystrophy (INAD), and aceruloplasminemia. Objective: To define the radiologic features of each NBIA subtype. Methods: Brain MRIs from patients with molecularly confirmed PKAN (26 cases), neuroferritinopathy (21 cases), INAD (four cases), and aceruloplasminemia (10 cases) were analyzed blindly to delineate patterns of iron deposition and neurodegeneration. Results: In most cases of PKAN, abnormalities were restricted to globus pallidus and substantia nigra, with 100% having an eye of the tiger sign. In a minority of PKAN cases there was hypointensity of the dentate nuclei (1/5 on T2* sequences, 2/26 on fast spin echo [FSE]). In INAD, globus pallidus and substantia nigra were involved on T2* and FSE scans, with dentate involvement only seen on T2*. By contrast, neuroferritinopathy had consistent involvement of the dentate nuclei, globus pallidus, and putamen, with confluent areas of hyperintensity due to probable cavitation, involving the pallida and putamen in 52%, and a subset having lesions in caudate nuclei and thalami. More uniform involvement of all basal ganglia and the thalami was typical in aceruloplasminemia, but without cavitation. Conclusions: In the majority of cases, different subtypes of neurodegeneration associated with brain iron accumulation can be reliably distinguished with T2* and T2 fast spin echo brain MRI, leading to accurate clinical and subsequent molecular diagnosis. GLOSSARY FSE = fast spin echo; INAD = infantile neuroaxonal dystrophy; NBIA = neurodegeneration associated with brain iron accumulation; PKAN = pantothenate kinase associated neurodegeneration; ROI = region of interest.

McNeill, A; Birchall, D; Hayflick, S J.; Gregory, A; Schenk, J F.; Zimmerman, E A.; Shang, H; Miyajima, H; Chinnery, P F.

2008-01-01

11

Enhanced MRI and MRI-Guided Interventional Procedures in Women with Asymptomatic Silicone-Injected Breasts  

PubMed Central

Asymptomatic women who have received silicone injection for breast augmentation have a risk of underestimating breast cancer by palpation, mammography, or breast sonography. Enhanced breast MRI is sensitive to display certain nonspecific enhanced lesions or suspicious lesions. Such nonspecific MRI-detected lesions could be managed by American College Radiology BI-RADS lexicon and selectively with MRI-guided techniques biopsy to prevent unnecessary surgery.

Cheung, Yun-Chung; Chen, Shin-Chih; Lo, Yung-Feng

2012-01-01

12

Resting-state BOLD networks versus task-associated functional MRI for distinguishing Alzheimer's disease risk groups.  

PubMed

To assess the ability of resting-state functional magnetic resonance imaging to distinguish known risk factors for AD, we evaluated 17 cognitively normal individuals with a family history of AD and at least one copy of the apolipoprotein e4 allele compared to 12 individuals who were not carriers of the APOE4 gene and did not have a family history of AD. Blood oxygen level dependent fMRI was performed evaluating encoding-associated signal and resting-state default mode network signal differences between the two risk groups. Neurocognitive testing revealed that the high risk group performed worse on category fluency testing, but the groups were equivalent on all other cognitive measures. During encoding of novel face-name pairs, there were no regions of encoding-associated BOLD activations that were different in the high risk group. Encoding-associated deactivations were greater in magnitude in the low risk group in the medial and right lateral parietal cortex, similar to findings in AD studies. The resting-state DMN analysis demonstrated nine regions in the prefrontal, orbital frontal, temporal and parietal lobes that distinguished the two risk groups. Resting-state DMN analysis could distinguish risk groups with an effect size of 3.35, compared to an effect size of 1.39 using encoding-associated fMRI techniques. Imaging of the resting state avoids performance related variability seen in activation fMRI, is less complicated to acquire and standardize, does not require radio-isotopes, and may be more effective at identifying functional pathology associated with AD risk compared to non-resting fMRI techniques. PMID:19539034

Fleisher, Adam S; Sherzai, Ayesha; Taylor, Curtis; Langbaum, Jessica B S; Chen, Kewei; Buxton, Richard B

2009-06-16

13

Resting-state BOLD networks versus task-associated functional MRI for distinguishing Alzheimer's disease risk groups  

PubMed Central

To assess the ability of resting state functional magnetic resonance imaging to distinguish known risk factors for AD, we evaluated 17 cognitively normal individuals with a family history of AD and at least one copy of the apolipoprotein e4 allele compared to 12 individuals who were not carriers of the APOE4 gene and did not have a family history of AD. Blood oxygen level dependent fMRI was performed evaluating encoding-associated signal and resting state default mode network signal differences between the two risk groups. Neurocognitive testing revealed that the high risk group performed worse on category fluency testing, but the groups were equivalent on all other cognitive measures. During encoding of novel face-name pairs, there were no regions of encoding-associated BOLD activations that were different in the high risk group. Encoding-associated deactivations were greater in magnitude in the low risk group in the medial and right lateral parietal cortex, similar to findings in AD studies. The resting state DMN analysis demonstrated nine regions in the prefrontal, orbital frontal, temporal and parietal lobes that distinguished the two risk groups. Resting state DMN analysis could distinguish risk groups with an effect size of 3.35, compared to an effect size of 1.39 using encoding-associated fMRI techniques. Imaging of the resting state avoids performance related variability seen in activation fMRI, is less complicated to acquire and standardize, does not require radio-isotopes, and may be more effective at identifying functional pathology associated with AD risk compared to non-resting fMRI techniques.

Fleisher, Adam S.; Sherzai, Ayesha; Taylor, Curtis; Langbaum, Jessica B.S.; Chen, Kewei; Buxton, Richard B.

2009-01-01

14

Role of diffusion-weighted echo-planar MRI in distinguishing between brain abscess and tumour: a preliminary report  

Microsoft Academic Search

Our purpose was to evaluate diffusion-weighted (DW) echo-planar MRI in differentiating between brain abscess and tumour.\\u000a We examined two patients with surgically confirmed pyogenic brain abscess and 18 with metastatic brain tumours or high-grade\\u000a glioma, using a 1.5 T system. The apparent diffusion coefficient (ADC) of each necrotic or solid contrast-enhancing lesion\\u000a was measured with two different b values (20

K. Noguchi; N. Watanabe; T. Nagayoshi; T. Kanazawa; S. Toyoshima; M. Shimizu; H. Seto

1999-01-01

15

Ultrashort Echo Time for Improved Positive-Contrast Manganese-Enhanced MRI of Cancer  

PubMed Central

Objective Manganese (Mn) is a positive magnetic resonance imaging (MRI) contrast agent that has been used to obtain physiological, biochemical, and molecular biological information. There is great interest to broaden its applications, but a major challenge is to increase detection sensitivity. Another challenge is distinguishing regions of Mn-related signal enhancement from background tissue with inherently similar contrast. To overcome these limitations, this study investigates the use of ultrashort echo time (UTE) and subtraction UTE (SubUTE) imaging for more sensitive and specific determination of Mn accumulation. Materials and Methods Simulations were performed to investigate the feasibility of UTE and SubUTE for Mn-enhanced MRI and to optimize imaging parameters. Phantoms containing aqueous Mn solutions were imaged on a MRI scanner to validate simulations predictions. Breast cancer cells that are very aggressive (MDA-MB-231 and a more aggressive variant LM2) and a less aggressive cell line (MCF7) were labeled with Mn and imaged on MRI. All imaging was performed on a 3 Tesla scanner and compared UTE and SubUTE against conventional T1-weighted spoiled gradient echo (SPGR) imaging. Results Simulations and phantom imaging demonstrated that UTE and SubUTE provided sustained and linearly increasing positive contrast over a wide range of Mn concentrations, whereas conventional SPGR displayed signal plateau and eventual decrease. Higher flip angles are optimal for imaging higher Mn concentrations. Breast cancer cell imaging demonstrated that UTE and SubUTE provided high sensitivity, with SubUTE providing background suppression for improved specificity and eliminating the need for a pre-contrast baseline image. The SubUTE sequence allowed the best distinction of aggressive breast cancer cells. Conclusions UTE and SubUTE allow more sensitive and specific positive-contrast detection of Mn enhancement. This imaging capability can potentially open many new doors for Mn-enhanced MRI in vascular, cellular, and molecular imaging.

Nofiele, Joris Tchouala; Cheng, Hai-Ling Margaret

2013-01-01

16

Surface plasmon-enhanced terahertz spectroscopic distinguishing between isomers in powder form.  

PubMed

The effect of a dielectric overlayer on terahertz transmission through a freestanding metallic array of subwavelength holes is experimentally presented. There is a remarkable resonance redshift from 0.600 to 0.498 THz at the surface plasmon (SP) metal-dielectric resonance mode with increasing film thickness. When the overlayer film is thicker than a critical thickness, the resonance frequency becomes steady at the final resonance frequency ?(f). On the basis of the dispersion relation of SPs, two kinds of glutamic acid enantiomers are distinguished by use of SP-enhanced terahertz spectra of metallic array of subwavelength holes according to the result of ?(f). The terahertz plasmonic hole array with the sensitive nature provides an approach to distinguish trace amount of powder substances, which has a promising application prospect in the fields of public security and biomedical science, such as distinguishing between isomers and identifying expensive medicines and drugs. PMID:23385924

He, Mingxia; Li, Jingyan; Liu, Guanlin; Han, Jiaguang; Tian, Zhen; Gu, Jianqiang; Chen, Tao; Qin, Rui

2013-02-01

17

Dynamic contrast-enhanced-MRI of tumor hypoxia.  

PubMed

Patients with highly hypoxic primary tumors show increased frequency of locoregional treatment failure and poor survival rates and may benefit from particularly aggressive treatment. The potential of gadolinium diethylene-triamine penta-acetic acid-based dynamic contrast-enhanced-MRI in assessing tumor hypoxia was investigated in this preclinical study. Xenografted tumors of eight human melanoma lines were subjected to dynamic contrast-enhanced-MRI and measurement of the fraction of radiobiologically hypoxic cells and the fraction of pimonidazole-positive hypoxic cells. Tumor images of K(trans) (the volume transfer constant of gadolinium diethylene-triamine penta-acetic acid) and v(e) (the fractional distribution volume of gadolinium diethylene-triamine penta-acetic acid) were produced by pharmacokinetic analysis of the dynamic contrast-enhanced-MRI data, and K(trans) and v(e) frequency distributions of the non-necrotic tumor tissue were established and related to the extent of hypoxia. Tumors showing high K(trans) values and high v(e) values had low fractions of hypoxic cells, whereas tumors showing both low K(trans) values and low v(e) values had high hypoxic fractions. K(trans) differentiated better between tumors with low and high hypoxic fractions than did v(e). This study supports the current attempts to establish dynamic contrast-enhanced-MRI as a method for assessing the extent of hypoxia in human tumors, and it provides guidelines for the clinical development of valid assays. PMID:21661044

Egeland, Tormod A M; Gulliksrud, Kristine; Gaustad, Jon-Vidar; Mathiesen, Berit; Rofstad, Einar K

2011-06-09

18

MRI gadolinium enhancement precedes neuroradiological findings in acute necrotizing encephalopathy.  

PubMed

We report a 2-year-old Japanese boy with acute necrotizing encephalopathy (ANE) triggered by human herpes virus-6, who presented insightful magnetic resonance imaging (MRI) findings. He was admitted due to impaired consciousness and a convulsion, 2days after the onset of an upper respiratory infection. At admission, cranial MRI showed marked gadolinium enhancement at the bilateral thalami, brainstem and periventricular white matter without abnormal findings in noncontrast MRI sequences. On the following day, noncontrast computed tomography demonstrated homogeneous low-density lesions in the bilateral thalami and severe diffuse brain edema. The patient progressively deteriorated and died on the 18th day of admission. The pathogenesis of ANE remains mostly unknown, but it has been suggested that hypercytokinemia may play a major role. Overproduced cytokines cause vascular endothelial damage and alter the permeability of the vessel wall in the multiple organs, including the brain. The MRI findings in our case demonstrate that blood-brain barrier permeability was altered prior to the appearance of typical neuroradiological findings. This suggests that alteration of blood-brain barrier permeability is the first step in the development of the brain lesions in ANE, and supports the proposed mechanism whereby hypercytokinemia causes necrotic brain lesions. This is the first report demonstrating MRI gadolinium enhancement antecedent to typical neuroradiological findings in ANE. PMID:23265619

Yoshida, Takeshi; Tamura, Takuya; Nagai, Yuhki; Ueda, Hiroyuki; Awaya, Tomonari; Shibata, Minoru; Kato, Takeo; Heike, Toshio

2012-12-20

19

Dynamic contrast-enhanced imaging techniques: CT and MRI  

PubMed Central

Over the last few decades there has been considerable research into quantifying the cerebral microvasculature with imaging, for use in studies of the human brain and various pathologies including cerebral tumours. This review highlights key issues in dynamic contrast-enhanced CT, dynamic contrast-enhanced MRI and arterial spin labelling, the various applications of which are considered elsewhere in this special issue of the British Journal of Radiology.

O'Connor, J P B; Tofts, P S; Miles, K A; Parkes, L M; Thompson, G; Jackson, A

2011-01-01

20

[MRI with dynamic contrast enhancement in brain tumors].  

PubMed

Magnetic resonance imaging (MRI) is the leading method of radiation diagnosis of brain tumors. In conditions of the artificial contrast enhancement there are more clearly differentiated the boundaries of the tumor node on the back of peritumorous edema and identified structural features of the tumor. The purpose of this study was to examine indicators of the dynamics of accumulation and removal of contrast agents by brain tumors in MRI technique with dynamic contrast and identify opportunities of this method in the differential diagnosis of various types of tumors. PMID:23814831

Panfilenko, A F; Iakovlev, S A; Pozdniakov, A V; Tiumin, L A; Shcherbuk, A Iu

2013-01-01

21

Epigenetic signatures distinguish multiple classes of enhancers with distinct cellular functions  

PubMed Central

Epigenetic regulation of gene enhancer elements is important for establishing and maintaining the identity of cells. Gene enhancer elements are thought to exist in either active or poised states distinguishable by chromatin features, but a complete understanding of the regulation of enhancers is lacking. Here, by using mouse embryonic stem cells and their differentiated derivatives, as well as terminally differentiated cells, we report the coexistence of multiple, defined classes of enhancers that serve distinct cellular functions. Specifically, we found that active enhancers can be subclassified based on varying levels of H3K4me1, H3K27ac, and H3K36me3 and the pSer2/5 forms of RNA polymerase II. The abundance of these histone modifications positively correlates with the expression of associated genes and cellular functions consistent with the identity of the cell type. Poised enhancers can also be subclassified based on presence or absence of H3K27me3 and H3K9me3, conservation, genomic location, expression levels of associated genes, and predicted function of associated genes. These findings not only refine the repertoire of histone modifications at both active and poised gene enhancer elements but also raise the possibility that enhancers associated with distinct cellular functions are partitioned based on specific combinations of histone modifications.

Zentner, Gabriel E.; Tesar, Paul J.; Scacheri, Peter C.

2011-01-01

22

Classic models for dynamic contrast-enhanced MRI.  

PubMed

Dynamic contrast-enhanced MRI (DCE-MRI) is a functional MRI method where T1 -weighted MR images are acquired dynamically after bolus injection of a contrast agent. The data can be interpreted in terms of physiological tissue characteristics by applying the principles of tracer-kinetic modelling. In the brain, DCE-MRI enables measurement of cerebral blood flow (CBF), cerebral blood volume (CBV), blood-brain barrier (BBB) permeability-surface area product (PS) and the volume of the interstitium (ve ). These parameters can be combined to form others such as the volume-transfer constant K(trans) , the extraction fraction E and the contrast-agent mean transit times through the intra- and extravascular spaces. A first generation of tracer-kinetic models for DCE-MRI was developed in the early 1990s and has become a standard in many applications. Subsequent improvements in DCE-MRI data quality have driven the development of a second generation of more complex models. They are increasingly used, but it is not always clear how they relate to the models of the first generation or to the model-free deconvolution methods for tissues with intact BBB. This lack of understanding is leading to increasing confusion on when to use which model and how to interpret the parameters. The purpose of this review is to clarify the relation between models of the first and second generations and between model-based and model-free methods. All quantities are defined using a generic terminology to ensure the widest possible scope and to reveal the link between applications in the brain and in other organs. PMID:23674304

Sourbron, Steven P; Buckley, David L

2013-05-15

23

Sturge-Weber syndrome with no leptomeningeal enhancement on MRI  

Microsoft Academic Search

Sturge-Weber syndrome (SWS) is a neurocutaneous syndrome characterized by a facial nevus flammeus associated with seizures,\\u000a developmental delay, and, often, with hemiparesis and hemianopia. On MRI, the most characteristic finding has been reported\\u000a to be leptomeningeal enhancement, believed to represent leakage of contrast medium through the anomalous pial vessels that\\u000a characterize the disease. We present a case of SWS with

N. J. Fischbein; A. J. Barkovich; Y. Wu; B. O. Berg

1998-01-01

24

MRI arterial enhancement fraction in hepatic fibrosis and cirrhosis.  

PubMed

OBJECTIVE. Fibrosis leads to altered liver hemodynamics. The arterial enhancement fraction, which is defined as the ratio of hepatic arterial perfusion to the total hepatic perfusion, can provide noninvasive assessment of hepatic perfusion. The aim of this study was to show that the arterial enhancement fraction values correlate with histopathologic stage of liver fibrosis, thus providing a reliable noninvasive radiologic alternative to liver biopsy for the detection and staging of hepatic fibrosis. MATERIALS AND METHODS. We evaluated hepatic fibrosis stage (denoted by Metavir score [F]) and arterial enhancement fraction of patients who underwent standard triphasic liver MRI and liver biopsy within 1 year from January 2005 to December 2010. Prototype software was used to calculate the arterial enhancement fraction. Statistical analysis included nonparametric tests and area under the receiver operating characteristic curve (AUC). RESULTS. One hundred fourteen patients (69 men and 45 women; median age, 52.5 years) were divided into groups according to the Metavir score. The mean arterial enhancement fraction was 24.2% ± 11.6% for F0, 35.2% ± 18.7% for F1, 30.2% ± 12.5% for F2, 37.5% ± 16.4% for F3, and 59.8% ± 16.6% for F4. The mean arterial enhancement fraction values differed significantly between Metavir scores (p < 0.001) and showed a positive correlation with Metavir score (r = 0.693; p < 0.001). The optimal mean arterial enhancement fraction cutoffs were 32.96% or more (AUC = 0.8343) for detection of mild fibrosis, 33.33% or more (AUC = 0.8524) for detection of moderate fibrosis, 38.43% or more (AUC = 0.8819) for detection of severe fibrosis, and 45.76% or more (AUC = 0.9161) for detection of cirrhosis. CONCLUSION. Arterial enhancement fraction using triple-phase MRI can provide a reliable noninvasive method to assess hepatic fibrosis. PMID:24059398

Ou, Hsin-You; Bonekamp, Susanne; Bonekamp, David; Corona-Villalobos, Celia Pamela; Torbenson, Michael S; Geiger, Bernhard; Kamel, Ihab R

2013-10-01

25

Manganese-Enhanced MRI: An Exceptional Tool in Translational Neuroimaging  

PubMed Central

The metal manganese is a potent magnetic resonance imaging (MRI) contrast agent that is essential in cell biology. Manganese-enhanced magnetic resonance imaging (MEMRI) is providing unique information in an ever-growing number of applications aimed at understanding the anatomy, the integration, and the function of neural circuits both in normal brain physiology as well as in translational models of brain disease. A major drawback to the use of manganese as a contrast agent, however, is its cellular toxicity. Therefore, paramount to the successful application of MEMRI is the ability to deliver Mn2+ to the site of interest using as low a dose as possible while preserving detectability by MRI. In the present work, the different approaches to MEMRI in translational neuroimaging are reviewed and challenges for future identified from a practical standpoint.

Silva, Afonso C.; Bock, Nicholas A.

2008-01-01

26

Tumor Microenvironment Identification In Vivo using Dynamic Contrast Enhanced MRI  

Cancer.gov

The microenvironment in solid tumors is characterized by inadequate and heterogeneous perfusion, hyper-permeable vasculature, hypoxia, acidic extracellular pH, and nutrient deprivation. Hypoxic tumors, often associated with a more aggressive tumor phenotype, are more resistant to chemo- or radiation therapy than well-vascularized, well-oxygenated tumors. We present an approach to identify areas of tumor hypoxia using the signal-versus-time curves of Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI) data as a surrogate marker of hypoxia.

27

Hepatocellular carcinoma: perfusion quantification with dynamic contrast-enhanced MRI.  

PubMed

OBJECTIVE. The objective of our study was to report our initial experience with dynamic contrast-enhanced MRI (DCE-MRI) for perfusion quantification of hepatocellular carcinoma (HCC) and surrounding liver. SUBJECTS AND METHODS. DCE-MRI of the liver was prospectively performed on 31 patients with HCC (male-female ratio, 26:5; mean age, 61 years; age range, 41-83 years). A dynamic coronal 3D FLASH sequence was performed at 1.5 T before and after injection of gadolinium-based contrast agent with an average temporal resolution of 3.8 seconds. Regions of interest were drawn on the abdominal aorta, portal vein, liver parenchyma, and HCC lesions by two observers in consensus. Time-activity curves were analyzed using a dual-input single-compartment model. The following perfusion parameters were obtained: arterial flow, portal venous flow, arterial fraction, distribution volume, and mean transit time (MTT). RESULTS. Thirty-three HCCs (mean size, 3.9 cm; range, 1.1-12.6 cm) were evaluated in 26 patients. When compared with liver parenchyma, HCC showed significantly higher arterial hepatic blood flow and arterial fraction (p < 0.0001) and significantly lower distribution volume and portal venous hepatic blood flow (p < 0.0001-0.023), with no difference in MTT. Untreated HCCs (n = 16) had a higher arterial fraction and lower portal venous hepatic blood flow value than chemoembolized HCCs (n = 17, p < 0.04). CONCLUSION. DCE-MRI can be used to quantify perfusion metrics of HCC and liver parenchyma and to assess perfusion changes after HCC chemoembolization. PMID:24059368

Taouli, Bachir; Johnson, R Scott; Hajdu, Cristina H; Oei, Marcel T H; Merad, Miriam; Yee, Herman; Rusinek, Henry

2013-10-01

28

A simulation tool for dynamic contrast enhanced MRI.  

PubMed

The quantification of bolus-tracking MRI techniques remains challenging. The acquisition usually relies on one contrast and the analysis on a simplified model of the various phenomena that arise within a voxel, leading to inaccurate perfusion estimates. To evaluate how simplifications in the interstitial model impact perfusion estimates, we propose a numerical tool to simulate the MR signal provided by a dynamic contrast enhanced (DCE) MRI experiment. Our model encompasses the intrinsic R1 and R2 relaxations, the magnetic field perturbations induced by susceptibility interfaces (vessels and cells), the diffusion of the water protons, the blood flow, the permeability of the vessel wall to the the contrast agent (CA) and the constrained diffusion of the CA within the voxel. The blood compartment is modeled as a uniform compartment. The different blocks of the simulation are validated and compared to classical models. The impact of the CA diffusivity on the permeability and blood volume estimates is evaluated. Simulations demonstrate that the CA diffusivity slightly impacts the permeability estimates (< 5% for classical blood flow and CA diffusion). The effect of long echo times is investigated. Simulations show that DCE-MRI performed with an echo time TE = 5 ms may already lead to significant underestimation of the blood volume (up to 30% lower for brain tumor permeability values). The potential and the versatility of the proposed implementation are evaluated by running the simulation with realistic vascular geometry obtained from two photons microscopy and with impermeable cells in the extravascular environment. In conclusion, the proposed simulation tool describes DCE-MRI experiments and may be used to evaluate and optimize acquisition and processing strategies. PMID:23516414

Pannetier, Nicolas Adrien; Debacker, Clément Stéphan; Mauconduit, Franck; Christen, Thomas; Barbier, Emmanuel Luc

2013-03-14

29

A Simulation Tool for Dynamic Contrast Enhanced MRI  

PubMed Central

The quantification of bolus-tracking MRI techniques remains challenging. The acquisition usually relies on one contrast and the analysis on a simplified model of the various phenomena that arise within a voxel, leading to inaccurate perfusion estimates. To evaluate how simplifications in the interstitial model impact perfusion estimates, we propose a numerical tool to simulate the MR signal provided by a dynamic contrast enhanced (DCE) MRI experiment. Our model encompasses the intrinsic and relaxations, the magnetic field perturbations induced by susceptibility interfaces (vessels and cells), the diffusion of the water protons, the blood flow, the permeability of the vessel wall to the the contrast agent (CA) and the constrained diffusion of the CA within the voxel. The blood compartment is modeled as a uniform compartment. The different blocks of the simulation are validated and compared to classical models. The impact of the CA diffusivity on the permeability and blood volume estimates is evaluated. Simulations demonstrate that the CA diffusivity slightly impacts the permeability estimates ( for classical blood flow and CA diffusion). The effect of long echo times is investigated. Simulations show that DCE-MRI performed with an echo time may already lead to significant underestimation of the blood volume (up to 30% lower for brain tumor permeability values). The potential and the versatility of the proposed implementation are evaluated by running the simulation with realistic vascular geometry obtained from two photons microscopy and with impermeable cells in the extravascular environment. In conclusion, the proposed simulation tool describes DCE-MRI experiments and may be used to evaluate and optimize acquisition and processing strategies.

Mauconduit, Franck; Christen, Thomas; Barbier, Emmanuel Luc

2013-01-01

30

Assessing heterogeneity of lesion enhancement kinetics in dynamic contrast-enhanced MRI for breast cancer diagnosis  

PubMed Central

The current study investigates the feasibility of using texture analysis to quantify the heterogeneity of lesion enhancement kinetics in order to discriminate malignant from benign breast lesions. A total of 82 biopsy-proven breast lesions (51 malignant, 31 benign), originating from 74 women subjected to dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) were analysed. Pixel-wise analysis of DCE-MRI lesion data was performed to generate initial enhancement, post-initial enhancement and signal enhancement ratio (SER) parametric maps; these maps were subsequently subjected to co-occurrence matrix texture analysis. The discriminating ability of texture features extracted from each parametric map was investigated using a least-squares minimum distance classifier and further compared with the discriminating ability of the same texture features extracted from the first post-contrast frame. Selected texture features extracted from the SER map achieved an area under receiver operating characteristic curve of 0.922 ± 0.029, a performance similar to post-initial enhancement map features (0.906 ± 0.032) and statistically significantly higher than for initial enhancement map (0.767 ± 0.053) and first post-contrast frame (0.756 ± 0.060) features. Quantifying the heterogeneity of parametric maps that reflect lesion washout properties could contribute to the computer-aided diagnosis of breast lesions in DCE-MRI.

Karahaliou, A; Vassiou, K; Arikidis, N S; Skiadopoulos, S; Kanavou, T; Costaridou, L

2010-01-01

31

Quantitative dynamic contrast-enhanced MRI for the assessment of mandibular invasion by squamous cell carcinoma  

Microsoft Academic Search

The objective of this study was to determine the value of dynamic contrast-enhanced MRI (DCE-MRI) for the preoperative assessment of mandibular invasion in squamous cell carcinomas (SCC), adjacent or fixed to the mandible. DCE-MRI was performed with gadolinium diethylene triamine pentaacetic acid (Gd-DTPA). Data were obtained from 25 patients. From pharmacokinetic analysis of the tissue uptake of Gd-DTPA, the DCE-MRI

Ellen M. Van Cann; Mark Rijpkema; Arend Heerschap; Andries van der Bilt; Ron Koole; Paul J. W. Stoelinga

2008-01-01

32

Delayed contrast-enhanced MRI: use in myocardial viability assessment and other cardiac pathology.  

PubMed

As in other organs, tissue characterization is important for many cardiac diseases. For example, in ischemic heart disease, differentiation between reversibly and irreversibly damaged myocardium in patients with a prior myocardial infarction is crucial in determining disease severity, functional recovery and patient outcome. With the recent advent of the single inversion-recovery contrast-enhanced magnetic resonance imaging (MRI) sequence (delayed contrast-enhanced MRI), contrast between normal and abnormal tissues could be significantly enhanced compared with the conventional cardiac MRI sequences, enabling even subtle abnormalities to be visualized. Together with other advances in cardiac MRI (e.g. functional imaging, coronary artery imaging), MRI has become one of the preferred non-invasive modalities to study cardiac diseases. In this paper an overview of the versatility of delayed contrast-enhanced MRI for investigating cardiac diseases is given. PMID:15801058

Bogaert, Jan; Dymarkowski, Steven

2005-02-01

33

Mammographic density, MRI background parenchymal enhancement and breast cancer risk.  

PubMed

Mammographic density (MD), representing connective and epithelial tissue (fibroglandular tissue, FGT) is a major risk factor for breast cancer. In an analysis of an autopsy series (Bartow SA, Pathak DR, Mettler FA. Radiographic microcalcification and parenchymal patterns as indicators of histologic "high-risk" benign breast disease. Cancer 1990; 66: 1721-1725, Bartow SA, Pathak DR, Mettler FA et al. Breast mammographic pattern: a concatenation of confounding and breast cancer risk factors. Am J Epidemiol 1995; 142: 813-819), MD was found to be strongly correlated with the collagen and epithelial content of the breast (Li T, Sun L, Miller N et al. The association of measured breast tissue characteristics with MD and other risk factors for breast cancer. Cancer Epidemiol Biomarkers Prev 2005; 14: 343-349), and another report showed that breast epithelium was highly concentrated in the areas of collagen concentration (Hawes D, Downey S, Pearce CL et al. Dense breast stromal tissue shows greatly increased concentration of breast epithelium but no increase in its proliferative activity. Breast Cancer Res 2006; 8: R24). Collagen comprises the overwhelming majority of the FGT, occupying an area on the slides obtained from the autopsy series some 15 times the area of glandular tissue. The relationship of MD with breast cancer risk appears likely to be due to a major extent to increasing epithelial cell numbers with increasing MD. FGT is also seen in breast magnetic resonance imaging (breast MRI) and, as expected, it has been shown that this measure of FGT (MRI-FGT) is highly correlated with MD. A contrast-enhanced breast MRI shows that normal FGT 'enhances' (background parenchymal enhancement, BPE) after contrast agent is administered(Morris EA. Diagnostic breast MR imaging: current status and future directions. Radiol Clin North Am 2007; 45: 863-880, vii., Kuhl C. The current status of breast MR imaging. Part I. Choice of technique, image interpretation, diagnostic accuracy, and transfer to clinical practice. Radiology 2007; 244: 356-378), and a recent study suggests that BPE is also a major breast cancer risk factor, possibly as important as, and independent of MD (King V, Brooks JD, Bernstein JL et al. BPE at breast MR imaging and breast cancer risk. Radiology 2011; 260: 50-60). BPE is much more sensitive to the effects of menopause and tamoxifen than is FGT (King V, Gu Y, Kaplan JB et al. Impact of menopausal status on BPE and fibroglandular tissue on breast MRI. Eur Radiol 2012; 22: 2641-2647, King V, Kaplan J, Pike MC et al. Impact of tamoxifen on amount of fibroglandular tissue, BPE, and cysts on breast MRI. Breast J 2012; 18: 527-534). Changes in MD and BPE may be most useful in predicting response to chemopreventive agents aimed at blocking breast cell proliferation. More study of the biological basis of the effects of MD and BPE is needed if we are to fully exploit these factors in developing chemopreventive approaches to breast cancer. PMID:24131968

Pike, M C; Pearce, C L

2013-11-01

34

Synthesis and characterization of magnetoliposomes for MRI contrast enhancement.  

PubMed

This work assesses the characteristics of magnetoliposomes of soybean phosphatidylcholine (SPC):cholesterol (Chol) loaded with superparamagnetic iron oxide nanoparticles (IONPs) stabilized with tetramethylammonium hydroxide (TMAOH) and their capacity to enhance magnetic resonance imaging (MRI) contrast. Magnetoliposomes of SPC were used for comparative studies. IONPs and magnetoliposomes were characterized using transmission electron microscopy, dynamic light scattering, SQUID magnetometry, FTIR and MRI. The saturation magnetization at 10K was ~0.06 Am(2)/kg for SPC:Chol magnetoliposomes with 7 g iron oxide/mol of lipid and ~0.05 Am(2)/kg for SPC magnetoliposomes with 21 g iron oxide/mol of lipid. As these values are associated with the number of incorporated magnetic IONPs, the saturation magnetization is 1.2 times higher for magnetoliposomes of SPC:Chol as compared with magnetoliposomes of SPC alone. The behavior of temperature dependence in both cases is typical of superparamagnetic particles. FTIR spectra evidence the increase of magnetoliposome membrane ordering with the presence of Chol. Principal component analysis (PCA) applied to FTIR spectra evidenced a clear distinction between scores for SPC:Chol, and SPC magnetoliposomes and for SPC empty liposomes. PCA applied to FTIR data differentiate magnetoliposomes from empty liposomes. MR images of aqueous phantoms obtained with and without magnetoliposomes, clearly evidence their effect on T2 image weighting. PMID:23422275

Faria, M R; Cruz, M M; Gonçalves, M C; Carvalho, A; Feio, G; Martins, M B F

2013-02-16

35

Use of iron colloid-enhanced MRI for study of acute radiation-induced hepatic injury  

SciTech Connect

We present a case with acute radiation-induced hepatic injury using chondroitin sulfate iron colloid (CSIC)-enhanced MRI. Uptake of CSIC was decreased in the irradiated portion of the liver. CSIC-enhanced MRI is useful for obtaining information on the function of the reticuloendothelial system and demarcates between irradiated and nonirradiated zones. 18 refs., 3 figs

Suto, Yuji; Ametani, Masaki; Kato, Takashi; Hashimoto, Masayuki; Kamba, Masayuki; Sugihara, Syuji; Ohta, Yoshio [Tottori Univ. School of Medicine, Yonago (Japan)

1996-03-01

36

Contrast-enhanced MRI in acute optic neuritis: relationship to visual performance  

Microsoft Academic Search

Summary The location and extent of an abnormal signal on MRI of the optic nerve affected by optic neuritis are said to correlate with the severity of initial visual loss and recovery. We used gadolinium-enhanced fat-suppressed MRI to show abnormal enhancement of the optic nerve to determine the sensitivity of this modality in acute optic neuritis and whether the abnormal

Mark J. Kupersmith; Therese Alban; Barbara Zeiffer; Daniel Lefton

2002-01-01

37

New method for contrast manipulation in DNP-enhanced MRI.  

PubMed

The magnetization subtraction technique (MS), which is equivalent to the inversion recovery technique in strong magnetic fields, has been implemented in dynamic nuclear polarization-enhanced magnetic resonance imaging (DNPI). The general theoretical basis of the MS method, which can be applied to DNPI or to prepolarized MRI in weak magnetic fields (such as Earth's magnetic field), is introduced. Details are provided about the signal amplitude, dynamic range of the method, and conditions required to observe signal void in samples with specific T1 relaxation times. The experimental results obtained with MS DNPI are presented and discussed. In the experiments, electron spin resonance irradiation frequencies of 199 MHz and 16.2 MHz were employed. Also, T1 contrast manipulation in the polarizing and in the detection magnetic field is discussed and demonstrated for MS DNPI. PMID:8699950

Planinsic, G; Grucker, D; Stepisnik, J

1996-03-01

38

Differentiation of Breast Cancer from Fibroadenoma with Dual-Echo Dynamic Contrast-Enhanced MRI  

PubMed Central

Dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) of the breast is a routinely used imaging method which is highly sensitive for detecting breast malignancy. Specificity, though, remains suboptimal. Dynamic susceptibility contrast magnetic resonance imaging (DSC MRI), an alternative dynamic contrast imaging technique, evaluates perfusion-related parameters unique from DCE MRI. Previous work has shown that the combination of DSC MRI with DCE MRI can improve diagnostic specificity, though an additional administration of intravenous contrast is required. Dual-echo MRI can measure both T1W DCE MRI and T2*W DSC MRI parameters with a single contrast bolus, but has not been previously implemented in breast imaging. We have developed a dual-echo gradient-echo sequence to perform such simultaneous measurements in the breast, and use it to calculate the semi-quantitative T1W and T2*W related parameters such as peak enhancement ratio, time of maximal enhancement, regional blood flow, and regional blood volume in 20 malignant lesions and 10 benign fibroadenomas in 38 patients. Imaging parameters were compared to surgical or biopsy obtained tissue samples. Receiver operating characteristic (ROC) curves and area under the ROC curves were calculated for each parameter and combination of parameters. The time of maximal enhancement derived from DCE MRI had a 90% sensitivity and 69% specificity for predicting malignancy. When combined with DSC MRI derived regional blood flow and volume parameters, sensitivity remained unchanged at 90% but specificity increased to 80%. In conclusion, we show that dual-echo MRI with a single administration of contrast agent can simultaneously measure both T1W and T2*W related perfusion and kinetic parameters in the breast and the combination of DCE MRI and DSC MRI parameters improves the diagnostic performance of breast MRI to differentiate breast cancer from benign fibroadenomas.

Wang, Shiwei; DelProposto, Zachary; Wang, Haoyu; Ding, Xuewei; Ji, Conghua; Wang, Bei; Xu, Maosheng

2013-01-01

39

Screening applications for MRI in the detection of upper abdominal disease: comparative study of non-contrast-enhanced single-shot MRI and contrast-enhanced helical CT  

Microsoft Academic Search

.  \\u000a Purpose: To compare the value of ’push-button' singe-shot non-contrast-enhanced MRI and contrast-enhanced helical CT for detection\\u000a of upper abdominal disease. Methods: In 120 patients, images obtained with non contrast-enhanced single-shot MRI (T2: double echo HASTE, and T1: turbo FLASH)\\u000a and contrast-enhanced helical CT were compared. Lesions or abnormalities were divided in 8 anatomical categories (1: liver;\\u000a 2: pancreatobiliary; 3:

T. De Jaegere; L. Van Hoe; W. Van Steenbergen; E. Van Cutsem; H. Bosmans; E. Heindryckx; P. Loubeyre; G. Marchal

1999-01-01

40

MRI of ovarian masses.  

PubMed

MRI provides exquisite views of the pelvic anatomy through its high spatial resolution and tissue contrast, and as such plays a key role in the work up of ovarian lesions, identifying features that distinguish benign and malignant lesions. In the case of primary tumors it enables local staging and detection of metastatic disease to help guide management options such as complex surgery or the consideration of neoadjuvant chemotherapy. Functional MRI techniques such as diffusion-weighted MRI (DW-MRI), dynamic contrast-enhanced MRI (DCE-MRI) and tumor-selective molecular imaging are currently being evaluated as possible predictive and prognostic biomarkers in the context of ovarian malignancy, and may play a larger role in routine clinical practice in the future. Herein we provide an overview of the conventional and advanced MRI techniques used to characterize ovarian masses and of the role that MR plays in the staging, treatment selection and follow up of patients with ovarian cancer. PMID:23355430

Vargas, Hebert Alberto; Barrett, Tristan; Sala, Evis

2013-02-01

41

Three-dimensional images of liver tumours reconstructed by Gd-EOB-DTPA-enhanced MRI  

PubMed Central

The purpose of this study was to evaluate three-dimensional images of liver tumours obtained with gadolinium ethoxybenzyl diethylenetriamine penta-acetic acid (Gd-EOB-DTPA)-enhanced MRI (3D-EOB-MRI) in hepatic surgery. We conclude that 3D-EOB-MRI may be an alternative method for depicting liver tumours adjacent to the hepatic veins and portal branches, and may provide additional information for surgical planning.

Takeshita, K; Watanabe, A; Kutomi, K; Haruyama, T; Yamamoto, A; Furui, S; Sano, K

2012-01-01

42

Diagnosis of cirrhosis with intravoxel incoherent motion diffusion MRI and dynamic contrast-enhanced MRI alone and in combination: preliminary experience  

Microsoft Academic Search

PURPOSE: To report our preliminary experience with the use of intravoxel incoherent motion (IVIM) diffusion-weighted magnetic resonance imaging (DW-MRI) and dynamic contrast-enhanced (DCE)-MRI alone and in combination for the diagnosis of liver cirrhosis. MATERIALS AND METHODS: Thirty subjects (16 with noncirrhotic liver, 14 with cirrhosis) were prospectively assessed with IVIM DW-MRI (n = 27) and DCE-MRI (n = 20). IVIM

Jignesh Patel; Eric E. Sigmund; Henry Rusinek; Marcel Oei; James S. Babb; Bachir Taouli

2010-01-01

43

Can medial temporal lobe regions distinguish true from false? An event-related functional MRI study of veridical and illusory recognition memory.  

PubMed

To investigate the types of memory traces recovered by the medial temporal lobe (MTL), neural activity during veridical and illusory recognition was measured with the use of functional MRI (fMRI). Twelve healthy young adults watched a videotape segment in which two speakers alternatively presented lists of associated words, and then the subjects performed a recognition test including words presented in the study lists (True items), new words closely related to studied words (False items), and new unrelated words (New items). The main finding was a dissociation between two MTL regions: whereas the hippocampus was similarly activated for True and False items, suggesting the recovery of semantic information, the parahippocampal gyrus was more activated for True than for False items, suggesting the recovery of perceptual information. The study also yielded a dissociation between two prefrontal cortex (PFC) regions: whereas bilateral dorsolateral PFC was more activated for True and False items than for New items, possibly reflecting monitoring of retrieved information, left ventrolateral PFC was more activated for New than for True and False items, possibly reflecting semantic processing. Precuneus and lateral parietal regions were more activated for True and False than for New items. Orbitofrontal cortex and cerebellar regions were more activated for False than for True items. In conclusion, the results suggest that activity in anterior MTL regions does not distinguish True from False, whereas activity in posterior MTL regions does. PMID:11287664

Cabeza, R; Rao, S M; Wagner, A D; Mayer, A R; Schacter, D L

2001-04-03

44

Can medial temporal lobe regions distinguish true from false? An event-related functional MRI study of veridical and illusory recognition memory  

PubMed Central

To investigate the types of memory traces recovered by the medial temporal lobe (MTL), neural activity during veridical and illusory recognition was measured with the use of functional MRI (fMRI). Twelve healthy young adults watched a videotape segment in which two speakers alternatively presented lists of associated words, and then the subjects performed a recognition test including words presented in the study lists (True items), new words closely related to studied words (False items), and new unrelated words (New items). The main finding was a dissociation between two MTL regions: whereas the hippocampus was similarly activated for True and False items, suggesting the recovery of semantic information, the parahippocampal gyrus was more activated for True than for False items, suggesting the recovery of perceptual information. The study also yielded a dissociation between two prefrontal cortex (PFC) regions: whereas bilateral dorsolateral PFC was more activated for True and False items than for New items, possibly reflecting monitoring of retrieved information, left ventrolateral PFC was more activated for New than for True and False items, possibly reflecting semantic processing. Precuneus and lateral parietal regions were more activated for True and False than for New items. Orbitofrontal cortex and cerebellar regions were more activated for False than for True items. In conclusion, the results suggest that activity in anterior MTL regions does not distinguish True from False, whereas activity in posterior MTL regions does.

Cabeza, Roberto; Rao, Stephen M.; Wagner, Anthony D.; Mayer, Andrew R.; Schacter, Daniel L.

2001-01-01

45

Distinct laterality alterations distinguish mild cognitive impairment and Alzheimer's disease from healthy aging: Statistical parametric mapping with high resolution MRI.  

PubMed

Laterality of human brain varies under healthy aging and diseased conditions. The alterations in hemispheric asymmetry may embed distinct biomarkers linked to the disease dynamics. Statistical parametric mapping based on high-resolution magnetic resonance imaging (MRI) and image processing techniques have allowed automated characterization of morphological features across the entire brain. In this study, 149 subjects grouped in healthy young, healthy elderly, mild cognitive impairment (MCI), and Alzheimer's disease (AD) were investigated using multivariate analysis for regional cerebral laterality indexed by surface area, curvature index, cortical thickness, and subjacent white matter volume measured on high-resolution MR images. Asymmetry alteration of MCI and AD were characterized by marked region-specific reduction, while healthy elderly featured a distinct laterality shift in the limbic system in addition to regional asymmetry loss. Lack of the laterality shift in limbic system and early loss of asymmetry in entorhinal cortex may be biomarkers to identify preclinical AD among other dementia. Multivariate analysis of hemispheric asymmetry may provide information helpful for monitoring the disease progress and improving the management of MCI and AD. Hum Brain Mapp 34:3400-3410, 2013. © 2012 Wiley Periodicals, Inc. PMID:22927141

Long, Xiaojing; Zhang, Lijuan; Liao, Weiqi; Jiang, Chunxiang; Qiu, Bensheng

2012-08-28

46

Interpretation and applicability of empirical tissue enhancement metrics in dynamic contrast-enhanced MRI based on a multiple pathway model  

Microsoft Academic Search

Computer simulations based on a physiologically realistic tracer kinetic model with multiple pathways was used to provide insights on the applicability and interpretation of tissue enhancement metrics such as the maximum slope, peak enhancement and area under curve, commonly used in dynamic contrast-enhanced (DCE) MRI. Results show that physiological conditions of the tissue that could affect the accuracy of the

T S Koh; W Shi; C H Thng; J W Kwek; S Bisdas; J B K Khoo

2012-01-01

47

Impatient MRI: Illinois Massively Parallel Acceleration Toolkit for image reconstruction with enhanced throughput in MRI  

Microsoft Academic Search

Much progress has been made in the design of efficient acquisition trajectories for high spatial and temporal resolution in magnetic resonance imaging (MRI). Additionally, significant developments in image reconstruction have enabled the reconstruction of reasonable images from massively undersampled or noisy data that is corrupted by a variety of physical effects, including magnetic field inhomogeneity. Translation of these techniques into

Xiao-Long Wu; Jiading Gai; Fan Lam; Maojing Fu; Justin P. Haldar; Yue Zhuo; Zhi-Pei Liang; Wen-Mei Hwu; Bradley P. Sutton

2011-01-01

48

Polymeric PARACEST Agents for Enhancing MRI Contrast Sensitivity  

PubMed Central

Linear polymers of PARACEST agents were prepared by using classical free radical chain polymerization conditions. The Eu3+-polymers exhibited similar intermediate-to-slow water exchange and CEST characteristics as the Eu3+-monomers. This provided an avenue to lower the detection limit of these imaging agents substantially and makes them potentially useful as MRI sensors for molecular imaging.

Wu, Yunkou; Zhou, Youfu; Quari, Olivier; Woods, Mark; Zhao, Piyu; Soesbe, Todd C.; Kiefer, Garry E.; Sherry, A. Dean

2009-01-01

49

An Aid to Decision-Making in Therapy of Retroperitoneal Fibrosis: Dynamic Enhancement Analysis of Gadolinium MRI  

PubMed Central

Background Idiopathic retroperitoneal fibrosis (IRF) as an uncommon cause of obstructive uropathy is often primarily treated medically by the attending urologist. We evaluated dynamic enhancement analysis (DEA) as a possible predictor of response to medical treatment and for treatment monitoring. Methods From 2007, 24 patients with fibrosis were assessed by magnetic resonance imaging (MRI) with DEA. The dynamic enhancement quotient (DEQ) was measured before therapy with prednisone (n = 12) or tamoxifen (n = 12) and in follow-up investigations after 3 and 6 months. Response to medical treatment was recorded by changes in the retroperitoneal mass on MRI and possible relief of ureteral obstruction, which was monitored by intravenous pyelogram and/or MAG3 scan after removal of DJ stents. Results Treatment groups did not differ significantly as to age, gender, or laboratory values, and response to medical treatment showed no significant difference between agents. Overall there were no cases of progression, 2 cases of stable disease, 11 cases of mild fibrotic regression, and 11 of significant or complete regression. DJ stents could successfully be removed in 21 of 35 renal units (60.0%). In a total of 61 DEAs the DEQ was significantly higher (P < 0.001) in patients with a good response (DEQ = 4.02) than in those with an average response (3.11) or none (2.14). Conclusions DEA was able to distinguish between patients with different response rates to medical treatment of IRF and may be useful to individualize therapeutic decision-making.

Brandt, Alexander Sascha; Kamper, Lars; Kukuk, Sonja; Piroth, Werner; Haage, Patrick; Roth, Stephan

2013-01-01

50

Glucose Administration Enhances fMRI Brain Activation and Connectivity Related to Episodic Memory Encoding for Neutral and Emotional Stimuli  

ERIC Educational Resources Information Center

|Glucose enhances memory in a variety of species. In humans, glucose administration enhances episodic memory encoding, although little is known regarding the neural mechanisms underlying these effects. Here we examined whether elevating blood glucose would enhance functional MRI (fMRI) activation and connectivity in brain regions associated with…

Parent, Marise B.; Krebs-Kraft, Desiree L.; Ryan, John P.; Wilson, Jennifer S.; Harenski, Carla; Hamann, Stephan

2011-01-01

51

[Patterns of delayed-enhancement in MRI of ischemic and non-ischemic cardiomyopathies].  

PubMed

Contrast-enhanced MRI using the delayed-enhancement technique (DE-MRI) is widely applied in the clinical work-up of myocardial diseases. Myocardial diseases of varying etiology result in myocardial changes, such as necrosis, fibrosis, edema and metabolite deposition, which can be visualized by DE-MRI. Acute and chronic ischemic diseases based on a coronary artery disease as well as non-ischemic cardiomyopathies display DE. Cardiomyopathies often show a characteristic enhancement pattern. While ischemic lesions are localized in the subendocardium, non-ischemic cardiomyopathies often display an intramyocardial or subepicardial pattern. The typical pattern for dilated cardiomyopathies is band-like and intramyocardial with septal involvement. Arrhythmogenic right-ventricular dysplasias/cardiomyopathies are frequently associated with right-ventricular DE. In the case of amyloid cardiomyopathies which are often restrictive cardiomyopathies, subendocardial and circular DE is typically observed. Hypertrophic cardiomyopathies display patchy intramyocardial DE usually in the anteroseptal region. Acute myocarditis is typically accompanied by intramyocardial or subepicardial DE affecting the lateral wall. In the case of chronic myocarditis, intramyocardial or subepicardial DE is observed most frequently. Cardiac sarcoidosis typically entails patchy subepicardial DE with right- and left-ventricular involvement. Since there is an overlap between the enhancement patterns of cardiomyopathies, the diagnostic accuracy of DE-MRI is limited and the diagnosis must be based on additional clinical and MRI findings. The amount of DE often corresponds with cardiac functional parameters as well as with the frequency of cardiac events so that DE-MRI may be useful for risk stratification. Furthermore, DE-MRI can be helpful in the planning and evaluation of myocardial biopsies and electrophysiological examinations. PMID:17203440

Stork, A; Müllerleile, K; Bansmann, P M; Koops, A; Meinertz, T; Adam, G; Lund, G K

2007-01-01

52

EVALUATION OF DYNAMIC CONTRAST- ENHANCED MRI IN DETECTING RENAL SCARRING IN A RAT INJURY MODEL  

PubMed Central

Purpose To create a reliable rat model with small renal cortical scars and evaluate the accuracy and sensitivity of dynamic contrast-enhanced magnetic resonance imaging (MRI) in detecting the kinds of lesions that are associated with reflux nephropathy. Materials and Methods In 16 rats, 3 unilateral renal cortical lesions were created using either electrocautery or pure alcohol with the contralateral kidney serving as control. MRI on a 1.5 T GE Signa was performed 10 – 14 days after surgery. After bolus injection of 0.2 mM/Kg Gd-DTPA, sequential MRI acquisitions were performed using a 4-inch quadrature birdcage coil. Renal and scar volumes and pathology were compared after scanning and sacrifice. Results Forty of the 48 points of injury (83%) in the 16 rats were detected grossly. Under microscopy, 36 injuries (75%) were detected on mid-kidney cross-sections. The average lesion was 4.2 mm3 corresponding to 0.5% of the kidney volume. Using pathological findings as the gold standard, the sensitivity and specificity of scar detection using MRI was 69% and 93% respectively. Conclusion A rat model was created to demonstrate the sensitivity of dynamic contrast-enhanced MRI for detecting renal scars. Alcohol and electrocautery created reliable renal scars that were confirmed pathologically. MRI detected these lesions that averaged 4.2 mm3 (0.5% total renal volume) with sensitivity and specificity of 69% and 93% respectively.

Wang, Bingyin; Sommer, Graham; Spielman, Daniel; Dairiki Shortliffe, Linda M.

2010-01-01

53

Characteristics of axillary lymph nodes apparent on dynamic contrast-enhanced breast MRI in healthy women.  

PubMed

The study was initiated to characterize and better understand the natural characteristics of axillary lymph nodes (LNs) apparent on dynamic breast magnetic resonance imaging (MRI). The most important finding in 71 subjects that included healthy women was that 41% showed strong enhanced axillary LNs. The dynamic curves of these LNs revealed an initial mean signal increase of 197% (±58%), all of them with a following plateau (34%) or washout (66%). Our study points out that the previous understanding of contrast enhancement in breast lesions should be taken with care when assessing axillary LNs. This has to be considered especially in preoperative breast MRI. PMID:22726960

Krammer, Julia; Engel, Dorothee; Nissen, Johanna; Schnitzer, Andreas; Suetterlin, Marc; Schoenberg, Stefan O; Wasser, Klaus

2012-06-08

54

Topiramate-induced acute myopia with MRI contrast enhancement.  

PubMed

Topiramate is a sulfamate-substituted monosaccharide mainly used to treat epilepsy in children and adults and prophylaxis of migraine. This article describes a case of topiramate-induced acute transient myopia. The underlying mechanism and management is discussed. A 13-year-old female complained of sudden onset of blurred vision; 7 days prior to this she had commenced topiramate therapy for migraine prophylaxis. Visual acuity was reduced in both eyes. Examination revealed myopic refractive changes which resolved quickly following discontinuation of the drug. An MRI showed uveoscleral and subcutaneous cellular tissue abnormalities in the T1 contrasted images. PMID:22427296

Latini, Manuel Facundo; Romano, Lucas Martín

2012-02-03

55

Relationships between dynamic contrast-enhanced MRI findings and pattern of invasion for tongue carcinoma.  

PubMed

The purpose of this study was to evaluate the effectiveness of dynamic contrast-enhanced MRI (DC-MRI) for assessing the pattern of invasion of tongue carcinomas. We studied 20 cases of squamous cell carcinoma of the tongue that showed peripheral enhancement patterns on DC-MRI. The diameter of each tumor was >2.0 cm and no apparent artifacts were seen. The signal enhancement to noise ratio (SE/N) of the regions of interest, which were located in the central and peripheral regions of the tumor, were measured using DC-MRI, while maximum SE/N, %-wash out, and the ascending rate of SE/N were also calculated. The histopathological pattern of invasion was assessed in each case and used to classify them into clear (13 cases) and diffuse (7 cases) groups, after which the 4 parameters were compared between the 2 groups. The ascending rate of SE/N in the peripheral region was significantly lower in the diffuse group (p=0.047). There were no other significant differences between the 2 groups for any parameter in either tumor region. These results suggest that DC-MRI is able to show the histopathological pattern of invasion into surrounding structures. PMID:16596208

Ariyoshi, Yasunori; Shimahara, Masashi

2006-05-01

56

Synergistic Enhancement of Iron Oxide Nanoparticle and Gadolinium for Dual-Contrast MRI  

PubMed Central

Purpose The use of MR contrast agents allows accurate diagnosis by exerting an influence on the longitudinal (T1) or transverse (T2) relaxation time of the surrounding tissue. In this study, we combined the use of iron oxide (IO) particles and nonspecific extracellular gadolinium chelate (Gd) in order to further improve the sensitivity and specificity of lesion detection. Procedures With a 7-Tesla scanner, pre-contrasted, IO-enhanced and dual contrast agent enhanced MRIs were performed in phantom, normal animals, and animal models of lymph node tumor metastases and orthotopic brain tumor. For the dual-contrast (DC) MRI, we focused on the evaluation of T2 weighted DC MRI with IO administered first, then followed by the injection of a bolus of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Results Quantified with C/N ratios and MRI relaxometry, the synergistic effect of coordinated administration of Gd-DTPA and IO was observed and confirmed in phantom, normal liver and tumor models. At 30 min after administration of Feridex, Gd-DTPA further decreased T2 relaxation in liver immediately after the injection. Additional administration of Gd-DTPA also immediately increased the signal contrast between tumor and brain parenchyma and maximized the C/N ratio to ?4.12 ± 0.71. Dual contrast MRI also enhanced the delineation of tumor borders and small lesions. Conclusions DC-MRI will be helpful to improve diagnostic accuracy and decrease the threshold size for lesion detection.

Zhang, Fan; Huang, Xinglu; Qian, Chunqi; Zhu, Lei; Hida, Naoki; Niu, Gang; Chen, Xiaoyuan

2012-01-01

57

High speed 3D overhauser-enhanced MRI using combined b-SSFP and compressed sensing.  

PubMed

PURPOSE: Overhauser-enhanced MRI is a promising technique for imaging the distribution and dynamics of free radicals. A key challenge for Overhauser-enhanced MRI is attaining high spatial and temporal resolution while simultaneously limiting resonator and sample heating due to the long, high power radio-frequency pulses needed to saturate the electron resonance. METHODS: The approach presented here embeds EPR pulses within a balanced steady state free precession sequence. Unlike other Overhauser-enhanced MRI methods, no separate Overhauser prepolarization step is required. This steady-state approach also eliminates the problem of time-varying Overhauser-enhanced signal and provides constant polarization in the sample during the acquisition. A further increase in temporal resolution was achieved by incorporating undersampled k-space strategies and compressed sensing reconstruction. RESULTS: We demonstrate 1 × 2 × 3.5 mm(3) resolution at 6.5 mT across a 54 × 54 × 110 mm(3) sample in 33 s while sampling 30% of k-space. CONCLUSION: The work presented here overcomes the main limitations of Overhauser enhanced MRI as previously described in the literature, drastically improving speed and resolution, and enabling new opportunities for the measurement of free radicals in living organisms, and for the study of dynamic processes such as metabolism and flow. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc. PMID:23475813

Sarracanie, Mathieu; Armstrong, Brandon D; Stockmann, Jason; Rosen, Matthew S

2013-03-01

58

A Nanocomplex System as Targeted Contrast Agent Delivery Vehicle for MRI Dynamic Contrast Enhancement Study  

PubMed Central

We have developed and tested a liposomal nanocomplex system, which contains Gd-DTPA as a payload and transferrin on the surface, as a tumor specific targeting MRI contrast agent for studying prostate cancer tumors in mice. In vivo, the probe significantly enhanced the MRI signal. The image contrast between the peripheral region of the tumor and the non-involved muscle was nearly 50% higher two hours after administration of the nanocomplex. The liposomal nanocomplex increased the amount of Gd accumulated in tumors by factor 2.8 compared to that accumulated by using Magnevist alone. Moreover, the heterogeneous MRI image features correlate well with the tumor pathology. The image enhancement patterns can be used for cancer prognosis and non-invasive monitoring of the response to therapy.

Korotcov, Alexandru; Shan, Liang; Meng, Huan; Wang, Tongxin; Sridhar, Rajagopalan; Zhao, Yuliang; Liang, Xing-Jie; Wang, Paul C.

2010-01-01

59

MRI  

NSDL National Science Digital Library

This patient education program explains Magnetic Resonance Imaging (MRI), the role of this imaging in diagnosis, the procedure itself, and associated benefits and risks. This is a MedlinePlus Interactive Health Tutorial from the National Library of Medicine, designed and developed by the Patient Education Institute. NOTE: The tutorial requires a special Flash plug-in, version 4 or above. If you do not have Flash, you will be prompted to obtain a free download of the software before you start the tutorial. You will also need an Acrobat Reader, available as a free download, in order to view the Reference Summary.

Institute, Patient E.

2008-09-10

60

MRI-guided gas bubble enhanced ultrasound heating in in vivo rabbit thigh  

Microsoft Academic Search

In this study, we propose a focused ultrasound surgery protocol that induces and then uses gas bubbles at the focus to enhance the ultrasound absorption and ultimately create larger lesions in vivo. MRI and ultrasound visualization and monitoring methods for this heating method are also investigated. Larger lesions created with a carefully monitored single ultrasound exposure could greatly improve the

S. D. Sokka; R. King; K. Hynynen

2003-01-01

61

[Lumbar radiculopathy presenting neuralgic amyotrophy with gadolinium-enhanced MRI lesions: a case report].  

PubMed

A 40-year-old man presented with sudden onset of severe left buttock pain that radiated down the thigh to the leg. On examination, he showed moderate weakness and atrophy in the left quadriceps and tibialis anterior muscles, and absence of a left patellar tendon reflex. Needle electromyography revealed an active denervation pattern in the left quadriceps muscles, suggesting neuralgic amyotrophy. Contrast-enhanced MRI showed abnormal enhancement of the left cauda equina. Steroid pulse therapy relieved pain, and subsequent high-dose intravenous immunoglobulin prevented progression of muscle atrophy and weakness. Neuralgic amyotrophy is characterized by attacks of severe neuropathic pain and subsequent patchy paresis in the upper or lower extremities. Since overall recovery is less favourable than usually assumed, early diagnosis is very important. This case was remarkable in that contrast-enhanced MRI revealed abnormal enhancement and thickening of the cauda equina, which may help in achieving early diagnosis and treatment. PMID:22354236

Unoda, Ki-Ichi; Ito, Takumi; Nakajima, Hideto

2012-01-01

62

Neural Correlates of Feigned Memory Impairment are Distinguishable from Answering Randomly and Answering Incorrectly: An fMRI and Behavioral Study  

ERIC Educational Resources Information Center

|Previous functional magnetic resonance imaging (fMRI) studies have identified activation in the prefrontal-parietal-sub-cortical circuit during feigned memory impairment when comparing with truthful telling. Here, we used fMRI to determine whether neural activity can differentiate between answering correctly, answering randomly, answering…

Liang, Chun-Yu; Xu, Zhi-Yuan; Mei, Wei; Wang, Li-Li; Xue, Li; Lu, De Jian; Zhao, Hu

2012-01-01

63

Neural Correlates of Feigned Memory Impairment are Distinguishable from Answering Randomly and Answering Incorrectly: An fMRI and Behavioral Study  

ERIC Educational Resources Information Center

Previous functional magnetic resonance imaging (fMRI) studies have identified activation in the prefrontal-parietal-sub-cortical circuit during feigned memory impairment when comparing with truthful telling. Here, we used fMRI to determine whether neural activity can differentiate between answering correctly, answering randomly, answering…

Liang, Chun-Yu; Xu, Zhi-Yuan; Mei, Wei; Wang, Li-Li; Xue, Li; Lu, De Jian; Zhao, Hu

2012-01-01

64

Can medial temporal lobe regions distinguish true from false? An event-related functional MRI study of veridical and illusory recognition memory  

Microsoft Academic Search

To investigate the types of memory traces recovered by the medial temporal lobe (MTL), neural activity during veridical and illusory recognition was measured with the use of functional MRI (fMRI). Twelve healthy young adults watched a videotape segment in which two speakers alternatively presented lists of associated words, and then the subjects performed a recognition test including words presented in

Roberto Cabeza; Stephen M. Rao; Anthony D. Wagner; Andrew R. Mayer; Daniel L. Schacter

2001-01-01

65

Relationship of MRI Delayed Contrast Enhancement to Irreversible Injury, Infarct Age, and Contractile Function  

Microsoft Academic Search

Background—Contrast MRI enhancement patterns in several pathophysiologies resulting from ischemic myocardial injury are controversial or have not been investigated. We compared contrast enhancement in acute infarction (AI), after severe but reversible ischemic injury (RII), and in chronic infarction. Methods and Results—In dogs, a large coronary artery was occluded to study AI and\\/or chronic infarction (n 518), and a second coronary

Raymond J. Kim; David S. Fieno; Todd B. Parrish; Kathleen Harris; Enn-Ling Chen; Orlando Simonetti; Jeffrey Bundy; J. Paul Finn; Francis J. Klocke; Robert M. Judd

66

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

PubMed

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

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

2013-04-24

67

Noninvasive assessment of hepatic fibrosis using gadoxetate-disodium-enhanced 3T MRI.  

PubMed

Introduction. Gadoxetate-disodium is a liver-specific MR contrast agent absorbed by hepatocytes via organic anion transporting polypeptide 1B3 and is excreted into the biliary system by multidrug resistance-associated protein 2. It has been suggested that relative parenchymal enhancement on hepatocyte phase image is associated with hepatic function. However, it is not clear whether gadoxetate-disodium-enhanced MRI can be used as a noninvasive fibrosis marker. Thus, the purpose of our study was to evaluate the diagnostic performance of gadoxetate-disodium-enhanced MRI in predicting the hepatic fibrosis stage. Materials and methods. A total of 113 patients who had fibrosis staged according to the Batts and Ludwig score were enrolled: F0 (n = 13), F1 (n = 18), F2 (n = 15), F3 (n = 32), and F4 (n = 35). All patients underwent gadoxetate-disodium-enhanced MRI before confirmation by biopsy (n = 67) or surgery (n = 46). For quantitative analysis, the contrast enhancement index (CEI) was calculated by measuring the signal intensity (SI) in liver and paraspinal muscle using a region of interest, as follows: CEI = (liver SI/paraspinal muscle SI) 20 min hepatocyte phase image/(liver SI/paraspinal muscle SI) pre-contrast T1-weighted image. The diagnostic performance was evaluated by the ROC curve, adjusted for the prevalence of each fibrosis stage. Results. A significant negative correlation was observed between CEI and fibrosis stage (r = -0.545, P < 0.0001). The adjusted AUROC for CEI in the prediction of mild (??F1), moderate (? F2), or severe fibrosis (? F3) and liver cirrhosis (F4) was 0.668, 0.703, 0.73, and 0.84, respectively. In conclusion, our results demonstrate that quantitative analysis of relative hepatic enhancement using gadoxetate-disodium-enhanced MRI can predict the hepatic fibrosis stage. PMID:24114823

Jang, Yun-Jin; Cho, Seung Hyun Cho; Bae, Ji Hea; Kim, Gab Chul; Ryeom, Hunkyu; Kim, Hye Jung; Shin, Kyung-Min; Lee, Hui Joong

68

Tracer kinetic model-driven registration for dynamic contrast-enhanced MRI time-series data.  

PubMed

Dynamic contrast-enhanced MRI (DCE-MRI) time series data are subject to unavoidable physiological motion during acquisition (e.g., due to breathing) and this motion causes significant errors when fitting tracer kinetic models to the data, particularly with voxel-by-voxel fitting approaches. Motion correction is problematic, as contrast enhancement introduces new features into postcontrast images and conventional registration similarity measures cannot fully account for the increased image information content. A methodology is presented for tracer kinetic model-driven registration that addresses these problems by explicitly including a model of contrast enhancement in the registration process. The iterative registration procedure is focused on a tumor volume of interest (VOI), employing a three-dimensional (3D) translational transformation that follows only tumor motion. The implementation accurately removes motion corruption in a DCE-MRI software phantom and it is able to reduce model fitting errors and improve localization in 3D parameter maps in patient data sets that were selected for significant motion problems. Sufficient improvement was observed in the modeling results to salvage clinical trial DCE-MRI data sets that would otherwise have to be rejected due to motion corruption. PMID:17969122

Buonaccorsi, Giovanni A; O'Connor, James P B; Caunce, Angela; Roberts, Caleb; Cheung, Sue; Watson, Yvonne; Davies, Karen; Hope, Lynn; Jackson, Alan; Jayson, Gordon C; Parker, Geoffrey J M

2007-11-01

69

USPIO-enhanced MRI for preoperative staging of gynecological pelvic tumors: preliminary results.  

PubMed

The aim of this study was to assess nodal enhancement with ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI) during preoperative staging of gynecological pelvic tumors within the same imaging session for the primary tumor. Pelvic MRI was performed 18-28 h after intravenous infusion of USPIO (Combidex/Sinerem, 2.6 mg Fe/kg body weight) in 13 women (mean age 51 years) scheduled for surgery for biopsy proven ( n=11) or clinically suspected ( n=2) uterine carcinoma. Axial T1-weighted spin-echo (SE), T2-weighted fast SE (FSE; with fat saturation), fast spoiled gradient-recalled (FSPGR) echo, sagittal and oblique T2-weighted FSE sequences were acquired on a 1.5-T system. Lymph nodes were prospectively staged using standard criteria, i.e., size and shape, as well as USPIO enhancement. Results were correlated with histology findings. MRI correctly staged all primary uterine tumors. In one case, the preoperative diagnosis of stage IV switched the therapeutic approach to radiochemotherapy. Ninety-one (86 benign, 5 malignant) of the histologically characterized nodes could be correlated with their MRI counterparts. One node was false positive; three micrometastases greater than 5 mm and one 5-mm metastasis were missed. On a nodal basis, the sensitivity score was 0.33 and the specificity score, 0.99. On a patient basis, the sensitivity score was 0.25 and the specificity score, 0.80. Our preliminary results indicate that USPIO-enhanced pelvic MRI for preoperative nodal assessment is feasible within one imaging session for primary tumors and that it has a high specificity. However, the low sensitivity in the present study is a limitation for the clinical application of this technique. PMID:14991323

Keller, Thomas M; Michel, Sven C A; Fröhlich, Johannes; Fink, Daniel; Caduff, Rosmarie; Marincek, Borut; Kubik-Huch, Rahel A

2004-02-26

70

Using the magnitude of PSA bounce after MRI-guided prostate brachytherapy to distinguish recurrence, benign precipitating factors, and idiopathic bounce  

Microsoft Academic Search

Purpose: To identify events that precipitated a prostate-specific antigen (PSA) bounce and characterize the magnitude, duration, and time to PSA bounce after MRI-guided prostate brachytherapy.Methods and Materials: Between 1997 and 2001, 186 patients with low-risk prostate cancer underwent MRI-guided permanent 125I source implantation, with or without external beam radiotherapy. A PSA bounce was defined as a ?15% elevation in PSA

Prajnan Das; Ming-H Chen; Kristin Valentine; Lynn Lopes; Robert A Cormack; Andrew A Renshaw; Clare M Tempany; Sanjaya Kumar; Anthony V D’Amico

2002-01-01

71

[Non-masslike enhancement on breast MRI: interpretation pearls].  

PubMed

The MR Breast Imaging Reporting and Data System (BI-RADS) lexicon of the American College of Radiology (ACR) includes a new lesion category defined as non-masslike enhancement. The purpose of this paper is to review the definition of this new entity, illustrate the main imaging features described in the BI-RADS lexicon and to propose a diagnostic approach based on data from the literature in order to achieve diagnosis and optimal patient management. PMID:19421111

Thomassin-Naggara, I; Salem, C; Darai, E; Bazot, M; Uzan, S; Marsault, C; Chopier, J

2009-03-01

72

Cardiac Amyloidosis: Typical Imaging Findings and Diffuse Myocardial Damage Demonstrated by Delayed Contrast-Enhanced MRI  

SciTech Connect

Amyloidosis is a rare systemic disease. However, involvement of the heart is a common finding and is the most frequent cause of death in amyloidosis. We report the sonographic, scintigraphic, and MRI features of a pathologically proven case of cardiac amyloidosis. Delayed contrast-enhanced MR images, using an inversion recovery prepped gradient-echo sequence, revealed diffuse enhancement in the wall of both left and right ventricles. This enhancement suggested expansion of the extracellular space of the myocardium caused by diffuse myocardial necrosis secondary to deposition of amyloid.

Sueyoshi, Eijun, E-mail: EijunSueyoshi@aol.com; Sakamoto, Ichiro; Okimoto, Tomoaki; Hayashi, Kuniaki [Nagasaki University School of Medicine, Department of Radiology (Japan); Tanaka, Kyouei; Toda, Genji [Nagasaki University School of Medicine, Department of Cardiology (Japan)

2006-08-15

73

Perceptual enhancement of arteriovenous malformation in MRI angiography displays  

NASA Astrophysics Data System (ADS)

The importance of presenting medical images in an intuitive and usable manner during a procedure is essential. However, most medical visualization interfaces, particularly those designed for minimally-invasive surgery, suffer from a number of issues as a consequence of disregarding the human perceptual, cognitive, and motor system's limitations. This matter is even more prominent when human visual system is overlooked during the design cycle. One example is the visualization of the neuro-vascular structures in MR angiography (MRA) images. This study investigates perceptual performance in the usability of a display to visualize blood vessels in MRA volumes using a contour enhancement technique. Our results show that when contours are enhanced, our participants, in general, can perform faster with higher level of accuracy when judging the connectivity of different vessels. One clinical outcome of such perceptual enhancement is improvement of spatial reasoning needed for planning complex neuro-vascular operations such as treating Arteriovenous Malformations (AVMs). The success of an AVM intervention greatly depends on fully understanding the anatomy of vascular structures. However, poor visualization of pre-operative MRA images makes the planning of such a treatment quite challenging.

Abhari, Kamyar; Baxter, John S. H.; Eagleson, Roy; Peters, Terry; de Ribaupierre, Sandrine

2012-02-01

74

Dynamic Contrast-Enhanced MRI of Cervical Cancers: Temporal Percentile Screening of Contrast Enhancement Identifies Parameters for Prediction of Chemoradioresistance  

SciTech Connect

Purpose: To systematically screen the tumor contrast enhancement of locally advanced cervical cancers to assess the prognostic value of two descriptive parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Methods and Materials: This study included a prospectively collected cohort of 81 patients who underwent DCE-MRI with gadopentetate dimeglumine before chemoradiotherapy. The following descriptive DCE-MRI parameters were extracted voxel by voxel and presented as histograms for each time point in the dynamic series: normalized relative signal increase (nRSI) and normalized area under the curve (nAUC). The first to 100th percentiles of the histograms were included in a log-rank survival test, resulting in p value and relative risk maps of all percentile-time intervals for each DCE-MRI parameter. The maps were used to evaluate the robustness of the individual percentile-time pairs and to construct prognostic parameters. Clinical endpoints were locoregional control and progression-free survival. The study was approved by the institutional ethics committee. Results: The p value maps of nRSI and nAUC showed a large continuous region of percentile-time pairs that were significantly associated with locoregional control (p < 0.05). These parameters had prognostic impact independent of tumor stage, volume, and lymph node status on multivariate analysis. Only a small percentile-time interval of nRSI was associated with progression-free survival. Conclusions: The percentile-time screening identified DCE-MRI parameters that predict long-term locoregional control after chemoradiotherapy of cervical cancer.

Andersen, Erlend K.F. [Department of Medical Physics, Oslo University Hospital, Oslo (Norway); Hole, Knut Hakon; Lund, Kjersti V. [Department of Radiology, Oslo University Hospital, Oslo (Norway); Sundfor, Kolbein [Department of Gynaecological Oncology, Oslo University Hospital, Oslo (Norway); Kristensen, Gunnar B. [Department of Gynaecological Oncology, Oslo University Hospital, Oslo (Norway); Institute for Medical Informatics, Oslo University Hospital, Oslo (Norway); Lyng, Heidi [Department of Radiation Biology, Oslo University Hospital, Oslo (Norway); Malinen, Eirik, E-mail: eirik.malinen@fys.uio.no [Department of Medical Physics, Oslo University Hospital, Oslo (Norway); Department of Physics, University of Oslo, Oslo (Norway)

2012-03-01

75

Motion compensated generalized reconstruction for free-breathing dynamic contrast-enhanced MRI.  

PubMed

The analysis of abdominal and thoracic dynamic contrast-enhanced MRI is often impaired by artifacts and misregistration caused by physiological motion. Breath-hold is too short to cover long acquisitions. A novel multipurpose reconstruction technique, entitled dynamic contrast-enhanced generalized reconstruction by inversion of coupled systems, is presented. It performs respiratory motion compensation in terms of both motion artefact correction and registration. It comprises motion modeling and contrast-change modeling. The method feeds on physiological signals and x-f space properties of dynamic series to invert a coupled system of linear equations. The unknowns solved for represent the parameters for a linear nonrigid motion model and the parameters for a linear contrast-change model based on B-splines. Performance is demonstrated on myocardial perfusion imaging, on six simulated data sets and six clinical exams. The main purpose consists in removing motion-induced errors from time-intensity curves, thus improving curve analysis and postprocessing in general. This method alleviates postprocessing difficulties in dynamic contrast-enhanced MRI and opens new possibilities for dynamic contrast-enhanced MRI analysis. PMID:20882640

Filipovic, M; Vuissoz, P-A; Codreanu, A; Claudon, M; Felblinger, J

2010-09-29

76

Immobilized Contrast Enhanced (ICE) MRI: Gadolinium-based long-term MR Contrast Enhancement of the Vein Graft Vessel Wall*  

PubMed Central

An implantable MR contrast agent that can be covalently immobilized on tissue during surgery has been developed. The rationale is that a durable increase in tissue contrast using an implantable contrast agent can enhance post-surgical tissue differentiation using MRI. For small vessel (e.g., vein graft) MRI, the direct benefit of such permanent “labeling” of the vessel wall by modification of its relaxation properties is to achieve more efficient imaging. This efficiency can be realized as either increased contrast leading to more accurate delineation of vessel wall and lesion tissue boundaries, or, faster imaging without penalizing contrast-to-noise ratio, or a combination thereof. We demonstrate, for the first time, stable long-term MRI enhancement using such an exogenous contrast mechanism based on immobilizing a modified Gd-DTPA complex on a human vein using a covalent amide bond. Signal enhancement due to the covalently immobilized contrast agent is demonstrated for excised human vein specimens imaged at 3T, and its long-term stability is demonstrated during a 4-month incubation period.

Mitsouras, Dimitris; Vemula, Praveen Kumar; Yu, Peng; Tao, Ming; Nguyen, Binh T.; Campagna, Christina M.; Karp, Jeffrey M.; Mulkern, Robert V.; Ozaki, C. Keith; Rybicki, Frank J.

2010-01-01

77

Real-time virtual sonography, a coordinated sonography and MRI system that uses magnetic navigation, improves the sonographic identification of enhancing lesions on breast MRI.  

PubMed

This study verified that recently developed real-time virtual sonography (RVS) to coordinate a sonography image and the magnetic resonance imaging (MRI) multiplanar reconstruction (MPR) with magnetic navigation was useful. The purpose of this study was to evaluate the accuracy of RVS to sonographically identify enhancing lesions by breast MRI. Between December 2008 and May 2009, RVS was performed in 51 consecutive patients with 63 enhancing lesions. MRI was performed with the patients in the supine position using a 1.5-T imager with a body surface coil to achieve the same position as with sonography. To assess the accuracy of the RVS, the following three issues were analyzed: (i) The sonographic detection rate of enhancing lesions, (ii) the comparison of the tumor size measured by sonography and the MRI-MPR and (iii) the positioning errors as the distance from the actual sonographic position to the expected MRI position in 3-D. Among the 63 enhancing lesions, 42 (67%) lesions were identified by conventional B-mode, whereas the remaining 21 (33%) initial conventional B-mode occult lesions were identified by RVS alone. The sonographic size of the lesions detected by RVS alone was significantly smaller than that of lesions detected by conventional B-mode (p < 0.001). The mean tumor size provided by RVS was 12.3 mm for real-time sonography and 14.1 mm for MRI-MPR (r = 0.848, p < 0.001). The mean positioning errors for the transverse and sagittal planes and the depth from the skin were 7.7, 6.9 and 2.8 mm, respectively. The overall mean 3D positioning error was 12.0 mm. Our results suggest that RVS has good targeting accuracy to directly compare a sonographic image with MRI results without operator dependence. PMID:22137178

Nakano, Shogo; Yoshida, Miwa; Fujii, Kimihito; Yorozuya, Kyoko; Kousaka, Junko; Mouri, Yukako; Fukutomi, Takashi; Ohshima, Yukihiko; Kimura, Junko; Ishiguchi, Tsuneo

2012-01-01

78

Casein-coated iron oxide nanoparticles for high MRI contrast enhancement and efficient cell targeting.  

PubMed

Surface properties, as well as inherent physicochemical properties, of the engineered nanomaterials play important roles in their interactions with the biological systems, which eventually affect their efficiency in diagnostic and therapeutic applications. Here we report a new class of MRI contrast agent based on milk casein protein-coated iron oxide nanoparticles (CNIOs) with a core size of 15 nm and hydrodynamic diameter ~30 nm. These CNIOs exhibited excellent water-solubility, colloidal stability, and biocompatibility. Importantly, CNIOs exhibited prominent T2 enhancing capability with a transverse relaxivity r2 of 273 mM(-1) s(-1) at 3 tesla. The transverse relaxivity is ~2.5-fold higher than that of iron oxide nanoparticles with the same core but an amphiphilic polymer coating. CNIOs showed pH-responsive properties, formed loose and soluble aggregates near the pI (pH ~4.0). The aggregates could be dissociated reversibly when the solution pH was adjusted away from the pI. The transverse relaxation property and MRI contrast enhancing effect of CNIOs remained unchanged in the pH range of 2.0-8.0. Further functionalization of CNIOs can be achieved via surface modification of the protein coating. Bioaffinitive ligands, such as a single chain fragment from the antibody of epidermal growth factor receptor (ScFvEGFR), could be readily conjugated onto the protein coating, enabling specific targeting to MDA-MB-231 breast cancer cells overexpressing EGFR. T2-weighted MRI of mice intravenously administered with CNIOs demonstrated strong contrast enhancement in the liver and spleen. These favorable properties suggest CNIOs as a class of biomarker targeted magnetic nanoparticles for MRI contrast enhancement and related biomedical applications. PMID:23633522

Huang, Jing; Wang, Liya; Lin, Run; Wang, Andrew Y; Yang, Lily; Kuang, Min; Qian, Weiping; Mao, Hui

2013-05-14

79

Targeted Multifunctional Nanoparticles cure and image Brain Tumors: Selective MRI Contrast Enhancement and Photodynamic Therapy  

Microsoft Academic Search

Aimed at targeted therapy and imaging of brain tumors, our approach uses targeted, multi-functional nano-particles (NP). A typical nano-particle contains a biologically inert, non-toxic matrix, biodegradable and bio-eliminable over a long time period. It also contains active components, such as fluorescent chemical indicators, photo-sensitizers, MRI contrast enhancement agents and optical imaging dyes. In addition, its surface contains molecular targeting units,

Raoul Kopelman

2008-01-01

80

Manganese-Enhanced MRI Reveals Structural and Functional Changes in the Cortex of Bassoon Mutant Mice  

Microsoft Academic Search

Manganese-enhanced magnetic resonance imaging (ME-MRI) was used to analyze the brain architecture in mice lacking the functional presynaptic active zone protein Bassoon. Anatomical characteriza- tion revealed a significant increase in the total brain volume in Bassoon mutants as compared with wild-type mice, which is mainly caused by changes in cortex and hippocampus volume. The measured enlargement in cortical volume coincides

Frank Angenstein; Heiko G. Niessen; J. Goldschmidt; H. Lison; W. D. Altrock; E. D. Gundelfinger; H. Scheich

2006-01-01

81

Multifunctional nanoparticle platforms for in vivo MRI enhancement and photodynamic therapy of a rat brain cancer  

NASA Astrophysics Data System (ADS)

A paradigm for brain cancer detection, treatment, and monitoring is established. Multifunctional biomedical nanoparticles (30 60 nm) containing photosensitizer externally deliver reactive oxygen species (ROS) to cancer cells while simultaneously enhancing magnetic resonance imaging (MRI) contrast providing real-time tumor kill measurement. Plasma residence time control and specific cell targeting are achieved. A 5 min treatment in rats halted and even reversed in vivo tumor growth after 3 4 days post-treatment.

Kopelman, Raoul; Lee Koo, Yong-Eun; Philbert, Martin; Moffat, Bradford A.; Ramachandra Reddy, G.; McConville, Patrick; Hall, Daniel E.; Chenevert, Thomas L.; Bhojani, Mahaveer Swaroop; Buck, Sarah M.; Rehemtulla, Alnawaz; Ross, Brian D.

2005-05-01

82

Oxygen-enhanced MRI in temporal lobe epilepsy: diagnosis and lateralization.  

PubMed

We explored the diagnostic value of oxygen-enhanced MRI, a novel technique for measuring regional brain metabolism, in a set of normal adult volunteers and temporal lobe epilepsy patients. Eight right-handed adult normal volunteers and ten right-handed patients with temporal lobe epilepsy were studied. Six patients had lesions concordant with their epilepsy on high-resolution (3T) structural MRI. Four patients were nonlesional. Hyperoxia (oxygen enhancement, OE) was carried out by administering 100% O(2) in epochs by mask or cannula interleaved with breathing of normal atmospheric air. The T2* (blood oxygen level dependent, BOLD) signal was recorded in continuously acquired echo-planar images. Data from nine temporal lobe subregions were subjected to spectral analysis and statistical testing. OE resulted in unambiguous concordant positive T2* signal change in all subjects. Analysis of the distribution of spectral power within the temporal lobe revealed a significant (p<0.025, one-sided) group difference between normals and epilepsy patients, with seven patients exhibiting large deviations from normalcy that lateralized their disease. Two such patients had nonlesional MRIs. Oxygen-enhanced MRI is a promising metabolic imaging modality for the diagnosis and lateralization of oxidative metabolic derangement associated with lesional and nonlesional temporal lobe epilepsy. PMID:21917423

Kalamangalam, Giridhar P; Nelson, Jeffrey T; Ellmore, Timothy M; Narayana, Ponnada A

2011-09-13

83

Contrast-enhanced ultra-high-field liver MRI: a feasibility trial.  

PubMed

The aim of this study was to investigate the feasibility of dynamic contrast-enhanced 7 T MRI of the liver using an eight-channel radiofrequency (RF) transmit/receive body-coil. 16 healthy subjects were examined on a 7 T MR system utilizing a custom-built eight-channel RF body-coil suitable for RF-shimming. The following data were acquired: (1) steady state free precession imaging, (2) T2w turbo spin echo imaging, (3) T1w in and opposed-phase imaging, (4) T1w 3D FLASH images pre-contrast and in arterial, portal-venous and venous phase and (5) a fat-saturated pre- and post-contrast 2D FLASH sequence. Visual evaluation of (1) the delineation of liver vasculature, (2) the overall image quality, and (3) artifact presence and consequent image impairment was performed. SNR of the liver parenchyma was measured for the contrast-enhanced 2D and 3D FLASH sequences. For statistical analysis, a Wilcoxon-Rank Test was used. Best delineation of non-enhanced liver vasculature and overall image quality was found for 2D FLASH MRI, with only slight improvement in vessel conspicuity after the application of contrast media. T2-weighted TSE imaging remained strongly impaired, falling short of diagnostic relevance and precluding a clinical application. Our results demonstrate the feasibility and diagnostic potential of dedicated contrast-enhanced 7 T liver MRI as well as the potential for non-contrast-enhanced angiographic application. PMID:21862273

Umutlu, Lale; Bitz, Andreas K; Maderwald, Stefan; Orzada, Stephan; Kinner, Sonja; Kraff, Oliver; Brote, Irina; Ladd, Susanne C; Schroeder, Tobias; Forsting, Michael; Antoch, Gerald; Ladd, Mark E; Quick, Harald H; Lauenstein, Thomas C

2011-08-20

84

Concurrent MRI and diffuse optical tomography of breast after indocyanine green enhancement  

PubMed Central

We present quantitative optical images of human breast in vivo. The images were obtained by using near-infrared diffuse optical tomography (DOT) after the administration of indocyanine green (ICG) for contrast enhancement. The optical examination was performed concurrently with a magnetic resonance imaging (MRI) exam on patients scheduled for excisional biopsy or surgery so that accurate image coregistration and histopathological information of the suspicious lesions was available. The ICG-enhanced optical images coregistered accurately with Gadolinium-enhanced magnetic resonance images validating the ability of DOT to image breast tissue. In contrast to simple transillumination, we found that DOT provides for localization and quantification of exogenous tissue chromophore concentrations. Additionally our use of ICG, an albumin bound absorbing dye in plasma, demonstrates the potential to differentiate disease based on the quantified enhancement of suspicious lesions.

Ntziachristos, Vasilis; Yodh, A. G.; Schnall, Mitchell; Chance, Britton

2000-01-01

85

The suppression of repetition enhancement: a review of fMRI studies.  

PubMed

Repetition suppression in fMRI studies is generally thought to underlie behavioural facilitation effects (i.e., priming) and it is often used to identify the neuronal representations associated with a stimulus. However, this pays little heed to the large number of repetition enhancement effects observed under similar conditions. In this review, we identify several cognitive variables biasing repetition effects in the BOLD response towards enhancement instead of suppression. These variables are stimulus recognition, learning, attention, expectation and explicit memory. We also evaluate which models can account for these repetition effects and come to the conclusion that there is no one single model that is able to embrace all repetition enhancement effects. Accumulation, novel network formation as well as predictive coding models can all explain subsets of repetition enhancement effects. PMID:23159344

Segaert, Katrien; Weber, Kirsten; de Lange, Floris P; Petersson, Karl Magnus; Hagoort, Peter

2012-11-14

86

Default-mode network activity distinguishes amnestic type mild cognitive impairment from healthy aging: A combined structural and resting-state functional MRI study  

Microsoft Academic Search

Resting-state functional magnetic resonance imaging (MRI), have revealed coactivation in a distributed network that characterizes the default-mode in the human brain. However, details from resting-state imaging in amnestic type mild cognitive impairment (aMCI) is poorly understand. Regional homogeneity, which characterizes low-frequency blood oxygenation level dependent fluctuation, after statistically controlling for the regional atrophy and age in resting-state, were examined and

Feng Bai; Zhijun Zhang; Hui Yu; Yongmei Shi; Yonggui Yuan; Wanlin Zhu; Xiangrong Zhang; Yun Qian

2008-01-01

87

Simultaneous imaging of tumor oxygenation and microvascular permeability using Overhauser enhanced MRI  

PubMed Central

Architectural and functional abnormalities of blood vessels are a common feature in tumors. A consequence of increased vascular permeability and concomitant aberrant blood flow is poor delivery of oxygen and drugs, which is associated with treatment resistance. In the present study, we describe a strategy to simultaneously visualize tissue oxygen concentration and microvascular permeability by using a hyperpolarized 1H-MRI, known as Overhauser enhanced MRI (OMRI), and an oxygen-sensitive contrast agent OX63. Substantial MRI signal enhancement was induced by dynamic nuclear polarization (DNP). The DNP achieved up to a 7,000% increase in MRI signal at an OX63 concentration of 1.5 mM compared with that under thermal equilibrium state. The extent of hyperpolarization is influenced mainly by the local concentration of OX63 and inversely by the tissue oxygen level. By collecting dynamic OMRI images at different hyperpolarization levels, local oxygen concentration and microvascular permeability of OX63 can be simultaneously determined. Application of this modality to murine tumors revealed that tumor regions with high vascular permeability were spatio-temporally coincident with hypoxia. Quantitative analysis of image data from individual animals showed an inverse correlation between tumor vascular leakage and median oxygen concentration. Immunohistochemical analyses of tumor tissues obtained from the same animals after OMRI experiments demonstrated that lack of integrity in tumor blood vessels was associated with increased tumor microvascular permeability. This dual imaging technique may be useful for the longitudinal assessment of changes in tumor vascular function and oxygenation in response to chemotherapy, radiotherapy, or antiangiogenic treatment.

Matsumoto, Shingo; Yasui, Hironobu; Batra, Sonny; Kinoshita, Yuichi; Bernardo, Marcelino; Munasinghe, Jeeva P.; Utsumi, Hideo; Choudhuri, Rajani; Devasahayam, Nallathamby; Subramanian, Sankaran; Mitchell, James B.; Krishna, Murali C.

2009-01-01

88

Quantitative MRI of colonic mural enhancement: segmental differences exist in endoscopically proven normal colon  

PubMed Central

Objectives Abnormal contrast enhancement on MRI is advocated as a biomarker for inflammation in colitis, although the enhancement kinetics of normal colon are poorly described. Our purpose was to quantitatively assess mural enhancement in normal colon and test for intersegmental differences. Methods Eight patients without prior history of inflammatory bowel disease underwent standard MRI colonography followed by normal same-day colonoscopy. Acquired sequences included a volumetric interpolated breath-hold examination (VIBE) to encompass the whole colonic volume, performed at 5°, 10° and 35° flip angles for T1 quantitation and then at a fixed 35° flip angle three times prior to and every 30 s following intravenous gadoterate meglumine for 220 s. Ascending colon, descending colon and rectal R1 (1/T1) was plotted against time. Mean pre-contrast R1, initial change of R1 (?R1), early and late “plateau phase” enhancement and the area under the R1–time (AUC–R1) curve were compared between segments using the Student's paired t-test. Results There was no significant difference of pre-contrast R1 between segments (p=0.49 to 0.62). ?R1 was higher for ascending colon compared with descending colon (0.0023±0.0012 ms?1 vs 0.0010±0.0011 ms?1, p=0.03). There was no significant difference for early or late plateau phase R1 between colonic segments (p=0.08 to 1.00). AUC–R1 was greater for ascending than descending colon (0.54±0.19 vs 0.30±0.14, p=0.03). Conclusions Intersegmental differences in colonic enhancement are present and should be considered when interpreting differential segmental enhancement.

Punwani, S; Hafeez, R; Bainbridge, A; Boulos, P; Halligan, S; Bloom, S; Taylor, S A

2012-01-01

89

Mapping Tumor Hypoxia In Vivo Using Pattern Recognition of Dynamic Contrast-enhanced MRI Data12  

PubMed Central

In solid tumors, hypoxia contributes significantly to radiation and chemotherapy resistance and to poor outcomes. The “gold standard” pO2 electrode measurements of hypoxia in vivo are unsatisfactory because they are invasive and have limited spatial coverage. Here, we present an approach to identify areas of tumor hypoxia using the signal versus time curves of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) data as a surrogate marker of hypoxia. We apply an unsupervised pattern recognition (PR) technique to determine the differential signal versus time curves associated with different tumor microenvironmental characteristics in DCE-MRI data of a preclinical cancer model. Well-perfused tumor areas are identified by rapid contrast uptake followed by rapid washout; hypoxic areas, which are regions of reduced vascularization, are identified by delayed contrast signal buildup and washout; and necrotic areas exhibit slow or no contrast uptake and no discernible washout over the experimental observation. The strength of the PR concept is that it captures the pixel-enhancing behavior in its entirety—during both contrast agent uptake and washout—and thus, subtleties in the temporal behavior of contrast enhancement related to features of the tumor microenvironment (driven by vascular changes) may be detected. The assignment of the tumor compartments/microenvironment to well vascularized, hypoxic, and necrotic is validated by comparison to data previously obtained using complementary imaging modalities. The proposed novel analysis approach has the advantage that it can be readily translated to the clinic, as DCE-MRI is used routinely for the identification of tumors in patients, is widely available, and easily implemented on any clinical magnet.

Stoyanova, Radka; Huang, Kris; Sandler, Kiri; Cho, HyungJoon; Carlin, Sean; Zanzonico, Pat B; Koutcher, Jason A; Ackerstaff, Ellen

2012-01-01

90

In Vivo Detection of Individual Glomeruli in the Rodent Olfactory Bulb Using Manganese Enhanced MRI  

PubMed Central

MRI contrast based on relaxation times, proton density, or signal phase have been applied to delineate neural structures in the brain. However, neural units such as cortical layers and columns have been difficult to identify using these methods. Manganese ion delivered either systemically or injected directly has been shown to accumulate specifically within cellular areas of the brain enabling the differentiation of layers within the hippocampus, cortex, cerebellum, and olfactory bulb in vivo. Here we show the ability to detect individual olfactory glomeruli using manganese enhanced MRI (MEMRI). Glomeruli are anatomically distinct structures (~150 ?m in diameter) on the surface of the olfactory bulb that represent the first processing units for olfactory sensory information. Following systemic delivery of MnCl2 we used 3D-MRI with 50?m isotropic resolution to detect discrete spots of increased signal intensity between 100–200 ?m in diameter in the glomerular layer of the rat olfactory bulb. Inflow effects of arterial blood and susceptibility effects of venous blood were suppressed and were evaluated by comparing the location of vessels in the bulb to areas of manganese enhancement using iron oxide to increase vessel contrast. These potential vascular effects did not explain the contrast detected. Nissl staining of individual glomeruli were also compared to MEMRI images from the same animals clearly demonstrating that many of the manganese enhanced regions corresponded to individual olfactory glomeruli. Thus, MEMRI can be used as a non-invasive means to detect olfactory glomeruli for longitudinal studies looking at neural plasticity during olfactory development or possible degeneration associated with disease.

Chuang, Kai-Hsiang; Belluscio, Leonardo; Koretsky, Alan P.

2009-01-01

91

Visualization of thermal ablation lesions using cumulative dynamic contrast enhancement MRI  

NASA Astrophysics Data System (ADS)

A novel robust and user friendly method for post-processing dynamic contrast enhanced (DCE) MRI data is presented, which provides reliable real-time delineation of the borders of thermal ablation lesions on low SNR images shortly after contrast agent injection without any model-based curve fitting. Some simple descriptors of the DCE process are calculated in a time efficient recursive manner and combined into a single image reflecting both current and previous enhancement states of each pixel, which allows robust discrimination between tissue areas with different perfusion properties. The resulting cumulative DCE (CDCE) images are shown to exhibit a strong correlation with histopathology and late gadolinium enhancement representations of the thermal damage in soft tissue. It is shown that the outer border of the non-perfused ablation lesion core on CDCE MRI corresponds to the histopathological lesion border. The described method has a potential not only to facilitate thermal ablation outcome assessment, but also to improve detection of infiltrative tumours and reduce the administered contrast agent dose in any DCE scans.

Shmatukha, Andriy; Sethi, Benu; Shurrab, Mohammed; Ghate, Sudip; Qi, Xiuling; Barry, Jennifer; Wright, Graham; Crystal, Eugene

2013-05-01

92

Quantifying heterogeneity of lesion uptake in dynamic contrast enhanced MRI for breast cancer diagnosis  

NASA Astrophysics Data System (ADS)

The current study investigates whether texture features extracted from lesion kinetics feature maps can be used for breast cancer diagnosis. Fifty five women with 57 breast lesions (27 benign, 30 malignant) were subjected to dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) on 1.5T system. A linear-slope model was fitted pixel-wise to a representative lesion slice time series and fitted parameters were used to create three kinetic maps (wash out, time to peak enhancement and peak enhancement). 28 grey level co-occurrence matrices features were extracted from each lesion kinetic map. The ability of texture features per map in discriminating malignant from benign lesions was investigated using a Probabilistic Neural Network classifier. Additional classification was performed by combining classification outputs of most discriminating feature subsets from the three maps, via majority voting. The combined scheme outperformed classification based on individual maps achieving area under Receiver Operating Characteristics curve 0.960±0.029. Results suggest that heterogeneity of breast lesion kinetics, as quantified by texture analysis, may contribute to computer assisted tissue characterization in DCE-MRI.

Karahaliou, A.; Vassiou, K.; Skiadopoulos, S.; Kanavou, T.; Yiakoumelos, A.; Costaridou, L.

2009-07-01

93

MRI edge enhancement as a diffusive discord of spin phase structure.  

PubMed

The enhancement of magnetic resonance image intensity near impermeable boundaries can be nicely described by a new approach where the diffusional spin echo attenuation is linked to the correlation function of molecular motion. In this method the spin phase structure created by the applied gradient is considered to be a composition of plane waves with the wave vectors representing feasible momentum states of a particle in confinement. The enhancement of edges on the magnetic resonance images (MRI) comes out as a discord of plane waves due to particle motion. It results from the average of the wave phase by using the cumulant expansion in the Gaussian approximation. The acquired analytical expression describes the MRI signal space distribution where the enhancement of edges depends on the intensity and the duration of gradient sequence as well as on the length of the mean squared particle displacement in restricted geometry. This new method works well with gradients of general waveform and is, therefore, suitable for imaging sequences where finite or even modulated gradients are usually used. PMID:10053144

Stepisnik, J; Duh, A; Mohoric, A; Sersa, I

1999-03-01

94

Visualization of thermal ablation lesions using cumulative dynamic contrast enhancement MRI.  

PubMed

A novel robust and user friendly method for post-processing dynamic contrast enhanced (DCE) MRI data is presented, which provides reliable real-time delineation of the borders of thermal ablation lesions on low SNR images shortly after contrast agent injection without any model-based curve fitting. Some simple descriptors of the DCE process are calculated in a time efficient recursive manner and combined into a single image reflecting both current and previous enhancement states of each pixel, which allows robust discrimination between tissue areas with different perfusion properties. The resulting cumulative DCE (CDCE) images are shown to exhibit a strong correlation with histopathology and late gadolinium enhancement representations of the thermal damage in soft tissue. It is shown that the outer border of the non-perfused ablation lesion core on CDCE MRI corresponds to the histopathological lesion border. The described method has a potential not only to facilitate thermal ablation outcome assessment, but also to improve detection of infiltrative tumours and reduce the administered contrast agent dose in any DCE scans. PMID:23615319

Shmatukha, Andriy; Sethi, Benu; Shurrab, Mohammed; Ghate, Sudip; Qi, Xiuling; Barry, Jennifer; Wright, Graham; Crystal, Eugene

2013-04-25

95

The effect of motion correction on pharmacokinetic parameter estimation in dynamic-contrast-enhanced MRI  

NASA Astrophysics Data System (ADS)

A dynamic-contrast-enhanced magnetic resonance imaging (DCE-MRI) dataset consists of many imaging frames, often acquired both before and after contrast injection. Due to the length of time spent acquiring images, patient motion is likely and image re-alignment or registration is required before further analysis such as pharmacokinetic model fitting. Non-rigid image registration procedures may be used to correct motion artefacts; however, a careful choice of registration strategy is required to reduce misregistration artefacts associated with enhancing features. This work investigates the effect of registration on the results of model-fitting algorithms for 52 DCE-MR mammography cases for 14 patients. Results are divided into two sections: a comparison of registration strategies in which a DCE-MRI-specific algorithm is preferred in 50% of cases, followed by an investigation of parameter changes with known applied deformations, inspecting the effect of magnitude and timing of motion artefacts. Increased motion magnitude correlates with increased model-fit residual and is seen to have a strong influence on the visibility of strongly enhancing features. Motion artefacts in images close to the contrast agent arrival have a disproportionate effect on discrepancies in parameter estimation. The choice of algorithm, magnitude of motion and timing of the motion are each shown to influence estimated pharmacokinetic parameters even when motion magnitude is small.

Melbourne, A.; Hipwell, J.; Modat, M.; Mertzanidou, T.; Huisman, H.; Ourselin, S.; Hawkes, D. J.

2011-12-01

96

Dynamic-contrast-enhanced-MRI with extravasating contrast reagent: rat cerebral glioma blood volume determination.  

PubMed

The accurate mapping of the tumor blood volume (TBV) fraction (vb) is a highly desired imaging biometric goal. It is commonly thought that achieving this is difficult, if not impossible, when small molecule contrast reagents (CRs) are used for the T1-weighted (Dynamic-Contrast-Enhanced) DCE-MRI technique. This is because angiogenic malignant tumor vessels allow facile CR extravasation. Here, a three-site equilibrium water exchange model is applied to DCE-MRI data from the cerebrally-implanted rat brain U87 glioma, a tumor exhibiting rapid CR extravasation. Analyses of segments of the (and the entire) DCE data time-course with this "shutter-speed" pharmacokinetic model, which admits finite water exchange kinetics, allow TBV estimation from the first-pass segment. Pairwise parameter determinances were tested with grid searches of 2D parametric error surfaces. Tumor blood volume (vb), as well as ve (the extracellular, extravascular space volume fraction), and Ktrans (a CR extravasation rate measure) parametric maps are presented. The role of the Patlak Plot in DCE-MRI is also considered. PMID:20674422

Li, Xin; Rooney, William D; Várallyay, Csanád G; Gahramanov, Seymur; Muldoon, Leslie L; Goodman, James A; Tagge, Ian J; Selzer, Audrey H; Pike, Martin M; Neuwelt, Edward A; Springer, Charles S

2010-07-31

97

Brain-wide pathway for waste clearance captured by contrast-enhanced MRI.  

PubMed

The glymphatic system is a recently defined brain-wide paravascular pathway for cerebrospinal fluid (CSF) and interstitial fluid (ISF) exchange that facilitates efficient clearance of solutes and waste from the brain. CSF enters the brain along para-arterial channels to exchange with ISF, which is in turn cleared from the brain along para-venous pathways. Because soluble amyloid ? clearance depends on glymphatic pathway function, we proposed that failure of this clearance system contributes to amyloid plaque deposition and Alzheimer's disease progression. Here we provide proof of concept that glymphatic pathway function can be measured using a clinically relevant imaging technique. Dynamic contrast-enhanced MRI was used to visualize CSF-ISF exchange across the rat brain following intrathecal paramagnetic contrast agent administration. Key features of glymphatic pathway function were confirmed, including visualization of para-arterial CSF influx and molecular size-dependent CSF-ISF exchange. Whole-brain imaging allowed the identification of two key influx nodes at the pituitary and pineal gland recesses, while dynamic MRI permitted the definition of simple kinetic parameters to characterize glymphatic CSF-ISF exchange and solute clearance from the brain. We propose that this MRI approach may provide the basis for a wholly new strategy to evaluate Alzheimer's disease susceptibility and progression in the live human brain. PMID:23434588

Iliff, Jeffrey J; Lee, Hedok; Yu, Mei; Feng, Tian; Logan, Jean; Nedergaard, Maiken; Benveniste, Helene

2013-02-22

98

Dynamic-contrast-enhanced-MRI with extravasating contrast reagent: Rat cerebral glioma blood volume determination  

NASA Astrophysics Data System (ADS)

The accurate mapping of the tumor blood volume (TBV) fraction (vb) is a highly desired imaging biometric goal. It is commonly thought that achieving this is difficult, if not impossible, when small molecule contrast reagents (CRs) are used for the T1-weighted (Dynamic-Contrast-Enhanced) DCE-MRI technique. This is because angiogenic malignant tumor vessels allow facile CR extravasation. Here, a three-site equilibrium water exchange model is applied to DCE-MRI data from the cerebrally-implanted rat brain U87 glioma, a tumor exhibiting rapid CR extravasation. Analyses of segments of the (and the entire) DCE data time-course with this “shutter-speed” pharmacokinetic model, which admits finite water exchange kinetics, allow TBV estimation from the first-pass segment. Pairwise parameter determinances were tested with grid searches of 2D parametric error surfaces. Tumor blood volume (vb), as well as ve (the extracellular, extravascular space volume fraction), and Ktrans (a CR extravasation rate measure) parametric maps are presented. The role of the Patlak Plot in DCE-MRI is also considered.

Li, Xin; Rooney, William D.; Várallyay, Csanád G.; Gahramanov, Seymur; Muldoon, Leslie L.; Goodman, James A.; Tagge, Ian J.; Selzer, Audrey H.; Pike, Martin M.; Neuwelt, Edward A.; Springer, Charles S.

2010-10-01

99

Brain-wide pathway for waste clearance captured by contrast-enhanced MRI  

PubMed Central

The glymphatic system is a recently defined brain-wide paravascular pathway for cerebrospinal fluid (CSF) and interstitial fluid (ISF) exchange that facilitates efficient clearance of solutes and waste from the brain. CSF enters the brain along para-arterial channels to exchange with ISF, which is in turn cleared from the brain along para-venous pathways. Because soluble amyloid ? clearance depends on glymphatic pathway function, we proposed that failure of this clearance system contributes to amyloid plaque deposition and Alzheimer’s disease progression. Here we provide proof of concept that glymphatic pathway function can be measured using a clinically relevant imaging technique. Dynamic contrast-enhanced MRI was used to visualize CSF-ISF exchange across the rat brain following intrathecal paramagnetic contrast agent administration. Key features of glymphatic pathway function were confirmed, including visualization of para-arterial CSF influx and molecular size-dependent CSF-ISF exchange. Whole-brain imaging allowed the identification of two key influx nodes at the pituitary and pineal gland recesses, while dynamic MRI permitted the definition of simple kinetic parameters to characterize glymphatic CSF-ISF exchange and solute clearance from the brain. We propose that this MRI approach may provide the basis for a wholly new strategy to evaluate Alzheimer’s disease susceptibility and progression in the live human brain.

Iliff, Jeffrey J.; Lee, Hedok; Yu, Mei; Feng, Tian; Logan, Jean; Nedergaard, Maiken; Benveniste, Helene

2013-01-01

100

Convection-enhanced delivery of maghemite nanoparticles: Increased efficacy and MRI monitoring.  

PubMed

Convection-enhanced drug delivery (CED) is a novel approach to delivering drugs into brain tissue. Drugs are delivered continuously via a catheter, enabling large volume distributions of high drug concentrations with minimum systemic toxicity. Previously we demonstrated that CED formation/extent of small molecules may be significantly improved by increasing infusate viscosities. In this study we show that the same methodology can be applied to monodispersed maghemite nanoparticles (MNPs). For this purpose we used a normal rat brain model and performed CED of MNPs over short infusion times. By adding 3% sucrose or 3%-6% polyethylene glycol (PEG; molecular weight 400) to saline containing pristine MNPs, we increased infusate viscosity and obtained increased CED efficacy. Further, we show that CED of dextran-coated MNPs (dextran-MNPs) resulted in increased efficacy over pristine MNPs (p < 0.007). To establish the use of MRI for reliable depiction of MNP distribution, CED of fluorescent dextran-MNPs was performed, demonstrating a significant correlation between the distributions as depicted by MRI and spectroscopic images (r(2) = 0.74, p < 0.0002). MRI follow-up showed that approximately 80%-90% of the dextran-MNPs were cleared from the rat brain within 40 days of CED; the rest remained in the brain for more than 4 months. MNPs have been tested for applications such as targeted drug delivery and controlled drug release and are clinically used as a contrast agent for MRI. Thus, combining the CED method with the advantages of MNPs may provide a powerful tool to treat and monitor brain tumors. PMID:18316474

Perlstein, Benny; Ram, Zvi; Daniels, Dianne; Ocherashvilli, Aharon; Roth, Yiftach; Margel, Shlomo; Mardor, Yael

2008-03-03

101

Quantitative assessment of intervertebral disc glycosaminoglycan distribution by gadolinium-enhanced MRI in orthopedic patients.  

PubMed

Our hypothesis was that the enhanced MRI of cartilage (dGEMRIC) imaging protocol could be used in patients to quantify the sulfated glycosaminoglycan (sGAG) in intervertebral discs (IVD). To test this hypothesis, 23 patients with degenerative disc pathology scheduled for surgery were studied by a specific dGEMRIC protocol: each patient underwent two MRI scans, before and 3.5 hr after Gd(DTPA)2-injection of a nonconventional dose of 40 mL. Then, T(1PRE-ENH) and T(1POST-ENH) parametric images of the disc were obtained, from which a new index DeltaT(1) of the molecular status of the IVD was computed (T(1PRE-ENH) - T(1POST-ENH)). A total of 31 tissue samples (one or two from each patient) obtained at herniectomy were collected and biochemically analyzed for sGAG content and used as the gold standard for comparison. DeltaT(1) values in correspondence to degenerated sectors were higher (158 +/- 36 ms) compared to normal sectors (80 +/- 13 ms). Linear regression analysis between MRI-derived and biochemistry-derived measurements resulted in a significant correlation (r = 0.73, P < 0.0001). The DeltaT(1) parametric images, calculated using the modified dGEMRIC technique, provided noninvasive quantitative information about sGAG content within discal tissue in vivo, which resulted in agreement with biochemical analysis. The application of this new MRI method could provide diagnostic information for standard treatment of lumbar discopathy and for innovative therapies of regenerative medicine. PMID:18050346

Vaga, Stefania; Raimondi, Manuela Teresa; Caiani, Enrico Gianluca; Costa, Francesco; Giordano, Carmen; Perona, Franco; Zerbi, Alberto; Fornari, Maurizio

2008-01-01

102

MRI Enhancement in Stromal Tissue Surrounding Breast Tumors: Association with Recurrence Free Survival following Neoadjuvant Chemotherapy  

PubMed Central

Rationale and Objectives Normal-appearing stromal tissues surrounding breast tumors can harbor abnormalities that lead to increased risk of local recurrence. The objective of this study was to develop a new imaging methodology to characterize the signal patterns of stromal tissue and to investigate their association with recurrence-free survival following neoadjuvant chemotherapy. Materials and Methods Fifty patients with locally-advanced breast cancer were imaged with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) before (V1) and after one cycle (V2) of adriamycin-cytoxan therapy. Contrast enhancement in normal-appearing stroma around the tumor was characterized by the mean percent enhancement (PE) and mean signal enhancement ratio (SER) in distance bands of 5 mm from the tumor edge. Global PE and SER were calculated by averaging all stromal bands 5 to 40 mm from tumor. Proximity-dependent PE and SER were analyzed using a linear mixed effects model and Cox proportional hazards model for recurrence-free survival. Results The mixed effects model displayed a decreasing radial trend in PE at both V1 and V2. An increasing trend was less pronounced in SER. Survival analysis showed that the hazard ratio estimates for each unit decrease in global SER was statistically significant at V1 [estimated hazard ratio?=?0.058, 95% Wald CI (0.003, 1.01), likelihood ratio p?=?0.03]; but was not so for V2. Conclusions These findings show that stromal tissue outside the tumor can be quantitatively characterized by DCE-MRI, and suggest that stromal enhancement measurements may be further developed for use as a potential predictor of recurrence/disease-free survival following therapy.

Jones, Ella F.; Sinha, Sumedha P.; Newitt, David C.; Klifa, Catherine; Kornak, John

2013-01-01

103

Correlation of late gadolinium enhancement MRI and quantitative T2 measurement in cardiac sarcoidosis.  

PubMed

PURPOSE: To investigate the potentially improved detection and quantification of cardiac involvement using novel late-gadolinium-enhancement (LGE) cardiac magnetic resonance imaging (MRI) and quantitative T2 measurement to achieve better myocardial tissue characterization in systemic sarcoidosis. MATERIALS AND METHODS: Twenty-eight patients with systemic sarcoidosis underwent a cardiac magnetic resonance imaging (CMR) study on a 1.5T system. Precontrast CMR included left ventricular (LV) and right ventricular (RV) function and quantitative T2 measurement. Postcontrast LGE-MRI included inversion-recovery fast-gradient-echo (IR-FGRE) and multicontrast late-enhancement imaging (MCLE). RESULTS: LV functional parameters were normal in all patients (LVEF?=?61.2?±?8.5%) including with cardiac involvement (LVEF?=?59.4?±?12.1%) and without (LVEF?=?61.7?±?7.5%) while the average RV function was comparatively decreased (RVEF?=?48.0?±?6.6%, P?MRI can identify cardiac involvement in systemic sarcoidosis. MCLE might be more sensitive at detecting subtle myocardial lesion. The decreased T2 observed in cardiac sarcoid may reflect its inactive phase, thus might provide a noninvasive method for monitoring disease activity or therapy.J. Magn. Reson. Imaging 2013;00:000-000. © 2013 Wiley Periodicals, Inc. PMID:23720077

Yang, Yuesong; Safka, Katherine; Graham, John J; Roifman, Idan; Zia, Mohammad I; Wright, Graham A; Balter, Meyer; Dick, Alexander J; Connelly, Kim A

2013-05-29

104

Acute effects of pelvic irradiation on the adult uterus revealed by dynamic contrast-enhanced MRI.  

PubMed

Objective: Pelvic radiation therapy (RT) can influence fertility in female rectal cancer survivors. Data regarding its effects on the adult uterus are scant. This study aims to evaluate the uterus before and after RT, using dynamic contrast-enhanced MRI. Methods: Eligible patients (n=10) received RT for rectal cancer, had an intact uterus and underwent dynamic contrast-enhanced MRI before and after RT. Seven patients were pre-menopausal. Results: Patients received pelvic RT (median, 50.2?Gy) with concurrent 5-fluorouracil. Five patients were treated with intensity modulated RT (IMRT) and five with a three-field technique. The median D95 of the uterus was 30?Gy; D05 was 48?Gy; and V95 was 97%. The median cervical D95 was 45?Gy; D05, 50?Gy; and V95, 100%. Cervical dose was higher with IMRT than with three-field plans (p?0.038). On T2 MRI, the junctional zone was visible in nine patients before and in one after RT (p=0.001). Median cervical length (2.3 vs 3.0?cm) and endometrial thickness (2.6 vs 5.9?mm) were reduced after RT (p?0.008). In pre-menopausal patients, the volume transfer constant, Ktrans, (0.069 vs 0.195, p=0.006) and the extracellular extravascular volume fraction, Ve, (0.217 vs 0.520, p=0.053) decreased. Conclusion: Pelvic RT significantly affected uterine anatomy and perfusion. Cervical dose was higher with IMRT than three-field plans, but no attempt was made to constrain the dose. Advances in knowledge: Pelvic RT significantly affects the adult uterus. These findings are crucial to understand the potential consequences of RT on fertility, and they lay the groundwork for further prospective studies. PMID:24052311

Milgrom, S A; Alberto Vargas, H; Sala, E; Frankel Kelvin, J; Hricak, H; Goodman, K A

2013-09-19

105

Manganese Enhanced MRI Reveals Functional Circuitry in Response to Odorant Stimuli  

PubMed Central

To investigate the circuitry involved in detecting odorants in the rodent brain, we developed a method using manganese-enhanced MRI (MEMRI) to map the flow of neural information from the olfactory sensory neurons (OSNs) to the central layers of the olfactory bulb. Studies have shown that Mn2+ enters active neurons and is transported anterogradely to axon terminals where it can cross synapses to functionally trace neural networks. Thus, by delivering MnCl2 directly into the nasal cavity of mice and then exposing them to defined odorants, Mn2+ is preferentially taken up by activated OSNs. Using the time course of the MRI signal, we generated maps of Mn2+ accumulation in the olfactory bulb for both glomerular and mitral cell layers. Results demonstrated that overlapping yet distinct enhancement patterns were produced by exposure to either octanal, acetophenone, or carvone. Notably, areas of Mn2+ accumulation in the mitral cell layer were similar to those in the glomerular layer consistent with neural information that passes from specific OSNs to specific mitral cells. Finally, by correlating specific Mn2+ signal peaks to genetically labeled glomeruli that are known to be activated by the odorant octanal, we show that MEMRI maps can be resolved at the level of individual glomeruli.

Chuang, Kai-Hsiang; Lee, Jung Hee; Silva, Afonso C.; Belluscio, Leonardo; Koretsky, Alan P.

2008-01-01

106

Manganese-Enhanced MRI Reveals Multiple Cellular and Vascular Layers in Normal and Degenerated Retinas  

PubMed Central

Purpose To use manganese-enhanced magnetic resonance imaging (MEMRI) at 25 × 25 × 800 ?m3 to image different retinal and vascular layers in the rat retinas. Materials and Methods Manganese-chloride was injected intraocularly in normal (n = 5) and Royal College of Surgeons (RCS, an model of photoreceptor degeneration) (n = 5) rats at postnatal day 90. MEMRI at 4.7 T was performed 24 hours later. MRI was repeated following intravenous Gd-DTPA in the same animals to highlight the vasculatures. Layer assignment and thickness were compared to histology. Results MEMRI 24 hours after intravitreal manganese-chloride injection revealed seven bands of alternating hyper- and hypointensities, corresponding histologically to the ganglion cell layer, inner plexiform layer, inner nuclear layer, outer plexiform layer, outer nuclear layer, photoreceptor-segment layer, and choroidal vascular layer. Intravenous Gd-DTPA—which does not cross the blood–retinal barrier and the retinal pigment epithelium—further enhanced the two layers bounding the retina, corresponding to the retinal and choroidal vascular layers, but not the avascular outer nuclear layer and the photoreceptor-segment layer. MEMRI of the RCS retinas revealed the loss of the outer plexiform layer, outer nuclear layer, and photoreceptor-segment layer. Histological analysis corroborated the MRI laminar assignments and thicknesses. Conclusion Lamina-specific retinal structures neurodegenerative changes to structure in retinal diseases can be detected using MEMRI.

Nair, Govind; Pardue, Machelle T.; Kim, Moon; Duong, Timothy Q.

2013-01-01

107

Monitoring radiation-induced changes in bone marrow histopathology with ultra-small superparamagnetic iron oxide (USPIO)-enhanced MRI.  

PubMed

The purpose of this study was to monitor radiation-induced alterations of the blood-bone marrow barrier (BMB) and the reticuloendothelial system (RES) with AMI-227-enhanced magnetic resonance imaging (MRI). Twenty New Zealand white rabbits (n = 10 following total body irradiation and n = 10 controls) underwent AMI-227-enhanced MRI. Pulse sequences included dynamic fast low-angle shot (FLASH; TR/TE 50/4 msec, flip angle 60 degrees) MRI and static T1- and T2-weighted spin-echo (SE) and turbo-SE sequences of the lumbar spine and sacrum. Bone marrow enhancement was quantified as delta signal intensity (SI) (%) =|[(SIpost - SIpre)/SIpre] x 100%| and compared with histopathology, including iron stains and electron microscopy. Dynamic bone marrow deltaSI (%) data steadily increased up to 10-15 minutes after AMI-227 administration, while blood deltaSI (%) data stayed nearly constant, histologically corresponding to iron oxide leakage into the bone marrow interstitium. This bone marrow contrast enhancement increased significantly following irradiation, corresponding to alterations of the endothelial lining of the bone marrow sinusoids. Late postcontrast images exhibited a significant positive T1 enhancement and negative T2 enhancement of the normal bone marrow, which further increased with irradiation due to increased RES activity. Irradiation-induced changes in bone marrow physiology could be reliably assessed with AMI-227-enhanced MRI. PMID:10331759

Daldrup, H E; Link, T M; Blasius, S; Strozyk, A; Könemann, S; Jürgens, H; Rummeny, E J

1999-05-01

108

Enhancement and suppression in a lexical interference fMRI-paradigm  

PubMed Central

Previous picture-word interference (PWI) fMRI-paradigms revealed ambiguous mechanisms underlying facilitation and inhibition in healthy subjects. Lexical distractors revealed increased (enhancement) or decreased (suppression) activation in language and monitoring/control areas. Performing a secondary examination and data analysis, we aimed to illuminate the relation between behavioral and neural interference effects comparing target-related distractors (REL) with unrelated distractors (UNREL). We hypothesized that interference involves both (A) suppression due to priming and (B) enhancement due to simultaneous distractor and target processing. Comparisons to UNREL should remain distractor unspecific even at a low threshold. (C) Distractor types with common characteristics should reveal overlapping brain areas. In a 3T MRI scanner, participants were asked to name pictures while auditory words were presented (stimulus onset asynchrony [SOA] = –200 msec). Associatively and phonologically related distractors speeded responses (facilitation), while categorically related distractors slowed them down (inhibition) compared to UNREL. As a result, (A) reduced brain activations indeed resembled previously reported patterns of neural priming. Each target-related distractor yielded suppressions at least in areas associated with vision and conflict/competition monitoring (anterior cingulate cortex [ACC]), revealing least priming for inhibitors. (B) Enhancements concerned language-related but distractor-unspecific regions. (C) Some wider brain regions were commonly suppressed for combinations of distractor types. Overlapping areas associated with conceptual priming were found for facilitatory distractors (inferior frontal gyri), and areas related to phonetic/articulatory processing (precentral gyri and left parietal operculum/insula) for distractors sharing feature overlap. Each distractor with semantic relatedness revealed nonoverlapping suppressions in lexical-phonological areas (superior temporal regions). To conclude, interference combines suppression of areas well known from neural priming and enhancement of language-related areas caused by dual activation from target and distractor. Differences between interference and priming need to be taken into account. The present interference paradigm has the potential to reveal the functioning of word-processing stages, cognitive control, and responsiveness to priming at the same time.

Abel, Stefanie; Dressel, Katharina; Weiller, Cornelius; Huber, Walter

2012-01-01

109

Calculation of intravascular signal in dynamic contrast enhanced-MRI using adaptive complex independent component analysis.  

PubMed

Assessing tumor response to therapy is a crucial step in personalized treatments. Pharmacokinetic (PK) modeling provides quantitative information about tumor perfusion and vascular permeability that are associated with prognostic factors. A fundamental step in most PK analyses is calculating the signal that is generated in the tumor vasculature. This signal is usually inseparable from the extravascular extracellular signal. It was shown previously using in vivo and phantom experiments that independent component analysis (ICA) is capable of calculating the intravascular time-intensity curve in dynamic contrast enhanced (DCE)-MRI. A novel adaptive complex independent component analysis (AC-ICA) technique is developed in this study to calculate the intravascular time-intensity curve and separate this signal from the DCE-MR images of tumors. The use of the complex-valued DCE-MRI images rather than the commonly used magnitude images satisfied the fundamental assumption of ICA, i.e., linear mixing of the sources. Using an adaptive cost function in ICA through estimating the probability distribution of the tumor vasculature at each iteration resulted in a more robust and accurate separation algorithm. The AC-ICA algorithm provided a better estimate for the intravascular time-intensity curve than the previous ICA-based method. A simulation study was also developed in this study to realistically simulate DCE-MRI data of a leaky tissue mimicking phantom. The passage of the MR contrast agent through the leaky phantom was modeled with finite element analysis using a diffusion model. Once the distribution of the contrast agent in the imaging field of view was calculated, DCE-MRI data was generated by solving the Bloch equation for each voxel at each time point. The intravascular time-intensity curve calculation results were compared to the previously proposed ICA-based intravascular time-intensity curve calculation method that applied ICA to the magnitude of the DCE-MRI data (Mag-ICA) using both simulated and experimental tissue mimicking phantoms. The AC-ICA demonstrated superior performance compared to the Mag-ICA method. AC-ICA provided more accurate estimate of intravascular time-intensity curve, having smaller error between the calculated and actual intravascular time-intensity curves compared to the Mag-ICA. Furthermore, it showed higher robustness in dealing with datasets with different resolution by providing smaller variation between the results of each datasets and having smaller difference between the intravascular time-intensity curves of various resolutions. Thus, AC-ICA has the potential to be used as the intravascular time-intensity curve calculation method in PK analysis and could lead to more accurate PK analysis for tumors. PMID:23247848

Mehrabian, Hatef; Chopra, Rajiv; Martel, Anne L

2012-12-12

110

Distinguishable neurofunctional effects of task practice and item practice in picture naming: A BOLD fMRI study in healthy subjects.  

PubMed

Practice of language tasks results in improved performance and BOLD signal changes. We distinguish changes correlated with repeated exposure to a picture naming task, from changes associated with naming specific items trained during practice. Task practice affected trained and untrained items, yielding left-sided BOLD deactivations in extrastriate, prefrontal and superior temporal areas (consistent with their putative role in perceptual priming, articulatory planning and phonological lexical retrieval, respectively). Item practice effects were restricted to trained words. There was deactivation in left posterior fusiform (supporting its role in accessing structural object representations), anterior cingulate and left insular/inferior frontal cortices (consistent with their role in processing low-frequency words). Central precuneus and posterior cingulate were hyperactivated (consistent with their putative role in episodic memory for trained items, probably due to functional connections with language areas). In healthy subjects, naming practice modifies stored linguistic representations, but mostly affects ease of access to trained words. PMID:23933470

Basso, Gianpaolo; Magon, Stefano; Reggiani, Francesca; Capasso, Rita; Monittola, Gianpiero; Yang, Fu-Ju; Miceli, Gabriele

2013-08-07

111

Differentiation of myeloma and metastatic cancer in the spine using dynamic contrast-enhanced MRI.  

PubMed

Spinal myeloma and metastatic cancer cause similar symptoms and show similar imaging presentations, thus making them difficult to differentiate. In this study, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was performed to differentiate between 9 myelomas and 22 metastatic cancers that present as focal lesions in the spine. The characteristic DCE parameters, including the peak signal enhancement percentage (SE%), the steepest wash-in SE% during the ascending phase and the wash-out SE%, were calculated by normalizing to the precontrast signal intensity. The two-compartmental pharmacokinetic model was used to obtain K(trans) and kep. All nine myelomas showed the wash-out DCE pattern. Of the 22 metastatic cancers, 12 showed wash-out, 7 showed plateau, and 3 showed persistent enhancing patterns. The fraction of cases that showed the wash-out pattern was significantly higher in the myeloma group than the metastatic cancer group (9/9=100% vs. 12/22=55%, P=.03). Compared to the metastatic cancer group, the myeloma group had a higher peak SE% (226%±72% vs. 165%±60%, P=.044), a higher steepest wash-in SE% (169%±51% vs. 111%±41%, P=.01), a higher K(trans) (0.114±0.036 vs. 0.077±0.0281/min, P=.016) and a higher kep (0.88±0.26 vs. 0.49±0.23 1/min, P=.002). The receiver operating characteristic analysis to differentiate between these two groups showed that the area under the curve was 0.798 for K(trans), 0.864 for kep and 0.919 for combined K(trans) and kep. These results show that DCE-MRI may provide additional information for making differential diagnosis to aid in choosing the optimal subsequent procedures or treatments for spinal lesions. PMID:23290477

Lang, Ning; Su, Min-Ying; Yu, Hon J; Lin, Muqing; Hamamura, Mark J; Yuan, Huishu

2013-01-03

112

Mn-citrate and Mn-HIDA: intermediate-affinity chelates for manganese-enhanced MRI.  

PubMed

In this study we investigated two manganese chelates in order to improve the image enhancement of manganese-enhanced MRI and decrease the toxicity of free manganese ions. Since both MnCl? and a low-affinity chelate were associated with a slow continuous decrease of cardiac functions, we investigated intermediate-affinity chelates: manganese N-(2-hydroxyethyl)iminodiacetic acid (Mn-HIDA) and Mn-citrate. The T? relaxivity values for Mn-citrate (4.4 m m?¹ s?¹) and Mn-HIDA (3.3 m m?¹ s?¹) in artificial cerebrospinal fluid (CSF) were almost constant in a concentration range from 0.5 to 5 m m at 37 °C and 4.7 T. In human plasma, the relaxivity values increased when the concentrations of these Mn chelates were decreased, suggesting the presence of free Mn²? bound with serum albumin. Mn-HIDA and Mn-citrate demonstrated a tendency for better contractility when employed with an isolated perfused frog heart, compared with MnCl?. Only minimal changes were demonstrated after a venous infusion of 100 m m Mn-citrate or Mn-HIDA (8.3 µmol kg?¹ min?¹) in rats and a constant heart rate, arterial pressure and sympathetic nerve activity were maintained, even after breaking the blood-brain barrier (BBB). Mn-citrate and Mn-HIDA could not cross the intact BBB and appeared in the CSF, and then diffused into the brain parenchyma through the ependymal layer. The responses in the supraoptic nucleus induced by the hypertonic stimulation were detectable. Therefore, Mn-citrate and Mn-HIDA appear to be better choices for maintaining the vital conditions of experimental animals, and they may improve the reproducibility of manganese-enhanced MRI of the small nuclei in the hypothalamus and thalamus. PMID:23281286

Seo, Yoshiteru; Satoh, Keitaro; Morita, Hironobu; Takamata, Akira; Watanabe, Kazuto; Ogino, Takashi; Hasebe, Tooru; Murakami, Masataka

113

Layer-Specific Manganese-Enhanced MRI of the Retina in Light and Dark Adaptation  

PubMed Central

Purpose. To employ functional manganese-enhanced MRI (MEMRI) to image layer-specific changes in calcium-dependent activities in the rat retina during light versus dark adaptation. Methods. Functional MEMRI at 20 × 20 × 700 ?m was used to study light and dark adaptation in the same animals (N = 10) in which one eye was covered and the fellow eye was not. The activity encoding of the light and dark adaptation was achieved in awake conditions and imaged under anesthesia. T1-weighted MRI at 11.7 tesla (T) was performed using two identical radiofrequency transceiver coils to allow interleaved MRI acquisitions of the two eyes. An intravascular contrast agent was also used to verify layer assignments. Results. MEMRI detected contrasts among the inner retina, outer retina, and choroid. Independent confirmation of the vascular layers and boundaries between layers was documented with an intravascular contrast agent. The retinal layer thicknesses agreed with published data. The outer retina had lower MEMRI activity in light compared with dark adaption (P < 0.001), consistent with the increased metabolic demand associated with the “dark current.” The inner retina had higher MEMRI activity in light compared with dark adaption (P < 0.05). The choroid MEMRI activity was not statistically different between light and dark adaptation (P > 0.05). Conclusions. This study demonstrated a high-resolution MEMRI protocol to image functional activities among different layers of the retinas in awake animals during light and dark adaptation. This approach could have potential applications in animal models of retinal dysfunction.

De La Garza, Bryan H.; Li, Guang; Shih, Yen-Yu I.; Duong, Timothy Q.

2012-01-01

114

Ferumoxytol enhanced resting state fMRI and relative cerebral blood volume mapping in normal human brain.  

PubMed

The brain demonstrates spontaneous low-frequency (<0.1Hz) cerebral blood flow (CBF) fluctuations, measurable by resting state functional MRI (rs-fMRI). Ultra small superparamagnetic iron oxide particles have been shown to enhance task-based fMRI signals (cerebral blood volume fMRI or CBV-fMRI), compared to the BOLD effect, by a factor of ?2.5 at 3T in primates and humans. We evaluated the use of ferumoxytol for steady state, resting state FMRI (CBV-rs-fMRI) and relative cerebral blood volume (rCBV) mapping, at 3T, in healthy volunteers. All standard resting state networks (RSNs) were identified in all subjects. On average the RSN Z statistics (MELODIC independent components) and volumes of the visual and default mode (DMN) networks were comparable. rCBV values were averaged for the visual (Vis) and DMN networks and correlated with the corresponding DMN and visual network Z statistics. There was a negative correlation between the rCBV and the Z statistics for the DMN, for both BOLD and CBV-rs-fMRI contrast (R(2)=0.63, 0.76). A similar correlation was not found for the visual network. Short repetition time rs-fMRI data were Fourier transformed to evaluate the effect of ferumoxytol on cardiac and respiratory fluctuations in the brain rs-BOLD, CBV signals. Cardiac and respiratory fluctuations decreased to baseline within large vessels post ferumoxytol. Robust rs-fMRI and CBV mapping is possible in normal human brain. PMID:23831413

D'Arceuil, Helen; Coimbra, Alexandre; Triano, Pamela; Dougherty, Margaret; Mello, Julie; Moseley, Michael; Glover, Gary; Lansberg, Maarten; Blankenberg, Francis

2013-07-03

115

Dynamic contrast-enhanced MRI reveals the extent and the microvascular pattern of breast ductal carcinoma in situ.  

PubMed

To report the role of magnetic resonance imaging (MRI) in assessing the extent of breast ductal carcinoma in situ (DCIS). To assess whether the microvascularity pattern in DCIS correlates with magnetic resonance enhancement. Eighty-five histologically proven DCIS (77 pure DCIS, eight microinvasive DCIS) were prospectively studied with MRI. The morphology of magnetic resonance enhancement and the kinetic curve was recorded. Histopathologically, intraductal lesions were classified according to Van Nuys score. Tumor microvascularity was immunohistochemically assessed in a subset of 24 DCIS evaluating the number of microvessels, microvascularity area, and microvascularity pattern (diffuse or periductal). On the mammogram, 74% of DCIS appeared as microcalcifications. On MRI, 70% of DCIS showed enhancement. Non-mass-like uptake was observed in 78% of cases. The mean size of nonenhancing carcinomas was significantly lower than that of enhancing carcinomas (p = 0.033). The diffuse pattern was more frequent than the periductal pattern. A significant relationship between the morphology of MR enhancement and the microvascularity pattern was observed (p = 0.036); thus, 90% of DCIS showing segmental enhancement on MRI displayed a diffuse pattern while all DCIS with ductal enhancement showed a periductal pattern. There was a significant relationship between the maximum area of microvascularity and the vascular pattern (p = 0.015); periductal patterns showed larger areas than diffuse patterns. The lesion size was significantly larger as the Van Nuys score increased (p < 0.001) and was also related to the number of microvessels (p = 0.012). The mean area of microvascularity of DCIS was significantly larger as the Van Nuys score increased (p = 0.02). Breast MRI helps depict the extent of DCIS and reveals its microvascular pattern. PMID:23758454

Santamaría, Gorane; Velasco, Martín; Farrús, Blanca; Caparrós, Francesc Xavier; Fernández, Pedro Luis

2013-06-12

116

Comment to: Parametric Response Map as an Imaging Biomarker to Distinguish Progression from Pseudoprogression in High-Grade Glioma: Pitfalls in Perfusion MRI in Brain Tumors  

Microsoft Academic Search

Summary  Pseudoprogression is a recently recognized phenomenon which occurs mainly within the first 3 months after resection and radiochemotherapy\\u000a of glioblastomas in up to 30% of cases. It refers to contrast enhancement with or without clinical deterioration which spontaneously\\u000a resolves and which is not regarded as being related to tumor growth. Even with advanced imaging techniques it is not yet possible\\u000a to

A. Radbruch; M. Bendszus; W. Wick; S. Heiland

2010-01-01

117

Enhanced emotional reactivity after selective REM sleep deprivation in humans: an fMRI study  

PubMed Central

Converging evidence from animal and human studies suggest that rapid eye movement (REM) sleep modulates emotional processing. The aim of the present study was to explore the effects of selective REM sleep deprivation (REM-D) on emotional responses to threatening visual stimuli and their brain correlates using functional magnetic resonance imaging (fMRI). Twenty healthy subjects were randomly assigned to two groups: selective REM-D, by awakening them at each REM sleep onset, or non-rapid eye movement sleep interruptions (NREM-I) as control for potential non-specific effects of awakenings and lack of sleep. In a within-subject design, a visual emotional reactivity task was performed in the scanner before and 24 h after sleep manipulation. Behaviorally, emotional reactivity was enhanced relative to baseline (BL) in the REM deprived group only. In terms of fMRI signal, there was, as expected, an overall decrease in activity in the NREM-I group when subjects performed the task the second time, particularly in regions involved in emotional processing, such as occipital and temporal areas, as well as in the ventrolateral prefrontal cortex, involved in top-down emotion regulation. In contrast, activity in these areas remained the same level or even increased in the REM-D group, compared to their BL level. Taken together, these results suggest that lack of REM sleep in humans is associated with enhanced emotional reactivity, both at behavioral and neural levels, and thus highlight the specific role of REM sleep in regulating the neural substrates for emotional responsiveness.

Rosales-Lagarde, Alejandra; Armony, Jorge L.; del Rio-Portilla, Yolanda; Trejo-Martinez, David; Conde, Ruben; Corsi-Cabrera, Maria

2012-01-01

118

Comparative analysis of ferumoxytol and gadoteridol enhancement using T1- and T2-weighted MRI in neuroimaging  

PubMed Central

Purpose Ferumoxytol, an ultrasmall superparamagnetic particle of iron oxide, was suggested as a potential alternative MRI contrast agent in patients with renal failure. We compared ferumoxytol to gadoteridol enhancement on T1- and T2-weighted MRI in CNS pathology to explore its diagnostic utility. Materials & Methods Data were collected from 3 IRB-approved HIPAA-compliant protocols in 70 adults who underwent alternate day post-gadoteridol and post-ferumoxytol MRI using identical parameters. Two neuroradiologists measured lesion enhancing size and intensity on post-contrast T1-weighted acquisitions in consensus. T2-weighted images were evaluated for the presence of post-contrast hypointensity. Mixed model repeated measures analysis of variance determined differences between T1 – weighted enhancement size and intensity for individual protocols and group. Results Following exclusions, 49 MRI studies in 29 males and 20 females (mean age 51 years) were assessed. T1-weighted estimated enhancing sizes were different between agents (p = 0.0456) as a group, however no differences were observed with untreated gliomas (n=17) on two protocols (p = 1.0, 0.99 respectively). Differences in T1-weighted enhancement intensity between agents were significant for the group (p = 0.0006) until interactions of protocol and agent were considered (non-significant). T2-weighted images were assessed for post-contrast hypointensity, observed in 26/51 (51%) of ferumoxytol and 0/51 (0%) of gadoteridol scans. Conclusion Ferumoxytol may be a useful MRI contrast agent in patients unable to receive gadolinium-based contrast agents (GBCA). Greater experience with a wider variety of pathology is necessary in order to understand differences in enhancement with ferumoxytol compared to GBCA given different mechanisms of action.

Hamilton, BE; Nesbit, GM; Dosa, E; Gahramanov, S; Rooney, B; Nesbit, EG; Raines, J; Kraemer, Dale; Neuwelt, EA

2012-01-01

119

Imaging corticospinal tract connectivity in injured rat spinal cord using manganese-enhanced MRI  

PubMed Central

Background Manganese-enhanced MRI (MEI) offers a novel neuroimaging modality to trace corticospinal tract (CST) in live animals. This paper expands this capability further and tests the utility of MEI to image axonal fiber connectivity in CST of injured spinal cord (SC). Methods A rat was injured at the thoracic T4 level of the SC. The CST was labeled with manganese (Mn) injected intracortically at two weeks post injury. Next day, the injured SC was imaged using MEI and diffusion tensor imaging (DTI) modalities. Results In vivo MEI data obtained from cervical SC confirmed that CST was successfully labeled with Mn. Ex vivo MEI data obtained from excised SC depicted Mn labeling of the CST in SC sections caudal to the lesion, which meant that Mn was transported through the injury, possibly mediated by viable CST fibers present at the injury site. Examining the ex vivo data from the injury epicenter closely revealed a thin strip of signal enhancement located ventrally between the dorsal horns. This enhancement was presumably associated with the Mn accumulation in these intact fibers projecting caudally as part of the CST. Additional measurements with DTI supported this view. Conclusion Combining these preliminary results collectively demonstrated the feasibility of imaging fiber connectivity in experimentally injured SC using MEI. This approach may play important role in future investigations aimed at understanding the neuroplasticity in experimental SCI research.

Bilgen, Mehmet

2006-01-01

120

Prognostic implication of late gadolinium enhancement on cardiac MRI in light chain (AL) amyloidosis on long term follow up  

Microsoft Academic Search

BACKGROUND: Light chain amyloidosis (AL) is a rare plasma cell dyscrasia associated with poor survival especially in the setting of heart failure. Late gadolinium enhancement (LGE) on cardiac MRI was recently found to correlate with myocardial amyloid deposition but the prognostic role is not established. The aim is to determine the prognostic significance of LGE in AL by comparing long

Raymond Q Migrino; Richard Christenson; Aniko Szabo; Megan Bright; Seth Truran; Parameswaran Hari

2009-01-01

121

Role of dynamic contrast enhanced MRI in monitoring early response of locally advanced breast cancer to neoadjuvant chemotherapy  

Microsoft Academic Search

Neoadjuvant chemotherapy has become the standard treatment for patients with locally advanced breast cancer; however a technique that can accurately differentiate responders from non-responders at an early time point during treatment has still to be identified. The purpose of this work was to evaluate the ability of pharmacokinetically modelled dynamic contrast-enhanced MRI data to predict and monitor response of patients

Martin D. Pickles; Martin Lowry; David J. Manton; Peter Gibbs; Lindsay W. Turnbull

2005-01-01

122

Lung ventilation- and perfusion-weighted Fourier decomposition magnetic resonance imaging: in vivo validation with hyperpolarized 3He and dynamic contrast-enhanced MRI.  

PubMed

The purpose of this work was to validate ventilation-weighted (VW) and perfusion-weighted (QW) Fourier decomposition (FD) magnetic resonance imaging (MRI) with hyperpolarized (3)He MRI and dynamic contrast-enhanced perfusion (DCE) MRI in a controlled animal experiment. Three healthy pigs were studied on 1.5-T MR scanner. For FD MRI, the VW and QW images were obtained by postprocessing of time-resolved lung image sets. DCE acquisitions were performed immediately after contrast agent injection. (3)He MRI data were acquired following the administration of hyperpolarized helium and nitrogen mixture. After baseline MR scans, pulmonary embolism was artificially produced. FD MRI and DCE MRI perfusion measurements were repeated. Subsequently, atelectasis and air trapping were induced, which followed with FD MRI and (3)He MRI ventilation measurements. Distributions of signal intensities in healthy and pathologic lung tissue were compared by statistical analysis. Images acquired using FD, (3)He, and DCE MRI in all animals before the interventional procedure showed homogeneous ventilation and perfusion. Functional defects were detected by all MRI techniques at identical anatomical locations. Signal intensity in VW and QW images was significantly lower in pathological than in healthy lung parenchyma. The study has shown usefulness of FD MRI as an alternative, noninvasive, and easily implementable technique for the assessment of acute changes in lung function. PMID:22392633

Bauman, Grzegorz; Scholz, Alexander; Rivoire, Julien; Terekhov, Maxim; Friedrich, Janet; de Oliveira, Andre; Semmler, Wolfhard; Schreiber, Laura Maria; Puderbach, Michael

2012-03-05

123

Same-session functional assessment of rat retina and brain with manganese-enhanced MRI  

PubMed Central

Manganese-enhanced MRI (MEMRI) is a powerful non-invasive approach for objectively measuring either retina or binocular visual brain activity in vivo. In this study, we investigated the sensitivity of MEMRI to monocular stimulation using a new protocol for providing within-subject functional comparisons in the retina and brain in the same scanning session. Adult Sprague Dawley or Long–Evans rats had one eye covered with an opaque patch. After intraperitoneal Mn2+ administration on the following day, rats underwent visual stimulation for 8 h. Animals were then anesthetized, and the brain and each eye examined by MEMRI. Function was assessed through pairwise comparisons of the patched (dark-adapted) versus unpatched (light-exposed) eyes, and of differentially-stimulated brain structures – the dorsal lateral geniculate nucleus, superior colliculus, and visual cortical regions – contralateral to the patched versus unpatched eye. As expected, Mn2+ uptake was greater in the outer retina of dark-adapted, relative to light-exposed, eyes (P<0.05). Contralateral to the unpatched eye, significantly more Mn2+ uptake was found throughout the visual brain regions than in the corresponding structures contralateral to the patched eye (P<0.05). Notably, this regional pattern of activity corresponded well to previous work with monocular stimulation. No stimulation-dependent differences in Mn2+ uptake were observed in negative control brain regions (P>0.05). Post-hoc assessment of functional data by animal age and strain revealed no significant effects. These results demonstrate, for the first time, the acquisition of functional MRI data from the eye and visual brain regions in a single scanning session.

Bissig, David; Berkowitz, Bruce A.

2013-01-01

124

Myelin mapping in the central nervous system of living mice using contrast-enhanced magnetization transfer MRI.  

PubMed

This work compares magnetization transfer (MT) MRI of living mice with contrast-enhanced MT MRI using intraventricular administration of gadopentetate dimeglumine (Gd-DTPA), systemic administration of MnCl2, and both. In MT MRI at 9.4 T, the contrast-to-noise ratio (CNR) between white matter (WM) and gray matter (GM) increased by 85% after Gd-DTPA injection into the lateral ventricle. When applied in conjunction with manganese-enhanced MT MRI (117 ?m isotropic resolution, 6 min measuring time), Gd-DTPA boosted the CNR increase from +56% to +117%. Additional T1 measurements at 2.35 T revealed that intraventricular Gd-DTPA shortens the T1 of GM much more than that of WM, which corresponds to estimated extracellular spaces of 26% in GM and only 15% in WM. These results explain the additional MT contrast enhancement by Gd-DTPA and demonstrate that the T1 shortening by intracellular Mn2+ is well complemented by extracellular Gd-DTPA. The data suggest a high myelin and low water content to hinder access of hydrophilic paramagnetic agents, so that the resulting differential accumulation effectively reduces the MT saturation in water-rich tissues and thereby facilitates the mapping of myelin-rich tissues. Finally, a 156% CNR increase between GM and WM for contrast-enhanced MT MRI at 9.4T using both Gd-DTPA and manganese allowed for 60?m isotropic resolution (102 min measuring time), which delineated myelinated fibers and layers even within GM areas such as the thalamus and cerebellar cortex. Improved MT contrasts were also seen in the cervical spinal cord. PMID:22796983

Watanabe, Takashi; Frahm, Jens; Michaelis, Thomas

2012-07-14

125

Dynamic Contrast-Enhanced MRI Kinetics of Invasive Breast Cancer: A Potential Prognostic Marker for Radiation Therapy  

SciTech Connect

Purpose: Our goal was to determine the correlations between dynamic contrast-enhanced MRI (DCE-MRI) kinetics of breast cancers and axillary nodal status (ANS) which may have prognostic value in designing radiation therapy recommendations. Methods and Materials: A retrospective review identified 167 consecutive patients treated with external beam radiotherapy for invasive breast cancer from Jan 1, 2006 to Nov 1, 2007. Patients with DCE-MRI kinetic data from our institution who underwent axillary surgical staging prior to chemotherapy were included. ANS was assessed as positive or negative by pathology record review. For each primary cancer, maximum tumor diameter and kinetic values for initial peak enhancement (PE), percent initial rapid enhancement (RE), and percent delayed washout enhancement (WE) were measured with a computer-aided evaluation program. Univariate, multivariate, and receiver operating characteristic curve analyses were performed according to the ANS. Results: Forty-six patients met study criteria, with 32 (70%) node-negative and 14 (30%) node-positive patients. Median PE was significantly greater in node-positive patients (209%) than in node-negative patients (138%, p = 0.0027). Similarly, median RE was significantly greater in node-positive patients (57%) than in node-negative patients (27%, p = 0.0436). WE was not different between groups (p = 0.9524). Median maximum tumor diameter was greater in node-positive patients (26 mm) than in node-negative patients (15 mm, p = 0.015). Multivariate analysis showed that only PE trended toward significance (p = 0.18). Conclusions: DCE-MRI kinetics of primary breast cancers correlate with ANS. Multivariate analysis demonstrates the correlation is not due simply to underlying lesion size. If validated prospectively, DCE-MRI kinetics may aid as a tool in selecting patients or designing fields for radiation therapy.

Loiselle, Christopher R., E-mail: Loiselle@u.washington.ed [Department of Radiation Oncology, University of Washington Medical Center, Seattle, Washington 98195 (United States); Eby, Peter R.; DeMartini, Wendy B.; Peacock, Sue M.S. [Department of Radiology, University of Washington Medical Center, Seattle, Washington 98195 (United States); Seattle Cancer Care Alliance, 825 Eastlake Ave. E, Seattle, Washington 98109 (United States); Bittner, Nathan [Department of Radiation Oncology, University of Washington Medical Center, Seattle, Washington 98195 (United States); Lehman, Constance D. [Department of Radiology, University of Washington Medical Center, Seattle, Washington 98195 (United States); Seattle Cancer Care Alliance, 825 Eastlake Ave. E, Seattle, Washington 98109 (United States); Kim, Janice N. [Department of Radiation Oncology, University of Washington Medical Center, Seattle, Washington 98195 (United States); Seattle Cancer Care Alliance, 825 Eastlake Ave. E, Seattle, Washington 98109 (United States)

2010-04-15

126

Contrast-Enhanced Whole-Heart Coronary MRI with Bolus Infusion of Gadobenate Dimeglumine at 1.5 T  

PubMed Central

We sought to investigate the T1 kinetics of blood and myocardium after three infusion schemes of gadobenate dimeglumine (Gd-BOPTA) and subsequently compared contrast-enhanced whole-heart coronary MRI after a bolus Gd-BOPTA infusion with nonenhanced coronary MRI at 1.5T. Blood and myocardium T1 was measured in seven healthy adults, after each underwent three Gd-BOPTA infusion schemes (bolus: 0.2 mmol/kg at 2 ml/sec, hybrid: 0.1 mmol/kg at 2 ml/sec followed by 0.1 mmol/kg at 0.1 ml/sec, and slow: 0.2 mmol/kg at 0.3 ml/sec). Fourteen additional subjects underwent contrast-enhanced coronary MRI with an inversion-recovery steady-state-free-precession sequence after bolus Gd-BOPTA infusion. Images were compared with nonenhanced T2-prepared SSFP whole-heart coronary MRI in signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), depicted vessel length, vessel sharpness, and subjective image quality. Bolus and slow infusion schemes resulted in similar T1 during coronary MRI, whereas the hybrid infusion method yielded higher T1 values. A bolus infusion of Gd-BOPTA significantly improved SNR, CNR, depicted coronary artery length, and subjective image quality when all segments were collectively compared but not when compared segment by segment. In conclusion, whole-heart SSFP coronary MRI at 1.5T can benefit from a bolus infusion of 0.2 mmol/kg Gd-BOPTA.

Hu, Peng; Chan, Jonathan; Ngo, Long H.; Smink, Jouke; Goddu, Beth; Kissinger, Kraig V.; Goepfert, Lois; Hauser, Thomas H.; Rofsky, Neil M.; Manning, Warren J.; Nezafat, Reza

2010-01-01

127

Detection of Neovessels in Atherosclerotic Plaques of Rabbits using Dynamic Contrast Enhanced MRI and 18F-FDG PET  

PubMed Central

Introduction The association of inflammatory cells and neovessels in atherosclerosis is considered a histological hallmark of high-risk active lesions. Therefore, the development and validation of noninvasive imaging techniques that allow for the detection of inflammation and neoangiogenesis in atherosclerosis would be of major clinical interest. Objective Our aim was to test two techniques, black blood dynamic contrast enhanced MRI (DCE-MRI) and 18-fluorine-fluorodeoxyglucose (18F-FDG) PET, to quantify inflammation expressed as plaque neovessels content in a rabbit model of atherosclerosis. Methods and Results Atherosclerotic plaques were induced in the aorta of ten rabbits by a combination of two endothelial abrasions and four months hyperlipidemic diet. Six rabbits underwent MRI during the injection of Gd-DTPA, while four rabbits were imaged after injection of 18F-FDG with PET. We found a positive correlation between neovessels count in atherosclerotic plaques and 1) Gd-DTPA uptake parameters evaluated by DCE-MRI (r = 0.89, p = 0.016) and 2) 18F-FDG uptake evaluated by PET (r = 0.5, p =0.103 after clustered robust, Huber-White, standard errors analysis). Conclusion DCE-MRI and 18F-FDG PET may allow for the evaluation of inflammation in atherosclerotic plaques of rabbits. These non-invasive imaging modalities could be proposed as clinical tools in the evaluation of lesion prognosis and monitoring of anti–angiogenic therapies.

Calcagno, Claudia; Cornily, Jean-Christophe; Hyafil, Fabien; Rudd, James H. F.; Briley-Saebo, Karen C.; Mani, Venkatesh; Goldschlager, Gregg; Machac, Josef; Fuster, Valentin; Fayad, Zahi A.

2011-01-01

128

Influence of post-treatment delay on the evaluation of the response to focused ultrasound surgery of breast cancer by dynamic contrast enhanced MRI  

Microsoft Academic Search

The assessment of the effectiveness of MRI-guided focused ultrasound surgery (MRIgFUS) of breast carcinomas can be performed by dynamic contrast- enhanced magnetic resonance imaging (DCE-MRI) parameters which monitor the presence of residual tumour. The aim of this study was to evaluate the effect of the post-treatment delay on this assessment. DCE-MRI data were acquired immediately and 3-14 days after MRIgFUS

A Khiat; D GIANFELICE; M AMARA; Y BOULANGER

2006-01-01

129

Contrast-enhanced cardiac MRI before coronary artery bypass surgery: impact of myocardial scar extent on bypass flow.  

PubMed

The aim of the study was to relate the extent of myocardial late gadolinium enhancement (LGE) in cardiac MRI to intraoperative graft flow in patients undergoing coronary artery bypass graft (CABG) surgery. Thirty-three CAD patients underwent LGE MRI before surgery using an inversion-recovery GRE sequence (turboFLASH). Intraoperative graft flow in Doppler ultrasonography was compared with the scar extent in each coronary vessel territory. One hundred and fourteen grafts were established supplying 86 of the 99 vessel territories. A significant negative correlation was found between scar extent and graft flow (r = -0.4, p < 0.0001). Flow in grafts to territories with no or small subendocardial scar was significantly higher than in grafts to territories with broad nontransmural or transmural scar (75 +/- 39 vs. 38 +/- 26 cc min(-1); p < 0.0001). In summary, the extent of myocardial scar as defined by contrast-enhanced MRI predicts coronary bypass graft flow. Beyond the probability of functional recovery, preoperative MRI might add value to surgery planning by predicting midterm bypass graft patency. PMID:18581115

Hunold, Peter; Massoudy, Parwis; Boehm, Claudia; Schlosser, Thomas; Nassenstein, Kai; Knipp, Stephan; Eggebrecht, Holger; Thielmann, Matthias; Erbel, Raimund; Jakob, Heinz; Barkhausen, Jörg

2008-06-26

130

Model-based blind estimation of kinetic parameters in dynamic contrast enhanced (DCE)-MRI.  

PubMed

A method to simultaneously estimate the arterial input function (AIF) and pharmacokinetic model parameters from dynamic contrast-enhanced (DCE)-MRI data was developed. This algorithm uses a parameterized functional form to model the AIF and k-means clustering to classify tissue time-concentration measurements into a set of characteristic curves. An iterative blind estimation algorithm alternately estimated parameters for the input function and the pharmacokinetic model. Computer simulations were used to investigate the algorithm's sensitivity to noise and initial estimates. In 12 patients with sarcomas, pharmacokinetic parameter estimates were compared with "truth" obtained from model regression using a measured AIF. When arterial voxels were included in the blind estimation algorithm, the resulting AIF was similar to the measured input function. The "true" K(trans) values in tumor regions were not significantly different than the estimated values, 0.99 +/- 0.41 and 0.86 +/- 0.40 min(-1), respectively, P = 0.27. "True" k(ep) values also matched closely, 0.70 +/- 0.24 and 0.65 +/- 0.25 min(-1), P = 0.08. When only tissue curves free of significant vascular contribution are used (v(p) < 0.05), the resulting AIF showed substantial delay and dispersion consistent with a more local AIF such as has been observed in dynamic susceptibility contrast imaging in the brain. PMID:19859949

Fluckiger, Jacob U; Schabel, Matthias C; Dibella, Edward V R

2009-12-01

131

In vivo detection of excitotoxicity by manganese-enhanced MRI: comparison with physiological stimulation.  

PubMed

Manganese-enhanced MRI (MEMRI) is a powerful technique for the in vivo monitoring of brain function in animals. Manganese enters into cells through calcium channels, i.e., voltage-gated calcium channels and activated glutamate receptors (e.g., N-methyl-D-aspartate receptors). N-methyl-D-aspartate receptors are activated both in normal physiological and pathophysiological conditions. Consistent with these mechanisms, we showed that in the olfactory bulb, the MEMRI signal strongly increases when excitotoxic mechanisms are induced by an administration of a N-methyl-D-aspartate receptor agonist, quinolinate. We found that the intensity of the MEMRI signal in excitotoxic conditions is similar to the odor-evoked signal in normal physiological conditions. Finally, we showed that the dynamics of the MEMRI signal are determined by the early phase of manganese in the olfactory bulb. Overall, these data show that, in addition to physiological studies, MEMRI can be used as an in vivo method to follow-up the dynamics of excitotoxic events. PMID:22127903

Gobbo, Oliviero L; Petit, Fanny; Gurden, Hirac; Dhenain, Marc

2011-11-29

132

Intravascular contrast agent-enhanced MRI measuring contrast clearance and tumor blood volume and the effects of vascular modifiers in an experimental tumor  

SciTech Connect

Purpose: To examine the feasibility of using the MRI blood pool agent NC100150 for evaluation of tumor blood volume (TBV) estimates by both dynamic contrast-enhanced MRI (DCE-MRI) and susceptibility contrast MRI assays in an experimental tumor. Contrast agent clearance (K{sup trans}; depends on perfusion and permeability) from the DCE-MRI time curves was estimated, and changes in TBV and K{sup trans} were measured after administration of two drugs that reduce perfusion by different mechanisms. Methods and materials: The DCE-MRI experiments were simulated with expected physiologic values for the C3H mouse mammary carcinoma. The C3H tumor was examined by DCE-MRI and susceptibility contrast MRI with NC100150 (NC100150 Injection, Clariscan; Amersham Health, Oslo, Norway) after treatment with either hydralazine or combretastatin (Oxigene, Boston, MA). Results: Simulations showed that reliable estimates of changes in TBV and K{sup trans} could be performed with DCE-MRI. Hydralazine was shown to reduce TBV as measured by both assays and to reduce K{sup trans}. Dynamic contrast-enhanced MRI also suggested that TBV and K{sup trans} were reduced in combretastatin-treated tumors, and the TBV reduction was confirmed by susceptibility contrast MRI. Data suggested the drug to affect mainly the total TBV, whereas microvessels as such seemed less altered. Conclusion: The study supports the use of the combined DCE-MRI and susceptibility contrast MRI assay with a blood pool agent in characterizing tumors and their response to treatment.

Bentzen, Lise [Experimental Clinical Oncology, Arhus University Hospital, Arhus (Denmark)]. E-mail: lise@oncology.dk; Vestergaard-Poulsen, Peter [Neuroradiology Research Unit, Arhus University Hospital, Arhus (Denmark); Nielsen, Thomas [Experimental Clinical Oncology, Arhus University Hospital, Arhus (Denmark); Neuroradiology Research Unit, Arhus University Hospital, Arhus (Denmark); Overgaard, Jens [Experimental Clinical Oncology, Arhus University Hospital, Arhus (Denmark); Bjornerud, Atle [Department of Radiology, Rikshospitalet, Oslo (Norway); Briley-Saebo, Karen [Amersham Health, Oslo (Norway); Horsman, Michael R. [Experimental Clinical Oncology, Arhus University Hospital, Arhus (Denmark); Ostergaard, Leif [Neuroradiology Research Unit, Arhus University Hospital, Arhus (Denmark)

2005-03-15

133

Manganese-enhanced MRI reflects seizure outcome in a model for mesial temporal lobe epilepsy.  

PubMed

The neurobiological processes resulting in epilepsy, known as epileptogenesis, are incompletely understood. Manganese-enhanced MRI (MEMRI) can potentially aide in this quest as it provides superior tissue contrast, particularly of the hippocampal subregions. This longitudinal study aims to characterise the changes in the hippocampus of the post kainic acid-induced status epilepticus (KASE) rat model of mesial temporal lobe epilepsy using MEMRI in vivo. Serial acquisition of T(1)-weighted MEMRI images were taken before, 2 days and 6 weeks after KASE (10-30 mg/kg, i.p.) in 14 rats and in 11 control rats, while a second cohort of control (N=6) and epileptic animals (N=10) was imaged at 2 months post KASE only. MnCl(2) (50 mM, 10 ?l) was administered in the right lateral ventricle 1 day before scanning. Regions of interest were drawn around the hippocampus and several subregions of the hippocampus (CA1, CA3 and dentate gyrus). Markers of epilepsy such as spontaneous recurrent seizures, hippocampal neuronal loss and mossy fiber sprouting were quantified. A persistent increase in MEMRI signal intensity was found in the hippocampus, CA1 and dentate gyrus in the KASE group compared to the control group (ANOVA P<0.05). The intensity signal in the hippocampus and subregions correlated inversely with the frequency of spontaneous recurrent seizures in the chronic epileptic phase, however there was no relationship observed between histopathological changes such as cell loss and mossy fiber sprouting with seizures. This study demonstrates that MEMRI is able to detect imaging changes in the hippocampus during the course of epileptogenesis relevant for seizure expression. These data strongly indicate a relationship between manganese enhancement and spontaneous seizure outcome, suggesting that MEMRI could provide a preclinical biomarker for the severity of epileptogenesis in vivo in animal models. PMID:23220429

Dedeurwaerdere, S; Fang, K; Chow, M; Shen, Y-T; Noordman, I; van Raay, L; Faggian, N; Porritt, M; Egan, G F; O'Brien, T J

2012-12-05

134

GD-DTPA enhanced MRI of ocular transport in a rat model of chronic glaucoma.  

PubMed

Glaucoma is a neurodegenerative disease of the visual system characterized by the elevation of intraocular pressure. While this elevated pressure is related to an increased resistance to the outflow of aqueous humor from the eye, their impacts to the etiology and pathogenesis of the disease are not fully understood. This study aims to employ in vivo Gd-DTPA enhanced magnetic resonance imaging to evaluate the ocular transport following an induction of ocular hypertension in a rat model of chronic glaucoma. An experimental ocular hypertension model was induced in adult rats using an argon laser to photocoagulate the episcleral and limbal veins on the surface of the eyeball. The enhancements of the MRI signal intensity in the anterior chamber and vitreous body were measured as a function of time following systemic administration of Gd-DTPA solution at 3 mmol/kg. Results showed a progressive T1-weighted signal increase in the vitreous body of the glaucomatous eye but not the control eye. This increase occurred earlier in the anterior vitreous body than the preretinal vitreous. Further, there was an earlier Gd-DTPA transport into the anterior chamber in the majority of glaucomatous eyes. Our findings revealed the leakage of Gd-DTPA at the aqueous-vitreous interface, which was likely resulted from increased permeability of blood-aqueous or aqueous-vitreous barrier. These may explain the sources of changing biochemical compositions in the glaucomatous chamber components, which may implicate the cascades of neurodegenerative processes in the retina and the optic nerve. PMID:18639546

Chan, Kevin C; Fu, Qing-ling; Guo, Hua; So, Kwok-fai; Wu, Ed X

2008-06-28

135

Inflow-weighted pulmonary perfusion: comparison between dynamic contrast-enhanced MRI versus perfusion scintigraphy in complex pulmonary circulation  

PubMed Central

Background Due to the different properties of the contrast agents, the lung perfusion maps as measured by 99mTc-labeled macroaggregated albumin perfusion scintigraphy (PS) are not uncommonly discrepant from those measured by dynamic contrast-enhanced MRI (DCE-MRI) using indicator-dilution analysis in complex pulmonary circulation. Since PS offers the pre-capillary perfusion of the first-pass transit, we hypothesized that an inflow-weighted perfusion model of DCE-MRI could simulate the result by PS. Methods 22 patients underwent DCE-MRI at 1.5T and also PS. Relative perfusion contributed by the left lung was calculated by PS (PSL%), by DCE-MRI using conventional indicator dilution theory for pulmonary blood volume (PBVL%) and pulmonary blood flow (PBFL%) and using our proposed inflow-weighted pulmonary blood volume (PBViwL%). For PBViwL%, the optimal upper bound of the inflow-weighted integration range was determined by correlation coefficient analysis. Results The time-to-peak of the normal lung parenchyma was the optimal upper bound in the inflow-weighted perfusion model. Using PSL% as a reference, PBVL% showed error of 49.24% to ?40.37% (intraclass correlation coefficient RI?=?0.55) and PBFL% had error of 34.87% to ?27.76% (RI?=?0.80). With the inflow-weighted model, PBViwL% had much less error of 12.28% to ?11.20% (RI?=?0.98) from PSL%. Conclusions The inflow-weighted DCE-MRI provides relative perfusion maps similar to that by PS. The discrepancy between conventional indicator-dilution and inflow-weighted analysis represents a mixed-flow component in which pathological flow such as shunting or collaterals might have participated.

2013-01-01

136

Dendrimer-enhanced MRI as a diagnostic and prognostic biomarker of sepsis-induced acute renal failure in aged mice  

Microsoft Academic Search

Dendrimer-enhanced MRI as a diagnostic and prognostic biomarker of sepsis-induced acute renal failure in aged mice.BackgroundAcute renal failure (ARF) induced by sepsis has a high mortality. In an aged mouse model of sepsis-induced ARF we have previously shown that renal injury occurs before serum creatinine is elevated. Development of a noninvasive biomarker that could diagnose renal dysfunction early in sepsis

James W. Dear; HISATAKA KOBAYASHI; SANG-KYUNG JO; Mikaela K. Holly; XUZHEN HU; Peter S. T. Yuen; Martin W. Brechbiel; Robert A. Star

2005-01-01

137

Correlation of histological findings with gadolinium enhanced MRI scans during healing of a PHEMA orbital implant in rabbits  

Microsoft Academic Search

BACKGROUND\\/AIMSTo investigate a poly(2-hydroxyethyl methacrylate) (PHEMA) orbital implant with a spongy anterior hemisphere and a smooth gel posterior hemisphere, by histology correlated with magnetic resonance images.METHODSFollowing enucleation, eight rabbits received PHEMA implants to which the muscles were directly sutured, and underwent gadolinium enhanced magnetic resonance imaging (MRI) from 3 to 52 weeks. After the rabbits were killed, the implants were

Celia R Hicks; Ian T Morris; Sarojini Vijayasekaran; Michael J Fallon; Jordana McAllister; Anthony B Clayton; Traian V Chirila; Geoffrey J Crawford; Ian J Constable

1999-01-01

138

EGFRvIII Antibody Conjugated Iron Oxide Nanoparticles for MRI Guided Convection-Enhanced Delivery and Targeted Therapy of Glioblastoma  

PubMed Central

The magnetic nanoparticle has emerged as a potential multifunctional clinical tool that can provide cancer cell detection by magnetic resonance imaging (MRI) contrast enhancement as well as targeted cancer cell therapy. A major barrier in the use of nanotechnology for brain tumor applications is the difficulty in delivering nanoparticles to intracranial tumors. Iron oxide nanoparticles (IONPs; 10 nm in core size) conjugated to a purified antibody that selectively binds to the epidermal growth factor receptor (EGFR) deletion mutant (EGFRvIII) present on human glioblastoma multiforme (GBM) cells, were used for therapeutic targeting and MRI contrast enhancement of experimental glioblastoma both in vitro and in vivo after convection-enhanced delivery (CED). A significant decrease in glioblastoma cell survival was observed after nanoparticle treatment and no toxicity was observed with treatment of human astrocytes (P<0.001). Lower EGFR phosphorylation was found in glioblastoma cells after EGFRvIIIAb-IONP treatment. Apoptosis was determined to be the mode of cell death after treatment of GBM cells and glioblastoma stem cell (GSC)-containing neurospheres with EGFRvIIIAb-IONPs. MRI-guided CED of EGFRvIIIAb-IONPs allowed for the initial distribution of magnetic nanoparticles within or adjacent to intracranial human xenograft tumors and continued dispersion days later. A significant increase in animal survival was found after CED of magnetic nanoparticles (P<0.01) in mice implanted with highly tumorigenic glioblastoma xenografts (U87?EGFRvIII). IONPs conjugated to an antibody specific to the EGFRvIII deletion mutant constitutively expressed by human glioblastoma tumors can provide selective MRI contrast enhancement of tumor cells and targeted therapy of infiltrative glioblastoma cells after CED.

Hadjipanayis, Costas G.; Machaidze, Revaz; Kaluzova, Milota; Wang, Liya; Schuette, Albert J.; Chen, Hongwei; Wu, Xinying; Mao, Hui

2010-01-01

139

Dynamic Contrast Enhanced MRI of Prostate Cancer: Correlation with Morphology and Tumour Stage, Histological Grade and PSA  

Microsoft Academic Search

AIM: To quantify MRI enhancement characteristics of normal and abnormal prostatic tissues and to correlate these with tumour stage, histological grade and tumour markers.MATERIALS AND METHODS: Quantitative gradient recalled echo MR images were obtained following bolus injection of gadopentetate dimeglumine in 48 patients with prostate cancer. Turbo spin-echo T2-weighted images at the same anatomical position were reviewed for the presence

ANWAR R. PADHANI; CONNIE J. GAPINSKI; DAVID A. MACVICAR; GEOFFREY J. PARKER; JOHN SUCKLING; PATRICK B. REVELL; MARTIN O. LEACH; DAVID P. DEARNALEY; JANET E. HUSBAND

2000-01-01

140

Optimal gadolinium dose level for magnetic resonance imaging (MRI) contrast enhancement of U87-derived tumors in athymic nude rats for the assessment of photodynamic therapy  

NASA Astrophysics Data System (ADS)

This study aims to determine the effect of varying gadopentetate dimeglumine (Gd-DTPA) dose on Dynamic Contrast Enhanced-Magnetic Resonance Imaging (DCE-MRI) tracking of brain tumor photodynamic therapy (PDT) outcome. Methods: We injected 2.5 x 105 U87 cells (derived from human malignant glioma) into the brains of six athymic nude rats. After 9, 12, and 13 days DCE-MRI images were acquired on a 9.4 T micro-MRI scanner before and after administration of 100, 150, or 200 ?L of Gd-DTPA. Results: Tumor region normalized DCE-MRI scan enhancement at peak was: 1.217 over baseline (0.018 Standard Error [SE]) at the 100 ?L dose, 1.339 (0.013 SE) at the 150 ?L dose, and 1.287 (0.014 SE) at the 200 ?L dose. DCE-MRI peak tumor enhancement at the 150 ?L dose was significantly greater than both the 100 ?L dose (p < 3.323E-08) and 200 ?L dose (p < 0.0007396). Discussion: In this preliminary study, the 150 ?L Gd-DTPA dose provided the greatest T1 weighted contrast enhancement, while minimizing negative T2* effects, in DCE-MRI scans of U87-derived tumors. Maximizing Gd-DTPA enhancement in DCE-MRI scans may assist development of a clinically robust (i.e., unambiguous) technique for PDT outcome assessment.

Cross, Nathan; Varghai, Davood; Flask, Chris A.; Feyes, Denise K.; Oleinick, Nancy L.; Dean, David

2009-02-01

141

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

PubMed Central

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 50? 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.

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

142

Automated segmentation of reference tissue for prostate cancer localization in dynamic contrast enhanced MRI  

NASA Astrophysics Data System (ADS)

For pharmacokinetic (PK) analysis of Dynamic Contrast Enhanced (DCE) MRI the arterial input function needs to be estimated. Previously, we demonstrated that PK parameters have a significant better discriminative performance when per patient reference tissue was used, but required manual annotation of reference tissue. In this study we propose a fully automated reference tissue segmentation method that tackles this limitation. The method was tested with our Computer Aided Diagnosis (CADx) system to study the effect on the discriminating performance for differentiating prostate cancer from benign areas in the peripheral zone (PZ). The proposed method automatically segments normal PZ tissue from DCE derived data. First, the bladder is segmented in the start-to-enhance map using the Otsu histogram threshold selection method. Second, the prostate is detected by applying a multi-scale Hessian filter to the relative enhancement map. Third, normal PZ tissue was segmented by threshold and morphological operators. The resulting segmentation was used as reference tissue to estimate the PK parameters. In 39 consecutive patients carcinoma, benign and normal tissue were annotated on MR images by a radiologist and a researcher using whole mount step-section histopathology as reference. PK parameters were computed for each ROI. Features were extracted from the set of ROIs using percentiles to train a support vector machine that was used as classifier. Prospective performance was estimated by means of leave-one-patient-out cross validation. A bootstrap resampling approach with 10,000 iterations was used for estimating the bootstrap mean AUCs and 95% confidence intervals. In total 42 malignant, 29 benign and 37 normal regions were annotated. For all patients, normal PZ was successfully segmented. The diagnostic accuracy obtained for differentiating malignant from benign lesions using a conventional general patient plasma profile showed an accuracy of 0.64 (0.53-0.74). Using the automated per-patient calibration method the diagnostic performance improved significantly to 0.76 (0.67-0.86, p=0.017) , whereas the manual per-patient calibration showed a diagnostic performance of 0.79 (0.70-0.89, p=0.01). In conclusion, the results show that an automated per-patient reference tissue PK model is feasible. A significantly better discriminating performance compared to the conventional general calibration was obtained and the diagnostic accuracy is similar to using manual per-patient calibration.

Vos, Pieter C.; Hambrock, Thomas; Barentsz, Jelle O.; Huisman, Henkjan J.

2010-03-01

143

Development and characterization of a dynamic lesion phantom for the quantitative evaluation of dynamic contrast-enhanced MRI  

PubMed Central

Purpose: To develop a dynamic lesion phantom that is capable of producing physiological kinetic curves representative of those seen in human dynamic contrast-enhanced MRI (DCE-MRI) data. The objective of this phantom is to provide a platform for the quantitative comparison of DCE-MRI protocols to aid in the standardization and optimization of breast DCE-MRI. Methods: The dynamic lesion consists of a hollow, plastic mold with inlet and outlet tubes to allow flow of a contrast agent solution through the lesion over time. Border shape of the lesion can be controlled using the lesion mold production method. The configuration of the inlet and outlet tubes was determined using fluid transfer simulations. The total fluid flow rate was determined using x-ray images of the lesion for four different flow rates (0.25, 0.5, 1.0, and 1.5 ml?s) to evaluate the resultant kinetic curve shape and homogeneity of the contrast agent distribution in the dynamic lesion. High spatial and temporal resolution x-ray measurements were used to estimate the true kinetic curve behavior in the dynamic lesion for benign and malignant example curves. DCE-MRI example data were acquired of the dynamic phantom using a clinical protocol. Results: The optimal inlet and outlet tube configuration for the lesion molds was two inlet molds separated by 30° and a single outlet tube directly between the two inlet tubes. X-ray measurements indicated that 1.0 ml?s was an appropriate total fluid flow rate and provided truth for comparison with MRI data of kinetic curves representative of benign and malignant lesions. DCE-MRI data demonstrated the ability of the phantom to produce realistic kinetic curves. Conclusions: The authors have constructed a dynamic lesion phantom, demonstrated its ability to produce physiological kinetic curves, and provided estimations of its true kinetic curve behavior. This lesion phantom provides a tool for the quantitative evaluation of DCE-MRI protocols, which may lead to improved discrimination of breast cancer lesions.

Freed, Melanie; de Zwart, Jacco A.; Hariharan, Prasanna; R. Myers, Matthew; Badano, Aldo

2011-01-01

144

The Incremental Value of Contrast-Enhanced MRI in the Detection of Biopsy-Proven Local Recurrence of Prostate Cancer After Radical Prostatectomy: Effect of Reader Experience  

PubMed Central

OBJECTIVE The purpose of this study is to retrospectively assess the incremental value of contrast-enhanced MRI (CE-MRI) to T2-weighted MRI in the detection of postsurgical local recurrence of prostate cancer by readers of different experience levels, using biopsy as the reference standard. MATERIALS AND METHODS Fifty-two men with biochemical recurrence after prostatectomy underwent 1.5-T endorectal MRI with multiphase contrast-enhanced imaging and had biopsy within 3 months of MRI. Two radiologists (reader 1 had 1 year and reader 2 had 6 years of experience) independently reviewed each MRI study and classified the likelihood of recurrent cancer on a 5-point scale. Areas under receiver operating characteristic curves (Az) were calculated to assess readers’ diagnostic performance with T2-weighted MRI alone and combined with CE-MRI. Interobserver agreement was assessed using Cohen kappa statistics. RESULTS Thirty-three patients (63%) had biopsy-proven local recurrence of prostate cancer. With the addition of CE-MRI to T2-weighted imaging, the Az for cancer detection increased significantly for reader 1 (0.77 vs 0.85; p = 0.0435) but not for reader 2 (0.86 vs 0.88; p = 0.7294). The use of CE-MRI improved interobserver agreement from fair (? = 0.39) to moderate (? = 0.58). CONCLUSION CE-MRI increased interobserver agreement and offered incremental value to T2-weighted MRI in the detection of locally recurrent prostate cancer for the relatively inexperienced reader.

Wassberg, Cecilia; Akin, Oguz; Vargas, Hebert Alberto; Shukla-Dave, Amita; Zhang, Jingbo; Hricak, Hedvig

2012-01-01

145

Prediction of Prostate Cancer Extracapsular Extension with High Spatial Resolution Dynamic Contrast-Enhanced 3 Tesla MRI  

PubMed Central

Objectives To assess the value of dynamic contrast-enhanced (DCE) combined with T2-weighted (T2W) endorectal coil (ERC) magnetic resonance imaging (MRI) at 3 T (3T) for determining extracapsular extension (ECE) of prostate cancer. Methods In this IRB-approved study, ERC 3T MRI of the prostate was performed in 108 patients prior to radical prostatectomy. T2W fast spin-echo and DCE 3D gradient echo images were acquired. The interpretations of readers with varied experience were analyzed. MRI-based staging results were compared with radical prostatectomy histology. Descriptive statistics were generated for prediction of ECE and staging accuracies were determined by the area under the receiver-operating-characteristic curve. Results The overall sensitivity, specificity, positive predictive value, and negative predictive value for ECE were 75%, 92%, 79% and 91%, respectively. Diagnostic accuracy for staging was 86%, 80% and 91% for all readers, experienced and less experienced readers, respectively. Conclusions ERC 3T MRI of the prostate combining DCE and T2W imaging is an accurate pretheurapeutic staging tool for assessment of ECE in clinical practice across varying levels of reader experience.

Bloch, B. Nicolas; Genega, Elizabeth M.; Costa, Daniel N.; Pedrosa, Ivan; Smith, Martin P.; Kressel, Herbert Y.; Ngo, Long; Sanda, Martin G.; DeWolf, William C.; Rofsky, Neil M.

2013-01-01

146

An improved coverage and spatial resolution--using dual injection dynamic contrast-enhanced (ICE-DICE) MRI: a novel dynamic contrast-enhanced technique for cerebral tumors.  

PubMed

A new dual temporal resolution-based, high spatial resolution, pharmacokinetic parametric mapping method is described--improved coverage and spatial resolution using dual injection dynamic contrast-enhanced (ICE-DICE) MRI. In a dual-bolus dynamic contrast-enhanced-MRI acquisition protocol, a high temporal resolution prebolus is followed by a high spatial resolution main bolus to allow high spatial resolution parametric mapping for cerebral tumors. The measured plasma concentration curves from the dual-bolus data were used to reconstruct a high temporal resolution arterial input function. The new method reduces errors resulting from uncertainty in the temporal alignment of the arterial input function, tissue response function, and sampling grid. The technique provides high spatial resolution 3D pharmacokinetic maps (voxel size 1.0 × 1.0 × 2.0 mm(3)) with whole brain coverage and greater parameter accuracy than that was possible with the conventional single temporal resolution methods. High spatial resolution imaging of brain lesions is highly desirable for small lesions and to support investigation of heterogeneity within pathological tissue and peripheral invasion at the interface between diseased and normal brain. The new method has the potential to be used to improve dynamic contrast-enhanced-MRI techniques in general. PMID:22791559

Li, Ka-Loh; Buonaccorsi, Giovanni; Thompson, Gerard; Cain, John R; Watkins, Amy; Russell, David; Qureshi, Salman; Evans, D Gareth; Lloyd, Simon K; Zhu, Xiaoping; Jackson, Alan

2012-01-03

147

Iron oxide nanosized clusters embedded in porous nanorods: a new colloidal design to enhance capabilities of MRI contrast agents.  

PubMed

Development of nanosized materials to enhance the image contrast between the normal and diseased tissue and/or to indicate the status of organ functions or blood flow is essential in nuclear magnetic resonance imaging (MRI). Here we describe a contrast agent based on a new iron oxide design (superparamagnetic iron oxide clusters embedded in antiferromagnetic iron oxide porous nanorods). We show as a proof-of-concept that aqueous colloidal suspensions containing these particles show enhanced-proton relaxivities (i.e., enhanced MRI contrast capabilities). A remarkable feature of this new design is that large scale production is possible since aqueous-based routes are used, and porosity and iron oxide superparamagnetic clusters are directly developed from a single phase. We have also proved with the help of a simple model that the physical basis behind the increase in relaxivities lies on both the increase of dipolar field (interactions within iron oxide clusters) and the decrease of proton-cluster distance (porosity favors the close contact between protons and clusters). Finally, a list of possible steps to follow to enhance capabilities of this contrast agent is also included (partial coating with noble metals to add extra sensing capacity and chemical functionality, to increase the amount of doping while simultaneously carrying out cytotoxicity studies, or to find conditions to further decrease the size of the nanorods and to enhance their stability). PMID:20355739

Rebolledo, Aldo F; Laurent, Sophie; Calero, Macarena; Villanueva, Angeles; Knobel, Marcelo; Marco, Jose F; Tartaj, Pedro

2010-04-27

148

A Novel Method for Volumetric MRI Response Assessment of Enhancing Brain Tumors  

Microsoft Academic Search

Current radiographic response criteria for brain tumors have difficulty describing changes surrounding postoperative resection cavities. Volumetric techniques may offer improved assessment, however usually are time-consuming, subjective and require expert opinion and specialized magnetic resonance imaging (MRI) sequences. We describe the application of a novel volumetric software algorithm that is nearly fully automated and uses standard T1 pre- and post-contrast MRI

Charles W. Kanaly; Dale Ding; Ankit I. Mehta; Anthony F. Waller; Ian Crocker; Annick Desjardins; David A. Reardon; Allan H. Friedman; Darell D. Bigner; John H. Sampson; Maciej Lesniak

2011-01-01

149

Mn-alginate gels as a novel system for controlled release of Mn2+ in manganese-enhanced MRI.  

PubMed

The aim of the present study was to test alginate gels of different compositions as a system for controlled release of manganese ions (Mn(2+)) for application in manganese-enhanced MRI (MEMRI), in order to circumvent the challenge of achieving optimal MRI resolution without resorting to high, potentially cytotoxic doses of Mn(2+). Elemental analysis and stability studies of Mn-alginate revealed marked differences in ion binding capacity, rendering Mn/Ba-alginate gels with high guluronic acid content most stable. The findings were corroborated by corresponding differences in the release rate of Mn(2+) from alginate beads in vitro using T(1)-weighted MRI. Furthermore, intravitreal (ivit) injection of Mn-alginate beads yielded significant enhancement of the rat retina and retinal ganglion cell (RGC) axons 24?h post-injection. Subsequent compartmental modelling and simulation of ivit Mn(2+) transport and concentration revealed that application of slow release contrast agents can achieve a significant reduction of ivit Mn(2+) concentration compared with bolus injection. This is followed by a concomitant increase in the availability of ivit Mn(2+) for uptake by RGC, corresponding to significantly increased time constants. Our results provide proof-of-concept for the applicability of Mn-alginate gels as a system for controlled release of Mn(2+) for optimized MEMRI application. PMID:22434640

Mørch, Yrr A; Sandvig, Ioanna; Olsen, Oystein; Donati, Ivan; Thuen, Marte; Skjåk-Braek, Gudmund; Haraldseth, Olav; Brekken, Christian

150

Detection of renal ischemic lesions using Gd-DTPA enhanced turbo FLASH MRI: Experimental and clinical results  

SciTech Connect

Our goal was to investigate the role of Gd-DTPA-enhanced dynamic MRI in the evaluation of renal ischemic lesions. With a turbo FLASH sequence before and after injection of Gd-DTPA, nine foxhound dogs after 60-120 min of renal ischemia underwent MR examination. In addition, five patients with a tumor in a solitary kidney were examined before and after nephron-sparing renal surgery to evaluate renal perfusion and function. The experimental and clinical findings were correlated with conventional measurements of kidney function and with histological findings. Complete renal ischemia leads to a poor corticomedullary differentiation in Gd-DTPA-enhanced turbo FLASH MRI. The signal-intensity-versus-time plots of kidneys with significant postischemic changes show a less steep increase of signal intensity in the cortex and a steeper increase of signal intensity in the medulla than those of normal kidneys. Dynamic MRI demonstrate renal morphology and reflect the functional status of the renal vasculature. 21 refs., 8 figs., 1 tab.

Vosshenrich, R.; Fischer, U.; Funke, M.; Kopka, L.; Grabbe, E. [Univ. of Goettingen (Germany)] [and others

1996-03-01

151

Perfusion characteristics of late radiation injury of parotid glands: quantitative evaluation with dynamic contrast-enhanced MRI.  

PubMed

We aimed to quantitatively investigate the alteration of parotid perfusion after irradiation using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) based on a two-compartment tracer kinetic model. This study enrolled 19 patients (53.2 +/- 14.9 years) treated by head and neck radiotherapy and 19 age-relevant and sex-matched subjects as a control group. Perfusion parameters (K ( el ), k (21) and A) of parotid glands were analyzed based on the Brix model from T1-weighted DCE-MRI. Suitability of the Brix model was evaluated via Monte Carlo simulation for the goodness-of-fit. Analysis of nonlinear goodness-of-fit showed that the Brix model is appropriate in evaluating the parotid perfusion (R(2) = 0.938 +/- 0.050). The irradiated parotid glands showed significantly lower K ( el ) (P < 0.0005) and k (21) (P < 0.05) and consequently significantly higher value of peak enhancement (P < 0.0005) and time-to-peak (P < 0.0005) compared with non-irradiated ones, suggestive of gradual and prolonged accumulation and delayed wash-out of contrast agent due to increased extracellular extravascular space and decreased vascular permeability in the irradiated glands. Linear regression analysis showed dose-dependent perfusion changes of the irradiated parotid glands. We conclude that quantitative DCE-MRI is a potential tool in investigating parotid gland perfusion changes after radiotherapy. PMID:18661135

Juan, Chun-Jung; Chen, Cheng-Yu; Jen, Yee-Min; Liu, Hua-Shan; Liu, Yi-Jui; Hsueh, Chun-Jen; Wang, Chao-Ying; Chou, Yu-Ching; Chai, Yao-Te; Huang, Guo-Shu; Chung, Hsiao-Wen

2008-07-26

152

Prospective evaluation of contrast-enhanced MRI in the depiction of peritoneal spread in primary or recurrent ovarian cancer.  

PubMed

The purpose of this study was to assess the accuracy of MRI in the staging of intra-abdominal tumor seeding of ovarian carcinoma. Fifty-seven patients with suspected primary or recurrent ovarian carcinoma were included in this study. All patients received laparotomy within 8 weeks after MRI. The MRI protocol included fat-saturated T1-weighted spin-echo (SE) sequences pre- and post i.v. application of gadopentetate dimeglumine. The criteria for tumor manifestation was contrast enhancement of intra-abdominal soft tissue lesions or peritoneum. The image review was performed by a blinded radiologist, a specialist in gynecological and abdominal MR imaging. Results were compared with findings during laparotomy. Sensitivity, specificity, positive and negative predictive values, and corresponding 95% confidence intervals were calculated for single intra-abdominal locations and for groups of locations defined according to surgical strategies for intra-abdominal cytoreduction. Laparotomy and histopathology confirmed 251 abdominal tumor locations. Sensitivity was high in lower pelvis locations (73-83%) except for ureter or bladder infiltration (40%). Bowel or mesentery locations displayed sensitivity values from 73 to 77%. Sensitivity was very low for pelvic lymph nodes (28%), greater omentum (38%), and lesser sac (43%). Magnetic resonance imaging based on contrast-enhanced fat-saturated T1 SE sequences improves planning of cytoreduction preceding chemotherapy in advanced primary or relapsed ovarian carcinoma. PMID:12695813

Ricke, Jens; Sehouli, Jalid; Hach, Constanze; Hänninen, Enrique Lopez; Lichtenegger, Werner; Felix, Roland

2002-11-05

153

Noninvasive assessment of tumor microenvironment using dynamic contrast enhanced MRI and 18F- fluoromisonidazole PET imaging in neck nodal metastases  

PubMed Central

Purpose Pretreatment multimodality imaging can provide useful anatomical and functional data about tumors, including perfusion and possibly hypoxia status. The purpose of our study was to assess non-invasively the tumor microenvironment of neck nodal metastases in patients with head and neck (HN) cancer by investigating the relationship between tumor perfusion measured using Dynamic Contrast Enhanced MRI (DCE-MRI) and hypoxia measured by 18F-fluoromisonidazole (18F-FMISO) PET. Methods and Materials Thirteen newly diagnosed HN cancer patients with metastatic neck nodes underwent DCE-MRI and 18F-FMISO PET imaging prior to chemotherapy and radiation therapy. The matched regions of interests from both modalities were analyzed. To examine the correlations between DCE-MRI parameters and standard uptake value (SUV) measurements from 18F-FMISO PET, the non-parametric Spearman correlation coefficient was calculated. Furthermore, DCE-MRI parameters were compared between nodes with 18F-FMISO uptake and nodes with no 18F-FMISO uptake using Mann-Whitney U tests. Results For the 13 patients, a total of 18 nodes were analyzed. The nodal size strongly correlated with the 18F-FMISO SUV (?=0.74, p<0.001). There was a strong negative correlation between the median kep (?=?0.58, p=0.042) and the 18F-FMISO SUV. Hypoxic nodes (moderate to severe 18F-FMISO uptake) had significantly lower median Ktrans (p=0.049) and median kep (p=0.027) values than did non-hypoxic nodes (no 18F-FMISO uptake). Conclusion This initial evaluation of the preliminary results support the hypothesis that in metastatic neck lymph nodes, hypoxic nodes are poorly perfused (i.e., have significantly lower kep and Ktrans values) compared to non-hypoxic nodes.

Jansen, Jacobus F. A.; Schoder, Heiko; Lee, Nancy Y.; Wang, Ya; Pfister, David. G.; Fury, Matthew G.; Stambuk, Hilda. E.; Humm, John L.; Koutcher, Jason A.; Shukla-Dave, Amita

2009-01-01

154

Endourethral MRI  

Microsoft Academic Search

Although high-resolution MRI with phased array pelvic, endo- rectal, and endovaginal coils has dramatically enhanced the ability to visualize abnormalities of the female urethra and peri- urethral tissues, controversy still remains about the anatomy of this region. This study introduces an endourethral approach for ultra-high-resolution MRI of the female urethra and the periure- thral tissues. To this end, two different

Harald H. Quick; Jean-Michel Serfaty; Harpreet K. Pannu; Rene Genadry; Christopher J. Yeung; Ergin Atalar

2001-01-01

155

Model selection in measures of vascular parameters using dynamic contrast-enhanced MRI: experimental and clinical applications.  

PubMed

A review of the selection of models in dynamic contrast-enhanced MRI (DCE-MRI) is conducted, with emphasis on the balance between the bias and variance required to produce stable and accurate estimates of vascular parameters. The vascular parameters considered as a first-order model are the forward volume transfer constant K(trans) , the plasma volume fraction vp and the interstitial volume fraction ve . To illustrate the critical issues in model selection, a data-driven selection of models in an animal model of cerebral glioma is followed. Systematic errors and extended models are considered. Studies with nested and non-nested pharmacokinetic models are reviewed; models considering water exchange are considered. PMID:23881857

Ewing, James R; Bagher-Ebadian, Hassan

2013-08-01

156

Perfluorocarbons enhance a T2*-based MRI technique for identifying the penumbra in a rat model of acute ischemic stroke.  

PubMed

Accurate imaging of ischemic penumbra is crucial for improving the management of acute stroke patients. T2* magnetic resonance imaging (MRI) combined with a T2*oxygen challenge (T2*OC) is being developed to detect penumbra based on changes in blood deoxyhemoglobin. Using 100% O2, T2*OC-defined penumbra exhibits ongoing glucose metabolism and tissue recovery on reperfusion. However, potential limitations in translating this technique include a sinus artefact in human scans with delivery of 100% OC and relatively small signal changes. Here we investigate whether an oxygen-carrying perfluorocarbon (PFC) emulsion can enhance the sensitivity of the technique, enabling penumbra detection with lower levels of inspired oxygen. Stroke was induced in male Sprague-Dawley rats (n=17) with ischemic injury and perfusion deficit determined by diffusion and perfusion MRI, respectively. T2* signal change was measured in regions of interest (ROIs) located within ischemic core, T2*OC-defined penumbra and equivalent contralateral areas during 40% O2±prior PFC injection. Region of interest analyses between groups showed that PFC significantly enhanced the T2* response to 40% O2 in T2*-defined penumbra (mean increase of 10.6±2.3% compared to 5.6±1.5% with 40% O2, P<0.001). This enhancement was specific to the penumbra ROI. Perfluorocarbon emulsions therefore enhances the translational potential of the T2*OC technique for identifying penumbra in acute stroke patients. PMID:23801243

Deuchar, Graeme A; Brennan, David; Griffiths, Hugh; Macrae, I Mhairi; Santosh, Celestine

2013-06-26

157

The Role of Heparanase in Lymph Node Metastatic Dissemination: Dynamic Contrast-Enhanced MRI of Eb Lymphoma in Mice1  

PubMed Central

Abstract Heparanase expression has been linked to increased tumor invasion, metastasis, and angiogenesis and with poor prognosis. The aim of the study was to monitor the effect of heparanase expression on lymph node metastasis, in heparanase-overexpressing subcutaneous Eb mouse T-lymphoma tumors, and their draining lymph node. Dynamic contrast-enhanced magnetic resonance imaging (MRI) using biotin-BSA-GdDTPA-FAM/ROX was applied for analysis of blood volume, vascular permeability, and interstitial convection, and for detection of very early stages of such metastatic dissemination. Eb tumors increased extravasation, interstitial convection, and lymphatic drain of the contrast material. Interstitial flow directions were mapped by showing radial outflow interrupted in some tumors by directional flow toward the popliteal lymph node. Heparanase expression significantly increased contrast enhancement of the popliteal lymph node but not of the primary tumor. Changes in MR contrast enhancement preceded the formation of pathologically detectable metastases, and were detectable when only a few enhanced green fluorescent protein (EGFP)-expressing Eb cells were found near and within the nodes. These results demonstrate very early, heparanase-dependent vascular changes in lymph nodes that were visible by MRI following administration of biotin-BSA-GdDTPA-FAM/ROX, and can be used for studying the initial stages of lymph node infiltration.

Dafni, Hagit; Cohen, Batya; Ziv, Keren; Israely, Tomer; Goldshmidt, Orit; Nevo, Nava; Harmelin, Alon; Vlodavsky, Israel; Neeman, Michal

2005-01-01

158

Respiratory motion-compensated radial dynamic contrast-enhanced (DCE)-MRI of chest and abdominal lesions.  

PubMed

Dynamic contrast-enhanced (DCE)-MRI is becoming an increasingly important tool for evaluating tumor vascularity and assessing the effectiveness of emerging antiangiogenic and antivascular agents. In chest and abdominal regions, however, respiratory motion can seriously degrade the achievable image quality in DCE-MRI studies. The purpose of this work is to develop a respiratory motion-compensated DCE-MRI technique that combines the self-gating properties of radial imaging with the reconstruction flexibility afforded by the golden-angle view-order strategy. Following radial data acquisition, the signal at k-space center is first used to determine the respiratory cycle, and consecutive views during the expiratory phase of each respiratory period (34-55 views, depending on the breathing rate) are grouped into individual segments. Residual intrasegment translation of lesion is subsequently compensated for by an autofocusing technique that optimizes image entropy, while intersegment translation (among different respiratory cycles) is corrected using 3D image correlation. The resulting motion-compensated, undersampled dynamic image series is then processed to reduce image streaking and to enhance the signal-to-noise ratio (SNR) prior to perfusion analysis, using either the k-space-weighted image contrast (KWIC) radial filtering technique or principal component analysis (PCA). The proposed data acquisition scheme also allows for high frame-rate arterial input function (AIF) sampling and free-breathing baseline T(1) mapping. The performance of the proposed radial DCE-MRI technique is evaluated in subjects with lung and liver lesions, and results demonstrate that excellent pixelwise perfusion maps can be obtained with the proposed methodology. PMID:18956465

Lin, Wei; Guo, Junyu; Rosen, Mark A; Song, Hee Kwon

2008-11-01

159

Suitability of Pharmacokinetic Models for Dynamic Contrast-Enhanced MRI of Abdominal Aortic Aneurysm Vessel Wall: A Comparison  

PubMed Central

Purpose Increased microvascularization of the abdominal aortic aneurysm (AAA) vessel wall has been related to AAA progression and rupture. The aim of this study was to compare the suitability of three pharmacokinetic models to describe AAA vessel wall enhancement using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Materials and Methods Patients with AAA underwent DCE-MRI at 1.5 Tesla. The volume transfer constant (Ktrans), which reflects microvascular flow, permeability and surface area, was calculated by fitting the blood and aneurysm vessel wall gadolinium concentration curves. The relative fit errors, parameter uncertainties and parameter reproducibilities for the Patlak, Tofts and Extended Tofts model were compared to find the most suitable model. Scan-rescan reproducibility was assessed using the interclass correlation coefficient and coefficient of variation (CV). Further, the relationship between Ktrans and AAA size was investigated. Results DCE-MRI examinations from thirty-nine patients (mean age±SD: 72±6 years; M/F: 35/4) with an mean AAA maximal diameter of 49±6 mm could be included for pharmacokinetic analysis. Relative fit uncertainties for Ktrans based on the Patlak model (17%) were significantly lower compared to the Tofts (37%) and Extended Tofts model (42%) (p<0.001). Ktrans scan-rescan reproducibility for the Patlak model (ICC?=?0.61 and CV?=?22%) was comparable with the Tofts (ICC?=?0.61, CV?=?23%) and Extended Tofts model (ICC?=?0.76, CV?=?22%). Ktrans was positively correlated with maximal AAA diameter (Spearman’s ??=?0.38, p?=?0.02) using the Patlak model. Conclusion Using the presented imaging protocol, the Patlak model is most suited to describe DCE-MRI data of the AAA vessel wall with good Ktrans scan-rescan reproducibility.

Nguyen, V. Lai; Kooi, M. Eline; Backes, Walter H.; van Hoof, Raf H. M.; Saris, Anne E. C. M.; Wishaupt, Mirthe C. J.; Hellenthal, Femke A. M. V. I.; van der Geest, Rob J.; Kessels, Alfons G. H.; Schurink, Geert Willem H.; Leiner, Tim

2013-01-01

160

Dynamic Contrast-Enhanced MRI-Based Early Detection of Acute Renal Transplant Rejection.  

PubMed

A novel framework for the classification of acute rejection versus nonrejection status of renal transplants from 2-D dynamic contrast-enhanced magnetic resonance imaging is proposed. The framework consists of four steps. First, kidney objects are segmented from adjacent structures with a level set deformable boundary guided by a stochastic speed function that accounts for a fourth-order Markov-Gibbs random field model of the kidney/background shape and appearance. Second, a Laplace-based nonrigid registration approach is used to account for local deformations caused by physiological effects. Namely, the target kidney object is deformed over closed, equispaced contours (iso-contours) to closely match the reference object. Next, the cortex is segmented as it is the functional kidney unit that is most affected by rejection. To characterize rejection, perfusion is estimated from contrast agent kinetics using empirical indexes, namely, the transient phase indexes (peak signal intensity, time-to-peak, and initial up-slope), and a steady-phase index defined as the average signal change during the slowly varying tissue phase of agent transit. We used a kn-nearest neighbor classifier to distinguish between acute rejection and nonrejection. Performance of our method was evaluated using the receiver operating characteristics (ROC). Experimental results in 50 subjects, using a combinatoric kn-classifier, correctly classified 92% of training subjects, 100% of the test subjects, and yielded an area under the ROC curve that approached the ideal value. Our proposed framework thus holds promise as a reliable noninvasive diagnostic tool. PMID:23797240

Khalifa, Fahmi; Beache, Garth M; El-Ghar, Mohamed Abou; El-Diasty, Tarek; Gimel'farb, Georgy; Kong, Maiying; El-Baz, Ayman

2013-06-19

161

Preliminary Study of Oxygen-Enhanced Longitudinal Relaxation in MRI: A Potential Novel Biomarker of Oxygenation Changes in Solid Tumors  

SciTech Connect

Purpose: There is considerable interest in developing non-invasive methods of mapping tumor hypoxia. Changes in tissue oxygen concentration produce proportional changes in the magnetic resonance imaging (MRI) longitudinal relaxation rate (R{sub 1}). This technique has been used previously to evaluate oxygen delivery to healthy tissues and is distinct from blood oxygenation level-dependent (BOLD) imaging. Here we report application of this method to detect alteration in tumor oxygenation status. Methods and materials: Ten patients with advanced cancer of the abdomen and pelvis underwent serial measurement of tumor R{sub 1} while breathing medical air (21% oxygen) followed by 100% oxygen (oxygen-enhanced MRI). Gadolinium-based dynamic contrast-enhanced MRI was then performed to compare the spatial distribution of perfusion with that of oxygen-induced DELTAR{sub 1}. Results: DELTAR{sub 1} showed significant increases of 0.021 to 0.058 s{sup -1} in eight patients with either locally recurrent tumor from cervical and hepatocellular carcinomas or metastases from ovarian and colorectal carcinomas. In general, there was congruency between perfusion and oxygen concentration. However, regional mismatch was observed in some tumor cores. Here, moderate gadolinium uptake (consistent with moderate perfusion) was associated with low area under the DELTAR{sub 1} curve (consistent with minimal increase in oxygen concentration). Conclusions: These results provide evidence that oxygen-enhanced longitudinal relaxation can monitor changes in tumor oxygen concentration. The technique shows promise in identifying hypoxic regions within tumors and may enable spatial mapping of change in tumor oxygen concentration.

O'Connor, James P.B. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom) and Cancer Research UK Department of Medical Oncology, Christie Hospital, Manchester (United Kingdom); Naish, Josephine H.; Parker, Geoff J.M. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); Waterton, John C. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); AstraZeneca, Cheshire (United Kingdom); Watson, Yvonne [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); Jayson, Gordon C. [Cancer Research UK Department of Medical Oncology, Christie Hospital, Manchester (United Kingdom); Buonaccorsi, Giovanni A.; Cheung, Sue; Buckley, David L.; McGrath, Deirdre M. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); West, Catharine M.L. [Academic Department of Radiation Oncology, University of Manchester, Manchester (United Kingdom); Davidson, Susan E. [Department of Clinical Oncology, Christie Hospital, Manchester (United Kingdom); Roberts, Caleb; Mills, Samantha J. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); Mitchell, Claire L.; Hope, Lynn; Ton, N. Chan [Cancer Research UK Department of Medical Oncology, Christie Hospital, Manchester (United Kingdom); Jackson, Alan [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom)

2009-11-15

162

Empirical mathematical model for dynamic manganese-enhanced MRI of the murine pancreas for assessment of ?-cell function.  

PubMed

Autoimmune ablation of pancreatic ?-cells and alteration of its microvasculature may be a predictor of Type I diabetes development. A dynamic manganese-enhanced MRI (MEMRI) approach and an empirical mathematical model were developed to monitor whole pancreatic ?-cell function and vasculature modifications in mice. Normal and streptozotocin-induced diabetic FVB/N mice were imaged on a 9.4T MRI system using a 3D magnetization prepared rapid acquisition gradient echo pulse sequence to characterize low dose manganese kinetics in the pancreas head, body and tail. Average signal enhancement in the pancreas (head, body, and tail) as a function of time was fit by a novel empirical mathematical model characterizing contrast uptake/washout rates and yielding parameters describing peak signal, initial slope, and initial area under the curve. Signal enhancement from glucose-induced manganese uptake was fit by a linear function. The results demonstrated that the diabetic pancreatic tail had a significantly lower contrast uptake rate, smaller initial slope/initial area under the curve, and a smaller rate of Mn uptake following glucose activation (p<0.05) compared to the normal pancreatic tail. These observations parallel known patterns of ?-cell loss and alteration in supportive vasculature associated with diabetes. Dynamic MEMRI is a promising technique for assessing ?-cell functionality and vascular perfusion with potential applications for monitoring diabetes progression and/or therapy. PMID:23102946

Dhyani, Anita H; Fan, Xiaobing; Leoni, Lara; Haque, Muhammad; Roman, Brian B

2012-10-25

163

Retrieval of Brain Tumors with Region-Specific Bag-of-Visual-Words Representations in Contrast-Enhanced MRI Images  

PubMed Central

A content-based image retrieval (CBIR) system is proposed for the retrieval of T1-weighted contrast-enhanced MRI (CE-MRI) images of brain tumors. In this CBIR system, spatial information in the bag-of-visual-words model and domain knowledge on the brain tumor images are considered for the representation of brain tumor images. A similarity metric is learned through a distance metric learning algorithm to reduce the gap between the visual features and the semantic concepts in an image. The learned similarity metric is then used to measure the similarity between two images and then retrieve the most similar images in the dataset when a query image is submitted to the CBIR system. The retrieval performance of the proposed method is evaluated on a brain CE-MRI dataset with three types of brain tumors (i.e., meningioma, glioma, and pituitary tumor). The experimental results demonstrate that the mean average precision values of the proposed method range from 90.4% to 91.5% for different views (transverse, coronal, and sagittal) with an average value of 91.0%.

Huang, Meiyan; Yang, Wei; Yu, Mei; Lu, Zhentai; Feng, Qianjin; Chen, Wufan

2012-01-01

164

Quantification of Massive Allograft Healing with Dynamic Contrast Enhanced-MRI and Cone Beam-CT: A Pilot Study  

PubMed Central

Although massive allografts are widely used for reconstruction of critical defects in long bones caused by tumor or trauma, many will have inadequate long-term outcomes. Toward a tissue engineering solution to this problem, we developed experimental stem cell and gene therapy adjuvants that induce angiogenesis, osteogenesis, and remodeling of the structural allografts. We present data from pilot studies to show the utility of dynamic contrast enhanced MRI (DCE-MRI) to quantify vascularity after femoral osteotomy in a canine femur model and cone beam CT (CB-CT) to quantify bone volume in a patient after composite prosthetic-allograft reconstructive surgery. The results demonstrate our ability to suppress the artifacts generated by the metal implants required to secure massive allografts such that precise quantification of cortical bone revascularization (>10-fold increase at 3 weeks postoperatively) and new bone formation (accurate to about 193 ?m3) around the graft can be performed longitudinally via DCE-MRI and CB-CT, respectively.

Ehrhart, Nicole; Kraft, Susan; Conover, David; Rosier, Randy N.

2008-01-01

165

Permeability assessment of the focused ultrasound-induced blood-brain barrier opening using dynamic contrast-enhanced MRI  

NASA Astrophysics Data System (ADS)

Focused ultrasound (FUS) in conjunction with microbubbles has been shown to successfully open the blood-brain barrier (BBB) in the mouse brain. In this study, we compute the BBB permeability after opening in vivo. The spatial permeability of the BBB-opened region was assessed using dynamic contrast-enhanced MRI (DCE-MRI). The DCE-MR images were post-processed using the general kinetic model (GKM) and the reference region model (RRM). Permeability maps were generated and the Ktrans values were calculated for a predefined volume of interest in the sonicated and the control area for each mouse. The results demonstrated that Ktrans in the BBB-opened region (0.02 ± 0.0123 for GKM and 0.03 ± 0.0167 min-1 for RRM) was at least two orders of magnitude higher when compared to the contra-lateral (control) side (0 and 8.5 × 10-4 ± 12 × 10-4 min-1, respectively). The permeability values obtained with the two models showed statistically significant agreement and excellent correlation (R2 = 0.97). At histological examination, it was concluded that no macroscopic damage was induced. This study thus constitutes the first permeability assessment of FUS-induced BBB opening using DCE-MRI, supporting the fact that the aforementioned technique may constitute a safe, non-invasive and efficacious drug delivery method.

Vlachos, F.; Tung, Y.-S.; Konofagou, E. E.

2010-09-01

166

The Value of Arterial Spin-Labeled Perfusion Imaging in Acute Ischemic Stroke - Comparison with Dynamic Susceptibility Contrast Enhanced MRI  

PubMed Central

Background and Purpose To evaluate the potential clinical value of arterial spin labeled (ASL) perfusion MRI in acute ischemic stroke (AIS) through comparison with dynamic susceptibility contrast (DSC) enhanced perfusion MRI. Methods Pseudo-continuous ASL with 3D background suppressed GRASE (Gradient and Spin Echo) readout was applied with DSC perfusion MRI on 26 AIS patients. ASL CBF and multi-parametric DSC perfusion maps were rated for image quality and lesion severity/conspicuity. Mean ASL CBF and DSC perfusion values were obtained in main vascular territories. Kendall’s coefficient of concordance was calculated to evaluate the reliability of ratings. Spearman correlation coefficients were calculated to compare ratings and quantitative perfusion values between ASL and DSC perfusion maps. Results ASL CBF and DSC perfusion maps provided largely consistent results in delineating hypoperfused brain regions in AIS. Hyperemic lesions, which also appeared frequently in the AIS cases studied, were more conspicuous on ASL CBF than on DSC CBF, Mean Transit Time (MTT) and Time to the maximum of the tissue residual function (Tmax) maps. Conclusions As a rapid, noninvasive and quantitative technique, ASL has clinical utility in detecting blood flow abnormalities in AIS patients.

Wang, Danny JJ; Alger, Jeffry R; Qiao, Joe X; Hao, Qing; Hou, Samuel; Fiaz, Rana; Gunther, Matthias; Pope, Whitney B; Saver, Jeffrey L; Salamon, Noriko; Liebeskind, David S

2012-01-01

167

Gaussian mixture model-based classification of dynamic contrast enhanced MRI data for identifying diverse tumor microenvironments: preliminary results.  

PubMed

Tumor hypoxia develops heterogeneously, affects radiation sensitivity and the development of metastases. Prognostic information derived from the in vivo characterization of the spatial distribution of hypoxic areas in solid tumors can be of value for radiation therapy planning and for monitoring the early treatment response. Tumor hypoxia is caused by an imbalance between the supply and consumption of oxygen. The tumor oxygen supply is inherently linked to its vasculature and perfusion which can be evaluated by dynamic contrast enhanced (DCE-) MRI using the contrast agent Gd-DTPA. Thus, we hypothesize that DCE-MRI data may provide surrogate information regarding tumor hypoxia. In this study, DCE-MRI data from a rat prostate tumor model were analysed with a Gaussian mixture model (GMM)-based classification to identify perfused, hypoxic and necrotic areas for a total of ten tumor slices from six rats, of which one slice was used as training data for GMM classifications. The results of pattern recognition analyzes were validated by comparison to corresponding Akep maps defining the perfused area (0.84 ± 0.09 overlap), hematoxylin and eosin (H&E)-stained tissue sections defining necrosis (0.64 ± 0.15 overlap) and pimonidazole-stained sections defining hypoxia (0.72 ± 0.17 overlap), respectively. Our preliminary data indicate the feasibility of a GMM-based classification to identify tumor hypoxia, necrosis and perfusion/permeability from non-invasively acquired, in vivo DCE-MRI data alone, possibly obviating the need for invasive procedures, such as biopsies, or exposure to radioactivity, such as positron emission tomography (PET) exams. PMID:23440683

Han, S H; Ackerstaff, E; Stoyanova, R; Carlin, S; Huang, W; Koutcher, J A; Kim, J K; Cho, G; Jang, G; Cho, H

2013-02-25

168

Early Detection of Lewis Lung Carcinoma Tumor Control by Irradiation Using Diffusion-Weighted and Dynamic Contrast-Enhanced MRI  

PubMed Central

Purpose To investigate the correlation between diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) derived parameters and radioresponsiveness of Lewis lung carcinoma (LLC) tumor. Materials and Methods LLC tumor growth in C57BL/6 mouse limb was used for the experiment. The tumors were irradiated with 10 Gy×5, or 30 Gy×2 vs. sham irradiation. Fourteen tumors were subjected to DW-MRI and DCE-MRI pre-radiotherapy and weekly imaging after radiotherapy. The temporal changes in apparent diffusion coefficient (ADC) and DCE-MRI derived parameters (Ktrans, kep, ve, and vp) were correlated with tumor size, and were histologically compared with CD31 staining of resected tumors. Results The 10 Gy×5 dose inhibited tumor growth for a week, while 30 Gy×2 controlled tumor growth for a 3-week observation period. One week after radiotherapy (week 2), irradiated tumors showed significantly higher values of ADC than untreated ones (10 Gy×5, p?=?0.004; 30 Gy×2, p?=?0.01). Significantly higher values of ve were shown earlier by 30 Gy×2 vs. sham (p?=?0.01) and 10 Gy×5 vs. sham irradiation (p?=?0.05). Sustained higher ve from 10 Gy×5 compared to sham irradiated tumors was evident at week 3 (p?=?0.016) and week 4 (p?=?0.046). A 13.8% early increase in ADC for 30 Gy×2 tumor group (p?=?0.002) and a 16.5% increase for 10 Gy×5 group were noted (p?=?0.01) vs. sham irradiation (which showed a 2.2% decrease). No differences were found for Ktrans, kep, or vp. Both radiotherapy groups demonstrated significant reduction in microvessel counts. Conclusion Early increase in ADC and ve correlated with tumor control by irradiation.

Cheng, Jason Chia-Hsien; Yuan, Ang; Chen, Jyh-Horng; Lu, Yi-Chien; Cho, Kuan-Hung; Wu, Jian-Kuen; Wu, Chien-Jang; Chang, Yeun-Chung; Yang, Pan-Chyr

2013-01-01

169

Background parenchymal enhancement in the contralateral normal breast of patients undergoing neoadjuvant chemotherapy measured by DCE-MRI.  

PubMed

The purpose of this study was to analyze background parenchymal enhancement (BPE) in the contralateral normal breast of cancer patients during the course of neoadjuvant chemotherapy (NAC). Forty-five subjects were analyzed. Each patient had three MRIs, one baseline (B/L) and two follow-up (F/U) studies. The fibroglandular tissue in the contralateral normal breast was segmented using a computer-assisted algorithm. Based on the segmented fibroglandular tissue, BPE was calculated. BPE measured in baseline (B/L) and follow-up (F/U) MR studies were compared. The baseline BPE was also correlated with age and compared between pre/peri-menopausal (<55years old) and post-menopausal women (?55years old). The pre-treatment BPE measured in B/L MRI was significantly higher in women <55years old than in women ?55years old (20.1%±7.4% vs. 12.1%±5.1%, p?0.01). A trend of negative correlation between BPE and age was noted (r=-0.29). In women <55years old, BPE at F/U-1 (18.8%±6.9%) was decreased compared to B/L, and was further decreased in F/U-2 (13.3%±5.7%) which was significant compared to B/L and F/U-1. In women ?55years old, no significant difference was noted in any paired comparison among B/L, F/U-1 and F/U-2 MRI. A higher baseline BPE was associated with a greater reduction of BPE in F/U-2 MRI (r=0.73). Our study showed that younger women tended to have higher BPE than older women. BPE was significantly decreased in F/U-2 MRI after NAC in women <55years old. The reduction in BPE was most likely due to the ovarian ablation induced by chemotherapeutic agents. PMID:23992630

Chen, Jeon-Hor; Yu, Hon; Lin, Muqing; Mehta, Rita S; Su, Min-Ying

2013-08-29

170

Enhancing equation comprehension with index finger writing: An fMRI study  

Microsoft Academic Search

Learning is a complicated process composed of vision, interpretation, comprehension and memory. This study for the first time compared activities in the brain for equation reading and writing by selected professionals using functional magnetic resonance imaging (fMRI). Finger writing did not change the message pathway in brain, but on the other hand intensified stimuli on the information integration and language

Xiao-Dong Wang; Ming-Tung Wang; Duu-Jong Lee

2008-01-01

171

Direct visualization of non-human primate subcortical nuclei with contrast-enhanced high field MRI  

Microsoft Academic Search

Subcortical nuclei are increasingly targeted for deep brain stimulation (DBS) and for gene transfer to treat neurological and psychiatric disorders. For a successful outcome in patients, it is critical to place DBS electrodes or infuse viral vectors accurately within targeted nuclei. However current MRI approaches are still limited to localize brainstem and basal ganglia nuclei accurately. By combining ultra-high resolution

Naoki Tani; Olivier Joly; Hirokazu Iwamuro; Lynn Uhrig; Christopher J. Wiggins; Cyril Poupon; Hauke Kolster; Wim Vanduffel; Denis Le Bihan; Stéphane Palfi; Béchir Jarraya

2011-01-01

172

Prostate cancer computer-assisted diagnosis software using dynamic contrast-enhanced MRI  

Microsoft Academic Search

ProCAD is a computer assisted diagnosis (CAD) software dedicated to prostate DCE-MRI analysis. In addition to standard visualization features, 2D and multislice 2D contouring tools based on a seeded growing region algorithm were included in the software. Tumor volume assessment and semiquantitative analysis of suspicious lesions can be performed. A 5-levels cancer suspicion score (ranging from \\

Philippe Puech; Nacim Betrouni; Romain Viard; Arnauld Villers; Xavier Leroy; Laurent Lemaître

2007-01-01

173

MRI after implantation of a novel femoral closure device following intra-arterial catheterisation: implications for subsequent contrast-enhanced MR angiography  

Microsoft Academic Search

Objective  To assess MRI safety aspects and artefacts of a novel femoral artery closure device during contrast-enhanced MR angiography\\u000a in patients following intra-arterial catheterisation.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Ten consecutive patients underwent MRI within 24 h of coronary angiography and placement of a femoral artery closure device.\\u000a We used a T2-weighted gradient-echo MRI sequence to measure the device-related artefact size in comparison with a phantom\\u000a image,

Oliver K. Mohrs; Steffen E. Petersen; Bernd Nowak; Hans-Ulrich Kauczor; Thomas Voigtlaender

2010-01-01

174

Comparative study of fat-suppressed Gd-enhanced MRI of hands in the early stage of rheumatoid arthritis (RA) and non-RA  

Microsoft Academic Search

The object of this work was to evaluate the usefulness of fat-suppressed gadolinium (Gd)-enhanced magnetic resonance imaging\\u000a (MRI) for the diagnosis of early-stage rheumatoid arthritis. Forty wrists of patients who had suffered from stiff or swollen\\u000a hands for 1–12 months were examined prospectively by MRI. Rheumatoid arthritis (RA) was proven in 21 patients, and the other\\u000a 19 patients were not

Tomoko Matsumoto; Toshiyuki Tsurumoto; Hiroyuki Shindo; Masataka Uetani

2001-01-01

175

Quantitative dynamic contrast enhanced MRI of experimental synovitis in the rabbit knee: Comparison of macromolecular blood pool agents vs. Gadolinium-DOTA  

Microsoft Academic Search

The purpose of this study was to assess 2 Gd-based macromolecular intravascular contrast agents (P792, rapid clearance blood pool agent (rBPA) and P717, slow clearance blood pool agent (sBPA)) compared to Gd-DOTA (representative extracellular non specific agent) in MR imaging of knee rabbit experimental synovitis. Quantitative dynamic contrast enhanced MRI (qDCE-MRI) after intravascular injection of a low molecular weight contrast

Astrid Watrin-Pinzano; Damien Loeuille; Jean-Christophe Goebel; Françoise Lapicque; Fredéric Walter; Philippe Robert; Patrick Netter; Claire Corot; Pierre Gillet; Alain Blum

176

Hybrid assemblies based on a gadolinium-containing polyoxometalate and a cationic polymer with spermine side chains for enhanced MRI contrast agents.  

PubMed

Supramolecular assembly: Spherical and stable hybrid assemblies based on a cationic polymer with spermine side chains and an anionic Gd(3+) -containing polyoxometalate cluster (GdW) are prepared by electrostatic interaction. The T1 -weighted MRI performance of GdW is enhanced about three times in the assemblies; meanwhile, the assemblies show good biocompatibility, which enables them to be promising candidates for MRI contrast agents. PMID:24030934

Chai, Wenqiang; Wang, Shan; Zhao, Hang; Liu, Guifeng; Fischer, Karl; Li, Haolong; Wu, Lixin; Schmidt, Manfred

2013-09-12

177

Comparison of triple dose versus standard dose gadolinium-DTPA for detection of MRI enhancing lesions in patients with MS.  

PubMed

We studied whether a triple dose of gadolinium-DTPA alone or in combination with delayed scanning increases the sensitivity of brain MRI for detecting enhancing lesions in patients with MS. We obtained T1-weighted brain MRI scans in two sessions for 22 patients with clinically definite MS. In the first session, we obtained one scan 5 to 7 minutes after the injection of 0.1 mmol/kg gadolinium-DTPA (standard dose). In the second session, 6 to 24 hours later, we obtained one scan before the two scans 5 to 7 minutes (for all patients) and one hour (for 11 patients) after the injection of 0.3 mmol/kg gadolinium-DTPA (triple dose). We detected 83 enhancing lesions in 14 patients when the standard dose of gadolinium-DTPA was used. The numbers of enhancing lesions increased to 138 (average increase 66%; p = 0.001) and the numbers of patients with such lesions to 18 (increase 28%) when we used the triple dose of gadolinium-DTPA. In addition, the total area per patient occupied by such lesions was greater (p < 0.0001) and lesion signal intensity higher (p = 0.0001) on the triple-dose scans than the standard-dose scans. There was an increase in the number of large enhancing lesions (p = 0.03) in the scans obtained 1 hour after the injection of the triple dose of gadolinium-DTPA. These data indicate that in patients with MS, a triple dose of gadolinium-DTPA can reveal many more enhancing lesions, which also appear larger. This suggests that the pathologic nature of "active" lesions in MS is heterogeneous, which might have impact on planning clinical trials. PMID:8614498

Filippi, M; Yousry, T; Campi, A; Kandziora, C; Colombo, B; Voltz, R; Martinelli, V; Spuler, S; Bressi, S; Scotti, G; Comi, G

1996-02-01

178

SPIO-conjugated, doxorubicin-loaded microbubbles for concurrent MRI and focused-ultrasound enhanced brain-tumor drug delivery.  

PubMed

The blood-brain barrier (BBB) can be temporarily and locally opened by focused ultrasound (FUS) in the presence of circulating microbubbles (MBs). Currently, contrast-enhanced magnetic resonance imaging (CE-MRI) is used to monitor contrast agent leakage to verify BBB-opening and infer drug deposition. However, despite being administered concurrently, MBs, therapeutic agent, and contrast agent have distinct pharmacodynamic behaviors, thus complicating the quantification and optimization of BBB-opening and drug delivery. Here we propose multifunctional MBs loaded with therapeutic agent (doxorubicin; DOX) and conjugated with superparamagnetic iron oxide (SPIO) nanoparticles. These DOX-SPIO-MBs were designed to concurrently open the BBB and perform drug delivery upon FUS exposure, act as dual MRI and ultrasound contrast agent, and allow magnetic targeting (MT) to achieve enhanced drug delivery. We performed burst-tone FUS after injection of DOX-SPIO-MBs, followed by MT with an external magnet attached to the scalp in a rat glioma model. Animals were monitored by T2-weighted MRI and susceptibility weighted imaging and the concentration of SPIO particles was determined by spin-spin relaxivity. We found that DOX-SPIO-MBs were stable and provided significant superparamagnetic/acoustic properties for imaging. BBB-opening and drug delivery were achieved concurrently during the FUS exposure. In addition, MT increased local SPIO deposition in tumor regions by 22.4%. Our findings suggest that DOX-SPIO-MBs with FUS could be an excellent theranostic tool for future image-guided drug delivery to brain tumors. PMID:23433776

Fan, Ching-Hsiang; Ting, Chien-Yu; Lin, Han-Jung; Wang, Chung-Hsin; Liu, Hao-Li; Yen, Tzu-Chen; Yeh, Chih-Kuang

2013-02-20

179

In vivo MRI of fresh stored osteochondral allograft transplantation with delayed gadolinium-enhanced MRI of cartilage: protocol considerations and recommendations.  

PubMed

The protocol for delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) was adapted for the evaluation of transplanted osteochondral allograft cartilage. Eight patients with focal grade 4 cartilage defects of the femoral condyle were treated with single cylindrical osteochondral allografts. At 1 and 2 years, dGEMRIC image sequences were acquired and regions of interest (ROIs) were drawn in repair and native control cartilage. Mean T1 values of region of interest were used to calculate established dGEMRIC metrics. The correlation was measured between the ?R1 and R1 -Post metrics for repair and native cartilage. T1 times were measured in deep and superficial zones of cartilage. A strong correlation was identified between full-thickness, deep, and superficial ?R1 and R1 -Post values for native cartilage and repair cartilage for all years (range: 0.893-1.0). The mean T1 times and ?R1 rate between deep and superficial regions of articular cartilage were statistically different for all regions of the distal femora analyzed at 1 year and 2 years after osteochondral allograft transplantation (P<0.05). The dGEMRIC pre-Gadolinium scan is unnecessary when evaluating transplanted osteochondral allograft cartilage. The observation of stratified T1 and ?R1 values indicates a need to re-evaluate the methodology behind the placement of region of interest in dGEMRIC. PMID:22829500

Durkan, Michael G; Szumowski, Jerzy; Brown, Dawson S; Foss, Erik W; Crawford, Dennis C

2012-07-24

180

[Studies of artifacts with TFE factor increase in heart delayed enhancement MRI sequence IR-T1TFE].  

PubMed

The characteristic of delayed enhancement MRI is high spatial resolution, which makes it possible to evaluate the degree of damage to the myocardium from the inner to the outer membrane of patients with ischemic heart disease. Therefore, this MRI technique is unique in its ability to detect myocardial condition and is necessary to obtain high-quality images. We experienced artifacts induced by TFE factor increase with delayed enhancement of IR-T1TFE. The purpose of this study was to determine the cause of such artifacts. IR-T1TFE changed signal intensity with phase direction as the TFE factor increased. Streak artifacts occurred because signal intensity caused changes with phase direction. Increases in TFE factor prolonged data collection time, such that marked artifacts were created because of changes in signal intensity. Ghost artifacts occurred because signal intensity changed between shots. When the TFE factor was increased, the difference in signal intensity was diminished between shots. The interval of acquired noise decreased in the raw data. Therefore, the interval of ghost artifacts became wider on images. PMID:15213699

Horie, Tomohiko; Ikeda, Syu; Muro, Isao

2004-05-01

181

Gradient-enhanced volume rendering: an image processing strategy to facilitate whole small bowel imaging with MRI.  

PubMed

MRI of the small bowel with positive contrast from orally administered contrast agent is a promising non-invasive imaging method. The aim of our study was to introduce small bowel MRI in a display format that clinicians are accustomed to and that maximizes the amount of information visualized on a single image. Twelve healthy volunteers, median age 32 years (range 18-49 years) participated in the study. A mixture of 20 ml Gd-DOTA (Dotarem), 0.8 g/kg body weight psyllium fibre (Metamucil) and 1.2 l water were sequentially administered over a period of 4 h. Imaging was performed on a 1.5 T unit (Philips Gyroscan, Intera). Fat-saturated, 3D, gradient echo imaging was performed while the patient was in apnea (30 s). Bowel motion was reduced with 40 mg intravenously administered scopolamine (Buscopan). A 3D, gradient-enhanced, volume rendering technique was applied to the 3D data sets. Standard projections [left anterior oblique (LAO), right anterior oblique (RAO), supine and prone] resembling conventional enteroclysis were successfully generated within fewer than 10 min processing time. Reconstructions were reproducible and provided an entire overview of the small bowel. In addition thin-slab volume rendering allowed an overlap-free display of individual structures. Positive contrast from orally administered contrast agent, combined with a gradient enhanced volume rendering method, allows the reconstruction of the small bowel in a pattern resembling conventional double-contrast enteroclysis. Segmental display without overlay is possible. PMID:17021699

Wyss, Michael; Froehlich, Johannes M; Patak, Michael A; Juli, Christoph F; Scheidegger, Markus B; Zollikofer, Christoph L; Wentz, Klaus U

2006-10-05

182

IMRT boost dose planning on dominant intraprostatic lesions: Gold marker-based three-dimensional fusion of CT with dynamic contrast-enhanced and 1H-spectroscopic MRI  

Microsoft Academic Search

PURPOSE: To demonstrate the theoretical feasibility of integrating two functional prostate magnetic resonance imaging (MRI) techniques (dynamic contrast-enhanced MRI [DCE-MRI] and 1H-spectroscopic MRI [MRSI]) into inverse treatment planning for definition and potential irradiation of a dominant intraprostatic lesion (DIL) as a biologic target volume for high-dose intraprostatic boosting with intensity-modulated radiotherapy (IMRT). METHODS AND MATERIALS: In 5 patients, four gold

Emile N. J. T. van Lin; Jurgen J. Fütterer; Stijn W. T. P. J. Heijmink; Lisette P. van der Vight; Aswin L. Hoffmann; Peter van Kollenburg; HenkJan J. Huisman; Tom W. J. Scheenen; J. Alfred Witjes; Jan Willem Leer; Jelle O. Barentsz; Andries G. Visser

2006-01-01

183

IMRT boost dose planning on dominant intraprostatic lesions: Gold marker-based three-dimensional fusion of CT with dynamic contrast-enhanced and ¹H-spectroscopic MRI  

Microsoft Academic Search

Purpose: To demonstrate the theoretical feasibility of integrating two functional prostate magnetic resonance imaging (MRI) techniques (dynamic contrast-enhanced MRI [DCE-MRI] and ¹H-spectroscopic MRI [MRSI]) into inverse treatment planning for definition and potential irradiation of a dominant intraprostatic lesion (DIL) as a biologic target volume for high-dose intraprostatic boosting with intensity-modulated radiotherapy (IMRT). Methods and Materials: In 5 patients, four gold

Emile N. J. T. van. Lin; Jurgen J. Fuetterer; Stijn W. T. P. J. Heijmink; Lisette P. van der Vight; Aswin L. Hoffmann; Peter van Kollenburg; Henk Jan J. Huisman; Tom W. J. Scheenen; J. Alfred Witjes; Jan Willem Leer; Jelle O. Barentsz; Andries G. Visser

2006-01-01

184

High-resolution contrast-enhanced MRI of atherosclerosis with digital cardiac and respiratory gating in mice.  

PubMed

Atherosclerosis initially develops predominantly at the aortic root and carotid origin, where effective visualization in mice requires efficient cardiac and respiratory gating. The present study sought to first compare the high-resolution MRI gating performance of two digital gating strategies using: 1) separate cardiac and respiratory signals (double-sensor); and 2) a single-sensor cardiorespiratory signal (ECG demodulation), and second, to apply an optimized processing technique to dynamic contrast-enhanced (CE) carotid origin vessel-wall imaging in mice. High-resolution MR mouse heart and aortic arch images were acquired by ECG signal detection, digital signal processing, and gating signal generation modeled using Simulink (MathWorks, USA). Double-sensor gating used a respiratory sensor while single-sensor gating used breathing-modulated ECG to generate a demodulated respiratory signal. Pre- and postcontrast T(1)-weighted images were acquired to evaluate vessel-wall enhancement with a gadolinium blood-pool agent (P792; Guerbet, France) at the carotid origin in vivo in ApoE(-/-) and C57BL/6 mice, using the optimized cardiorespiratory gating processing technique. Both strategies provided images with improved spatial resolution, less artifacts, and 100% correct transistor-to-transistor logic (TTL) signals. Image quality allowed vessel-wall enhancement measurement in all the ApoE(-/-) mice, with maximal (32%) enhancement 27 min postinjection. The study demonstrated the efficiency of both cardiorespiratory gating strategies for dynamic contrast-enhanced vessel-wall imaging. PMID:17969010

Alsaid, Hasan; Sabbah, Maher; Bendahmane, Zakaria; Fokapu, Odette; Felblinger, Jacques; Desbleds-Mansard, Catherine; Corot, Claire; Briguet, André; Crémillieux, Yannick; Canet-Soulas, Emmanuelle

2007-12-01

185

Direct comparison of intra-articular versus intravenous delayed gadolinium-enhanced MRI of hip joint cartilage.  

PubMed

PURPOSE: To investigate the potential of delayed gadolinium-enhanced magnetic resonance imaging in cartilage (dGEMRIC) after intra-articular (ia) contrast agent administration at 3 Tesla (T), a paired study comparing intravenous (iv) dGEMRIC (standard) with ia-dGEMRIC was performed. MATERIALS AND METHODS: Thirty-five symptomatic patients with suspected cartilage damage underwent ia- and iv-dGEMRIC. MRI was performed with a 3T system wherein the interval between both measurements was 2 weeks. For iv-dGEMRIC, FDA approved Gd-DOTA(-) was injected intravenously 45 min before the MRI scan. For ia-dGEMRIC, 10-20 mL of a 2 mM solution of Gd- DOTA(-) was injected under fluoroscopic guidance 30 min before the MRI scan. RESULTS: Both ia- and iv-dGEMRIC demonstrated the typical T1Gd pattern in hip joint cartilage with increasing values toward the superior regions in acetabular cartilage reflecting the higher glycosaminoglycan (GAG) content in the main weight-bearing area. Correlation analysis revealed a moderate correlation between both techniques (r = 0.439, P-value < 0.001), whereas the T1Gd values for iv-dGEMRIC were significantly higher than those for ia-dGEMRIC. This corresponds with the Bland-Altman plot analysis, which revealed a systemic bias (higher T1Gd values after iv gadolinium application) of ?70 ms. CONCLUSION: Ia-dGEMRIC was able to reveal the characteristic T1Gd pattern in hip joint cartilage confirming the sensitivity of ia-dGEMRIC for GAG. In addition, there was a significant correlation between iv-dGEMRIC and ia-dGEMRIC. However, the T1Gd values after ia contrast media application were significantly lower than those after iv application that has to be considered for future studies. J. Magn. Reson. Imaging 2013;. © 2013 Wiley Periodicals, Inc. PMID:23744796

Zilkens, Christoph; Miese, Falk; Kim, Young-Jo; Jäger, Marcus; Mamisch, Tallal C; Hosalkar, Harish; Antoch, Gerald; Krauspe, Rüdiger; Bittersohl, Bernd

2013-06-01

186

Flip angle optimization for dynamic contrast-enhanced MRI-studies with spoiled gradient echo pulse sequences  

NASA Astrophysics Data System (ADS)

Spoiled gradient echo pulse (SPGRE) sequences are commonly used in dynamic contrast-enhanced MRI (DCE-MRI) studies to measure the contrast agent concentration in a tissue of interest over time. However, due to improper tuning of the SPGRE parameters, concentration uncertainty can be very high, even at high signal-to-noise ratio in the MR measurement. In this work, an optimization procedure is proposed for selecting the optimal value of the SPGRE-flip angle FAopt, given the expected concentration range. The optimization condition ensures that every concentration in the assumed range has the lowest possible uncertainty. By decoupling the R1- and R*2-effects caused by the presence of the contrast agent, a contour plot has been generated from which FAopt can be read off for any study design. Investigation of ten recent DCE-MRI studies showed that improper flip angle selection unnecessarily increases the concentration uncertainty, up to 742% and 72% on average for the typical physiological concentration ranges of 0-2 mM in tumour tissue and 0-10 mM in blood, respectively. Simulations show that the reduced noise levels on the concentration curves, observed at the optimal flip angle, effectively increase the precision of the kinetic parameters estimates (up to 82% for Ktrans, 82% for ?e and 92% for ?p in the case of an individually measured arterial input function (AIF), up to 53% for Ktrans, 59% for ?e and 67% for ?p in the case of a standard AIF). In vivo experiments confirm the potential of flip angle optimization to increase the reproducibility of the kinetic parameter estimates.

De Naeyer, D.; Verhulst, J.; Ceelen, W.; Segers, P.; De Deene, Y.; Verdonck, P.

2011-08-01

187

Brain Processing of Biologically Relevant Odors in the Awake Rat, as Revealed by Manganese-Enhanced MRI  

PubMed Central

Background So far, an overall view of olfactory structures activated by natural biologically relevant odors in the awake rat is not available. Manganese-enhanced MRI (MEMRI) is appropriate for this purpose. While MEMRI has been used for anatomical labeling of olfactory pathways, functional imaging analyses have not yet been performed beyond the olfactory bulb. Here, we have used MEMRI for functional imaging of rat central olfactory structures and for comparing activation maps obtained with odors conveying different biological messages. Methodology/Principal Findings Odors of male fox feces and of chocolate flavored cereals were used to stimulate conscious rats previously treated by intranasal instillation of manganese (Mn). MEMRI activation maps showed Mn enhancement all along the primary olfactory cortex. Mn enhancement elicited by male fox feces odor and to a lesser extent that elicited by chocolate odor, differed from that elicited by deodorized air. This result was partly confirmed by c-Fos immunohistochemistry in the piriform cortex. Conclusion/Significance By providing an overall image of brain structures activated in awake rats by odorous stimulation, and by showing that Mn enhancement is differently sensitive to different stimulating odors, the present results demonstrate the interest of MEMRI for functional studies of olfaction in the primary olfactory cortex of laboratory small animals, under conditions close to natural perception. Finally, the factors that may cause the variability of the MEMRI signal in response to different odor are discussed.

Lehallier, Benoist; Rampin, Olivier; Saint-Albin, Audrey; Jerome, Nathalie; Ouali, Christian; Maurin, Yves; Bonny, Jean-Marie

2012-01-01

188

Synthesis and characterization of PEGylated Gd2O3 nanoparticles for MRI contrast enhancement.  

PubMed

Recently, much attention has been given to the development of biofunctionalized nanoparticles with magnetic properties for novel biomedical imaging. Guided, smart, targeting nanoparticulate magnetic resonance imaging (MRI) contrast agents inducing high MRI signal will be valuable tools for future tissue specific imaging and investigation of molecular and cellular events. In this study, we report a new design of functionalized ultrasmall rare earth based nanoparticles to be used as a positive contrast agent in MRI. The relaxivity is compared to commercially available Gd based chelates. The synthesis, PEGylation, and dialysis of small (3-5 nm) gadolinium oxide (DEG-Gd(2)O(3)) nanoparticles are presented. The chemical and physical properties of the nanomaterial were investigated with Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and dynamic light scattering. Neutrophil activation after exposure to this nanomaterial was studied by means of fluorescence microscopy. The proton relaxation times as a function of dialysis time and functionalization were measured at 1.5 T. A capping procedure introducing stabilizing properties was designed and verified, and the dialysis effects were evaluated. A higher proton relaxivity was obtained for as-synthesized diethylene glycol (DEG)-Gd(2)O(3) nanoparticles compared to commercial Gd-DTPA. A slight decrease of the relaxivity for as-synthesized DEG-Gd(2)O(3) nanoparticles as a function of dialysis time was observed. The results for functionalized nanoparticles showed a considerable relaxivity increase for particles dialyzed extensively with r(1) and r(2) values approximately 4 times the corresponding values for Gd-DTPA. The microscopy study showed that PEGylated nanoparticles do not activate neutrophils in contrast to uncapped Gd(2)O(3). Finally, the nanoparticles are equipped with Rhodamine to show that our PEGylated nanoparticles are available for further coupling chemistry, and thus prepared for targeting purposes. The long term goal is to design a powerful, directed contrast agent for MRI examinations with specific targeting possibilities and with properties inducing local contrast, that is, an extremely high MR signal at the cellular and molecular level. PMID:20334417

Ahrén, Maria; Selegård, Linnéa; Klasson, Anna; Söderlind, Fredrik; Abrikossova, Natalia; Skoglund, Caroline; Bengtsson, Torbjörn; Engström, Maria; Käll, Per-Olov; Uvdal, Kajsa

2010-04-20

189

Ferritin Enhances SPIO Tracking of C6 Rat Glioma Cells by MRI  

PubMed Central

Purpose To investigate the effect of ferritin protein overexpression on superparamagnetic iron oxide (SPIO) particle labeling of C6 rat glioma cells, and track the labeled cells in vivo using magnetic resonance imaging (MRI). Materials and Methods A plasmid of H-chain of murine ferritin gene was constructed and transfected into C6 cells. The parental and the transfected C6 cells labeled with SPIO were bilaterally inoculated subcutaneously into nude mice. The mice were imaged by multiple T2-weighted MR scans after C6 cell inoculation. The mice were killed 2 weeks later, and the concentration of iron in the tumor tissue was measured by inductively coupled plasma. Results The iron concentration in xenografts derived from SPIO-labeled C6 cells that were transfected with ferritin plasmid was significantly higher than that in xenografts from parental C6 cells that were labeled with SPIO but not transfected (p=0.034, N=5). Ferritin-transfected C6 cells showed an improved T2 contrast in vivo compared with parental cells labeled with SPIO but not transfected. Conclusion Coordinating ferritin with SPIO can lead to a longer MRI cellular tracking period.

Wang, Jiandong; Xie, Jin; Zhou, Xiaojun; Cheng, Zhen; Gu, Ning; Teng, Gaojun; Hu, Qiujue; Zhu, Feipeng; Chang, Shuanghui; Zhang, Fan; Lu, Guangming; Chen, Xiaoyuan

2010-01-01

190

Metal-substituted protein MRI contrast agents engineered for enhanced relaxivity and ligand sensitivity.  

PubMed

Engineered metalloproteins constitute a flexible new class of analyte-sensitive molecular imaging agents detectable by magnetic resonance imaging (MRI), but their contrast effects are generally weaker than synthetic agents. To augment the proton relaxivity of agents derived from the heme domain of cytochrome P450 BM3 (BM3h), we formed manganese(III)-containing proteins that have higher electron spin than their native ferric iron counterparts. Metal substitution was achieved by coexpressing BM3h variants with the bacterial heme transporter ChuA in Escherichia coli and supplementing the growth medium with Mn3+-protoporphyrin IX. Manganic BM3h variants exhibited up to 2.6-fold higher T1 relaxivities relative to native BM3h at 4.7 T. Application of ChuA-mediated porphyrin substitution to a collection of thermostable chimeric P450 domains resulted in a stable, high-relaxivity BM3h derivative displaying a 63% relaxivity change upon binding of arachidonic acid, a natural ligand for the P450 enzyme and an important component of biological signaling pathways. This work demonstrates that protein-based MRI sensors with robust ligand sensitivity may be created with ease by including metal substitution among the toolkit of methods available to the protein engineer. PMID:21171606

Lelyveld, Victor S; Brustad, Eric; Arnold, Frances H; Jasanoff, Alan

2011-02-01

191

Automated scoring of regional lung perfusion in children from contrast enhanced 3D MRI  

NASA Astrophysics Data System (ADS)

MRI perfusion images give information about regional lung function and can be used to detect pulmonary pathologies in cystic fibrosis (CF) children. However, manual assessment of the percentage of pathologic tissue in defined lung subvolumes features large inter- and intra-observer variation, making it difficult to determine disease progression consistently. We present an automated method to calculate a regional score for this purpose. First, lungs are located based on thresholding and morphological operations. Second, statistical shape models of left and right children's lungs are initialized at the determined locations and used to precisely segment morphological images. Segmentation results are transferred to perfusion maps and employed as masks to calculate perfusion statistics. An automated threshold to determine pathologic tissue is calculated and used to determine accurate regional scores. We evaluated the method on 10 MRI images and achieved an average surface distance of less than 1.5 mm compared to manual reference segmentations. Pathologic tissue was detected correctly in 9 cases. The approach seems suitable for detecting early signs of CF and monitoring response to therapy.

Heimann, Tobias; Eichinger, Monika; Bauman, Grzegorz; Bischoff, Arved; Puderbach, Michael; Meinzer, Hans-Peter

2012-02-01

192

Non-contrast enhanced MRI for evaluation of breast lesions: comparison of non-contrast enhanced high spectral and spatial resolution (HiSS) images vs. contrast enhanced fat-suppressed images  

PubMed Central

RATIONALE AND OBJECTIVES To evaluate high spectral and spatial resolution (HiSS) MRI for diagnosis of breast cancer without injection of contrast media: to compare the performance of pre-contrast HiSS images to conventional contrast-enhanced fat-suppressed T1-weighted images, based on image quality and in the task of classifying benign and malignant breast lesions. MATERIALS AND METHODS Ten benign and 44 malignant lesions were imaged at 1.5T with HiSS (pre-contrast administration) and conventional fat-suppressed imaging (3–10 min post-contrast). This set of 108 images, after randomization, was evaluated by three experienced radiologists blinded to the imaging technique. BIRADS morphologic criteria (lesion shape; lesion margin; internal signal intensity pattern) and final assessment were used to measure reader performance. Image quality was evaluated based on boundary delineation and quality of fat suppression. An overall probability of malignancy was assigned to each lesion for HiSS and conventional images separately. RESULTS On boundary delineation and quality of fat-suppression, pre-contrast HiSS scored similarly to conventional post-contrast MRI. On benign vs. malignant lesion separation, there was no statistically significant difference in ROC performance between HiSS and conventional MRI, and HiSS met a reasonable non-inferiority condition. CONCLUSION Pre-contrast HiSS imaging is a promising approach for showing lesion morphology without blooming and other artifacts caused by contrast agents. HiSS images could be used to guide subsequent dynamic contrast-enhanced MRI scans, to maximize spatial and temporal resolution in suspicious regions. HiSS MRI without contrast agent injection may be particularly important for patients at risk for contrast-induced nephrogenic systemic fibrosis, or allergic reactions.

Medved, Milica; Fan, Xiaobing; Abe, Hiroyuki; Newstead, Gillian M.; Wood, Abbie M.; Shimauchi, Akiko; Kulkarni, Kirti; Ivancevic, Marko K.; Pesce, Lorenzo L.; Olopade, Olufunmilayo I.; Karczmar, Gregory S.

2011-01-01

193

Gd-EOB-DTPA-Enhanced MRI for Detection of Liver Metastases from Colorectal Cancer: A Surgeon's Perspective!  

PubMed Central

Colorectal cancer affects over one million people worldwide annually, with the liver being the most common site of metastatic spread. Adequate resection of hepatic metastases is the only chance for a cure in a subset of patients, and five-year survival increases to 35% with complete resection. Traditionally, computed tomographic imaging (CT) was utilized for staging and to evaluate metastases in the liver. Recently, the introduction of hepatobiliary contrast-enhanced magnetic resonance imaging (MRI) agents including gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Eovist in the United States, Primovist in Europe, or Gd-EOB-DTPA) has proved to be a sensitive method for detection of hepatic metastases. Accurate detection of liver metastases is critical for staging of colorectal cancer as well as preoperative planning.

Lafaro, Kelly J.; Roumanis, Panayota; Demirjian, Aram N.; Lall, Chandana; Imagawa, David K.

2013-01-01

194

Issues of discontinuity in the impulse residue function for deconvolution analysis of dynamic contrast-enhanced MRI data.  

PubMed

Recent dynamic contrast-enhanced MRI studies using the adiabatic tissue homogeneity model have highlighted potential issues of difficulty in convergence during data-fitting and reduced parameter precision, due to discontinuities in the adiabatic tissue homogeneity model. This study presents two solutions (an analytic approach and a discrete correction method) to such convergence problems and show that these problems can be attributed to an inaccurate approximation of the convolution integral based on the standard trapezoidal quadrature. It is further explained that such issues of discontinuity in the impulse residue function do not pertain only to the adiabatic tissue homogeneity model, but are generic to all tracer kinetic models, if the difference in bolus arrival time between the arterial input and tissue voxels were to be accounted for simultaneously during model-fitting. PMID:21465544

Koh, T S; Cheong, D L H; Hou, Z

2011-04-04

195

Gd-EOB-DTPA-enhanced 3.0-Tesla MRI findings for the preoperative detection of focal liver lesions: Comparison with iodine-enhanced multi-detector computed tomography  

NASA Astrophysics Data System (ADS)

The safety of gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic-acid (Gd-EOB-DTPA) has been confirmed, but more study is needed to assess the diagnostic accuracy of Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) in patients with a hepatocellular carcinoma (HCC) for whom surgical treatment is considered or with a metastatic hepatoma. Research is also needed to examine the rate of detection of hepatic lesions compared to multi-detector computed tomography (MDCT), which is used most frequently to localize and characterize a HCC. Gd-EOB-DTPA-enhanced MRI and iodine-enhanced MDCT imaging were compared for the preoperative detection of focal liver lesions. The clinical usefulness of each method was examined. The current study enrolled 79 patients with focal liver lesions who preoperatively underwent MRI and MDCT. In these patients, there was less than one month between the two diagnostic modalities. Imaging data were taken before and after contrast enhancement in both methods. To evaluate the images, we analyzed the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) in the lesions and the liver parenchyma. To compare the sensitivity of the two methods, we performed a quantitative analysis of the percentage signal intensity of the liver (PSIL) on a high resolution picture archiving and communication system (PACS) monitor (paired-samples t-test, p < 0.05). The enhancement was evaluated based on a consensus of four observers. The enhancement pattern and the morphological features during the arterial and the delayed phases were correlated between the Gd-EOB-DTPA-enhanced MRI findings and the iodine-enhanced MDCT by using an adjusted x2 test. The SNRs, CNRs, and PSIL all had a greater detection rate in Gd-EOB-DTPA enhanced MRI than in iodine-enhanced MDCT. Hepatocyte-selective uptake was observed 20 minutes after the injection in the focal nodular hyperplasia (FNH, 9/9), adenoma (9/10), and highly-differentiated HCC (grade G1, 27/30). Rim enhancement was detected in all metastases (30/30). During the arterial and the delayed phases, good overall agreement between the gadoxetic-acid-enhanced MR and CT was observed (x2 test, p < 0.05). For the preoperative detection of focal liver lesions, Gd-EOB-DTPA-enhanced MRI had a higher diagnostic value and higher detection rate than iodine-enhanced MDCT. The arterial and the delayed dynamic enhancement patterns, and the gadoxetic-acid-enhanced MR imaging can provide information on the possible degree of cellular differentiation of a HCC, adenoma or metastatic tumor.

Park, Hyong-Hu; Goo, Eun-Hoe; Im, In-Chul; Lee, Jae-Seung; Kim, Moon-Jib; Kwak, Byung-Joon; Chung, Woon-Kwan; Dong, Kyung-Rae

2012-12-01

196

Joint estimation of shape and deformation for the detection of lesions in dynamic contrast-enhanced breast MRI.  

PubMed

We propose a mathematical framework for simultaneously delineating the boundary of object and estimating its temporal motion in the application of lesion detection in a dynamic contrast-enhanced (DCE) breast MRI sequence where both the appearance and the shape of region of interest is assumed to change in time. A unified energy functional for a joint segmentation and registration is proposed based on the assumption that the statistical properties of dynamic intensity curves within a region of interest are homogeneous. Our algorithm is designed to provide the morphological properties of the enhanced region and its dynamic intensity profiles, called kinetic signatures, in the analysis of DCE imagery since these features are considered as significant cues in understanding images. The proposed energy comprises a combination of a segmentation energy and a registration energy. The segmentation energy is developed based on a convex formulation being insensitive to the initialization. The registration energy is designed to compensate motion artifacts that are usually involved in the temporal imaging procedure. The major objective of this work is to provide a mathematical framework for a joint segmentation and registration on a dynamic sequence of images, and we demonstrate the mutual benefit of the estimation of temporal deformations for the registration step and the localization of regions of interest for the segmentation step. The effectiveness of the developed algorithm has been demonstrated on a number of clinical DCE breast MRI data in the application of breast lesion detection and the results show its potential to improve the accuracy and the efficiency in the diagnosis of breast cancer. PMID:24140912

Hong, Byung-Woo

2013-10-18

197

Joint estimation of shape and deformation for the detection of lesions in dynamic contrast-enhanced breast MRI  

NASA Astrophysics Data System (ADS)

We propose a mathematical framework for simultaneously delineating the boundary of object and estimating its temporal motion in the application of lesion detection in a dynamic contrast-enhanced (DCE) breast MRI sequence where both the appearance and the shape of region of interest is assumed to change in time. A unified energy functional for a joint segmentation and registration is proposed based on the assumption that the statistical properties of dynamic intensity curves within a region of interest are homogeneous. Our algorithm is designed to provide the morphological properties of the enhanced region and its dynamic intensity profiles, called kinetic signatures, in the analysis of DCE imagery since these features are considered as significant cues in understanding images. The proposed energy comprises a combination of a segmentation energy and a registration energy. The segmentation energy is developed based on a convex formulation being insensitive to the initialization. The registration energy is designed to compensate motion artifacts that are usually involved in the temporal imaging procedure. The major objective of this work is to provide a mathematical framework for a joint segmentation and registration on a dynamic sequence of images, and we demonstrate the mutual benefit of the estimation of temporal deformations for the registration step and the localization of regions of interest for the segmentation step. The effectiveness of the developed algorithm has been demonstrated on a number of clinical DCE breast MRI data in the application of breast lesion detection and the results show its potential to improve the accuracy and the efficiency in the diagnosis of breast cancer.

Hong, Byung-Woo

2013-11-01

198

Enhanced brain connectivity in math-gifted adolescents: An fMRI study using mental rotation  

Microsoft Academic Search

Mathematical giftedness is a form of intelligence related to enhanced mathematical reasoning that can be tested using a variety of numerical and spatial tasks. A number of neurobiological mechanisms related to exceptional mathematical reasoning ability have been postulated, including enhanced brain connectivity. We aimed to further investigate this possibility by comparing a group of mathematically gifted adolescents with an average

James Prescott; Maria Gavrilescu; Ross Cunnington; Michael W. OBoyle; Gary F. Egan

2010-01-01

199

Semi-parametric analysis of dynamic contrast-enhanced MRI using Bayesian P-splines.  

PubMed

Current approaches to quantitative analysis of DCE-MRI with non-linear models involve the convolution of an arterial input function (AIF) with the contrast agent concentration at a voxel or regional level. Full quantification provides meaningful biological parameters but is complicated by the issues related to convergence, (de-)convolution of the AIF, and goodness of fit. To overcome these problems, this paper presents a penalized spline smoothing approach to model the data in a semi-parametric way. With this method, the AIF is convolved with a set of B-splines to produce the design matrix, and modeling of the resulting deconvolved biological parameters is obtained in a way that is similar to the parametric models. Further kinetic parameters are obtained by fitting a non-linear model to the estimated response function and detailed validation of the method, both with simulated and in vivo data is PMID:17354949

Schmid, Volker J; Whitcher, Brandon; Yang, Guang-Zhong

2006-01-01

200

In vivo evaluation of retinal and callosal projections in early postnatal development and plasticity using manganese-enhanced MRI and diffusion tensor imaging  

Microsoft Academic Search

The rodents are an excellent model for understanding the development and plasticity of the visual system. In this study, we explored the feasibility of Mn-enhanced MRI (MEMRI) and diffusion tensor imaging (DTI) at 7T for in vivo and longitudinal assessments of the retinal and callosal pathways in normal neonatal rodent brains and after early postnatal visual impairments. Along the retinal

Kevin C. Chan; Joe S. Cheng; Shujuan Fan; Iris Y. Zhou; Jian Yang; Ed X. Wu

201

Nerve root enhancement on spinal MRI in pediatric Guillain-Barré syndrome.  

PubMed

Guillain-Barré syndrome diagnosis is based on clinical presentation and supportive diagnostic testing. In its early stage, no single, reliable diagnostic test is available. However, a finding of nerve root enhancement on spinal magnetic resonance imaging may be useful. We evaluated the frequency of nerve root enhancement on spinal magnetic resonance imaging in children with Guillain-Barré syndrome. At a single tertiary pediatric center, we conducted a retrospective chart review of children with Guillain-Barré syndrome who had complete spinal or lumbosacral spinal magnetic resonance imaging with gadolinium administration from January 2002-January 2009. Twenty-four consecutive patients were identified. Spinal nerve root enhancement with gadolinium was present in 92% (22/24) of children with Guillain-Barré syndrome on initial spinal magnetic resonance imaging (95% confidence interval, 0.745-0.978). This finding increased to 100% of patients, after two patients underwent repeat spinal magnetic resonance imaging that did reveal nerve root enhancement. Patterns of enhancement were variable, but involved the thoracolumbar nerve roots in all patients. Enhancement of nerve roots with gadolinium on initial spinal magnetic resonance imaging was frequently present in these children with Guillain-Barré syndrome. Spinal magnetic resonance imaging is a sensitive diagnostic test and should be considered an additional diagnostic tool in select cases. PMID:20837305

Mulkey, Sarah B; Glasier, Charles M; El-Nabbout, Bassem; Walters, William D; Ionita, Christian; McCarthy, Michael H; Sharp, Gregory B; Shbarou, Rolla M

2010-10-01

202

Breast Cancer Detected on an Incident (Second or Subsequent) Round of Screening MRI: MRI Features of False-Negative Cases.  

PubMed

OBJECTIVE. The purpose of this article is to evaluate the nature of breast cancers detected in the incident round of screening MRI to determine MRI features of early breast cancer. MATERIALS AND METHODS. From 2003 to 2012, there were 16 incident breast cancers in 15 patients on screening MRI, including nine cancers that were retrospectively identifiable on the prior MRI (false-negative [FN] cancers at prior screening examination). We evaluated the BI-RADS features of these incident cancers in previous and current MRI scans. RESULTS. Of 16 incident cancers, there were 11 mass lesions (69%), three foci (19%), and two nonmasslike enhancement lesions (13%). Of the nine FN cancers (five foci, two masses, and two nonmasslike enhancement lesions), all showed increases in size on the current examination (median, 80% increase); four lesions showed rapid uptake kinetics on prior examinations, and five lesions showed a change in kinetic pattern from slow to rapid uptake. Among the five foci, one focus was isolated and four foci were in a background of other foci, where two foci could be distinguished for their higher signal intensity. CONCLUSION. On screening MRI, any lesion that increases in size, has rapid uptake kinetics or a change in kinetic pattern, or is an isolated focus or focus showing more enhancement than other foci should be viewed with a high degree of suspicion, and a biopsy should be considered. PMID:24147491

Yamaguchi, Ken; Schacht, David; Newstead, Gillian M; Bradbury, Angela R; Verp, Marion S; Olopade, Olufunmilayo I; Abe, Hiroyuki

2013-11-01

203

Combination of model-free and model-based analysis of dynamic contrast enhanced MRI for breast cancer diagnosis  

NASA Astrophysics Data System (ADS)

Dynamic contrast enhancement (DCE) is the leading technique in magnetic resonance imaging for cancer detection and diagnosis. However, there are large variations in the reported sensitivity and specificity of this method that result from the wide range of contrast-enhanced MRI sequences and protocols, image processing methods, and interpretation criteria. Analysis methods can be divided to physiological based models that take into account the vascular and tissue specific features that influence tracer perfusion, and to model free algorithms that decompose enhancement patterns in order to segment and classify different tissue types. Inhere we present a general hybrid method for analyzing dynamic contrast enhanced images integrating a mathematical, model-free technique with a model derived approach that characterizes tissue microvasculature function. We demonstrate the application of the method for breast cancer diagnosis. A brief description of this approach was recently presented for the diagnosis of prostate cancer. The model free method employed principal component analysis and yielded eigen-vectors of which two were relevant for characterizing breast malignancy. The physiological relevance of the two eigen-vectors was revealed by a quantitative correlation with the model based three time point technique. Projection maps of the eigen-vector that specifically related to the wash-out rate of the contrast agent depicted with high accuracy breast cancer. Overall, this hybrid method is fast, standardized, and yields parametric images characterizing tissue microvascular function. It can improve breast cancer detection and be potentially extended as a computer-aided tool for the detection and diagnosis of other cancers.

Eyal, E.; Furman-Haran, E.; Badikhi, D.; Kelcz, F.; Degani, H.

2008-04-01

204

Positive MRI contrast enhancement in THP-1 cells with Gd2O3 nanoparticles.  

PubMed

There is a demand for more efficient and tissue-specific MRI contrast agents and recent developments involve the design of substances useful as molecular markers and magnetic tracers. In this study, nanoparticles of gadolinium oxide (Gd2O3) have been investigated for cell labeling and capacity to generate a positive contrast. THP-1, a monocytic cell line that is phagocytic, was used and results were compared with relaxivity of particles in cell culture medium (RPMI 1640). The results showed that Gd2O3-labeled cells have shorter T1 and T2 relaxation times compared with untreated cells. A prominent difference in signal intensity was observed, indicating that Gd2O3 nanoparticles can be used as a positive contrast agent for cell labeling. The r1 for cell samples was 4.1 and 3.6 s(-1) mm(-1) for cell culture medium. The r2 was 17.4 and 12.9 s(-1) mm(-1), respectively. For r1, there was no significant difference in relaxivity between particles in cells compared to particles in cell culture medium, (p(r1) = 0.36), but r2 was significantly different for the two different series (p(r2) = 0.02). Viability results indicate that THP-1 cells endure treatment with Gd2O3 nanoparticles for an extended period of time and it is therefore concluded that results in this study are based on viable cells. PMID:18546094

Klasson, Anna; Ahrén, Maria; Hellqvist, Eva; Söderlind, Fredrik; Rosén, Anders; Käll, Per-Olov; Uvdal, Kajsa; Engström, Maria

205

Advanced methods for quantification of infarct size in mice using three-dimensional high-field late gadolinium enhancement MRI  

PubMed Central

Conventional methods to quantify infarct size after myocardial infarction in mice are not ideal, requiring either tissue destruction for histology or relying on nondirect measurements such as wall motion. We therefore implemented a fast, high-resolution method to directly measure infarct size in vivo using three-dimensional (3D) late gadolinium enhancement MRI (3D-LGE). Myocardial T1 relaxation was quantified at 9.4 Tesla in five mice, and reproducibility was tested by repeat imaging after 5 days. In a separate set of healthy and infarcted mice (n = 8 of each), continuous T1 measurements were made following intravenous or intraperitoneal injection of a contrast agent (0.5 ?mol/g gadolinium-diethylenetriamine pentaacetic acid). The time course of T1 contrast development between viable and nonviable myocardium was thereby determined, with optimal postinjection imaging windows and inversion times identified. Infarct sizes were quantified using 3D-LGE and compared with triphenyltetrazolium chloride histology on day 1 after infarction (n = 8). Baseline myocardial T1 was highly reproducible: the mean value was 952 ± 41 ms. T1 contrast peaked earlier after intravenous injection than with intraperitoneal injection; however, contrast between viable and nonviable myocardium was comparable for both routes (P = 0.31), with adequate contrast remaining for at least 60 min postinjection. Excellent correlation was obtained between infarct sizes derived from 3D-LGE and histology (r = 0.91, P = 0.002), and Bland-Altman analysis indicated good agreement free from systematic bias. We have validated an improved 3D MRI method to noninvasively quantify infarct size in mice with unsurpassed spatial resolution and tissue contrast. This method is particularly suited to studies requiring early quantification of initial infarct size, for example, to measure damage before intervention with stem cells.

Bohl, Steffen; Lygate, Craig A.; Barnes, Hannah; Medway, Debra; Stork, Lee-Anne; Schulz-Menger, Jeanette; Neubauer, Stefan; Schneider, Jurgen E.

2009-01-01

206

Structural effect on degradability and in vivo contrast enhancement of polydisulfide Gd(III) complexes as biodegradable macromolecular MRI contrast agents  

PubMed Central

Structural effect of polydisulfide Gd(III) chelates on their in vitro degradability, and cardiovascular and tumor imaging in mice were evaluated as biodegradable macromolecular MRI contrast agents. Polydisulfide Gd(III) chelates, Gd-DTPA cystamine copolymers (GDCC), Gd-DTPA L-cystine copolymers (GDCP), Gd-DTPA D-cystine copolymers (dGDCP) and Gd-DTPA glutathione (oxidized) copolymers (GDGP), with different sizes and narrow molecular weight distribution were prepared and evaluated both in vitro and in vivo in mice bearing MDA-MB-231 tumor xenografts. Large steric hindrance around the disulfide bonds in GDGP resulted in greater T1 and T2 relaxivities than GDCC, GDCP and dGDCP. The degradability of the polydisulfide by the endogenous thiols decreased with an increase in steric effects around the disulfide bonds in the order of GDCC > GDCP, dGDCP > GDGP. The size and degradability of the contrast agents had significant impact on vascular contrast enhancement kinetics. The agents with large size and low degradability resulted in more prolonged vascular enhancement than the agents with small size and high degradability. It seems that the size and degradability of the agents did not significantly affect tumor enhancement. All agents resulted in significant contrast enhancement in tumor tissue. This study has demonstrated that the vascular enhancement kinetics of the polydisulfide MRI contrast agents can be controlled by their sizes and structures. The polydisulfide Gd(III) chelates are promising biodegradable macromolecular MRI contrast agents for MR angiography and cancer imaging.

Zong, Yuda; Wang, Xuli; Jeong, Eun-Kee; Parker, Dennis L.; Lu, Zheng-Rong

2009-01-01

207

Convection-enhanced delivery of maghemite nanoparticles: Increased efficacy and MRI monitoring  

Microsoft Academic Search

Convection-enhanced drug delivery (CED) is a novel approach to delivering drugs into brain tissue. Drugs are delivered continuously via a catheter, enabling large volume distributions of high drug concentrations with minimum systemic toxicity. Previously we demonstrated that CED formation\\/extent of small molecules may be significantly improved by increasing infusate viscosities. In this study we show that the same methodology can

Benny Perlstein; Zvi Ram; Dianne Daniels; Aharon Ocherashvilli; Yiftach Roth; Shlomo Margel; Yael Mardor

208

Impact of Repeated Topical-Loaded Manganese-Enhanced MRI on the Mouse Visual System  

PubMed Central

Purpose. Optic nerve degeneration in diseases such as glaucoma and multiple sclerosis evolves in months to years. The use of Mn2+-Enhanced Magnetic Resonance Imaging (MEMRI) in a time-course study may provide new insights into the disease progression. Previously, we demonstrated the feasibility of using a topical administration for Mn2+ delivery to the visual system. This study is to evaluate the impact of biweekly or monthly repeated Mn2+ topical administration and the pH levels of the Mn2+ solutions for MEMRI on the mouse visual pathway. Methods. Using groups of mice, the MEMRI with an acidic or pH neutralized 1 M MnCl2 solution was performed. To evaluate the feasibility of repeated MEMRIs, topical-loaded MEMRI was conducted biweekly seven times or monthly three times. The enhancement of MEMRI in the visual system was quantified. After repeated MEMRIs, the corneas were examined by optical coherence tomography. The retinal ganglion cells (RGCs) and optic nerves were examined by histology. Results. All mice exhibited consistent enhancements along the visual system following repeated MEMRIs. The acidic Mn2+ solution induced a greater MEMRI enhancement as compared with a neutral pH Mn2+ solution. Significant 20% RGC loss was found after three biweekly Mn2+ inductions, but no RGC loss was found after three monthly Mn2+ treatments. The corneal thickness was found increased after seven biweekly topical-loaded MEMRI. Conclusions. Acidic Mn2+ solutions enhanced the uptake of Mn2+ observed on the MEMRI. Increasing the time intervals of repeated Mn2+ topical administration reduced the adverse effects caused by MEMRI.

Sun, Shu-Wei; Thiel, Tiffany; Liang, Hsiao-Fang

2012-01-01

209

Pretreatment Diffusion-Weighted and Dynamic Contrast-Enhanced MRI for Prediction of Local Treatment Response in Squamous Cell Carcinomas of the Head and Neck  

PubMed Central

OBJECTIVE The objective of our study was to predict response to chemoradiation therapy in patients with head and neck squamous cell carcinoma (HNSCC) by combined use of diffusion-weighted imaging (DWI) and high-spatial-resolution, high-temporal-resolution dynamic contrast-enhanced MRI (DCE-MRI) parameters from primary tumors and metastatic nodes. SUBJECTS AND METHODS Thirty-two patients underwent pretreatment DWI and DCE-MRI using a modified radial imaging sequence. Postprocessing of data included motion-correction algorithms to reduce motion artifacts. The median apparent diffusion coefficient (ADC), volume transfer constant (Ktrans), extracellular extravascular volume fraction (ve), and plasma volume fraction (vp) were computed from primary tumors and nodal masses. The quality of the DCE-MRI maps was estimated using a threshold median chi-square value of 0.10 or less. Multivariate logistic regression and receiver operating characteristic curve analyses were used to determine the best model to discriminate responders from nonresponders. RESULTS Acceptable ?2 values were observed from 84% of primary tumors and 100% of nodal masses. Five patients with unsatisfactory DCE-MRI data were excluded and DCEMRI data for three patients who died of unrelated causes were censored from analysis. The median follow-up for the remaining patients (n = 24) was 23.72 months. When ADC and DCE-MRI parameters (Ktrans, ve, vp) from both primary tumors and nodal masses were incorporated into multivariate logistic regression analyses, a considerably higher discriminative accuracy (area under the curve [AUC] = 0.85) with a sensitivity of 81.3% and specificity of 75% was observed in differentiating responders (n = 16) from nonresponders (n = 8). CONCLUSION The combined use of DWI and DCE-MRI parameters from both primary tumors and nodal masses may aid in prediction of response to chemoradiation therapy in patients with HNSCC.

Chawla, Sanjeev; Kim, Sungheon; Dougherty, Lawrence; Wang, Sumei; Loevner, Laurie A.; Quon, Harry; Poptani, Harish

2013-01-01

210

Molecular imaging of tumors and metastases using chemical exchange saturation transfer (CEST) MRI.  

PubMed

The two glucose analogs 2-deoxy-D-glucose (2-DG) and 2-fluoro-2-deoxy-D-glucose (FDG) are preferentially taken up by cancer cells, undergo phosphorylation and accumulate in the cells. Owing to their exchangeable protons on their hydroxyl residues they exhibit significant chemical exchange saturation transfer (CEST) effect in MRI. Here we report CEST-MRI on mice bearing orthotopic mammary tumors injected with 2-DG or FDG. The tumor exhibited an enhanced CEST effect of up to 30% that persisted for over one hour. Thus 2-DG/FDG CEST MRI can replace PET/CT or PET/MRI for cancer research in laboratory animals, but also has the potential to be used in the clinic for the detection of tumors and metastases, distinguishing between malignant and benign tumors and monitoring tumor response to therapy as well as tumors metabolism noninvasively by using MRI, without the need for radio-labeled isotopes. PMID:24157711

Rivlin, Michal; Horev, Judith; Tsarfaty, Ilan; Navon, Gil

2013-10-25

211

On the Dark Rim Artifact in Dynamic Contrast-Enhanced MRI Myocardial Perfusion Studies  

PubMed Central

A dark band or rim along parts of the subendocardial border of the left ventricle (LV) and the myocardium has been noticed in some dynamic contrast-enhanced MR perfusion studies. The artifact is thought to be due to susceptibility effects from the gadolinium bolus, motion, or resolution, or a combination of these. Here motionless ex vivo hearts in which the cavity was filled with gadolinium are used to show that dark rim artifacts can be consistent with resolution effects alone.

Di Bella, E.V.R.; Parker, D.L.; Sinusas, A.J.

2008-01-01

212

MRI of atherosclerose  

Microsoft Academic Search

This thesis is aimed at visualization of atherosclerotic plaques with MRI. Noninvasive screening for subclinical atherosclerosis as well as detection of high-risk atherosclerotic plaque in an established population of cardiovascular patients is important for patient management. Anatomical MRI utilizing intrinsic contrast based on different MR relaxation properties of plaque components, contrast-enhanced MRI using non-targeted ultra-small particles of iron oxide (USPIOs)

B. C. M. te Boekhorst

2010-01-01

213

Power Doppler sonography with and without echo-enhancing contrast agent and contrast-enhanced MRI for the evaluation of rheumatoid arthritis of the shoulder joint: differentiation between synovitis and joint effusion  

Microsoft Academic Search

Objective. To evaluate patients with clinically active rheumatoid arthritis (RA) of the shoulder for joint effusion and synovitis using conventional sonography, power Doppler (PD) sonography with and without echo-enhancing contrast agent, and contrast-enhanced MRI.Design and patients. Twenty-four patients (mean age 64 years) with known RA had one symptomatic shoulder evaluated by conventional gray-scale sonography and PD sonography before and after intravenous

G. Wamser; K. Bohndorf; K. Vollert; W. Bücklein; J. Schalm

2003-01-01

214

Enhanced smoking cue salience associated with depression severity in nicotine-dependent individuals: a preliminary fMRI study.  

PubMed

The association between cigarette smoking and depression has been well documented; however, little research has been done to elucidate the neurobiological substrates of this highly prevalent comorbidity. We used multiple linear regression analysis to evaluate the relationship between depression severity as assessed by the Hamilton Depression Rating Scale (HAMD) and blood oxygen level-dependent (BOLD) responses to visual smoking cues in drug-free nicotine-dependent smokers (n=18). Two functional magnetic resonance imaging (fMRI) scans were completed over a single study day, following overnight smoking abstinence (pre-smoking scan) and after cigarette reinstatement (post-smoking scan). During the pre-smoking scan positive correlations between BOLD activity and HAMD scores were observed in areas of the mesocorticolimbic dopaminergic system [inferior frontal gyrus, middle frontal gyrus (MFG), hippocampus (HC), anterior cingulate gyrus] and areas of the visuospatial attention circuit (medial occipital lobe, middle cingulate cortex, superior frontal gyrus, angular gyrus). During the post-smoking scan positive correlations were observed in areas of the brain implicated in drug expectancy (MFG), memory (HC), attentional motivation (posterior cingulate cortex), and visual processing and attention (precuneus). These preliminary findings demonstrate that smokers with higher depression severity attribute greater incentive salience to smoking-related cues and this is especially pronounced during periods of acute abstinence. Such enhanced salience of smoking cues, even after smoking a cigarette, may play a critical role both in the maintenance of smoking in depression and in greater levels of nicotine dependence seen in this patient population. PMID:20604987

Kushnir, Vladyslav; Menon, Mahesh; Balducci, Xavier L; Selby, Peter; Busto, Usoa; Zawertailo, Laurie

2010-07-07

215

[A case of acute autonomic, sensory and motor neuropathy with swelling and gadolinium enhancement of bilateral trigeminal nerve on MRI and dissociation between superficial and deep sensation disturbance].  

PubMed

We report a case of a 46-year old man with acute autonomic, sensory and motor neuropathy (AASMN). He developed severe orthostatic hypotension, anuria,anhydrosis, tonic pupil with dysarthria, dysphagia, jaw claudication, and dysesthesia and sharp pain several days after symptom of upper respiratory infection. Neurological examination revealed severely decreased superficial sensation with normal deep sensation. Brain MRI findings showed bilateral trigeminal nerve swelling with gadolinium (Gd) enhancement. His motor and sensory symptoms and MRI abnormality were improved after the administration of intravenous immunoglobulin and intravenous methylprednisolone therapy; however his autonomic symptoms scarcely reacted to these immunotherapies. As long as we investigated in AASMN cases, bilateral trigeminal nerve swelling with Gd enhancement and dissociation between superficial and deep sensation disturbance have not reported, suggesting that the present case mainly disrupted C nerve fibers distributing postganglionic autonomic and temperature-pain sensory nerves. PMID:23470893

Naito, Hiroyuki; Doi, Hikaru; Inamizu, Saeko; Ito, Hijiri; Araki, Takehisa

2013-01-01

216

Infusion-based manganese-enhanced MRI: a new imaging technique to visualize the mouse brain  

PubMed Central

Manganese-enhanced magnetic resonance imaging is a technique that employs the divalent ion of the paramagnetic metal manganese (Mn2+) as an effective contrast agent to visualize, in vivo, the mammalian brain. As total achievable contrast is directly proportional to the net amount of Mn2+ accumulated in the brain, there is a great interest in optimizing administration protocols to increase the effective delivery of Mn2+ to the brain while avoiding the toxic effects of Mn2+ overexposure. In this study, we investigated outcomes following continuous slow systemic infusion of manganese chloride (MnCl2) into the mouse via mini-osmotic pump administration. The effects of increasing fractionated rates of Mn2+ infusion on signal enhancement in regions of the brain were analyzed in a three-treatment study. We acquired whole-brain 3-D T1-weighted images and performed region of interest quantitative analysis to compare mean normalized signal in Mn2+ treatments spanning 3, 7, or 14 days of infusion (rates of 1, 0.5, and 0.25 ?L/h, respectively). Evidence of Mn2+ transport at the conclusion of each infusion treatment was observed throughout the brains of normally behaving mice. Regions of particular Mn2+ accumulation include the olfactory bulbs, cortex, infralimbic cortex, habenula, thalamus, hippocampal formation, amygdala, hypothalamus, inferior colliculus, and cerebellum. Signals measured at the completion of each infusion treatment indicate comparable means for all examined fractionated rates of Mn2+ infusion. In this current study, we achieved a significantly higher dose of Mn2+ (180 mg/kg) than that employed in previous studies without any observable toxic effects on animal physiology or behavior.

Mok, Stephanie I.; Munasinghe, Jeeva P.; Young, W. S.

2011-01-01

217

Quantitative Diffusion Weighted Imaging and Dynamic Susceptibility-weighted Contrast-enhanced Perfusion MRI Analysis of T2-hypointense Lesion Components in Pediatric Diffuse Intrinsic Pontine Glioma  

PubMed Central

Background and Purpose Focal anaplasia in cerebral neoplasm has been found to be characterized by T2 hypointensity, signal enhancement on post-contrast T1-weighted images and restricted water diffusion.. We identified T2HOFs with these MRI characteristics in children with DIPG and hypothesized that those represent areas of focal anaplasia, hence may also exhibitid increased perfusion properties, therefore we used dynamic susceptibility-weighted perfusion MRI to support our hypothesis,. Materials and Methods We retrospectively reviewed the baseline MRI scans of 86 patients (48 girls, 37 boys, median age 6.1 years, range 1.1–17.6 years) treated for DIPG at our hospital (2004–2009). T2HOFs with the described MRI characteristics were identified in 10 patients. We used an ROI-based, quantitative multiparametric (ADC, FA, rCBV, rCBF, and rMTT) approach to compare the MRI properties of T2HOFs with those of the typical T2HRT. Results ADC was significantly lower in T2HOFswith the specified MRI characteristics compared to T2HRTs (range, 0.71 to 1.95 ?m2/ms vs. 1.36 to 2.13 ?m2/ms, P < .01) and FA (range, 0.12 to 0.34 vs. 0.07 to 0.24, P=.03) and rCBV (range, 0.4 to 2.62 vs. 0.23 to 1.57, P=.01) were significantly higher. Neither rCBF nor rMTT was significantly different between T2HOFs and T2HRTs. Conclusion Our data suggest that T2HOFs in DIPG may represent areas of focal anaplasia and underline the importance of regional, rather than global tumor field analysis in the diagnostic imaging workup of cerebral neoplasms and guidance for biopsy in particular.

Lobel, U.; Sedlacik, J.; Reddick, W.E.; Kocak, M.; Ji, Q.; Broniscer, A.; Hillenbrand, C.M.; Patay, Z.

2012-01-01

218

Ferucarbotran (Resovist): a new clinically approved RES-specific contrast agent for contrast-enhanced MRI of the liver: properties, clinical development, and applications  

Microsoft Academic Search

.   Ferucarbotran (Resovist) is the second clinically approved superparamagnetic iron oxide developed for contrast-enhanced MRI\\u000a of the liver. The purpose of this review is to provide an overview on the properties, clinical development, and application\\u000a of ferucarbotran. Safety data obtained during clinical phases I–III revealed a total of 162 adverse events within 1053 patients,\\u000a of which 75 were classified as

Peter Reimer; Thomas Balzer

2003-01-01

219

Dynamic Contrast-Enhanced and Diffusion MRI Show Rapid and Dramatic Changes in Tumor Microenvironment in Response to Inhibition of HIF-1? Using PX478  

Microsoft Academic Search

PX-478 is a new agent known to inhibit the hypoxia- responsivetranscriptionfactor,HIF-1A,inexperimental tumors. The current study was undertaken in prepa- ration for clinical trials to determine which noninvasive imaging endpoint(s) is sensitive to this drug's actions. Dynamic contrast-enhanced (DCE) and diffusion- weighted (DW) magnetic resonance imaging (MRI) were used to monitor acute effects on tumor hemo- dynamics and cellularity, respectively. Mice

Bénédicte F. Jordan; Matthew Runquist; Natarajan Raghunand; Amanda Baker; Ryan Williams; Lynn Kirkpatrickb; Garth Powis; Robert J. Gillies

2005-01-01

220

Manganese-enhanced MRI detected the gray matter lesions in the late phase of mild hypoxic-ischemic injury in neonatal rat  

Microsoft Academic Search

This study aims to use manganese-enhanced MRI (MEMRI) to investigate the progression and permanence of the gray matter injuries in a neonatal rat model by mild hypoxic-ischemia (H-I) insult. Histological analyses were performed using staining for Mn superoxide dismutase (Mn-SOD) and glutamine synthetase (GS), which are Mn-binding enzymes against oxidative stress and glutamate excitotoxicity in neurodegeneration, and the standard hematoxylin

Jian Yang; Ed X. Wu

2007-01-01

221

Diagnostic efficacy of gadoxetic acid (Primovist)-enhanced MRI and spiral CT for a therapeutic strategy: comparison with intraoperative and histopathologic findings in focal liver lesions  

Microsoft Academic Search

A multicenter study has been employed to evaluate the diagnostic efficacy of magnetic resonance imaging (MRI) using the new\\u000a liver-specific contrast agent gadoxetic acid (Gd-EOB-DTPA, Primovist), as opposed to contrast-enhanced biphasic spiral computed\\u000a tomography (CT), in the diagnosis of focal liver lesions, compared with a standard of reference (SOR). One hundred and sixty-nine\\u000a patients with hepatic lesions eligible for surgery

Renate Hammerstingl; Alexander Huppertz; Josy Breuer; Thomas Balzer; Anthony Blakeborough; Rick Carter; Lluis Castells Fusté; Gertraud Heinz-Peer; Werner Judmaier; Michael Laniado; Riccardo M. Manfredi; Didier G. Mathieu; Dieter Müller; Koenraad Mortelè; Peter Reimer; Maximilian F. Reiser; Philip J. Robinson; Kohkan Shamsi; Michael Strotzer; Matthias Taupitz; Bernd Tombach; Gianluca Valeri; Bernhard E. van Beers; Thomas J. Vogl

2008-01-01

222

Evaluation of femoral head vascularization in slipped capital femoral epiphysis before and after cannulated screw fixation with use of contrast-enhanced MRI: initial results  

Microsoft Academic Search

In this study we used contrast-enhanced magnetic resonance imaging (MRI) to evaluate the vascularization of the femoral head\\u000a in children with slipped capital femoral epiphysis (SCFE) before and after cannulated screw fixation. Eleven consecutive children\\u000a with SCFE, seven boys and four girls, aged 10–15 years were included in the study. There were no preslips; four children had\\u000a acute, three acute-on-chronic, and

G. Staatz; D. Honnef; A. Kochs; C. Hohl; T. Schmidt; H. Röhrig; R. W. Günther

2007-01-01

223

Optimization of a fuzzy C-means approach to determining probability of lesion malignancy and quantifying lesion enhancement heterogeneity in breast DCE-MRI  

NASA Astrophysics Data System (ADS)

Previous research has shown that a fuzzy C-means (FCM) approach to computerized lesion analysis has the potential to aid radiologists in the interpretation of dynamic contrast-enhanced MRI (DCE-MRI) breast exams. 1, 2 Our purpose in this study was to optimize the performance of the FCM approach with respect to binary (benign/malignant) breast lesion classification in DCE-MRI. We used both raw (calculated from kinetic data points) and empirically fitted3 kinetic features for this study. FCM was used to automatically select a characteristic kinetic curve (CKC) based on intensity-time point data of voxels within each lesion, using four different kinetic criteria: (1) maximum initial enhancement, (2) minimum shape index, (3) maximum washout, and (4) minimum time to peak. We extracted kinetic features from these CKCs, which were merged using linear discriminant analysis (LDA), and evaluated with receiver operating characteristic (ROC) analysis. There was comparable performance for methods 1, 2, and 4, while method 3 was inferior. Next, we modified use of the FCM method by calculating a feature vector for every voxel in each lesion and using FCM to select a characteristic feature vector (CFV) for each lesion. Using this method, we achieved performance similar to the four CKC methods. Finally, we generated lesion color maps using FCM membership matrices, which facilitated the visualization of enhancing voxels in a given lesion.

Bancroft Brown, Jeremy; Giger, Maryellen L.; Bhooshan, Neha; Newstead, Gillian; Jansen, Sanaz

2010-03-01

224

Phase Differential Enhancement of FLIM to Distinguish FRET Components of a Biosensor for Monitoring Molecular Activity of Membrane Type 1 Matrix Metalloproteinase in Live Cells  

PubMed Central

Fluorescence lifetime-resolved imaging microscopy (FLIM) has been used to monitor the enzymatic activity of a proteolytic enzyme, Membrane Type 1 Matrix Metalloproteinase (MT1-MMP), with a recently developed FRET-based biosensor in vitro and in live HeLa and HT1080 cells. MT1-MMP is a collagenaise that is involved in the destruction of extra-cellular matrix (ECM) proteins, as well as in various cellular functions including migration. The increased expression of MT1-MMP has been positively correlated with the invasive potential of tumor cells. However, the precise spatiotemporal activation patterns of MT1-MMP in live cells are still not well-established. The activity of MT1-MMP was examined with our biosensor in live cells. Imaging of live cells was performed with full-field frequency-domain FLIM. Image analysis was carried out both with polar plots and phase differential enhancement. Phase differential enhancement, which is similar to phase suppression, is shown to facilitate the differentiation between different conformations of the MT1-MMP biosensor in live cells when the lifetime differences are small. FLIM carried out in differential enhancement or phase suppression modes, requires only two acquired phase images, and permits rapid imaging of the activity of MT1-MMP in live cells.

Eichorst, John Paul; Huang, He

2012-01-01

225

Identifying Terminal Distinguishable Languages  

Microsoft Academic Search

We discuss new efficient learning algorithms for certain subclasses of regular and even linear languages based on the notion of terminal distinguishability introduced by Radhakrishnan and Nagaraja. The learning model we use is identification in the limit from positive samples as proposed by Gold and further studied by Angluin and many others. All classes we introduce in this paper are

Henning Fernau

2004-01-01

226

[3 T MRI imaging methods in the study of contrast-enhanced Adamkiewicz Artery].  

PubMed

Contrast enhanced magnetic resonance angiography (CE-MRA) is a common method for imaging the Adamkiewicz Artery (AKA). Test-bolus imaging methods have long been the mainstream, and recently, a time resolved technique (4D-MRA) is also reported. However, the current rates of detection for both are mixed, and the best method has not been established yet. For AKA, the present rate is 72% left, Th8?L1 91% that exists between, with a vessel diameter of 0.5 to 1.5 mm. Additionally, the AKA branch is known to have large individual differences, and thus, a wide range of high spatial resolution imaging. At our institution from January 2009, a 3 T system is installed, and 4D-MRA (time-resolved angiography with interleaved stochastic trajectories: TWIST) imaging became possible. TWIST is a sequence to balance the temporal resolution and spatial resolution, and is considered optimal for the imaging of AKA. In accordance with this idea, the first group of seven patients was imaged by TWIST, but in all cases, the results were not depicting AKA. In subsequent cases, the technique was changed to a 3D-gradient echo sequence with a Bolus-tracking method (Care bolus), and good results were obtained. In conclusion, AKA TWIST was not thought to depict the relationship between specific parameters. When using TWIST for imaging AKA, we will need to find out why it was not visualized, by examining AKA with simulated vessel phantoms, TWIST and Care Bolus. Furthermore, we report on our visual evaluation of the Retrospective clinical pictures. PMID:21282914

Hirata, Keiya; Takahashi, Masaru; Chikakoshi, Saeko; Nakamura, Eisui; Nishio, Hiroshi

2010-12-20

227

Methanol poisoning: characteristic MRI findings.  

PubMed

Acute methanol intoxication is not an unusual poisoning. It can have serious neurological sequelae. We emphasize how neuroimaging can help in distinguishing methanol poisoning from other causes of acute unconsciousness in alcoholic patients such as hypoglycemic brain damage and carbon monoxide poisoning or head injury, which are frequently observed in alcoholic patients and are also responsible for altered sensorium. The most important findings in MR brain imaging in methanol poisoning have been bilateral putaminal hemorrhagic necrosis. Other less common findings are subcortical and deep white matter lesions, cerebral and cerebellar cortical lesions, and midbrain lesions, cerebral and intraventricular hemorrhage, and even enhancement of necrotic lesions, we found almost the entire spectrum of MRI findings in this patient with methanol poisoning. Neurological sequelae can entail the course and prognosis in methanol poisoning. The patient died because of ventilator-associated pneumonia that developed in the course of prolonged hospitalization. PMID:22634487

Jain, Nirdesh; Himanshu, Dandu; Verma, Shailendra Prasad; Parihar, Anit

228

Visualization and quantification of whole rat heart laminar structure using high-spatial resolution contrast-enhanced MRI  

PubMed Central

It has been shown by histology that cardiac myocytes are organized into laminae and this structure is important in function, both influencing the spread of electrical activation and enabling myocardial thickening in systole by laminar sliding. We have carried out high-spatial resolution three-dimensional MRI of the ventricular myolaminae of the entire volume of the isolated rat heart after contrast perfusion [dimeglumine gadopentate (Gd-DTPA)]. Four ex vivo rat hearts were perfused with Gd-DTPA and fixative and high-spatial resolution MRI was performed on a 9.4T MRI system. After MRI, cryosectioning followed by histology was performed. Images from MRI and histology were aligned, described, and quantitatively compared. In the three-dimensional MR images we directly show the presence of laminae and demonstrate that these are highly branching and are absent from much of the subepicardium. We visualized these MRI volumes to demonstrate laminar architecture and quantitatively demonstrated that the structural features observed are similar to those imaged in histology. We showed qualitatively and quantitatively that laminar architecture is similar in the four hearts. MRI can be used to image the laminar architecture of ex vivo hearts in three dimensions, and the images produced are qualitatively and quantitatively comparable with histology. We have demonstrated in the rat that: 1) laminar architecture is consistent between hearts; 2) myolaminae are absent from much of the subepicardium; and 3) although localized orthotropy is present throughout the myocardium, tracked myolaminae are branching structures and do not have a discrete identity.

Benoist, David; Benson, Alan P.; White, Ed; Tanner, Steven F.; Holden, Arun V.; Dobrzynski, Halina; Bernus, Olivier; Radjenovic, Aleksandra

2012-01-01

229

Phase-based arterial input function measurements in the femoral arteries for quantification of dynamic contrast-enhanced (DCE) MRI and comparison with DCE-CT.  

PubMed

Dynamic contrast-enhanced (DCE) MRI is useful for diagnosis, treatment monitoring and follow-up of prostate cancer. However, large differences have been reported in the parameter range of the transfer constant K(trans) , making longitudinal studies and comparison of DCE-MRI findings between studies difficult. Large part of this inconsistency in K(trans) values can be attributed to problems with the accurate measurement of the arterial input function (AIF) from the magnitude signal (AIF(MAG) (N) ). Phase-based AIF measurements (AIF(PHASE) ) have been proposed as a more robust alternative to AIF(MAG) (N) measurements. This study compares AIF(PHASE) with AIFs measured with DCE-CT (AIF(CT) ), and the corresponding K(trans) maps in 12 prostate cancer patients. The shape of AIF(PHASE) and AIF(CT) are similar, although differences in the peak height and peak width exist as a result of differences in injection protocol. No significant differences in K(trans) values were found between the DCE-MRI and DCE-CT exams, with median K(trans) values of 0.10 and 0.08 min(-1) for healthy peripheral zone tissue and 0.44 and 0.36 min(-1) for regions suspected of tumor respectively. Therefore, robust quantification of K(trans) values from DCE-MRI exams in the cancerous prostate is feasible with the use of AIF(PHASE) . PMID:21604291

Korporaal, Johannes G; van den Berg, Cornelis A T; van Osch, Matthias J P; Groenendaal, Greetje; van Vulpen, Marco; van der Heide, Uulke A

2011-05-20

230

Self-Gated CINE MRI for Combined Contrast-Enhanced Imaging and Wall-Stiffness Measurements of Murine Aortic Atherosclerotic Lesions  

PubMed Central

Background High-resolution contrast-enhanced imaging of the murine atherosclerotic vessel wall is difficult due to unpredictable flow artifacts, motion of the thin artery wall and problems with flow suppression in the presence of a circulating contrast agent. Methods and Results We applied a 2D-FLASH retrospective-gated CINE MRI method at 9.4T to characterize atherosclerotic plaques and vessel wall distensibility in the aortic arch of aged ApoE?/? mice after injection of a contrast agent. The method enabled detection of contrast enhancement in atherosclerotic plaques in the aortic arch after I.V. injection of micelles and iron oxides resulting in reproducible plaque enhancement. Both contrast agents were taken up in the plaque, which was confirmed by histology. Additionally, the retrospective-gated CINE method provided images of the aortic wall throughout the cardiac cycle, from which the vessel wall distensibility could be calculated. Reduction in plaque size by statin treatment resulted in lower contrast enhancement and reduced wall stiffness. Conclusions The retrospective-gated CINE MRI provides a robust and simple way to detect and quantify contrast enhancement in atherosclerotic plaques in the aortic wall of ApoE?/? mice. From the same scan, plaque-related changes in stiffness of the aortic wall can be determined. In this mouse model, a correlation between vessel wall stiffness and atherosclerotic lesions was found.

den Adel, Brigit; van der Graaf, Linda M.; Strijkers, Gustav J.; Lamb, Hildo J.; Poelmann, Robert E.; van der Weerd, Louise

2013-01-01

231

First-Pass Contrast-Enhanced Myocardial Perfusion MRI in Mice on a 3-T Clinical MR Scanner  

PubMed Central

First-pass contrast-enhanced myocardial perfusion MRI in rodents has so far not been possible due to the temporal and spatial resolution requirements. We developed a new first-pass perfusion MR method for rodent imaging on a clinical 3.0-T scanner (Philips Healthcare, Best, The Netherlands) that employed 10-fold k-space and time domain undersampling with constrained image reconstruction, using temporal basis sets (k-t principle component analysis) to achieve a spatial resolution of 0.2 × 0.2 × 1.5mm3 and an acquisition window of 43 msec. The method was successfully tested in five healthy and four infarcted mice (C57BL/6J) at heart rates of 495.1 ± 45.8 beats/min. Signal-intensity-time profiles showed a percentage myocardial signal increase of 141.3 ± 38.9% in normal mice, compared with 44.7 ± 32.4% in infarcted segments. Mean myocardial blood flow by Fermi function for constrained deconvolution in control mice was 7.3 ± 1.5 mL/g/min, comparable to published literature, with no significant differences between three myocardial segments. In infarcted segments, myocardial blood flow was significantly reduced to 1.2 ± 0.8 mL/g/min (P < 0.01). This is the first report of first-pass myocardial perfusion MR in a mouse model on a clinical 3-T MR scanner and using a k-t undersampling method. Data were acquired on a 3-T scanner, using an approach similar to clinical acquisition protocols, thus facilitating translation of imaging findings between rodent and human studies. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.

Makowski, Marcus; Jansen, Christian; Webb, Ian; Chiribiri, Amedeo; Nagel, Eike; Botnar, Rene; Kozerke, Sebastian; Plein, Sven

2010-01-01

232

Manganese-enhanced MRI of layer-specific activity in the visual cortex from awake and free-moving rats.  

PubMed

Cortical responses to visual stimulation have been studied extensively in the rodent, but often require post-stimulation ex vivo examination of the tissue. Here, we test the hypothesis that visual stimulus-dependent cortical activity from awake and free-moving rats can be encoded following systemically administered MnCl(2), and activity subsequently readout using manganese-enhanced MRI (MEMRI), a technique that can be performed without sacrificing the animal. Unanesthetized Sprague-Dawley rats, with or without systemic injection of MnCl(2), were maintained for 8 h in either a visually stimulating environment or darkness. To identify vision-dependent changes in cortical activity, animals were anesthetized and cortices were examined by 3D RARE MEMRI. Mean signal intensities in sub-cortical regions (e.g., superior colliculus and the lateral geniculate), and cortical regions (primary and accessory visual cortices) were compared. Cortex linearization was performed to aid in layer-specific signal intensity comparisons. Manganese administration alone globally increased signal intensity in the brain (P<0.0001). In visually stimulated and unstimulated rats, layer-specific analysis revealed that stimulated rats had on average significantly (P<0.05) higher signal intensities in layers IV and V of the primary visual cortex, as well as in deeper portions of the superficial superior colliculus, relative to dark adapted rats. Such differences went undetected without layer-specific analysis. We demonstrate, for the first time, the feasibility of layer-specific stimulus-dependant non-invasive MEMRI readout after encoding activity in awake and free moving rats. Future MEMRI studies are envisioned that measure the effects on cortical activity of sensory stimulation, as well as normal development, disease, plasticity, and therapy in longitudinal studies. PMID:19015035

Bissig, David; Berkowitz, Bruce A

2008-10-29

233

Quantification of microvascular cerebral blood flux and late-stage tumor compartmentalization in 9L gliosarcoma using flow enhanced MRI.  

PubMed

Measurements of tumor microvasculature are important to obtain an understanding of tumor angiogenesis and for the evaluation of therapies. In this work, we characterize the evolution of the microvascular flux at different stages of tumor growth in the 9L rat brain tumor model. The absolute quantification of cerebral blood flux is achieved with MRI at 7 T using the flow enhanced signal intensity (FENSI) method. FENSI flux maps were obtained between 5 and 14 days after glioma cell inoculation. Based on cerebral blood flux maps, we highlighted two main stages of tumor growth, below and above 3 mm, presenting distinct flux patterns and vascular properties. No significant difference emerged from the group analysis performed on the data collected at an early developmental stage (tumor size??3 mm), we observed a significant decrease in the cerebral blood flux inside the gliosarcoma (-33%, p?

Reynaud, Olivier; Geffroy, Françoise; Ciobanu, Luisa

2013-01-21

234

Heterogeneity of Intramural Function in Hypertrophic Cardiomyopathy: Mechanistic Insights from MRI Late Gadolinium Enhancement and High-resolution DENSE Strain Maps  

PubMed Central

Background In HCM, myocardial abnormalities are commonly heterogeneous. Two patterns of LGE have been reported: a bright “confluent” and an intermediate intensity abnormality termed “diffuse,” each representing different degrees of myocardial scarring. We used MRI to study the relation between intramural cardiac function and the extent of fibrosis in HCM. The aim of this study was to determine whether excess collagen or myocardial scarring, as determined by late gadolinium enhancement (LGE) MRI, are the primary mechanisms leading to heterogeneous regional contractile function in patients with hypertrophic cardiomyopathy (HCM). Methods and Results Intramural left ventricular (LV) strain, transmural LV function, and regions of myocardial fibrosis/scarring were imaged in 22 patients with HCM using displacement encoding with stimulated echoes (DENSE), cine MRI and LGE. DENSE systolic strain maps were qualitatively and quantitatively compared with LGE images. Intramural systolic strain by DENSE was significantly depressed within areas of confluent and diffuse LGE but also in the core of the most hypertrophic non-enhanced segment (all p<0.001 vs. non-hypertrophied segments). DENSE demonstrated an unexpected inner rim of largely preserved contractile function and a non-contracting outer wall within hypertrophic segments in 91% of patients. Conclusions LGE predicted some but not all of the heterogeneity of intramural contractile abnormalities. This indicates that myocardial scarring or excess interstitial collagen deposition does not fully explain the observed contractile heterogeneity in HCM. Thus, myofibril disarray or other non-fibrotic processes affect systolic function in a large number of patients with HCM.

Aletras, Anthony H.; Tilak, Gauri S.; Hsu, Li-Yueh; Arai, Andrew E.

2012-01-01

235

Quantitative assessment of regional cerebral blood flow by dynamic susceptibility contrast-enhanced MRI, without the need for arterial blood signals  

NASA Astrophysics Data System (ADS)

In dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI), an arterial input function (AIF) is usually obtained from a time-concentration curve (TCC) of the cerebral artery. This study was aimed at developing an alternative technique for reconstructing AIF from TCCs of multiple brain regions. AIF was formulated by a multi-exponential function using four parameters, and the parameters were determined so that the AIF curves convolved with a model of tissue response reproduced the measured TCCs for 20 regions. Systematic simulations were performed to evaluate the effects of possible error sources. DSC-MRI and positron emission tomography (PET) studies were performed on 14 patients with major cerebral artery occlusion. Cerebral blood flow (CBF) images were calculated from DSC-MRI data, using our novel method alongside conventional AIF estimations, and compared with those from 15O-PET. Simulations showed that the calculated CBF values were sensitive to variations in the assumptions regarding cerebral blood volume. Nevertheless, AIFs were reasonably reconstructed for all patients. The difference in CBF values between DSC-MRI and PET was -2.2 ± 7.4 ml/100 g/min (r = 0.55, p < 0.01) for our method, versus -0.2 ± 8.2 ml/100 g/min (r = 0.47, p = 0.01) for the conventional method. The difference in the ratio of affected to unaffected hemispheres between DSC-MRI and PET was 0.07 ± 0.09 (r = 0.82, p < 0.01) for our method, versus 0.07 ± 0.09 (r = 0.83, p < 0.01) for the conventional method. The contrasts in CBF images from our method were the same as those from the conventional method. These findings suggest the feasibility of assessing CBF without arterial blood signals.

Enmi, Jun-ichiro; Kudomi, Nobuyuki; Hayashi, Takuya; Yamamoto, Akihide; Iguchi, Satoshi; Moriguchi, Tetsuaki; Hori, Yuki; Koshino, Kazuhiro; Zeniya, Tsutomu; Shah, Nadim Jon; Yamada, Naoaki; Iida, Hidehiro

2012-12-01

236

Noninvasive monitoring of radiotherapy-induced microvascular changes using dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) in a colorectal tumor model  

SciTech Connect

Purpose: To examine dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with a macromolecular contrast agent (P792) to visualize effects of radiotherapy (RT) on microvascular leakage in a colorectal cancer model. Methods and Materials: CC531 tumors were induced in WAG/Rij rats. DCE-MRI was performed before and 5 days after 5 x 5 Gy of RT and parametric maps generated of the endothelial transfer constant (K{sup trans} ) and the fractional interstitial space (V{sub e} ) according to the Tofts model. Tissue pO{sub 2} mapping was performed in each tumor core and rim before and after RT. Microvessel density (MVD), vascular endothelial growth factor (VEGF) expression, and pimonidazole hypoxia staining were compared with a control group of tumor-bearing rats. Results: Mean K{sup trans} and v{sub e} were significantly reduced after RT in all tumor regions. Mean pO{sub 2} was 6.8 mm Hg before RT vs. 7.7 mm Hg after RT (p < 0.001) in the tumor rim and 3.5 mm Hg before RT vs. 4.4 mm Hg after RT (p < 0.001) in the tumor core. Mean MVD in the tumor rim was 10.4 in the RT treated group vs. 16.9 in the control group (p = 0.061). VEGF expression was significantly higher in RT-treated rats. After RT, no correlation was found between DCE-MRI parameters and histologic parameters. A correlation was seen after RT between pO{sub 2} and K{sup trans} (r -0.57, p = 0.08) and between pO{sub 2} and v{sub e} (r = -0.65, p = 0.04). Conclusions: Dynamic contrast-enhanced-MRI with P792 allows quantification of microvascular changes in this colorectal model. RT significantly reduces neovascular leakage and enhances tissue oxygenation and VEGF expression. After RT, DCE-MRI parameters are related to tumor pO{sub 2}, but not to MVD or VEGF expression.

Ceelen, Wim [Department of Surgery, Ghent University Hospital, Ghent (Belgium)]. E-mail: Wim.ceelen@ugent.be; Smeets, Peter [Department of Radiology, Ghent University Hospital, Ghent (Belgium); Backes, Walter [Department of Radiology, Maastricht University Hospital, Maastricht (Netherlands); Van Damme, Nancy [Department of Gastroenterology, Ghent University Hospital, Ghent (Belgium); Boterberg, Tom [Department of Radiotherapy, Ghent University Hospital, Ghent (Belgium); Demetter, Pieter [Department of Pathology, Erasmus University Hospital, Brussels (Belgium); Bouckenooghe, Isabel [Department of Surgery, Ghent University Hospital, Ghent (Belgium); De Visschere, Marieke [Department of Surgery, Ghent University Hospital, Ghent (Belgium); Peeters, Marc [Department of Gastroenterology, Ghent University Hospital, Ghent (Belgium); Pattyn, Piet [Department of Surgery, Ghent University Hospital, Ghent (Belgium)

2006-03-15

237

Dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) for the assessment of Pc 4-sensitized photodynamic therapy of a U87-derived glioma model in the athymic nude rat  

NASA Astrophysics Data System (ADS)

Introduction: Dynamic Contrast-Enhanced-Magnetic Resonance Imaging (DCE-MRI) may provide a means of tracking the outcome of Pc 4-sensitized photodynamic therapy (PDT) in deeply placed lesions (e.g., brain tumors). We previously determined that 150 ?L of gadolinium (Gd-DTPA) produces optimal enhancement of U87-derived intracerebral tumors in an athymic nude rat glioma model. We wish to determine how consistently DCE-MRI enhancement will detect an increase in Gd-enhancement of these tumors following Pc 4-PDT. Methods: We injected 2.5 x 105 U87 cells into the brains of 6 athymic nude rats. After 7-8 days pre-Pc 4 PDT peri-tumor DCE-MRI images were acquired on a 7.0T microMRI scanner before and after administration of 150 ?L Gd. DCE-MRI scans were repeated on Days 11, 12, and 13 following Pc 4-PDT (Day 8 or 9). Results: Useful DCE-MRI data were obtained for these animals before and after Pc 4- PDT. In the pre-Pc 4-PDT DCE-MRI scans an average normalized peak Gd enhancement was observed in tumor tissue that was 1.297 times greater than baseline (0.035 Standard Error [SE]). The average normalized peak Gd enhancement in the tumor tissue in the scan following PDT (Day 11) was 1.537 times greater than baseline (0.036 SE), a statistically significant increase in enhancement (p = 0.00584) over the pre-PDT level. Discussion: A 150 ?L Gd dose appears to provide an unambiguous increase in signal indicating Pc 4-PDT-induced necrosis of the U87-derived tumor. Our DCEMRI protocol may allow the development of a clinically robust, unambiguous, non-invasive technique for the assessment of PDT outcome.

Anka, Ali; Thompson, Paul; Mott, Eric; Sharma, Rahul; Zhang, Ruozhen; Cross, Nathan; Sun, Jiayang; Flask, Chris A.; Oleinick, Nancy L.; Dean, David

2010-02-01

238

Visual spatial attention enhances the amplitude of positive and negative fMRI responses to visual stimulation in an eccentricity-dependent manner.  

PubMed

Endogenous visual spatial attention improves perception and enhances neural responses to visual stimuli at attended locations. Although many aspects of visual processing differ significantly between central and peripheral vision, little is known regarding the neural substrates of the eccentricity dependence of spatial attention effects. We measured amplitudes of positive and negative fMRI responses to visual stimuli as a function of eccentricity in a large number of topographically-organized cortical areas. Responses to each stimulus were obtained when the stimulus was attended and when spatial attention was directed to a stimulus in the opposite visual hemifield. Attending to the stimulus increased both positive and negative response amplitudes in all cortical areas we studied: V1, V2, V3, hV4, VO1, LO1, LO2, V3A/B, IPS0, TO1, and TO2. However, the eccentricity dependence of these effects differed considerably across cortical areas. In early visual, ventral, and lateral occipital cortex, attentional enhancement of positive responses was greater for central compared to peripheral eccentricities. The opposite pattern was observed in dorsal stream areas IPS0 and putative MT homolog TO1, where attentional enhancement of positive responses was greater in the periphery. Both the magnitude and the eccentricity dependence of attentional modulation of negative fMRI responses closely mirrored that of positive responses across cortical areas. PMID:23562388

Bressler, David W; Fortenbaugh, Francesca C; Robertson, Lynn C; Silver, Michael A

2013-04-03

239

Evaluation of Optimal Scan Delay for Gadoxetate Disodium-Enhanced Hepatic Arterial Phase MRI Using MR Fluoroscopic Triggering and Slow Injection Technique.  

PubMed

OBJECTIVE. The purpose of this article is to prospectively evaluate the optimal scan delay for gadoxetate disodium-enhanced hepatic arterial phase MRI of hypervascular hepatocellular carcinoma (HCC) using MR fluoroscopic triggering and a slow-injection technique. SUBJECTS AND METHODS. Sixty-three patients (37 men and 26 women; age range, 33-92 years; mean age, 68.2 years) underwent gadoxetate disodium-enhanced MRI; there were 33 hypervascular HCCs (size range, 8-57 mm; mean size, 19.8 mm) in 19 patients. The time from the start of contrast agent injection to its arrival in the abdominal aorta (time to arrival) and the time from contrast agent arrival to peak enhancement (time to peak) were determined using MR fluoroscopy using IV slow injection at 1 mL/s of contrast material and a saline chaser. All patients underwent four-phase whole-liver imaging with a 3D keyhole gradient-echo sequence during a single breath-hold immediately after confirmation of aortic peak enhancement. Delays from peak aortic enhancement to k-space filling were 5-9, 10-14, 15-19, and 20-28 seconds, respectively, in the four phases. Time to arrival, time to peak, and HCC-to-liver contrast were evaluated. RESULTS. The time to arrival (range, 11-24 seconds; mean, 16.2 seconds) and the time to peak (range, 3-10 seconds; mean, 6.8 seconds) showed considerable variation among patients. HCC-to-liver contrast peaked at the first phase in 58% of cases, at the second phase in 42% of cases, and at the third and fourth phases in 0% of cases. Mean HCC-to-liver contrast in the first and second phases was significantly higher than that in the third and fourth phases (p < 0.01). CONCLUSION. Optimal scan delays for imaging hypervascular HCCs with gadoxetate disodium-enhanced hepatic arterial phase MRI was 7-12 seconds after the peak aortic enhancement using a slow-injection protocol. PMID:23971449

Goshima, Satoshi; Kanematsu, Masayuki; Kondo, Hiroshi; Watanabe, Haruo; Kawada, Hiroshi; Moriyama, Noriyuki; Bae, Kyongtae T

2013-09-01

240

Automatic classification of scar tissue in late gadolinium enhancement cardiac MRI for the assessment of left-atrial wall injury after radiofrequency ablation  

NASA Astrophysics Data System (ADS)

Radiofrequency ablation is a promising procedure for treating atrial fibrillation (AF) that relies on accurate lesion delivery in the left atrial (LA) wall for success. Late Gadolinium Enhancement MRI (LGE MRI) at three months post-ablation has proven effective for noninvasive assessment of the location and extent of scar formation, which are important factors for predicting patient outcome and planning of redo ablation procedures. We have developed an algorithm for automatic classification in LGE MRI of scar tissue in the LA wall and have evaluated accuracy and consistency compared to manual scar classifications by expert observers. Our approach clusters voxels based on normalized intensity and was chosen through a systematic comparison of the performance of multivariate clustering on many combinations of image texture. Algorithm performance was determined by overlap with ground truth, using multiple overlap measures, and the accuracy of the estimation of the total amount of scar in the LA. Ground truth was determined using the STAPLE algorithm, which produces a probabilistic estimate of the true scar classification from multiple expert manual segmentations. Evaluation of the ground truth data set was based on both inter- and intra-observer agreement, with variation among expert classifiers indicating the difficulty of scar classification for a given a dataset. Our proposed automatic scar classification algorithm performs well for both scar localization and estimation of scar volume: for ground truth datasets considered easy, variability from the ground truth was low; for those considered difficult, variability from ground truth was on par with the variability across experts.

Perry, Daniel; Morris, Alan; Burgon, Nathan; McGann, Christopher; MacLeod, Robert; Cates, Joshua

2012-02-01

241

The Comparative Study of Ultrasonography, Contrast-Enhanced MRI, and 18F-FDG PET/CT for Detecting Axillary Lymph Node Metastasis in T1 Breast Cancer  

PubMed Central

Purpose A more noninvasive evaluation of axillary lymph node in breast cancer is one of the principal challenges of breast cancer treatment. To detect axillary lymph node metastasis (ALNM) in T1 breast cancer, we have compared the axillary ultrasonography (AUS), contrast-enhanced magnetic resonance imaging (cMRI), and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) to determine the most adequate test or a combination of tests. Methods Retrospectively, 349 T1 breast cancer patients who were preoperatively examined using AUS, cMRI, and PET/CT between 2008 and 2011 and whom underwent pathological evaluations of axillary lymph nodes were reviewed and analyzed. Results In total, 26.4% (92/349) of patients exhibited ALNM. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of AUS for determining ALNM were 44.6%, 88.7%, 58.6%, 81.7%, and 77.1%, respectively. cMRI was similar to AUS. The sensitivity, specificity, PPV, NPV, and accuracy of PET/CT were 44.5%, 94.2%, 73.2%, 82.6%, and 81.1%, respectively. The combination including cMRI and PET/CT was the most accurate with sensitivity, specificity, PPV, NPV, and accuracy values of 39.1%, 98.8%, 92.3%, 81.9%, and 83.1%, respectively. The mean number (3.5±4.2) of ALNMs in the patients who were positive based on cMRI and PET/CT and also pathologically proven to exhibit ALNM was significantly larger than the number (2.16±2.26) in other patients who exhibited ALNM (p=0.035). Conclusion There are no definitive modalities for detecting ALNM in T1 breast cancers to replace sentinel lymph node biopsy (SLNB). If ALNM is suspected based on cMRI and PET/CT, the axillary dissection without SLNB might be a better option because it is related to high possibilities of ALNM and large axillary metastatic volumes.

Hwang, Seung Ook; Lee, Sang-Woo; Kim, Hye Jung; Kim, Wan Wook; Park, Ho Yong

2013-01-01

242

Athletic injuries of the extensor carpi ulnaris subsheath: MRI findings and utility of gadolinium-enhanced fat-saturated T1-weighted sequences with wrist pronation and supination  

Microsoft Academic Search

Objective  To report the magnetic resonance imaging (MRI) findings in athletic injuries of the extensor carpi ulnaris (ECU) subsheath,\\u000a assessing the utility of gadolinium-enhanced (Gd) fat-saturated (FS) T1-weighted sequences with wrist pronation and supination.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Sixteen patients (13 male, three female; mean age 30.3 years) with athletic injuries of the ECU subsheath sustained between\\u000a January 2003 and June 2009 were included in this

Jeremy Jeantroux; Fabio Becce; Henri Guerini; Bernard Montalvan; Dominique Le Viet; Jean-Luc Drapé

2011-01-01

243

Evaluating regional blood spinal cord barrier dysfunction following spinal cord injury using longitudinal dynamic contrast-enhanced MRI  

Microsoft Academic Search

BACKGROUND: In vivo preclinical imaging of spinal cord injury (SCI) in rodent models provides clinically relevant information in translational research. This paper uses multimodal magnetic resonance imaging (MRI) to investigate neurovascular pathology and changes in blood spinal cord barrier (BSCB) permeability following SCI in a mouse model of SCI. METHODS: C57BL\\/6 female mice (n = 5) were subjected to contusive

Ilkan Tatar; Peter Cheng-te Chou; Mohamed Mokhtar Desouki; Hanaa El Sayed; Mehmet Bilgen

2009-01-01

244

Alertness in Young Healthy Subjects: An fMRI Study of Brain Region Interactivity Enhanced by a Warning Signal  

ERIC Educational Resources Information Center

An effective connectivity study was carried out on 16 young, healthy subjects performing an alertness task. The objective of this study was to develop and to evaluate a putative network model of alertness by adapting structural equation modeling to fMRI data. This study was designed to evaluate the directed interactivity of an attentional network…

Perin, B.; Godefroy, O.; Fall, S.; de Marco, G.

2010-01-01

245

Alertness in Young Healthy Subjects: An fMRI Study of Brain Region Interactivity Enhanced by a Warning Signal  

ERIC Educational Resources Information Center

|An effective connectivity study was carried out on 16 young, healthy subjects performing an alertness task. The objective of this study was to develop and to evaluate a putative network model of alertness by adapting structural equation modeling to fMRI data. This study was designed to evaluate the directed interactivity of an attentional network…

Perin, B.; Godefroy, O.; Fall, S.; de Marco, G.

2010-01-01

246

MRI-Visible Poly(?-caprolactone) with Controlled Contrast Agent Ratios for Enhanced Visualization in Temporary Imaging Applications.  

PubMed

Hydrophobic macromolecular contrast agents (MMCAs) are highly desirable to provide safe and efficient magnetic resonance (MR) visibility to implantable medical devices. In this study, we report on the synthesis and evaluation of novel biodegradable poly(?-caprolactone)-based MMCAs. Poly(?-propargyl-?-caprolactone-co-?-caprolactone)s containing 2, 5, and 10 mol % of propargyl groups have been prepared by ring-opening copolymerization of ?-caprolactone and the corresponding propargylated lactone. In parallel, a diazido derivative of the clinically used diethylenetriaminepentaacetic acid (DTPA)/Gd(3+) complex has been synthesized. Finally, MRI-visible poly(?-caprolactone)s (PCLs) were obtained by the efficient click ligation of these compounds via a Cu(I)-catalyzed [3 + 2] cycloaddition. ICP-MS analyses confirmed the efficient coupling of the complex on the PCL backbone with the MRI-visible PCLs containing 1.0, 2.6, and 3.6 wt % of Gd(3+). The influence of the Gd(3+) grafting density on the T1 relaxation times and on the MRI visibility of the novel biodegradable MMCAs was evaluated. Finally, their stability and cytocompatibility were assessed with regard to their potential as innovative MRI-visible biomaterials for biomedical applications. PMID:24007393

El Habnouni, Sarah; Nottelet, Benjamin; Darcos, Vincent; Porsio, Barbara; Lemaire, Laurent; Franconi, Florence; Garric, Xavier; Coudane, Jean

2013-09-17

247

Quasi-Cubic Magnetite\\/Silica Core-Shell Nanoparticles as Enhanced MRI Contrast Agents for Cancer Imaging  

Microsoft Academic Search

Development of magnetic resonance imaging (MRI) contrast agents that can be readily applied for imaging of biological tissues under clinical settings is a challenging task. This is predominantly due to the expectation of an ideal MR agent being able to be synthesized in large quantities, possessing longer shelf life, reasonable biocompatibility, tolerance against its aggregation in biological fluids, and high

Jos L. Campbell; Jyoti Arora; Simon F. Cowell; Ashish Garg; Peter Eu; Suresh K. Bhargava; Vipul Bansal; Yi Wang

2011-01-01

248

Dynamic Contrast-Enhanced MRI in Head-and-Neck Cancer: The Impact of Region of Interest Selection on the Intra- and Interpatient Variability of Pharmacokinetic Parameters  

SciTech Connect

Purpose: Dynamic contrast-enhanced (DCE) MRI-extracted parameters measure tumor microvascular physiology and are usually calculated from an intratumor region of interest (ROI). Optimal ROI delineation is not established. The valid clinical use of DCE-MRI requires that the variation for any given parameter measured within a tumor be less than that observed between tumors in different patients. This work evaluates the impact of tumor ROI selection on the assessment of intra- and interpatient variability. Method and Materials: Head and neck cancer patients received initial targeted therapy (TT) treatment with erlotinib and/or bevacizumab, followed by radiotherapy and concurrent cisplatin with synchronous TT. DCE-MRI data from Baseline and the end of the TT regimen (Lead-In) were analyzed to generate the vascular transfer function (K{sup trans}), the extracellular volume fraction (v{sub e}), and the initial area under the concentration time curve (iAUC{sub 1min}). Four ROI sampling strategies were used: whole tumor or lymph node (Whole), the slice containing the most enhancing voxels (SliceMax), three slices centered in SliceMax (Partial), and the 5% most enhancing contiguous voxels within SliceMax (95Max). The average coefficient of variation (aCV) was calculated to establish intrapatient variability among ROI sets and interpatient variability for each ROI type. The average ratio between each intrapatient CV and the interpatient CV was calculated (aRCV). Results: Baseline primary/nodes aRCVs for different ROIs not including 95Max were, for all three MR parameters, in the range of 0.14-0.24, with Lead-In values between 0.09 and 0.2, meaning a low intrapatient vs. interpatient variation. For 95Max, intrapatient CVs approximated interpatient CVs, meaning similar data dispersion and higher aRCVs (0.6-1.27 for baseline) and 0.54-0.95 for Lead-In. Conclusion: Distinction between different patient's primary tumors and/or nodes cannot be made using 95Max ROIs. The other three strategies are viable and equivalent for using DCE-MRI to measure head and neck cancer physiology.

Craciunescu, Oana I., E-mail: oana.craciunescu@duke.edu [Department of Radiation Oncology, Duke University Medical Center, Durham, NC (United States); Yoo, David S. [Department of Radiation Oncology, Duke University Medical Center, Durham, NC (United States); Cleland, Esi [GECAD Ghana Ltd., Acra (Ghana); Muradyan, Naira [iCAD Inc., Nashua, NH (United States); Carroll, Madeline D. [Department of Radiation Oncology, Duke University Medical Center, Durham, NC (United States); MacFall, James R.; Barboriak, Daniel P. [Department of Radiology, Duke University Medical Center, Durham, NC (United States); Brizel, David M. [Department of Radiation Oncology, Duke University Medical Center, Durham, NC (United States); Department of Surgery, Duke University Medical Center, Durham, NC (United States)

2012-03-01

249

Enhanced cellular uptake and long-term retention of chitosan-modified iron-oxide nanoparticles for MRI-based cell tracking  

PubMed Central

Tracking cells after therapeutic transplantation is imperative for evaluation of implanted cell fate and function. In this study, ultrasmall superparamagnetic iron oxide nanoparticles (USPIO NPs) were surface functionalized with water-soluble chitosan, a cationic polysaccharide that mediates enhanced endocytic uptake, endosomal escape into the cytosol, and subsequent long-term retention of nanoparticles. NP surface and chitosan were independently fluorescently labeled. Our NPs enable NP trafficking studies and determination of fate beyond uptake by fluorescence microscopy as well as tracking of labeled cells as localized regions of hypointensity in T2*-weighted magnetic resonance imaging (MRI) images. Adult rat neural stem cells (NSCs) were labeled with NPs, and assessment of NSC proliferation rates and differentiation potential revealed no significant differences between labeled and unlabeled NSCs. Significantly enhanced uptake of chitosan NPs in comparison to native NPs was confirmed by transmission electron microscopy, nuclear magnetic resonance (NMR) spectroscopy and in vitro cellular MRI at 11.7 Tesla. While only negligible fractions of native NPs enter cells, chitosan NPs appear within membranous vesicles within 2 hours of exposure. Additionally, chitosan-functionalized NPs escaped from membrane-bound vesicles within days, circumventing NP endo-lysosomal trafficking and exocytosis and hence enabling long-term tracking of labeled cells. Finally, our labeling strategy does not contain any NSC-specific reagents. To demonstrate general applicability across a variety of primary and immortalized cell types, embryonic mouse NSCs, mouse embryonic stem cells, HEK 293 kidney cells, and HeLa cervical cancer cells were additionally exposed to chitosan-USPIO NPs and exhibited similarly efficient loading as verified by NMR relaxometry. Our efficient and versatile labeling technology can support cell tracking with close to single cell resolution by MRI in vitro, for example, in complex tissue models not optically accessible by confocal or multi-photon fluorescence microscopy, and potentially in vivo, for example, in animal models of human disease or injury.

Bakhru, Sasha H; Altiok, Eda; Highley, Christopher; Delubac, Daniel; Suhan, Joseph; Hitchens, T Kevin; Ho, Chien; Zappe, Stefan

2012-01-01

250

The Principal of Dynamic Contrast Enhanced MRI, the Method of Pharmacokinetic Analysis, and Its Application in the Head and Neck Region  

PubMed Central

Many researchers have established the utility of the dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) in the differential diagnosis in the head and neck region, especially in the salivary gland tumors. The subjective assessment of the pattern of the time-intensity curve (TIC) or the simple quantification of the TIC, such as the time to peak enhancement (Tpeak) and the wash-out ratio (WR), is commonly used. Although the semiquantitative evaluations described above have been widely applied, they do not provide information on the underlying pharmacokinetic analysis in tissue. The quantification of DCE-MRI is preferable; therefore, many compartment model analyses have been proposed. The Toft and Kermode (TK) model is one of the most popular compartment models, which provide information about the influx forward volume transfer constant from plasma into the extravascular-extracellular space (EES) and the fractional volume of EES per unit volume of tissue is used in many clinical studies. This paper will introduce the method of pharmacokinetic analysis and also describe the clinical application of this technique in the head and neck region.

Chikui, Toru; Obara, Makoto; Simonetti, Arjan W.; Ohga, Masahiro; Koga, Shoichi; Kawano, Shintaro; Matsuo, Yoshio; Kamintani, Takeshi; Shiraishi, Tomoko; Kitamoto, Erina; Nakamura, Katsumasa; Yoshiura, Kazunori

2012-01-01

251

Ultra-high-field imaging distinguishes MS lesions from asymptomatic white matter lesions  

PubMed Central

Objectives: To investigate whether multiple sclerosis (MS) and non-MS white matter brain lesions can be distinguished by their appearance on 7 T T2*-weighted MRI. Methods: This was an observational study of 28 patients with MS and 17 patients with cerebral white matter lesions who did not have MS. Subjects were imaged using 7 T T2*-weighted imaging. White matter lesions were identified and analyzed for volume, location, and perivenous appearance. Results: Out of 901 lesions identified in patients with MS, 80% were perivenous. In comparison, 19% of 428 lesions identified in patients without MS had a perivenous appearance. Seven-Tesla T2*-weighted MRI reliably distinguished all patients with clinically definite MS (>40% lesions appeared perivenous) from those without clinical MS (<40% lesions appeared perivenous). Perivenous lesion appearance was more predictive of MS (odds ratio [OR] 14, p < 0.001) than subcortical or periventricular lesion location (OR 4.5, p < 0.001, and OR 2.4, p = 0.009). Perivenous lesion appearance was observed with a similar frequency in patients with clinically isolated syndrome of demyelination and in early (gadolinium-enhancing) MS lesions. Conclusion: Perivenous lesion location on 7 T T2*-weighted imaging is predictive of the presence of demyelination. Optimization of this imaging technique at lower magnetic resonance field strengths would offer benefit for the diagnosis of MS.

Tallantyre, E.C.; Dixon, J.E.; Donaldson, I.; Owens, T.; Morgan, P.S.; Morris, P.G.

2011-01-01

252

Pioglitazone modulates vascular inflammation in atherosclerotic rabbits monitored non-invasively with 18F-fluorodeoxyglucose-PET/CT and black blood dynamic contrast enhanced-MRI  

PubMed Central

Objectives We sought to determine the anti-atherosclerotic properties of pioglitazone using multi-modality non-invasive imaging techniques. Background Inflammation is an essential component of vulnerable or high risk atheromas. Pioglitazone, a peroxisome proliferator–activated receptor-gamma (PPAR-?)agonist possesses potent anti-inflammatory properties. We aimed to non-invasively to quantify the anti-inflammatory effects of pioglitazone on atheroma using 18F-fluorodeoxyglucose (18F-FDG)-PET/CT and dynamic contrast enhanced MRI (DCE-MRI). Methods Atherosclerotic plaques were induced in the aorta of fifteen New Zealand White (NZW) rabbits by a combination of hyperlipidemic diet and two balloon endothelial denudations. Nine rabbits continued the same diet whereas six received pioglitazone (10mg/kg orally) in addition to the diet. Twelve animals underwent 18F-FDG-PET/CT and fifteen animals underwent DCE-MRI at baseline, one and three months after treatment initiation. Concomitantly, serum metabolic parameters were monitored. After imaging was completed aortic histological analysis and correlation analysis was performed. Results 18F-FDG-PET/CT detected an increase in average standardized uptake value (SUV) in the control group (p<0.01), indicating progressive inflammation, while stable SUV values were observed in the treatment group, indicating no progression. DCE-MRI detected a significant decrease in area under the curve (AUC) for the pioglitazone group (p<0.01). Immunohistology of the aortas demonstrated a significant decrease in macrophage and oxidized phospholipid immunoreactivity in the pioglitazone group (p=0.04 and p=0.01, respectively) with respect to control animals, underlining the imaging results. Serum metabolic parameters showed no difference between groups. A strong positive correlation between SUV and macrophage density and AUC and neovessels was detected ( r2=0.86, p<0.0001 and r2=0.66, p=0.004, respectively). Conclusions 18F-FDG-PET/CT and DCE-MRI demonstrate non-invasively the anti-inflammatory effects of pioglitazone on atheroma. Both imaging modalities appear suited to monitor inflammation in atherosclerosis.

Vucic, Esad; Dickson, Stephen D.; Calcagno, Claudia; Rudd, James H.F.; Moshier, Erin; Hayashi, Katsumi; Mounessa, Jessica S.; Roytman, Michelle; Moon, Matthew J.; Lin, James; Tsimikas, Sotirios; Fisher, Edward A.; Nicolay, Klaas; Fuster, Valentin; Fayad, Zahi A.

2011-01-01

253

Enhancing insight in scientific problem solving by highlighting the functional features of prototypes: An fMRI study.  

PubMed

Insight can be the first step toward creating a groundbreaking product. As evident in anecdotes and major inventions in history, heuristic events (heuristic prototypes) prompted inventors to acquire insight when solving problems. Bionic imitation in scientific innovation is an example of this kind of problem solving. In particular, heuristic prototypes (e.g., the lotus effect; the very high water repellence exhibited by lotus leaves) help solve insight problems (e.g., non-stick surfaces). We speculated that the biological functional feature of prototypes is a critical factor in inducing insightful scientific problem solving. In this functional magnetic resonance imaging (fMRI) study, we selected scientific innovation problems and utilized "learning prototypes-solving problems" two-phase paradigm to test the supposition. We also explored its neural mechanisms. Functional MRI data showed that the activation of the middle temporal gyrus (MTG, BA 37) and the middle occipital gyrus (MOG, BA 19) were associated with the highlighted functional feature condition. fMRI data also indicated that the MTG (BA 37) could be responsible for the semantic processing of functional features and for the formation of novel associations based on related functions. In addition, the MOG (BA 19) could be involved in the visual imagery of formation and application of function association between the heuristic prototype and problem. Our findings suggest that both semantic processing and visual imagery could be crucial components underlying scientific problem solving. PMID:23994216

Hao, Xin; Cui, Shuai; Li, Wenfu; Yang, Wenjing; Qiu, Jiang; Zhang, Qinglin

2013-08-27

254

Enhanced multi-protocol analysis via intelligent supervised embedding (EMPrAvISE): detecting prostate cancer on multi-parametric MRI  

NASA Astrophysics Data System (ADS)

Currently, there is significant interest in developing methods for quantitative integration of multi-parametric (structural, functional) imaging data with the objective of building automated meta-classifiers to improve disease detection, diagnosis, and prognosis. Such techniques are required to address the differences in dimensionalities and scales of individual protocols, while deriving an integrated multi-parametric data representation which best captures all disease-pertinent information available. In this paper, we present a scheme called Enhanced Multi-Protocol Analysis via Intelligent Supervised Embedding (EMPrAvISE); a powerful, generalizable framework applicable to a variety of domains for multi-parametric data representation and fusion. Our scheme utilizes an ensemble of embeddings (via dimensionality reduction, DR); thereby exploiting the variance amongst multiple uncorrelated embeddings in a manner similar to ensemble classifier schemes (e.g. Bagging, Boosting). We apply this framework to the problem of prostate cancer (CaP) detection on 12 3 Tesla pre-operative in vivo multi-parametric (T2-weighted, Dynamic Contrast Enhanced, and Diffusion-weighted) magnetic resonance imaging (MRI) studies, in turn comprising a total of 39 2D planar MR images. We first align the different imaging protocols via automated image registration, followed by quantification of image attributes from individual protocols. Multiple embeddings are generated from the resultant high-dimensional feature space which are then combined intelligently to yield a single stable solution. Our scheme is employed in conjunction with graph embedding (for DR) and probabilistic boosting trees (PBTs) to detect CaP on multi-parametric MRI. Finally, a probabilistic pairwise Markov Random Field algorithm is used to apply spatial constraints to the result of the PBT classifier, yielding a per-voxel classification of CaP presence. Per-voxel evaluation of detection results against ground truth for CaP extent on MRI (obtained by spatially registering pre-operative MRI with available whole-mount histological specimens) reveals that EMPrAvISE yields a statistically significant improvement (AUC=0.77) over classifiers constructed from individual protocols (AUC=0.62, 0.62, 0.65, for T2w, DCE, DWI respectively) as well as one trained using multi-parametric feature concatenation (AUC=0.67).

Viswanath, Satish; Bloch, B. Nicholas; Chappelow, Jonathan; Patel, Pratik; Rofsky, Neil; Lenkinski, Robert; Genega, Elizabeth; Madabhushi, Anant

2011-03-01

255

Cellular-interstitial water exchange and its effect on the determination of contrast agent concentration in vivo: dynamic contrast-enhanced MRI of human internal obturator muscle.  

PubMed

The purpose of this study was to assess the effects of cellular-interstitial water exchange on estimates of tracer kinetics parameters obtained using rapid dynamic contrast-enhanced (DCE) MRI. Data from the internal obturator muscle of six patients were examined using three models of water exchange: no exchange (NX), fast exchange limit (FXL), and intermediate rate (shutter-speed [SS]). In combination with additional multiple flip angle (FA) data, a full two-pool exchange model was also used. The results obtained using the NX model (transfer constant, K(trans) = 0.049 +/- 0.027 min(-1), apparent interstitial volume, v(e) = 0.14 +/- 0.04) were marginally higher than those obtained using the FXL model (K(trans) = 0.045 +/- 0.025 min(-1), v(e) = 0.13 +/- 0.04), but the error bars overlapped in two-thirds of these parameter estimate pairs. Estimates of K(trans) and v(e) obtained using the SS model exceeded those obtained using the NX model in half the patients, and many estimates, including all those of intracellular residence time of water, t(i), were imprecise. Results obtained using the full two-pool model fell between those obtained using FXL and NX models, and estimates of t(i) were also imprecise. The results suggest that data obtained using clinically relevant DCE-MRI are exchange-insensitive and unsuitable for the assessment of cellular-interstitial water exchange. PMID:18956419

Buckley, David L; Kershaw, Lucy E; Stanisz, Greg J

2008-11-01

256

Dynamic Contrast-Enhanced and Diffusion MRI Show Rapid and Dramatic Changes in Tumor Microenvironment in Response to Inhibition of HIF-1? Using PX-4781  

PubMed Central

Abstract PX-478 is a new agent known to inhibit the hypoxia-responsive transcription factor, HIF-1?, in experimental tumors. The current study was undertaken in preparation for clinical trials to determine which noninvasive imaging endpoint(s) is sensitive to this drug's actions. Dynamic contrast-enhanced (DCE) and diffusion-weighted (DW) magnetic resonance imaging (MRI) were used to monitor acute effects on tumor hemodynamics and cellularity, respectively. Mice bearing human xenografts were treated either with PX-478 or vehicle, and imaged over time. DW imaging was performed at three b values to generate apparent diffusion coefficient of water (ADCw) maps. For DCE-MRI, a macromolecular contrast reagent, BSA-Gd-DTPA, was used to determine vascular permeability and vascular volume fractions. PX-478 induced a dramatic reduction in tumor blood vessel permeability within 2 hours after treatment, which returned to baseline by 48 hours. The anti-VEGF antibody, Avastin, reduced both the permeability and vascular volume. PX-478 had no effect on the perfusion behavior of a drug-resistant tumor system, A-549. Tumor cellularity, estimated from ADCw, was significantly decreased 24 and 36 hours after treatment. This is the earliest significant response of ADC to therapy yet reported. Based on these preclinical findings, both of these imaging endpoints will be included in the clinical trial of PX-478.

Jordan, Benedicte F; Runquist, Matthew; Raghunand, Natarajan; Baker, Amanda; Williams, Ryan; Kirkpatrick, Lynn; Powis, Garth; Gillies, Robert J

2005-01-01

257

Dynamic contrast-enhanced and diffusion MRI show rapid and dramatic changes in tumor microenvironment in response to inhibition of HIF-1alpha using PX-478.  

PubMed

PX-478 is a new agent known to inhibit the hypoxia-responsive transcription factor, HIF-1alpha, in experimental tumors. The current study was undertaken in preparation for clinical trials to determine which noninvasive imaging endpoint(s) is sensitive to this drug's actions. Dynamic contrast-enhanced (DCE) and diffusion-weighted (DW) magnetic resonance imaging (MRI) were used to monitor acute effects on tumor hemodynamics and cellularity, respectively. Mice bearing human xenografts were treated either with PX-478 or vehicle, and imaged over time. DW imaging was performed at three b values to generate apparent diffusion coefficient of water (ADCw) maps. For DCE-MRI, a macromolecular contrast reagent, BSA-Gd-DTPA, was used to determine vascular permeability and vascular volume fractions. PX-478 induced a dramatic reduction in tumor blood vessel permeability within 2 hours after treatment, which returned to baseline by 48 hours. The anti-VEGF antibody, Avastin, reduced both the permeability and vascular volume. PX-478 had no effect on the perfusion behavior of a drug-resistant tumor system, A-549. Tumor cellularity, estimated from ADCw, was significantly decreased 24 and 36 hours after treatment. This is the earliest significant response of ADC to therapy yet reported. Based on these preclinical findings, both of these imaging endpoints will be included in the clinical trial of PX-478. PMID:15967100

Jordan, Bénédicte F; Runquist, Matthew; Raghunand, Natarajan; Baker, Amanda; Williams, Ryan; Kirkpatrick, Lynn; Powis, Garth; Gillies, Robert J

2005-05-01

258

Quasi-Cubic Magnetite/Silica Core-Shell Nanoparticles as Enhanced MRI Contrast Agents for Cancer Imaging  

PubMed Central

Development of magnetic resonance imaging (MRI) contrast agents that can be readily applied for imaging of biological tissues under clinical settings is a challenging task. This is predominantly due to the expectation of an ideal MR agent being able to be synthesized in large quantities, possessing longer shelf life, reasonable biocompatibility, tolerance against its aggregation in biological fluids, and high relaxivity, resulting in better contrast during biological imaging. Although a repertoire of reports address various aforementioned issues, the previously reported results are far from optimal, which necessitates further efforts in this area. In this study, we demonstrate facile large-scale synthesis of sub-100 nm quasi-cubic magnetite and magnetite/silica core-shell (Mag@SiO2) nanoparticles and their applicability as a biocompatible T2 contrast agent for MRI of biological tissues. Our study suggests that silica-coated magnetite nanoparticles reported in this study can potentially act as improved MR contrast agents by addressing a number of aforementioned issues, including longer shelf life and stability in biological fluids. Additionally, our in vitro and in vivo studies clearly demonstrate the importance of silica coating towards improved applicability of T2 contrast agents for cancer imaging.

Cowell, Simon F.; Garg, Ashish; Eu, Peter; Bhargava, Suresh K.; Bansal, Vipul

2011-01-01

259

MRI of herpes simplex encephalitis  

Microsoft Academic Search

The magnetic resonance imaging (MRI) findings in eight patients with herpes simplex meningoencephalitis were reviewed: 14 examinations were analysed. The most striking finding was high signal intensity in the temporal lobe(s) with the typical configuration known from CT. Meningeal enhancement after Gd-DTPA administration was clearly seen in four patients. Haemorrhagic changes are much better seen on MRI than on CT.

Ph. Demaerel; G. Wilms; W. Robberecht; K. Johannik; P. Hecke; H. Carton; A. L. Baert

1992-01-01

260

Evidence of Key Tinnitus-Related Brain Regions Documented by a Unique Combination of Manganese-Enhanced MRI and Acoustic Startle Reflex Testing  

PubMed Central

Animal models continue to improve our understanding of tinnitus pathogenesis and aid in development of new treatments. However, there are no diagnostic biomarkers for tinnitus-related pathophysiology for use in awake, freely moving animals. To address this disparity, two complementary methods were combined to examine reliable tinnitus models (rats repeatedly administered salicylate or exposed to a single noise event): inhibition of acoustic startle and manganese-enhanced MRI. Salicylate-induced tinnitus resulted in wide spread supernormal manganese uptake compared to noise-induced tinnitus. Neither model demonstrated significant differences in the auditory cortex. Only in the dorsal cortex of the inferior colliculus (DCIC) did both models exhibit supernormal uptake. Therefore, abnormal membrane depolarization in the DCIC appears to be important in tinnitus-mediated activity. Our results provide the foundation for future studies correlating the severity and longevity of tinnitus with hearing loss and neuronal activity in specific brain regions and tools for evaluating treatment efficacy across paradigms.

Holt, Avril Genene; Bissig, David; Mirza, Najab; Rajah, Gary; Berkowitz, Bruce

2010-01-01

261

Quantitative in vivo measurement of early axonal transport deficits in a triple transgenic mouse model of Alzheimer's disease using manganese-enhanced MRI  

PubMed Central

Impaired axonal transport has been linked to the pathogenic processes of Alzheimer’s disease (AD) in which axonal swelling and degeneration are prevalent. The development of non-invasive neuroimaging methods to quantitatively assess in vivo axonal transport deficits would be enormously valuable to visualize early, yet subtle, changes in the AD brain, to monitor the disease progression and to quantify the effect of drug intervention. A triple transgenic mouse model of AD closely resembles human AD neuropathology. In this study, we investigated age-dependent alterations in the axonal transport rate in a longitudinal assessment of the triple transgenic mouse olfactory system, using fast multi-sliced T1 mapping with manganese-enhanced MRI. The data show that impairment in axonal transport is a very early event in AD pathology in these mice, preceding both deposition of A? plaques and formation of Tau fibrils.

Kim, Jieun; Choi, In-Young; Michaelis, Mary L.; Lee, Phil

2011-01-01

262

Dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) of photodynamic therapy (PDT) outcome and associated changes in the blood-brain barrier following Pc 4-PDT of glioma in an athymic nude rat model  

NASA Astrophysics Data System (ADS)

Introduction: Dynamic Contrast-Enhanced-Magnetic Resonance Imaging (DCE-MRI) appears to provide an unambiguous means of tracking the outcome of photodynamic therapy (PDT) of brain tumors with the photosensitizer Pc 4. The increase in Gd enhancement observed after Pc 4-PDT may be due to a temporary opening of the blood-brain-barrier which, as noted by others, may offer a therapeutic window. Methods: We injected 2.5 x 105 U87 cells into the brains of 9 athymic nude rats. After 8-9 days peri-tumor DCE-MRI images were acquired on a 7.0 T microMRI scanner before and after the administration of 150 ?L Gd. DCE-MRI scans were repeated three times following Pc 4-PDT. Results: The average, normalized peak enhancement in the tumor region, approximately 30-90 seconds after Gd administration, was 1.31 times greater than baseline (0.03 Standard Error [SE]) prior to PDT and was 1.44 (0.02 SE) times baseline in the first Post-PDT scans (Day 11), a statistically significant (p ~ 0.014, N=8) increase over the Pre- PDT scans, and was 1.38 (0.02 SE) times baseline in the second scans (Day 12), also a statistically significant (p ~ 0.008, N=7) increase. Observations were mixed in the third Post-PDT scans (Day 13), averaging 1.29 (0.03 SE) times baseline (p ~ 0.66, N=7). Overall a downward trend in enhancement was observed from the first to the third Post-PDT scans. Discussion: DCE-MRI may provide an unambiguous indication of brain tumor PDT outcome. The initial increase in DCE-MRI signal may correlate with a temporary, PDT-induced opening of the blood-brain-barrier, creating a potential therapeutic window.

Belle, Vaijayantee; Anka, Ali; Cross, Nathan; Thompson, Paul; Mott, Eric; Sharma, Rahul; Gray, Kayla; Zhang, Ruozhen; Xu, Yueshuo; Sun, Jiayang; Flask, Chris A.; Oleinick, Nancy L.; Dean, David

2012-02-01

263

Laser-induced thermotherapy (LITT) for the treatment of liver metastases: the correlation of Gd-DTPA-enhanced magnetic resonance imaging (MRI) and histomorphological findings in the chronic model  

NASA Astrophysics Data System (ADS)

The purpose of the study was to evaluate Gd-DTPA-enhanced MRI for the follow-up of laser-induced thermotherapy (LITT) in the treatment of liver metastases. Interstitial laser-induced thermotherapy (LITT) was performed in 55 chinchilla bastard rabbits with a Nd:YAG laser and a specially developed diffuser tip applicator. The animals were examined at different times using MRI and histological methods. T1-weighted spin-echo sequences were made with gadolinium-DTPA and submitted to correlation analysis. The analysis yielded a good correlation (r equals 0.96) between the largest lesion diameters. Lesions showed discontinuous regeneration kinetics with a 41% volume reduction 1 month after LITT. MRI of the lesion directly after LITT showed a hyperintense transition zone. Following the application of intravenous contrast medium, transition zone enhancement was first seen 72 - 96 hours after LITT. Even after 6 months, the laser-induced lesion is visualized as a non-enhanced area. Lesion regeneration followed the principles of wound healing. It is concluded that gadolinium-DTPA- enhanced MRI yielded definitive criteria for the follow-up assessment of LITT.

Isbert, Christoph M.; Germer, Christoph-Thomas; Albrecht, Dirk; Schilling, Andreas; Heiniche, Antje; Roggan, Andre; Wolf, K.-J.; Mueller, Gerhard J.; Buhr, Heinz-Johannes

1997-05-01

264

Portable MRI  

Microsoft Academic Search

This project proposes to: (1) provide the power of MRI to situations where it presently isn't available; (2) perform the engineering required to move from lab to a functional prototype; and (3) leverage significant existing infrastructure and capability in ultra-low field MRI. The reasons for doing this: (1) MRI is the most powerful tool for imaging soft-tissue (e.g. brain); (2)

Espy; Michelle A

2012-01-01

265

A case report of pseudoprogression followed by complete remission after proton-beam irradiation for a low-grade glioma in a teenager: the value of dynamic contrast-enhanced MRI  

Microsoft Academic Search

A fourteen years-old boy was treated post-operatively with proton therapy for a recurrent low-grade oligodendroglioma located in the tectal region. Six months after the end of irradiation (RT), a new enhancing lesion appeared within the radiation fields. To differentiate disease progression from radiation-induced changes, dynamic susceptibility contrast-enhanced (DSCE) MRI was used with a T2* sequence to study perfusion and permeability

Candice Meyzer; Frédéric Dhermain; Denis Ducreux; Jean-Louis Habrand; Pascale Varlet; Christian Sainte-Rose; Christelle Dufour; Jacques Grill

2010-01-01

266

Biventricular apical thrombi demonstrated by contrast-enhanced cardiac MRI following anteroapical STEMI and unsuccessful reperfusion therapy  

PubMed Central

Contrast-enhanced cardiac magnetic resonance imaging can define the territory and extent of myocardial infarction from patterns of late gadolinium enhancement. Following failure to reperfuse with thrombolytic therapy, a case of myocardial infarction is described in which ongoing symptoms and an electrocardiogram change led to a diagnostic dilemma. Cardiac magnetic resonance imaging confirmed an apical infarction, an aneurysm and acute pericarditis. In addition, late gadolinium enhancement unexpectedly revealed the presence of biventricular apical thrombi. The prevalence of cardiac thrombi and pulmonary emboli may be greater than generally appreciated.

Keeble, William; VonderMuhll, Isabelle; Paterson, Ian

2008-01-01

267

Distinguishing features of ?-proteobacterial genomes  

PubMed Central

We analyzed several features of five currently available ?-proteobacterial genomes, including two aerobic bacteria exhibiting predatory behavior and three anaerobic sulfate-reducing bacteria. The ? genomes are distinguished from other bacteria by several properties: (i) The ? genomes contain two “giant” S1 ribosomal protein genes in contrast to all other bacterial types, which encode a single or no S1; (ii) in most ?-proteobacterial genomes the major ribosomal protein (RP) gene cluster is near the replication terminus whereas most bacterial genomes place the major RP cluster near the origin of replication; (iii) the ? genomes possess the rare combination of discriminating asparaginyl and glutaminyl tRNA synthetase (AARS) together with the amido-transferase complex (Gat CAB) genes that modify Asp-tRNAAsn into Asn-tRNAAsn and Glu-tRNAGln into Gln-tRNAGln; (iv) the TonB receptors and ferric siderophore receptors that facilitate uptake and removal of complex metals are common among ? genomes; (v) the anaerobic ? genomes encode multiple copies of the anaerobic detoxification protein rubrerythrin that can neutralize hydrogen peroxide; and (vi) ?54 activators play a more important role in the ? genomes than in other bacteria. ? genomes have a plethora of enhancer binding proteins that respond to environmental and intracellular cues, often as part of two-component systems; (vii) ? genomes encode multiple copies of metallo-?-lactamase enzymes; (viii) a host of secretion proteins emphasizing SecA, SecB, and SecY may be especially useful in the predatory activities of Myxococcus xanthus; (ix) ? proteobacteria drive many multiprotein machines in their periplasms and outer membrane, including chaperone-feeding machines, jets for slime secretion, and type IV pili. Bdellovibrio replicates in the periplasm of prey cells. The sulfate-reducing ? proteobacteria metabolize hydrogen and generate a proton gradient by electron transport. The predicted highly expressed genes from ? genomes reflect their different ecologies, metabolic strategies, and adaptations.

Karlin, Samuel; Brocchieri, Luciano; Mrazek, Jan; Kaiser, Dale

2006-01-01

268

MRI of cochlear otosclerosis  

Microsoft Academic Search

Cochlear otosclerosis is an uncommon cause of mixed and sensorineural hearing loss. This has a characteristic appearance on CT, producing a distinctive pericochlear hypodense double ring. However, its appearance on MRI is not as readily appreciated, producing a ring of intermediate signal in the pericochlear and perilabyrinthine regions on T1 weighted images, demonstrating mild to moderate enhancement after gadolinium administration.

J P N GOH; L L CHAN; T Y TAN

2002-01-01

269

Hepatic Cavernous Hemangiomas: Relationship between Speed of Intratumoral Enhancement during Dynamic MRI and Apparent Diffusion Coefficient on Diffusion-Weighted Imaging  

PubMed Central

Objective To investigate the relationships between the apparent diffusion coefficients (ADCs) on diffusion-weighted imaging (DWI) and the speed of contrast-enhancement in hepatic hemangiomas. Materials and Methods Sixty-nine hepatic hemangiomas (? 1 cm) were evaluated with DWI, by using multiple b values (b = 50, 400, 800 s/mm2), followed by a gadolinium-enhanced dynamic MRI. The lesions were classified into three groups, according to the speed of contrast-enhancement on the portal phase. ADCs were measured on the ADC map automatically, and were calculated by using the two different b values (mADC50-400 with b values = 50 and 400; mADC400-800 with b values = 400 and 800 s/mm2). Results The mean ADCs (× 10-3 mm2/s) were significantly higher in the rapid group (1.9 ± 0.44) than in the intermediate (1.7 ± 0.35, p = 0.046) or the slow groups (1.4 ± 0.34, p = 0.002). There were significant differences between the rapid and the slow groups in mADC50-400 (2.12 vs. 1.48; p = 0.008) and mADC400-800 (1.68 vs. 1.22, p = 0.010), and between the rapid and the intermediate groups in mADC50-400 (2.12 vs. 1.79, p = 0.049). Comparing mADC50-400 with mADC400-800, there was a significant difference only in the rapid group (p = 0.001). Conclusion Higher ADCs of rapidly-enhancing hemangiomas may be related to richer intralesional vascular perfusion. Also, the restricted diffusion may be attributed to the difference of structural characteristics of hemangioma.

Nam, Se Jin; Park, Kae Young; Chung, Jae-Joon; Kim, Joo Hee; Kim, Ki Whang

2012-01-01

270

In vivo tumor characterization using both MR and optical contrast agents with a hybrid MRI-DOT system  

NASA Astrophysics Data System (ADS)

Dynamic contrast enhanced MRI (DCE-MRI) has been proven to be the most sensitive modality in detecting breast lesions. Currently available MR contrast agent, Gd-DTPA, is a low molecular weight extracellular agent and can diffuse freely from the vascular space into interstitial space. Due to this reason, DCE-MRI has low sensitivity in differentiating benign and malignant tumors. Meanwhile, diffuse optical tomography (DOT) can be used to provide enhancement kinetics of an FDA approved optical contrast agent, ICG, which behaves like a large molecular weight optical agent due to its binding to albumin. The enhancement kinetics of ICG may have a potential to distinguish between the malignant and benign tumors and hence improve the specificity. Our group has developed a high speed hybrid MRI-DOT system. The DOT is a fully automated, MR-compatible, multi-frequency and multi-spectral imaging system. Fischer-344 rats bearing subcutaneous R3230 tumor are injected simultaneously with Gd-DTPA (0.1nmol/kg) and IC-Green (2.5mg/kg). The enhancement kinetics of both contrast agents are recorded simultaneously with this hybrid MRI-DOT system and evaluated for different tumors.

Lin, Yuting; Ghijsen, Michael; Thayer, David; Nalcioglu, Orhan; Gulsen, Gultekin

2011-02-01

271

A Bayesian hierarchical model for the analysis of a longitudinal dynamic contrast-enhanced MRI oncology study.  

PubMed

Imaging in clinical oncology trials provides a wealth of information that contributes to the drug development process, especially in early phase studies. This article focuses on kinetic modeling in DCE-MRI, inspired by mixed-effects models that are frequently used in the analysis of clinical trials. Instead of summarizing each scanning session as a single kinetic parameter--such as median k(trans) across all voxels in the tumor ROI-we propose to analyze all voxel time courses from all scans and across all subjects simultaneously in a single model. The kinetic parameters from the usual nonlinear regression model are decomposed into unique components associated with factors from the longitudinal study; e.g., treatment, patient, and voxel effects. A Bayesian hierarchical model provides the framework to construct a data model, a parameter model, as well as prior distributions. The posterior distribution of the kinetic parameters is estimated using Markov chain Monte Carlo (MCMC) methods. Hypothesis testing at the study level for an overall treatment effect is straightforward and the patient- and voxel-level parameters capture random effects that provide additional information at various levels of resolution to allow a thorough evaluation of the clinical trial. The proposed method is validated with a breast cancer study, where the subjects were imaged before and after two cycles of chemotherapy, demonstrating the clinical potential of this method to longitudinal oncology studies. PMID:19097226

Schmid, Volker J; Whitcher, Brandon; Padhani, Anwar R; Taylor, N Jane; Yang, Guang-Zhong

2009-01-01

272

Simplified MRI  

NSDL National Science Digital Library

Is it a tumor? Magnetic Resonance Imaging (MRI) can tell. Your head is full of tiny radio transmitters (the nuclear spins of the hydrogen nuclei of your water molecules). In an MRI unit, these little radios can be made to broadcast their positions, giving a detailed picture of the inside of your head.

Simulations, Phet I.; Dubson, Michael; Lemaster, Ron; Mckagan, Sam; Perkins, Kathy; Wieman, Carl

2006-07-01

273

Differential microstructure and physiology of brain and bone metastases in a rat breast cancer model by diffusion and dynamic contrast enhanced MRI.  

PubMed

Pharmacological approaches to treat breast cancer metastases in the brain have been met with limited success. In part, the impermeability of the blood brain barrier (BBB) has hindered delivery of chemotherapeutic agents to metastatic tumors in the brain. BBB-permeable chemotherapeutic drugs are being developed, and noninvasively assessing the efficacy of these agents will be important in both preclinical and clinical settings. In this regard, dynamic contrast enhanced (DCE) and diffusion weighted imaging (DWI) are magnetic resonance imaging (MRI) techniques to monitor tumor vascular permeability and cellularity, respectively. In a rat model of metastatic breast cancer, we demonstrate that brain and bone metastases develop with distinct physiological characteristics as measured with MRI. Specifically, brain metastases have limited permeability of the BBB as assessed with DCE and an increased apparent diffusion coefficient (ADC) measured with DWI compared to the surrounding brain. Microscopically, brain metastases were highly infiltrative, grew through vessel co-option, and caused extensive edema and injury to the surrounding neurons and their dendrites. By comparison, metastases situated in the leptomenengies or in the bone had high vascular permeability and significantly lower ADC values suggestive of hypercellularity. On histological examination, tumors in the bone and leptomenengies were solid masses with distinct tumor margins. The different characteristics of these tissue sites highlight the influence of the microenvironment on metastatic tumor growth. In light of these results, the suitability of DWI and DCE to evaluate the response of chemotherapeutic and anti-angiogenic agents used to treat co-opted brain metastases, respectively, remains a formidable challenge. PMID:22042553

Budde, Matthew D; Gold, Eric; Jordan, E Kay; Frank, Joseph A

2011-11-01

274

Deficits in axonal transport in hippocampal-based circuitry and the visual pathway in APP knock-out animals witnessed by manganese enhanced MRI  

PubMed Central

Mounting evidence implicates axonal transport defects, typified by the presence of axonal varicosities with aberrant accumulations of cargo, as an early event in Alzheimer’s disease (AD) pathogenesis. Work identifying amyloid precursor protein (APP) as a vesicular motor receptor for anterograde axonal transport further implicates axonal transport in AD. Manganese-enhanced MRI (MEMRI) detects axonal transport dynamics in preclinical studies. Here we pursue an understanding of the role of APP in axonal transport in the central nervous system by applying MEMRI to hippocampal circuitry and to the visual pathway in living mice homozygous for either wild type or a deletion in the APP gene (n = 12 for each genotype). Following intra-ocular or stereotaxic hippocampal injection, we performed time-lapse MRI to detect Mn2+ transport. Three dimensional whole brain datasets were compared on a voxel-wise basis using within-group pair-wise analysis. Quantification of transport to structures connected to injection sites via axonal fiber tracts was also performed. Histology confirmed consistent placement of hippocampal injections and no observable difference in glial-response to the injections. APP ?/? mice had significantly reduced transport from the hippocampus to the septal nuclei and amygdala after 7 hours and reduced transport to the contralateral hippocampus after 25 hours; axonal transport deficits in the APP ?/? animals were also identified in the visual pathway. These data support a system-wide role for APP in axonal transport within the central nervous system and demonstrate the power of MEMRI for assessing neuronal circuitry involved in memory and learning.

Gallagher, Joseph J.; Zhang, Xiaowei; Ziomek, Greg; Jacobs, Russell E.; Bearer, Elaine L.

2012-01-01

275

Enhancing k-means and kernelized fuzzy c-means clustering with cluster center initialization in segmenting MRI brain images  

Microsoft Academic Search

Clustering is the process of organizing data objects into a set of disjoint classes called clusters. The objective of this paper is to develop an enhanced k-means and kernelized fuzzy c-means for a segmentation of brain magnetic resonance images. Performance of iterative clustering algorithms which converges to numerous local minima depend highly on initial cluster centers. In general the clustering

N. Hema Rajini; R. Bhavani

2011-01-01

276

Quantitative assessment of macromolecular concentration during direct infusion into an agarose hydrogel phantom using contrast-enhanced MRI  

Microsoft Academic Search

Convection-enhanced delivery (CED), that is, direct tissue infusion, has emerged as a promising local drug delivery method for treating diseases of the nervous system. Determination of the spatial distribution of therapeutic agents after infusion is important in evaluating the efficacy of treatment, optimizing infusion protocols and improving the understanding of drug pharmacokinetics. In this study, we provide a methodology to

Xiaoming Chen; Garrett W. Astaryb; Hector Sepulveda; Thomas H. Marecic; Malisa Sarntinoranont

277

Tumor Metabolism and Perfusion in Head and Neck Squamous Cell Carcinoma: Pretreatment Multimodality Imaging with 1H-Magnetic Resonance Spectroscopy, Dynamic Contrast-Enhanced MRI and 18F-FDG PET  

PubMed Central

Purpose To correlate proton magnetic resonance spectroscopy (1H-MRS), dynamic contrast-enhanced MRI (DCE-MRI) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) in nodal metastases of patients with head and neck squamous cell carcinoma (HNSCC) for assessment of tumor biology. Additionally, pretreatment multimodality imaging (MMI) was evaluated for its efficacy in predicting short-term response to treatment. Methods and Materials Metastatic neck nodes were imaged with 1H-MRS, DCE-MRI and 18F-FDG PET in 16 patients with newly diagnosed HNSCC before treatment. Short-term radiological response was evaluated at 3–4 months. The correlations between 1H-MRS (choline concentration, Cho/W), DCE-MRI (volume transfer constant, Ktrans; volume fraction of the extravascular extracellular space, ve; and redistribution rate constant, kep) and 18F-FDG PET (standard uptake value, SUV; and total lesion glycolysis, TLG) were calculated using non-parametric Spearman rank correlation. To predict the short-term response, logistic regression analysis was performed. Results A significant positive correlation was found between Cho/W and TLG (? = 0.599, p = 0.031). Cho/W correlated negatively with heterogeneity measures std(ve) (? = ?0.691, p = 0.004) and std(kep) (? = ?0.704, p = 0.003). SUVmax values correlated strongly with MRI tumor volume (? = 0.643, p = 0.007). Logistic regression indicated that std(Ktrans) and SUVmean were significant predictors of short-term response (p < 0.07). Conclusion Pretreatment multi-modality imaging using 1H-MRS, DCE-MRI and 18F-FDG PET is feasible in HNSCC patients with nodal metastases. Additionally, combined DCE-MRI and 18F-FDG PET parameters were predictive of short-term response to treatment.

Jansen, Jacobus F.A.; Schoder, Heiko; Lee, Nancy Y.; Stambuk, Hilda. E.; Wang, Ya; Fury, Matthew G.; Patel, Snehal G.; Pfister, David G.; Shah, Jatin P.; Koutcher, Jason A.; Shukla-Dave, Amita

2010-01-01

278

Percentage of signal intensity loss for characterisation of focal liver lesions in patients with chronic liver disease using ferucarbotran-enhanced MRI  

PubMed Central

The purpose of this study was to determine the percentage of signal intensity loss (PSIL) threshold for the characterisation of focal liver lesions among patients with chronic liver disease. 55 nodules in 49 patients with chronic liver disease who underwent ferucarbotran-enhanced MR studies were included. Among the 49 patients, 40 had liver cirrhosis and 9 had chronic hepatitis. 8 haemangiomas, 3 focal nodular hyperplasia, 9 dysplastic nodules and 12 well, 19 moderately and 4 poorly differentiated hepatocellular carcinomas (HCCs) were revealed. The PSIL, signal-to-noise ratio and contrast-to-noise ratio of each lesion type were calculated. The diagnostic performance of PSIL on ferucarbotran-enhanced T2 weighted images (PSILT2WI) and T2 weighted fat-suppression images (PSILFS-T2WI) that characterised hepatic tumours was compared with receiver operating characteristic (ROC) analysis. Using ROC analysis, the diagnostic performance of PSILFS-T2WI was superior to that of PSILT2WI (p = 0.01). The mean PSILFS-T2WI of the benign lesions was significantly higher than that of HCC (p<0.001), and the mean PSILFS-T2WI of well-differentiated HCC was significantly higher than that of moderately/poorly differentiated HCCs (p = 0.001). With a PSILFS-T2WI threshold of 40% in lesions characterising ferucarbotran-enhanced FS-T2WI, the sensitivity, specificity, accuracy, positive predictive value and negative predictive value were 88.6%, 95%, 90.9%, 96.9% and 82.6%, respectively. In conclusion, with ferucarbotran-enhanced FS-T2WI, a PSILFS-T2WI threshold of 40% for characterising focal liver nodules among patients with chronic liver disease is recommended. It is useful for distinguishing HCC from benign nodules.

Chou, C-T; Chen, R-C; Chen, W-T; Lii, J-M

2010-01-01

279

Enhanced reward sensitivity and decreased loss sensitivity in Internet addicts: an fMRI study during a guessing task.  

PubMed

As the world's fastest growing "addiction", Internet addiction should be studied to unravel the potential heterogeneity. The present study is set to examine reward and punishment processing in Internet addicts as compared to healthy controls while they subjectively experience monetary gain and loss during the performance of a guessing task. The results showed that Internet addicts associated with increased activation in orbitofrontal cortex in gain trials and decreased anterior cingulate activation in loss trials than normal controls. The results suggested that Internet addicts have enhanced reward sensitivity and decreased loss sensitivity than normal comparisons. PMID:21764067

Dong, Guangheng; Huang, Jie; Du, Xiaoxia

2011-07-20

280

Cardiac MRI  

MedlinePLUS

... Blogger. Share this page from the NHLBI on Buzz. Share this page from the NHLBI on Delicious. ... inserted into your body. MRI uses radio waves, magnets, and a computer to create pictures of your ...

281

Chest MRI  

MedlinePLUS

... Blogger. Share this page from the NHLBI on Buzz. Share this page from the NHLBI on Delicious. ... and blood vessels. Chest MRI uses radio waves, magnets, and a computer to create these pictures. The ...

282

Gadofluorine M enhancement allows more sensitive detection of inflammatory CNS lesions than T2-w imaging: a quantitative MRI study.  

PubMed

Magnetic resonance imaging plays a pivotal role in the diagnosis and treatment monitoring of multiple sclerosis. Currently available magnetic resonance-techniques only partly reflect the extent of tissue inflammation and damage. In the present study, application of the experimental magnetic resonance-contrast agent Gadofluorine M significantly increased the sensitivity of lesion detection in myelin-oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis, an animal model for multiple sclerosis. Gadofluorine M-enhancement on T(1)-weighted (T(1)-w) images utilizing a clinical 1.5 T magnetic resonance unit showed numerous lesions in optic nerve, spinal cord and brain, the majority of which were not detectable on standard T(2)-weighted (T(2)-w) and Gd-DTPA enhanced T(1)-w sequences. Quantitative assessment by pixel counts revealed highly significant differences in sensitivity in favour of Gadofluorine M. Gadofluorine uptake closely corresponded to inflammation and demyelination on tissue sections. These unique features of Gadofluorine M in visualizing inflammatory CNS lesions hold promise for future clinical development in multiple sclerosis. PMID:18669504

Bendszus, Martin; Ladewig, Gesa; Jestaedt, Leonie; Misselwitz, Bernd; Solymosi, Laszlo; Toyka, Klaus; Stoll, Guido

2008-07-24

283

Mapping of oxygen by imaging lipids relaxation enhancement: A potential sensitive endogenous MRI contrast to map variations in tissue oxygenation.  

PubMed

PURPOSE: Because of its paramagnetic properties, oxygen may act as an endogenous magnetic resonance imaging contrast agent by changing proton relaxation rates. Changes in tissue oxygen concentrations have been shown to produce changes in relaxation rate R(1) of water. The aim of the study was to improve the sensitivity of oxygen enhanced R(1) imaging by exploiting the higher solubility of oxygen in lipids (as compared with water) to sensitively monitor changes in tissue oxygen levels by selectively measuring the R(1) of lipids. METHODS: The method, with the acronym "MOBILE" (mapping of oxygen by imaging lipids relaxation enhancement), was applied in different mouse models of hypoxic processes on a 11.7 T magnetic resonance imaging system. MOBILE was compared with R*(2) , R(1) of water, and with pO(2) measurements (using electron paramagnetic resonance oximetry). MOBILE was also applied in the brain of healthy human volunteers exposed to an oxygen breathing challenge on a 3 T magnetic resonance imaging system. RESULTS: MOBILE was shown to be able to monitor changes in oxygenation in tumor, peripheral, liver, and brain tissues. The clinical translation was demonstrated in human volunteers. CONCLUSION: MOBILE arises as a promising noninvasive and sensitive tool for diagnosis and therapeutic guidance in disorders involving hypoxia. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc. PMID:23023932

Jordan, Bénédicte F; Magat, Julie; Colliez, Florence; Ozel, Elif; Fruytier, Anne-Catherine; Marchand, Valérie; Mignion, Lionel; Bouzin, Caroline; Cani, Patrice D; Vandeputte, Caroline; Feron, Olivier; Delzenne, Nathalie; Himmelreich, Uwe; Denolin, Vincent; Duprez, Thierry; Gallez, Bernard

2012-09-28

284

Light-dependant intraretinal ion regulation by melanopsin in young awake and free moving mice evaluated with manganese-enhanced MRI  

PubMed Central

Purpose To test the hypothesis that in young, functionally blind mice, light-dependent intraretinal ion regulation occurs via melanopsin. Methods Postnatal day (P) 7 wild type (WT, C57Bl/6) and melanopsin knockout (KO, opn4?/?, B6129) mice were light or dark adapted. Awake and freely moving animals were injected intraperitoneally (ip) with MnCl2. Four hours later, the mice in both groups were anesthetized and studied with manganese-enhanced MRI (MEMRI) to measure the extent of intraretinal uptake of manganese and whole retinal thicknesses. Results In control P7 mice, light exposure increased (p<0.05) retinal manganese uptake over that in dark. This difference was observed throughout most of the retina. In P7 KO mice, intraretinal manganese uptake did not differ from that in age-matched dark-adapted WT mice, and was not light-dependent. No differences in whole retinal thickness were noted between groups. Conclusions First time evidence is presented which demonstrates intraretinal ion regulation by melanopsin in vivo.

Roberts, Robin; Bissig, David

2010-01-01

285

Enhanced Antitumor Efficacy of a Vascular Disrupting Agent Combined with an Antiangiogenic in a Rat Liver Tumor Model Evaluated by Multiparametric MRI  

PubMed Central

A key problem in solid tumor therapy is tumor regrowth from a residual viable rim after treatment with a vascular disrupting agent (VDA). As a potential solution, we studied a combined treatment of a VDA and antiangiogenic. This study was approved by the institutional ethical committee for the use and care of laboratory animals. Rats with implanted liver tumors were randomized into four treatment groups: 1) Zd6126 (Zd); 2) Thalidomide (Tha); 3) Zd in combination with Tha (ZdTha); and 4) controls. Multiparametric MRIs were performed and quantified before and after treatment. Circulating endothelial progenitor cells (EPCs) and plasma stromal cell-derived factor-1? (SDF-1?) were monitored. Tumor apoptosis, necrosis, and microvessels were verified by histopathology. A single use of Zd or Tha did not significantly delay tumor growth. The combined ZdTha showed enhanced antitumor efficacy due to synergistic effects; it induced a cumulative tumor apoptosis or necrosis, which resulted in significant delay in tumor growth and reduction in the viable tumor rim; it also reduced tumor vessel permeability; and it improved tumor hemodynamic indexes, most likely via a transient normalization of tumor vasculature induced by Tha. A stepwise linear regression analysis showed that the apparent diffusion coefficient was an independent predictor of tumor growth. We found no significant increases in Zd-induced circulating EPCs or plasma SDF-1?. ZdTha showed improved therapeutic efficacy in solid tumors compared to either agent alone. The therapeutic effects were successfully tracked in vivo with multiparametric MRI.

Chen, Feng; Feng, Yingmei; Zheng, Kaier; De Keyzer, Frederik; Li, Junjie; Feng, Yuanbo; Cona, Marlein Miranda; Wang, Huaijun; Jiang, Yansheng; Yu, Jie; Marchal, Guy; Verfaillie, Catherine; De Geest, Bart; Oyen, Raymond; Ni, Yicheng

2012-01-01

286

Accuracy of T1 measurement in dynamic contrast-enhanced breast MRI using two- and three-dimensional variable flip angle fast low-angle shot.  

PubMed

In vivo T1 measurements, used to monitor the uptake of contrast agent by tissues, are typically performed as a first step in implementing compartmental analysis of contrast-enhanced breast magnetic resonance imaging (MRI) data. We have extended previously described methodology for in vivo T1 measurement (using a variable flip-angle gradient-recalled echo technique) to two-dimensional (2D), fast low-angle shot (FLASH). This approach requires computational modeling of slice-selective radiofrequency (RF) excitation to correct for nonrectangular slice profiles. The accuracy with which breast tissue T1 values can be measured by this approach is examined: T1 measurements from phantom and in vivo image data acquired with 2D and 3D FLASH imaging sequences are presented. Significant sources of error due to imaging pulse sequence quality and RF transmit field nonuniformity in the breast coil device that will have detrimental consequences for compartmental analysis are identified. Rigorous quality assurance programs with calibrated phantoms are thus recommended, to verify the accuracy with which T1 measurements are obtained. PMID:10077009

Brookes, J A; Redpath, T W; Gilbert, F J; Murray, A D; Staff, R T

1999-02-01

287

Dynamic contrast-enhanced MRI in mice at high field: Estimation of the arterial input function can be achieved by phase imaging.  

PubMed

PURPOSE: Quantitative dynamic contrast-enhanced MRI requires an accurate arterial input function (AIF). At high field, increased susceptibility effects and decreased longitudinal relaxivity of contrast agents lead to predominant T(2) * effects in blood vessels, producing a dip in signal during passage of the contrast agent bolus. This study determined phase-derived AIFs in mice at 11.7 T. METHODS: AIFs were measured in aorta/vena cava for five FBV/N mice and in iliac arteries/veins for five NMRI mice with a fast low angle shot sequence, simultaneously with tumor imaging (temporal resolution: 1.19 s). Gadoterate was injected into the tail vein as a bolus (0.286 mmol Gd/kg). An in vitro study was also performed to calculate the relationship between ?? and gadolinium concentration. RESULTS: The phantom system confirmed the linear relationship between measured ?? and gadolinium concentration. In vivo, a dip in arterial magnitude signal made it impossible to quantify the AIF. With phase imaging, a clear quantifiable bolus peak was obtained; peak measured concentration in plasma was 4.9?±?0.9 mM for FBV/N mice and 8.0?±?0.6 mM for NMRI mice, close to the expected concentration of 6.8 mM. CONCLUSION: Phase imaging seems to be an appropriate means to measure the AIF of mice at high field. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc. PMID:23440927

Fruytier, A-C; Magat, J; Colliez, F; Jordan, B; Cron, G; Gallez, B

2013-02-25

288

fMRI evidence of degeneration-induced neuropathic pain in diabetes: Enhanced limbic and striatal activations.  

PubMed

Persistent neuropathic pain due to peripheral nerve degeneration in diabetes is a stressful symptom; however, the underlying neural substrates remain elusive. This study attempted to explore neuroanatomical substrates of thermal hyperalgesia and burning pain in a diabetic cohort due to pathologically proven cutaneous nerve degeneration (the painful group). By applying noxious 44°C heat stimuli to the right foot to provoke neuropathic pain symptoms, brain activation patterns were compared with those of healthy control subjects and patients with a similar degree of cutaneous nerve degeneration but without pain (the painless group). Psychophysical results showed enhanced affective pain ratings in the painful group. After eliminating the influence of different pain intensity ratings on cerebral responses, the painful group displayed augmented responses in the limbic and striatal structures, including the perigenual anterior cingulate cortex (ACC), superior frontal gyrus, medial thalamus, anterior insular cortex, lentiform nucleus (LN), and premotor area. Among these regions, blood oxygen level-dependent (BOLD) signals in the ACC and LN were correlated with pain ratings to thermal stimulations in the painful group. Furthermore, activation maps of a simple regression analysis as well as a region of interest analysis revealed that responses in these limbic and striatal circuits paralleled the duration of neuropathic pain. However, in the painless group, BOLD signals in the primary somatosensory cortex and ACC were reduced. These results suggest that enhanced limbic and striatal activations underlie maladaptive responses after cutaneous nerve degeneration, which contributed to the development and maintenance of burning pain and thermal hyperalgesia in diabetes. Hum Brain Mapp 34:2733-2746, 2013. © 2012 Wiley Periodicals, Inc. PMID:22522975

Tseng, Ming-Tsung; Chiang, Ming-Chang; Chao, Chi-Chao; Tseng, Wen-Yih I; Hsieh, Sung-Tsang

2012-04-21

289

Quantitative in vivo assessment of radiation injury of the liver using Gd-EOB-DTPA enhanced MRI: tolerance dose of small liver volumes  

PubMed Central

Backround Hepatic radiation toxicity restricts irradiation of liver malignancies. Better knowledge of hepatic tolerance dose is favourable to gain higher safety and to optimize radiation regimes in radiotherapy of the liver. In this study we sought to determine the hepatic tolerance dose to small volume single fraction high dose rate irradiation. Materials and methods 23 liver metastases were treated by CT-guided interstitial brachytherapy. MRI was performed 3 days, 6, 12 and 24 weeks after therapy. MR-sequences were conducted with T1-w GRE enhanced by hepatocyte-targeted Gd-EOB-DTPA. All MRI data sets were merged with 3D-dosimetry data. The reviewer indicated the border of hypointensity on T1-w images (loss of hepatocyte function) or hyperintensity on T2-w images (edema). Based on the volume data, a dose-volume-histogram was calculated. We estimated the threshold dose for edema or function loss as the D90, i.e. the dose achieved in at least 90% of the pseudolesion volume. Results At six weeks post brachytherapy, the hepatocyte function loss reached its maximum extending to the former 9.4Gy isosurface in median (i.e., ?9.4Gy dose exposure led to hepatocyte dysfunction). After 12 and 24 weeks, the dysfunctional volume had decreased significantly to a median of 11.4Gy and 14Gy isosurface, respectively, as a result of repair mechanisms. Development of edema was maximal at six weeks post brachytherapy (9.2Gy isosurface in median), and regeneration led to a decrease of the isosurface to a median of 11.3Gy between 6 and 12 weeks. The dose exposure leading to hepatocyte dysfunction was not significantly different from the dose provoking edema. Conclusion Hepatic injury peaked 6 weeks after small volume irradiation. Ongoing repair was observed up to 6 months. Individual dose sensitivity may differ as demonstrated by a relatively high standard deviation of threshold values in our own as well as all other published data.

2011-01-01

290

AUR memorial award--1988. MRI enhancement of perfused tissues using chromium labeled red blood cells as an intravascular contrast agent  

SciTech Connect

It has been demonstrated that chromium (Cr) labeling significantly decreases the relaxation times of packed red blood cells (RBCs). In this study, the spin-lattice relaxation time (T1) of human red cells was shortened from 836 ms to 29 ms and the spin-spin relaxation time (T2) shortened from 134 ms to 18 ms, when the cells were labeled at a Cr incubation concentration of 50 mM. Labeling of canine cells at 50 mM resulted in a T1 of 36 ms and a T2 of 26 ms. A labeling concentration of 10 mM produced similar relaxation enhancement, with uptake of 47% of the available Cr, and was determined to be optimal. The enhancement of longitudinal and transverse relaxation rates (1/T1,-1/T2) per amount of hemoglobin-bound Cr are 6.9 s-1 mM-1 and 9.8 s-1 mM-1 respectively, different from those of a pure Cr+3 solution. Labeling cells at 10 mM decreased the survival half-time in vivo from 16.6 days to 4.7 days in dogs. No difference in red cell survival was found with the use of hetero-transfusion versus auto-transfusion of labeled RBCs. Significant shortening of the T1 (912 ms to 266 ms, P = .03) and T2 (90 ms to 70 ms, P = .006) of spleen and the T1 (764 ms to 282 ms, P = .005) and the T2 (128 ms to 86 ms, P = .005) of liver occurred when 10% of the RBC mass of dogs was exchanged with Cr labeled cells. Liver and spleen spin density changes (P greater than 0.23) and muscle spin density and relaxation changes (P greater than 0.4) were insignificant. The in vivo T1 of a canine spleen which had been infarcted did not change following transfusion with labeled cells, where the T1 of liver did shorten. We believe this preliminary study suggests that Cr labeled red cells may have the potential to become an intravascular magnetic resonance imaging contrast agent.

Eisenberg, A.D.; Conturo, T.E.; Price, R.R.; Holburn, G.E.; Partain, C.L.; James, A.E. Jr. (Vanderbilt Univ. Medical Center, Nashville, TN (USA))

1989-10-01

291

A model-constrained Monte Carlo method for blind arterial input function estimation in dynamic contrast-enhanced MRI: II. In vivo results  

NASA Astrophysics Data System (ADS)

Accurate quantification of pharmacokinetic model parameters in tracer kinetic imaging experiments requires correspondingly accurate determination of the arterial input function (AIF). Despite significant effort expended on methods of directly measuring patient-specific AIFs in modalities as diverse as dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), dynamic positron emission tomography (PET), and perfusion computed tomography (CT), fundamental and technical difficulties have made consistent and reliable achievement of that goal elusive. Here, we validate a new algorithm for AIF determination, the Monte Carlo blind estimation (MCBE) method (which is described in detail and characterized by extensive simulations in a companion paper), by comparing AIFs measured in DCE-MRI studies of eight brain tumor patients with results of blind estimation. Blind AIFs calculated with the MCBE method using a pool of concentration-time curves from a region of normal brain tissue were found to be quite similar to the measured AIFs, with statistically significant decreases in fit residuals observed in six of eight patients. Biases between the blind and measured pharmacokinetic parameters were the dominant source of error. Averaged over all eight patients, the mean biases were +7% in K trans, 0% in kep, -11% in vp and +10% in ve. Corresponding uncertainties (median absolute deviation from the best fit line) were 0.0043?min-1 in K trans, 0.0491 min-1 in kep, 0.29% in vp and 0.45% in ve. The use of a published population-averaged AIF resulted in larger mean biases in three of the four parameters (-23% in K trans, -22% in kep, -63% in vp), with the bias in ve unchanged, and led to larger uncertainties in all four parameters (0.0083 min-1 in K trans, 0.1038 min-1 in kep, 0.31% in vp and 0.95% in ve). When blind AIFs were calculated from a region of tumor tissue, statistically significant decreases in fit residuals were observed in all eight patients despite larger deviations of these blind AIFs from the measured AIFs. The observed decrease in root-mean-square fit residuals between the normal brain and tumor tissue blind AIFs suggests that the local blood supply in tumors is measurably different from that in normal brain tissue and that the proposed method is able to discriminate between the two. We have shown the feasibility of applying the MCBE algorithm to DCE-MRI data acquired in brain, finding generally good agreement with measured AIFs and decreased biases and uncertainties relative to the use of a population-averaged AIF. These results demonstrate that the MCBE algorithm is a useful alternative to direct AIF measurement in cases where acquisition of high-quality arterial input function data is difficult or impossible.

Schabel, Matthias C.; DiBella, Edward V. R.; Jensen, Randy L.; Salzman, Karen L.

2010-08-01

292

Neural correlates of retrieval-based memory enhancement: An fMRI study of the testing effect.  

PubMed

Restudying material is a common method for learning new information, but not necessarily an effective one. Research on the testing effect shows that practice involving retrieval from memory can facilitate later memory in contrast to passive restudy. Despite extensive behavioral work, the brain processes that make retrieval an effective learning strategy remain unclear. In the present experiment, we explored how initially retrieving items affected memory a day later as compared to a condition involving traditional restudy. In contrast to restudy, initial testing that contributed to future memory success was associated with engagement of several regions including the anterior hippocampus, lateral temporal cortices, and medial prefrontal cortex (PFC). Additionally, testing enhanced hippocampal connectivity with ventrolateral PFC and midline regions. These findings indicate that the testing effect may be contingent on processes that are typically thought to support memory success at encoding (e.g. relational binding, selection and elaboration of semantically-related information) in addition to those more often associated with retrieval (e.g. memory search). PMID:23607935

Wing, Erik A; Marsh, Elizabeth J; Cabeza, Roberto

2013-04-19

293

Application of direct virtual coil to dynamic contrast-enhanced MRI and MR angiography with data-driven parallel imaging.  

PubMed

PURPOSE: To demonstrate the feasibility of direct virtual coil (DVC) in the setting of 4D dynamic imaging used in multiple clinical applications. THEORY AND METHODS: Three dynamic imaging applications were chosen: pulmonary perfusion, liver perfusion, and peripheral MR angiography (MRA), with 18, 11, and 10 subjects, respectively. After view-sharing, the k-space data were reconstructed twice: once with channel-by-channel (CBC) followed by sum-of-squares coil combination and once with DVC. Images reconstructed using CBC and DVC were compared and scored based on overall image quality by two experienced radiologists using a five-point scale. RESULTS: The CBC and DVC showed similar image quality in image domain. Time course measurements also showed good agreement in the temporal domain. CBC and DVC images were scored as equivalent for all pulmonary perfusion cases, all liver perfusion cases, and four of the 10 peripheral MRA cases. For the remaining six peripheral MRA cases, DVC were scored as slightly better (not clinically significant) than the CBC images by Radiologist A and as equivalent by Radiologist B. CONCLUSION: For dynamic contrast-enhanced MR applications, it is clinically feasible to reduce image reconstruction time while maintaining image quality and time course measurement using the DVC technique. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc. PMID:23441013

Wang, Kang; Beatty, Philip J; Nagle, Scott K; Reeder, Scott B; Holmes, James H; Rahimi, Mahdi S; Bell, Laura C; Korosec, Frank R; Brittain, Jean H

2013-02-25

294

MRI of active otosclerosis  

Microsoft Academic Search

Our aim was to determine whether MRI reliably shows pathology in patients with active otosclerosis (otospongiosis). We studied\\u000a five patients with clinical and audiometric signs of this disorder and positive findings on high-resolution CT and tympanocochlear\\u000a scintigraphy. Contrast enhancement of otospongiotic lesions was found in all affected ears, and could be topographically related\\u000a to demineralised otospongiotic foci on CT. In

S. Ziyeh; A. Berlis; U. H. Ross; M. J. Reinhardt; M. Schumacher

1997-01-01

295

Morphological and functional midbrain phenotypes in Fibroblast Growth Factor 17 mutant mice detected by Mn-enhanced MRI  

PubMed Central

With increasing efforts to develop and utilize mouse models of a variety of neuro-developmental diseases, there is an urgent need for sensitive neuroimaging methods that enable in vivo analysis of subtle alterations in brain anatomy and function in mice. Previous studies have shown that the brains of Fibroblast Growth Factor 17 null mutants (Fgf17?/?) have anatomical abnormalities in the inferior colliculus (IC)–the auditory midbrain–and minor foliation defects in the cerebellum. In addition, changes in the expression domains of several cortical patterning genes were detected, without overt changes in forebrain morphology. Recently, it has also been reported that Fgf17?/? mutants have abnormal vocalization and social behaviors, phenotypes that could reflect molecular changes in the cortex and/or altered auditory processing / perception in these mice. We used manganese (Mn)-enhanced magnetic resonance imaging (MEMRI) to analyze the anatomical phenotype of Fgf17?/? mutants in more detail than achieved previously, detecting changes in IC, cerebellum, olfactory bulb, hypothalamus and frontal cortex. We also used MEMRI to characterize sound-evoked activity patterns, demonstrating a significant reduction of the active IC volume in Fgf17?/? mice. Furthermore, tone-specific (16- and 40-kHz) activity patterns in the IC of Fgf17?/? mice were observed to be largely overlapping, in contrast to the normal pattern, separated along the dorsal-ventral axis. These results demonstrate that Fgf17 plays important roles in both the anatomical and functional development of the auditory midbrain, and show the utility of MEMRI for in vivo analyses of mutant mice with subtle brain defects.

Yu, Xin; Nieman, Brian J.; Sudarov, Anamaria; Szulc, Kamila U.; Abdollahian, Davood J.; Bhatia, Nitin; Lalwani, Anil K.; Joyner, Alexandra L.; Turnbull, Daniel H.

2011-01-01

296

In vivo evaluation of retinal and callosal projections in early postnatal development and plasticity using manganese-enhanced MRI and diffusion tensor imaging.  

PubMed

The rodents are an excellent model for understanding the development and plasticity of the visual system. In this study, we explored the feasibility of Mn-enhanced MRI (MEMRI) and diffusion tensor imaging (DTI) at 7 T for in vivo and longitudinal assessments of the retinal and callosal pathways in normal neonatal rodent brains and after early postnatal visual impairments. Along the retinal pathways, unilateral intravitreal Mn2+ injection resulted in Mn2+ uptake and transport in normal neonatal visual brains at postnatal days (P) 1, 5 and 10 with faster Mn2+ clearance than the adult brains at P60. The reorganization of retinocollicular projections was also detected by significant Mn2+ enhancement by 2%-10% in the ipsilateral superior colliculus (SC) of normal neonatal rats, normal adult mice and adult rats after neonatal monocular enucleation (ME) but not in normal adult rats or adult rats after monocular deprivation (MD). DTI showed a significantly higher fractional anisotropy (FA) by 21% in the optic nerve projected from the remaining eye of ME rats compared to normal rats at 6 weeks old, likely as a result of the retention of axons from the ipsilaterally uncrossed retinal ganglion cells, whereas the anterior and posterior retinal pathways projected from the enucleated or deprived eyes possessed lower FA after neonatal binocular enucleation (BE), ME and MD by 22%-56%, 18%-46% and 11%-15% respectively compared to normal rats, indicative of neurodegeneration or immaturity of white matter tracts. Along the visual callosal pathways, intracortical Mn2+ injection to the visual cortex of BE rats enhanced a larger projection volume by about 74% in the V1/V2 transition zone of the contralateral hemisphere compared to normal rats, without apparent DTI parametric changes in the splenium of corpus callosum. This suggested an adaptive change in interhemispheric connections and spatial specificity in the visual cortex upon early blindness. The results of this study may help determine the mechanisms of axonal uptake and transport, microstructural reorganization and functional activities in the living visual brains during development, diseases, plasticity and early interventions in a global and longitudinal setting. PMID:21985904

Chan, Kevin C; Cheng, Joe S; Fan, Shujuan; Zhou, Iris Y; Yang, Jian; Wu, Ed X

2011-10-01

297

Conventional MRI evaluation of gliomas  

PubMed Central

MRI using T1 weighted, T2 weighted and gadolinium-enhanced sequences plays a central clinical role in diagnosis, characterisation, surveillance and therapeutic monitoring of gliomas. Such conventional MRI protocols provide high resolution multiplanar structural information, and substantially improved tissue characterisation compared with CT. However, the MRI signal lacks biological specificity, e.g. T2 weighted dependent signal abnormality is dominated by tissue water content, and contrast enhancement reflects a non-specific increase in blood-brain barrier permeability. This limits non-invasive glioma diagnosis, characterisation and therapeutic planning and assessment of active tumour load may be confounded by treatment-related effects. The complex features of glioma morphology and often subtle changes between MRI examinations are also frequently difficult to detect reliably by visual inspection of the images, even by an experienced radiologist. Moreover, the most widely used response criteria in clinical practice and therapeutic trials rely on linear measurements of enhancing tumour and are further challenged by the irregular shape and heterogeneous composition of gliomas. This contributes to the poor correlation of these criteria with hard clinical endpoints. While conventional MRI is widely available and provides essential anatomical information, the lack of pathology-specific biomarkers available from standard MRI sequences and methods of image analysis used limit overall diagnostic and prognostic efficacy of the examination.

Upadhyay, N; Waldman, A D

2011-01-01

298

Communication: The distinguishable cluster approximation.  

PubMed

We present a method that accurately describes strongly correlated states and captures dynamical correlation. It is derived as a modification of coupled-cluster theory with single and double excitations (CCSD) through consideration of particle distinguishability between dissociated fragments, whilst retaining the key desirable properties of particle-hole symmetry, size extensivity, invariance to rotations within the occupied and virtual spaces, and exactness for two-electron subsystems. The resulting method, called the distinguishable cluster approximation, smoothly dissociates difficult cases such as the nitrogen molecule, with the modest N(6) computational cost of CCSD. Even for molecules near their equilibrium geometries, the new model outperforms CCSD. It also accurately describes the massively correlated states encountered when dissociating hydrogen lattices, a proxy for the metal-insulator transition, and the fully dissociated system is treated exactly. PMID:23862916

Kats, Daniel; Manby, Frederick R

2013-07-14

299

Distinguishing cellulitis from its mimics.  

PubMed

Distinguishing true cellulitis from its many imitators is challenging but critical if we are to avoid unnecessary use of antibiotics and delays in treatment. Common imitators of cellulitis are stasis dermatitis, lipodermatosclerosis, contact dermatitis, lymphedema, eosinophilic cellulitis, and papular urticaria. Specific criteria do not exist for the diagnosis of cellulitis, but the alert physician can find clues in the history and physical examination that point toward cellulitis. PMID:22854433

Keller, Emily C; Tomecki, Kenneth J; Alraies, M Chadi

2012-08-01

300

Portable MRI  

SciTech Connect

This project proposes to: (1) provide the power of MRI to situations where it presently isn't available; (2) perform the engineering required to move from lab to a functional prototype; and (3) leverage significant existing infrastructure and capability in ultra-low field MRI. The reasons for doing this: (1) MRI is the most powerful tool for imaging soft-tissue (e.g. brain); (2) Billions don't have access due to cost or safety issues; (3) metal will heat/move in high magnetic fields; (4) Millions of cases of traumatic brain injury in US alone; (5) even more of non-traumatic brain injury; (6) (e.g. stroke, infection, chemical exposure); (7) Need for early diagnostic; (8) 'Signature' wound of recent conflicts; (9) 22% of injuries; (10) Implications for post-traumatic stress disorder; and (11) chronic traumatic encephalopathy.

Espy, Michelle A. [Los Alamos National Laboratory

2012-06-29

301

Quantitative Contrast-Enhanced First-Pass Cardiac Perfusion MRI at 3T with Accurate Arterial Input Function and Myocardial Wall Enhancement  

PubMed Central

Purpose To develop, and validate in vivo, a robust quantitative first-pass perfusion cardiovascular MR (CMR) method with accurate arterial input function (AIF) and myocardial wall enhancement. Materials and Methods A saturation-recovery (SR) pulse sequence was modified to sequentially acquire multiple slices after a single non-selective saturation pulse at 3T. In each heartbeat, an AIF image is acquired in the aortic root with a short TD (50ms), followed by the acquisition of myocardial images with longer TD values (~150-400ms). Longitudinal relaxation rates (R1=1/T1) were calculated using an ideal saturation recovery equation based on the Bloch equation, and corresponding gadolinium contrast concentrations were calculated assuming fast water exchange condition. The proposed method was validated against a reference multi-point SR method by comparing their respective R1 measurements in the blood and left ventricular myocardium, prior to and at multiple time-points following contrast injections, in 7 volunteers. Results R1 measurements with the proposed method and reference multi-point method were strongly correlated (r>0.88, P<10?5) and in good agreement (mean difference ±1.96 standard deviation 0.131 ± 0.317 / 0.018 ± 0.140 s?1 for blood/myocardium, respectively). Conclusion The proposed quantitative first-pass perfusion CMR method measured accurate R1 values for quantification of AIF and myocardial wall contrast agent concentrations in 3 cardiac short-axis slices, in a total acquisition time of 523ms per heartbeat.

Breton, Elodie; Kim, Daniel; Chung, Sohae; Axel, Leon

2011-01-01

302

HO-1 gene overexpression enhances the beneficial effects of superparamagnetic iron oxide labeled bone marrow stromal cells transplantation in swine hearts underwent ischemia/reperfusion: an MRI study.  

PubMed

To determine the effect of intracoronary transfer of superparamagnetic iron oxide (SPIO) labeled heme oxygenase-1 (HO-1) overexpressed bone marrow stromal cells (BMSCs) in a porcine myocardial ischemia/reperfusion model. Cell apoptosis was assayed and supernatant cytokine concentrations were measured in BMSCs that underwent hypoxia/reoxygen in vitro. Female mini-swines that underwent 1 h LAD occlusion followed by 1 h reperfusion were randomly allocated to receive intracoronary saline (control), 1 x 10(7) SPIO-labeled BMSCs transfected with pcDNA3.1-Lacz plasmid (Lacz-BMSCs), pcDNA3.1-human HO-1 (HO-1-BMSCs), pcDNA3.1-hHO-1 pretreated with a HO inhibitor, tin protoporphyrin (SnPP, n = 10 each). MRI and postmortem histological analysis were made at 1 week or 3 months thereafter. Post hypoxia/reoxygen in vitro, apoptosis was significantly reduced, supernatant VEGF significantly increased while TNF-alpha and IL-6 significantly reduced in HO-1-BMSCs group compared with Lacz-BMSCs group (all p < 0.05). Myocardial expression of VEGF was significantly higher in HO-1-BMSCs than in Lacz-BMSCs group at 1 week post transplantation (all p < 0.05). Signal voids induced by the SPIO were detected in the peri-infarction region in all BMSC groups at 1 week but not at 3 months post transplantation and the extent of the hypointense signal was the highest in HO-1-BMSCs group, and histological analysis showed that signal voids represented cardiac macrophages that engulfed the SPIO-labeled BMSCs. Pretreatment with SnPP significantly attenuated the beneficial effects of HO-1-BMSCs. Transplantation of HO-1-overexpressed BMSCs significantly enhanced the beneficial effects of BMSCs on improving cardiac function in this model. PMID:20033189

Jiang, Yibo; Chen, Lijuan; Tang, Yaoliang; Ma, Genshan; Shen, Chengxing; Qi, Chunmei; Zhu, Qi; Yao, Yuyu; Liu, Naifeng

2009-12-24

303

Nanomaterials in Medicine Special Feature Sackler Colloquium: Preparation and initial characterization of biodegradable particles containing gadolinium-DTPA contrast agent for enhanced MRI  

Microsoft Academic Search

Accurate imaging of atherosclerosis is a growing necessity for timely treatment of the disease. Magnetic resonance imaging (MRI) is a promising technique for plaque imaging. The goal of this study was to create polymeric particles of a small size with high loading of diethylenetriaminepentaacetic acid gadolinium (III) (Gd-DTPA) and demonstrate their usefulness for MRI. A water-in-oil-in-oil double emulsion solvent evaporation

Amber L. Doiron; Kevin Chu; Adeel Ali; Lisa Brannon-Peppas

2008-01-01

304

MRI in small brains displaying extensive plasticity  

Microsoft Academic Search

Manganese-enhanced magnetic resonance imaging (ME-MRI), blood oxygen-level-dependent functional MRI (BOLD fMRI) and diffusion tensor imaging (DTI) can now be applied to animal species as small as mice or songbirds. These techniques confirmed previous find- ings but are also beginning to reveal new phenomena that were difficult or impossible to study previously. These imaging techniques will lead to major technical and

Annemie Van der Linden; Vincent Van Meir; Tiny Boumans; Colline Poirier; Jacques Balthazart

2009-01-01

305

Gd-HOPO based high relaxivity MRI contrast agents  

PubMed Central

Conspectus Magnetic resonance imaging (MRI) is a particularly effective tool in medicine because of its high depth penetration (1 mm to 1 m) and ability to resolve different soft tissues. The MRI signal is generated by the relaxation of in vivo water molecule protons. MRI images can be improved by administering paramagnetic agents, which increase the relaxation rates of nearby water protons, thereby enhancing the MRI signal. The lanthanide cation Gd3+ is generally used because of its favorable electronic properties; high toxicity, however, necessitates strongly coordinating ligands to keep Gd3+ completely bound while in the patient. In this Account, we give a coordination chemistry overview of contrast agents (CAs) based on Gd-hydroxypyridinone (HOPO), which show improved MRI contrast and high thermodynamic stabilities. Tris-bidentate HOPO-based ligands developed in our laboratory were designed to complement the coordination preferences of Gd3+, especially its oxophilicity. The HOPO ligands provide a hexadentate coordination environment for Gd3+ in which all the donor atoms are oxygen. Because Gd3+ favors eight or nine coordination, this design provides two to three open sites for inner-sphere water molecules. These water molecules rapidly exchange with bulk solution, hence affecting the relaxation rates of bulk water molecules. The parameters affecting the efficiency of these contrast agents have been tuned to improve contrast while still maintaining a high thermodynamic stability for Gd3+ binding. The Gd-HOPO-based contrast agents surpass current commercially available agents because of a higher number of inner-sphere water molecules, rapid exchange of inner-sphere water molecules via an associative mechanism, and a long electronic relaxation time. The contrast enhancement provided by these agents is at least twice that of commercial contrast agents, which are based on polyaminocarboxylate ligands. Advances in MRI technology have made significant contributions to the improvement of clinical diagnostics by allowing visualization of underlying pathology. However, understanding the mechanism of a disease at the molecular level requires improved imaging sensitivity. The ultimate goal is to visually distinguish between different disease targets or markers—such as enzymes, hormones, proteins, or small molecules—at biologically relevant concentrations (millimolar to nanomolar). Although MRI techniques can provide images of the organs and tissues in which these biomarkers are regulated, the high sensitivity required to visualize the biological targets within the tissues is currently lacking—contrast enhancements of 50-fold beyond current agents are required to achieve this goal. According to the theory of paramagnetic relaxation, the contrast enhancement can be further improved by slowing the tumbling rate of the MRI agent. Theoretically, this enhancement would be greater for contrast agents with an optimal rate of water exchange. The Gd-HOPO-based contrast agents have optimal water-exchange rates, whereas the commercial agents have slower non-optimal water-exchange rates; thus, the Gd-HOPO agents are ideal for attachment to macromolecules, which will slow down the tumbling rate and increase contrast. This strategy has been recently tested with the Gd-HOPO agents via covalent attachment to virus capsids, affording contrast enhancements 10-fold beyond commercial agents.

Datta, Ankona; Raymond, Kenneth N.

2009-01-01

306

MRI of the knee with arthroscopic correlation.  

PubMed

Major advances in MRI and arthroscopy have allowed for enhanced diagnosis and subsequent management of ligamentous and soft tissue injuries of the knee. Recognition of the appearance of acute ACL and PCL injuries on MRI can enhance arthroscopic reconstruction. PCL injuries are often more subtle and can present with indirect signs. T2-weighted MRI imaging can examine which structures have been damaged in the posterolateral corner which may manifest arthroscopically as a drive-through sign. Characterization of PLC, meniscus, MCL injuries and OCD lesions on MRI have remarkable correlation with arthroscopic findings. This article focuses on current understanding of how MRI and athroscopy can enhance treatment of ligamentous and soft tissue injuries of the knee. PMID:23773879

Griffin, Justin W; Miller, Mark D

2013-05-09

307

Distinguishing Ichthyoses by Protein Profiling  

PubMed Central

To explore the usefulness of protein profiling for characterization of ichthyoses, we here determined the profile of human epidermal stratum corneum by shotgun proteomics. Samples were analyzed after collection on tape circles from six anatomic sites (forearm, palm, lower leg, forehead, abdomen, upper back), demonstrating site-specific differences in profiles. Additional samples were collected from the forearms of subjects with ichthyosis vulgaris (filaggrin (FLG) deficiency), recessive X-linked ichthyosis (steroid sulfatase (STS) deficiency) and autosomal recessive congenital ichthyosis type lamellar ichthyosis (transglutaminase 1 (TGM1) deficiency). The ichthyosis protein expression patterns were readily distinguishable from each other and from phenotypically normal epidermis. In general, the degree of departure from normal was lower from ichthyosis vulgaris than from lamellar ichthyosis, parallel to the severity of the phenotype. Analysis of samples from families with ichthyosis vulgaris and concomitant modifying gene mutations (STS deficiency, GJB2 deficiency) permitted correlation of alterations in protein profile with more complex genetic constellations.

Rice, Robert H.; Bradshaw, Katie M.; Durbin-Johnson, Blythe P.; Rocke, David M.; Eigenheer, Richard A.; Phinney, Brett S.; Schmuth, Matthias; Gruber, Robert

2013-01-01

308

Distinguishing ichthyoses by protein profiling.  

PubMed

To explore the usefulness of protein profiling for characterization of ichthyoses, we here determined the profile of human epidermal stratum corneum by shotgun proteomics. Samples were analyzed after collection on tape circles from six anatomic sites (forearm, palm, lower leg, forehead, abdomen, upper back), demonstrating site-specific differences in profiles. Additional samples were collected from the forearms of subjects with ichthyosis vulgaris (filaggrin (FLG) deficiency), recessive X-linked ichthyosis (steroid sulfatase (STS) deficiency) and autosomal recessive congenital ichthyosis type lamellar ichthyosis (transglutaminase 1 (TGM1) deficiency). The ichthyosis protein expression patterns were readily distinguishable from each other and from phenotypically normal epidermis. In general, the degree of departure from normal was lower from ichthyosis vulgaris than from lamellar ichthyosis, parallel to the severity of the phenotype. Analysis of samples from families with ichthyosis vulgaris and concomitant modifying gene mutations (STS deficiency, GJB2 deficiency) permitted correlation of alterations in protein profile with more complex genetic constellations. PMID:24130705

Rice, Robert H; Bradshaw, Katie M; Durbin-Johnson, Blythe P; Rocke, David M; Eigenheer, Richard A; Phinney, Brett S; Schmuth, Matthias; Gruber, Robert

2013-10-09

309

MRI-based sector analysis enhances prostate palladium-103 brachytherapy quality assurance in a phase II prospective trial of men with intermediate-risk localized prostate cancer.  

PubMed

PURPOSE: Palladium-103 ((103)Pd) may be superior to other isotopes in brachytherapy for localized intermediate-risk prostate cancer because of its relatively short half-life, higher initial dose rate, and greater dose heterogeneity within the target volume; these properties also underscore the need for accurate target delineation and postimplant quality assurance. We assessed the use of prostate sector analysis based on MRI for quality assurance after (103)Pd monotherapy. METHODS AND MATERIALS: Fifty men with intermediate-risk prostate cancer underwent (103)Pd monotherapy in a prospective phase II trial at MD Anderson Cancer Center. Dosimetric analyses on day 30 after the implant were done using both CT and fused CT/MRI scans. Dosimetric variables were assessed for the entire prostate and for each of three or six sectors. Volumes and dosimetric variables were compared with paired t tests. RESULTS: Postimplant dosimetric variables for the entire prostate were significantly different on CT vs. CT/MRI (p = 0.019 for V100 and p < 0.01 for D90). Prostate volumes were smaller on the CT/MRI scans (p < 0.00001). The base sector contributed the greatest difference, with doses based on CT/MRI lower than those based on CT (p < 0.01 for V100 and D90). To date, these lower base doses have not affected biochemical outcomes for patients with disease in prostate base biopsy samples. CONCLUSIONS: CT/MRI is more precise than CT for prostate volume delineation and dosimetric quality assessment and thus provides superior heterogeneity control assessment after (103)Pd monotherapy implants. PMID:23669149

Takiar, Vinita; Pugh, Thomas J; Swanson, David; Kudchadker, Rajat J; Bruno, Teresa L; McAvoy, Sarah; Mahmood, Usama; Frank, Steven J

2013-05-11

310

Current Status and New Developments in Breast MRI  

PubMed Central

Summary Breast magnetic resonance imaging (MRI) is the most sensitive imaging modality for the detection of breast cancer. Its specificity is equivalent to that of mammography. Nowadays, breast MRI is an absolutely essential breast imaging method. Technical innovations allow dynamic contrast-enhanced (DCE) MRI of both breasts with high image quality. Thereby, DCE breast MRI should always be performed with regard to current standards. New quantitative techniques such as diffusion-weighted MRI are promising. However, they still have potential pitfalls, in particular with regard to the diagnosis of non-mass lesions and small breast lesions. Ongoing technical innovations can possibly help to further optimize breast MRI.

Siegmann, Katja C.; Kramer, Bernhard; Claussen, Claus

2011-01-01

311

Distinguishing ordinal and disordinal interactions.  

PubMed

Re-parameterized regression models may enable tests of crucial theoretical predictions involving interactive effects of predictors that cannot be tested directly using standard approaches. First, we present a re-parameterized regression model for the Linear × Linear interaction of 2 quantitative predictors that yields point and interval estimates of 1 key parameter-the crossover point of predicted values-and leaves certain other parameters unchanged. We explain how resulting parameter estimates provide direct evidence for distinguishing ordinal from disordinal interactions. We generalize the re-parameterized model to Linear × Qualitative interactions, where the qualitative variable may have 2 or 3 categories, and then describe how to modify the re-parameterized model to test moderating effects. To illustrate our new approach, we fit alternate models to social skills data on 438 participants in the National Institute of Child Health and Human Development Study of Early Child Care. The re-parameterized regression model had point and interval estimates of the crossover point that fell near the mean on the continuous environment measure. The disordinal form of the interaction supported 1 theoretical model-differential-susceptibility-over a competing model that predicted an ordinal interaction. PMID:22984788

Widaman, Keith F; Helm, Jonathan L; Castro-Schilo, Laura; Pluess, Michael; Stallings, Michael C; Belsky, Jay

2012-09-17

312

Play the MRI Game  

MedlinePLUS

... about the Nobel Prize Alfred Nobel's Life and Work Teachers' Questionnaire MRI Play MRI the Magnetic Miracle Game About the game In the MRI imaging technique, strong magnets and radio waves are used for getting images of inner ...

313

Breast MR with special focus on DW-MRI and DCE-MRI  

PubMed Central

Abstract The use of magnetic resonance imaging (MRI) for the assessment of breast lesions was first described in the 1970s; however, its wide application in clinical routine is relatively recent. The basic principles for diagnosis of a breast lesion rely on the evaluation of signal intensity in T2-weighted sequences, on morphologic assessment and on the evaluation of contrast enhancement behaviour. The quantification of dynamic contrast behaviour by dynamic contrast-enhanced (DCE) MRI and evaluation of the diffusivity of water molecules by means of diffusion-weighted MRI (DW-MRI) have shown promise in the work-up of breast lesions. Therefore, breast MRI has gained a role for all indications that could benefit from its high sensitivity, such as detection of multifocal lesions, detection of contralateral carcinoma and in patients with familial disposition. Breast MRI has been shown to have a role in monitoring of neoadjuvant chemotherapy, for the evaluation of therapeutic results during the course of therapy. Breast MRI can improve the determination of the remaining tumour size at the end of therapy in patients with a minor response. DCE-MRI and DW-MRI have shown potential for improving the early assessment of tumour response to therapy and the assessment of residual tumour after the end of therapy. Breast MRI is important in the postoperative work-up of breast cancers. High sensitivity and specificity have been reported for the diagnosis of recurrence; however, pitfalls such as liponecrosis and changes after radiation therapy have to be carefully considered.

Bonello, L.; Priolo, F.; Summers, P.; Bellomi, M.

2011-01-01

314

Breast cancer classification with mammography and DCE-MRI  

NASA Astrophysics Data System (ADS)

Since different imaging modalities provide complementary information regarding the same lesion, combining information from different modalities may increase diagnostic accuracy. In this study, we investigated the use of computerized features of lesions imaged via both full-field digital mammography (FFDM) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in the classification of breast lesions. Using a manually identified lesion location, i.e. a seed point on FFDM images or a ROI on DCE-MRI images, the computer automatically segmented mass lesions and extracted a set of features for each lesion. Linear stepwise feature selection was firstly performed on single modality, yielding one feature subset for each modality. Then, these selected features served as the input to another feature selection procedure when extracting useful information from both modalities. The selected features were merged by linear discriminant analysis (LDA) into a discriminant score. Receiver operating characteristic (ROC) analysis was used to evaluate the performance of the selected feature subset in the task of distinguishing between malignant and benign lesions. From a FFDM database with 321 lesions (167 malignant and 154 benign), and a DCE-MRI database including 181 lesions (97 malignant and 84 benign), we constructed a multi-modality dataset with 51 lesions (29 malignant and 22 benign). With leave-one-out-by-lesion evaluation on the multi-modality dataset, the mammography-only features yielded an area under the ROC curve (AUC) of 0.62 +/- 0.08 and the DCE-MRI-only features yielded an AUC of 0.94+/-0.03. The combination of these two modalities, which included a spiculation feature from mammography and a kinetic feature from DCE-MRI, yielded an AUC of 0.94. The improvement of combining multi-modality information was statistically significant as compared to the use of mammography only (p=0.0001). However, we failed to show the statistically significant improvement as compared to DCE-MRI, with the limited multi-modality dataset (p=0.22).

Yuan, Yading; Giger, Maryellen L.; Li, Hui; Sennett, Charlene

2009-02-01

315

A case report of pseudoprogression followed by complete remission after proton-beam irradiation for a low-grade glioma in a teenager: the value of dynamic contrast-enhanced MRI.  

PubMed

A fourteen years-old boy was treated post-operatively with proton therapy for a recurrent low-grade oligodendroglioma located in the tectal region. Six months after the end of irradiation (RT), a new enhancing lesion appeared within the radiation fields. To differentiate disease progression from radiation-induced changes, dynamic susceptibility contrast-enhanced (DSCE) MRI was used with a T2* sequence to study perfusion and permeability characteristics simultaneously. Typically, the lesion showed hypoperfusion and hyperpermeability compared to the controlateral normal brain. Without additional treatment but a short course of steroids, the image disappeared over a six months period allowing us to conclude for a pseudo-progression. The patient is alive in complete remission more than 2 years post-RT. PMID:20132555

Meyzer, Candice; Dhermain, Frédéric; Ducreux, Denis; Habrand, Jean-Louis; Varlet, Pascale; Sainte-Rose, Christian; Dufour, Christelle; Grill, Jacques

2010-02-04

316

Small hypervascular hepatocellular carcinomas: value of diffusion-weighted imaging compared with "washout" appearance on dynamic MRI  

PubMed Central

Objective To compare the value of diffusion-weighted MRI (DWI) with the venous “washout” appearance during dynamic MRI for the assessment of small arterial hypervascular lesions in cirrhotic liver. Methods After exclusion of benign hypervascular lesions, including haemangiomas and subcapsular non-tumorous arterioportal shunts, indicated by typical imaging features, a total of 109 small arterial hypervascular lesions (0.5–3.0 cm in the longest diameter) in 65 patients with cirrhosis who underwent gadopentetate dimeglumine-enhanced dynamic MRI and DWI (b=50, 400, 800 s mm?2) at 1.5 T during a 16-month period were retrospectively analysed to determine the presence of venous washout during dynamic imaging or sustained hyperintensity upon increasing the b factor size on DWI. Results Among the 99 hypervascular hepatocellular carcinomas (HCCs), sustained hyperintensity on DWI (92/99, 93%) was more prevalent than the washout appearance (72/99, 72%) on dynamic MRI (p<0.001). Depending on the lesion size, subcentimetre-sized HCCs had a significantly lower prevalence of venous washout (13/30, 43%) than the sustained hyperintensity on DWI (27/30, 90%) (p=0.001). In all 10 hypervascular benign conditions, there was no venous washout on dynamic MRI and no sustained hyperintensity on DWI. Sensitivity and specificity for diagnosis of hypervascular HCCs were 92.9% and 100% in DWI and 72% and 100% in dynamic MRI, respectively. Conclusion Compared with the venous washout during dynamic imaging, DWI provides more reliable information in the MRI assessment of small hypervascular HCCs, distinguishing them from atypical hypervascular benign or pseudolesions. DWI could complement the early diagnosis of small hypervascular HCCs that do not display venous washout during dynamic imaging.

Kim, D J; Yu, J-S; Kim, J H; Chung, J-J; Kim, K W

2012-01-01

317

Distinguishing Stream Ciphers with Convolutional Filters  

Microsoft Academic Search

This paper presents a new type of distinguisher for the shrinking generator and the alternating-step generator with known\\u000a feedback polynomial and for the multiplexor generator. For the former the distinguisher is more efficient than existing ones\\u000a and for the latter it results in a complete breakdown of security. The distinguisher is conceptually very simple and lends\\u000a itself to theoretical analysis

Joan Daemen; Gilles Van Assche

2006-01-01

318

Environmentally responsive MRI contrast agents.  

PubMed

Biomedical imaging techniques can provide a vast amount of anatomical information, enabling diagnosis and the monitoring of disease and treatment profile. MRI uniquely offers convenient, non-invasive, high resolution tomographic imaging. A considerable amount of effort has been invested, across several decades, in the design of non toxic paramagnetic contrast agents capable of enhancing positive MRI signal contrast. Recently, focus has shifted towards the development of agents capable of specifically reporting on their local biochemical environment, where a switch in image contrast is triggered by a specific stimulus/biochemical variable. Such an ability would not only strengthen diagnosis but also provide unique disease-specific biochemical insight. This feature article focuses on recent progress in the development of MRI contrast switching with molecular, macromolecular and nanoparticle-based agents. PMID:24040650

Davies, Gemma-Louise; Kramberger, Iris; Davis, Jason J

2013-09-26

319

Association between bilateral asymmetry of kinetic features computed from the DCE-MRI images and breast cancer  

NASA Astrophysics Data System (ADS)

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) of breast yields high sensitivity but relatively lower specificity. To improve diagnostic accuracy of DCE-MRI, we investigated the association between bilateral asymmetry of kinetic features computed from the left and right breasts and breast cancer detection with the hypothesis that due to the growth of angiogenesis associated with malignant lesions, the average dynamic contrast enhancement computed from the breasts depicting malignant lesions should be higher than negative or benign breasts. To test this hypothesis, we assembled a database involving 130 DCE-MRI examinations including 81 malignant and 49 benign cases. We developed a computerized scheme that automatically segments breast areas depicted on MR images and computes kinetic features related to the bilateral asymmetry of contrast enhancement ratio between two breasts. An artificial neural network (ANN) was then used to classify between malignant and benign cases. To identify the optimal approach to compute the bilateral kinetic feature asymmetry, we tested 4 different thresholds to select the enhanced pixels (voxels) from DCE-MRI images and compute the kinetic features. Using the optimal threshold, the ANN had a classification performance measured by the area under the ROC curve of AUC=0.79+/-0.04. The positive and negative predictive values were 0.75 and 0.67, respectively. The study suggested that the bilateral asymmetry of kinetic features or contrast enhancement of breast background tissue could provide valuable supplementary information to distinguish between the malignant and benign cases, which can be fused into existing computer-aided detection schemes to improve classification performance.

Yang, Qian; Li, Lihua; Zhang, Juan; Zhang, Chengjie; Zheng, Bin

2013-03-01

320

MRI Findings of Pericardial Fat Necrosis: Case Report  

PubMed Central

Pericardial fat necrosis is an infrequent cause of acute chest pain and this can mimic acute myocardial infarction and acute pericarditis. We describe here a patient with the magnetic resonance imaging (MRI) findings of pericardial fat necrosis and this was correlated with the computed tomography (CT) findings. The MRI findings may be helpful for distinguishing pericardial fat necrosis from other causes of acute chest pain and from the fat-containing tumors in the cardiophrenic space of the anterior mediastinum.

Lee, Hyo Hyeok; Jung, Sang Sig; Jung, Seung Mun; Choi, Soo Jung; Shin, Dae Hee

2011-01-01

321

Ferumoxytol in clinical practice: implications for MRI.  

PubMed

Ferumoxytol is an iron-containing parenteral treatment for iron deficiency anemia that was recently approved by the Food and Drug Administration. The iron is in the form of a superparamagnetic iron oxide that causes T1, T2, and T2* shortening on magnetic resonance imaging (MRI). Furthermore, the drug has a long intravascular half-life of 14-15 hours; a standard dose can affect MRI for days to months. We describe a case in which a patient underwent contrast-enhanced MRI of the liver 2 days after receiving a dose of ferumoxytol, which was unknown to the radiology team. The blood pool and soft tissues were hyperintense on T1-weighted images, concealing enhancement from the gadolinium-based contrast agent that was administered during the exam and rendering the exam nondiagnostic. Radiologists must be aware of this potential effect in screening patients for MRI and interpreting exams. PMID:23097302

McCullough, Brendan J; Kolokythas, Orpheus; Maki, Jeffrey H; Green, Douglas E

2012-10-23

322

Outcome Classification of Preschool Children With Autism Spectrum Disorders Using MRI Brain Measures  

Microsoft Academic Search

ObjectiveTo test the hypothesis that a combination of magnetic resonance imaging (MRI) brain measures obtained during early childhood distinguish children with autism spectrum disorders (ASD) from typically developing children and is associated with functional outcome.

Natacha Akshoomoff; Catherine Lord; Alan J. Lincoln; Rachel Y. Courchesne; Ruth A. Carper; Jeanne Townsend; Eric Courchesne

2004-01-01

323

Engineering novel detectors and sensors for MRI.  

PubMed

Increasing detection sensitivity and image contrast have always been major topics of research in MRI. In this perspective, we summarize two engineering approaches to make detectors and sensors that have potential to extend the capability of MRI. The first approach is to integrate miniaturized detectors with a wireless powered parametric amplifier to enhance the detection sensitivity of remotely coupled detectors. The second approach is to microfabricate contrast agents with encoded multispectral frequency shifts, whose properties can be specified and fine-tuned by geometry. These two complementary approaches will benefit from the rapid development in nanotechnology and microfabrication which should enable new opportunities for MRI. PMID:23245489

Qian, Chunqi; Zabow, Gary; Koretsky, Alan

2012-11-29

324

The features of breast lymphoma on MRI.  

PubMed

Objective: To investigate the morphological features of breast lymphoma (BL) on MRI. Methods: MRI features of 20 patients with BL (12 primary and 8 secondary) were reviewed according to Breast Imaging-Reporting and Data System categories. Results: 19 cases were unilateral and 1 was bilateral. According to the enhanced images, of the 20 cases, BL presented as a mass in 11 (55%), as an enhancement with no mass effect in 7 (35%) and as a mass and mixed enhancement with no mass effect in 2 (10%). There were 38 masses and 44 lesions with no mass effect in our study. All lesions showed mild heterogeneous internal enhancement. For lesions with mass effect, the margins were smooth in 32% (12/38) and irregular in 68% (26/38); and the shape was oval in 87% (32/38). Kinetic curve assessment (13 cases, 38 lesions) revealed that the average initial rise rate was 104%. The type II enhancement curve appeared in 55% (21/38) of lesions. No significant differences between the primary and secondary BL were observed for any of the MRI features. Conclusion: BL mostly appeared oval with irregular margins showing mild heterogeneous internal enhancement and/or as enhanced lesions with no mass effect with mild heterogeneous internal enhancement. Advances in knowledge: Some special features on MRI are useful for the diagnosis of BL. PMID:24029630

Liu, K; Xie, P; Peng, W; Zhou, Z

2013-09-12

325

Stepwise heterogeneity analysis of breast tumors in perfusion DCE-MRI datasets  

NASA Astrophysics Data System (ADS)

The signal curves in perfusion dynamic contrast enhanced MRI (DCE-MRI) of cancerous breast tissue reveal valuable information about tumor angiogenesis. Pathological studies have illustrated that breast tumors consist of different subregions, especially with more homogeneous properties during their growth. Differences should be identifiable in DCEMRI signal curves if the characteristics of these sub-regions are related to the perfusion and angiogenesis. We introduce a stepwise clustering method which in a first step uses a new similarity measure. The new similarity measure (PM) compares how parallel washout phases of two curves are. To distinguish the starting point of the washout phase, a linear regression method is partially fitted to the curves. In the next step, the minimum signal value of the washout phase is normalized to zero. Finally, PM is calculated according to maximal variation among the point wise differences during washout phases. In the second step of clustering the groups of signal curves with parallel washout are clustered using Euclidean distance. The introduced method is evaluated on 15 DCE-MRI breast datasets with different types of breast tumors. The use of our new heterogeneity analysis is feasible in single patient examination and improves breast MR diagnostics.

Mohajer, Mojgan; Schmid, Volker J.; Engels, Nina A.; Noel, Peter B.; Rummeny, Ernst; Englmeier, Karl-Hans

2012-02-01

326

A comparison of MRI criteria for diagnosing pediatric ADEM and MS  

Microsoft Academic Search

BACKGROUND: Brain MRI is a useful tool for diagnosing inflammatory demyelinating disorders in children. However, it remains unclear which are the most reliable criteria for distinguishing multiple sclerosis (MS) from monophasic disorders such as acute disseminated encephalomyelitis (ADEM). We therefore compared the 4 current sets of MRI criteria in our Dutch pediatric cohort and determined which are the most useful

I. A. Ketelslegers; R. F. Neuteboom; M. Boon; C. E. Catsman-Berrevoets; R. Q. Hintzen

2010-01-01

327

Outcome Classification of Preschool Children with Autism Spectrum Disorders Using Mri Brain Measures.  

ERIC Educational Resources Information Center

Objective: To test the hypothesis that a combination of magnetic resonance imaging (MRI) brain measures obtained during early childhood distinguish children with autism spectrum disorders (ASD) from typically developing children and is associated with functional outcome. Method: Quantitative MRI technology was used to measure gray and white matter…

Akshoomoff, Natacha; Lord, Catherine; Lincoln, Alan J.; Courchesne, Rachel Y.; Carper, Ruth A.; Townsend, Jeanne; Courchesne, Eric

2004-01-01

328

Canalis basilaris medianus: MRI  

Microsoft Academic Search

We report the MRI appearances of an developmental anatomical variant of the basiocciput, with neuroimaging findings (CT and\\u000a MRI). Such variants are commonly asymptomatic, but may be associated with episodes of meningitis.

C. Jacquemin; T. M. Bosley; M. al Saleh; P. Mullaney

2000-01-01

329

MRI Acquisition ACRING-6677  

Cancer.gov

MRI Technical Acquisition (ACRIN-6677 Protocol) Required Hardware/Software: Most modern 1.5 Tesla or 3.0 Tesla MRI systems can adequately perform the required examinations. Under certain circumstances, older systems can also perform well, while on

330

Functional Imaging: CT and MRI  

PubMed Central

Synopsis Numerous imaging techniques permit evaluation of regional pulmonary function. Contrast-enhanced CT methods now allow assessment of vasculature and lung perfusion. Techniques using spirometric controlled MDCT allow for quantification of presence and distribution of parenchymal and airway pathology, Xenon gas can be employed to assess regional ventilation of the lungs and rapid bolus injections of iodinated contrast agent can provide quantitative measure of regional parenchymal perfusion. Advances in magnetic resonance imaging (MRI) of the lung include gadolinium-enhanced perfusion imaging and hyperpolarized helium imaging, which can allow imaging of pulmonary ventilation and .measurement of the size of emphysematous spaces.

van Beek, Edwin JR; Hoffman, Eric A

2008-01-01

331

MRI of the shoulder  

Microsoft Academic Search

This book reports on the use of magnetic resonance imaging (MRI) in evaluating shoulder disorders. The book gives detailed information on MRI techniques and shoulder anatomy, describes and illustrates MRI findings for a wide range of shoulder disorders, and explains how abnormalities seen on MIR images relate to pathophysiology and clinical signs. Special attention is given to imaging of rotator

M. B. Zlatkin; J. P. Iannotti; M. D. Schnall

1991-01-01

332

Gd-hydroxypyridinone (HOPO)-based high-relaxivity magnetic resonance imaging (MRI) contrast agents.  

PubMed

Magnetic resonance imaging (MRI) is a particularly effective tool in medicine because of its high depth penetration (from 1 mm to 1 m) and ability to resolve different soft tissues. The MRI signal is generated by the relaxation of in vivo water molecule protons. MRI images can be improved by administering paramagnetic agents, which increase the relaxation rates of nearby water protons, thereby enhancing the MRI signal. The lanthanide cation Gd(3+) is generally used because of its favorable electronic properties; high toxicity, however, necessitates strongly coordinating ligands to keep Gd(3+) completely bound while in the patient. In this Account, we give a coordination chemistry overview of contrast agents (CAs) based on Gd-hydroxypyridinone (HOPO), which show improved MRI contrast and high thermodynamic stabilities. Tris-bidentate HOPO-based ligands developed in our laboratory were designed to complement the coordination preferences of Gd(3+), especially its oxophilicity. The HOPO ligands provide a hexadentate coordination environment for Gd(3+), in which all of the donor atoms are oxygen. Because Gd(3+) favors eight or nine coordination, this design provides two to three open sites for inner-sphere water molecules. These water molecules rapidly exchange with bulk solution, hence affecting the relaxation rates of bulk water molecules. The parameters affecting the efficiency of these contrast agents have been tuned to improve contrast while still maintaining a high thermodynamic stability for Gd(3+) binding. The Gd-HOPO-based contrast agents surpass current commercially available agents because of a higher number of inner-sphere water molecules, rapid exchange of inner-sphere water molecules via an associative mechanism, and a long electronic relaxation time. The contrast enhancement provided by these agents is at least twice that of commercial contrast agents, which are based on polyaminocarboxylate ligands. Advances in MRI technology have made significant contributions to the improvement of clinical diagnostics by allowing visualization of underlying pathology. However, understanding the mechanism of a disease at the molecular level requires improved imaging sensitivity. The ultimate goal is to visually distinguish between different disease targets or markers, such as enzymes, hormones, proteins, or small molecules, at biologically relevant concentrations (from micro- to nanomolar). Although MRI techniques can provide images of the organs and tissues in which these biomarkers are regulated, the high sensitivity required to visualize the biological targets within the tissues is currently lacking; contrast enhancements of 50-fold beyond current agents are required to achieve this goal. According to the theory of paramagnetic relaxation, the contrast enhancement can be further improved by slowing the tumbling rate of the MRI agent. Theoretically, this enhancement would be greater for contrast agents with an optimal rate of water exchange. The Gd-HOPO-based contrast agents have optimal water-exchange rates, whereas the commercial agents have slower non-optimal water-exchange rates; thus, the Gd-HOPO agents are ideal for attachment to macromolecules, which will slow down the tumbling rate and increase contrast. This strategy has been recently tested with the Gd-HOPO agents via covalent attachment to virus capsids, affording contrast enhancements 10-fold beyond commercial agents. PMID:19505089

Datta, Ankona; Raymond, Kenneth N

2009-07-21

333

The Basics of MRI  

NSDL National Science Digital Library

The Basics of MRI is a hypertextbook by Dr. Joseph Hornak of the Rochester Institute of Technology that focuses on the mathematics and physics of magnetic resonance imaging. "Exponential Functions," "Differentials and Integrals," and "Coordinate Transformation" are just a few of the mathematical topics discussed. The physics behind MRI is broken down into the following chapters: "Spin Physics," "NMR Spectroscopy," "Fourier Transforms," "Imaging Principles," and "Fourier Transform Imaging Principles." Hornak has also included a multitude of information on imaging techniques, presentation, and hardware. Those concerned with what occurs during a MRI exam, rather than the math and physics of MRI, will want to consult the chapter entitled "Your MRI Exam."

Hornak, Joseph P.

1996-01-01

334

Hornbills can distinguish between primate alarm calls.  

PubMed Central

Some mammals distinguish between and respond appropriately to the alarm calls of other mammal and bird species. However, the ability of birds to distinguish between mammal alarm calls has not been investigated. Diana monkeys (Cercopithecus diana) produce different alarm calls to two predators: crowned eagles (Stephanoaetus coronatus) and leopards (Panthera pardus). Yellow-casqued hornbills (Ceratogymna elata) are vulnerable to predation by crowned eagles but are not preyed on by leopards and might therefore be expected to respond to the Diana monkey eagle alarm call but not to the leopard alarm call. We compared responses of hornbills to playback of eagle shrieks, leopard growls, Diana monkey eagle alarm calls and Diana monkey leopard alarm calls and found that they distinguished appropriately between the two predator vocalizations as well as between the two Diana monkey alarm calls. We discuss possible mechanisms leading to these responses.

Rainey, Hugo J; Zuberbuhler, Klaus; Slater, Peter J B

2004-01-01

335

Nano-sized MRI contrast agents with dendrimer cores  

Microsoft Academic Search

Gadolinium-based MRI contrast agents (CAs) can be effective at a ?100-fold lower concentration of Gadolinium ions in comparison to the concentration of Iodine atoms required for CT imaging. Therefore, a number of dendrimer based macromolecular MRI CAs of various sizes and properties prepared employing relatively simple chemistry are readily available that can provide sufficient contrast enhancement for various applications. Molecules

Hisataka Kobayashi; Martin W. Brechbiel

2005-01-01

336

Computer-assisted analysis of peripheral zone prostate lesions using T2-weighted and dynamic contrast enhanced T1-weighted MRI  

Microsoft Academic Search

In this study, computer-assisted analysis of prostate lesions was researched by combining information from two different magnetic resonance (MR) modalities: T2-weighted (T2-w) and dynamic contrast-enhanced (DCE) T1-w images. Two issues arise when incorporating T2-w images in a computer-aided diagnosis (CADx) system: T2-w values are position as well as sequence dependent and images can be misaligned due to patient movement during

Pieter C Vos; Thomas Hambrock; Jelle O Barenstz; Henkjan J Huisman

2010-01-01

337

Sequential Change in Myocardial Perfusion in Ischemic Heart Disease Post Percutaneous Coronary Intervention: A longitudinal study using first-pass contrast-enhanced MRI  

Microsoft Academic Search

In this study, we performed first-pass contrast-enhanced (FPCE) myocardial perfusion in a serial follow-up to determine the timing, magnitude and transmural difference of myocardial perfusion recovery by evaluating the change in stress perfusion, rest perfusion, and myocardial perfusion reserve (MPR). All patients received baseline MR studies one day before PCI treatment and follow-up MR studies at one day, one week

W. C. Shen

338

On distinguishing radions from Higgs bosons  

Microsoft Academic Search

Radion couplings are almost identical in form to Higgs boson couplings, making it very difficult to distinguish the two states when the masses and branching ratios to Standard Model particles are similar. The only real difference lies in the fact that the coupling of radions to off-shell fermions is proportional to the momentum rather than the mass of the fermion.

Prasanta Kumar Das; Santosh Kumar Rai; Sreerup Raychaudhuri

2005-01-01

339

Distinguishing the potential operands in FORTRAN programs  

Microsoft Academic Search

There are several possible relationships between the number of potential operands and the actual operands used which correlate with available data (such as Akiyama's debugging data). However, additional data is required to distinguish between these hypotheses. Since there is a large body of programs available written in FORTRAN, we wish to develop a mechanical counting procedure to enumerate potential operands

George E. Estes

1982-01-01

340

Distinguishing Juvenile Homicide From Violent Juvenile Offending  

Microsoft Academic Search

Juvenile homicide is a social problem that has remained a central focus within juvenile justice research in recent years. The term juvenile murderer describes a legal category, but it is purported to have significant scientific meaning. Research has attempted to conceptualize adolescent murderers as a clinical category that can be reliably distinguished from their nonhomicidal counterparts. This study examined 33

Frank DiCataldo; Meghan Everett

2008-01-01

341

Distinguishing Disability: Parents, Privilege, and Special Education  

ERIC Educational Resources Information Center

|Students in special education programs can have widely divergent experiences. For some, special education amounts to a dumping ground where schools unload their problem students, while for others, it provides access to services and accommodations that drastically improve chances of succeeding in school and beyond. "Distinguishing Disability"…

Ong-Dean, Colin

2009-01-01

342

Distinguishing between transformational and servant leadership  

Microsoft Academic Search

Purpose – Although transformational and servant leadership has been in existence since the 1970s and theoretical assumptions about the differences began in the 1990s, this paper seeks to relate the first empirical investigation distinguishing between the two leaders, which was conducted recently by the first author. Design\\/methodology\\/approach – Through a review of the literature, the first author established 19 semantic

Jeanine Parolini; Kathleen Patterson; Bruce Winston

2009-01-01

343

Gamma Oscillations Distinguish True From False Memories  

Microsoft Academic Search

To test whether distinct patterns of electro- physiological activity prior to a response can distinguish true from false memories, we analyzed intracranial elec- troencephalographic recordings while 52 patients under- going treatment for epilepsy performed a verbal free- recall task. These analyses revealed that the same pattern of gamma-band (28-100 Hz) oscillatory activity that pre- dicts successful memory formation at item

Per B. Sederberg; Andreas Schulze-Bonhage; Joseph R. Madsen; Edward B. Bromfield; Brian Litt; Armin Brandt; Michael J. Kahana

2007-01-01

344

Autonomic Nervous System Activity Distinguishes among Emotions  

Microsoft Academic Search

Emotion-specific activity in the autonomic nervous system was generated by constructing facial prototypes of emotion muscle by muscle and by reliving past emotional experiences. The autonomic activity produced distinguished not only between positive and negative emotions, but also among negative emotions. This finding challenges emotion theories that have proposed autonomic activity to be undifferentiated or that have failed to address

Paul Ekman; Robert W. Levenson; Wallace V. Friesen

1983-01-01

345

On distinguishing prime numbers from composite numbers  

Microsoft Academic Search

A new algorithm for testing primality is presented. The algorithm is distinguishable from the lovely algorithms of Solvay and Strassen [36], Miller [27] and Rabin [32] in that its assertions of primality are certain (i.e., provable from Peano's axioms) rather than dependent on unproven hypothesis (Miller) or probability (Solovay-Strassen, Rabin). An argument is presented which suggests that the algorithm runs

Leonard M. Adleman

1980-01-01

346

"Dropped-head" syndrome due to isolated myositis of neck extensor muscles: MRI findings.  

PubMed

MRI findings of a patient with dropped-head syndrome due to focal myositis of the neck extensor muscles are presented. MRI showed oedematous changes and marked enhancement of the neck extensor muscles. After therapy MRI demonstrated disappearance of the abnormal findings. PMID:16220272

Gaeta, Michele; Mazziotti, Silvio; Toscano, Antonio; Rodolico, Carmelo; Mazzeo, Anna; Blandino, Alfredo

2005-10-12

347

“Dropped-head” syndrome due to isolated myositis of neck extensor muscles: MRI findings  

Microsoft Academic Search

MRI findings of a patient with dropped-head syndrome due to focal myositis of the neck extensor muscles are presented. MRI\\u000a showed oedematous changes and marked enhancement of the neck extensor muscles. After therapy MRI demonstrated disappearance\\u000a of the abnormal findings.

Michele Gaeta; Silvio Mazziotti; Antonio Toscano; Carmelo Rodolico; Anna Mazzeo; Alfredo Blandino

2006-01-01

348

MRI as a tool for the study of waterflooding processes in heterogeneous cores.  

PubMed

NMR imaging has shown itself to be an important tool for improving analysis of flow behaviour during waterflooding in heterogeneous cores. Waterflooding is a widely employed technique in enhancing oil and gas recovery. However the success of such a process could be considerably reduced by instability of the displacing front with negative effects on production efficiency. MRI can be easily applied in evaluating the flow advancement because of its ability to distinguish different phases during dynamic experiments. In our study we have evaluated the shape of the displacing front during water injection in highly heterogeneous reservoir carbonates. The effect of petrographical heterogeneities which strongly characterize the rocks, revealed a marked influence on flow behaviour. Viscosity increase by polymer addition, in spite of a more favourable mobility ratio, resulted in a poorer performance because of higher channelling effects. The results of selected simulation experiments are discussed. PMID:8970109

Maddinelli, G; Brancolini, A

1996-01-01

349

MRI of retinoblastoma  

PubMed Central

We review the role of MRI in retinoblastoma and simulating lesions. Retinoblastoma is the most common paediatric intra-ocular tumour. It may be endophytic, exophytic or a diffuse infiltrating tumour. MRI can detect intra-ocular, extra-ocular and intracranial extension of the tumour. MRI is essential for monitoring patients after treatment and detection of associated second malignancies. It helps to differentiating the tumour from simulating lesions with leukocoria.

Razek, A A K A; Elkhamary, S

2011-01-01

350

MRI of Stroke Recovery  

PubMed Central

MRI is a vital tool for the measurement of acute stroke and has been used to visualize changes in activation patterns during stroke recovery. There is emerging interest on using MRI to monitor the structural substrates of spontaneous recovery and neurorestorative treatment of stroke. In this review, we describe the use of MRI and its associated challenges to measure vascular and neuronal remodeling in response to spontaneous and therapy-induced stroke recovery. We demonstrate that MRI methodologies may be used in real-time monitoring of recovery from stroke.

Jiang, Quan; Zhang, Zheng Gang; Chopp, Michael

2010-01-01

351

SENSE: Sensitivity encoding for fast MRI  

Microsoft Academic Search

New theoretical and practical concepts are presented for consid- erably enhancing the performance of magnetic resonance imag- ing (MRI) by means of arrays of multiple receiver coils. Sensitiv- ity encoding (SENSE) is based on the fact that receiver sensitivity generally has an encoding effect complementary to Fourier preparation by linear field gradients. Thus, by using multiple receiver coils in parallel

Klaas P. Pruessmann; Markus Weiger; Markus B. Scheidegger; Peter Boesiger

1999-01-01

352

Elemental imaging of MRI contrast agents: benchmarking of LA-ICP-MS to MRI.  

PubMed

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been used to map the spatial distribution of magnetic resonance imaging (MRI) contrast agents (Gd-based) in histological sections in order to explore synergies with in vivo MRI. Images from respective techniques are presented for two separate studies namely (1) convection enhanced delivery of a Gd nanocomplex (developmental therapeutic) into rat brain and (2) convection enhanced delivery, with co-infusion of Magnevist (commercial Gd contrast agent) and Carboplatin (chemotherapy drug), into pig brain. The LA technique was shown to be a powerful compliment to MRI not only in offering improved sensitivity, spatial resolution and signal quantitation but also in giving added value regarding the fate of administered agents (Gd and Pt agents). Furthermore simultaneous measurement of Fe enabled assignment of an anomalous contrast enhancement region in rat brain to haemorrhage at the infusion site. PMID:22526651

Pugh, J A T; Cox, A G; McLeod, C W; Bunch, J; Writer, M J; Hart, S L; Bienemann, A; White, E; Bell, J

2012-04-18

353

MRI findings in a dog with kernicterus.  

PubMed

A severe increase in total bilirubin coincided with a decline in neurologic status to comatose in a 9 yr old spayed female mixed-breed dog being treated for immune-mediated hemolytic anemia. MRI of the brain was performed to investigate potential causes for the neurologic signs. MRI revealed bilaterally symmetrical hyperintensities within the caudate nuclei, globus pallidus, thalamus, deep cerebellar nuclei, and cortical gray matter on T2-weighted and fluid-attenuated inversion recovery (FLAIR) sequences, which coincided with areas of bilirubin deposition and neuronal necrosis (kernicterus) identified on necropsy examination. This is the second case report of an adult dog exhibiting kernicterus, and the first report to document MRI findings associated with that condition. Kernicterus is an uncommonly reported complication of hyperbilirubinemia in dogs, but is potentially underreported due to difficulties in recognizing subtle lesions and distinguishing kernicterus from other potential causes of neurologic abnormalities with readily available antemortem tests. MRI may be helpful in supporting the diagnosis of kernicterus. PMID:23690488

Belz, Katie M; Specht, Andrew J; Johnson, Victoria S; Conway, Julia A

2013-05-20

354

Cerebral Blood Volume Analysis in Glioblastomas Using Dynamic Susceptibility Contrast-Enhanced Perfusion MRI: A Comparison of Manual and Semiautomatic Segmentation Methods  

PubMed Central

Purpose To compare the reproducibilities of manual and semiautomatic segmentation method for the measurement of normalized cerebral blood volume (nCBV) using dynamic susceptibility contrast-enhanced (DSC) perfusion MR imaging in glioblastomas. Materials and Methods Twenty-two patients (11 male, 11 female; 27 tumors) with histologically confirmed glioblastoma (WHO grade IV) were examined with conventional MR imaging and DSC imaging at 3T before surgery or biopsy. Then nCBV (means and standard deviations) in each mass was measured using two DSC MR perfusion analysis methods including manual and semiautomatic segmentation method, in which contrast-enhanced (CE)-T1WI and T2WI were used as structural imaging. Intraobserver and interobserver reproducibility were assessed according to each perfusion analysis method or each structural imaging. Interclass correlation coefficient (ICC), Bland-Altman plot, and coefficient of variation (CV) were used to evaluate reproducibility. Results Intraobserver reproducibilities on CE-T1WI and T2WI were ICC of 0.74–0.89 and CV of 20.39–36.83% in manual segmentation method, and ICC of 0.95–0.99 and CV of 8.53–16.19% in semiautomatic segmentation method, repectively. Interobserver reproducibilites on CE-T1WI and T2WI were ICC of 0.86–0.94 and CV of 19.67–35.15% in manual segmentation method, and ICC of 0.74–1.0 and CV of 5.48–49.38% in semiautomatic segmentation method, respectively. Bland-Altman plots showed a good correlation with ICC or CV in each method. The semiautomatic segmentation method showed higher intraobserver and interobserver reproducibilities at CE-T1WI-based study than other methods. Conclusion The best reproducibility was found using the semiautomatic segmentation method based on CE-T1WI for structural imaging in the measurement of the nCBV of glioblastomas.

Jung, Seung Chai; Choi, Seung Hong; Yeom, Jeong A.; Kim, Ji-Hoon; Ryoo, Inseon; Kim, Soo Chin; Shin, Hwaseon; Lee, A. Leum; Yun, Tae Jin; Park, Chul-Kee; Sohn, Chul-Ho; Park, Sung-Hye

2013-01-01

355

Gamma oscillations distinguish true from false memories.  

PubMed

To test whether distinct patterns of electrophysiological activity prior to a response can distinguish true from false memories, we analyzed intracranial electroencephalographic recordings while 52 patients undergoing treatment for epilepsy performed a verbal free-recall task. These analyses revealed that the same pattern of gamma-band (28-100 Hz) oscillatory activity that predicts successful memory formation at item encoding--increased gamma power in the hippocampus, prefrontal cortex, and left temporal lobe--reemerges at retrieval to distinguish correct from incorrect responses. The timing of these oscillatory effects suggests that self-cued memory retrieval begins in the hippocampus and then spreads to the cortex. Thus, retrieval of true, as compared with false, memories induces a distinct pattern of gamma oscillations, possibly reflecting recollection of contextual information associated with past experience. PMID:17958703

Sederberg, Per B; Schulze-Bonhage, Andreas; Madsen, Joseph R; Bromfield, Edward B; Litt, Brian; Brandt, Armin; Kahana, Michael J

2007-11-01

356

Distinguishing Regulatory DNA From Neutral Sites  

PubMed Central

We explore several computational approaches to analyzing interspecies genomic sequence alignments, aiming to distinguish regulatory regions from neutrally evolving DNA. Human–mouse genomic alignments were collected for three sets of human regions: (1) experimentally defined gene regulatory regions, (2) well-characterized exons (coding sequences, as a positive control), and (3) interspersed repeats thought to have inserted before the human–mouse split (a good model for neutrally evolving DNA). Models that potentially could distinguish functional noncoding sequences from neutral DNA were evaluated on these three data sets, as well as bulk genome alignments. Our analyses show that discrimination based on frequencies of individual nucleotide pairs or gaps (i.e., of possible alignment columns) is only partially successful. In contrast, scoring procedures that include the alignment context, based on frequencies of short runs of alignment columns, dramatically improve separation between regulatory and neutral features. Such scoring functions should aid in the identification of putative regulatory regions throughout the human genome.

Elnitski, Laura; Hardison, Ross C.; Li, Jia; Yang, Shan; Kolbe, Diana; Eswara, Pallavi; O'Connor, Michael J.; Schwartz, Scott; Miller, Webb; Chiaromonte, Francesca

2003-01-01

357

Recent advances in flow MRI.  

PubMed

The past five years have seen exciting new developments in Flow MRI. Two-dimensional images are now routinely acquired in 100-200 ms and, in some cases, acquisition times of 5-10 ms are possible. This has been achieved not only by advances in the implementation of existing pulse sequences but also in data acquisition strategies, such as Compressed Sensing and Bayesian approaches, and technical advices in parallel imaging and signal enhancement methods. In particular, the short imaging timescales that are now achieved offer significant opportunities in the study of transient flow phenomena. PMID:23260397

Gladden, Lynn F; Sederman, Andrew J

2012-11-29

358

Comparing quantum Markovianities: Distinguishability versus correlations  

NASA Astrophysics Data System (ADS)

We compare several criteria for quantum Markovianities and illustrate the differences and similarities through explicit examples of random unitary qubit dynamics (Pauli channels). In particular, we demonstrate that the quantum Markovianity based on distinguishability [Breuer , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.103.210401 103, 210401 (2009)] is not equivalent to that based on correlations [Luo , Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.86.044101 86, 044101 (2012)].

Jiang, Min; Luo, Shunlong

2013-09-01

359

Distinguishing Regulatory DNA From Neutral Sites  

Microsoft Academic Search

We explore several computational approaches to analyzing interspecies genomic sequence alignments, aiming to distinguish regulatory regions from neutrally evolving DNA. Human-mouse genomic alignments were collected for three sets of human regions: (1) experimentally defined gene regulatory regions, (2) well-characterized exons (coding sequences, as a positive control), and (3) interspersed repeats thought to have inserted before the human-mouse split (a good

Laura Elnitski; Ross C. Hardison; Jia Li; Shan Yang; Diana Kolbe; Pallavi Eswara; Michael J. O'Connor; Scott Schwartz; Webb Miller; Francesca Chiaromonte

2003-01-01

360

Familial Identification: Population Structure and Relationship Distinguishability  

PubMed Central

With the expansion of offender/arrestee DNA profile databases, genetic forensic identification has become commonplace in the United States criminal justice system. Implementation of familial searching has been proposed to extend forensic identification to family members of individuals with profiles in offender/arrestee DNA databases. In familial searching, a partial genetic profile match between a database entrant and a crime scene sample is used to implicate genetic relatives of the database entrant as potential sources of the crime scene sample. In addition to concerns regarding civil liberties, familial searching poses unanswered statistical questions. In this study, we define confidence intervals on estimated likelihood ratios for familial identification. Using these confidence intervals, we consider familial searching in a structured population. We show that relatives and unrelated individuals from population samples with lower gene diversity over the loci considered are less distinguishable. We also consider cases where the most appropriate population sample for individuals considered is unknown. We find that as a less appropriate population sample, and thus allele frequency distribution, is assumed, relatives and unrelated individuals become more difficult to distinguish. In addition, we show that relationship distinguishability increases with the number of markers considered, but decreases for more distant genetic familial relationships. All of these results indicate that caution is warranted in the application of familial searching in structured populations, such as in the United States.

Rohlfs, Rori V.; Fullerton, Stephanie Malia; Weir, Bruce S.

2012-01-01

361

Hybrid-SPRITE MRI.  

PubMed

In a FID based frequency encoding MRI experiment the central part of k-space is not generally accessible due to the probe dead time. This portion of k-space is however crucial for image reconstruction. SPRITE (Single Point Ramped Imaging with T1 Enhancement), SPI with a linearly ramped phase encode gradient, has been employed to image short relaxation time systems for many years with great success. It is a robust imaging method in significant measure because it provides acquisition of high quality k-space origin data. We propose a new sampling scheme, termed hybrid-SPRITE, combining phase and frequency encoding to ensure high quality images with reduced acquisition times, reduced gradient duty cycle and increased sensitivity. In hybrid-SPRITE, numerous time domain points are collected to assist image reconstruction. An Inverse Non-uniform Discrete Fourier Transform (INDFT) is employed in 1D applications. A pseudo-polar grid is exploited in 2D hybrid-SPRITE for rapid and accurate image reconstruction. PMID:23916990

Xiao, Dan; Balcom, Bruce J

2013-07-18

362

Hybrid-SPRITE MRI  

NASA Astrophysics Data System (ADS)

In a FID based frequency encoding MRI experiment the central part of k-space is not generally accessible due to the probe dead time. This portion of k-space is however crucial for image reconstruction. SPRITE (Single Point Ramped Imaging with T1 Enhancement), SPI with a linearly ramped phase encode gradient, has been employed to image short relaxation time systems for many years with great success. It is a robust imaging method in significant measure because it provides acquisition of high quality k-space origin data. We propose a new sampling scheme, termed hybrid-SPRITE, combining phase and frequency encoding to ensure high quality images with reduced acquisition times, reduced gradient duty cycle and increased sensitivity. In hybrid-SPRITE, numerous time domain points are collected to assist image reconstruction. An Inverse Non-uniform Discrete Fourier Transform (INDFT) is employed in 1D applications. A pseudo-polar grid is exploited in 2D hybrid-SPRITE for rapid and accurate image reconstruction.

Xiao, Dan; Balcom, Bruce J.

2013-10-01

363

Ex vivo MRI evaluation of breast tumors: a novel tool for verifying resection of nonpalpable only MRI detected lesions.  

PubMed

A fundamental question in surgery of only magnetic resonance imaging (MRI)-detected breast lesions is to ensure their removal when they are not palpable by clinical examination and surgical exploration. This is especially relevant in the case of small tumors, carcinoma in situ or lobular carcinoma. Thirty-nine patients were enrolled in the study, 21 patients with breast lesions detected by both conventional imaging and breast MRI (bMRI) and 18 patients with bMRI findings only. Preoperative bMRI allowed staging the disease and localizing the lesion. In the operating theater, contrast medium was injected 1 minute before skin incision. After removal, surgical specimens were submitted to ex vivo MRI, performed using a dedicated surface coil and Spair inversion recovery sequences for suppression of fat signal intensity. All MRI enhancing lesions were completely included within the surgical specimen and visualized by ex vivo MRI. In the first 21 patients, bMRI was able to visualize branching margins or satellite nodules around the core lesion, and allowed for better staging of the surrounding in situ carcinoma; in the last 18 patients, eight of whom were breast cancer type 1 susceptibility protein (BRCA) mutation carriers, bMRI identified 12 malignant tumors, otherwise undetectable, that were all visualized by ex vivo MRI. This is the first description of a procedure that re-enhances breast lesions within a surgical specimen, demonstrating the surgical removal of nonpalpable breast lesions diagnosed only with bMRI. This new strategy reproduces the morphology and the entire extension of the primary lesion on the specimen, with potentially better local surgical control, reducing additional unplanned surgery. PMID:24102850

Agresti, Roberto; Trecate, Giovanna; Ferraris, Cristina; Valeri, Barbara; Maugeri, Ilaria; Pellitteri, Cristina; Martelli, Gabriele; Migliavacca, Silvana; Carcangiu, Maria Luisa; Bohm, Silvia; Maffioli, Lorenzo; Vergnaghi, Daniele; Panizza, Pietro

2013-09-19

364

Preparation and in vitro evaluation of folate-receptor-targeted SPION-polymer micelle hybrids for MRI contrast enhancement in cancer imaging.  

PubMed

Polymer-SPION hybrids were investigated for receptor-mediated localization in tumour tissue. Superparamagnetic iron oxide nanoparticles (SPIONs) prepared by high-temperature decomposition of iron acetylacetonate were monodisperse (9.27 ± 3.37 nm), with high saturation magnetization of 76.8 emu g(-1). Amphiphilic copolymers prepared from methyl methacrylate and PEG methacrylate by atom transfer radical polymerization were conjugated with folic acid (for folate-receptor specificity). The folate-conjugated polymer had a low critical micellar concentration (0.4 mg l(-1)), indicating stability of the micellar formulation. SPION-polymeric micelle clusters were prepared by desolvation of the SPION dispersion/polymer solution in water. Magnetic resonance imaging of the formulation revealed very good contrast enhancement, with transverse (T(2)) relaxivity of 260.4 mM(-1) s(-1). The biological evaluation of the SPION micelles included cellular viability assay (MTT) and uptake in HeLa cells. These studies demonstrated the potential use of these nanoplatforms for imaging and targeting. PMID:23221062

Mahajan, Shveta; Koul, Veena; Choudhary, Veena; Shishodia, Gauri; Bharti, Alok C

2012-12-07

365

MRI of Listeria rhombencephalitis  

Microsoft Academic Search

A case of Listeria rhombencephalitis in a patient, who was evaluated by MRI, is reported. MRI showed areas of high signal intensity on T2-weighted images in the rhombencephalon and confirmed the clinical diagnosis of a brainstem affection by Listeria monocytogenes.

M. Just; G. Krämer; H. P. Higer; F. Thömke; P. Pfannenstiel

1987-01-01

366

Default-mode network activity distinguishes Alzheimer's disease from healthy aging: Evidence from functional MRI  

Microsoft Academic Search

Recent functional imaging studies have revealed coactivation in a distributed network of cortical regions that characterizes the resting state, or default mode, of the human brain. Among the brain regions implicated in this network, several, including the posterior cingulate cortex and inferior parietal lobes, have also shown decreased metabolism early in the course of Alzhei- mer's disease (AD). We reasoned

Michael D. Greicius; Gaurav Srivastava; Allan L. Reiss; Vinod Menon

2004-01-01

367

Computer-assisted analysis of peripheral zone prostate lesions using T2-weighted and dynamic contrast enhanced T1-weighted MRI.  

PubMed

In this study, computer-assisted analysis of prostate lesions was researched by combining information from two different magnetic resonance (MR) modalities: T2-weighted (T2-w) and dynamic contrast-enhanced (DCE) T1-w images. Two issues arise when incorporating T2-w images in a computer-aided diagnosis (CADx) system: T2-w values are position as well as sequence dependent and images can be misaligned due to patient movement during the acquisition. A method was developed that computes T2 estimates from a T2-w and proton density value and a known sequence model. A mutual information registration strategy was implemented to correct for patient movement. Global motion is modelled by an affine transformation, while local motion is described by a volume preserving non-rigid deformation based on B-splines. The additional value to the discriminating performance of a DCE T1-w-based CADx system was evaluated using bootstrapped ROC analysis. T2 estimates were successfully computed in 29 patients. T2 values were extracted and added to the CADx system from 39 malignant, 19 benign and 29 normal annotated regions. T2 values alone achieved a diagnostic accuracy of 0.85 (0.77-0.92) and showed a significantly improved discriminating performance of 0.89 (0.81-0.95), when combined with DCE T1-w features. In conclusion, the study demonstrated a simple T2 estimation method that has a diagnostic performance such that it complements a DCE T1-w-based CADx system in discriminating malignant lesions from normal and benign regions. Additionally, the T2 estimate is beneficial to visual inspection due to the removed coil profile and fixed window and level settings. PMID:20197602

Vos, Pieter C; Hambrock, Thomas; Barenstz, Jelle O; Huisman, Henkjan J

2010-03-02

368

Quantification of left ventricular size and function using contrast-enhanced real-time 3D imaging with power modulation: comparison with cardiac MRI.  

PubMed

In patients with optimal images, real-time 3-D echocardiography (RT3DE) allows accurate evaluation of left ventricular (LV) volumes and ejection fraction (EF). However, in patients with poor acoustic windows, lower correlations were reported despite the use of contrast. We hypothesized that power modulation (PM) RT3DE imaging that uses low mechanical indices and provides uniform LV opacification could overcome this problem. Accordingly, we sought to: (i) Test the feasibility of quantification of LV volumes and EF from contrast-enhanced (CE) PM RT3DE images, (ii) validate this technique against cardiac magnetic resonance (CMR) reference and (iii) test its clinical value by quantifying the improvement in accuracy and reproducibility. We studied 20 patients who underwent CMR, harmonic nonenhanced RT3DE and CE PM RT3DE imaging on the same day. All images were analyzed to obtain end-systolic and end-diastolic LV volumes (EDV, ESV) and calculate EF. To determine the reproducibility of each RT3DE technique, imaging was repeated in the same setting by a second sonographer. In addition, patients were divided according to the quality of their RT3DE images into two groups, for which agreement with CMR and reproducibility were calculated separately. CE PM RT3DE imaging improved the accuracy of EDV, ESV and EF measurements in patients with poor acoustic windows without significantly affecting those in patients with optimal images. In addition, CE PM RT3DE imaging improved the reproducibility of the measurements, as reflected by a twofold decrease in intermeasurement variability. Importantly, the variability in CE PM RT3DE-derived volumes and EF was under 10%, irrespective of image quality. This methodology may become the new standard for LV size and function, which will be particularly important in patients with poor acoustic windows or contraindications to CMR. PMID:22906750

Coon, Patrick D; Pollard, Heidi; Furlong, Kathleen; Lang, Roberto M; Mor-Avi, Victor

2012-08-17

369

MRI at 132 ?T for the Detection of Tumors  

NASA Astrophysics Data System (ADS)

We are investigating the use of magnetic resonance imaging (MRI), typically at 132 ?T, with enhanced longitudinal-relaxation-time (T1)-weighted contrast to detect tumors. We have measured T1 of healthy and cancerous prostate tissue specimens--within a few hours of their surgical removal--from approximately 20 patients. The measurements involve a field-cycling imaging technique in which we prepolarize protons in fields up to 150 mT. After this field has been ramped down, the image of each pair of samples is encoded using magnetic field gradients, and the proton nuclear magnetic resonance signal is measured using a SQUID coupled to an untuned, second-derivative gradiometer. The observed T1 contrast is significantly greater than that at (say) 1.5 T, suggesting that one may be able to distinguish tumors from healthy tissue without a contrast agent: average T1 values at 132 ?T for healthy and cancerous prostate tissue are 60 and 46 ms. We describe a 150-mT prepolarizing coil that will allow the system to be reconfigured in a geometry suitable for in vivo imaging of human prostates.

Busch, Sarah; Mößle, Michael; Hatridge, Michael; Lee, In Hwan; Chew, Kevin; Simko, Jeff; Pines, Alex; Clarke, John

2010-03-01

370

Distinguishing benign from malignant liver tumours  

PubMed Central

Abstract Liver masses are very common and most are benign. It is therefore important to avoid unnecessary interventions for benign lesions, while at the same time ensuring accurate diagnosis of hepatic malignancies. Many cancer patients, like the general population, have incidental benign liver lesions. In planning treatment for cancer patients, it is critical to avoid inappropriate treatment decisions based on misdiagnosis of a benign lesion as a metastasis or primary liver malignancy. This article describes the salient imaging features of the common benign liver masses and outlines a general approach to distinguishing between benign and malignant hepatic lesions.

2007-01-01

371

Terahertz surface plasmon sensor for distinguishing gasolines.  

PubMed

Gasolines of two different octane numbers are experimentally distinguished using a thin metal sheet perforated with a periodic hole array terahertz surface plasmon (SP) sensor. This sensor is proved to be very sensitive to the change in permittivities of analytes. The differences between the gasolines 93# and 97# in composition lead to various refractive indices, permittivities, and absorption coefficients, thus varying their interactions with surface waves on the sensor, which enables a distinction of 6 GHz between the two octane numbers in the transmission peaks. The freestanding SP sensor is effective and reliable and can be simply employed in analyte distinction, which has potential applications in the petroleum industry. PMID:23938420

Liu, Guanlin; He, Mingxia; Tian, Zhen; Li, Jingyan; Liu, Jiazheng

2013-08-10

372

Can cosmic parallax distinguish between anisotropic cosmologies?  

NASA Astrophysics Data System (ADS)

In an anisotropic universe, observers not positioned at a point of special symmetry should observe cosmic parallax—the relative angular motion of test galaxies over cosmic time. It was recently argued that the nonobservance of this effect in upcoming precision astrometry missions such as GAIA may be used to place strong bounds on the position of off-center observers in a void-model universe described by the Lemaitre-Tolman-Bondi metric. We consider the analogous effect in anisotropic cosmological models described by an axisymmetric homogeneous Bianchi type I metric and discuss whether any observation of cosmic parallax would distinguish between different anisotropic evolutions.

Fontanini, Michele; West, Eric J.; Trodden, Mark

2009-12-01

373

Metallofullerenes: a new class of MRI agents and more?  

PubMed

Metallofullerenes have incited research endeavors across many disciplines owing to their wide range of properties obtainable by altering the metal component inside the fullerene cage or by a variety of surface functionalities. With a metal component of gadolinium, gadofullerenes have particularly shown promise in MRI applications owing to their high proton relaxivity and isolation of the metal from the biological environment. This article aims to give a perspective on the development of metallofullerenes as MRI contrast agents and further applications that distinguish them as a new class of imaging agent. PMID:24156489

Fatouros, Panos P; Shultz, Michael D

2013-11-01

374

Myocardial viability assessment in patients with highly impaired left ventricular function: comparison of delayed enhancement, dobutamine stress MRI, end-diastolic wall thickness, and TI 201 SPECT with functional recovery after revascularization  

Microsoft Academic Search

This study compared different magnetic resonance imaging (MRI) methods with Tl201 single photon emission computerized tomography (SPECT) and the “gold standard” for viability assessment, functional recovery after coronary artery bypass grafting (CABG). Twenty patients (64±7.3 years) with severely impaired left ventricular function (ejection fraction [EF] 28.6±8.7%) underwent MRI and SPECT before and 6 months after CABG. Wall-motion abnormalities were assessed

M. Gutberlet; M. Fröhlich; S. Mehl; H. Amthauer; H. Hausmann; R. Meyer; H. Siniawski; J. Ruf; M. Plotkin; T. Denecke; B. Schnackenburg; R. Hetzer; R. Felix

2005-01-01

375

Unusual MRI findings in an immunocompetent patient with EBV encephalitis: a case report  

PubMed Central

Blackground It is well-known that Epstein-Barr virus (EBV) can affect the central nervous system (CNS). Case presentation Herein the authors report unusual timely Magnetic Resonance Imaging (MRI) brain scan findings in an immunocompetent patient with EBV encephalitis. Diffusion weighted MRI sequence performed during the acute phase of the disease was normal, whereas the Fast Relaxation Fast Spin Echo T2 image showed diffuse signal intensity changes in white matter. The enhancement pattern suggested an inflammatory response restricted to the brain microcirculation. Acyclovir and corticosteroid therapy was administered. After three weeks, all signal intensities returned to normal and the patient showed clinical recovery. Conclusion This report demonstrates that EBV in an immunocompetent adult can present with diffuse, reversible brain white matter involvement in the acute phase of mononucleosis. Moreover, our case suggests that a negative DWI sequence is associated with a favorable improvement in severe EBV CNS infection. More extensive studies are needed to assess what other instrumental data can help to distinguish viral lesions from other causes in the acute phase of disease.

2011-01-01

376

Cardiac magnetic resonance in a patient with MRI-conditional pacemaker.  

PubMed

An implanted pacemaker is generally considered a contraindication for magnetic resonance imaging (MRI). The increasing number of indications for MRI and the rising prevalence of implanted cardiac pacemakers have prompted the recent development of MRI-conditional pacemaker systems. We present the case of a 68-year-old woman with left ventricular hypertrophy, hypertension, aortic valve stenosis and a family history of cardiac amyloidosis, who developed complete heart block. In view of the foreseeable need for cardiac MRI, an MRI-conditional dual chamber pacemaker was implanted. The MRI scan confirmed moderate left ventricular hypertrophy and aortic valve stenosis, and showed no delayed enhancement suggestive of amyloid heart disease. This case illustrates the feasibility of cardiac MRI in this setting and the usefulness of the recently introduced MRI-conditional pacemaker systems. PMID:23333214

Ferreira, António Miguel; Mendes, Lígia; Soares, Luís; da Graça Correia, Maria; Gil, Victor

2013-01-17

377

The Basics of MRI  

NSDL National Science Digital Library

This textbook contains a comprehensive tour of magnetic resonance imaging (MRI) including the underlying mathematics and physics, image processing, and also job opportunities. This textbook also includes homework problems with solutions.

Hornak, Joseph P.

2010-03-16

378

Magnetic Resonance Imaging (MRI).  

National Technical Information Service (NTIS)

Magnetic resonance imaging (MRI) is a method of graphically representing the distribution of water and other hydrogen-rich molecules in the human body. Imaging parameters are complex. Although MR images may demonstrate anatomy as do conventional radiograp...

E. Feigenbaum

1985-01-01

379

Inequality indicators and distinguishability in economics  

NASA Astrophysics Data System (ADS)

Money has a material counterpart, such as banknotes or coins, and an ideal expression, monetary units. In the latter case, it is boson-like: individual incomes have no a priori limit, and their units are not distinguishable from each other in economic processes. Individuals, on the other hand, usually occupy one job at a time which makes them akin to fermions. We apply to individual incomes down-to-earth statistical calculations, similar to those for quantum particles, and obtain expressions for the cumulative distribution function, probability density and Lorenz function resulting from the simultaneous use of both statistics. They provide extremely good fits to corresponding data on French income distributions. On this basis, we propose a new entropic inequality indicator.

Rosenblatt, J.; Martinás, K.

2008-03-01

380

University of Massachusetts: Distinguished Visitors Program  

NSDL National Science Digital Library

The University of Massachusetts at Amherst Library has an elaborate mix of digital collections available through their UMarmot program, which is the online presence of their Special Collections & University Archives division. One of the more recent digitization projects they have completed is the Distinguished Visitors Program. The Program contains talks from a wide range of visitors who came to Amherst in the 1970s. The talks here include lively conversations with Isaac Asimov, Julian Bond, Angela Davis, David Halberstam, Tom Hayden, and Jane Fonda. Visitors will also find a short description of each individual's talk, along with information about what brought him or her to campus. The talks are engaging; one of the best is the talk by David Halberstam, which features a discussion of American politics and foreign policy in the wake of Watergate.

2012-04-06