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Sample records for portal imager dosimetry

  1. Portal dosimetry for VMAT using integrated images obtained during treatment

    SciTech Connect

    Bedford, James L. Hanson, Ian M.; Hansen, Vibeke Nordmark

    2014-02-15

    Purpose: Portal dosimetry provides an accurate and convenient means of verifying dose delivered to the patient. A simple method for carrying out portal dosimetry for volumetric modulated arc therapy (VMAT) is described, together with phantom measurements demonstrating the validity of the approach. Methods: Portal images were predicted by projecting dose in the isocentric plane through to the portal image plane, with exponential attenuation and convolution with a double-Gaussian scatter function. Appropriate parameters for the projection were selected by fitting the calculation model to portal images measured on an iViewGT portal imager (Elekta AB, Stockholm, Sweden) for a variety of phantom thicknesses and field sizes. This model was then used to predict the portal image resulting from each control point of a VMAT arc. Finally, all these control point images were summed to predict the overall integrated portal image for the whole arc. The calculated and measured integrated portal images were compared for three lung and three esophagus plans delivered to a thorax phantom, and three prostate plans delivered to a homogeneous phantom, using a gamma index for 3% and 3 mm. A 0.6 cm{sup 3} ionization chamber was used to verify the planned isocentric dose. The sensitivity of this method to errors in monitor units, field shaping, gantry angle, and phantom position was also evaluated by means of computer simulations. Results: The calculation model for portal dose prediction was able to accurately compute the portal images due to simple square fields delivered to solid water phantoms. The integrated images of VMAT treatments delivered to phantoms were also correctly predicted by the method. The proportion of the images with a gamma index of less than unity was 93.7% ± 3.0% (1SD) and the difference between isocenter dose calculated by the planning system and measured by the ionization chamber was 0.8% ± 1.0%. The method was highly sensitive to errors in monitor units and

  2. A new approach in the design of electronic portal imaging devices for portal dosimetry in radiotherapy.

    PubMed

    Badel, J N; Partouche-Sebban, D; Abraham, I; Carrie, C

    2014-09-01

    A CCD-based EPID using new crystal-assembly X-ray (CAX) converters is investigated for radiotherapy dosimetry. The proposed EPID design consists in replacing the common phosphor X-ray converters of current CCD-based EPIDs with high-stopping-power CAX converters. A Test Imaging Device (TID), consisting of a 30-mm-thick CAX converter made of Bismuth Germanate (BGO), coupled to a highly sensitive CCD camera, was used to evaluate the accessible imaging and dosimetric performance of the proposed design. The system response to dose and its dependence on photon beam energy were investigated. The effects of ghosting, dose rate, field size and phantom thickness were evaluated as well. The same measurements were also performed with our clinically used aSi-EPID so that comparisons of performance could be directly inferred. The TID displayed no detectable ghosting or sensitivity to dose rate. Its response to MU exposure was found to be linear within about ±1%. The level of glare induced in the TID and the aSi-EPID were equivalent. The TID resolution was higher than that of the aSi-EPID on the axis, but was found to decrease with off-axis distance. Finally, the image quality, assessed on the basis of signal-to-noise ratio in low dose radiographs of the larynx of a patient, was higher for the TID. The imaging performance accessible with the TID proved to be satisfying and its dosimetric capability was found to be superior to that of the current aSi-EPID.

  3. Transit Dosimetry for Patient Treatment Verification with an Electronic Portal Imaging Device

    NASA Astrophysics Data System (ADS)

    Berry, Sean L.

    The complex and individualized photon fluence patterns constructed during intensity modulated radiation therapy (IMRT) treatment planning must be verified before they are delivered to the patient. There is a compelling argument for additional verification throughout the course of treatment due to the possibility of data corruption, unintentional modification of the plan parameters, changes in patient anatomy, errors in patient alignment, and even mistakes in identifying the correct patient for treatment. Amorphous silicon (aSi) Electronic Portal Imaging Devices (EPIDs) can be utilized for IMRT verification. The goal of this thesis is to implement EPID transit dosimetry, measurement of the dose at a plane behind the patient during their treatment, within the clinical process. In order to achieve this goal, a number of the EPID's dosimetric shortcomings were studied and subsequently resolved. Portal dose images (PDIs) acquired with an aSi EPID suffer from artifacts related to radiation backscattered asymmetrically from the EPID support structure. This backscatter signal varies as a function of field size (FS) and location on the EPID. Its presence can affect pixel values in the measured PDI by up to 3.6%. Two methods to correct for this artifact are offered: discrete FS specific correction matrices and a single generalized equation. The dosimetric comparison between the measured and predicted through-air dose images for 49 IMRT treatment fields was significantly improved (p << .001) after the application of these FS specific backscatter corrections. The formulation of a transit dosimetry algorithm followed the establishment of the backscatter correction and a confirmation of the EPID's positional stability with linac gantry rotation. A detailed characterization of the attenuation, scatter, and EPID response behind an object in the beam's path is necessary to predict transit PDIs. In order to validate the algorithm's performance, 49 IMRT fields were delivered to a

  4. A generalized calibration procedure for in vivo transit dosimetry using siemens electronic portal imaging devices.

    PubMed

    Fidanzio, Andrea; Greco, Francesca; Gargiulo, Laura; Cilla, Savino; Sabatino, Domenico; Cappiello, Massimo; Di Felice, Cinzia; Di Castro, Elisabetta; Azario, Luigi; Russo, Mariateresa; Pompei, Luciano; D'Onofrio, Guido; Piermattei, Angelo

    2011-03-01

    A practical and accurate generalized in vivo dosimetry procedure has been implemented for Siemens linacs supplying 6, 10, and 15 MV photon beams, equipped with aSi electronic portal imaging devices (EPIDs). The in vivo dosimetry method makes use of correlation ratios between EPID transit signal, s (t) (0) (TPR,w,L), and phantom mid-plane dose, D (0)(TPR,w,L), as functions of phantom thickness, w, square field dimensions, L, and tissue-phantom ratio TPR(20,10). The s (t) (0) (TPR,w,L) and D (0)(TPR,w,L) values were defined to be independent of the EPID sensitivity and monitor unit calibration, while their dependence on TPR(20,10) was investigated to determine a set of generalized correlation ratios to be used for beams with TPR(20,10) falling in the examined range. This way, other radiotherapy centers can use the method with no need to locally perform the whole set of measurements in solid water phantoms, required to implement it. Tolerance levels for 3D conformal treatments, ranging between ±5 and ±6% according to tumor type and location, were estimated for comparison purposes between reconstructed isocenter dose, D (iso), and treatment planning system (TPS) computed dose D (iso,TPS). Finally a dedicated software, interfaceable with record and verify (R&V) systems used in the centers, was developed to obtain in vivo dosimetry results in less than 2 min after beam delivery.

  5. Calibration of portal imaging devices for radiotherapy in-vivo dosimetry

    NASA Astrophysics Data System (ADS)

    Piermattei, Angelo; Cilla, Savino; Fidanzio, Andrea; Greco, Francesca; Sabatino, Domenico; Gargiulo, Laura; Azario, Luigi

    2010-11-01

    The complexity of radiotherapy techniques requires an accurate verification of the dose delivered to the patient during treatment. Recently, the present authors have developed an in patient dose reconstruction method with X-ray beams for 3D conformal radiotherapy. The procedure is based on correlation functions defined by the ratios of the transit signal measured by an electronic portal imaging device (EPID) to the mid-plane dose measured by calibrated ion chambers in a solid water phantom. The dosimetric characterization of aSi EPIDs in terms of signal stability, linearity and dependence on field dimension pointed out that these detectors are useful for the transit dosimetry of photon beams. However, the aSi EPIDs manufactured by Varian, Elekta and Siemens for their linacs are at present used for the visual inspection of the patient's set-up, and their use as transit dosimeters needs a special calibration that requires an effort for every beam. The aim of this paper has been the determination of a generalized EPID calibration that can be used by linacs of different manufacturers equipped with aSi EPIDs. The transit dosimetry method here proposed could supply for every linac the reconstruction in real time of the isocenter dose in patients with a tolerance level ranging between ±4% and ±6% depending on the treatment type and body district.

  6. Automatic in vivo portal dosimetry of all treatments

    NASA Astrophysics Data System (ADS)

    Olaciregui-Ruiz, I.; Rozendaal, R.; Mijnheer, B.; van Herk, M.; Mans, A.

    2013-11-01

    At our institution EPID (electronic portal imaging device) dosimetry is routinely applied to perform in vivo dose verification of all patient treatments with curative intent since January 2008. The major impediment of the method has been the amount of work required to produce and inspect the in vivo dosimetry reports (a time-consuming and labor-intensive process). In this paper we present an overview of the actions performed to implement an automated in vivo dosimetry solution clinically. We reimplemented the EPID dosimetry software and modified the acquisition software. Furthermore, we introduced new tools to periodically inspect the record-and-verify database and automatically run the EPID dosimetry software when needed. In 2012, 95% of our 3839 treatments scheduled for in vivo dosimetry were analyzed automatically (27 633 portal images of intensity-modulated radiotherapy (IMRT) fields, 5551 portal image data of VMAT arcs, and 2003 portal images of non-IMRT fields). The in vivo dosimetry verification results are available a few minutes after delivery and alerts are immediately raised when deviations outside tolerance levels are detected. After the clinical introduction of this automated solution, inspection of the detected deviations is the only remaining work. These newly developed tools are a major step forward towards full integration of in vivo EPID dosimetry in radiation oncology practice.

  7. On flattening filter-free portal dosimetry.

    PubMed

    Pardo, Eduardo; Castro Novais, Juan; Molina López, María Yolanda; Ruiz Maqueda, Sheila

    2016-07-08

    Varian introduced (in 2010) the option of removing the flattening filter (FF) in their C-Arm linacs for intensity-modulated treatments. This mode, called flattening filter-free (FFF), offers the advantage of a greater dose rate. Varian's "Portal Dosimetry" is an electronic portal imager device (EPID)-based tool for IMRT verification. This tool lacks the capability of verifying flattening filter-free (FFF) modes due to saturation and lack of an image prediction algorithm. (Note: the latest versions of this software and EPID correct these issues.) The objective of the present study is to research the feasibility of said verifications (with the older versions of the software and EPID). By placing the EPID at a greater distance, the images can be acquired without saturation, yielding a linearity similar to the flattened mode. For the image prediction, a method was optimized based on the clinically used algorithm (analytical anisotropic algorithm (AAA)) over a homogeneous phantom. The depth inside the phantom and its electronic density were tailored. An application was developed to allow the conversion of a dose plane (in DICOM format) to Varian's custom format for Portal Dosimetry. The proposed method was used for the verification of test and clinical fields for the three qualities used in our institution for IMRT: 6X, 6FFF and 10FFF. The method developed yielded a positive verification (more than 95% of the points pass a 2%/2 mm gamma) for both the clinical and test fields. This method was also capable of "predicting" static and wedged fields. A workflow for the verification of FFF fields was developed. This method relies on the clinical algorithm used for dose calculation and is able to verify the FFF modes, as well as being useful for machine quality assurance. The procedure described does not require new hardware. This method could be used as a verification of Varian's Portal Dose Image Prediction.

  8. On flattening filter-free portal dosimetry.

    PubMed

    Pardo, Eduardo; Castro Novais, Juan; Molina López, María Yolanda; Ruiz Maqueda, Sheila

    2016-01-01

    Varian introduced (in 2010) the option of removing the flattening filter (FF) in their C-Arm linacs for intensity-modulated treatments. This mode, called flattening filter-free (FFF), offers the advantage of a greater dose rate. Varian's "Portal Dosimetry" is an electronic portal imager device (EPID)-based tool for IMRT verification. This tool lacks the capability of verifying flattening filter-free (FFF) modes due to saturation and lack of an image prediction algorithm. (Note: the latest versions of this software and EPID correct these issues.) The objective of the present study is to research the feasibility of said verifications (with the older versions of the software and EPID). By placing the EPID at a greater distance, the images can be acquired without saturation, yielding a linearity similar to the flattened mode. For the image prediction, a method was optimized based on the clinically used algorithm (analytical anisotropic algorithm (AAA)) over a homogeneous phantom. The depth inside the phantom and its electronic density were tailored. An application was developed to allow the conversion of a dose plane (in DICOM format) to Varian's custom format for Portal Dosimetry. The proposed method was used for the verification of test and clinical fields for the three qualities used in our institution for IMRT: 6X, 6FFF and 10FFF. The method developed yielded a positive verification (more than 95% of the points pass a 2%/2 mm gamma) for both the clinical and test fields. This method was also capable of "predicting" static and wedged fields. A workflow for the verification of FFF fields was developed. This method relies on the clinical algorithm used for dose calculation and is able to verify the FFF modes, as well as being useful for machine quality assurance. The procedure described does not require new hardware. This method could be used as a verification of Varian's Portal Dose Image Prediction. PMID:27455487

  9. Fast transit portal dosimetry using density-scaled layer modeling of aSi-based electronic portal imaging device and Monte Carlo method

    SciTech Connect

    Jung, Jae Won; Kim, Jong Oh; Yeo, Inhwan Jason; Cho, Young-Bin; Kim, Sun Mo; DiBiase, Steven

    2012-12-15

    Purpose: Fast and accurate transit portal dosimetry was investigated by developing a density-scaled layer model of electronic portal imaging device (EPID) and applying it to a clinical environment. Methods: The model was developed for fast Monte Carlo dose calculation. The model was validated through comparison with measurements of dose on EPID using first open beams of varying field sizes under a 20-cm-thick flat phantom. After this basic validation, the model was further tested by applying it to transit dosimetry and dose reconstruction that employed our predetermined dose-response-based algorithm developed earlier. The application employed clinical intensity-modulated beams irradiated on a Rando phantom. The clinical beams were obtained through planning on pelvic regions of the Rando phantom simulating prostate and large pelvis intensity modulated radiation therapy. To enhance agreement between calculations and measurements of dose near penumbral regions, convolution conversion of acquired EPID images was alternatively used. In addition, thickness-dependent image-to-dose calibration factors were generated through measurements of image and calculations of dose in EPID through flat phantoms of various thicknesses. The factors were used to convert acquired images in EPID into dose. Results: For open beam measurements, the model showed agreement with measurements in dose difference better than 2% across open fields. For tests with a Rando phantom, the transit dosimetry measurements were compared with forwardly calculated doses in EPID showing gamma pass rates between 90.8% and 98.8% given 4.5 mm distance-to-agreement (DTA) and 3% dose difference (DD) for all individual beams tried in this study. The reconstructed dose in the phantom was compared with forwardly calculated doses showing pass rates between 93.3% and 100% in isocentric perpendicular planes to the beam direction given 3 mm DTA and 3% DD for all beams. On isocentric axial planes, the pass rates varied

  10. Calibration of an amorphous-silicon flat panel portal imager for exit-beam dosimetry

    SciTech Connect

    Chen, Josephine; Chuang, Cynthia F.; Morin, Olivier; Aubin, Michele; Pouliot, Jean

    2006-03-15

    Amorphous-silicon flat panel detectors are currently used to acquire digital portal images with excellent image quality for patient alignment before external beam radiation therapy. As a first step towards interpreting portal images acquired during treatment in terms of the actual dose delivered to the patient, a calibration method is developed to convert flat panel portal images to the equivalent water dose deposited in the detector plane and at a depth of 1.5 cm. The method is based on empirical convolution models of dose deposition in the flat panel detector and in water. A series of calibration experiments comparing the response of the flat panel imager and ion chamber measurements of dose in water determines the model parameters. Kernels derived from field size measurements account for the differences in the production and detection of scattered radiation in the two systems. The dissimilar response as a function of beam energy spectrum is characterized from measurements performed at various off-axis positions and for increasing attenuator thickness in the beam. The flat panel pixel inhomogeneity is corrected by comparing a large open field image with profiles measured in water. To verify the accuracy of the calibration method, calibrated flat panel profiles were compared with measured dose profiles for fields delivered through solid water slabs, a solid water phantom containing an air cavity, and an anthropomorphic head phantom. Open rectangular fields of various sizes and locations as well as a multileaf collimator-shaped field were delivered. For all but the smallest field centered about the central axis, the calibrated flat panel profiles matched the measured dose profiles with little or no systematic deviation and approximately 3% (two standard deviations) accuracy for the in-field region. The calibrated flat panel profiles for fields located off the central axis showed a small -1.7% systematic deviation from the measured profiles for the in-field region

  11. A novel algorithm for the reconstruction of an entrance beam fluence from treatment exit patient portal dosimetry images

    NASA Astrophysics Data System (ADS)

    Sperling, Nicholas Niven

    The problem of determining the in vivo dosimetry for patients undergoing radiation treatment has been an area of interest since the development of the field. Most methods which have found clinical acceptance work by use of a proxy dosimeter, e.g.: glass rods, using radiophotoluminescence; thermoluminescent dosimeters (TLD), typically CaF or LiF; Metal Oxide Silicon Field Effect Transistor (MOSFET) dosimeters, using threshold voltage shift; Optically Stimulated Luminescent Dosimeters (OSLD), composed of Carbon doped Aluminum Dioxide crystals; RadioChromic film, using leuko-dye polymers; Silicon Diode dosimeters, typically p-type; and ion chambers. More recent methods employ Electronic Portal Image Devices (EPID), or dosimeter arrays, for entrance or exit beam fluence determination. The difficulty with the proxy in vivo dosimetery methods is the requirement that they be placed at the particular location where the dose is to be determined. This precludes measurements across the entire patient volume. These methods are best suited where the dose at a particular location is required. The more recent methods of in vivo dosimetry make use of detector arrays and reconstruction techniques to determine dose throughout the patient volume. One method uses an array of ion chambers located upstream of the patient. This requires a special hardware device and places an additional attenuator in the beam path, which may not be desirable. A final approach is to use the existing EPID, which is part of most modern linear accelerators, to image the patient using the treatment beam. Methods exist to deconvolve the detector function of the EPID using a series of weighted exponentials. Additionally, this method has been extended to determine in vivo dosimetry. The method developed here employs the use of EPID images and an iterative deconvolution algorithm to reconstruct the impinging primary beam fluence on the patient. This primary fluence may then be employed to determine dose through

  12. Conditions for reliable time-resolved dosimetry of electronic portal imaging devices for fixed-gantry IMRT and VMAT

    SciTech Connect

    Yeo, Inhwan Jason; Patyal, Baldev; Mandapaka, Anant; Jung, Jae Won; Yi, Byong Yong; Kim, Jong Oh

    2013-07-15

    Purpose: The continuous scanning mode of electronic portal imaging devices (EPID) that offers time-resolved information has been newly explored for verifying dynamic radiation deliveries. This study seeks to determine operating conditions (dose rate stability and time resolution) under which that mode can be used accurately for the time-resolved dosimetry of intensity-modulated radiation therapy (IMRT) beams.Methods: The authors have designed the following test beams with variable beam holdoffs and dose rate regulations: a 10 Multiplication-Sign 10 cm open beam to serve as a reference beam; a sliding window (SW) beam utilizing the motion of a pair of multileaf collimator (MLC) leaves outside the 10 Multiplication-Sign 10 cm jaw; a step and shoot (SS) beam to move the pair in step; a volumetric modulated arc therapy (VMAT) beam. The beams were designed in such a way that they all produce the same open beam output of 10 Multiplication-Sign 10 cm. Time-resolved ion chamber measurements at isocenter and time-resolved and integrating EPID measurements were performed for all beams. The time-resolved EPID measurements were evaluated through comparison with the ion chamber and integrating EPID measurements, as the latter are accepted procedures. For two-dimensional, time-resolved evaluation, a VMAT beam with an infield MLC travel was designed. Time-resolved EPID measurements and Monte Carlo calculations of such EPID dose images for this beam were performed and intercompared.Results: For IMRT beams (SW and SS), the authors found disagreement greater than 2%, caused by frame missing of the time-resolved mode. However, frame missing disappeared, yielding agreement better than 2%, when the dose rate of irradiation (and thus the frame acquisition rates) reached a stable and planned rate as the dose of irradiation was raised past certain thresholds (a minimum 12 s of irradiation per shoot used for SS IMRT). For VMAT, the authors found that dose rate does not affect the frame

  13. Feasibility of portal dosimetry for flattening filter-free radiotherapy.

    PubMed

    Chuter, Robert W; Rixham, Philip A; Weston, Steve J; Cosgrove, Vivian P

    2016-01-08

    The feasibility of using portal dosimetry (PD) to verify 6 MV flattening filter-free (FFF) IMRT treatments was investigated. An Elekta Synergy linear accelerator with an Agility collimator capable of delivering FFF beams and a standard iViewGT amorphous silicon (aSi) EPID panel (RID 1640 AL5P) at a fixed SSD of 160 cm were used. Dose rates for FFF beams are up to four times higher than for conventional flattened beams, meaning images taken at maximum FFF dose rate can saturate the EPID. A dose rate of 800 MU/min was found not to saturate the EPID for open fields. This dose rate was subsequently used to characterize the EPID for FFF portal dosimetry. A range of open and phantom fields were measured with both an ion chamber and the EPID, to allow comparison between the two. The measured data were then used to create a model within The Nederlands Kanker Instituut's (NKI's) portal dosimetry software. The model was verified using simple square fields with a range of field sizes and phantom thicknesses. These were compared to calculations performed with the Monaco treatment planning system (TPS) and isocentric ion chamber measurements. It was found that the results for the FFF verification were similar to those for flattened beams with testing on square fields, indicating a difference in dose between the TPS and portal dosimetry of approximately 1%. Two FFF IMRT plans (prostate and lung SABR) were delivered to a homogeneous phantom and showed an overall dose difference at isocenter of ~0.5% and good agreement between the TPS and PD dose distributions. The feasibility of using the NKI software without any modifications for high-dose-rate FFF beams and using a standard EPID detector has been investigated and some initial limitations highlighted.

  14. Feasibility of portal dosimetry for flattening filter-free radiotherapy.

    PubMed

    Chuter, Robert W; Rixham, Philip A; Weston, Steve J; Cosgrove, Vivian P

    2016-01-01

    The feasibility of using portal dosimetry (PD) to verify 6 MV flattening filter-free (FFF) IMRT treatments was investigated. An Elekta Synergy linear accelerator with an Agility collimator capable of delivering FFF beams and a standard iViewGT amorphous silicon (aSi) EPID panel (RID 1640 AL5P) at a fixed SSD of 160 cm were used. Dose rates for FFF beams are up to four times higher than for conventional flattened beams, meaning images taken at maximum FFF dose rate can saturate the EPID. A dose rate of 800 MU/min was found not to saturate the EPID for open fields. This dose rate was subsequently used to characterize the EPID for FFF portal dosimetry. A range of open and phantom fields were measured with both an ion chamber and the EPID, to allow comparison between the two. The measured data were then used to create a model within The Nederlands Kanker Instituut's (NKI's) portal dosimetry software. The model was verified using simple square fields with a range of field sizes and phantom thicknesses. These were compared to calculations performed with the Monaco treatment planning system (TPS) and isocentric ion chamber measurements. It was found that the results for the FFF verification were similar to those for flattened beams with testing on square fields, indicating a difference in dose between the TPS and portal dosimetry of approximately 1%. Two FFF IMRT plans (prostate and lung SABR) were delivered to a homogeneous phantom and showed an overall dose difference at isocenter of ~0.5% and good agreement between the TPS and PD dose distributions. The feasibility of using the NKI software without any modifications for high-dose-rate FFF beams and using a standard EPID detector has been investigated and some initial limitations highlighted. PMID:26894337

  15. Implementation of IMRT and VMAT using Delta4 phantom and portal dosimetry as dosimetry verification tools

    NASA Astrophysics Data System (ADS)

    Daci, Lulzime; Malkaj, Partizan

    2016-03-01

    In this study we analyzed and compared the dose distribution of different IMRT and VMAT plans with the intent to provide pre-treatment quality assurance using two different tools. Materials/Methods: We have used the electronic portal imaging device EPID after calibration to dose and correction for the background offset signal and also the Delta4 phantom after en evaluation of angular sensitivity. The Delta4 phantom has a two-dimensional array with ionization chambers. We analyzed three plans for each anatomical site calculated by Eclipse treatment planning system. The measurements were analyzed using γ-evaluation method with passing criteria 3% absolute dose and 3 mm distance to agreement (DTA). For all the plans the range of score has been from 97% to 99% for gantry fixed at 0° while for rotational planes there was a slightly decreased pass rates and above 95%. Point measurement with a ionization chamber were done in additional to see the accuracy of portal dosimetry and to evaluate the Delta4 device to various dose rates. Conclusions: Both Delt4 and Portal dosimetry shows good results between the measured and calculated doses. While Delta4 is more accurate in measurements EPID is more time efficient. We have decided to use both methods in the first steps of IMRT and VMAT implementation and later on to decide which of the tools to use depending on the complexity of plans, how much accurate we want to be and the time we have on the machine.

  16. SU-E-T-335: Transit Dosimetry for Verification of Dose Delivery Using Electronic Portal Imaging Device (EPID)

    SciTech Connect

    Baek, T; Chung, E; Lee, S; Yoon, M

    2014-06-01

    Purpose: To evaluate the effectiveness of transit dose, measured with an electronic portal imaging device (EPID), in verifying actual dose delivery to patients. Methods: Plans of 5 patients with lung cancer, who received IMRT treatment, were examined using homogeneous solid water phantom and inhomogeneous anthropomorphic phantom. To simulate error in patient positioning, the anthropomorphic phantom was displaced from 5 mm to 10 mm in the inferior to superior (IS), superior to inferior (SI), left to right (LR), and right to left (RL) directions. The transit dose distribution was measured with EPID and was compared to the planed dose using gamma index. Results: Although the average passing rate based on gamma index (GI) with a 3% dose and a 3 mm distance-to-dose agreement tolerance limit was 94.34 % for the transit dose with homogeneous phantom, it was reduced to 84.63 % for the transit dose with inhomogeneous anthropomorphic phantom. The Result also shows that the setup error of 5mm (10mm) in IS, SI, LR and SI direction can Result in the decrease in values of GI passing rates by 1.3% (3.0%), 2.2% (4.3%), 5.9% (10.9%), and 8.9% (16.3%), respectively. Conclusion: Our feasibility study suggests that the transit dose-based quality assurance may provide information regarding accuracy of dose delivery as well as patient positioning.

  17. Denoising portal images by means of wavelet techniques

    NASA Astrophysics Data System (ADS)

    Gonzalez Lopez, Antonio Francisco

    Portal images are used in radiotherapy for the verification of patient positioning. The distinguishing feature of this image type lies in its formation process: the same beam used for patient treatment is used for image formation. The high energy of the photons used in radiotherapy strongly limits the quality of portal images: Low contrast between tissues, low spatial resolution and low signal to noise ratio. This Thesis studies the enhancement of these images, in particular denoising of portal images. The statistical properties of portal images and noise are studied: power spectra, statistical dependencies between image and noise and marginal, joint and conditional distributions in the wavelet domain. Later, various denoising methods are applied to noisy portal images. Methods operating in the wavelet domain are the basis of this Thesis. In addition, the Wiener filter and the non local means filter (NLM), operating in the image domain, are used as a reference. Other topics studied in this Thesis are spatial resolution, wavelet processing and image processing in dosimetry in radiotherapy. In this regard, the spatial resolution of portal imaging systems is studied; a new method for determining the spatial resolution of the imaging equipments in digital radiology is presented; the calculation of the power spectrum in the wavelet domain is studied; reducing uncertainty in film dosimetry is investigated; a method for the dosimetry of small radiation fields with radiochromic film is presented; the optimal signal resolution is determined, as a function of the noise level and the quantization step, in the digitization process of films and the useful optical density range is set, as a function of the required uncertainty level, for a densitometric system. Marginal distributions of portal images are similar to those of natural images. This also applies to the statistical relationships between wavelet coefficients, intra-band and inter-band. These facts result in a better

  18. Interfractional trend analysis of dose differences based on 2D transit portal dosimetry

    NASA Astrophysics Data System (ADS)

    Persoon, L. C. G. G.; Nijsten, S. M. J. J. G.; Wilbrink, F. J.; Podesta, M.; Snaith, J. A. D.; Lustberg, T.; van Elmpt, W. J. C.; van Gils, F.; Verhaegen, F.

    2012-10-01

    Dose delivery of a radiotherapy treatment can be influenced by a number of factors. It has been demonstrated that the electronic portal imaging device (EPID) is valuable for transit portal dosimetry verification. Patient related dose differences can emerge at any time during treatment and can be categorized in two types: (1) systematic—appearing repeatedly, (2) random—appearing sporadically during treatment. The aim of this study is to investigate how systematic and random information appears in 2D transit dose distributions measured in the EPID plane over the entire course of a treatment and how this information can be used to examine interfractional trends, building toward a methodology to support adaptive radiotherapy. To create a trend overview of the interfractional changes in transit dose, the predicted portal dose for the different beams is compared to a measured portal dose using a γ evaluation. For each beam of the delivered fraction, information is extracted from the γ images to differentiate systematic from random dose delivery errors. From the systematic differences of a fraction for a projected anatomical structures, several metrics are extracted like percentage pixels with |γ| > 1. We demonstrate for four example cases the trends and dose difference causes which can be detected with this method. Two sample prostate cases show the occurrence of a random and systematic difference and identify the organ that causes the difference. In a lung cancer case a trend is shown of a rapidly diminishing atelectasis (lung fluid) during the course of treatment, which was detected with this trend analysis method. The final example is a breast cancer case where we show the influence of set-up differences on the 2D transit dose. A method is presented based on 2D portal transit dosimetry to record dose changes throughout the course of treatment, and to allow trend analysis of dose discrepancies. We show in example cases that this method can identify the causes of

  19. SU-E-J-235: Varian Portal Dosimetry Accuracy at Detecting Simulated Delivery Errors

    SciTech Connect

    Gordon, J; Bellon, M; Barton, K; Gulam, M; Chetty, I

    2014-06-01

    Purpose: To use receiver operating characteristic (ROC) analysis to quantify the Varian Portal Dosimetry (VPD) application's ability to detect delivery errors in IMRT fields. Methods: EPID and VPD were calibrated/commissioned using vendor-recommended procedures. Five clinical plans comprising 56 modulated fields were analyzed using VPD. Treatment sites were: pelvis, prostate, brain, orbit, and base of tongue. Delivery was on a Varian Trilogy linear accelerator at 6MV using a Millenium120 multi-leaf collimator. Image pairs (VPD-predicted and measured) were exported in dicom format. Each detection test imported an image pair into Matlab, optionally inserted a simulated error (rectangular region with intensity raised or lowered) into the measured image, performed 3%/3mm gamma analysis, and saved the gamma distribution. For a given error, 56 negative tests (without error) were performed, one per 56 image pairs. Also, 560 positive tests (with error) with randomly selected image pairs and randomly selected in-field error location. Images were classified as errored (or error-free) if percent pixels with γ<κ was < (or ≥) τ. (Conventionally, κ=1 and τ=90%.) A ROC curve was generated from the 616 tests by varying τ. For a range of κ and τ, true/false positive/negative rates were calculated. This procedure was repeated for inserted errors of different sizes. VPD was considered to reliably detect an error if images were correctly classified as errored or error-free at least 95% of the time, for some κ+τ combination. Results: 20mm{sup 2} errors with intensity altered by ≥20% could be reliably detected, as could 10mm{sup 2} errors with intensity was altered by ≥50%. Errors with smaller size or intensity change could not be reliably detected. Conclusion: Varian Portal Dosimetry using 3%/3mm gamma analysis is capable of reliably detecting only those fluence errors that exceed the stated sizes. Images containing smaller errors can pass mathematical analysis, though

  20. Prediction of DVH parameter changes due to setup errors for breast cancer treatment based on 2D portal dosimetry

    SciTech Connect

    Nijsten, S. M. J. J. G.; Elmpt, W. J. C. van; Mijnheer, B. J.; Minken, A. W. H.; Persoon, L. C. G. G.; Lambin, P.; Dekker, A. L. A. J.

    2009-01-15

    Electronic portal imaging devices (EPIDs) are increasingly used for portal dosimetry applications. In our department, EPIDs are clinically used for two-dimensional (2D) transit dosimetry. Predicted and measured portal dose images are compared to detect dose delivery errors caused for instance by setup errors or organ motion. The aim of this work is to develop a model to predict dose-volume histogram (DVH) changes due to setup errors during breast cancer treatment using 2D transit dosimetry. First, correlations between DVH parameter changes and 2D gamma parameters are investigated for different simulated setup errors, which are described by a binomial logistic regression model. The model calculates the probability that a DVH parameter changes more than a specific tolerance level and uses several gamma evaluation parameters for the planning target volume (PTV) projection in the EPID plane as input. Second, the predictive model is applied to clinically measured portal images. Predicted DVH parameter changes are compared to calculated DVH parameter changes using the measured setup error resulting from a dosimetric registration procedure. Statistical accuracy is investigated by using receiver operating characteristic (ROC) curves and values for the area under the curve (AUC), sensitivity, specificity, positive and negative predictive values. Changes in the mean PTV dose larger than 5%, and changes in V{sub 90} and V{sub 95} larger than 10% are accurately predicted based on a set of 2D gamma parameters. Most pronounced changes in the three DVH parameters are found for setup errors in the lateral-medial direction. AUC, sensitivity, specificity, and negative predictive values were between 85% and 100% while the positive predictive values were lower but still higher than 54%. Clinical predictive value is decreased due to the occurrence of patient rotations or breast deformations during treatment, but the overall reliability of the predictive model remains high. Based on our

  1. Quantitative imaging for clinical dosimetry

    NASA Astrophysics Data System (ADS)

    Bardiès, Manuel; Flux, Glenn; Lassmann, Michael; Monsieurs, Myriam; Savolainen, Sauli; Strand, Sven-Erik

    2006-12-01

    Patient-specific dosimetry in nuclear medicine is now a legal requirement in many countries throughout the EU for targeted radionuclide therapy (TRT) applications. In order to achieve that goal, an increased level of accuracy in dosimetry procedures is needed. Current research in nuclear medicine dosimetry should not only aim at developing new methods to assess the delivered radiation absorbed dose at the patient level, but also to ensure that the proposed methods can be put into practice in a sufficient number of institutions. A unified dosimetry methodology is required for making clinical outcome comparisons possible.

  2. Quantifying the performance of in vivo portal dosimetry in detecting four types of treatment parameter variations

    SciTech Connect

    Bojechko, C.; Ford, E. C.

    2015-12-15

    Purpose: To quantify the ability of electronic portal imaging device (EPID) dosimetry used during treatment (in vivo) in detecting variations that can occur in the course of patient treatment. Methods: Images of transmitted radiation from in vivo EPID measurements were converted to a 2D planar dose at isocenter and compared to the treatment planning dose using a prototype software system. Using the treatment planning system (TPS), four different types of variability were modeled: overall dose scaling, shifting the positions of the multileaf collimator (MLC) leaves, shifting of the patient position, and changes in the patient body contour. The gamma pass rate was calculated for the modified and unmodified plans and used to construct a receiver operator characteristic (ROC) curve to assess the detectability of the different parameter variations. The detectability is given by the area under the ROC curve (AUC). The TPS was also used to calculate the impact of the variations on the target dose–volume histogram. Results: Nine intensity modulation radiation therapy plans were measured for four different anatomical sites consisting of 70 separate fields. Results show that in vivo EPID dosimetry was most sensitive to variations in the machine output, AUC = 0.70 − 0.94, changes in patient body habitus, AUC = 0.67 − 0.88, and systematic shifts in the MLC bank positions, AUC = 0.59 − 0.82. These deviations are expected to have a relatively small clinical impact [planning target volume (PTV) D{sub 99} change <7%]. Larger variations have even higher detectability. Displacements in the patient’s position and random variations in MLC leaf positions were not readily detectable, AUC < 0.64. The D{sub 99} of the PTV changed by up to 57% for the patient position shifts considered here. Conclusions: In vivo EPID dosimetry is able to detect relatively small variations in overall dose, systematic shifts of the MLC’s, and changes in the patient habitus. Shifts in the

  3. Time-resolved versus time-integrated portal dosimetry: the role of an object's position with respect to the isocenter in volumetric modulated arc therapy.

    PubMed

    Schyns, Lotte E J R; Persoon, Lucas C G G; Podesta, Mark; van Elmpt, Wouter J C; Verhaegen, Frank

    2016-05-21

    The aim of this work is to compare time-resolved (TR) and time-integrated (TI) portal dosimetry, focussing on the role of an object's position with respect to the isocenter in volumetric modulated arc therapy (VMAT). Portal dose images (PDIs) are simulated and measured for different cases: a sphere (1), a bovine bone (2) and a patient geometry (3). For the simulated case (1) and the experimental case (2), several transformations are applied at different off-axis positions. In the patient case (3), three simple plans with different isocenters are created and pleural effusion is simulated in the patient. The PDIs before and after the sphere transformations, as well as the PDIs with and without simulated pleural effusion, are compared using a TI and TR gamma analysis. In addition, the performance of the TI and TR gamma analyses for the detection of real geometric changes in patients treated with clinical plans is investigated and a correlation analysis is performed between gamma fail rates and differences in dose volume histogram (DVH) metrics. The TI gamma analysis can show large differences in gamma fail rates for the same transformation at different off-axis positions (or for different plan isocenters). The TR gamma analysis, however, shows consistent gamma fail rates. For the detection of real geometric changes in patients treated with clinical plans, the TR gamma analysis has a higher sensitivity than the TI gamma analysis. However, the specificity for the TR gamma analysis is lower than for the TI gamma analysis. Both the TI and TR gamma fail rates show no correlation with changes in DVH metrics. This work shows that TR portal dosimetry is fundamentally superior to TI portal dosimetry, because it removes the strong dependence of the gamma fail rate on the off-axis position/plan isocenter. However, for 2D TR portal dosimetry, it is still difficult to interpret gamma fail rates in terms of changes in DVH metrics for patients treated with VMAT.

  4. Time-resolved versus time-integrated portal dosimetry: the role of an object’s position with respect to the isocenter in volumetric modulated arc therapy

    NASA Astrophysics Data System (ADS)

    Schyns, Lotte E. J. R.; Persoon, Lucas C. G. G.; Podesta, Mark; van Elmpt, Wouter J. C.; Verhaegen, Frank

    2016-05-01

    The aim of this work is to compare time-resolved (TR) and time-integrated (TI) portal dosimetry, focussing on the role of an object’s position with respect to the isocenter in volumetric modulated arc therapy (VMAT). Portal dose images (PDIs) are simulated and measured for different cases: a sphere (1), a bovine bone (2) and a patient geometry (3). For the simulated case (1) and the experimental case (2), several transformations are applied at different off-axis positions. In the patient case (3), three simple plans with different isocenters are created and pleural effusion is simulated in the patient. The PDIs before and after the sphere transformations, as well as the PDIs with and without simulated pleural effusion, are compared using a TI and TR gamma analysis. In addition, the performance of the TI and TR gamma analyses for the detection of real geometric changes in patients treated with clinical plans is investigated and a correlation analysis is performed between gamma fail rates and differences in dose volume histogram (DVH) metrics. The TI gamma analysis can show large differences in gamma fail rates for the same transformation at different off-axis positions (or for different plan isocenters). The TR gamma analysis, however, shows consistent gamma fail rates. For the detection of real geometric changes in patients treated with clinical plans, the TR gamma analysis has a higher sensitivity than the TI gamma analysis. However, the specificity for the TR gamma analysis is lower than for the TI gamma analysis. Both the TI and TR gamma fail rates show no correlation with changes in DVH metrics. This work shows that TR portal dosimetry is fundamentally superior to TI portal dosimetry, because it removes the strong dependence of the gamma fail rate on the off-axis position/plan isocenter. However, for 2D TR portal dosimetry, it is still difficult to interpret gamma fail rates in terms of changes in DVH metrics for patients treated with VMAT.

  5. Phase contrast portal imaging using synchrotron radiation

    SciTech Connect

    Umetani, K.; Kondoh, T.

    2014-07-15

    Microbeam radiation therapy is an experimental form of radiation treatment with great potential to improve the treatment of many types of cancer. We applied a synchrotron radiation phase contrast technique to portal imaging to improve targeting accuracy for microbeam radiation therapy in experiments using small animals. An X-ray imaging detector was installed 6.0 m downstream from an object to produce a high-contrast edge enhancement effect in propagation-based phase contrast imaging. Images of a mouse head sample were obtained using therapeutic white synchrotron radiation with a mean beam energy of 130 keV. Compared to conventional portal images, remarkably clear images of bones surrounding the cerebrum were acquired in an air environment for positioning brain lesions with respect to the skull structure without confusion with overlapping surface structures.

  6. Phase contrast portal imaging using synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Umetani, K.; Kondoh, T.

    2014-07-01

    Microbeam radiation therapy is an experimental form of radiation treatment with great potential to improve the treatment of many types of cancer. We applied a synchrotron radiation phase contrast technique to portal imaging to improve targeting accuracy for microbeam radiation therapy in experiments using small animals. An X-ray imaging detector was installed 6.0 m downstream from an object to produce a high-contrast edge enhancement effect in propagation-based phase contrast imaging. Images of a mouse head sample were obtained using therapeutic white synchrotron radiation with a mean beam energy of 130 keV. Compared to conventional portal images, remarkably clear images of bones surrounding the cerebrum were acquired in an air environment for positioning brain lesions with respect to the skull structure without confusion with overlapping surface structures.

  7. Initial Clinical Experience Performing Patient Treatment Verification With an Electronic Portal Imaging Device Transit Dosimeter

    SciTech Connect

    Berry, Sean L.; Polvorosa, Cynthia; Cheng, Simon; Deutsch, Israel; Chao, K. S. Clifford; Wuu, Cheng-Shie

    2014-01-01

    Purpose: To prospectively evaluate a 2-dimensional transit dosimetry algorithm's performance on a patient population and to analyze the issues that would arise in a widespread clinical adoption of transit electronic portal imaging device (EPID) dosimetry. Methods and Materials: Eleven patients were enrolled on the protocol; 9 completed and were analyzed. Pretreatment intensity modulated radiation therapy (IMRT) patient-specific quality assurance was performed using a stringent local 3%, 3-mm γ criterion to verify that the planned fluence had been appropriately transferred to and delivered by the linear accelerator. Transit dosimetric EPID images were then acquired during treatment and compared offline with predicted transit images using a global 5%, 3-mm γ criterion. Results: There were 288 transit images analyzed. The overall γ pass rate was 89.1% ± 9.8% (average ± 1 SD). For the subset of images for which the linear accelerator couch did not interfere with the measurement, the γ pass rate was 95.7% ± 2.4%. A case study is presented in which the transit dosimetry algorithm was able to identify that a lung patient's bilateral pleural effusion had resolved in the time between the planning CT scan and the treatment. Conclusions: The EPID transit dosimetry algorithm under consideration, previously described and verified in a phantom study, is feasible for use in treatment delivery verification for real patients. Two-dimensional EPID transit dosimetry can play an important role in indicating when a treatment delivery is inconsistent with the original plan.

  8. Dosimetric properties of the Theraview fluoroscopic electronic portal imaging device.

    PubMed

    Glendinning, A G; Bonnett, D E

    2000-05-01

    Electronic portal imaging devices (EPIDs) can be used for non-imaging applications in radiotherapy such as patient dosimetry. Of the systems available, the fluoroscopic camera-based EPID Theraview (InfiMed Inc.) has not been studied to date, and a review of the dosimetric properties of the system is presented here. In the "single set-up" mode of image acquisition, pixel intensity increases sublinearly with applied dose. The response was dependent on the system's video signal gain and showed a threshold dose to the detector in the range 0.05-0.35 cGy, and pixel saturation at detector doses in the range 1.2-1.6 cGy. Repeated exposures of the EPID were observed to be extremely reproducible (standard deviation 0.5%). The sensitivity of the system showed a linear decline of 0.04% day-1 over a 68-day period, during which time the relative off-axis response within 10 x 10 cm2 field was constant to within a standard deviation of 0.56%. The system shows spatial non-uniformity, which requires correction for application to dose measurements in two-dimensions. Warm-up of the camera control unit required a period of at least 40 min and was associated with an enhancement in pixel intensity of up to 12%. A radiation dose history effect was observed at doses as low as 0.2 Gy. Camera dark current was shown to be negligible at normal accelerator operation. No discernible image distortion was found. Mechanical stability on gantry rotation was also assessed and image displacement of up to 5 mm at the isocentre was observed. It was concluded that the device could be used for dosimetry provided necessary precautions were observed and corrections made. PMID:10884749

  9. Open source portal to distributed image repositories

    NASA Astrophysics Data System (ADS)

    Tao, Wenchao; Ratib, Osman M.; Kho, Hwa; Hsu, Yung-Chao; Wang, Cun; Lee, Cason; McCoy, J. M.

    2004-04-01

    In large institution PACS, patient data may often reside in multiple separate systems. While most systems tend to be DICOM compliant, none of them offer the flexibility of seamless integration of multiple DICOM sources through a single access point. We developed a generic portal system with a web-based interactive front-end as well as an application programming interface (API) that allows both web users and client applications to query and retrieve image data from multiple DICOM sources. A set of software tools was developed to allow accessing several DICOM archives through a single point of access. An interactive web-based front-end allows user to search image data seamlessly from the different archives and display the results or route the image data to another DICOM compliant destination. An XML-based API allows other software programs to easily benefit from this portal to query and retrieve image data as well. Various techniques are employed to minimize the performance overhead inherent in the DICOM. The system is integrated with a hospital-wide HIPAA-compliant authentication and auditing service that provides centralized management of access to patient medical records. The system is provided under open source free licensing and developed using open-source components (Apache Tomcat for web server, MySQL for database, OJB for object/relational data mapping etc.). The portal paradigm offers a convenient and effective solution for accessing multiple image data sources in a given healthcare enterprise and can easily be extended to multi-institution through appropriate security and encryption mechanisms.

  10. Practical guidelines for routine intensity-modulated radiotherapy verification: pre-treatment verification with portal dosimetry and treatment verification with in vivo dosimetry

    PubMed Central

    Vinall, A J; Williams, A J; Currie, V E; Van Esch, A; Huyskens, D

    2010-01-01

    The purpose of this work is to provide guidelines for the routine use of portal dosimetry and in vivo diode measurements to verify intensity-modulated radiotherapy (IMRT) treatments. To achieve tolerance levels that are sensitive enough to intercept problems, both the portal dosimetry and the in vivo procedure must be optimised. Portal dosimetry was improved by the introduction of an optimised two-dimensional (2D) profile correction, which also accounted for the effect of backscatter from the R-arm. The scaled score, indicating the fraction of points not meeting the desired gamma evaluation criteria within the field opening, was determined as the parameter of interest. Using gamma criteria of a 3% dose difference and 3 mm distance to agreement, a “scaled score” threshold value of 1.5% was chosen to indicate excessive tongue and groove and other problems. The pre-treatment portal dosimetry quality assurance (QA) does not encompass verification of the patient dose calculation or position, and so it is complemented by in vivo diode measurements. Diode positioning is crucial in IMRT, and so we describe a method for diode positioning at any suitable point. We achieved 95% of IMRT field measurements within ±5% and 99% within ±8%, with improved accuracy being achieved over time owing to better positioning. Although the careful preparation and setup of the diode measurements can be time-consuming, this is compensated for by the time efficiency of the optimised procedure. Both methods are now easily absorbed into the routine work of the department. PMID:20965905

  11. DRR and portal image registration for automatic patient positioning in radiotherapy treatment.

    PubMed

    Bastida-Jumilla, Ma Consuelo; Larrey-Ruiz, Jorge; Verdú-Monedero, Rafael; Morales-Sánchez, Juan; Sancho-Gómez, José-Luis

    2011-12-01

    Image processing turns out to be essential in the planning and verification of radiotherapy treatments. Before applying a radiotherapy treatment, a dosimetry planning must be performed. Usually, the planning is done by means of an X-ray volumetric analysis using computerized tomography, where the area to be radiated is marked out. During the treatment phase, it is necessary to place the patient under the particle accelerator exactly as considered in the dosimetry stage. Coarse alignment is achieved using fiduciary markers placed over the patient's skin as external references. Later, fine alignment is provided by comparing a digitally reconstructed radiography (DRR) from the planning stage and a portal image captured by the accelerator in the treatment stage. The preprocessing of DRR and portal images, as well as the minimization of the non-shared information between both kinds of images, is mandatory for the correct operation of the image registration algorithm. With this purpose, mathematical morphology and image processing techniques have been used. The present work describes a fully automatic method to calculate more accurately the necessary displacement of the couch to place the patient exactly at the planned position. The proposed method to achieve the correct positioning of the patient is based on advanced image registration techniques. Preliminary results show a perfect match with the displacement estimated by the physician.

  12. DRR and portal image registration for automatic patient positioning in radiotherapy treatment.

    PubMed

    Bastida-Jumilla, Ma Consuelo; Larrey-Ruiz, Jorge; Verdú-Monedero, Rafael; Morales-Sánchez, Juan; Sancho-Gómez, José-Luis

    2011-12-01

    Image processing turns out to be essential in the planning and verification of radiotherapy treatments. Before applying a radiotherapy treatment, a dosimetry planning must be performed. Usually, the planning is done by means of an X-ray volumetric analysis using computerized tomography, where the area to be radiated is marked out. During the treatment phase, it is necessary to place the patient under the particle accelerator exactly as considered in the dosimetry stage. Coarse alignment is achieved using fiduciary markers placed over the patient's skin as external references. Later, fine alignment is provided by comparing a digitally reconstructed radiography (DRR) from the planning stage and a portal image captured by the accelerator in the treatment stage. The preprocessing of DRR and portal images, as well as the minimization of the non-shared information between both kinds of images, is mandatory for the correct operation of the image registration algorithm. With this purpose, mathematical morphology and image processing techniques have been used. The present work describes a fully automatic method to calculate more accurately the necessary displacement of the couch to place the patient exactly at the planned position. The proposed method to achieve the correct positioning of the patient is based on advanced image registration techniques. Preliminary results show a perfect match with the displacement estimated by the physician. PMID:21455811

  13. Algorithms for contrast enhancement of electronic portal images

    NASA Astrophysics Data System (ADS)

    Díez, S.; Sánchez, S.

    2015-11-01

    An implementation of two new automatized image processing algorithms for contrast enhancement of portal images is presented as suitable tools which facilitate the setup verification and visualization of patients during radiotherapy treatments. In the first algorithm, called Automatic Segmentation and Histogram Stretching (ASHS), the portal image is automatically segmented in two sub-images delimited by the conformed treatment beam: one image consisting of the imaged patient obtained directly from the radiation treatment field, and the second one is composed of the imaged patient outside it. By segmenting the original image, a histogram stretching can be independently performed and improved in both regions. The second algorithm involves a two-step process. In the first step, a Normalization to Local Mean (NLM), an inverse restoration filter is applied by dividing pixel by pixel a portal image by its blurred version. In the second step, named Lineally Combined Local Histogram Equalization (LCLHE), the contrast of the original image is strongly improved by a Local Contrast Enhancement (LCE) algorithm, revealing the anatomical structures of patients. The output image is lineally combined with a portal image of the patient. Finally the output images of the previous algorithms (NLM and LCLHE) are lineally combined, once again, in order to obtain a contrast enhanced image. These two algorithms have been tested on several portal images with great results.

  14. Epid Dosimetry

    SciTech Connect

    Greer, Peter B.; Vial, Philip

    2011-05-05

    Electronic portal imaging devices (EPIDs) were introduced originally for patient position verification. The idea of using EPIDs for dosimetry was realised in the 1980s. Little was published on the topic until the mid 1990's, when the interest in EPIDs for dosimetry increased rapidly and continues to grow. The increasing research on EPID dosimetry coincided with the introduction of intensity modulated radiation therapy (IMRT). EPIDs are well suited to IMRT dosimetry because they are high resolution, two-dimensional (2D) digital detectors. They are also pre-existing on almost all modern linear accelerators. They generally show a linear response to increasing dose. Different types of EPIDs have been clinically implemented, and these have been described in several review papers. The current generation of commercially available EPIDs are indirect detection active matrix flat panel imagers, also known as amorphous silicon (a-Si) EPIDs. Disadvantages of a-Si EPIDs for dosimetry include non-water equivalent construction materials, and the energy sensitivity and optical scatter of the phosphor scintillators used to create optical signal from the megavoltage beam. This report discusses current knowledge regarding a-Si EPIDs for dosimetry.

  15. Epid Dosimetry

    NASA Astrophysics Data System (ADS)

    Greer, Peter B.; Vial, Philip

    2011-05-01

    Electronic portal imaging devices (EPIDs) were introduced originally for patient position verification. The idea of using EPIDs for dosimetry was realised in the 1980s. Little was published on the topic until the mid 1990's, when the interest in EPIDs for dosimetry increased rapidly and continues to grow. The increasing research on EPID dosimetry coincided with the introduction of intensity modulated radiation therapy (IMRT). EPIDs are well suited to IMRT dosimetry because they are high resolution, two-dimensional (2D) digital detectors. They are also pre-existing on almost all modern linear accelerators. They generally show a linear response to increasing dose. Different types of EPIDs have been clinically implemented, and these have been described in several review papers. The current generation of commercially available EPIDs are indirect detection active matrix flat panel imagers, also known as amorphous silicon (a-Si) EPIDs. Disadvantages of a-Si EPIDs for dosimetry include non-water equivalent construction materials, and the energy sensitivity and optical scatter of the phosphor scintillators used to create optical signal from the megavoltage beam. This report discusses current knowledge regarding a-Si EPIDs for dosimetry.

  16. Advanced Millimeter-Wave Security Portal Imaging Techniques

    SciTech Connect

    Sheen, David M.; Bernacki, Bruce E.; McMakin, Douglas L.

    2012-04-01

    Millimeter-wave imaging is rapidly gaining acceptance for passenger screening at airports and other secured facilities. This paper details a number of techniques developed over the last several years including novel image reconstruction and display techniques, polarimetric imaging techniques, array switching schemes, as well as high frequency high bandwidth techniques. Implementation of some of these methods will increase the cost and complexity of the mm-wave security portal imaging systems. RF photonic methods may provide new solutions to the design and development of the sequentially switched linear mm-wave arrays that are the key element in the mm-wave portal imaging systems.

  17. Monte Carlo simulation of the transit dosimetric response of an a-Si electronic portal imaging device

    NASA Astrophysics Data System (ADS)

    Blake, S. J.; McNamara, A. L.; Vial, P.; Holloway, L.; Greer, P. B.; Kuncic, Z.

    2014-03-01

    Amorphous silicon (a-Si) electronic portal imaging devices (EPIDs) are x-ray detectors frequently used in radiotherapy imaging and dosimetry applications. EPIDs employ a copper plate and gadolinium oxysulfide phosphor screen with an array of a-Si photodiodes to indirectly detect incident radiation. In this study, a previously developed Monte Carlo (MC) model of an a-Si EPID has been extended for transit dosimetry. The GEANT4 MC toolkit was used to integrate an a-Si EPID model with two phantoms and a 6 MV x-ray source. A solid water phantom was used to simulate EPID transmission factors, field size output factors and relative dose profiles and results were compared to experimental measurements. An anthropomorphic head phantom was used to qualitatively compare simulated and measured portal images of humanoid anatomy. Calculated transmission factors and field size output factors agreed to within 2.0% and 1.9% of experimental measurements, respectively. A comparison of calculated and measured relative dose profiles yielded >98% of points passing a gamma analysis with 3%/3 mm criterion for all field sizes. The simulated anthropomorphic head phantom image shows macroscopic anatomical features and qualitatively agrees with the measured image. Results validate the suitability of the MC model for predicting EPID response in transit dosimetry.

  18. Iterative 2D deconvolution of portal imaging radiographs.

    PubMed

    Looe, Hui Khee; Harder, Dietrich; Willborn, Kay C; Poppe, Björn

    2011-01-01

    Portal imaging has become an integral part of modern radiotherapy techniques such as IMRT and IGRT. It serves to verify the accuracy of day-to-day patient positioning, a prerequisite for treatment success. However, image blurring attributable to different physical and geometrical effects, analysed in this work, impairs the image quality of the portal images, and anatomical structures cannot always be clearly outlined. A 2D iterative deconvolution method was developed to reduce this image blurring. The affiliated data basis was generated by the separate measurement of the components contributing to image blurring. Secondary electron transport and pixel size within the EPID, as well as geometrical penumbra due to the finite photon source size were found to be the major contributors, whereas photon scattering in the patient is less important. The underlying line-spread kernels of these components were shown to be Lorentz functions. This implies that each of these convolution kernels and also their combination can be characterized by a single characteristic, the width parameter λ of the Lorentz function. The overall resulting λ values were 0.5mm for 6 MV and 0.65 mm for 15 MV. Portal images were deconvolved using the point-spread function derived from the Lorentz function together with the experimentally determined λ values. The improvement of the portal images was quantified in terms of the modulation transfer function of a bar pattern. The resulting clinical images show a clear enhancement of sharpness and contrast.

  19. Quality assurance of electron beams using a Varian electronic portal imaging device

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Heaton, R.; Norrlinger, B.; Islam, M.

    2013-08-01

    The feasibility of utilizing an electronic portal imaging device (EPID) for the quality assurance of electron beams was investigated. This work was conducted on a Varian 2100iX machine equipped with an amorphous silicon (aS1000) portal imager. The linearity of the imager pixel response as a function of exposed dose was first confirmed. The short-term reproducibility of the EPID response to electron beams was verified. Low (6 MeV), medium (12 MeV) and high (20 MeV) energies were tested, each along with small (6 × 6 cm2), medium (10 × 10 cm2) and large (20 × 20 cm2) applicators. Acquired EPID images were analyzed using an in-house MATLAB code for radiation field size, penumbra, symmetry and flatness. Field sizes and penumbra values agreed with those from film dosimetry to within 1 mm. Field symmetry and flatness constancies were measured over a period of three weeks. The results indicate that EPID can be used for routine quality assurance of electron beams.

  20. SU-E-T-582: On-Line Dosimetric Verification of Respiratory Gated Volumetric Modulated Arc Therapy Using the Electronic Portal Imaging Device

    SciTech Connect

    Schaly, B; Gaede, S; Xhaferllari, I

    2015-06-15

    Purpose: To investigate the clinical utility of on-line verification of respiratory gated VMAT dosimetry during treatment. Methods: Portal dose images were acquired during treatment in integrated mode on a Varian TrueBeam (v. 1.6) linear accelerator for gated lung and liver patients that used flattening filtered beams. The source to imager distance (SID) was set to 160 cm to ensure imager clearance in case the isocenter was off midline. Note that acquisition of integrated images resulted in no extra dose to the patient. Fraction 1 was taken as baseline and all portal dose images were compared to that of the baseline, where the gamma comparison and dose difference were used to measure day-to-day exit dose variation. All images were analyzed in the Portal Dosimetry module of Aria (v. 10). The portal imager on the TrueBeam was calibrated by following the instructions for dosimetry calibration in service mode, where we define 1 calibrated unit (CU) equal to 1 Gy for 10×10 cm field size at 100 cm SID. This reference condition was measured frequently to verify imager calibration. Results: The gamma value (3%, 3 mm, 5% threshold) ranged between 92% and 100% for the lung and liver cases studied. The exit dose can vary by as much as 10% of the maximum dose for an individual fraction. The integrated images combined with the information given by the corresponding on-line soft tissue matched cone-beam computed tomography (CBCT) images were useful in explaining dose variation. For gated lung treatment, dose variation was mainly due to the diaphragm position. For gated liver treatment, the dose variation was due to both diaphragm position and weight loss. Conclusion: Integrated images can be useful in verifying dose delivery consistency during respiratory gated VMAT, although the CBCT information is needed to explain dose differences due to anatomical changes.

  1. Optimisation of the imaging and dosimetric characteristics of an electronic portal imaging device employing plastic scintillating fibres using Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Blake, S. J.; McNamara, A. L.; Vial, P.; Holloway, L.; Kuncic, Z.

    2014-11-01

    A Monte Carlo model of a novel electronic portal imaging device (EPID) has been developed using Geant4 and its performance for imaging and dosimetry applications in radiotherapy has been characterised. The EPID geometry is based on a physical prototype under ongoing investigation and comprises an array of plastic scintillating fibres in place of the metal plate/phosphor screen in standard EPIDs. Geometrical and optical transport parameters were varied to investigate their impact on imaging and dosimetry performance. Detection efficiency was most sensitive to variations in fibre length, achieving a peak value of 36% at 50 mm using 400 keV x-rays for the lengths considered. Increases in efficiency for longer fibres were partially offset by reductions in sensitivity. Removing the extra-mural absorber surrounding individual fibres severely decreased the modulation transfer function (MTF), highlighting its importance in maximising spatial resolution. Field size response and relative dose profile simulations demonstrated a water-equivalent dose response and thus the prototype’s suitability for dosimetry applications. Element-to-element mismatch between scintillating fibres and underlying photodiode pixels resulted in a reduced MTF for high spatial frequencies and quasi-periodic variations in dose profile response. This effect is eliminated when fibres are precisely matched to underlying pixels. Simulations strongly suggest that with further optimisation, this prototype EPID may be capable of simultaneous imaging and dosimetry in radiotherapy.

  2. An electronic portal imaging device as a physics tool.

    PubMed

    Curtin-Savard, A; Podgorsak, E B

    1997-01-01

    An electronic portal imaging device (EPID) can be used not only to acquire megavoltage patient images but also to measure certain radiation beam parameters of the linear accelerator. EPID images can be used to verify field junctions, center of collimator rotation, or radiation vs. light field coincidence. If the EPID images are calibrated in terms of dose rate, an EPID can be applied to beam penumbra measurement, collimator transmission determination, or compensator verification. Beam parameters measured with EPIDs are in close agreement with those measured with film or ionization chamber, making EPIDs reliable physics tools for quality control of various beam parameters in radiotherapy. PMID:9243462

  3. Assessment of dosimetrical performance in 11 Varian a-Si500 electronic portal imaging devices

    NASA Astrophysics Data System (ADS)

    Kavuma, Awusi; Glegg, Martin; Currie, Garry; Elliott, Alex

    2008-12-01

    Dosimetrical characteristics of 11 Varian a-Si-500 electronic portal imaging devices (EPIDs) in clinical use for periods ranging between 10 and 86 months were investigated for consistency of performance and portal dosimetry implications. Properties studied include short-term reproducibility, signal linearity with monitor units, response to reference beam, signal uniformity across the detector panel, signal dependence on field size, dose-rate influence, memory effects and image profiles as a function of monitor units. The EPID measurements were also compared with those of the ionization chambers' to ensure stability of the linear accelerators. Depending on their clinical installation date, the EPIDs were interfaced with one of the two different acquisition control software packages, IAS2/IDU-II or IAS3/IDU-20. Both the EPID age and image acquisition system influenced the dosimetric characteristics with the newer version (IAS3 with IDU-20) giving better data reproducibility and linearity fit than the older version (IAS2 with IDU-II). The relative signal response (uniformity) after 50 MU was better than 95% of the central value and independent of detector. Sensitivity for all EPIDs reduced continuously with increasing dose rates for the newer image acquisition software. In the dose-rate range 100-600 MU min-1, the maximum variation in sensitivity ranged between 1 and 1.8% for different EPIDs. For memory effects, the increase in the measured signal at the centre of the irradiated field for successive images was within 1.8% and 1.0% for the older and newer acquisition systems, respectively. Image profiles acquired at a lower MU in the radial plane (gun-target) had gradients in measured pixel values of up to 25% for the older system. Detectors with software/hardware versions IAS3/IDU-20 have a high degree of accuracy and are more suitable for routine quantitative IMRT dosimetrical verification.

  4. Comprehensive fluence model for absolute portal dose image prediction

    SciTech Connect

    Chytyk, K.; McCurdy, B. M. C.

    2009-04-15

    Amorphous silicon (a-Si) electronic portal imaging devices (EPIDs) continue to be investigated as treatment verification tools, with a particular focus on intensity modulated radiation therapy (IMRT). This verification could be accomplished through a comparison of measured portal images to predicted portal dose images. A general fluence determination tailored to portal dose image prediction would be a great asset in order to model the complex modulation of IMRT. A proposed physics-based parameter fluence model was commissioned by matching predicted EPID images to corresponding measured EPID images of multileaf collimator (MLC) defined fields. The two-source fluence model was composed of a focal Gaussian and an extrafocal Gaussian-like source. Specific aspects of the MLC and secondary collimators were also modeled (e.g., jaw and MLC transmission factors, MLC rounded leaf tips, tongue and groove effect, interleaf leakage, and leaf offsets). Several unique aspects of the model were developed based on the results of detailed Monte Carlo simulations of the linear accelerator including (1) use of a non-Gaussian extrafocal fluence source function, (2) separate energy spectra used for focal and extrafocal fluence, and (3) different off-axis energy spectra softening used for focal and extrafocal fluences. The predicted energy fluence was then convolved with Monte Carlo generated, EPID-specific dose kernels to convert incident fluence to dose delivered to the EPID. Measured EPID data were obtained with an a-Si EPID for various MLC-defined fields (from 1x1 to 20x20 cm{sup 2}) over a range of source-to-detector distances. These measured profiles were used to determine the fluence model parameters in a process analogous to the commissioning of a treatment planning system. The resulting model was tested on 20 clinical IMRT plans, including ten prostate and ten oropharyngeal cases. The model predicted the open-field profiles within 2%, 2 mm, while a mean of 96.6% of pixels over

  5. Phase contrast portal imaging for image-guided microbeam radiation therapy

    NASA Astrophysics Data System (ADS)

    Umetani, Keiji; Kondoh, Takeshi

    2014-03-01

    High-dose synchrotron microbeam radiation therapy is a unique treatment technique used to destroy tumors without severely affecting circumjacent healthy tissue. We applied a phase contrast technique to portal imaging in preclinical microbeam radiation therapy experiments. Phase contrast portal imaging is expected to enable us to obtain higherresolution X-ray images at therapeutic X-ray energies compared to conventional portal imaging. Frontal view images of a mouse head sample were acquired in propagation-based phase contrast imaging. The phase contrast images depicted edge-enhanced fine structures of the parietal bones surrounding the cerebrum. The phase contrast technique is expected to be effective in bony-landmark-based verification for image-guided radiation therapy.

  6. Advanced millimeter-wave security portal imaging techniques

    NASA Astrophysics Data System (ADS)

    Sheen, David M.; Bernacki, Bruce E.; McMakin, Douglas L.

    2012-03-01

    Millimeter-wave (mm-wave) imaging is rapidly gaining acceptance as a security tool to augment conventional metal detectors and baggage x-ray systems for passenger screening at airports and other secured facilities. This acceptance indicates that the technology has matured; however, many potential improvements can yet be realized. The authors have developed a number of techniques over the last several years including novel image reconstruction and display techniques, polarimetric imaging techniques, array switching schemes, and high-frequency high-bandwidth techniques. All of these may improve the performance of new systems; however, some of these techniques will increase the cost and complexity of the mm-wave security portal imaging systems. Reducing this cost may require the development of novel array designs. In particular, RF photonic methods may provide new solutions to the design and development of the sequentially switched linear mm-wave arrays that are the key element in the mm-wave portal imaging systems. Highfrequency, high-bandwidth designs are difficult to achieve with conventional mm-wave electronic devices, and RF photonic devices may be a practical alternative. In this paper, the mm-wave imaging techniques developed at PNNL are reviewed and the potential for implementing RF photonic mm-wave array designs is explored.

  7. SU-F-BRE-13: Replacing Pre-Treatment Phantom QA with 3D In-Vivo Portal Dosimetry for IMRT Breast Cancer

    SciTech Connect

    Stroom, J; Vieira, S; Greco, C; Olaciregui-Ruiz, I; Rozendaal, R; Herk, M van; Moser, E

    2014-06-15

    Purpose: Pre-treatment QA of individual treatment plans requires costly linac time and physics effort. Starting with IMRT breast treatments, we aim to replace pre-treatment QA with in-vivo portal dosimetry. Methods: Our IMRT breast cancer plans are routinely measured using the ArcCheck device (SunNuclear). 2D-Gamma analysis is performed with 3%/3mm criteria and the percentage of points with gamma<1 (nG1) is calculated within the 50% isodose surface. Following AAPM recommendations, plans with nG1<90% are approved; others need further inspection and might be rejected. For this study, we used invivo portal dosimetry (IPD) to measure the 3D back-projected dose of the first three fractions for IMRT breast plans. Patient setup was online corrected before for all measured fractions. To reduce patient related uncertainties, the three IPD results were averaged and 3D-gamma analysis was applied with abovementioned criteria . For a subset of patients, phantom portal dosimetry (PPD) was also performed on a slab phantom. Results: Forty consecutive breast patients with plans that fitted the EPID were analysed. The average difference between planned and IPD dose in the reference point was −0.7+/−1.6% (1SD). Variation in nG1 between the 3 invivo fractions was about 6% (1SD). The average nG1 for IPD was 89+/−6%, worse than ArcCheck (95+/−3%). This can be explained by patient related factors such as changes in anatomy and/or model deficiencies due to e.g. inhomogeneities. For the 20 cases with PPD, mean nG1 was equal to ArcCheck values, which indicates that the two systems are equally accurate. These data therefore suggest that proper criteria for 3D invivo verification of breast treatments should be nG1>80% instead of nG1>90%, which, for our breast cases, would result in 5% (2/40) further inspections. Conclusion: First-fraction in-vivo portal dosimetry using new gamma-evaluation criteria will replace phantom measurements in our institution, saving resources and yielding 3D

  8. [MLC positioning checks and calibration with a portal imaging system].

    PubMed

    Schiefer, Hans; Seelentag, Wolf W; Roth, Jakob; Krusche, Bernd

    2008-01-01

    For checking the leaf positions of a MLC (Multi Leaf Collimator) images are acquired with an EPID (Electronic Portal Imaging Device) and then evaluated with a programme (MLC check) developed in-house. During image acquisition a Perspex tray with two metal markers of known position (in the radiation field) is inserted in the satellite tray holder. After determination of the marker positions within the image coordinate system, the image can be transformed to the radiation field coordinate system. This allows the exact determination of the leaf tip positions relative to the radiation field. This evaluation can be applied to images of arbitrary field shapes, provided they were acquired in the same geometry (EPID position, gantry and collimator angles). The entire measurement procedure is based on images in bmp (Windows Bitmap) format, with a 1024 x 1024 matrix and a pixel depth of 24 bit (8 bit per color channel). A suitable marker plate can be manufactured without sophisticated workload; thus the method may be easily and cost effectively adapted at other locations.

  9. Hybrid Imaging for Patient-Specific Dosimetry in Radionuclide Therapy.

    PubMed

    Ljungberg, Michael; Gleisner, Katarina Sjögreen

    2015-01-01

    Radionuclide therapy aims to treat malignant diseases by systemic administration of radiopharmaceuticals, often using carrier molecules such as peptides and antibodies. The radionuclides used emit electrons or alpha particles as a consequence of radioactive decay, thus leading to local energy deposition. Administration to individual patients can be tailored with regards to the risk of toxicity in normal organs by using absorbed dose planning. The scintillation camera, employed in planar imaging or single-photon emission computed tomography (SPECT), generates images of the spatially and temporally varying activity distribution. Recent commercially available combined SPECT and computed tomography (CT) systems have dramatically increased the possibility of performing accurate dose planning by using the CT information in several steps of the dose-planning calculation chain. This paper discusses the dosimetry chain used for individual absorbed-dose planning and highlights the areas where hybrid imaging makes significant contributions. PMID:26854156

  10. Use of electronic portal imaging devices for electron treatment verification.

    PubMed

    Kairn, T; Aland, T; Crowe, S B; Trapp, J V

    2016-03-01

    This study aims to help broaden the use of electronic portal imaging devices (EPIDs) for pre-treatment patient positioning verification, from photon-beam radiotherapy to photon- and electron-beam radiotherapy, by proposing and testing a method for acquiring clinically-useful EPID images of patient anatomy using electron beams, with a view to enabling and encouraging further research in this area. EPID images used in this study were acquired using all available beams from a linac configured to deliver electron beams with nominal energies of 6, 9, 12, 16 and 20 MeV, as well as photon beams with nominal energies of 6 and 10 MV. A widely-available heterogeneous, approximately-humanoid, thorax phantom was used, to provide an indication of the contrast and noise produced when imaging different types of tissue with comparatively realistic thicknesses. The acquired images were automatically calibrated, corrected for the effects of variations in the sensitivity of individual photodiodes, using a flood field image. For electron beam imaging, flood field EPID calibration images were acquired with and without the placement of blocks of water-equivalent plastic (with thicknesses approximately equal to the practical range of electrons in the plastic) placed upstream of the EPID, to filter out the primary electron beam, leaving only the bremsstrahlung photon signal. While the electron beam images acquired using a standard (unfiltered) flood field calibration were observed to be noisy and difficult to interpret, the electron beam images acquired using the filtered flood field calibration showed tissues and bony anatomy with levels of contrast and noise that were similar to the contrast and noise levels seen in the clinically acceptable photon beam EPID images. The best electron beam imaging results (highest contrast, signal-to-noise and contrast-to-noise ratios) were achieved when the images were acquired using the higher energy electron beams (16 and 20 MeV) when the EPID was

  11. Evaluation of relative transmitted dose for a step and shoot head and neck intensity modulated radiation therapy using a scanning liquid ionization chamber electronic portal imaging device

    PubMed Central

    Mohammadi, Mohammad; Bezak, Eva

    2012-01-01

    The dose delivery verification for a head and neck static intensity modulated radiation therapy (IMRT) case using a scanning liquid ionization chamber electronic portal imaging device (SLIC-EPID) was investigated. Acquired electronic portal images were firstly converted into transmitted dose maps using an in-house developed method. The dose distributions were then compared with those calculated in a virtual EPID using the Pinnacle3 treatment planning system (TPS). Using gamma evaluation with the ΔDmax and DTA criteria of 3%/2.54 mm, an excellent agreement was observed between transmitted dose measured using SLIC-EPID and that calculated by TPS (gamma score approximately 95%) for large MLC fields. In contrast, for several small subfields, due to SLIC-EPID image blurring, significant disagreement was found in the gamma results. Differences between EPID and TPS dose maps were also observed for several parts of the radiation subfields, when the radiation beam passed through air on the outside of tissue. The transmitted dose distributions measured using portal imagers such as SLIC-EPID can be used to verify the dose delivery to a patient. However, several aspects such as accurate calibration procedure and imager response under different conditions should be taken into the consideration. In addition, SLIC-EPID image blurring is another important issue, which should be considered if the SLIC-EPID is used for clinical dosimetry verification. PMID:22363108

  12. Evaluation of relative transmitted dose for a step and shoot head and neck intensity modulated radiation therapy using a scanning liquid ionization chamber electronic portal imaging device.

    PubMed

    Mohammadi, Mohammad; Bezak, Eva

    2012-01-01

    The dose delivery verification for a head and neck static intensity modulated radiation therapy (IMRT) case using a scanning liquid ionization chamber electronic portal imaging device (SLIC-EPID) was investigated. Acquired electronic portal images were firstly converted into transmitted dose maps using an in-house developed method. The dose distributions were then compared with those calculated in a virtual EPID using the Pinnacle(3) treatment planning system (TPS). Using gamma evaluation with the ΔD(max) and DTA criteria of 3%/2.54 mm, an excellent agreement was observed between transmitted dose measured using SLIC-EPID and that calculated by TPS (gamma score approximately 95%) for large MLC fields. In contrast, for several small subfields, due to SLIC-EPID image blurring, significant disagreement was found in the gamma results. Differences between EPID and TPS dose maps were also observed for several parts of the radiation subfields, when the radiation beam passed through air on the outside of tissue. The transmitted dose distributions measured using portal imagers such as SLIC-EPID can be used to verify the dose delivery to a patient. However, several aspects such as accurate calibration procedure and imager response under different conditions should be taken into the consideration. In addition, SLIC-EPID image blurring is another important issue, which should be considered if the SLIC-EPID is used for clinical dosimetry verification.

  13. Tracking moving objects with megavoltage portal imaging: A feasibility study

    SciTech Connect

    Meyer, Juergen; Richter, Anne; Baier, Kurt; Wilbert, Juergen; Guckenberger, Matthias; Flentje, Michael

    2006-05-15

    Four different algorithms were investigated with the aim to determine their suitability to track an object in conventional megavoltage portal images. The algorithms considered were the mean of the sum of squared differences (MSSD), mutual information (MI), the correlation ratio (CR), and the correlation coefficient (CC). Simulation studies were carried out with various image series containing a rigid object of interest that was moved along a predefined trajectory. For each of the series the signal-to-noise ratio (SNR) was varied to compare the performance of the algorithms under noisy conditions. For a poor SNR of -6 dB the mean tracking error was 2.4, 6.5, 39.0, and 17.2 pixels for MSSD, CC, CR and MI, respectively, with a standard deviation of 1.9, 12.9, 19.5, and 7.5 pixels, respectively. The size of a pixel was 0.5 mm. These results improved to 1.1, 1.3, 1.3, and 2.0 pixels, respectively, with a standard deviation of 0.6, 0.8, 0.8, and 2.1 pixels, respectively, when a mean filter was applied to the images prior to tracking. The implementation of MSSD into existing in-house software demonstrated that, depending on the search range, it was possible to process between 2 and 15 images/s, making this approach capable of real-time applications. In conclusion, the best geometric tracking accuracy overall was obtained with MSSD, followed by CC, CR, and MI. The simplest and best algorithm, both in terms of geometric accuracy as well as computational cost, was the MSSD algorithm and was therefore the method of choice.

  14. SU-E-J-15: Automatically Detect Patient Treatment Position and Orientation in KV Portal Images

    SciTech Connect

    Qiu, J; Yang, D

    2015-06-15

    Purpose: In the course of radiation therapy, the complex information processing workflow will Result in potential errors, such as incorrect or inaccurate patient setups. With automatic image check and patient identification, such errors could be effectively reduced. For this purpose, we developed a simple and rapid image processing method, to automatically detect the patient position and orientation in 2D portal images, so to allow automatic check of positions and orientations for patient daily RT treatments. Methods: Based on the principle of portal image formation, a set of whole body DRR images were reconstructed from multiple whole body CT volume datasets, and fused together to be used as the matching template. To identify the patient setup position and orientation shown in a 2D portal image, the 2D portal image was preprocessed (contrast enhancement, down-sampling and couch table detection), then matched to the template image so to identify the laterality (left or right), position, orientation and treatment site. Results: Five day’s clinical qualified portal images were gathered randomly, then were processed by the automatic detection and matching method without any additional information. The detection results were visually checked by physicists. 182 images were correct detection in a total of 200kV portal images. The correct rate was 91%. Conclusion: The proposed method can detect patient setup and orientation quickly and automatically. It only requires the image intensity information in KV portal images. This method can be useful in the framework of Electronic Chart Check (ECCK) to reduce the potential errors in workflow of radiation therapy and so to improve patient safety. In addition, the auto-detection results, as the patient treatment site position and patient orientation, could be useful to guide the sequential image processing procedures, e.g. verification of patient daily setup accuracy. This work was partially supported by research grant from

  15. Comparison of the performance between portal dosimetry and a commercial two-dimensional array system on pretreatment quality assurance for volumetric-modulated arc and intensity-modulated radiation therapy

    NASA Astrophysics Data System (ADS)

    Kim, Yon-Lae; Chung, Jin-Beom; Kim, Jae-Sung; Lee, Jeong-Woo; Choi, Kyoung-Sik

    2014-04-01

    The aim of this study was to compare the dosimetric performance and to evaluate the pretreatment quality assurance (QA) of a portal dosimetry and a commercial two-dimensional (2-D) array system. In the characteristics comparison study, the measured values for the dose linearity, dose rate response, reproducibility, and field size dependence for 6-MV photon beams were analyzed for both detector systems. To perform the qualitative evaluations of the 10 IMRT and the 10 VMAT plans, we used the Gamma index for quantifying the agreement between calculations and measurements. The performance estimates for both systems show that overall, minimal differences in the dosimetric characteristics exist between the Electron portal imaging device (EPID) and 2-D array system. In the qualitative analysis for pretreatment quality assurance, the EPID and 2-D array system yield similar passing rate results for the majority of clinical Intensity-modulated radiation therapy (IMRT) and Volumetric-modulated arc therapy (VMAT) cases. These results were satisfactory for IMRT and VMAT fields and were within the acceptable criteria of γ%≤1, γ avg <0.5. The EPDI and the 2-D array systems showed comparable dosimetric results. In this study, the results revealed both systems to be suitable for patient-specific QA measurements for IMRT and VMAT. We conclude that, depending on the status of clinic, both systems can be used interchangeably for routine pretreatment QA.

  16. Quantitative 3D Optical Imaging: Applications in Dosimetry and Biophysics

    NASA Astrophysics Data System (ADS)

    Thomas, Andrew Stephen

    Optical-CT has been shown to be a potentially useful imaging tool for the two very different spheres of biologists and radiation therapy physicists, but it has yet to live up to that potential. In radiation therapy, researchers have used optical-CT for the readout of 3D dosimeters, but it is yet to be a clinically relevant tool as the technology is too slow to be considered practical. Biologists have used the technique for structural imaging, but have struggled with emission tomography as the reality of photon attenuation for both excitation and emission have made the images quantitatively irrelevant. Dosimetry. The DLOS (Duke Large field of view Optical-CT Scanner) was designed and constructed to make 3D dosimetry utilizing optical-CT a fast and practical tool while maintaining the accuracy of readout of the previous, slower readout technologies. Upon construction/optimization/implementation of several components including a diffuser, band pass filter, registration mount & fluid filtration system the dosimetry system provides high quality data comparable to or exceeding that of commercial products. In addition, a stray light correction algorithm was tested and implemented. The DLOS in combination with the 3D dosimeter it was designed for, PREAGETM, then underwent rigorous commissioning and benchmarking tests validating its performance against gold standard data including a set of 6 irradiations. DLOS commissioning tests resulted in sub-mm isotropic spatial resolution (MTF >0.5 for frequencies of 1.5lp/mm) and a dynamic range of ˜60dB. Flood field uniformity was 10% and stable after 45minutes. Stray light proved to be small, due to telecentricity, but even the residual can be removed through deconvolution. Benchmarking tests showed the mean 3D passing gamma rate (3%, 3mm, 5% dose threshold) over the 6 benchmark data sets was 97.3% +/- 0.6% (range 96%-98%) scans totaling ˜10 minutes, indicating excellent ability to perform 3D dosimetry while improving the speed of

  17. Evaluation of an aSi-EPID with flattening filter free beams: Applicability to the GLAaS algorithm for portal dosimetry and first experience for pretreatment QA of RapidArc

    SciTech Connect

    Nicolini, G.; Clivio, A.; Vanetti, E.; Cozzi, L.; Fogliata, A.; Krauss, H.; Fenoglietto, P.

    2013-11-15

    Purpose: To demonstrate the feasibility of portal dosimetry with an amorphous silicon mega voltage imager for flattening filter free (FFF) photon beams by means of the GLAaS methodology and to validate it for pretreatment quality assurance of volumetric modulated arc therapy (RapidArc).Methods: The GLAaS algorithm, developed for flattened beams, was applied to FFF beams of nominal energy of 6 and 10 MV generated by a Varian TrueBeam (TB). The amorphous silicon electronic portal imager [named mega voltage imager (MVI) on TB] was used to generate integrated images that were converted into matrices of absorbed dose to water. To enable GLAaS use under the increased dose-per-pulse and dose-rate conditions of the FFF beams, new operational source-detector-distance (SDD) was identified to solve detector saturation issues. Empirical corrections were defined to account for the shape of the profiles of the FFF beams to expand the original methodology of beam profile and arm backscattering correction. GLAaS for FFF beams was validated on pretreatment verification of RapidArc plans for three different TB linacs. In addition, the first pretreatment results from clinical experience on 74 arcs were reported in terms of γ analysis.Results: MVI saturates at 100 cm SDD for FFF beams but this can be avoided if images are acquired at 150 cm for all nominal dose rates of FFF beams. Rotational stability of the gantry-imager system was tested and resulted in a minimal apparent imager displacement during rotation of 0.2 ± 0.2 mm at SDD = 150 cm. The accuracy of this approach was tested with three different Varian TrueBeam linacs from different institutes. Data were stratified per energy and machine and showed no dependence with beam quality and MLC model. The results from clinical pretreatment quality assurance, provided a gamma agreement index (GAI) in the field area for six and ten FFF beams of (99.8 ± 0.3)% and (99.5 ± 0.6)% with distance to agreement and dose difference criteria

  18. Analytical scatter kernels for portal imaging at 6 MV.

    PubMed

    Spies, L; Bortfeld, T

    2001-04-01

    X-ray photon scatter kernels for 6 MV electronic portal imaging are investigated using an analytical and a semi-analytical model. The models are tested on homogeneous phantoms for a range of uniform circular fields and scatterer-to-detector air gaps relevant for clinical use. It is found that a fully analytical model based on an exact treatment of photons undergoing a single Compton scatter event and an approximate treatment of second and higher order scatter events, assuming a multiple-scatter source at the center of the scatter volume, is accurate within 1% (i.e., the residual scatter signal is less than 1% of the primary signal) for field sizes up to 100 cm2 and air gaps over 30 cm, but shows significant discrepancies for larger field sizes. Monte Carlo results are presented showing that the effective multiple-scatter source is located toward the exit surface of the scatterer, rather than at its center. A second model is therefore investigated where second and higher-order scattering is instead modeled by fitting an analytical function describing a nonstationary isotropic point-scatter source to Monte Carlo generated data. This second model is shown to be accurate to within 1% for air gaps down to 20 cm, for field sizes up to 900 cm2 and phantom thicknesses up to 50 cm. PMID:11339752

  19. SILICON PHOTOMULTIPLIERS FOR MEDICAL IMAGING AND DOSIMETRY-AN OVERVIEW.

    PubMed

    Herrnsdorf, L; Caccia, M; Mattsson, S

    2016-06-01

    Silicon photomultipliers (SiPMs) are an enabling solid-state technology for low light sensing, with single photon sensitivity and photon number resolving capability. They feature an extremely high internal gain at the 10(6) level, comparable to photomultiplier tubes (PMTs), with the advantage of low operating voltage (~50 V compared to ~1000 V for PMT) and low energy consumption. The solid-state technology makes SiPMs compact, insensitive to magnetic fields and with an extreme flexibility in the design to cope with different applications. The fast development of the multiplication avalanche opens up the possibility to achieve time resolution at the 30 ps level. Dynamic range is however limited compared to PMT and the dark count rate relatively high, yet today at the level of 50 kHz/mm(2) at room temperature. Interfaced with scintillation material, SiPMs provide a powerful platform for medical imaging applications (in positron emission tomography/computed tomography and in positron emission tomography/magnetic resonance), for X-ray quality control as well as for novel compact radiation protection instruments. This article gives an overview of SiPMs for medical imaging and dosimetry. In addition, a learning and training program targeted to graduate students is described. PMID:27103639

  20. Standard Imaging Techniques for Assessment of Portal Venous System and its Tributaries by Linear Endoscopic Ultrasound: A Pictorial Essay

    PubMed Central

    Rameshbabu, C. S.; Wani, Zeeshn Ahamad; Rai, Praveer; Abdulqader, Almessabi; Garg, Shubham; Sharma, Malay

    2013-01-01

    Linear Endosonography has been used to image the Portal Venous System but no established standard guidelines exist. This article presents techniques to visualize the portal venous system and its tributaries by linear endosonography. Attempt has been made to show most of the first order tributaries and some second order tributaries of splenic vein, superior mesenteric vein and portal vein. PMID:24949362

  1. Dosimetry in x-ray-based breast imaging

    NASA Astrophysics Data System (ADS)

    Dance, David R.; Sechopoulos, Ioannis

    2016-10-01

    The estimation of the mean glandular dose to the breast (MGD) for x-ray based imaging modalities forms an essential part of quality control and is needed for risk estimation and for system design and optimisation. This review considers the development of methods for estimating the MGD for mammography, digital breast tomosynthesis (DBT) and dedicated breast CT (DBCT). Almost all of the methodology used employs Monte Carlo calculated conversion factors to relate the measurable quantity, generally the incident air kerma, to the MGD. After a review of the size and composition of the female breast, the various mathematical models used are discussed, with particular emphasis on models for mammography. These range from simple geometrical shapes, to the more recent complex models based on patient DBCT examinations. The possibility of patient-specific dose estimates is considered as well as special diagnostic views and the effect of breast implants. Calculations using the complex models show that the MGD for mammography is overestimated by about 30% when the simple models are used. The design and uses of breast-simulating test phantoms for measuring incident air kerma are outlined and comparisons made between patient and phantom-based dose estimates. The most widely used national and international dosimetry protocols for mammography are based on different simple geometrical models of the breast, and harmonisation of these protocols using more complex breast models is desirable.

  2. A new silicon tracker for proton imaging and dosimetry

    NASA Astrophysics Data System (ADS)

    Taylor, J. T.; Waltham, C.; Price, T.; Allinson, N. M.; Allport, P. P.; Casse, G. L.; Kacperek, A.; Manger, S.; Smith, N. A.; Tsurin, I.

    2016-09-01

    For many years, silicon micro-strip detectors have been successfully used as tracking detectors for particle and nuclear physics experiments. A new application of this technology is to the field of particle therapy where radiotherapy is carried out by use of charged particles such as protons or carbon ions. Such a treatment has been shown to have advantages over standard x-ray radiotherapy and as a result of this, many new centres offering particle therapy are currently under construction around the world today. The Proton Radiotherapy, Verification and Dosimetry Applications (PRaVDA) consortium are developing instrumentation for particle therapy based upon technology from high-energy physics. The characteristics of a new silicon micro-strip tracker for particle therapy will be presented. The array uses specifically designed, large area sensors with technology choices that follow closely those taken for the ATLAS experiment at the HL-LHC. These detectors will be arranged into four units each with three layers in an x-u-v configuration to be suitable for fast proton tracking with minimal ambiguities. The sensors will form a tracker capable of tracing the path of ~200 MeV protons entering and exiting a patient allowing a new mode of imaging known as proton computed tomography (pCT). This will aid the accurate delivery of treatment doses and in addition, the tracker will also be used to monitor the beam profile and total dose delivered during the high fluences used for treatment. We present here details of the design, construction and assembly of one of the four units that will make up the complete tracker along with its characterisation using radiation tests carried out using a 90Sr source in the laboratory and a 60 MeV proton beam at the Clatterbridge Cancer Centre.

  3. A region-based Retinex with data filling for the enhancement of electronic portal images

    NASA Astrophysics Data System (ADS)

    Chen, Yuan-Po; Yeh, Shyh-An; Huang, Yung-Hui; Chang, Li-Yun; Kuo, Chung-Ming; Ding, Hueisch-Jy

    2013-05-01

    PurposePortal images are acquired by electronic portal imaging devices (EPID) with megavoltage (MV) x-ray, but they are inherently poor in terms of contrast, due to Compton Effect. In comparison with diagnostic x-ray images, portal images usually lack sufficient detail information for normal human vision. Therefore, an effective method of enhancing these images would be very useful. This paper proposes a new approach that combines global and local enhancement techniques. Materials and methodsA portal image usually has a high dynamic range (HDR) of up to 16 bits, so it could records details that are imperceptible to the naked eye. However, this property provides the potential for enhancement of the portal image. In order to overcome the low contrast appearance caused by innate physical properties, two phases and four sequential steps were proposed. At phase 1, global enhancement, HE is used to stretch narrow range histogram of original raw image to reasonable wide range so that we can easily partition the image into regions for local enhancement. At phase 2, local enhancement, EPIs were first segmented into regions based on histogram distribution. Then a new concept of local enhancement, pseudo-data filling, in which enhancement is controlled by manipulating the pseudo-data, is proposed in order to maximize the regional enhancement. Finally each region of EPI is enhanced by Retinex with optimized parameter and synthesized as output image. ResultsAt phase 1, HE can successfully improve EPIs contrast at varies body sites by redistribution histogram. This step provides possibility of histogram analyzing at phase 2. Therefore, histogram-based segmentation is feasible for nearly every patient as we expected. Simulation of pseudo-data filling and region-based Retinex enhancement demonstrate that the proposed method provides a more detailed portal image, which is proved by objective evaluation of two groups of radiation oncology staffs. ConclusionsAn effective enhancement

  4. Dose reconstruction for intensity-modulated radiation therapy using a non-iterative method and portal dose image

    NASA Astrophysics Data System (ADS)

    Yeo, Inhwan Jason; Jung, Jae Won; Chew, Meng; Kim, Jong Oh; Wang, Brian; Di Biase, Steven; Zhu, Yunping; Lee, Dohyung

    2009-09-01

    A straightforward and accurate method was developed to verify the delivery of intensity-modulated radiation therapy (IMRT) and to reconstruct the dose in a patient. The method is based on a computational algorithm that linearly describes the physical relationship between beamlets and dose-scoring voxels in a patient and the dose image from an electronic portal imaging device (EPID). The relationship is expressed in the form of dose response functions (responses) that are quantified using Monte Carlo (MC) particle transport techniques. From the dose information measured by the EPID the received patient dose is reconstructed by inversely solving the algorithm. The unique and novel non-iterative feature of this algorithm sets it apart from many existing dose reconstruction methods in the literature. This study presents the algorithm in detail and validates it experimentally for open and IMRT fields. Responses were first calculated for each beamlet of the selected fields by MC simulation. In-phantom and exit film dosimetry were performed on a flat phantom. Using the calculated responses and the algorithm, the exit film dose was used to inversely reconstruct the in-phantom dose, which was then compared with the measured in-phantom dose. The dose comparison in the phantom for all irradiated fields showed a pass rate of higher than 90% dose points given the criteria of dose difference of 3% and distance to agreement of 3 mm.

  5. Level-set segmentation of pulmonary nodules in megavolt electronic portal images using a CT prior

    SciTech Connect

    Schildkraut, J. S.; Prosser, N.; Savakis, A.; Gomez, J.; Nazareth, D.; Singh, A. K.; Malhotra, H. K.

    2010-11-15

    Purpose: Pulmonary nodules present unique problems during radiation treatment due to nodule position uncertainty that is caused by respiration. The radiation field has to be enlarged to account for nodule motion during treatment. The purpose of this work is to provide a method of locating a pulmonary nodule in a megavolt portal image that can be used to reduce the internal target volume (ITV) during radiation therapy. A reduction in the ITV would result in a decrease in radiation toxicity to healthy tissue. Methods: Eight patients with nonsmall cell lung cancer were used in this study. CT scans that include the pulmonary nodule were captured with a GE Healthcare LightSpeed RT 16 scanner. Megavolt portal images were acquired with a Varian Trilogy unit equipped with an AS1000 electronic portal imaging device. The nodule localization method uses grayscale morphological filtering and level-set segmentation with a prior. The treatment-time portion of the algorithm is implemented on a graphical processing unit. Results: The method was retrospectively tested on eight cases that include a total of 151 megavolt portal image frames. The method reduced the nodule position uncertainty by an average of 40% for seven out of the eight cases. The treatment phase portion of the method has a subsecond execution time that makes it suitable for near-real-time nodule localization. Conclusions: A method was developed to localize a pulmonary nodule in a megavolt portal image. The method uses the characteristics of the nodule in a prior CT scan to enhance the nodule in the portal image and to identify the nodule region by level-set segmentation. In a retrospective study, the method reduced the nodule position uncertainty by an average of 40% for seven out of the eight cases studied.

  6. The Feasibility of Thermal Imaging as a Future Portal Imaging Device for Therapeutic Ultrasound.

    PubMed

    Miloro, Piero; Civale, John; Rivens, Ian; Shaw, Adam

    2016-08-01

    This technical note describes a prototype thermally based portal imaging device that allows mapping of energy deposition on the surface of a tissue mimicking material in a focused ultrasound surgery (FUS) beam by using an infrared camera to measure the temperature change on that surface. The aim of the work is to explore the feasibility of designing and building a system suitable for rapid quality assurance (QA) for use with both ultrasound- and magnetic resonance (MR) imaging-guided clinical therapy ultrasound systems. The prototype was tested using an MR-guided Sonalleve FUS system (with the treatment couch outside the magnet bore). The system's effective thermal noise was 0.02°C, and temperature changes as low as 0.1°C were easily quantifiable. The advantages and drawbacks of thermal imaging for QA are presented through analysis of the results of an experimental session.

  7. The Feasibility of Thermal Imaging as a Future Portal Imaging Device for Therapeutic Ultrasound.

    PubMed

    Miloro, Piero; Civale, John; Rivens, Ian; Shaw, Adam

    2016-08-01

    This technical note describes a prototype thermally based portal imaging device that allows mapping of energy deposition on the surface of a tissue mimicking material in a focused ultrasound surgery (FUS) beam by using an infrared camera to measure the temperature change on that surface. The aim of the work is to explore the feasibility of designing and building a system suitable for rapid quality assurance (QA) for use with both ultrasound- and magnetic resonance (MR) imaging-guided clinical therapy ultrasound systems. The prototype was tested using an MR-guided Sonalleve FUS system (with the treatment couch outside the magnet bore). The system's effective thermal noise was 0.02°C, and temperature changes as low as 0.1°C were easily quantifiable. The advantages and drawbacks of thermal imaging for QA are presented through analysis of the results of an experimental session. PMID:27174419

  8. Imaging and radiological interventions in extra-hepatic portal vein obstruction

    PubMed Central

    Pargewar, Sudheer S; Desai, Saloni N; Rajesh, S; Singh, Vaibhav P; Arora, Ankur; Mukund, Amar

    2016-01-01

    Extrahepatic portal vein obstruction (EHPVO) is a primary vascular condition characterized by chronic long standing blockage and cavernous transformation of portal vein with or without additional involvement of intrahepatic branches, splenic or superior mesenteric vein. Patients generally present in childhood with multiple episodes of variceal bleed and EHPVO is the predominant cause of paediatric portal hypertension (PHT) in developing countries. It is a pre-hepatic type of PHT in which liver functions and morphology are preserved till late. Characteristic imaging findings include multiple parabiliary venous collaterals which form to bypass the obstructed portal vein with resultant changes in biliary tree termed portal biliopathy or portal cavernoma cholangiopathy. Ultrasound with Doppler, computed tomography, magnetic resonance cholangiography and magnetic resonance portovenography are non-invasive techniques which can provide a comprehensive analysis of degree and extent of EHPVO, collaterals and bile duct abnormalities. These can also be used to assess in surgical planning as well screening for shunt patency in post-operative patients. The multitude of changes and complications seen in EHPVO can be addressed by various radiological interventional procedures. The myriad of symptoms arising secondary to vascular, biliary, visceral and neurocognitive changes in EHPVO can be managed by various radiological interventions like transjugular intra-hepatic portosystemic shunt, percutaneous transhepatic biliary drainage, partial splenic embolization, balloon occluded retrograde obliteration of portosystemic shunt (PSS) and revision of PSS. PMID:27358683

  9. Focal spot motion of linear accelerators and its effect on portal image analysis.

    PubMed

    Sonke, Jan-Jakob; Brand, Bob; van Herk, Marcel

    2003-06-01

    The focal spot of a linear accelerator is often considered to have a fully stable position. In practice, however, the beam control loop of a linear accelerator needs to stabilize after the beam is turned on. As a result, some motion of the focal spot might occur during the start-up phase of irradiation. When acquiring portal images, this motion will affect the projected position of anatomy and field edges, especially when low exposures are used. In this paper, the motion of the focal spot and the effect of this motion on portal image analysis are quantified. A slightly tilted narrow slit phantom was placed at the isocenter of several linear accelerators and images were acquired (3.5 frames per second) by means of an amorphous silicon flat panel imager positioned approximately 0.7 m below the isocenter. The motion of the focal spot was determined by converting the tilted slit images to subpixel accurate line spread functions. The error in portal image analysis due to focal spot motionwas estimated by a subtraction of the relative displacement of the projected slit from the relative displacement of the field edges. It was found that the motion of the focal spot depends on the control system and design of the accelerator. The shift of the focal spot at the start of irradiation ranges between 0.05-0.7 mm in the gun-target (GT) direction. In the left-right (AB) direction the shift is generally smaller. The resulting error in portal image analysis due to focal spotmotion ranges between 0.05-1.1 mm for a dose corresponding to two monitor units (MUs). For 20 MUs, the effect of the focal spot motion reduces to 0.01-0.3 mm. The error in portal image analysis due to focal spot motion can be reduced by reducing the applied dose rate.

  10. Real-time Cherenkov emission portal imaging during CyberKnife® radiotherapy

    NASA Astrophysics Data System (ADS)

    Roussakis, Yiannis; Zhang, Rongxiao; Heyes, Geoff; Webster, Gareth; Mason, Suzannah; Green, Stuart; Pogue, Brian; Dehghani, Hamid

    2015-11-01

    The feasibility of real-time portal imaging during radiation therapy, through the Cherenkov emission (CE) effect is investigated via a medical linear accelerator (CyberKnife®) irradiating a partially-filled water tank with a 60 mm circular beam. A graticule of lead/plywood and a number of tissue equivalent materials were alternatively placed at the beam entrance face while the induced CE at the exit face was imaged using a gated electron-multiplying-intensified-charged-coupled device (emICCD) for both stationary and dynamic scenarios. This was replicated on an Elekta Synergy® linear accelerator with portal images acquired using the iViewGT™ system. Profiles across the acquired portal images were analysed to reveal the potential resolution and contrast limits of this novel CE based portal imaging technique and compared against the current standard. The CE resolution study revealed that using the lead/plywood graticule, separations down to 3.4  ±  0.5 mm can be resolved. A 28 mm thick tissue-equivalent rod with electron density of 1.69 relative to water demonstrated a CE contrast of 15% through air and 14% through water sections, as compared to a corresponding contrast of 19% and 12% using the iViewGT™ system. For dynamic scenarios, video rate imaging with 30 frames per second was achieved. It is demonstrated that CE-based portal imaging is feasible to identify both stationary and dynamic objects within a CyberKnife® radiotherapy treatment field.

  11. Real-time Cherenkov emission portal imaging during CyberKnife® radiotherapy.

    PubMed

    Roussakis, Yiannis; Zhang, Rongxiao; Heyes, Geoff; Webster, Gareth; Mason, Suzannah; Green, Stuart; Pogue, Brian; Dehghani, Hamid

    2015-11-21

    The feasibility of real-time portal imaging during radiation therapy, through the Cherenkov emission (CE) effect is investigated via a medical linear accelerator (CyberKnife(®)) irradiating a partially-filled water tank with a 60 mm circular beam. A graticule of lead/plywood and a number of tissue equivalent materials were alternatively placed at the beam entrance face while the induced CE at the exit face was imaged using a gated electron-multiplying-intensified-charged-coupled device (emICCD) for both stationary and dynamic scenarios. This was replicated on an Elekta Synergy(®) linear accelerator with portal images acquired using the iViewGT(™) system. Profiles across the acquired portal images were analysed to reveal the potential resolution and contrast limits of this novel CE based portal imaging technique and compared against the current standard. The CE resolution study revealed that using the lead/plywood graticule, separations down to 3.4  ±  0.5 mm can be resolved. A 28 mm thick tissue-equivalent rod with electron density of 1.69 relative to water demonstrated a CE contrast of 15% through air and 14% through water sections, as compared to a corresponding contrast of 19% and 12% using the iViewGT(™) system. For dynamic scenarios, video rate imaging with 30 frames per second was achieved. It is demonstrated that CE-based portal imaging is feasible to identify both stationary and dynamic objects within a CyberKnife(®) radiotherapy treatment field. PMID:26513015

  12. Assessment of the influence of a carbon fiber tabletop on portal imaging

    NASA Astrophysics Data System (ADS)

    Misiarz, Agnieszka; Krawczyk, Paweł; Swat, Kaja; Andrasiak, Michał

    2013-06-01

    The purpose of this paper was to investigate beam attenuation caused by a carbon-fiber tabletop and its influence on portal image quality. The dose was measured by a Farmer type jonization chamber. The measurements of the portal image quality were performed with an EPID QC phantom for 6 MV beam for a specified field size (covering all test elements of the phantom completely -26×26 cm2 in the isocenter, SSD 96.2 cm) and various portal—isocenter distances. The beam attenuation factor was measured for Polkam 16 treatment table with a carbon fiber tabletop. Carbon fiber tabletop induces beam attenuation in vertical direction by a factor of 3.39%. The lowest maximum deviation to the regression line for linearity was measured for 40 cm portal—phantom distance. The lowest signal to noise ratio was observed for the portal—phantom distance of 30 cm. This factor dropped by 9% for images with a tabletop. The difference in high contrast: horizontal is 3.64; 0.32; 3.25 for 50 cm, 40 cm and 30 cm respectively and vertical—3.64%; 0.32%; 4.01% for 50 cm, 40 cm and 30 cm respectively. The visibility of the holes with the smallest diameters (1 mm) is the same for 50 and 40 cm while it is better for 30 cm, as can be expected due to the lower SNR. Carbon-fiber inserts, tabletops play a vital role in modern radiotherapy. One of the most important advantages of carbon-fiber tabletops is the lack of the gantry direction limitations. In this paper the attenuation of a carbon-fiber tabletop and its influence on a portal image quality were investigated. Dose attenuation effects, comparable to other measurements, were found. That effect influences dose distribution delivered to the target volume and can increase the time of irradiation needed to take a portal image. It has been found that the best conditions for taking portal image occur when the distance from the phantom (patient) to the portal is 40 cm and the portal is parallel to the tabletop. In such conditions one observes the

  13. Radiotherapy treatment verification using radiological thickness measured with an amorphous silicon electronic portal imaging device: Monte Carlo simulation and experiment

    NASA Astrophysics Data System (ADS)

    Kairn, T.; Cassidy, D.; Sandford, P. M.; Fielding, A. L.

    2008-07-01

    This work validates the use of an amorphous-silicon, flat-panel electronic portal imaging device (a-Si EPID) for use as a gauge of patient or phantom radiological thickness, as an alternative to dosimetry. The response of the a-Si EPID is calibrated by adapting a technique previously applied to scanning liquid ion chamber EPIDs, and the stability, accuracy and reliability of this calibration are explored in detail. We find that the stability of this calibration, between different linacs at the same centre, is sufficient to justify calibrating only one of the EPIDs every month and using the calibration data thus obtained to perform measurements on all of the other linacs. Radiological thickness is shown to provide a reliable means of relating experimental measurements to the results of BEAMnrc Monte Carlo simulations of the linac-phantom-EPID system. For these reasons we suggest that radiological thickness can be used to verify radiotherapy treatment delivery and identify changes in the treatment field, patient position and target location, as well as patient physical thickness.

  14. The landsat image mosaic of the Antarctica Web Portal

    USGS Publications Warehouse

    Rusanowski, C.J.

    2007-01-01

    People believe what they can see. The Poles exist as a frozen dream to most people. The International Polar Year wants to break the ice (so to speak), open up the Poles to the general public, support current polar research, and encourage new research projects. The IPY officially begins in March, 2007. As part of this effort, the U.S. Geological Survey (USGS) and the British Antarctic Survey (BAS), with funding from the National Science Foundation (NSF), are developing three Landsat mosaics of Antarctica and an Antarctic Web Portal with a Community site and an online map viewer. When scientists are able to view the entire scope of polar research, they will be better able to collaborate and locate the resources they need. When the general public more readily sees what is happening in the polar environments, they will understand how changes to the polar areas affect everyone.

  15. Prediction of Liver Function by Using Magnetic Resonance-based Portal Venous Perfusion Imaging

    PubMed Central

    Cao, Yue; Wang, Hesheng; Johnson, Timothy D.; Pan, Charlie; Hussain, Hero; Balter, James M.; Normolle, Daniel; Ben-Josef, Edgar; Ten Haken, Randall K.; Lawrence, Theodore S.; Feng, Mary

    2013-01-01

    Purpose To evaluate whether liver function can be assessed globally and spatially by using volumetric dynamic contrast-enhanced magnetic resonance imaging MRI (DCE-MRI) to potentially aid in adaptive treatment planning. Methods and Materials Seventeen patients with intrahepatic cancer undergoing focal radiation therapy (RT) were enrolled in institution review board-approved prospective studies to obtain DCE-MRI (to measure regional perfusion) and indocyanine green (ICG) clearance rates (to measure overall liver function) prior to, during, and at 1 and 2 months after treatment. The volumetric distribution of portal venous perfusion in the whole liver was estimated for each scan. We assessed the correlation between mean portal venous perfusion in the nontumor volume of the liver and overall liver function measured by ICG before, during, and after RT. The dose response for regional portal venous perfusion to RT was determined using a linear mixed effects model. Results There was a significant correlation between the ICG clearance rate and mean portal venous perfusion in the functioning liver parenchyma, suggesting that portal venous perfusion could be used as a surrogate for function. Reduction in regional venous perfusion 1 month after RT was predicted by the locally accumulated biologically corrected dose at the end of RT (P<.0007). Regional portal venous perfusion measured during RT was a significant predictor for regional venous perfusion assessed 1 month after RT (P<.00001). Global hypovenous perfusion pre-RT was observed in 4 patients (3 patients with hepatocellular carcinoma and cirrhosis), 3 of whom had recovered from hypoperfusion, except in the highest dose regions, post-RT. In addition, 3 patients who had normal perfusion pre-RT had marked hypervenous perfusion or reperfusion in low-dose regions post-RT. Conclusions This study suggests that MR-based volumetric hepatic perfusion imaging may be a biomarker for spatial distribution of liver function, which

  16. Prediction of Liver Function by Using Magnetic Resonance-based Portal Venous Perfusion Imaging

    SciTech Connect

    Cao Yue; Wang Hesheng; Johnson, Timothy D.; Pan, Charlie; Hussain, Hero; Balter, James M.; Normolle, Daniel; Ben-Josef, Edgar; Ten Haken, Randall K.; Lawrence, Theodore S.; Feng, Mary

    2013-01-01

    Purpose: To evaluate whether liver function can be assessed globally and spatially by using volumetric dynamic contrast-enhanced magnetic resonance imaging MRI (DCE-MRI) to potentially aid in adaptive treatment planning. Methods and Materials: Seventeen patients with intrahepatic cancer undergoing focal radiation therapy (RT) were enrolled in institution review board-approved prospective studies to obtain DCE-MRI (to measure regional perfusion) and indocyanine green (ICG) clearance rates (to measure overall liver function) prior to, during, and at 1 and 2 months after treatment. The volumetric distribution of portal venous perfusion in the whole liver was estimated for each scan. We assessed the correlation between mean portal venous perfusion in the nontumor volume of the liver and overall liver function measured by ICG before, during, and after RT. The dose response for regional portal venous perfusion to RT was determined using a linear mixed effects model. Results: There was a significant correlation between the ICG clearance rate and mean portal venous perfusion in the functioning liver parenchyma, suggesting that portal venous perfusion could be used as a surrogate for function. Reduction in regional venous perfusion 1 month after RT was predicted by the locally accumulated biologically corrected dose at the end of RT (P<.0007). Regional portal venous perfusion measured during RT was a significant predictor for regional venous perfusion assessed 1 month after RT (P<.00001). Global hypovenous perfusion pre-RT was observed in 4 patients (3 patients with hepatocellular carcinoma and cirrhosis), 3 of whom had recovered from hypoperfusion, except in the highest dose regions, post-RT. In addition, 3 patients who had normal perfusion pre-RT had marked hypervenous perfusion or reperfusion in low-dose regions post-RT. Conclusions: This study suggests that MR-based volumetric hepatic perfusion imaging may be a biomarker for spatial distribution of liver function, which

  17. NOTE: A method for controlling image acquisition in electronic portal imaging devices

    NASA Astrophysics Data System (ADS)

    Glendinning, A. G.; Hunt, S. G.; Bonnett, D. E.

    2001-02-01

    Certain types of camera-based electronic portal imaging devices (EPIDs) which initiate image acquisition based on sensing a change in video level have been observed to trigger unreliably at the beginning of dynamic multileaf collimation sequences. A simple, novel means of controlling image acquisition with an Elekta linear accelerator (Elekta Oncology Systems, Crawley, UK) is proposed which is based on illumination of a photodetector (ORP-12, Silonex Inc., Plattsburgh, NY, USA) by the electron gun of the accelerator. By incorporating a simple trigger circuit it is possible to derive a beam on/off status signal which changes at least 100 ms before any dose is measured by the accelerator. The status signal does not return to the beam-off state until all dose has been delivered and is suitable for accelerator pulse repetition frequencies of 50-400 Hz. The status signal is thus a reliable means of indicating the initiation and termination of radiation exposure, and thus controlling image acquisition of such EPIDs for this application.

  18. Motion estimation accuracy for visible-light/gamma-ray imaging fusion for portable portal monitoring

    NASA Astrophysics Data System (ADS)

    Karnowski, Thomas P.; Cunningham, Mark F.; Goddard, James S.; Cheriyadat, Anil M.; Hornback, Donald E.; Fabris, Lorenzo; Kerekes, Ryan A.; Ziock, Klaus-Peter; Gee, Timothy F.

    2010-01-01

    The use of radiation sensors as portal monitors is increasing due to heightened concerns over the smuggling of fissile material. Portable systems that can detect significant quantities of fissile material that might be present in vehicular traffic are of particular interest. We have constructed a prototype, rapid-deployment portal gamma-ray imaging portal monitor that uses machine vision and gamma-ray imaging to monitor multiple lanes of traffic. Vehicles are detected and tracked by using point detection and optical flow methods as implemented in the OpenCV software library. Points are clustered together but imperfections in the detected points and tracks cause errors in the accuracy of the vehicle position estimates. The resulting errors cause a "blurring" effect in the gamma image of the vehicle. To minimize these errors, we have compared a variety of motion estimation techniques including an estimate using the median of the clustered points, a "best-track" filtering algorithm, and a constant velocity motion estimation model. The accuracy of these methods are contrasted and compared to a manually verified ground-truth measurement by quantifying the rootmean- square differences in the times the vehicles cross the gamma-ray image pixel boundaries compared with a groundtruth manual measurement.

  19. Liver Function After Irradiation Based on Computed Tomographic Portal Vein Perfusion Imaging

    SciTech Connect

    Cao Yue Pan, Charlie; Balter, James M.; Platt, Joel F.; Francis, Isaac R.; Knol, James A.; Normolle, Daniel; Ben-Josef, Edgar; Haken, Randall K. ten; Lawrence, Theodore S.

    2008-01-01

    Purpose: To determine whether individual and regional liver sensitivity to radiation could be assessed by measuring liver perfusion during a course of treatment using dynamic contrast-enhanced computed tomography scanning. Methods and Materials: Patients with intrahepatic cancer undergoing conformal radiotherapy underwent dynamic contrast-enhanced computed tomography (to measure perfusion distribution) and an indocyanine extraction study (to measure liver function) before, during, and 1 month after treatment. We hoped to determine whether the residual functioning liver (i.e., those regions showing portal vein perfusion) could be used to predict overall liver function after irradiation. Results: Radiation doses from 45 to 84 Gy resulted in undetectable regional portal vein perfusion 1 month after treatment. The volume of each liver with undetectable portal vein perfusion ranged from 0 to 39% and depended both on the patient's sensitivity and on dose distribution. There was a significant correlation between indocyanine green clearance and the mean of the estimated portal vein perfusion in the functional liver parenchyma (p < 0.001). Conclusion: This study reveals substantial individual variability in the sensitivity of the liver to irradiation. In addition, these findings suggest that hepatic perfusion imaging may be a marker for liver function and has the potential to be a tool for individualizing therapy.

  20. LIVER FUNCTION AFTER IRRADIATION BASED UPON CT PORTAL VEIN PERFUSION IMAGING

    PubMed Central

    Cao, Yue; Pan, Charlie; Balter, James M.; Platt, Joel F.; Francis, Isaac R.; Knol, James A.; Normolle, Daniel; Ben-Josef, Edgar; Ten Haken, Randall K.; Lawrence, Theodore S.

    2009-01-01

    Purpose The role of radiation in the treatment of intrahepatic cancer is limited by the development of radiation-induced liver disease (RILD), which occurs weeks after the course of radiation is completed. We hypothesized that, as the pathophysiology of RILD is veno-occlusive disease, we could assess individual and regional liver sensitivity to radiation by measuring liver perfusion during a course of treatment using dynamic contrast enhanced CT (DCE-CT) scanning. Materials and Methods Patients with intrahepatic cancer undergoing conformal radiotherapy underwent DCE-CT (to measure perfusion distribution) and an indocyanine extraction study (to measure liver function) prior to, during, and one month after treatment. We wished to determine if the residual functioning liver (i.e. those regions showing portal vein perfusion) could be used to predict overall liver function after irradiation. Results Radiation doses from 45 to 84 Gy resulted in undectable regional portal vein perfusion one month after treatment. The volume of each liver with undectable portal vein perfusion ranged from 0% to 39% and depended both on the patient’s sensitivity and dose distribution. There was a significant correlation between indocyanine green clearance and the mean of the estimated portal vein perfusion in the functional liver parenchyma (P < .001). Conclusion This study reveals substantial individual variability in the sensitivity of the liver to irradiation. In addition, these findings suggest that hepatic perfusion imaging may be a marker for liver function, and has the potential to be a tool for individualizing therapy. PMID:17855011

  1. Portal imaging practice patterns of children's oncology group institutions: Dosimetric assessment and recommendations for minimizing unnecessary exposure

    SciTech Connect

    Olch, Arthur J. . E-mail: aolch@chla.usc.edu; Geurts, Mark; Thomadsen, Bruce; Famiglietti, Robin; Chang, Eric L.

    2007-02-01

    Purpose: To determine and analyze the dosimetric consequences of current portal imaging practices for pediatric patients, and make specific recommendations for reducing exposure from portal imaging procedures. Methods and Materials: A survey was sent to approximately 250 Children's Oncology Group (COG) member institutions asking a series of questions about their portal imaging practices. Three case studies are presented with dosimetric analysis to illustrate the magnitude of unintended dose received by nontarget tissues using the most common techniques from the survey. Results: The vast majority of centers use double-exposure portal image techniques with a variety of open field margins. Only 17% of portal images were obtained during treatment, and for other imaging methods, few centers subtract monitor units from the treatment delivery. The number of monitor units used was nearly the same regardless of imager type, including electronic portal imaging devices. Eighty-six percent imaged all fields the first week and 17% imaged all fields every week. An additional 1,112 cm{sup 3} of nontarget tissue received 1 Gy in one of the example cases. Eight new recommendations are made, which will lower nontarget radiation doses with minimal impact on treatment verification accuracy. Conclusion: Based on the survey, changes can be made in portal imaging practices that will lower nontarget doses. It is anticipated that treatment verification accuracy will be minimally affected. Specific recommendations made to decrease the imaging dose and help lower the rate of radiation-induced secondary cancers in children are proposed for inclusion in future COG protocols using radiation therapy.

  2. Imaging and 3-D dosimetry: top tips for MRI and optical CT

    NASA Astrophysics Data System (ADS)

    Doran, Simon J.

    2010-11-01

    The conference "refresher session" associated with this abstract reviews the main principles of the two most important imaging readout modalities for 3-D dosimetry: MRI and optical CT. Best practices for both these techniques are already described in several different places in the literature, but, for the uninitiated, there are a number of pitfalls. Here, I list some of the important considerations required to obtain good results from these methods and point to relevant prior work.

  3. Portal imaging: Performance improvement in noise reduction by means of wavelet processing.

    PubMed

    González-López, Antonio; Morales-Sánchez, Juan; Larrey-Ruiz, Jorge; Bastida-Jumilla, María-Consuelo; Verdú-Monedero, Rafael

    2016-01-01

    This paper discusses the suitability, in terms of noise reduction, of various methods which can be applied to an image type often used in radiation therapy: the portal image. Among these methods, the analysis focuses on those operating in the wavelet domain. Wavelet-based methods tested on natural images--such as the thresholding of the wavelet coefficients, the minimization of the Stein unbiased risk estimator on a linear expansion of thresholds (SURE-LET), and the Bayes least-squares method using as a prior a Gaussian scale mixture (BLS-GSM method)--are compared with other methods that operate on the image domain--an adaptive Wiener filter and a nonlocal mean filter (NLM). For the assessment of the performance, the peak signal-to-noise ratio (PSNR), the structural similarity index (SSIM), the Pearson correlation coefficient, and the Spearman rank correlation (ρ) coefficient are used. The performance of the wavelet filters and the NLM method are similar, but wavelet filters outperform the Wiener filter in terms of portal image denoising. It is shown how BLS-GSM and NLM filters produce the smoothest image, while keeping soft-tissue and bone contrast. As for the computational cost, filters using a decimated wavelet transform (decimated thresholding and SURE-LET) turn out to be the most efficient, with calculation times around 1 s. PMID:26602966

  4. Portal biliopathy.

    PubMed

    Khuroo, Mohammad S; Rather, Ajaz A; Khuroo, Naira S; Khuroo, Mehnaaz S

    2016-09-21

    Portal biliopathy refers to cholangiographic abnormalities which occur in patients with portal cavernoma. These changes occur as a result of pressure on bile ducts from bridging tortuous paracholedochal, epicholedochal and cholecystic veins. Bile duct ischemia may occur due prolonged venous pressure effect or result from insufficient blood supply. In addition, encasement of ducts may occur due fibrotic cavernoma. Majority of patients are asymptomatic. Portal biliopathy is a progressive disease and patients who have long standing disease and more severe bile duct abnormalities present with recurrent episodes of biliary pain, cholangitis and cholestasis. Serum chemistry, ultrasound with color Doppler imaging, magnetic resonance imaging with magnetic resonance cholangiopancreatography and magnetic resonance portovenography are modalities of choice for evaluation of portal biliopathy. Endoscopic retrograde cholangiography being an invasive procedure is indicated for endotherapy only. Management of portal biliopathy is done in a stepwise manner. First, endotherapy is done for dilation of biliary strictures, placement of biliary stents to facilitate drainage and removal of bile duct calculi. Next portal venous pressure is reduced by formation of surgical porto-systemic shunt or transjugular intrahepatic portosystemic shunt. This causes significant resolution of biliary changes. Patients who persist with biliary symptoms and bile duct changes may benefit from surgical biliary drainage procedures (hepaticojejunostomy or choledechoduodenostomy). PMID:27672292

  5. Portal biliopathy

    PubMed Central

    Khuroo, Mohammad S; Rather, Ajaz A; Khuroo, Naira S; Khuroo, Mehnaaz S

    2016-01-01

    Portal biliopathy refers to cholangiographic abnormalities which occur in patients with portal cavernoma. These changes occur as a result of pressure on bile ducts from bridging tortuous paracholedochal, epicholedochal and cholecystic veins. Bile duct ischemia may occur due prolonged venous pressure effect or result from insufficient blood supply. In addition, encasement of ducts may occur due fibrotic cavernoma. Majority of patients are asymptomatic. Portal biliopathy is a progressive disease and patients who have long standing disease and more severe bile duct abnormalities present with recurrent episodes of biliary pain, cholangitis and cholestasis. Serum chemistry, ultrasound with color Doppler imaging, magnetic resonance imaging with magnetic resonance cholangiopancreatography and magnetic resonance portovenography are modalities of choice for evaluation of portal biliopathy. Endoscopic retrograde cholangiography being an invasive procedure is indicated for endotherapy only. Management of portal biliopathy is done in a stepwise manner. First, endotherapy is done for dilation of biliary strictures, placement of biliary stents to facilitate drainage and removal of bile duct calculi. Next portal venous pressure is reduced by formation of surgical porto-systemic shunt or transjugular intrahepatic portosystemic shunt. This causes significant resolution of biliary changes. Patients who persist with biliary symptoms and bile duct changes may benefit from surgical biliary drainage procedures (hepaticojejunostomy or choledechoduodenostomy).

  6. Portal biliopathy

    PubMed Central

    Khuroo, Mohammad S; Rather, Ajaz A; Khuroo, Naira S; Khuroo, Mehnaaz S

    2016-01-01

    Portal biliopathy refers to cholangiographic abnormalities which occur in patients with portal cavernoma. These changes occur as a result of pressure on bile ducts from bridging tortuous paracholedochal, epicholedochal and cholecystic veins. Bile duct ischemia may occur due prolonged venous pressure effect or result from insufficient blood supply. In addition, encasement of ducts may occur due fibrotic cavernoma. Majority of patients are asymptomatic. Portal biliopathy is a progressive disease and patients who have long standing disease and more severe bile duct abnormalities present with recurrent episodes of biliary pain, cholangitis and cholestasis. Serum chemistry, ultrasound with color Doppler imaging, magnetic resonance imaging with magnetic resonance cholangiopancreatography and magnetic resonance portovenography are modalities of choice for evaluation of portal biliopathy. Endoscopic retrograde cholangiography being an invasive procedure is indicated for endotherapy only. Management of portal biliopathy is done in a stepwise manner. First, endotherapy is done for dilation of biliary strictures, placement of biliary stents to facilitate drainage and removal of bile duct calculi. Next portal venous pressure is reduced by formation of surgical porto-systemic shunt or transjugular intrahepatic portosystemic shunt. This causes significant resolution of biliary changes. Patients who persist with biliary symptoms and bile duct changes may benefit from surgical biliary drainage procedures (hepaticojejunostomy or choledechoduodenostomy). PMID:27672292

  7. Dosimetry for spectral molecular imaging of small animals with MARS-CT

    NASA Astrophysics Data System (ADS)

    Ganet, Noémie; Anderson, Nigel; Bell, Stephen; Butler, Anthony; Butler, Phil; Carbonez, Pierre; Cook, Nicholas; Cotterill, Tony; Marsh, Steven; Panta, Raj Kumar; Laban, John; Walker, Sophie; Yeabsley, Adam; Damet, Jérôme

    2015-03-01

    The Medipix All Resolution Scanner (MARS) spectral CT is intended for small animal, pre-clinical imaging and uses an x-ray detector (Medipix) operating in single photon counting mode. The MARS system provides spectrometric information to facilitate differentiation of tissue types and bio-markers. For longitudinal studies of disease models, it is desirable to characterise the system's dosimetry. This dosimetry study is performed using three phantoms each consisting of a 30 mm diameter homogeneous PMMA cylinder simulating a mouse. The imaging parameters used for this study are derived from those used for gold nanoparticle identification in mouse kidneys. Dosimetry measurement are obtained with thermo-luminescent Lithium Fluoride (LiF:CuMgP) detectors, calibrated in terms of air kerma and placed at different depths and orientations in the phantoms. Central axis TLD air kerma rates of 17.2 (± 0.71) mGy/min and 18.2 (± 0.75) mGy/min were obtained for different phantoms and TLD orientations. Validation measurements were acquired with a pencil ionization chamber, giving an air-kerma rate of 20.3 (±1) mGy/min and an estimated total air kerma of 81.2 (± 4) mGy for a 720 projection acquisition. It is anticipated that scanner design improvements will significantly decrease future dose requirements. The procedures developed in this work will be used for further dosimetry calculations when optimizing image acquisition for the MARS system as it undergoes development towards human clinical applications.

  8. Megavoltage image contrast with low-atomic number target materials and amorphous silicon electronic portal imagers

    NASA Astrophysics Data System (ADS)

    Orton, E. J.; Robar, J. L.

    2009-03-01

    Low-atomic number (Z) targets have been shown to improve contrast in megavoltage (MV) images when using film-screen detection systems. This research aims to quantify the effect of low-Z targets on MV image contrast using an amorphous silicon electronic portal image detector (a-Si EPID) through both experimental measurement and Monte Carlo (MC) simulation. Experimental beams were produced with the linac running in the 6 MeV electron mode and with a 1.0 cm aluminum (Al, Z = 13) target replacing flattening filtration in the carousel, (6 MeV/Al). A 2100EX Varian linac equipped with an aS500 EPID was used with the QC3 MV phantom for the majority of contrast measurements. The BEAMnrc/EGSnrc MC package was used to build a model of the full imaging system including beam generation (linac head), the a-Si detector and the contrast phantom. The model accurately reproduces contrast measurements to within 2.5% for both the standard 6 MV therapy beam and the 6 MeV/Al beam. The contrast advantage of 6 MeV/Al over 6 MV, as quantified with the QC3 phantom, ranged from a factor increase of 1.6 ± 0.1 to 2.8 ± 0.2. Only a modest improvement in contrast was seen when the incident electron energy was reduced to 4 MeV (up to factor of 1.2 ± 0.1 over 6 MeV/Al) or with removal of the copper build-up layer in the detector, (up to factor of 1.2 ± 0.1 over 6 MeV/Al). Further decreasing the target Z, to beryllium (Be, Z = 4), at 4 MeV showed no significant improvement over 4 MeV/Al. Experimentally, the contrast advantage of 6 MeV/Al over 6 MV was found to decrease with increasing patient thickness, as can be expected due to selective attenuation of low-energy photons. At head and neck-like thicknesses, the low-Z advantage is a factor increase of 1.7 ± 0.1.

  9. Dosimetry and image quality assessment in a direct radiography system

    PubMed Central

    Oliveira, Bruno Beraldo; de Oliveira, Marcio Alves; Paixão, Lucas; Teixeira, Maria Helena Araújo; Nogueira, Maria do Socorro

    2014-01-01

    Objective To evaluate the mean glandular dose with a solid state detector and the image quality in a direct radiography system, utilizing phantoms. Materials and Methods Irradiations were performed with automatic exposure control and polymethyl methacrylate slabs with different thicknesses to calculate glandular dose values. The image quality was evaluated by means of the structures visualized on the images of the phantoms. Results Considering the uncertainty of the measurements, the mean glandular dose results are in agreement with the values provided by the equipment and with internationally adopted reference levels. Results obtained from images of the phantoms were in agreement with the reference values. Conclusion The present study contributes to verify the equipment conformity as regards dose values and image quality. PMID:25741119

  10. Review on the characteristics of radiation detectors for dosimetry and imaging

    NASA Astrophysics Data System (ADS)

    Seco, Joao; Clasie, Ben; Partridge, Mike

    2014-10-01

    The enormous advances in the understanding of human anatomy, physiology and pathology in recent decades have led to ever-improving methods of disease prevention, diagnosis and treatment. Many of these achievements have been enabled, at least in part, by advances in ionizing radiation detectors. Radiology has been transformed by the implementation of multi-slice CT and digital x-ray imaging systems, with silver halide films now largely obsolete for many applications. Nuclear medicine has benefited from more sensitive, faster and higher-resolution detectors delivering ever-higher SPECT and PET image quality. PET/MR systems have been enabled by the development of gamma ray detectors that can operate in high magnetic fields. These huge advances in imaging have enabled equally impressive steps forward in radiotherapy delivery accuracy, with 4DCT, PET and MRI routinely used in treatment planning and online image guidance provided by cone-beam CT. The challenge of ensuring safe, accurate and precise delivery of highly complex radiation fields has also both driven and benefited from advances in radiation detectors. Detector systems have been developed for the measurement of electron, intensity-modulated and modulated arc x-ray, proton and ion beams, and around brachytherapy sources based on a very wide range of technologies. The types of measurement performed are equally wide, encompassing commissioning and quality assurance, reference dosimetry, in vivo dosimetry and personal and environmental monitoring. In this article, we briefly introduce the general physical characteristics and properties that are commonly used to describe the behaviour and performance of both discrete and imaging detectors. The physical principles of operation of calorimeters; ionization and charge detectors; semiconductor, luminescent, scintillating and chemical detectors; and radiochromic and radiographic films are then reviewed and their principle applications discussed. Finally, a general

  11. New geo-portal for MODIS/SEVIRI image products with geolocation-based retrieval functionality

    NASA Astrophysics Data System (ADS)

    Sevilla, Jorge; Julien, Yves; Sória, Guillem; Sobrino, José A.; Plaza, Antonio

    2015-01-01

    A large number of remote sensing data sets have been collected in recent years by Earth observation instruments such as the moderate resolution imaging spectroradiometer (MODIS) aboard the Terra/Aqua satellite and the spinning enhanced visible and infrared imager (SEVIRI) aboard the geostationary platform Meteosat Second Generation. The advanced remote sensing products resulting from the analysis of these data are useful in a wide variety of applications but require significant resources in terms of storage, retrieval, and analysis. Despite the wide availability of these MODIS/SEVIRI products, the data coming from these instruments are spread among different locations and retrieved from different sources, and there is no common data repository from which the data or the associated products can be retrieved. We take a first step toward the development of a geo-portal for storing and efficiently retrieving MODIS/SEVIRI remote sensing products. The products are obtained using an automatic system that processes the data as soon as they are provided by the collecting antennas, and then the final products are uploaded with a one day delay in the geo-portal. Our focus in this work is on describing the design and efficient implementation of the geo-portal, which allows for a user-friendly and effective access to a full repository of MODIS/SEVIRI advanced products (comprising tens of terabytes of data) using geolocation retrieval capabilities. The geo-portal has been implemented as a web application composed of different layers. Its modular design provides quality of service and scalability (capacity for growth without any quality losing), allowing for the addition of components without the need to modify the entire system. On the client layer, an intuitive web browser interface provides users with remote access to the system. On the server layer, the system provides advanced data management and storage capabilities. On the storage layer, the system provides a secure

  12. An automated voxelized dosimetry tool for radionuclide therapy based on serial quantitative SPECT/CT imaging

    SciTech Connect

    Jackson, Price A.; Kron, Tomas; Beauregard, Jean-Mathieu; Hofman, Michael S.; Hogg, Annette; Hicks, Rodney J.

    2013-11-15

    Purpose: To create an accurate map of the distribution of radiation dose deposition in healthy and target tissues during radionuclide therapy.Methods: Serial quantitative SPECT/CT images were acquired at 4, 24, and 72 h for 28 {sup 177}Lu-octreotate peptide receptor radionuclide therapy (PRRT) administrations in 17 patients with advanced neuroendocrine tumors. Deformable image registration was combined with an in-house programming algorithm to interpolate pharmacokinetic uptake and clearance at a voxel level. The resultant cumulated activity image series are comprised of values representing the total number of decays within each voxel's volume. For PRRT, cumulated activity was translated to absorbed dose based on Monte Carlo-determined voxel S-values at a combination of long and short ranges. These dosimetric image sets were compared for mean radiation absorbed dose to at-risk organs using a conventional MIRD protocol (OLINDA 1.1).Results: Absorbed dose values to solid organs (liver, kidneys, and spleen) were within 10% using both techniques. Dose estimates to marrow were greater using the voxelized protocol, attributed to the software incorporating crossfire effect from nearby tumor volumes.Conclusions: The technique presented offers an efficient, automated tool for PRRT dosimetry based on serial post-therapy imaging. Following retrospective analysis, this method of high-resolution dosimetry may allow physicians to prescribe activity based on required dose to tumor volume or radiation limits to healthy tissue in individual patients.

  13. TLD assessment of mouse dosimetry during microCT imaging

    SciTech Connect

    Figueroa, Said Daibes; Winkelmann, Christopher T.; Miller, William H.; Volkert, Wynn A.; Hoffman, Timothy J.

    2008-09-15

    Advances in laboratory animal imaging have provided new resources for noninvasive biomedical research. Among these technologies is microcomputed tomography (microCT) which is widely used to obtain high resolution anatomic images of small animals. Because microCT utilizes ionizing radiation for image formation, radiation exposure during imaging is a concern. The objective of this study was to quantify the radiation dose delivered during a standard microCT scan. Radiation dose was measured using thermoluminescent dosimeters (TLDs), which were irradiated employing an 80 kVp x-ray source, with 0.5 mm Al filtration and a total of 54 mA s for a full 360 deg rotation of the unit. The TLD data were validated using a 3.2 cm{sup 3} CT ion chamber probe. TLD results showed a single microCT scan air kerma of 78.0{+-}5.0 mGy when using a poly(methylmethacrylate) (PMMA) anesthesia support module and an air kerma of 92.0{+-}6.0 mGy without the use of the anesthesia module. The validation CT ion chamber study provided a measured radiation air kerma of 81.0{+-}4.0 mGy and 97.0{+-}5.0 mGy with and without the PMMA anesthesia module, respectively. Internal TLD analysis demonstrated an average mouse organ radiation absorbed dose of 76.0{+-}5.0 mGy. The author's results have defined x-ray exposure for a routine microCT study which must be taken into consideration when performing serial molecular imaging studies involving the microCT imaging modality.

  14. TLD assessment of mouse dosimetry during microCT imaging.

    PubMed

    Figueroa, Said Daibes; Winkelmann, Christopher T; Miller, H William; Volkert, Wynn A; Hoffman, Timothy J

    2008-09-01

    Advances in laboratory animal imaging have provided new resources for noninvasive biomedical research. Among these technologies is microcomputed tomography (microCT) which is widely used to obtain high resolution anatomic images of small animals. Because microCT utilizes ionizing radiation for image formation, radiation exposure during imaging is a concern. The objective of this study was to quantify the radiation dose delivered during a standard microCT scan. Radiation dose was measured using thermoluminescent dosimeters (TLDs), which were irradiated employing an 80 kVp x-ray source, with 0.5 mm A1 filtration and a total of 54 mA s for a full 360 deg rotation of the unit. The TLD data were validated using a 3.2 cm3 CT ion chamber probe. TLD results showed a single microCT scan air kerma of 78.0 +/- 5.0 mGy when using a poly(methylmethacrylate) (PMMA) anesthesia support module and an air kerma of 92.0 +/- 6.0 mGy without the use of the anesthesia module. The validation CT ion chamber study provided a measured radiation air kerma of 81.0 +/- 4.0 mGy and 97.0 +/- 5.0 mGy with and without the PMMA anesthesia module, respectively. Internal TLD analysis demonstrated an average mouse organ radiation absorbed dose of 76.0 +/- 5.0 mGy. The author's results have defined x-ray exposure for a routine microCT study which must be taken into consideration when performing serial molecular imaging studies involving the microCT imaging modality.

  15. Simulations of three-dimensional radiometric imaging of extended sources in a security screening portal

    NASA Astrophysics Data System (ADS)

    Salmon, Neil A.; Bowring, Nick

    2015-10-01

    This paper investigates by simulation the use of the three-dimensional aperture synthesis imaging technique to image three-dimensional extended sources. Software was written to access the three-dimensional information from computer graphics models in the formats of *.dxf and *.3ds and use these to generate synthetic cross-correlations, as if they would have been generated by an aperture synthesis antenna/receiver array measuring the radiometric emission from the three-dimensional object. A three-dimensional (near-field) aperture synthesis imaging algorithm generates [1] a voxel image of the three-dimensional object. Images created from a sphere indicate faithful reproduction about a single phase centre when the radius of the sphere is less than the Fresnel scale. However, for larger spheres, definition in the threedimensional imagery suffers and a phenomenon, referred to in this paper as Fresnel noise, appears in the image. Images of objects larger than the Fresnel scale can be created by having multiple smaller images, each having a size approximately of the Fresnel scale and centred on separate phase centres. Using the software to generate threedimensional imagery of a person, to demonstrate capabilities for portal security screening, indicates the technique works to first order. Improvements are needed in the software to improve the spatial sampling of the radiometric fields from the three-dimensional objects and implement a volumetric image mosaicking technique to remove the Fresnel noise.

  16. Evaluation of a cassette-screen-film combination for radiation therapy portal localization imaging with improved contrast.

    PubMed

    Haus, A G; Dickerson, R E; Huff, K E; Monte, S; Schlager, B A; Atanas, M; Matloubieh, A

    1997-10-01

    A traditional limitation with radiation therapy portal images is low image contrast, due in part to the low attenuation of the exposing radiation by the tissues being imaged, and the contrast capabilities of the image receptor. We have developed, and have clinically evaluated, a cassette-screen-film combination for portal localization imaging, which features a copper front screen plus Gd2O2S:Tb fluorescent screens and a slow-speed, fine grain, film emulsion with inherently high contrast coated on both sides of a 7 mil Estar base. The film can be processed in a conventional rapid-process film processor. Sensitometric data indicate that the film contrast (average gradient) for the new combination is approximately 3.5 times higher than the conventional portal localization systems in current use. The new combination has been clinically compared with two conventional systems. The required monitor unit settings were found to be similar. Initial clinical results indicate portal images made with the new combination are superior to those obtained with the conventional combinations. The images have much higher contrast, subjective impressions of lower noise, show clearer definition of structures, and are much easier to read.

  17. A review of 3D image-based dosimetry, technical considerations and emerging perspectives in 90Y microsphere therapy

    PubMed Central

    O’ Doherty, Jim

    2016-01-01

    Yttrium-90 radioembolization (90Y-RE) is a well-established therapy for the treatment of hepatocellular carcinoma (HCC) and also of metastatic liver deposits from other malignancies. Nuclear Medicine and Cath Lab diagnostic imaging takes a pivotal role in the success of the treatment, and in order to fully exploit the efficacy of the technique and provide reliable quantitative dosimetry that are related to clinical endpoints in the era of personalized medicine, technical challenges in imaging need to be overcome. In this paper, the extensive literature of current 90Y-RE techniques and challenges facing it in terms of quantification and dosimetry are reviewed, with a focus on the current generation of 3D dosimetry techniques. Finally, new emerging techniques are reviewed which seek to overcome these challenges, such as high-resolution imaging, novel surgical procedures and the use of other radiopharmaceuticals for therapy and pre-therapeutic planning. PMID:27182449

  18. A semiconductor radiation imaging pixel detector for space radiation dosimetry

    NASA Astrophysics Data System (ADS)

    Kroupa, Martin; Bahadori, Amir; Campbell-Ricketts, Thomas; Empl, Anton; Hoang, Son Minh; Idarraga-Munoz, John; Rios, Ryan; Semones, Edward; Stoffle, Nicholas; Tlustos, Lukas; Turecek, Daniel; Pinsky, Lawrence

    2015-07-01

    Progress in the development of high-performance semiconductor radiation imaging pixel detectors based on technologies developed for use in high-energy physics applications has enabled the development of a completely new generation of compact low-power active dosimeters and area monitors for use in space radiation environments. Such detectors can provide real-time information concerning radiation exposure, along with detailed analysis of the individual particles incident on the active medium. Recent results from the deployment of detectors based on the Timepix from the CERN-based Medipix2 Collaboration on the International Space Station (ISS) are reviewed, along with a glimpse of developments to come. Preliminary results from Orion MPCV Exploration Flight Test 1 are also presented.

  19. A semiconductor radiation imaging pixel detector for space radiation dosimetry.

    PubMed

    Kroupa, Martin; Bahadori, Amir; Campbell-Ricketts, Thomas; Empl, Anton; Hoang, Son Minh; Idarraga-Munoz, John; Rios, Ryan; Semones, Edward; Stoffle, Nicholas; Tlustos, Lukas; Turecek, Daniel; Pinsky, Lawrence

    2015-07-01

    Progress in the development of high-performance semiconductor radiation imaging pixel detectors based on technologies developed for use in high-energy physics applications has enabled the development of a completely new generation of compact low-power active dosimeters and area monitors for use in space radiation environments. Such detectors can provide real-time information concerning radiation exposure, along with detailed analysis of the individual particles incident on the active medium. Recent results from the deployment of detectors based on the Timepix from the CERN-based Medipix2 Collaboration on the International Space Station (ISS) are reviewed, along with a glimpse of developments to come. Preliminary results from Orion MPCV Exploration Flight Test 1 are also presented. PMID:26256630

  20. Input/output characteristics of a matrix ion-chamber electronic portal imaging device.

    PubMed

    Yin, F F; Schell, M C; Rubin, P

    1994-09-01

    The input/output characteristics of a matrix liquid ion-chamber electronic portal imaging device (EPID) are investigated to elucidate the imaging properties of EPIDs. The radiation input to the detector, represented by dose rate, and the pixel value output from the device are related by a characteristic curve. Various incident radiation intensities are obtained by changing the source-to-detector distance (SDD). For each incident radiation intensity, an electronic portal image is obtained using a field size of 5 x 5 cm2. The output pixel value of the EPID is represented by the average pixel value of a region of interest of 9 x 9 pixels centered at a selected point. The effects of various accelerator settings, such as the repetition-rate setting and photon energy, gantry angle, field size, SDD, and acquisition mode of the EPID on characteristic curves are investigated at the central axis. The off-axis response of the detector is also examined. The derivative of the pixel value with respect to the input dose rate is used to analyze the detector contrast. Results indicate that the output pixel value is not a linear function of the incident radiation intensity. The detector contrast is comparable between photon energies of 10 and 6 MV and increases at low dose rates. The response of the imaging device varies substantially with acquisition mode, but is less sensitive to the SDD used for calibration. Characteristic curves are consistent for different gantry angles at the central axis and with the off-axis locations when the gantry angle is used for imaging and calibration, but vary with off-axis locations when the gantry angle is not at the calibration direction. Characteristic curves are also found to vary with different field sizes, but are similar in shape.

  1. Improved dosimetry for targeted radionuclide therapy using nonrigid registration on sequential SPECT images

    SciTech Connect

    Ao, Edwin C. I.; Mok, Greta S. P.; Wu, Nien-Yun; Wang, Shyh-Jen; Song, Na

    2015-02-15

    Purpose: Voxel-level and patient-specific 3D dosimetry for targeted radionuclide therapy (TRT) typically involves serial nuclear medicine scans. Misalignment of the images can result in reduced dosimetric accuracy. Since the scans are typically performed over a period of several days, there will be patient movement between scans and possible nonrigid organ deformation. This work aims to implement and evaluate the use of nonrigid image registration on a series of quantitative SPECT (QSPECT) images for TRT dosimetry. Methods: A population of 4D extended cardiac torso phantoms, comprised of three In-111 Zevalin biokinetics models and three anatomical variations, was generated based on the patient data. The authors simulated QSPECT acquisitions at five time points. At each time point, individual organ and whole-body deformation between scans were modeled by translating/rotating organs and the body up to 5°/voxels, keeping ≤5% difference in organ volume. An analytical projector was used to generate realistic noisy projections for a medium energy general purpose collimator. Projections were reconstructed using OS-EM algorithm with geometric collimator detector response, attenuation, and scatter corrections. The QSPECT images were registered using organ-based nonrigid image registration method. The cumulative activity in each voxel was obtained by integrating the activity over time. Dose distribution images were obtained by convolving the cumulative activity images with a Y-90 dose kernel. Dose volume histograms (DVHs) for organs-of-interest were analyzed. Results: After nonrigid registration, the mean differences in organ doses compared to the case without misalignment were improved from (−15.50 ± 5.59)% to (−2.12 ± 1.05)% and (−7.28 ± 2.30)% to (−0.23 ± 0.71)% for the spleen and liver, respectively. For all organs, the cumulative DVHs showed improvement after nonrigid registration and the normalized absolute error of differential DVHs ranged from 6.79% to

  2. Radiochromic film based dosimetry of image-guidance procedures on different radiotherapy modalities.

    PubMed

    Nobah, Ahmad; Aldelaijan, Saad; Devic, Slobodan; Tomic, Nada; Seuntjens, Jan; Al-Shabanah, Mohammed; Moftah, Belal

    2014-11-08

    In this work we compare doses from imaging procedures performed on today's state-of-the-art integrated imaging systems using a reference radiochromic film dosimetry system. Skin dose and dose profile measurements from different imaging systems were performed using radiochromic films at different anatomical sites on a humanoid RANDO phantom. EBT3 film was used to measure imaging doses from a TomoTherapy MVCT system, while XRQA2 film was used for dose measurements from kilovoltage imaging systems (CBCT on 21eX and TrueBeam Varian linear accelerators and CyberKnife stereoscopic orthogonal imagers). Maximum measured imaging doses in cGy at head, thorax, and pelvis regions were respectively 0.50, 1.01, and 4.91 for CBCT on 21eX, 0.38, 0.84, and 3.15 for CBCT on TrueBeam, 4.33, 3.86, and 6.50 for CyberKnife imagers, and 3.84, 1.90, and 2.09 for TomoTherapy MVCT. In addition, we have shown how an improved calibration system of XRQA2 film can achieve dose uncertainty level of better than 2% for doses above 0.25 cGy. In addition to simulation-based studies in literature, this study provides the radiation oncology team with data necessary to aid in their decision about imaging frequency for image-guided radiation therapy protocols.

  3. Dosimetric verification of radiation therapy including intensity modulated treatments, using an amorphous-silicon electronic portal imaging device

    NASA Astrophysics Data System (ADS)

    Chytyk-Praznik, Krista Joy

    Radiation therapy is continuously increasing in complexity due to technological innovation in delivery techniques, necessitating thorough dosimetric verification. Comparing accurately predicted portal dose images to measured images obtained during patient treatment can determine if a particular treatment was delivered correctly. The goal of this thesis was to create a method to predict portal dose images that was versatile and accurate enough to use in a clinical setting. All measured images in this work were obtained with an amorphous silicon electronic portal imaging device (a-Si EPID), but the technique is applicable to any planar imager. A detailed, physics-motivated fluence model was developed to characterize fluence exiting the linear accelerator head. The model was further refined using results from Monte Carlo simulations and schematics of the linear accelerator. The fluence incident on the EPID was converted to a portal dose image through a superposition of Monte Carlo-generated, monoenergetic dose kernels specific to the a-Si EPID. Predictions of clinical IMRT fields with no patient present agreed with measured portal dose images within 3% and 3 mm. The dose kernels were applied ignoring the geometrically divergent nature of incident fluence on the EPID. A computational investigation into this parallel dose kernel assumption determined its validity under clinically relevant situations. Introducing a patient or phantom into the beam required the portal image prediction algorithm to account for patient scatter and attenuation. Primary fluence was calculated by attenuating raylines cast through the patient CT dataset, while scatter fluence was determined through the superposition of pre-calculated scatter fluence kernels. Total dose in the EPID was calculated by convolving the total predicted incident fluence with the EPID-specific dose kernels. The algorithm was tested on water slabs with square fields, agreeing with measurement within 3% and 3 mm. The

  4. Computational high-resolution heart phantoms for medical imaging and dosimetry simulations

    NASA Astrophysics Data System (ADS)

    Gu, Songxiang; Gupta, Rajiv; Kyprianou, Iacovos

    2011-09-01

    Cardiovascular disease in general and coronary artery disease (CAD) in particular, are the leading cause of death worldwide. They are principally diagnosed using either invasive percutaneous transluminal coronary angiograms or non-invasive computed tomography angiograms (CTA). Minimally invasive therapies for CAD such as angioplasty and stenting are rendered under fluoroscopic guidance. Both invasive and non-invasive imaging modalities employ ionizing radiation and there is concern for deterministic and stochastic effects of radiation. Accurate simulation to optimize image quality with minimal radiation dose requires detailed, gender-specific anthropomorphic phantoms with anatomically correct heart and associated vasculature. Such phantoms are currently unavailable. This paper describes an open source heart phantom development platform based on a graphical user interface. Using this platform, we have developed seven high-resolution cardiac/coronary artery phantoms for imaging and dosimetry from seven high-quality CTA datasets. To extract a phantom from a coronary CTA, the relationship between the intensity distribution of the myocardium, the ventricles and the coronary arteries is identified via histogram analysis of the CTA images. By further refining the segmentation using anatomy-specific criteria such as vesselness, connectivity criteria required by the coronary tree and image operations such as active contours, we are able to capture excellent detail within our phantoms. For example, in one of the female heart phantoms, as many as 100 coronary artery branches could be identified. Triangular meshes are fitted to segmented high-resolution CTA data. We have also developed a visualization tool for adding stenotic lesions to the coronaries. The male and female heart phantoms generated so far have been cross-registered and entered in the mesh-based Virtual Family of phantoms with matched age/gender information. Any phantom in this family, along with user

  5. Superficial Dosimetry Imaging of Čerenkov Emission in Electron Beam Radiotherapy of Phantoms

    PubMed Central

    Zhang, Rongxiao; Fox, Colleen J.; Glaser, Adam K.; Gladstone, David J.; Pogue, Brian W.

    2014-01-01

    Čerenkov emission is generated from ionizing radiation in tissue above 264keV energy. This study presents the first examination of this optical emission as a surrogate for the absorbed superficial dose. Čerenkov emission was imaged from the surface of flat tissue phantoms irradiated with electrons, using a range of field sizes from 6cm×6cm to 20cm×20cm, incident angles from 0 to 50 degrees, and energies from 6 to 18 MeV. The Čerenkov images were compared with estimated superficial dose in phantoms from direct diode measurements, as well as calculations by Monte Carlo and the treatment planning system. Intensity images showed outstanding linear agreement (R2=0.97) with reference data of the known dose for energies from 6MeV to 18MeV. When orthogonal delivery was done, the in-plane and cross-plane dose distribution comparisons indicated very little difference (±2~4% differences) between the different methods of estimation as compared to Čerenkov light imaging. For an incident angle 50 degrees, the Čerenkov images and Monte Carlo simulation show excellent agreement with the diode data, but the treatment planning system (TPS) had at a larger error (OPT=±1~2%, Diode=±2~3%, TPS=±6~8% differences) as would be expected. The sampling depth of superficial dosimetry based on Čerenkov radiation has been simulated in layered skin model, showing the potential of sampling depth tuning by spectral filtering. Taken together, these measurements and simulations indicate that Čerenkov emission imaging might provide a valuable way to superficial dosimetry imaging from incident radiotherapy beams of electrons. PMID:23880473

  6. Superficial dosimetry imaging of Čerenkov emission in electron beam radiotherapy of phantoms

    NASA Astrophysics Data System (ADS)

    Zhang, Rongxiao; Fox, Colleen J.; Glaser, Adam K.; Gladstone, David J.; Pogue, Brian W.

    2013-08-01

    Čerenkov emission is generated from ionizing radiation in tissue above 264 keV energy. This study presents the first examination of this optical emission as a surrogate for the absorbed superficial dose. Čerenkov emission was imaged from the surface of flat tissue phantoms irradiated with electrons, using a range of field sizes from 6 cm × 6 cm to 20 cm × 20 cm, incident angles from 0° to 50°, and energies from 6 to 18 MeV. The Čerenkov images were compared with the estimated superficial dose in phantoms from direct diode measurements, as well as calculations by Monte Carlo and the treatment planning system. Intensity images showed outstanding linear agreement (R2 = 0.97) with reference data of the known dose for energies from 6 to 18 MeV. When orthogonal delivery was carried out, the in-plane and cross-plane dose distribution comparisons indicated very little difference (±2-4% differences) between the different methods of estimation as compared to Čerenkov light imaging. For an incident angle 50°, the Čerenkov images and Monte Carlo simulation show excellent agreement with the diode data, but the treatment planning system had a larger error (OPT = ±1˜2%, diode = ±2˜3%, TPS = ±6-8% differences) as would be expected. The sampling depth of superficial dosimetry based on Čerenkov radiation has been simulated in a layered skin model, showing the potential of sampling depth tuning by spectral filtering. Taken together, these measurements and simulations indicate that Čerenkov emission imaging might provide a valuable method of superficial dosimetry imaging from incident radiotherapy beams of electrons.

  7. Incorporating multislice imaging into x-ray CT polymer gel dosimetry

    SciTech Connect

    Johnston, H.; Hilts, M.; Jirasek, A.

    2015-04-15

    Purpose: To evaluate multislice computed tomography (CT) scanning for fast and reliable readout of radiation therapy (RT) dose distributions using CT polymer gel dosimetry (PGD) and to establish a baseline assessment of image noise and uniformity in an unirradiated gel dosimeter. Methods: A 16-slice CT scanner was used to acquire images through a 1 L cylinder filled with water. Additional images were collected using a single slice machine. The variability in CT number (N{sub CT}) associated with the anode heel effect was evaluated and used to define a new slice-by-slice background subtraction artifact removal technique for CT PGD. Image quality was assessed for the multislice system by evaluating image noise and uniformity. The agreement in N{sub CT} for slices acquired simultaneously using the multislice detector array was also examined. Further study was performed to assess the effects of increasing x-ray tube load on the constancy of measured N{sub CT} and overall scan time. In all cases, results were compared to the single slice machine. Finally, images were collected throughout the volume of an unirradiated gel dosimeter to quantify image noise and uniformity before radiation is delivered. Results: Slice-by-slice background subtraction effectively removes the variability in N{sub CT} observed across images acquired simultaneously using the multislice scanner and is the recommended background subtraction method when using a multislice CT system. Image noise was higher for the multislice system compared to the single slice scanner, but overall image quality was comparable between the two systems. Further study showed N{sub CT} was consistent across image slices acquired simultaneously using the multislice detector array for each detector configuration of the slice thicknesses examined. In addition, the multislice system was found to eliminate variations in N{sub CT} due to increasing x-ray tube load and reduce scanning time by a factor of 4 when compared to

  8. Reference radiochromic film dosimetry in kilovoltage photon beams during CBCT image acquisition

    SciTech Connect

    Tomic, Nada; Devic, Slobodan; DeBlois, Francois; Seuntjens, Jan

    2010-03-15

    Purpose: A common approach for dose assessment during cone beam computed tomography (CBCT) acquisition is to use thermoluminescent detectors for skin dose measurements (on patients or phantoms) or ionization chamber (in phantoms) for body dose measurements. However, the benefits of a daily CBCT image acquisition such as margin reduction in planning target volume and the image quality must be weighted against the extra dose received during CBCT acquisitions. Methods: The authors describe a two-dimensional reference dosimetry technique for measuring dose from CBCT scans using the on-board imaging system on a Varian Clinac-iX linear accelerator that employs the XR-QA radiochromic film model, specifically designed for dose measurements at low energy photons. The CBCT dose measurements were performed for three different body regions (head and neck, pelvis, and thorax) using humanoid Rando phantom. Results: The authors report on both surface dose and dose profiles measurements during clinical CBCT procedures carried out on a humanoid Rando phantom. Our measurements show that the surface doses per CBCT scan can range anywhere between 0.1 and 4.7 cGy, with the lowest surface dose observed in the head and neck region, while the highest surface dose was observed for the Pelvis spot light CBCT protocol in the pelvic region, on the posterior side of the Rando phantom. The authors also present results of the uncertainty analysis of our XR-QA radiochromic film dosimetry system. Conclusions: Radiochromic film dosimetry protocol described in this work was used to perform dose measurements during CBCT acquisitions with the one-sigma dose measurement uncertainty of up to 3% for doses above 1 cGy. Our protocol is based on film exposure calibration in terms of ''air kerma in air,'' which simplifies both the calibration procedure and reference dosimetry measurements. The results from a full Monte Carlo investigation of the dose conversion of measured XR-QA film dose at the surface into

  9. Digital Rocks Portal: a sustainable platform for imaged dataset sharing, translation and automated analysis

    NASA Astrophysics Data System (ADS)

    Prodanovic, M.; Esteva, M.; Hanlon, M.; Nanda, G.; Agarwal, P.

    2015-12-01

    Recent advances in imaging have provided a wealth of 3D datasets that reveal pore space microstructure (nm to cm length scale) and allow investigation of nonlinear flow and mechanical phenomena from first principles using numerical approaches. This framework has popularly been called "digital rock physics". Researchers, however, have trouble storing and sharing the datasets both due to their size and the lack of standardized image types and associated metadata for volumetric datasets. This impedes scientific cross-validation of the numerical approaches that characterize large scale porous media properties, as well as development of multiscale approaches required for correct upscaling. A single research group typically specializes in an imaging modality and/or related modeling on a single length scale, and lack of data-sharing infrastructure makes it difficult to integrate different length scales. We developed a sustainable, open and easy-to-use repository called the Digital Rocks Portal, that (1) organizes images and related experimental measurements of different porous materials, (2) improves access to them for a wider community of geosciences or engineering researchers not necessarily trained in computer science or data analysis. Once widely accepter, the repository will jumpstart productivity and enable scientific inquiry and engineering decisions founded on a data-driven basis. This is the first repository of its kind. We show initial results on incorporating essential software tools and pipelines that make it easier for researchers to store and reuse data, and for educators to quickly visualize and illustrate concepts to a wide audience. For data sustainability and continuous access, the portal is implemented within the reliable, 24/7 maintained High Performance Computing Infrastructure supported by the Texas Advanced Computing Center (TACC) at the University of Texas at Austin. Long-term storage is provided through the University of Texas System Research

  10. Denoising techniques combined to Monte Carlo simulations for the prediction of high-resolution portal images in radiotherapy treatment verification

    NASA Astrophysics Data System (ADS)

    Lazaro, D.; Barat, E.; Le Loirec, C.; Dautremer, T.; Montagu, T.; Guérin, L.; Batalla, A.

    2013-05-01

    This work investigates the possibility of combining Monte Carlo (MC) simulations to a denoising algorithm for the accurate prediction of images acquired using amorphous silicon (a-Si) electronic portal imaging devices (EPIDs). An accurate MC model of the Siemens OptiVue1000 EPID was first developed using the penelope code, integrating a non-uniform backscatter modelling. Two already existing denoising algorithms were then applied on simulated portal images, namely the iterative reduction of noise (IRON) method and the locally adaptive Savitzky-Golay (LASG) method. A third denoising method, based on a nonparametric Bayesian framework and called DPGLM (for Dirichlet process generalized linear model) was also developed. Performances of the IRON, LASG and DPGLM methods, in terms of smoothing capabilities and computation time, were compared for portal images computed for different values of the RMS pixel noise (up to 10%) in three different configurations, a heterogeneous phantom irradiated by a non-conformal 15 × 15 cm2 field, a conformal beam from a pelvis treatment plan, and an IMRT beam from a prostate treatment plan. For all configurations, DPGLM outperforms both IRON and LASG by providing better smoothing performances and demonstrating a better robustness with respect to noise. Additionally, no parameter tuning is required by DPGLM, which makes the denoising step very generic and easy to handle for any portal image. Concerning the computation time, the denoising of 1024 × 1024 images takes about 1 h 30 min, 2 h and 5 min using DPGLM, IRON, and LASG, respectively. This paper shows the feasibility to predict within a few hours and with the same resolution as real images accurate portal images, combining MC simulations with the DPGLM denoising algorithm.

  11. Automated detection of a prostate Ni-Ti stent in electronic portal images

    SciTech Connect

    Carl, Jesper; Nielsen, Henning; Nielsen, Jane; Lund, Bente; Larsen, Erik Hoejkjaer

    2006-12-15

    Planning target volumes (PTV) in fractionated radiotherapy still have to be outlined with wide margins to the clinical target volume due to uncertainties arising from daily shift of the prostate position. A recently proposed new method of visualization of the prostate is based on insertion of a thermo-expandable Ni-Ti stent. The current study proposes a new detection algorithm for automated detection of the Ni-Ti stent in electronic portal images. The algorithm is based on the Ni-Ti stent having a cylindrical shape with a fixed diameter, which was used as the basis for an automated detection algorithm. The automated method uses enhancement of lines combined with a grayscale morphology operation that looks for enhanced pixels separated with a distance similar to the diameter of the stent. The images in this study are all from prostate cancer patients treated with radiotherapy in a previous study. Images of a stent inserted in a humanoid phantom demonstrated a localization accuracy of 0.4-0.7 mm which equals the pixel size in the image. The automated detection of the stent was compared to manual detection in 71 pairs of orthogonal images taken in nine patients. The algorithm was successful in 67 of 71 pairs of images. The method is fast, has a high success rate, good accuracy, and has a potential for unsupervised localization of the prostate before radiotherapy, which would enable automated repositioning before treatment and allow for the use of very tight PTV margins.

  12. Application for internal dosimetry using biokinetic distribution of photons based on nuclear medicine images*

    PubMed Central

    Leal Neto, Viriato; Vieira, José Wilson; Lima, Fernando Roberto de Andrade

    2014-01-01

    Objective This article presents a way to obtain estimates of dose in patients submitted to radiotherapy with basis on the analysis of regions of interest on nuclear medicine images. Materials and Methods A software called DoRadIo (Dosimetria das Radiações Ionizantes [Ionizing Radiation Dosimetry]) was developed to receive information about source organs and target organs, generating graphical and numerical results. The nuclear medicine images utilized in the present study were obtained from catalogs provided by medical physicists. The simulations were performed with computational exposure models consisting of voxel phantoms coupled with the Monte Carlo EGSnrc code. The software was developed with the Microsoft Visual Studio 2010 Service Pack and the project template Windows Presentation Foundation for C# programming language. Results With the mentioned tools, the authors obtained the file for optimization of Monte Carlo simulations using the EGSnrc; organization and compaction of dosimetry results with all radioactive sources; selection of regions of interest; evaluation of grayscale intensity in regions of interest; the file of weighted sources; and, finally, all the charts and numerical results. Conclusion The user interface may be adapted for use in clinical nuclear medicine as a computer-aided tool to estimate the administered activity. PMID:25741101

  13. Optimization of image quality and dose for Varian aS500 electronic portal imaging devices (EPIDs)

    NASA Astrophysics Data System (ADS)

    McGarry, C. K.; Grattan, M. W. D.; Cosgrove, V. P.

    2007-12-01

    This study was carried out to investigate whether the electronic portal imaging (EPI) acquisition process could be optimized, and as a result tolerance and action levels be set for the PIPSPro QC-3V phantom image quality assessment. The aim of the optimization process was to reduce the dose delivered to the patient while maintaining a clinically acceptable image quality. This is of interest when images are acquired in addition to the planned patient treatment, rather than images being acquired using the treatment field during a patient's treatment. A series of phantoms were used to assess image quality for different acquisition settings relative to the baseline values obtained following acceptance testing. Eight Varian aS500 EPID systems on four matched Varian 600C/D linacs and four matched Varian 2100C/D linacs were compared for consistency of performance and images were acquired at the four main orthogonal gantry angles. Images were acquired using a 6 MV beam operating at 100 MU min-1 and the low-dose acquisition mode. Doses used in the comparison were measured using a Farmer ionization chamber placed at dmax in solid water. The results demonstrated that the number of reset frames did not have any influence on the image contrast, but the number of frame averages did. The expected increase in noise with corresponding decrease in contrast was also observed when reducing the number of frame averages. The optimal settings for the low-dose acquisition mode with respect to image quality and dose were found to be one reset frame and three frame averages. All patients at the Northern Ireland Cancer Centre are now imaged using one reset frame and three frame averages in the 6 MV 100 MU min-1 low-dose acquisition mode. Routine EPID QC contrast tolerance (±10) and action (±20) levels using the PIPSPro phantom based around expected values of 190 (Varian 600C/D) and 225 (Varian 2100C/D) have been introduced. The dose at dmax from electronic portal imaging has been reduced

  14. A novel method for patient exit and entrance dose prediction based on water equivalent path length measured with an amorphous silicon electronic portal imaging device

    NASA Astrophysics Data System (ADS)

    Kavuma, Awusi; Glegg, Martin; Metwaly, Mohamed; Currie, Garry; Elliott, Alex

    2010-01-01

    In vivo dosimetry is one of the quality assurance tools used in radiotherapy to monitor the dose delivered to the patient. Electronic portal imaging device (EPID) images for a set of solid water phantoms of varying thicknesses were acquired and the data fitted onto a quadratic equation, which relates the reduction in photon beam intensity to the attenuation coefficient and material thickness at a reference condition. The quadratic model is used to convert the measured grey scale value into water equivalent path length (EPL) at each pixel for any material imaged by the detector. For any other non-reference conditions, scatter, field size and MU variation effects on the image were corrected by relative measurements using an ionization chamber and an EPID. The 2D EPL is linked to the percentage exit dose table, for different thicknesses and field sizes, thereby converting the plane pixel values at each point into a 2D dose map. The off-axis ratio is corrected using envelope and boundary profiles generated from the treatment planning system (TPS). The method requires field size, monitor unit and source-to-surface distance (SSD) as clinical input parameters to predict the exit dose, which is then used to determine the entrance dose. The measured pixel dose maps were compared with calculated doses from TPS for both entrance and exit depth of phantom. The gamma index at 3% dose difference (DD) and 3 mm distance to agreement (DTA) resulted in an average of 97% passing for the square fields of 5, 10, 15 and 20 cm. The exit dose EPID dose distributions predicted by the algorithm were in better agreement with TPS-calculated doses than phantom entrance dose distributions.

  15. The Use of Gamma-Ray Imaging to Improve Portal Monitor Performance

    SciTech Connect

    Ziock, Klaus-Peter; Collins, Jeff; Fabris, Lorenzo; Gee, Timothy Felix; Goddard, James K; Habte Ghebretatios, Frezghi; Karnowski, Thomas Paul

    2008-01-01

    We have constructed a prototype, rapid-deployment portal monitor that uses visible-light and gamma-ray imaging to allow simultaneous monitoring of multiple lanes of traffic from the side of a roadway. Our Roadside Tracker uses automated target acquisition and tracking (TAT) software to identify and track vehicles in visible light images. The field of view of the visible camera overlaps with and is calibrated to that of a one-dimensional gamma-ray imager. The TAT code passes information on when vehicles enter and exit the system field of view and when they cross gamma-ray pixel boundaries. Based on this in-formation, the gamma-ray imager "harvests" the gamma-ray data specific to each vehicle, integrating its radiation signature for the entire time that it is in the field of view. In this fashion we are able to generate vehicle-specific radiation signatures and avoid source confusion problems that plague nonimaging approaches to the same problem.

  16. Feasibility study of patient positioning verification in electron beam radiotherapy with an electronic portal imaging device (EPID).

    PubMed

    Ramm, U; Köhn, J; Rodriguez Dominguez, R; Licher, J; Koch, N; Kara, E; Scherf, C; Rödel, C; Weiß, C

    2014-03-01

    The purpose of this study is to demonstrate the feasibility of verification and documentation in electron beam radiotherapy using the photon contamination detected with an electronic portal imaging device. For investigation of electron beam verification with an EPID, the portal images are acquired irradiating two different tissue equivalent phantoms at different electron energies. Measurements were performed on an Elekta SL 25 linear accelerator with an amorphous-Si electronic portal imaging device (EPID: iViewGT, Elekta Oncology Systems, Crawley, UK). As a measure of EPID image quality contrast (CR) and signal-to-noise ratio (SNR) are determined. For characterisation of the imaging of the EPID RW3 slabs and a Gammex 467 phantom with different material inserts are used. With increasing electron energy the intensity of photon contamination increases, yielding an increasing signal-to-noise ratio, but images are showing a decreasing contrast. As the signal-to-noise ratio saturates with increasing dose a minimum of 50 MUs is recommended. Even image quality depends on electron energy and diameter of the patient, the acquired results are mostly sufficient to assess the accuracy of beam positioning. In general, the online EPID acquisition has been demonstrated to be an effective electron beam verification and documentation method. The results are showing that this procedure can be recommended to be routinely and reliably done in patient treatment with electron beams.

  17. Dosimetry and image quality in digital mammography facilities in the State of Minas Gerais, Brazil

    NASA Astrophysics Data System (ADS)

    da Silva, Sabrina Donato; Joana, Geórgia Santos; Oliveira, Bruno Beraldo; de Oliveira, Marcio Alves; Leyton, Fernando; Nogueira, Maria do Socorro

    2015-11-01

    According to the National Register of Health Care Facilities (CNES), there are approximately 477 mammography systems operating in the state of Minas Gerais, Brazil, of which an estimated 200 are digital apparatus using mainly computerized radiography (CR) or direct radiography (DR) systems. Mammography is irreplaceable in the diagnosis and early detection of breast cancer, the leading cause of cancer death among women worldwide. A high standard of image quality alongside smaller doses and optimization of procedures are essential if early detection is to occur. This study aimed to determine dosimetry and image quality in 68 mammography services in Minas Gerais using CR or DR systems. The data of this study were collected between the years of 2011 and 2013. The contrast-to-noise ratio proved to be a critical point in the image production chain in digital systems, since 90% of services were not compliant in this regard, mainly for larger PMMA thicknesses (60 and 70 mm). Regarding the image noise, only 31% of these were compliant. The average glandular dose found is of concern, since more than half of the services presented doses above acceptable limits. Therefore, despite the potential benefits of using CR and DR systems, the employment of this technology has to be revised and optimized to achieve better quality image and reduce radiation dose as much as possible.

  18. Feasibility of fully automated detection of fiducial markers implanted into the prostate using electronic portal imaging: A comparison of methods

    SciTech Connect

    Harris, Emma J. . E-mail: eharris@icr.ac.uk; McNair, Helen A.; Evans, Phillip M.

    2006-11-15

    Purpose: To investigate the feasibility of fully automated detection of fiducial markers implanted into the prostate using portal images acquired with an electronic portal imaging device. Methods and Materials: We have made a direct comparison of 4 different methods (2 template matching-based methods, a method incorporating attenuation and constellation analyses and a cross correlation method) that have been published in the literature for the automatic detection of fiducial markers. The cross-correlation technique requires a-priory information from the portal images, therefore the technique is not fully automated for the first treatment fraction. Images of 7 patients implanted with gold fiducial markers (8 mm in length and 1 mm in diameter) were acquired before treatment (set-up images) and during treatment (movie images) using 1MU and 15MU per image respectively. Images included: 75 anterior (AP) and 69 lateral (LAT) set-up images and 51 AP and 83 LAT movie images. Using the different methods described in the literature, marker positions were automatically identified. Results: The method based upon cross correlation techniques gave the highest percentage detection success rate of 99% (AP) and 83% (LAT) set-up (1MU) images. The methods gave detection success rates of less than 91% (AP) and 42% (LAT) set-up images. The amount of a-priory information used and how it affects the way the techniques are implemented, is discussed. Conclusions: Fully automated marker detection in set-up images for the first treatment fraction is unachievable using these methods and that using cross-correlation is the best technique for automatic detection on subsequent radiotherapy treatment fractions.

  19. Characterization of a 2.5 MV inline portal imaging beam.

    PubMed

    Grafe, James L; Owen, Jennifer; Villarreal-Barajas, J Eduardo; Khan, Rao F H

    2016-01-01

    A new megavoltage (MV) energy was recently introduced on Varian TrueBeam linear accelerators for imaging applications. This work describes the experimental characterization of a 2.5 MV inline portal imaging beam for commissioning, routine clinical use, and quality assurance purposes. The beam quality of the 2.5 MV beam was determined by measuring a percent depth dose, PDD, in water phantom for 10 × 10 cm2 field at source-to-surface distance 100 cm with a CC13 ion chamber, plane parallel Markus chamber, and GafChromic EBT3 film. Absolute dosimetric output calibration of the beam was performed using a traceable calibrated ionization chamber, following the AAPM Task Group 51 procedure. EBT3 film measurements were also performed to measure entrance dose. The output stability of the imaging beam was monitored for five months. Coincidence of 2.5 MV imaging beam with 6 MV therapy beam was verified with hidden-target cubic phantom. Image quality was studied using the Leeds and QC3 phantom. The depth of maximum dose, dmax, and percent dose at 10 cm depth were, respectively, 5.7 mm and 51.7% for CC13, 6.1 mm and 51.9% for Markus chamber, and 5.1 mm and 51.9% for EBT3 film. The 2.5 MV beam quality is slightly inferior to that of a 60Co teletherapy beam; however, an estimated kQ of 1.00 was used for output calibration purposes. The beam output was found to be stable to within 1% over a five-month period. The relative entrance dose as measured with EBT3 films was 63%, compared to 23% for a clinical 6 MV beam for a 10 × 10 cm2 field. Overall coincidence of the 2.5 MV imaging beam with the 6 MV clinical therapy beam was within 0.2 mm. Image quality results for two com-monly used imaging phantoms were superior for the 2.5 MV beam when compared to the conventional 6 MV beam. The results from measurements on two TrueBeam accelerators show that 2.5 MV imaging beam is slightly softer than a therapeutic 60Co beam, it provides superior image quality than a 6 MV therapy beam, and has

  20. Comparison of MDCT protocols in trauma patients with suspected splenic injury: superior results with protocol that includes arterial and portal venous phase imaging

    PubMed Central

    Melikian, Raymond; Goldberg, Stephanie; Strife, Brian James; Halvorsen, Robert A.

    2016-01-01

    PURPOSE We aimed to determine which intravenous contrast-enhanced multidetector computed tomography (MDCT) protocol produced the most accurate results for the detection of splenic vascular injury in hemodynamically stable patients who had sustained blunt abdominal trauma. METHODS We retrospectively reviewed 88 patients from 2003 to 2011 who sustained blunt splenic trauma and underwent contrast-enhanced MDCT and subsequent angiography. Results of MDCT scans utilizing single phase (portal venous only, n=8), dual phase (arterial + portal venous or portal venous + delayed, n=42), or triple phase (arterial + portal venous + delayed, n=38) were compared with results of subsequent splenic angiograms for the detection of splenic vascular injury. RESULTS Dual phase imaging was more sensitive and accurate than single phase imaging (P = 0.016 and P = 0.029, respectively). When the subsets of dual phase imaging were compared, arterial + portal venous phase imaging was more sensitive and accurate than portal venous + delayed phase imaging (P = 0.005 and P = 0.002, respectively). Triple phase imaging was more accurate (P = 0.015) than dual phase; however, when compared with the dual phase subset of arterial + portal venous, there was no statistical difference in either sensitivity or accuracy. CONCLUSION Our results support the use of dual phase contrast-enhanced MDCT, which includes the arterial phase, in patients with suspected splenic injury and question the utility of obtaining a delayed sequence. PMID:27334296

  1. Skeletal dosimetry based on µCT images of trabecular bone: update and comparisons

    NASA Astrophysics Data System (ADS)

    Kramer, R.; Cassola, V. F.; Vieira, J. W.; Khoury, H. J.; de Oliveira Lira, C. A. B.; Robson Brown, K.

    2012-06-01

    Two skeletal dosimetry methods using µCT images of human bone have recently been developed: the paired-image radiation transport (PIRT) model introduced by researchers at the University of Florida (UF) in the US and the systematic-periodic cluster (SPC) method developed by researchers at the Federal University of Pernambuco in Brazil. Both methods use µCT images of trabecular bone (TB) to model spongiosa regions of human bones containing marrow cavities segmented into soft tissue volumes of active marrow (AM), trabecular inactive marrow and the bone endosteum (BE), which is a 50 µm thick layer of marrow on all TB surfaces and on cortical bone surfaces next to TB as well as inside the medullary cavities. With respect to the radiation absorbed dose, the AM and the BE are sensitive soft tissues for the induction of leukaemia and bone cancer, respectively. The two methods differ mainly with respect to the number of bone sites and the size of the µCT images used in Monte Carlo calculations and they apply different methods to simulate exposure from radiation sources located outside the skeleton. The PIRT method calculates dosimetric quantities in isolated human bones while the SPC method uses human bones embedded in the body of a phantom which contains all relevant organs and soft tissues. Consequently, the SPC method calculates absorbed dose to the AM and to the BE from particles emitted by radionuclides concentrated in organs or from radiation sources located outside the human body in one calculation step. In order to allow for similar calculations of AM and BE absorbed doses using the PIRT method, the so-called dose response functions (DRFs) have been developed based on absorbed fractions (AFs) of energy for electrons isotropically emitted in skeletal tissues. The DRFs can be used to transform the photon fluence in homogeneous spongiosa regions into absorbed dose to AM and BE. This paper will compare AM and BE AFs of energy from electrons emitted in skeletal

  2. A self-sufficient method for calibration of Varian electronic portal imaging device

    NASA Astrophysics Data System (ADS)

    Sun, Baozhou; Yaddanapudi, Sridhar; Goddu, Sreekrishna M.; Mutic, Sasa

    2015-01-01

    Electronic portal imaging device (EPID) is currently used for dosimetric verification of IMRT fields and linac quality assurance (QA). It is critical to understand the dosimetric response and perform an accurate and robust calibration of EPID. We present the implementation of an efficient method for the calibration and the validation of a Varian EPID, which relies only on data collected with that specific device. The calibration method is based on images obtained with five shifts of EPID panel. With this method, the relative gain (sensitivity) of each element of a detector matrix is calculated and applied on top of the calibration determined with the flood-field procedure. The calibration procedure was verified using a physical wedge inserted in the beam line and the corrected profile shows consistent results with the measurements using a calibrated 2D array. This method does not rely on the beam profile used in the flood-field calibration process, which allows EPID calibration in 10 minutes with no additional equipment compared to at least 2 hours to obtain beam profile and scanning beam equipment requirement with the conventional method.

  3. Portal Hypertension

    MedlinePlus

    ... Chronic Hepatitis C Additional Content Medical News Portal Hypertension By Steven K. Herrine, MD NOTE: This is ... Hepatic Encephalopathy Jaundice in Adults Liver Failure Portal Hypertension Portal hypertension is abnormally high blood pressure in ...

  4. Improving IMRT quality control efficiency using an amorphous silicon electronic portal imager

    SciTech Connect

    Budgell, G.J.; Zhang, Q.; Trouncer, R.J.; Mackay, R.I.

    2005-11-15

    An amorphous silicon electronic portal imaging device (EPID) has been investigated to determine its usefulness and efficiency for performing linear accelerator quality control checks specific to step and shoot intensity modulated radiation therapy (IMRT). Several dosimetric parameters were measured using the EPID: dose linearity and segment to segment reproducibility of low dose segments, and delivery accuracy of fractions of monitor units. Results were compared to ion chamber measurements. Low dose beam flatness and symmetry were tested by overlaying low dose beam profiles onto the profile from a stable high-dose exposure and visually checking for differences. Beam flatness and symmetry were also calculated and plotted against dose. Start-up reproducibility was tested by overlaying profiles from twenty successive two monitor unit segments. A method for checking the MLC leaf calibration was also tested, designed to be used on a daily or weekly basis, which consisted of summing the images from a series of matched fields. Daily images were co-registered with, then subtracted from, a reference image. A threshold image showing dose differences corresponding to >0.5 mm positional errors was generated and the number of pixels with such dose differences used as numerical parameter to which a tolerance can be applied. The EPID was found to be a sensitive relative dosemeter, able to resolve dose differences of 0.01 cGy. However, at low absolute doses a reproducible dosimetric nonlinearity of up to 7% due to image lag/ghosting effects was measured. It was concluded that although the EPID is suitable to measure segment to segment reproducibility and fractional monitor unit delivery accuracy, it is still less useful than an ion chamber as a tool for dosimetric checks. The symmetry/flatness test proved to be an efficient method of checking low dose profiles, much faster than any of the alternative methods. The MLC test was found to be extremely sensitive to sudden changes in

  5. Validation of a precision radiochromic film dosimetry system for quantitative two-dimensional imaging of acute exposure dose distributions.

    PubMed

    Dempsey, J F; Low, D A; Mutic, S; Markman, J; Kirov, A S; Nussbaum, G H; Williamson, J F

    2000-10-01

    We present an evaluation of the precision and accuracy of image-based radiochromic film (RCF) dosimetry performed using a commercial RCF product (Gafchromic MD-55-2, Nuclear Associates, Inc.) and a commercial high-spatial resolution (100 microm pixel size) He-Ne scanning-laser film-digitizer (Personal Densitometer, Molecular Dynamics, Inc.) as an optical density (OD) imaging system. The precision and accuracy of this dosimetry system are evaluated by performing RCF imaging dosimetry in well characterized conformal external beam and brachytherapy high dose-rate (HDR) radiation fields. Benchmarking of image-based RCF dosimetry is necessary due to many potential errors inherent to RCF dosimetry including: a temperature-dependent time evolution of RCF dose response; nonuniform response of RCF; and optical-polarization artifacts. In addition, laser-densitometer imaging artifacts can produce systematic OD measurement errors as large as 35% in the presence of high OD gradients. We present a RCF exposure and readout protocol that was developed for the accurate dosimetry of high dose rate (HDR) radiation sources. This protocol follows and expands upon the guidelines set forth by the American Association of Physicists in Medicine (AAPM) Task Group 55 report. Particular attention is focused on the OD imaging system, a scanning-laser film digitizer, modified to eliminate OD artifacts that were not addressed in the AAPM Task Group 55 report. RCF precision using this technique was evaluated with films given uniform 6 MV x-ray doses between 1 and 200 Gy. RCF absolute dose accuracy using this technique was evaluated by comparing RCF measurements to small volume ionization chamber measurements for conformal external-beam sources and an experimentally validated Monte Carlo photon-transport simulation code for a 192Ir brachytherapy source. Pixel-to-pixel standard deviations of uniformly irradiated films were less than 1% for doses between 10 and 150 Gy; between 1% and 5% for lower

  6. SU-E-J-237: Image Feature Based DRR and Portal Image Registration

    SciTech Connect

    Wang, X; Chang, J

    2014-06-01

    Purpose: Two-dimensional (2D) matching of the kV X-ray and digitally reconstructed radiography (DRR) images is an important setup technique for image-guided radiotherapy (IGRT). In our clinics, mutual information based methods are used for this purpose on commercial linear accelerators, but with often needs for manual corrections. This work proved the feasibility that feature based image transform can be used to register kV and DRR images. Methods: The scale invariant feature transform (SIFT) method was implemented to detect the matching image details (or key points) between the kV and DRR images. These key points represent high image intensity gradients, and thus the scale invariant features. Due to the poor image contrast from our kV image, direct application of the SIFT method yielded many detection errors. To assist the finding of key points, the center coordinates of the kV and DRR images were read from the DICOM header, and the two groups of key points with similar relative positions to their corresponding centers were paired up. Using these points, a rigid transform (with scaling, horizontal and vertical shifts) was estimated. We also artificially introduced vertical and horizontal shifts to test the accuracy of our registration method on anterior-posterior (AP) and lateral pelvic images. Results: The results provided a satisfactory overlay of the transformed kV onto the DRR image. The introduced vs. detected shifts were fit into a linear regression. In the AP image experiments, linear regression analysis showed a slope of 1.15 and 0.98 with an R2 of 0.89 and 0.99 for the horizontal and vertical shifts, respectively. The results are 1.2 and 1.3 with R2 of 0.72 and 0.82 for the lateral image shifts. Conclusion: This work provided an alternative technique for kV to DRR alignment. Further improvements in the estimation accuracy and image contrast tolerance are underway.

  7. Clinical practice and evaluation of electronic portal imaging device for VMAT quality assurance

    SciTech Connect

    Huang, Yen-Cho; Yeh, Chien-Yi; Yeh, Jih-Hsiang; Lo, Ching-Jung; Tsai, Ping-Fang; Hung, Chih-Hung; Tsai, Chieh-Sheng; Chen, Chen-Yuan

    2013-04-01

    Volumetric-modulated arc therapy (VMAT) is a novel extension of the intensity-modulated radiation therapy (IMRT) technique, which has brought challenges to dose verification. To perform VMAT pretreatment quality assurance, an electronic portal imaging device (EPID) can be applied. This study's aim was to evaluate EPID performance for VMAT dose verification. First, dosimetric characteristics of EPID were investigated. Then 10 selected VMAT dose plans were measured by EPID with the rotational method. The overall variation of EPID dosimetric characteristics was within 1.4% for VMAT. The film system serving as a conventional tool for verification showed good agreement both with EPID measurements ([94.1 ± 1.5]% with 3 mm/3% criteria) and treatment planning system (TPS) calculations ([97.4 ± 2.8]% with 3 mm/3% criteria). In addition, EPID measurements for VMAT presented good agreement with TPS calculations ([99.1 ± 0.6]% with 3 mm/3% criteria). The EPID system performed the robustness of potential error findings in TPS calculations and the delivery system. This study demonstrated that an EPID system can be used as a reliable and efficient quality assurance tool for VMAT dose verification.

  8. Clinical practice and evaluation of electronic portal imaging device for VMAT quality assurance.

    PubMed

    Huang, Yen-Cho; Yeh, Chien-Yi; Yeh, Jih-Hsiang; Lo, Ching-Jung; Tsai, Ping-Fang; Hung, Chih-Hung; Tsai, Chieh-Sheng; Chen, Chen-Yuan

    2013-01-01

    Volumetric-modulated arc therapy (VMAT) is a novel extension of the intensity-modulated radiation therapy (IMRT) technique, which has brought challenges to dose verification. To perform VMAT pretreatment quality assurance, an electronic portal imaging device (EPID) can be applied. This study's aim was to evaluate EPID performance for VMAT dose verification. First, dosimetric characteristics of EPID were investigated. Then 10 selected VMAT dose plans were measured by EPID with the rotational method. The overall variation of EPID dosimetric characteristics was within 1.4% for VMAT. The film system serving as a conventional tool for verification showed good agreement both with EPID measurements ([94.1 ± 1.5]% with 3 mm/3% criteria) and treatment planning system (TPS) calculations ([97.4 ± 2.8]% with 3 mm/3% criteria). In addition, EPID measurements for VMAT presented good agreement with TPS calculations ([99.1 ± 0.6]% with 3 mm/3% criteria). The EPID system performed the robustness of potential error findings in TPS calculations and the delivery system. This study demonstrated that an EPID system can be used as a reliable and efficient quality assurance tool for VMAT dose verification.

  9. Use of a line-pair resolution phantom for comprehensive quality assurance of electronic portal imaging devices based on fundamental imaging metrics

    SciTech Connect

    Gopal, Arun; Samant, Sanjiv S.

    2009-06-15

    Image guided radiation therapy solutions based on megavoltage computed tomography (MVCT) involve the extension of electronic portal imaging devices (EPIDs) from their traditional role of weekly localization imaging and planar dose mapping to volumetric imaging for 3D setup and dose verification. To sustain the potential advantages of MVCT, EPIDs are required to provide improved levels of portal image quality. Therefore, it is vital that the performance of EPIDs in clinical use is maintained at an optimal level through regular and rigorous quality assurance (QA). Traditionally, portal imaging QA has been carried out by imaging calibrated line-pair and contrast resolution phantoms and obtaining arbitrarily defined QA indices that are usually dependent on imaging conditions and merely indicate relative trends in imaging performance. They are not adequately sensitive to all aspects of image quality unlike fundamental imaging metrics such as the modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) that are widely used to characterize detector performance in radiographic imaging and would be ideal for QA purposes. However, due to the difficulty of performing conventional MTF measurements, they have not been used for routine clinical QA. The authors present a simple and quick QA methodology based on obtaining the MTF, NPS, and DQE of a megavoltage imager by imaging standard open fields and a bar-pattern QA phantom containing 2 mm thick tungsten line-pair bar resolution targets. Our bar-pattern based MTF measurement features a novel zero-frequency normalization scheme that eliminates normalization errors typically associated with traditional bar-pattern measurements at megavoltage x-ray energies. The bar-pattern QA phantom and open-field images are used in conjunction with an automated image analysis algorithm that quickly computes the MTF, NPS, and DQE of an EPID system. Our approach combines the fundamental advantages of

  10. Biokinetics and dosimetry of target-specific radiopharmaceuticals for molecular imaging and therapy

    NASA Astrophysics Data System (ADS)

    Ferro-Flores, Guillermina; Torres-García, Eugenio; Gonz&Ález-v&Ázquez, Armando; de Murphy, Consuelo Arteaga

    Molecular imaging techniques directly or indirectly monitor and record the spatiotemporal distribution of molecular or cellular processes for biochemical, biologic, diagnostic or therapeutic applications. 99mTc-HYNIC-TOC has shown high stability both in vitro and in vivo and rapid detection of somatostatin receptor-positive tumors. Therapies using radiolabeled anti-CD20 have demonstrated their efficacy in patients with B-cell non-Hodgkin's lymphoma (NHL). The aim of this study was to establish biokinetic models for 99mTc-HYNIC-TOC and 188Re-anti-CD20 and to evaluate their dosimetry as target-specific radiopharmaceuticals. The OLINDA/EXM code was used to calculate patient-specific internal radiation dose estimates. 99mTc-HYNIC-TOC images showed an average tumor/blood ratio of 4.3±0.7 in receptor-positive tumors with an average effective dose of 4.4 mSv. Dosimetric studies indicated that after administration of 5.8 to 7.5 GBq of 188Re-anti-CD20 the absorbed dose to total body would be 0.75 Gy which corresponds to the recommended dose for NHL therapies.

  11. A study of Winston-Lutz test on two different electronic portal imaging devices and with low energy imaging.

    PubMed

    Ravindran, Paul B

    2016-09-01

    Stereotactic radiosurgery requires sub-millimetre accuracy in patient positioning and target localization. Therefore, verification of the linear accelerator (linac) isocentre and the laser alignment to the isocentre is performed in some clinics prior to the treatment using the Winston-Lutz (W-L) test with films and more recently with images obtained using the electronic portal imaging devices (EPID). The W-L test is performed by acquiring EPID images of a radio-opaque ball of 6 mm diameter (the W-L phantom) placed at the isocentre of the linac at various gantry and table angles, with a predefined small square or circular radiation beam. In this study, the W-L test was performed on two linacs having EPIDs of different size and resolution, viz, a TrueBeam™ linac with aS1000 EPID of size 40 × 30 cm(2) with 1024 × 768 pixel resolution and an EDGE™ linac having an EPID of size 43 × 43 cm(2) with pixel resolution of 1280 × 1280. In order to determine the displacement of the radio-opaque ball centre from the radiation beam centre of the W-L test, an in-house MATLAB™ image processing code was developed using morphological operations. The displacement in radiation beam centre at each gantry and couch position was obtained by determining the distance between the radiation field centre and the radio-opaque ball centre for every image. Since the MATLAB code was based on image processing that was dependent on the image contrast and resolution, the W-L test was also compared for images obtained with different beam energies. The W-L tests were performed for 6 and 8 MV beams on the TrueBeam™ linac and for 2.5 and 6 MV beams on the EDGE™ linac with a higher resolution EPID. It was observed that the images obtained with the EPID of higher resolution resulted in same accuracy in the determination of the displacement between the centres of the radio-opaque ball and the radiation beam, and significant difference was not observed with images acquired with

  12. Bilharzial portal fibrosis: an important cause of portal hypertension.

    PubMed Central

    Carruthers, R. H.; Sinha, P.

    1978-01-01

    Thirty consecutive cases of portal hypertension seen in a surgical unit in Lusaka, Zambia, are reported. Of these cases 70% were due to portal fibrosis caused by Schistosoma mansoni infestation. Portacaval shunting was undertaken in most cases. Patients with portal fibrosis responded more favourably to portal decompression than did patients with cirrhosis. It is probable that the condition is more common than is generally reconigzed in areas where S. mansoni infestation is endemic. Images Fig. 1 Fig. 2 PMID:626472

  13. Evaluation of radiochromic gel dosimetry and polymer gel dosimetry in a clinical dose verification

    NASA Astrophysics Data System (ADS)

    Vandecasteele, Jan; De Deene, Yves

    2013-09-01

    A quantitative comparison of two full three-dimensional (3D) gel dosimetry techniques was assessed in a clinical setting: radiochromic gel dosimetry with an in-house developed optical laser CT scanner and polymer gel dosimetry with magnetic resonance imaging (MRI). To benchmark both gel dosimeters, they were exposed to a 6 MV photon beam and the depth dose was compared against a diamond detector measurement that served as golden standard. Both gel dosimeters were found accurate within 4% accuracy. In the 3D dose matrix of the radiochromic gel, hotspot dose deviations up to 8% were observed which are attributed to the fabrication procedure. The polymer gel readout was shown to be sensitive to B0 field and B1 field non-uniformities as well as temperature variations during scanning. The performance of the two gel dosimeters was also evaluated for a brain tumour IMRT treatment. Both gel measured dose distributions were compared against treatment planning system predicted dose maps which were validated independently with ion chamber measurements and portal dosimetry. In the radiochromic gel measurement, two sources of deviations could be identified. Firstly, the dose in a cluster of voxels near the edge of the phantom deviated from the planned dose. Secondly, the presence of dose hotspots in the order of 10% related to inhomogeneities in the gel limit the clinical acceptance of this dosimetry technique. Based on the results of the micelle gel dosimeter prototype presented here, chemical optimization will be subject of future work. Polymer gel dosimetry is capable of measuring the absolute dose in the whole 3D volume within 5% accuracy. A temperature stabilization technique is incorporated to increase the accuracy during short measurements, however keeping the temperature stable during long measurement times in both calibration phantoms and the volumetric phantom is more challenging. The sensitivity of MRI readout to minimal temperature fluctuations is demonstrated which

  14. A two-dimensional matrix correction for off-axis portal dose prediction errors

    SciTech Connect

    Bailey, Daniel W.; Kumaraswamy, Lalith; Bakhtiari, Mohammad; Podgorsak, Matthew B.

    2013-05-15

    Purpose: This study presents a follow-up to a modified calibration procedure for portal dosimetry published by Bailey et al. ['An effective correction algorithm for off-axis portal dosimetry errors,' Med. Phys. 36, 4089-4094 (2009)]. A commercial portal dose prediction system exhibits disagreement of up to 15% (calibrated units) between measured and predicted images as off-axis distance increases. The previous modified calibration procedure accounts for these off-axis effects in most regions of the detecting surface, but is limited by the simplistic assumption of radial symmetry. Methods: We find that a two-dimensional (2D) matrix correction, applied to each calibrated image, accounts for off-axis prediction errors in all regions of the detecting surface, including those still problematic after the radial correction is performed. The correction matrix is calculated by quantitative comparison of predicted and measured images that span the entire detecting surface. The correction matrix was verified for dose-linearity, and its effectiveness was verified on a number of test fields. The 2D correction was employed to retrospectively examine 22 off-axis, asymmetric electronic-compensation breast fields, five intensity-modulated brain fields (moderate-high modulation) manipulated for far off-axis delivery, and 29 intensity-modulated clinical fields of varying complexity in the central portion of the detecting surface. Results: Employing the matrix correction to the off-axis test fields and clinical fields, predicted vs measured portal dose agreement improves by up to 15%, producing up to 10% better agreement than the radial correction in some areas of the detecting surface. Gamma evaluation analyses (3 mm, 3% global, 10% dose threshold) of predicted vs measured portal dose images demonstrate pass rate improvement of up to 75% with the matrix correction, producing pass rates that are up to 30% higher than those resulting from the radial correction technique alone. As in

  15. Muon tomography imaging algorithms for nuclear threat detection inside large volume containers with the Muon Portal detector

    NASA Astrophysics Data System (ADS)

    Riggi, S.; Antonuccio-Delogu, V.; Bandieramonte, M.; Becciani, U.; Costa, A.; La Rocca, P.; Massimino, P.; Petta, C.; Pistagna, C.; Riggi, F.; Sciacca, E.; Vitello, F.

    2013-11-01

    Muon tomographic visualization techniques try to reconstruct a 3D image as close as possible to the real localization of the objects being probed. Statistical algorithms under test for the reconstruction of muon tomographic images in the Muon Portal Project are discussed here. Autocorrelation analysis and clustering algorithms have been employed within the context of methods based on the Point Of Closest Approach (POCA) reconstruction tool. An iterative method based on the log-likelihood approach was also implemented. Relative merits of all such methods are discussed, with reference to full GEANT4 simulations of different scenarios, incorporating medium and high-Z objects inside a container.

  16. Phantom dosimetry and image quality of i-CAT FLX cone-beam computed tomography

    PubMed Central

    Ludlow, John B.; Walker, Cameron

    2013-01-01

    Introduction Increasing use of cone-beam computed tomography in orthodontics has been coupled with heightened concern with the long-term risks of x-ray exposure in orthodontic populations. An industry response to this has been to offer low-exposure alternative scanning options in newer cone-beam computed tomography models. Methods Effective doses resulting from various combinations of field size, and field location comparing child and adult anthropomorphic phantoms using the recently introduced i-CAT FLX cone-beam computed tomography unit were measured with Optical Stimulated Dosimetry using previously validated protocols. Scan protocols included High Resolution (360° rotation, 600 image frames, 120 kVp, 5 mA, 7.4 sec), Standard (360°, 300 frames, 120 kVp, 5 mA, 3.7 sec), QuickScan (180°, 160 frames, 120 kVp, 5 mA, 2 sec) and QuickScan+ (180°, 160 frames, 90 kVp, 3 mA, 2 sec). Contrast-to-noise ratio (CNR) was calculated as a quantitative measure of image quality for the various exposure options using the QUART DVT phantom. Results Child phantom doses were on average 36% greater than Adult phantom doses. QuickScan+ protocols resulted in significantly lower doses than Standard protocols for child (p=0.0167) and adult (p=0.0055) phantoms. 13×16 cm cephalometric fields of view ranged from 11–85 μSv in the adult phantom and 18–120 μSv in the child for QuickScan+ and Standard protocols respectively. CNR was reduced by approximately 2/3rds comparing QuickScan+ to Standard exposure parameters. Conclusions QuickScan+ effective doses are comparable to conventional panoramic examinations. Significant dose reductions are accompanied by significant reductions in image quality. However, this trade-off may be acceptable for certain diagnostic tasks such as interim assessment of treatment results. PMID:24286904

  17. Characterization of a new polymer gel for radiosurgery dosimetry using Magnetic Resonance Imaging

    NASA Astrophysics Data System (ADS)

    Petrokokkinos, L.; Kozicki, M.; Pantelis, E.; Antypas, C.; Fijuth, J.; Karaiskos, P.; Sakelliou, L.; Seimenis, I.

    2009-06-01

    The VIPAR polymer gel dosimeter formulation was modified in an effort to eliminate the need for deoxygenation in the manufacturing procedure while preserving its favorable characteristics of dose rate independence and a wide dose response range. Aiming at an adequate dose sensitivity and the extension of dose response in the low dose region to facilitate the dose verification of radiosurgery applications where narrow beams are employed and steep dose gradients are involved, the new formulation consists of 8% N-Vinylpyrrolidone, 7.5% gelatine, 4% N,N'-methylenebisacrylamide, as well as of 0.0008% Copper Sulfate and 0.007% Ascorbic Acid as oxygen scavengers. To study the dose-R2 response, dose rate dependence and ``edge effect'' behaviour of the new formulation, one batch of two gel filled glass vials was prepared. Before MR Imaging, one vial was irradiated with a brachytherapy source while the other one was irradiated using circular CyberKnife radiation fields of 60, 10, 7.5 and 5 mm in diameter. Results of this study suggest that the new gel dosimeter responds linearly in the dose range of about 3 to 30 Gy, whilst the full dose response range exceeds the maximum delivered dose of 50 Gy. No dose rate dependence was observed for the new gel, while Cyberknife dosimetry results in the form of stereotactic field size and penumbra measurements suggest that the new formulation could be effective in the dose verification of demanding radiosurgery techniques.

  18. A comprehensive tool for image-based generation of fetus and pregnant women mesh models for numerical dosimetry studies

    NASA Astrophysics Data System (ADS)

    Dahdouh, S.; Varsier, N.; Serrurier, A.; De la Plata, J.-P.; Anquez, J.; Angelini, E. D.; Wiart, J.; Bloch, I.

    2014-08-01

    Fetal dosimetry studies require the development of accurate numerical 3D models of the pregnant woman and the fetus. This paper proposes a 3D articulated fetal growth model covering the main phases of pregnancy and a pregnant woman model combining the utero-fetal structures and a deformable non-pregnant woman body envelope. The structures of interest were automatically or semi-automatically (depending on the stage of pregnancy) segmented from a database of images and surface meshes were generated. By interpolating linearly between fetal structures, each one can be generated at any age and in any position. A method is also described to insert the utero-fetal structures in the maternal body. A validation of the fetal models is proposed, comparing a set of biometric measurements to medical reference charts. The usability of the pregnant woman model in dosimetry studies is also investigated, with respect to the influence of the abdominal fat layer.

  19. In vivo dosimetry in external beam radiotherapy

    SciTech Connect

    Mijnheer, Ben; Beddar, Sam; Izewska, Joanna; Reft, Chester

    2013-07-15

    In vivo dosimetry (IVD) is in use in external beam radiotherapy (EBRT) to detect major errors, to assess clinically relevant differences between planned and delivered dose, to record dose received by individual patients, and to fulfill legal requirements. After discussing briefly the main characteristics of the most commonly applied IVD systems, the clinical experience of IVD during EBRT will be summarized. Advancement of the traditional aspects of in vivo dosimetry as well as the development of currently available and newly emerging noninterventional technologies are required for large-scale implementation of IVD in EBRT. These new technologies include the development of electronic portal imaging devices for 2D and 3D patient dosimetry during advanced treatment techniques, such as IMRT and VMAT, and the use of IVD in proton and ion radiotherapy by measuring the decay of radiation-induced radionuclides. In the final analysis, we will show in this Vision 20/20 paper that in addition to regulatory compliance and reimbursement issues, the rationale for in vivo measurements is to provide an accurate and independent verification of the overall treatment procedure. It will enable the identification of potential errors in dose calculation, data transfer, dose delivery, patient setup, and changes in patient anatomy. It is the authors' opinion that all treatments with curative intent should be verified through in vivo dose measurements in combination with pretreatment checks.

  20. Use of an amorphous silicon electronic portal imaging device for multileaf collimator quality control and calibration.

    PubMed

    Baker, S J K; Budgell, G J; MacKay, R I

    2005-04-01

    Multileaf collimator (MLC) calibration and quality control is a time-consuming procedure typically involving the processing, scanning and analysis of films to measure leaf and collimator positions. Faster and more reliable calibration procedures are required for these tasks, especially with the introduction of intensity modulated radiotherapy which requires more frequent checking and finer positional leaf tolerances than previously. A routine quality control (QC) technique to measure MLC leaf bank gain and offset, as well as minor offsets (individual leaf position relative to a reference leaf), using an amorphous silicon electronic portal imaging device (EPID) has been developed. The technique also tests the calibration of the primary and back-up collimators. A detailed comparison between film and EPID measurements has been performed for six linear accelerators (linacs) equipped with MLC and amorphous silicon EPIDs. Measurements of field size from 4 to 24 cm with the EPID were systematically smaller than film measurements over all field sizes by 0.4 mm for leaves/back-up collimators and by 0.2 mm for conventional collimators. This effect is due to the gain calibration correction applied by the EPID, resulting in a 'flattening' of primary beam profiles. Linac dependent systematic differences of up to 0.5 mm in individual leaf/collimator positions were also found between EPID and film measurements due to the difference between the mechanical and radiation axes of rotation. When corrections for these systematic differences were applied, the residual random differences between EPID and film were 0.23 mm and 0.26 mm (1 standard deviation) for field size and individual leaf/back-up collimator position, respectively. Measured gains (over a distance of 220 mm) always agreed within 0.4 mm with a standard deviation of 0.17 mm. Minor offset measurements gave a mean agreement between EPID and film of 0.01+/-0.10 mm (1 standard deviation) after correction for the tilt of the

  1. Localization of linked {sup 125}I seeds in postimplant TRUS images for prostate brachytherapy dosimetry

    SciTech Connect

    Xue Jinyu . E-mail: Jinyu.Xue@mail.tju.edu; Waterman, Frank; Handler, Jay; Gressen, Eric

    2005-07-01

    Purpose: To demonstrate that {sup 125}I seeds can be localized in transrectal ultrasound (TRUS) images obtained with a high-resolution probe when the implant is performed with linked seeds and spacers. Adequate seed localization is essential to the implementation of TRUS-based intraoperative dosimetry for prostate brachytherapy. Methods and Materials: Thirteen preplanned peripherally loaded prostate implants were performed using {sup 125}I seeds and spacers linked together in linear arrays that prevent seed migration and maintain precise seed spacing. A set of two-dimensional transverse images spaced at 0.50-cm intervals were obtained with a high-resolution TRUS probe at the conclusion of the procedure with the patient still under anesthesia. The image set extended from 1.0 cm superior to the base to 1.0 cm inferior to the apex. The visible echoes along each needle track were first localized and then compared with the known construction of the implanted array. The first step was to define the distal and proximal ends of each array. The visible echoes were then identified as seeds or spacers from the known sequence of the array. The locations of the seeds that did not produce a visible echo were interpolated from their known position in the array. A CT scan was obtained after implantation for comparison with the TRUS images. Results: On average, 93% (range, 86-99%) of the seeds were visible in the TRUS images. However, it was possible to localize 100% of the seeds in each case, because the locations of the missing seeds could be determined from the known construction of the arrays. Two factors complicated the interpretation of the TRUS images. One was that the spacers also produced echoes. Although weak and diffuse, these echoes could be mistaken for seeds. The other was that the number of echoes along a needle track sometimes exceeded the number of seeds and spacers implanted. This was attributed to the overall length of the array, which was approximately 0.5 cm

  2. The Effect of E-Portal System on Corporate Image of Universities

    ERIC Educational Resources Information Center

    Tunji, Oyedepo; Nelson, Okorie

    2011-01-01

    Internet connectivity in tertiary institutions in Africa has been summarized in three characteristics-- too little, too expensive and poorly managed (African Tertiary Institutions Connectivity Survey (ATICS), 2006 report). The Internet portal system offers educational organizations the ability to track students needs and promote their programs and…

  3. Clinical implementation and rapid commissioning of an EPID based in-vivo dosimetry system

    NASA Astrophysics Data System (ADS)

    Hanson, Ian M.; Hansen, Vibeke N.; Olaciregui-Ruiz, Igor; van Herk, Marcel

    2014-10-01

    Using an Electronic Portal Imaging Device (EPID) to perform in-vivo dosimetry is one of the most effective and efficient methods of verifying the safe delivery of complex radiotherapy treatments. Previous work has detailed the development of an EPID based in-vivo dosimetry system that was subsequently used to replace pre-treatment dose verification of IMRT and VMAT plans. Here we show that this system can be readily implemented on a commercial megavoltage imaging platform without modification to EPID hardware and without impacting standard imaging procedures. The accuracy and practicality of the EPID in-vivo dosimetry system was confirmed through a comparison with traditional TLD in-vivo measurements performed on five prostate patients. The commissioning time required for the EPID in-vivo dosimetry system was initially prohibitive at approximately 10 h per linac. Here we present a method of calculating linac specific EPID dosimetry correction factors that allow a single energy specific commissioning model to be applied to EPID data from multiple linacs. Using this method reduced the required per linac commissioning time to approximately 30 min. The validity of this commissioning method has been tested by analysing in-vivo dosimetry results of 1220 patients acquired on seven linacs over a period of 5 years. The average deviation between EPID based isocentre dose and expected isocentre dose for these patients was (-0.7  ±  3.2)%. EPID based in-vivo dosimetry is now the primary in-vivo dosimetry tool used at our centre and has replaced nearly all pre-treatment dose verification of IMRT treatments.

  4. An image-based skeletal dosimetry model for the ICRP reference newborn—internal electron sources

    NASA Astrophysics Data System (ADS)

    Pafundi, Deanna; Rajon, Didier; Jokisch, Derek; Lee, Choonsik; Bolch, Wesley

    2010-04-01

    In this study, a comprehensive electron dosimetry model of newborn skeletal tissues is presented. The model is constructed using the University of Florida newborn hybrid phantom of Lee et al (2007 Phys. Med. Biol. 52 3309-33), the newborn skeletal tissue model of Pafundi et al (2009 Phys. Med. Biol. 54 4497-531) and the EGSnrc-based Paired Image Radiation Transport code of Shah et al (2005 J. Nucl. Med. 46 344-53). Target tissues include the active bone marrow (surrogate tissue for hematopoietic stem cells), shallow marrow (surrogate tissue for osteoprogenitor cells) and unossified cartilage (surrogate tissue for chondrocytes). Monoenergetic electron emissions are considered over the energy range 1 keV to 10 MeV for the following source tissues: active marrow, trabecular bone (surfaces and volumes), cortical bone (surfaces and volumes) and cartilage. Transport results are reported as specific absorbed fractions according to the MIRD schema and are given as skeletal-averaged values in the paper with bone-specific values reported in both tabular and graphic format as electronic annexes (supplementary data). The method utilized in this work uniquely includes (1) explicit accounting for the finite size and shape of newborn ossification centers (spongiosa regions), (2) explicit accounting for active and shallow marrow dose from electron emissions in cortical bone as well as sites of unossified cartilage, (3) proper accounting of the distribution of trabecular and cortical volumes and surfaces in the newborn skeleton when considering mineral bone sources and (4) explicit consideration of the marrow cellularity changes for active marrow self-irradiation as applicable to radionuclide therapy of diseased marrow in the newborn child.

  5. Development of a new positron emission tomography tracer for targeting tumor angiogenesis: synthesis, small animal imaging, and radiation dosimetry.

    PubMed

    Patterson, Cam; Frederick, C Brandon; Yuan, Hong; Dyer, Laura A; Lockyer, Pamela; Lalush, David S; Veleva, Anka N

    2013-05-15

    Angiogenesis plays a key role in cancer progression and correlates with disease aggressiveness and poor clinical outcomes. Affinity ligands discovered by screening phage display random peptide libraries can be engineered to molecularly target tumor blood vessels for noninvasive imaging and early detection of tumor aggressiveness. In this study, we tested the ability of a phage-display-selected peptide sequence recognizing specifically bone marrow- derived pro-angiogenic tumor-homing cells, the QFP-peptide, radiolabeled with 64Cu radioisotope to selectively image tumor vasculature in vivo by positron emission tomography (PET). To prepare the targeted PET tracer we modified QFP-phage with the DOTA chelator and radiolabeled the purified QFP-phage-DOTA intermediate with 64Cu to obtain QFP-targeted radioconjugate with high radiopharmaceutical yield and specific activity. We evaluated the new PET tracer in vivo in a subcutaneous (s.c.) Lewis lung carcinoma (LLC) mouse model and conducted tissue distribution, small animal PET/CT imaging study, autoradiography, histology, fluorescence imaging, and dosimetry assessments. The results from this study show that, in the context of the s.c. LLC immunocompetent mouse model, the QFP-tracer can target tumor blood vessels selectively. However, further optimization of the biodistribution and dosimetry profile of the tracer is necessary to ensure efficient radiopharmaceutical applications enabled by the biological specificity of the QFP-peptide.

  6. Preclinical acute toxicity, biodistribution, pharmacokinetics, radiation dosimetry and microPET imaging studies of [(18)F]fluorocholine in mice.

    PubMed

    Silveira, Marina B; Ferreira, Soraya M Z M D; Nascimento, Leonardo T C; Costa, Flávia M; Mendes, Bruno M; Ferreira, Andrea V; Malamut, Carlos; Silva, Juliana B; Mamede, Marcelo

    2016-10-01

    [(18)F]Fluorocholine ([(18)F]FCH) has been proven to be effective in prostate cancer. Since [(18)F]FCH is classified as a new radiopharmaceutical in Brazil, preclinical safety and efficacy data are required to support clinical trials and to obtain its approval. The aim of this work was to perform acute toxicity, biodistribution, pharmacokinetics, radiation dosimetry and microPET imaging studies of [(18)F]FCH. The results could support its use in nuclear medicine as an important piece of work for regulatory in Brazil.

  7. Preclinical acute toxicity, biodistribution, pharmacokinetics, radiation dosimetry and microPET imaging studies of [(18)F]fluorocholine in mice.

    PubMed

    Silveira, Marina B; Ferreira, Soraya M Z M D; Nascimento, Leonardo T C; Costa, Flávia M; Mendes, Bruno M; Ferreira, Andrea V; Malamut, Carlos; Silva, Juliana B; Mamede, Marcelo

    2016-10-01

    [(18)F]Fluorocholine ([(18)F]FCH) has been proven to be effective in prostate cancer. Since [(18)F]FCH is classified as a new radiopharmaceutical in Brazil, preclinical safety and efficacy data are required to support clinical trials and to obtain its approval. The aim of this work was to perform acute toxicity, biodistribution, pharmacokinetics, radiation dosimetry and microPET imaging studies of [(18)F]FCH. The results could support its use in nuclear medicine as an important piece of work for regulatory in Brazil. PMID:27509594

  8. Dosimetry of an iodine-123-labeled tropane to image dopamine transporters

    SciTech Connect

    Mozley, P.D.; Stubbs, J.B.; Kim, H.J.

    1996-01-01

    N-(3-iodopropen-2-yl)-2{beta}-carbomethoxy-3{beta}(4-chlorophenyl)tropane (IPT) is an analog of cocaine that selectively binds the presynaptic dopamine transporter. The present study sought to measure the radiation dosimetry of IPT in seven healthy human volunteers. Dynamic renal scans were acquired immediately after the intravenous administration of 165 {+-} 16 MBq (4.45 {+-} 0.42 mCi) of [{sup 123}I]IPT. Between 7 and 12 sets of whole-body scans were acquired over the next 24 hr. The 24-hr renal excretion fractions were measured from conjugate emission scans of 7-11 discreet voided urine specimens. The fraction of the administered dose in 11 organs and each urine specimen was quantified from the attenuation-corrected geometric mean counts in opposing views. Subject-specific residence times were evaluated for each subject independently by fitting the time-activity curves to a multicompartmental model. The radiation doses were estimated with the MIRD technique from the residence times for each subject individually before any results were averaged. The findings showed that IPT was excreted rapidly by the renal system. There were no reservoirs of retained activity outside the basal ganglia, where SPECT images in these subjects showed that the mean ratio of caudate to calcarine cortex averaged 25:1 at 3 hr after injection (range 19.6-32 hr). The basal ganglia received a radiation dose of 0.028 mGy/MBq (0.10 rad/mCi). The dose-limiting organ in men was the stomach, which received an estimated 0.11 mGy/MBq (0.37 rad/mCi). In women, the critical organ was the urinary bladder at 0.14 mGy/MBq (0.51 rad/mCi). Relatively high-contrast images of the presynaptic dopamine transporters in the basal ganglia can be acquired with 185 MBq (5 mCi) of [{sup 123}I]IPT. The radiation exposure that results is significantly less than the maximum allowed by current safety guidelines for research volunteers. 33 refs., 4 figs., 3 tabs.

  9. SU-D-BRF-07: Ultrasound and Fluoroscopy Based Intraoperative Image-Guidance System for Dynamic Dosimetry in Prostate Brachytherapy

    SciTech Connect

    Kuo, N; Le, Y; Deguet, A; Prince, J; Song, D; Lee, J; Dehghan, E; Burdette, E; Fichtinger, G

    2014-06-01

    Purpose: Prostate brachytherapy is a common treatment method for low-risk prostate cancer patients. Intraoperative treatment planning is known to improve the treatment procedure and the outcome. The current limitation of intraoperative treatment planning is the inability to localize the seeds in relation to the prostate. We developed an image-guidance system to fulfill this need to achieve intraoperative dynamic dosimetry in prostate brachytherapy. Methods: Our system is based on standard imaging equipments available in the operating room, including the transrectal ultrasound (TRUS) and the mobile C-arm. A simple fiducial is added to compute the C-arm pose. Three fluoroscopic images and an ultrasound volume of the seeds and the prostate are acquired and processed by four image processing algorithms: seed segmentation, fiducial detection with pose estimation, seed reconstruction, and seeds-to-TRUS registration. The updated seed positions allow the physician to assess the quality of implantation and dynamically adjust the treatment plan during the course of surgery to achieve improved exit dosimetry. Results: The system was tested on 10 phantoms and 37 patients. Seed segmentation resulted in a 1% false negative and 2% false positive rates. Fiducial detection with pose estimation resulted in a detection rate of 98%. Seed reconstruction had a mean reconstruction error of 0.4 mm. Seeds-to-TRUS registration had a mean registration error of 1.3 mm. The total processing time from image acquisition to registration was approximately 1 minute. Conclusion: We present an image-guidance system for intraoperative dynamic dosimetry in prostate brachytherapy. Using standard imaging equipments and a simple fiducial, our system can be easily adopted in any clinics. Robust image processing algorithms enable accurate and fast computation of the delivered dose. Especially, the system enables detection of possible hot/cold spots during the surgery, allowing the physician to address these

  10. Development of a one-stop beam verification system using electronic portal imaging devices for routine quality assurance

    SciTech Connect

    Lim, Sangwook; Ma, Sun Young; Jeung, Tae Sig; Yi, Byong Yong; Lee, Sang Hoon; Lee, Suk; Cho, Sam Ju; Choi, Jinho

    2012-10-01

    In this study, a computer-based system for routine quality assurance (QA) of a linear accelerator (linac) was developed by using the dosimetric properties of an amorphous silicon electronic portal imaging device (EPID). An acrylic template phantom was designed such that it could be placed on the EPID and be aligned with the light field of the collimator. After irradiation, portal images obtained from the EPID were transferred in DICOM format to a computer and analyzed using a program we developed. The symmetry, flatness, field size, and congruence of the light and radiation fields of the photon beams from the linac were verified simultaneously. To validate the QA system, the ion chamber and film (X-Omat V2; Kodak, New York, NY) measurements were compared with the EPID measurements obtained in this study. The EPID measurements agreed with the film measurements. Parameters for beams with energies of 6 MV and 15 MV were obtained daily for 1 month using this system. It was found that our QA tool using EPID could substitute for the film test, which is a time-consuming method for routine QA assessment.

  11. Design of Dual-Road Transportable Portal Monitoring System for Visible Light and Gamma-Ray Imaging

    SciTech Connect

    Karnowski, Thomas Paul; Cunningham, Mark F; Goddard Jr, James Samuel; Cheriyadat, Anil M; Hornback, Donald Eric; Fabris, Lorenzo; Kerekes, Ryan A; Ziock, Klaus-Peter; Bradley, Eric Craig; Chesser, Joel B; Marchant, William

    2010-01-01

    The use of radiation sensors as portal monitors is increasing due to heightened concerns over the smuggling of fissile material. Transportable systems that can detect significant quantities of fissile material that might be present in vehicular traffic are of particular interest, especially if they can be rapidly deployed to different locations. To serve this application, we have constructed a rapid-deployment portal monitor that uses visible-light and gamma-ray imaging to allow simultaneous monitoring of multiple lanes of traffic from the side of a roadway. The system operation uses machine vision methods on the visible-light images to detect vehicles as they enter and exit the field of view and to measure their position in each frame. The visible-light and gamma-ray cameras are synchronized which allows the gamma-ray imager to harvest gamma-ray data specific to each vehicle, integrating its radiation signature for the entire time that it is in the field of view. Thus our system creates vehicle-specific radiation signatures and avoids source confusion problems that plague non-imaging approaches to the same problem. Our current prototype instrument was designed for measurement of upto five lanes of freeway traffic with a pair of instruments, one on either side of the roadway. Stereoscopic cameras are used with a third alignment camera for motion compensation and are mounted on a 50 deployable mast. In this paper we discuss the design considerations for the machine-vision system, the algorithms used for vehicle detection and position estimates, and the overall architecture of the system. We also discuss system calibration for rapid deployment. We conclude with notes on preliminary performance and deployment.

  12. Biodistribution and Radiation Dosimetry for a Probe Targeting Prostate-Specific Membrane Antigen for Imaging and Therapy

    PubMed Central

    Herrmann, Ken; Bluemel, Christina; Weineisen, Martina; Schottelius, Margret; Wester, Hans-Jürgen; Czernin, Johannes; Eberlein, Uta; Beykan, Seval; Lapa, Constantin; Riedmiller, Hubertus; Krebs, Markus; Kropf, Saskia; Schirbel, Andreas; Buck, Andreas K.; Lassmann, Michael

    2016-01-01

    Prostate-specific membrane antigen (PSMA) is a promising target for diagnosis and treatment of prostate cancer. EuK-Subkff-68Ga-DOTAGA (68Ga-PSMA Imaging & Therapy [PSMA I&T]) is a recently introduced PET tracer for imaging PSMA expression in vivo. Whole-body distribution and radiation dosimetry of this new probe were evaluated. Methods Five patients with a history of prostate cancer were injected intravenously with 91–148 MBq of 68Ga-PSMA I&T (mean ± SD, 128 ± 23 MBq). After an initial series of rapid whole-body scans, 3 static whole-body scans were acquired at 1, 2, and 4 h after tracer injection. Time-dependent changes of the injected activity per organ were determined. Mean organ-absorbed doses and effective doses were calculated using OLINDA/EXM. Results Injection of 150 MBq of 68Ga-PSMA I&T resulted in an effective dose of 3.0 mSv. The kidneys were the critical organ (33 mGy), followed by the urinary bladder wall and spleen (10 mGy each), salivary glands (9 mGy each), and liver (7 mGy). Conclusion 68Ga-PSMA I&T exhibits a favorable dosimetry, delivering organ doses that are comparable to (kidneys) or lower than those delivered by 18F-FDG. PMID:25883128

  13. The importance of 3D dosimetry

    NASA Astrophysics Data System (ADS)

    Low, Daniel

    2015-01-01

    Radiation therapy has been getting progressively more complex for the past 20 years. Early radiation therapy techniques needed only basic dosimetry equipment; motorized water phantoms, ionization chambers, and basic radiographic film techniques. As intensity modulated radiation therapy and image guided therapy came into widespread practice, medical physicists were challenged with developing effective and efficient dose measurement techniques. The complex 3-dimensional (3D) nature of the dose distributions that were being delivered demanded the development of more quantitative and more thorough methods for dose measurement. The quality assurance vendors developed a wide array of multidetector arrays that have been enormously useful for measuring and characterizing dose distributions, and these have been made especially useful with the advent of 3D dose calculation systems based on the array measurements, as well as measurements made using film and portal imagers. Other vendors have been providing 3D calculations based on data from the linear accelerator or the record and verify system, providing thorough evaluation of the dose but lacking quality assurance (QA) of the dose delivery process, including machine calibration. The current state of 3D dosimetry is one of a state of flux. The vendors and professional associations are trying to determine the optimal balance between thorough QA, labor efficiency, and quantitation. This balance will take some time to reach, but a necessary component will be the 3D measurement and independent calculation of delivered radiation therapy dose distributions.

  14. Application of the optically stimulated luminescence (OSL) technique for mouse dosimetry in micro-CT imaging

    SciTech Connect

    Vrigneaud, Jean-Marc; Courteau, Alan; Oudot, Alexandra; Collin, Bertrand; Ranouil, Julien; Morgand, Loïc; Raguin, Olivier; Walker, Paul; Brunotte, François

    2013-12-15

    Purpose: Micro-CT is considered to be a powerful tool to investigate various models of disease on anesthetized animals. In longitudinal studies, the radiation dose delivered by the micro-CT to the same animal is a major concern as it could potentially induce spurious effects in experimental results. Optically stimulated luminescence dosimeters (OSLDs) are a relatively new kind of detector used in radiation dosimetry for medical applications. The aim of this work was to assess the dose delivered by the CT component of a micro-SPECT (single-photon emission computed tomography)/CT camera during a typical whole-body mouse study, using commercially available OSLDs based on Al{sub 2}O{sub 3}:C crystals.Methods: CTDI (computed tomography dose index) was measured in micro-CT with a properly calibrated pencil ionization chamber using a rat-like phantom (60 mm in diameter) and a mouse-like phantom (30 mm in diameter). OSLDs were checked for reproducibility and linearity in the range of doses delivered by the micro-CT. Dose measurements obtained with OSLDs were compared to those of the ionization chamber to correct for the radiation quality dependence of OSLDs in the low-kV range. Doses to tissue were then investigated in phantoms and cadavers. A 30 mm diameter phantom, specifically designed to insert OSLDs, was used to assess radiation dose over a typical whole-body mouse imaging study. Eighteen healthy female BALB/c mice weighing 27.1 ± 0.8 g (1 SD) were euthanized for small animal measurements. OLSDs were placed externally or implanted internally in nine different locations by an experienced animal technician. Five commonly used micro-CT protocols were investigated.Results: CTDI measurements were between 78.0 ± 2.1 and 110.7 ± 3.0 mGy for the rat-like phantom and between 169.3 ± 4.6 and 203.6 ± 5.5 mGy for the mouse-like phantom. On average, the displayed CTDI at the operator console was underestimated by 1.19 for the rat-like phantom and 2.36 for the mouse

  15. 3D dosimetry estimation for selective internal radiation therapy (SIRT) using SPECT/CT images: a phantom study

    NASA Astrophysics Data System (ADS)

    Debebe, Senait A.; Franquiz, Juan; McGoron, Anthony J.

    2015-03-01

    Selective Internal Radiation Therapy (SIRT) is a common way to treat liver cancer that cannot be treated surgically. SIRT involves administration of Yttrium - 90 (90Y) microspheres via the hepatic artery after a diagnostic procedure using 99mTechnetium (Tc)-macroaggregated albumin (MAA) to detect extrahepatic shunting to the lung or the gastrointestinal tract. Accurate quantification of radionuclide administered to patients and radiation dose absorbed by different organs is of importance in SIRT. Accurate dosimetry for SIRT allows optimization of dose delivery to the target tumor and may allow for the ability to assess the efficacy of the treatment. In this study, we proposed a method that can efficiently estimate radiation absorbed dose from 90Y bremsstrahlung SPECT/CT images of liver and the surrounding organs. Bremsstrahlung radiation from 90Y was simulated using the Compton window of 99mTc (78keV at 57%). 99mTc images acquired at the photopeak energy window were used as a standard to examine the accuracy of dosimetry prediction by the simulated bremsstrahlung images. A Liqui-Phil abdominal phantom with liver, stomach and two tumor inserts was imaged using a Philips SPECT/CT scanner. The Dose Point Kernel convolution method was used to find the radiation absorbed dose at a voxel level for a three dimensional dose distribution. This method will allow for a complete estimate of the distribution of radiation absorbed dose by tumors, liver, stomach and other surrounding organs at the voxel level. The method provides a quantitative predictive method for SIRT treatment outcome and administered dose response for patients who undergo the treatment.

  16. Evaluation of the precision of portal-image-guided head-and-neck localization: An intra- and interobserver study

    SciTech Connect

    Court, Laurence E.; Allen, Aaron; Tishler, Roy

    2007-07-15

    There is increasing evidence that, for some patients, image-guided intensity-modulated radiation therapy (IMRT) for head-and-neck cancer patients may maintain target dose coverage and critical organ (e.g., parotids) dose closer to the planned doses than setup using lasers alone. We investigated inter- and intraobserver uncertainties in patient setup in head-and-neck cancer patients. Twenty-two sets of orthogonal digital portal images (from five patients) were selected from images used for daily localization of head-and-neck patients treated with IMRT. To evaluate interobserver variations, five radiation therapists compared the portal images with the plan digitally reconstructed radiographs and reported shifts for the isocenter ({approx}C2) and for a supraclavicular reference point. One therapist repeated the procedure a month later to evaluate intraobserver variations. The procedure was then repeated with teams of two therapists. The frequencies for which agreement between the shift reported by the observer and the daily mean shift (average of all observers for a given image set) were less than 1.5 and 2.5 mm were calculated. Standard errors of measurement for the intra- and interobserver uncertainty (SEM{sub intra} and SEM{sub inter}) for the individual and teams were calculated. The data showed that there was very little difference between individual therapists and teams. At isocenter, 80%-90% of all reported shifts agreed with the daily average within 1.5 mm, showing consistency in the ways both individuals and teams interpret the images (SEM{sub inter}{approx}1 mm). This dropped to 65% for the supraclavicular point (SEM{sub inter}{approx}1.5 mm). Uncertainties increased for larger setup errors. In conclusion, image-guided patient positioning allows head-and-neck patients to be controlled within 3-4 mm. This is similar to the setup uncertainties found for most head-and-neck patients, but may provide some improvement for the subset of patients with larger setup

  17. Testing the GLAaS algorithm for dose measurements on low- and high-energy photon beams using an amorphous silicon portal imager

    SciTech Connect

    Nicolini, Giorgia; Fogliata, Antonella; Vanetti, Eugenio; Clivio, Alessandro; Vetterli, Daniel; Cozzi, Luca

    2008-02-15

    The GLAaS algorithm for pretreatment intensity modulation radiation therapy absolute dose verification based on the use of amorphous silicon detectors, as described in Nicolini et al. [G. Nicolini, A. Fogliata, E. Vanetti, A. Clivio, and L. Cozzi, Med. Phys. 33, 2839-2851 (2006)], was tested under a variety of experimental conditions to investigate its robustness, the possibility of using it in different clinics and its performance. GLAaS was therefore tested on a low-energy Varian Clinac (6 MV) equipped with an amorphous silicon Portal Vision PV-aS500 with electronic readout IAS2 and on a high-energy Clinac (6 and 15 MV) equipped with a PV-aS1000 and IAS3 electronics. Tests were performed for three calibration conditions: A: adding buildup on the top of the cassette such that SDD-SSD=d{sub max} and comparing measurements with corresponding doses computed at d{sub max}, B: without adding any buildup on the top of the cassette and considering only the intrinsic water-equivalent thickness of the electronic portal imaging devices device (0.8 cm), and C: without adding any buildup on the top of the cassette but comparing measurements against doses computed at d{sub max}. This procedure is similar to that usually applied when in vivo dosimetry is performed with solid state diodes without sufficient buildup material. Quantitatively, the gamma index ({gamma}), as described by Low et al. [D. A. Low, W. B. Harms, S. Mutic, and J. A. Purdy, Med. Phys. 25, 656-660 (1998)], was assessed. The {gamma} index was computed for a distance to agreement (DTA) of 3 mm. The dose difference {delta}D was considered as 2%, 3%, and 4%. As a measure of the quality of results, the fraction of field area with gamma larger than 1 (%FA) was scored. Results over a set of 50 test samples (including fields from head and neck, breast, prostate, anal canal, and brain cases) and from the long-term routine usage, demonstrated the robustness and stability of GLAaS. In general, the mean values of %FA

  18. Transjugular Portal Venous Stenting in Inflammatory Extrahepatic Portal Vein Stenosis

    SciTech Connect

    Schaible, Rolf; Textor, Jochen; Decker, Pan; Strunk, Holger; Schild, Hans

    2002-12-15

    We report the case of a 37-year-old man with necrotizing pancreatitis associated with inflammatory extrahepatic portal vein stenosis and progressive ascites. Four months after the acute onset, when no signs of infection were present, portal decompression was performed to treat refractory ascites. Transjugulartranshepatic venoplasty failed to dilate the stenosis in the extrahepatic portion of the portal vein sufficiently. Therefore a Wallstent was implanted, resulting in almost normal diameter of the vessel. In follow-up imaging studies the stent and the portal vein were still patent 12 months after the intervention and total resolution of the ascites was observed.

  19. A reference skeletal dosimetry model for an adult male radionuclide therapy patient based on three-dimensional imaging and paired-image radiation transport

    NASA Astrophysics Data System (ADS)

    Shah, Amish P.

    The need for improved patient-specificity of skeletal dose estimates is widely recognized in radionuclide therapy. Current clinical models for marrow dose are based on skeletal mass estimates from a variety of sources and linear chord-length distributions that do not account for particle escape into cortical bone. To predict marrow dose, these clinical models use a scheme that requires separate calculations of cumulated activity and radionuclide S values. Selection of an appropriate S value is generally limited to one of only three sources, all of which use as input the trabecular microstructure of an individual measured 25 years ago, and the tissue mass derived from different individuals measured 75 years ago. Our study proposed a new modeling approach to marrow dosimetry---the Paired Image Radiation Transport (PIRT) model---that properly accounts for both the trabecular microstructure and the cortical macrostructure of each skeletal site in a reference male radionuclide patient. The PIRT model, as applied within EGSnrc, requires two sets of input geometry: (1) an infinite voxel array of segmented microimages of the spongiosa acquired via microCT; and (2) a segmented ex-vivo CT image of the bone site macrostructure defining both the spongiosa (marrow, endosteum, and trabeculae) and the cortical bone cortex. Our study also proposed revising reference skeletal dosimetry models for the adult male cancer patient. Skeletal site-specific radionuclide S values were obtained for a 66-year-old male reference patient. The derivation for total skeletal S values were unique in that the necessary skeletal mass and electron dosimetry calculations were formulated from the same source bone site over the entire skeleton. We conclude that paired-image radiation-transport techniques provide an adoptable method by which the intricate, anisotropic trabecular microstructure of the skeletal site; and the physical size and shape of the bone can be handled together, for improved

  20. Bone marrow dosimetry via microCT imaging and stem cell spatial mapping

    NASA Astrophysics Data System (ADS)

    Kielar, Kayla N.

    In order to make predictions of radiation dose in patients undergoing targeted radionuclide therapy of cancer, an accurate model of skeletal tissues is necessary. Concerning these tissues, the dose-limiting factor in these therapies is the toxicity of the hematopoietically active bone marrow. In addition to acute effects, one must be concerned as well with long-term stochastic effects such as radiation-induced leukemia. Particular cells of interest for both toxicity and cancer risk are the hematopoietic stem cells (HSC), found within the active marrow regions of the skeleton. At present, cellular-level dosimetry models are complex, and thus we cannot model individual stem cells in an anatomic model of the patient. As a result, one reverts to looking at larger tissue regions where these cell populations may reside. To provide a more accurate marrow dose assessment, the skeletal dosimetry model must also be patient-specific. That is, it should be designed to match as closely as possible to the patient undergoing treatment. Absorbed dose estimates then can be tailored based on the skeletal size and trabecular microstructure of an individual for an accurate prediction of marrow toxicity. Thus, not only is it important to accurately model the target tissues of interest in a normal patient, it is important to do so for differing levels of marrow health. A skeletal dosimetry model for the adult female was provided for better predictions of marrow toxicity in patients undergoing radionuclide therapy. This work is the first fully established gender specific model for these applications, and supersedes previous models in scalability of the skeleton and radiation transport methods. Furthermore, the applicability of using bone marrow biopsies was deemed sufficient in prediction of bone marrow health, specifically for the hematopoietic stem cell population. The location and concentration of the HSC in bone marrow was found to follow a spatial gradient from the bone trabeculae

  1. Patient-specific dosimetry based on quantitative SPECT imaging and 3D-DFT convolution

    SciTech Connect

    Akabani, G.; Hawkins, W.G.; Eckblade, M.B.; Leichner, P.K.

    1999-01-01

    The objective of this study was to validate the use of a 3-D discrete Fourier Transform (3D-DFT) convolution method to carry out the dosimetry for I-131 for soft tissues in radioimmunotherapy procedures. To validate this convolution method, mathematical and physical phantoms were used as a basis of comparison with Monte Carlo transport (MCT) calculations which were carried out using the EGS4 system code. The mathematical phantom consisted of a sphere containing uniform and nonuniform activity distributions. The physical phantom consisted of a cylinder containing uniform and nonuniform activity distributions. Quantitative SPECT reconstruction was carried out using the Circular Harmonic Transform (CHT) algorithm.

  2. Investigation of the mechanical performance of Siemens linacs components during arc: gantry, MLC, and electronic portal imaging device

    PubMed Central

    Rowshanfarzad, Pejman; Häring, Peter; Riis, Hans L; Zimmermann, Sune J; Ebert, Martin A

    2015-01-01

    Background In radiotherapy treatments, it is crucial to monitor the performance of linac components including gantry, collimation system, and electronic portal imaging device (EPID) during arc deliveries. In this study, a simple EPID-based measurement method is suggested in conjunction with an algorithm to investigate the stability of these systems at various gantry angles with the aim of evaluating machine-related errors in treatments. Methods The EPID sag, gantry sag, changes in source-to-detector distance (SDD), EPID and collimator skewness, EPID tilt, and the sag in leaf bank assembly due to linac rotation were separately investigated by acquisition of 37 EPID images of a simple phantom with five ball bearings at various gantry angles. A fast and robust software package was developed for automated analysis of image data. Three Siemens linacs were investigated. Results The average EPID sag was within 1 mm for all tested linacs. Two machines showed >1 mm gantry sag. Changes in the SDD values were within 7.5 mm. EPID skewness and tilt values were <1° in all machines. The maximum sag in leaf bank assembly was <1 mm. Conclusion The method and software developed in this study provide a simple tool for effective investigation of the behavior of Siemens linac components with gantry rotation. Such a comprehensive study has been performed for the first time on Siemens machines. PMID:26604840

  3. SU-C-201-06: Utility of Quantitative 3D SPECT/CT Imaging in Patient Specific Internal Dosimetry of 153-Samarium with GATE Monte Carlo Package

    SciTech Connect

    Fallahpoor, M; Abbasi, M; Sen, A; Parach, A; Kalantari, F

    2015-06-15

    Purpose: Patient-specific 3-dimensional (3D) internal dosimetry in targeted radionuclide therapy is essential for efficient treatment. Two major steps to achieve reliable results are: 1) generating quantitative 3D images of radionuclide distribution and attenuation coefficients and 2) using a reliable method for dose calculation based on activity and attenuation map. In this research, internal dosimetry for 153-Samarium (153-Sm) was done by SPECT-CT images coupled GATE Monte Carlo package for internal dosimetry. Methods: A 50 years old woman with bone metastases from breast cancer was prescribed 153-Sm treatment (Gamma: 103keV and beta: 0.81MeV). A SPECT/CT scan was performed with the Siemens Simbia-T scanner. SPECT and CT images were registered using default registration software. SPECT quantification was achieved by compensating for all image degrading factors including body attenuation, Compton scattering and collimator-detector response (CDR). Triple energy window method was used to estimate and eliminate the scattered photons. Iterative ordered-subsets expectation maximization (OSEM) with correction for attenuation and distance-dependent CDR was used for image reconstruction. Bilinear energy mapping is used to convert Hounsfield units in CT image to attenuation map. Organ borders were defined by the itk-SNAP toolkit segmentation on CT image. GATE was then used for internal dose calculation. The Specific Absorbed Fractions (SAFs) and S-values were reported as MIRD schema. Results: The results showed that the largest SAFs and S-values are in osseous organs as expected. S-value for lung is the highest after spine that can be important in 153-Sm therapy. Conclusion: We presented the utility of SPECT-CT images and Monte Carlo for patient-specific dosimetry as a reliable and accurate method. It has several advantages over template-based methods or simplified dose estimation methods. With advent of high speed computers, Monte Carlo can be used for treatment planning

  4. SU-E-T-497: Semi-Automated in Vivo Radiochromic Film Dosimetry Using a Novel Image Processing Algorithm

    SciTech Connect

    Reyhan, M; Yue, N

    2014-06-01

    Purpose: To validate an automated image processing algorithm designed to detect the center of radiochromic film used for in vivo film dosimetry against the current gold standard of manual selection. Methods: An image processing algorithm was developed to automatically select the region of interest (ROI) in *.tiff images that contain multiple pieces of radiochromic film (0.5x1.3cm{sup 2}). After a user has linked a calibration file to the processing algorithm and selected a *.tiff file for processing, an ROI is automatically detected for all films by a combination of thresholding and erosion, which removes edges and any additional markings for orientation. Calibration is applied to the mean pixel values from the ROIs and a *.tiff image is output displaying the original image with an overlay of the ROIs and the measured doses. Validation of the algorithm was determined by comparing in vivo dose determined using the current gold standard (manually drawn ROIs) versus automated ROIs for n=420 scanned films. Bland-Altman analysis, paired t-test, and linear regression were performed to demonstrate agreement between the processes. Results: The measured doses ranged from 0.2-886.6cGy. Bland-Altman analysis of the two techniques (automatic minus manual) revealed a bias of -0.28cGy and a 95% confidence interval of (5.5cGy,-6.1cGy). These values demonstrate excellent agreement between the two techniques. Paired t-test results showed no statistical differences between the two techniques, p=0.98. Linear regression with a forced zero intercept demonstrated that Automatic=0.997*Manual, with a Pearson correlation coefficient of 0.999. The minimal differences between the two techniques may be explained by the fact that the hand drawn ROIs were not identical to the automatically selected ones. The average processing time was 6.7seconds in Matlab on an IntelCore2Duo processor. Conclusion: An automated image processing algorithm has been developed and validated, which will help

  5. Superficial dosimetry imaging based on Čerenkov emission for external beam radiotherapy with megavoltage x-ray beam

    SciTech Connect

    Zhang, Rongxiao; Glaser, Adam K.; Gladstone, David J.; Fox, Colleen J.; Pogue, Brian W.

    2013-10-15

    Purpose: Čerenkov radiation emission occurs in all tissue, when charged particles (either primary or secondary) travel at velocity above the threshold for the Čerenkov effect (about 220 KeV in tissue for electrons). This study presents the first examination of optical Čerenkov emission as a surrogate for the absorbed superficial dose for MV x-ray beams.Methods: In this study, Monte Carlo simulations of flat and curved surfaces were studied to analyze the energy spectra of charged particles produced in different regions near the surfaces when irradiated by MV x-ray beams. Čerenkov emission intensity and radiation dose were directly simulated in voxelized flat and cylindrical phantoms. The sampling region of superficial dosimetry based on Čerenkov radiation was simulated in layered skin models. Angular distributions of optical emission from the surfaces were investigated. Tissue mimicking phantoms with flat and curved surfaces were imaged with a time domain gating system. The beam field sizes (50 × 50–200 × 200 mm{sup 2}), incident angles (0°–70°) and imaging regions were all varied.Results: The entrance or exit region of the tissue has nearly homogeneous energy spectra across the beam, such that their Čerenkov emission is proportional to dose. Directly simulated local intensity of Čerenkov and radiation dose in voxelized flat and cylindrical phantoms further validate that this signal is proportional to radiation dose with absolute average discrepancy within 2%, and the largest within 5% typically at the beam edges. The effective sampling depth could be tuned from near 0 up to 6 mm by spectral filtering. The angular profiles near the theoretical Lambertian emission distribution for a perfect diffusive medium, suggesting that angular correction of Čerenkov images may not be required even for curved surface. The acquisition speed and signal to noise ratio of the time domain gating system were investigated for different acquisition procedures, and the

  6. Using combined x-ray and MR imaging for prostate I-125 post-implant dosimetry: phantom validation and preliminary patient work

    NASA Astrophysics Data System (ADS)

    Miquel, M. E.; Rhode, K. S.; Acher, P. L.; MacDougall, N. D.; Blackall, J.; Gaston, R. P.; Hegde, S.; Morris, S. L.; Beaney, R.; Deehan, C.; Popert, R.; Keevil, S. F.

    2006-03-01

    Post-implantation dosimetry is an important element of permanent prostate brachytherapy. This process relies on accurate localization of implanted seeds relative to the surrounding organs. Localization is commonly achieved using CT images, which provide suboptimal prostate delineation. On MR images, conversely, prostate visualization is excellent but seed localization is imprecise due to distortion and susceptibility artefacts. This paper presents a method based on fused MR and x-ray images acquired consecutively in a combined x-ray and MRI interventional suite. The method does not rely on any explicit registration step but on a combination of system calibration and tracking. A purpose-built phantom was imaged using MRI and x-rays, and the images were successfully registered. The same protocol was applied to three patients where combining soft tissue information from MRI with stereoscopic seed identification from x-ray imaging facilitated post-implant dosimetry. This technique has the potential to improve on dosimetry using either CT or MR alone.

  7. Generalized EPID calibration for in vivo transit dosimetry.

    PubMed

    Fidanzio, Andrea; Cilla, Savino; Greco, Francesca; Gargiulo, Laura; Azario, Luigi; Sabatino, Domenico; Piermattei, Angelo

    2011-01-01

    Many researchers are studying new in vivo dosimetry methods based on the use of Elelctronic portal imaging devices (EPIDs) that are simple and efficient in their daily use. However the need of time consuming implementation measurements with solid water phantoms for the in vivo dosimetry implementation can discourage someone in their use. In this paper a procedure has been proposed to calibrate aSi EPIDs for in vivo transit dosimetry. The dosimetric equivalence of three aSi Varian EPIDs has been investigated in terms of signal reproducibility and long term stability, signal linearity with MU and dose per pulse and signal dependence on the field dimensions. The signal reproducibility was within ± 0.5% (2SD), while the long term signal stability has been maintained well within ± 2%. The signal linearity with the monitor units (MU) was within ± 2% and within ± 0.5% for the EPIDs controlled by the IAS 2, and IAS 3 respectively. In particular it was verified that the correction factor for the signal linearity with the monitor units, k(lin), is independent of the beam quality, and the dose per pulse absorbed by the EPID. For 6, 10 and 15 MV photon beams, a generalized set of correlation functions F(TPR,w,L) and empirical factors f(TPR,d,L) as a function of the Tissue Phantom Ratio (TPR), the phantom thickness, w, the square field side, L, and the distance, d, between the phantom mid-plane and the isocentre were determined to reconstruct the isocenter dose. The tolerance levels of the present in vivo dosimetry method ranged between ± 5% and ± 6% depending on the tumor body location. In conclusion, the procedure proposed, that use generalized correlation functions, reduces the effort for the in vivo dosimetry method implementation for those photon beams with TPR within ± 0.3% as respect those here used.

  8. SU-C-204-05: Simulations of a Portal Imaging System for Conformal and Intensity Modulated Fast Neutron Therapy

    SciTech Connect

    James, S St.; Argento, D; Stewart, R

    2015-06-15

    Purpose: The University of Washington Medical Center offers neutron therapy for the palliative and definitive treatment of selected cancers. In vivo field verification has the potential to improve the safe and effective delivery of neutron therapy. We propose a portal imaging method that relies on the creation of positron emitting isotopes (11C and 15O) through (n, 2n) reactions with a PMMA plate placed below the patient. After field delivery, the plate is retrieved from the vault and imaged using a reader that detects annihilation photons. The spatial pattern of activity produced in the PMMA plate provides information to reconstruct the neutron fluence map needed to confirm treatment delivery. Methods: We used MCNP to simulate the accumulation of 11C activity in a slab of PMMA 2 mm thick, and GATE was used to simulate the sensitivity and spatial resolution of a prototype imaging system. BGO crystal thicknesses of 1 cm, 2 cm and 3 cm were simulated with detector separations of 2 cm. Crystal pitches of 2 mm and 4 mm were evaluated. Back-projection of the events was used to create a planar image. The spatial resolution was taken to be the FWHM of the reconstructed point source image. Results: The system sensitivity for a point source in the center of the field of view was found to range from 58% for 1 cm thick BGO with 2 mm crystal pitch to 74% for the 3 cm thick BGO crystals with 4 mm crystal pitch. The spatial resolution at the center of the field of view was found to be 1.5 mm for the system with 2 mm crystal pitch and 2.8 mm for the system with the 4 mm crystal pitch. Conclusion: BGO crystals with 4 mm crystal pitch and 3 cm length would offer the best sensitivity reader.

  9. Computational dosimetry

    SciTech Connect

    Siebert, B.R.L.; Thomas, R.H.

    1996-01-01

    The paper presents a definition of the term ``Computational Dosimetry`` that is interpreted as the sub-discipline of computational physics which is devoted to radiation metrology. It is shown that computational dosimetry is more than a mere collection of computational methods. Computational simulations directed at basic understanding and modelling are important tools provided by computational dosimetry, while another very important application is the support that it can give to the design, optimization and analysis of experiments. However, the primary task of computational dosimetry is to reduce the variance in the determination of absorbed dose (and its related quantities), for example in the disciplines of radiological protection and radiation therapy. In this paper emphasis is given to the discussion of potential pitfalls in the applications of computational dosimetry and recommendations are given for their avoidance. The need for comparison of calculated and experimental data whenever possible is strongly stressed.

  10. Breast Patient Setup Error Assessment: Comparison of Electronic Portal Image Devices and Cone-Beam Computed Tomography Matching Results

    SciTech Connect

    Topolnjak, Rajko; Sonke, Jan-Jakob; Nijkamp, Jasper; Rasch, Coen; Minkema, Danny; Remeijer, Peter; Vliet-Vroegindeweij, Corine van

    2010-11-15

    Purpose: To quantify the differences in setup errors measured with the cone-beam computed tomography (CBCT) and electronic portal image devices (EPID) in breast cancer patients. Methods and Materials: Repeat CBCT scan were acquired for routine offline setup verification in 20 breast cancer patients. During the CBCT imaging fractions, EPID images of the treatment beams were recorded. Registrations of the bony anatomy for CBCT to planning CT and EPID to digitally reconstructed-radiographs (DRRs) were compared. In addition, similar measurements of an anthropomorphic thorax phantom were acquired. Bland-Altman and linear regression analysis were performed for clinical and phantom registrations. Systematic and random setup errors were quantified for CBCT and EPID-driven correction protocols in the EPID coordinate system (U, V), with V parallel to the cranial-caudal axis and U perpendicular to V and the central beam axis. Results: Bland-Altman analysis of clinical EPID and CBCT registrations yielded 4 to 6-mm limits of agreement, indicating that both methods were not compatible. The EPID-based setup errors were smaller than the CBCT-based setup errors. Phantom measurements showed that CBCT accurately measures setup error whereas EPID underestimates setup errors in the cranial-caudal direction. In the clinical measurements, the residual bony anatomy setup errors after offline CBCT-based corrections were {Sigma}{sub U} = 1.4 mm, {Sigma}{sub V} = 1.7 mm, and {sigma}{sub U} = 2.6 mm, {sigma}{sub V} = 3.1 mm. Residual setup errors of EPID driven corrections corrected for underestimation were estimated at {Sigma}{sub U} = 2.2mm, {Sigma}{sub V} = 3.3 mm, and {sigma}{sub U} = 2.9 mm, {sigma}{sub V} = 2.9 mm. Conclusion: EPID registration underestimated the actual bony anatomy setup error in breast cancer patients by 20% to 50%. Using CBCT decreased setup uncertainties significantly.

  11. Monte Carlo simulation of a novel water-equivalent electronic portal imaging device using plastic scintillating fibers

    SciTech Connect

    Teymurazyan, A.; Pang, G.

    2012-03-15

    Purpose: Most electronic portal imaging devices (EPIDs) developed so far use a thin Cu plate/phosphor screen to convert x-ray energies into light photons, while maintaining a high spatial resolution. This results in a low x-ray absorption and thus a low quantum efficiency (QE) of approximately 2-4% for megavoltage (MV) x-rays. A significant increase of QE is desirable for applications such as MV cone-beam computed tomography (MV-CBCT). Furthermore, the Cu plate/phosphor screen contains high atomic number (high-Z) materials, resulting in an undesirable over-response to low energy x-rays (due to photoelectric effect) as well as high energy x-rays (due to pair production) when used for dosimetric verification. Our goal is to develop a new MV x-ray detector that has a high QE and uses low-Z materials to overcome the obstacles faced by current MV x-ray imaging technologies. Methods: A new high QE and low-Z EPID is proposed. It consists of a matrix of plastic scintillating fibers embedded in a water-equivalent medium and coupled to an optically sensitive 2D active matrix flat panel imager (AMFPI) for image readout. It differs from the previous approach that uses segmented crystalline scintillators made of higher density and higher atomic number materials to detect MV x-rays. The plastic scintillating fibers are focused toward the x-ray source to avoid image blurring due to oblique incidence of off-axis x-rays. When MV x-rays interact with the scintillating fibers in the detector, scintillation light will be produced. The light photons produced in a fiber core and emitted within the acceptance angle of the fiber will be guided toward the AMFPI by total internal reflection. A Monte Carlo simulation has been used to investigate imaging and dosimetric characteristics of the proposed detector under irradiation of MV x-rays. Results: Properties, such as detection efficiency, modulation transfer function, detective quantum efficiency (DQE), energy dependence of detector

  12. Study of X-ray field junction dose using an a-Si electronic portal imaging device.

    PubMed

    Madebo, Mebratu; Perkins, A; Fox, C; Johnston, P; Kron, T

    2010-03-01

    Field junctions between megavoltage photon beams are important in modern radiotherapy for treatments such as head and neck and breast cancer. An electronic portal imaging device (EPID) may be used to study junction dose between two megavoltage X-ray fields. In this study, the junction dose was used to determine machine characteristics such as jaw positions and their reproducibility, collimator rotation and the effect of gantry rotation. All measurements were done on Varian linear accelerators with EPID (Varian, Palo Alto, CA). The results show reproducibility in jaw positions of approximately 0.3 mm for repeated jaw placement while EPID readings were reproducible within a standard deviation of 0.4% for fixed jaw positions. Junction dose also allowed collimator rotation error of 0.1 degrees to be observed. Dependence of junction dose on gantry rotation due to gravity was observed; the gravity effect being maximum at 180 degrees gantry angle (beam pointing up). EPIDs were found to be reliable tools for checking field junctions, which in turn may be used to check jaw reproducibility and collimator rotation of linacs. PMID:20237889

  13. Skeletal dosimetry for external exposure to photons based on µCT images of spongiosa from different bone sites

    NASA Astrophysics Data System (ADS)

    Kramer, R.; Khoury, H. J.; Vieira, J. W.; Kawrakow, I.

    2007-11-01

    Micro computed tomography (µCT) images of human spongiosa have recently been used for skeletal dosimetry with respect to external exposure to photon radiation. In this previous investigation, the calculation of equivalent dose to the red bone marrow (RBM) and to the bone surface cells (BSC) was based on five different clusters of micro matrices derived from µCT images of vertebrae, and the BSC equivalent dose for 10 µm thickness of the BSC layer was determined using an extrapolation method. The purpose of this study is to extend the earlier investigation by using µCT images from eight different bone sites and by introducing an algorithm for the direct calculation of the BSC equivalent dose with sub-micro voxel resolution. The results show that for given trabecular bone volume fractions (TBVFs) the whole-body RBM equivalent dose does not depend on bone site-specific properties or imaging parameters. However, this study demonstrates that apart from the TBVF and the BSC layer thickness, the BSC equivalent dose additionally depends on a so-called trabecular bone structure (TBS) effect, i.e. that the contribution of photo-electrons released in trabecular bone to the BSC equivalent dose also depends on the bone site-specific structure of the trabeculae. For a given bone site, the TBS effect is also a function of the thickness of the BSC layer, and it could be shown that this effect would disappear almost completely, should the BSC layer thickness be raised from 10 to 50 µm, according to new radiobiological findings.

  14. In aqua vivo EPID dosimetry

    SciTech Connect

    Wendling, Markus; McDermott, Leah N.; Mans, Anton; Olaciregui-Ruiz, Igor; Pecharroman-Gallego, Raul; Sonke, Jan-Jakob; Stroom, Joep; Herk, Marcel J.; Mijnheer, Ben van

    2012-01-15

    Purpose: At the Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital in vivo dosimetry using an electronic portal imaging device (EPID) has been implemented for almost all high-energy photon treatments of cancer with curative intent. Lung cancer treatments were initially excluded, because the original back-projection dose-reconstruction algorithm uses water-based scatter-correction kernels and therefore does not account for tissue inhomogeneities accurately. The aim of this study was to test a new method, in aqua vivo EPID dosimetry, for fast dose verification of lung cancer irradiations during actual patient treatment. Methods: The key feature of our method is the dose reconstruction in the patient from EPID images, obtained during the actual treatment, whereby the images have been converted to a situation as if the patient consisted entirely of water; hence, the method is termed in aqua vivo. This is done by multiplying the measured in vivo EPID image with the ratio of two digitally reconstructed transmission images for the unit-density and inhomogeneous tissue situation. For dose verification, a comparison is made with the calculated dose distribution with the inhomogeneity correction switched off. IMRT treatment verification is performed for each beam in 2D using a 2D {gamma} evaluation, while for the verification of volumetric-modulated arc therapy (VMAT) treatments in 3D a 3D {gamma} evaluation is applied using the same parameters (3%, 3 mm). The method was tested using two inhomogeneous phantoms simulating a tumor in lung and measuring its sensitivity for patient positioning errors. Subsequently five IMRT and five VMAT clinical lung cancer treatments were investigated, using both the conventional back-projection algorithm and the in aqua vivo method. The verification results of the in aqua vivo method were statistically analyzed for 751 lung cancer patients treated with IMRT and 50 lung cancer patients treated with VMAT. Results: The improvements by

  15. The CEOS-Land Surface Imaging Constellation Portal for GEOSS: A resource for land surface imaging system information and data access

    USGS Publications Warehouse

    Holm, Thomas; Gallo, Kevin P.; Bailey, Bryan

    2010-01-01

    The Committee on Earth Observation Satellites is an international group that coordinates civil space-borne observations of the Earth, and provides the space component of the Global Earth Observing System of Systems (GEOSS). The CEOS Virtual Constellations concept was implemented in an effort to engage and coordinate disparate Earth observing programs of CEOS member agencies and ultimately facilitate their contribution in supplying the space-based observations required to satisfy the requirements of the GEOSS. The CEOS initially established Study Teams for four prototype constellations that included precipitation, land surface imaging, ocean surface topography, and atmospheric composition. The basic mission of the Land Surface Imaging (LSI) Constellation [1] is to promote the efficient, effective, and comprehensive collection, distribution, and application of space-acquired image data of the global land surface, especially to meet societal needs of the global population, such as those addressed by the nine Group on Earth Observations (GEO) Societal Benefit Areas (SBAs) of agriculture, biodiversity, climate, disasters, ecosystems, energy, health, water, and weather. The LSI Constellation Portal is the result of an effort to address important goals within the LSI Constellation mission and provide resources to assist in planning for future space missions that might further contribute to meeting those goals.

  16. Topical Review: Polymer gel dosimetry

    PubMed Central

    Baldock, C; De Deene, Y; Doran, S; Ibbott, G; Jirasek, A; Lepage, M; McAuley, K B; Oldham, M; Schreiner, L J

    2010-01-01

    Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented. PMID:20150687

  17. Secure portal.

    SciTech Connect

    Nelson, Cynthia Lee

    2007-09-01

    There is a need in security systems to rapidly and accurately grant access of authorized personnel to a secure facility while denying access to unauthorized personnel. In many cases this role is filled by security personnel, which can be very costly. Systems that can perform this role autonomously without sacrificing accuracy or speed of throughput are very appealing. To address the issue of autonomous facility access through the use of technology, the idea of a ''secure portal'' is introduced. A secure portal is a defined zone where state-of-the-art technology can be implemented to grant secure area access or to allow special privileges for an individual. Biometric technologies are of interest because they are generally more difficult to defeat than technologies such as badge swipe and keypad entry. The biometric technologies selected for this concept were facial and gait recognition. They were chosen since they require less user cooperation than other biometrics such as fingerprint, iris, and hand geometry and because they have the most potential for flexibility in deployment. The secure portal concept could be implemented within the boundaries of an entry area to a facility. As a person is approaching a badge and/or PIN portal, face and gait information can be gathered and processed. The biometric information could be fused for verification against the information that is gathered from the badge. This paper discusses a facial recognition technology that was developed for the purposes of providing high verification probabilities with low false alarm rates, which would be required of an autonomous entry control system. In particular, a 3-D facial recognition approach using Fisher Linear Discriminant Analysis is described. Gait recognition technology, based on Hidden Markov Models has been explored, but those results are not included in this paper. Fusion approaches for combining the results of the biometrics would be the next step in realizing the secure portal

  18. Radioembolization Dosimetry: The Road Ahead

    SciTech Connect

    Smits, Maarten L. J. Elschot, Mattijs; Sze, Daniel Y.; Kao, Yung H.; Nijsen, Johannes F. W.; Iagaru, Andre H.; Jong, Hugo W. A. M. de; Bosch, Maurice A. A. J. van den; Lam, Marnix G. E. H.

    2015-04-15

    Methods for calculating the activity to be administered during yttrium-90 radioembolization (RE) are largely based on empirical toxicity and efficacy analyses, rather than dosimetry. At the same time, it is recognized that treatment planning based on proper dosimetry is of vital importance for the optimization of the results of RE. The heterogeneous and often clustered intrahepatic biodistribution of millions of point-source radioactive particles poses a challenge for dosimetry. Several studies found a relationship between absorbed doses and treatment outcome, with regard to both toxicity and efficacy. This should ultimately lead to improved patient selection and individualized treatment planning. New calculation methods and imaging techniques and a new generation of microspheres for image-guided RE will all contribute to these improvements. The aim of this review is to give insight into the latest and most important developments in RE dosimetry and to suggest future directions on patient selection, individualized treatment planning, and study designs.

  19. The Effect of Registration Surrogate and Patient Factors on the Interobserver Variability of Electronic Portal Image Guidance During Prostate Radiotherapy

    SciTech Connect

    Kong, Vickie Lockwood, Gina; Yan Jing; Catton, Charles; Chung, Peter; Bayley, Andrew; Rosewall, Tara

    2011-01-01

    Intraprostatic fiducial markers (IPM) and electronic portal imaging (EPI) are commonly used to identify and correct for prostate motion during radiotherapy. However, little data is available on the precision of this image-guidance technique. This study quantified impact of different registration surrogates and patient factors on the interobserver variability of manual EPI alignment during prostate radiotherapy. For 50 prostate radiotherapy patients previously implanted with 3 IPM, five observers manually aligned 150 pairs of orthogonal EPI to the reference digital reconstructed radiograph using Varian Vision EPI analysis software. Images were aligned using: Bony anatomy (BA), single mid-prostate IPM (SM); and 2 strategies using 3 IPM: center of mass (COM) and rotate and translate (R and T). Intraclass correlation coefficients (ICCs) were calculated to quantify interobserver variability. The absolute displacements measured using SM and R and T were compared with those using COM. The impact of patients' pelvic diameter and adjuvant hormone therapy on interobserver variability were also evaluated. Twelve thousand displacement values were collected for analysis. The maximum discrepancy between the 5 observers was >2 mm in 47% of measurements using BA, 5% using SM, 4% using R and T, and 3% using COM. Both of the 3 IPM alignment strategies demonstrated lower interobserver variability than the single IPM strategy (ICC 0.94-0.97 vs. 0.82-0.94). BA had the highest interobserver variability (ICC = 0.43-0.90). Pelvic diameter and hormone therapy had no discernible impact on interobserver variability. Compared with COM, the absolute displacements measured using the other IPM strategies were statistically different (p < 0.001), but 95% of the absolute magnitude of differences between the strategies were {<=}1 mm. The high reproducibility among the observers demonstrated the precision of prostate localization using multiple IPM and EPI, which was not influenced by the patient

  20. SU-E-T-438: Commissioning of An In-Vivo Quality Assurance Method Using the Electronic Portal Imaging Device

    SciTech Connect

    Morin, O; Held, M; Pouliot, J

    2014-06-01

    Purpose: Patient specific pre-treatment quality assurance (QA) using arrays of detectors or film have been the standard approach to assure the correct treatment is delivered to the patient. This QA approach is expensive, labor intensive and does not guarantee or document that all remaining fractions were treated properly. The purpose of this abstract is to commission and evaluate the performance of a commercially available in-vivo QA software using the electronic portal imaging device (EPID) to record the daily treatments. Methods: The platform EPIgray V2.0.2 (Dosisoft), which machine model compares ratios of TMR with EPID signal to predict dose was commissioned for an Artiste (Siemens Oncology Care Systems) and a Truebeam (Varian medical systems) linear accelerator following the given instructions. The systems were then tested on three different phantoms (homogeneous stack of solid water, anthropomorphic head and pelvis) and on a library of patient cases. Simple and complex fields were delivered at different exposures and for different gantry angles. The effects of the table attenuation and the EPID sagging were evaluated. Gamma analysis of the measured dose was compared to the predicted dose for complex clinical IMRT cases. Results: Commissioning of the EPIgray system for two photon energies took 8 hours. The difference between the dose planned and the dose measured with EPIgray was better than 3% for all phantom scenarios tested. Preliminary results on patients demonstrate an accuracy of 5% is achievable in high dose regions for both 3DCRT and IMRT. Large discrepancies (>5%) were observed due to metallic structures or air cavities and in low dose areas. Flat panel sagging was visible and accounted for in the EPIgray model. Conclusion: The accuracy achieved by EPIgray is sufficient to document the safe delivery of complex IMRT treatments. Future work will evaluate EPIgray for VMAT and high dose rate deliveries. This work is supported by Dosisoft, Cachan, France.

  1. WE-E-BRE-01: An Image-Based Skeletal Dosimetry Model for the ICRP Reference Adult Female - Internal Electron Sources

    SciTech Connect

    O'Reilly, S; Maynard, M; Marshall, E; Bolch, W; Sinclair, L; Rajon, D; Wayson, M

    2014-06-15

    Purpose: Limitations seen in previous skeletal dosimetry models, which are still employed in commonly used software today, include the lack of consideration of electron escape and cross-fire from cortical bone, the modeling of infinite spongiosa, the disregard of the effect of varying cellularity on active marrow self-irradiation, and the lack of use of the more recent ICRP definition of a 50 micron surrogate tissue region for the osteoprogenitor cells - shallow marrow. These limitations were addressed in the present dosimetry model. Methods: Electron transport was completed to determine specific absorbed fractions to active marrow and shallow marrow of the skeletal regions of the adult female. The bone macrostructure was obtained from the whole-body hybrid computational phantom of the UF series of reference phantoms, while the bone microstructure was derived from microCT images of skeletal region samples taken from a 45 year-old female cadaver. The target tissue regions were active marrow and shallow marrow. The source tissues were active marrow, inactive marrow, trabecular bone volume, trabecular bone surfaces, cortical bone volume and cortical bone surfaces. The marrow cellularity was varied from 10 to 100 percent for active marrow self-irradiation. A total of 33 discrete electron energies, ranging from 1 keV to 10 MeV, were either simulated or modeled analytically. Results: The method of combining macro- and microstructure absorbed fractions calculated using MCNPX electron transport was found to yield results similar to those determined with the PIRT model for the UF adult male in the Hough et al. study. Conclusion: The calculated skeletal averaged absorbed fractions for each source-target combination were found to follow similar trends of more recent dosimetry models (image-based models) and did not follow current models used in nuclear medicine dosimetry at high energies (due to that models use of an infinite expanse of trabecular spongiosa)

  2. Methodology and dosimetry in adrenal medullary imaging with iodine-131 MIBG

    SciTech Connect

    Lindberg, S.; Fjaelling, M.J.; Jacobsson, L.; Jansson, S.; Tisell, L.E.

    1988-10-01

    Iodine-131 MIBG scans were performed in 59 patients in order to localize intra- or extra-adrenal pheochromocytomas (pheos), or to visualize hyperplastic adrenal medulla. Images were obtained from the pelvis to the base of the skull on Days 1, 4, and 7 after tracer injection. The 15 patients with histopathologic confirmation of adrenal medullary disease had positive scans. In three of these, the pheos were visible only on images obtained on Day 7. One scan was false negative. After excluding patients with a predisposition to adrenal medullary disease, nine subjects (28%) without verification of pheo displayed adrenal uptake of the radionuclide. Late images produce a low rate of false-negative scans; the background activity diminishes and even small pheos can be detected. In order to increase the quality of late images, 40 MBq (/sup 131/I)MIBG was used instead of 20 MBq. The dosimetric considerations are discussed.

  3. Pulsed light imaging for wide-field dosimetry of photodynamic therapy in the skin

    NASA Astrophysics Data System (ADS)

    Davis, Scott C.; Sexton, Kristian; Chapman, Michael Shane; Maytin, Edward; Hasan, Tayyaba; Pogue, Brian W.

    2014-03-01

    Photodynamic therapy using aminoluvelinic acid (ALA) is an FDA-approved treatment for actinic keratoses, pre-cancerous skin lesions which pose a significant risk for immunocompromised individuals, such as organ transplant recipients. While PDT is generally effective, response rates vary, largely due to variations in the accumulation of the photosensitizer protoporphyrin IX (PpIX) after ALA application. The ability to quantify PpIX production before treatment could facilitate the use of additional interventions to improve outcomes. While many groups have demonstrated the ability to image PpIX in the clinic, these systems generally require darkening the room lights during imaging, which is unpopular with clinicians. We have developed a novel wide-field imaging system based on pulsed excitation and gated acquisition to image photosensitizer activity in the skin. The tissue is illuminated using four pulsed LED's to excite PpIX, and the remitted light acquired with a synchronized ICCD. This approach facilitates real-time background subtraction of ambient light, precluding the need to darken the exam room. Delivering light in short bursts also allows the use of elevated excitation intensity while remaining under the maximum permissible exposure limits, making the modality more sensitive to photosensitizer fluorescence than standard approaches. Images of tissue phantoms indicate system sensitivity down to 250nM PpIX and images of animals demonstrate detection of PpIX fluorescence in vivo under normal room light conditions.

  4. Image-based dosimetry of an implanted radioactive stent using intravascular ultrasound

    NASA Astrophysics Data System (ADS)

    Peterson, Stephen W.

    Angioplasty has become an increasingly popular and effective treatment for heart disease. Unfortunately, restenosis, a cellular and biological reaction to the procedure, has hindered its effectiveness. Two of the most successful methods of inhibiting restenosis are radiation and stents. The combination of these two components, radioactive stents, is not as common as some of the other methods, yet still has potential of slowing restenosis. Investigation into source characteristics and artery wall radiobiology may illuminate some possible solutions to the problems of restenosis. This work has developed a calculational method to look at in-vivo images of implanted stents and determine the dose to the artery walls in order to test different source characteristics. The images are Intravascular Ultrasound (IVUS) cross-sectional slices of the stent and the artery. From these images, it is possible to determine the implanted stent structure. The pieces of the stent are identified in the images and modeled in a Monte Carlo simulation, using MCNP4c3. The simulation results were combined with the images to give three-dimensional absolute dose contours of the stent. The absolute dose values were verified using radiochromic film and 198Au-plated stents. This work was able to successfully verify the dose results and create a three-dimensional dose map of the implanted stent.

  5. Dosimetry in diagnostic radiology.

    PubMed

    Meghzifene, Ahmed; Dance, David R; McLean, Donald; Kramer, Hans-Michael

    2010-10-01

    Dosimetry is an area of increasing importance in diagnostic radiology. There is a realisation amongst health professionals that the radiation dose received by patients from modern X-ray examinations and procedures can be at a level of significance for the induction of cancer across a population, and in some unfortunate instances, in the acute damage to particular body organs such as skin and eyes. The formulation and measurement procedures for diagnostic radiology dosimetry have recently been standardised through an international code of practice which describes the methodologies necessary to address the diverging imaging modalities used in diagnostic radiology. Common to all dosimetry methodologies is the measurement of the air kerma from the X-ray device under defined conditions. To ensure the accuracy of the dosimetric determination, such measurements need to be made with appropriate instrumentation that has a calibration that is traceable to a standards laboratory. Dosimetric methods are used in radiology departments for a variety of purposes including the determination of patient dose levels to allow examinations to be optimized and to assist in decisions on the justification of examination choices. Patient dosimetry is important for special cases such as for X-ray examinations of children and pregnant patients. It is also a key component of the quality control of X-ray equipment and procedures. PMID:20655679

  6. Dosimetry of an In-Line Kilovoltage Imaging System and Implementation in Treatment Planning

    SciTech Connect

    Dzierma, Yvonne; Alaei, Parham; Licht, Norbert; Rübe, Christian

    2014-03-15

    Purpose: To present the beam properties of the Siemens 70-kV and 121-kV linear accelerator-mounted imaging modalities and commissioning of the 121-kV beam in the Philips Pinnacle treatment planning system (TPS); measurements in an Alderson phantom were performed for verification of the model and to estimate the cone-beam CT (CBCT) imaging dose in the head and neck, thorax, and pelvis. Methods and Materials: The beam profiles and depth–dose curve were measured in an acrylic phantom using thermoluminescent dosimeters and a soft x-ray ionization chamber. Measurements were imported into the TPS, modeled, and verified by phantom measurements. Results: Modeling of the profiles and the depth–dose curve can be achieved with good quality. Comparison with the measurements in the Alderson phantom is generally good; only very close to bony structures is the dose underestimated by the TPS. For a 200° arc CBCT of the head and neck, a maximum dose of 7 mGy is measured; the thorax and pelvis 360° CBCTs give doses of 4-10 mGy and 7-15 mGy, respectively. Conclusions: Dosimetric characteristics of the Siemens kVision imaging modalities are presented and modeled in the Pinnacle TPS. Thermoluminescent dosimeter measurements in the Alderson phantom agree well with the calculated TPS dose, validating the model and providing an estimate of the imaging dose for different protocols.

  7. Cone-beam optical computed tomography for gel dosimetry II: imaging protocols

    NASA Astrophysics Data System (ADS)

    Olding, Tim; Schreiner, L. John

    2011-03-01

    This work develops imaging protocols for improved dose readout of a Fricke-xylenol orange-gelatin (FXG) gel-filled 1 L polyethylene terephthalate (PETE) jar dosimeter using a commercial VistaTM cone-beam optical computed tomography (CT) scanner from Modus Medical Devices Inc. (London, ON, Canada). To ensure good management of light source-detector stability, it was determined that (a) a minimum of 2 h warm-up time is necessary prior to dosimeter scanning, (b) the light source should be kept on until the completion of the last data scan except for the minimum amount of time required to acquire dark field images, and (c) the optional Vista software projection image normalization routine should be used in image reconstruction. The institution of dosimeter scan time and temperature control was strongly indicated from the experiments. A standard post-irradiation wait time of 30 min measured to within ±30 s was established to minimize the measurement uncertainties due to dosimeter development and diffusion. To alleviate thermochromic behavior leading to inaccurate dose readout, holding bath warm up and pre-scan temperature adjustment procedures were developed to control dosimeter temperature to within ±0.2 °C. The possibility of stray light minimizing protocols was also investigated and deemed to be unnecessary. The largest significant sources of stray light in the system were identified as being due to angled scatter from the dosimeter gelatin matrix and refraction from the jar wall interfaces. It was concluded that these phenomena would be better addressed through dosimeter modification and an inter-jar dose-to-attenuation calibration methodology, rather than by setting additional imaging protocols.

  8. Characterization of the homogeneous tissue mixture approximation in breast imaging dosimetry

    SciTech Connect

    Sechopoulos, Ioannis; Bliznakova, Kristina; Qin Xulei; Fei Baowei; Feng, Steve Si Jia

    2012-08-15

    Purpose: To compare the estimate of normalized glandular dose in mammography and breast CT imaging obtained using the actual glandular tissue distribution in the breast to that obtained using the homogeneous tissue mixture approximation. Methods: Twenty volumetric images of patient breasts were acquired with a dedicated breast CT prototype system and the voxels in the breast CT images were automatically classified into skin, adipose, and glandular tissue. The breasts in the classified images underwent simulated mechanical compression to mimic the conditions present during mammographic acquisition. The compressed thickness for each breast was set to that achieved during each patient's last screening cranio-caudal (CC) acquisition. The volumetric glandular density of each breast was computed using both the compressed and uncompressed classified images, and additional images were created in which all voxels representing adipose and glandular tissue were replaced by a homogeneous mixture of these two tissues in a proportion corresponding to each breast's volumetric glandular density. All four breast images (compressed and uncompressed; heterogeneous and homogeneous tissue) were input into Monte Carlo simulations to estimate the normalized glandular dose during mammography (compressed breasts) and dedicated breast CT (uncompressed breasts). For the mammography simulations the x-ray spectra used was that used during each patient's last screening CC acquisition. For the breast CT simulations, two x-ray spectra were used, corresponding to the x-ray spectra with the lowest and highest energies currently being used in dedicated breast CT prototype systems under clinical investigation. The resulting normalized glandular dose for the heterogeneous and homogeneous versions of each breast for each modality was compared. Results: For mammography, the normalized glandular dose based on the homogeneous tissue approximation was, on average, 27% higher than that estimated using the

  9. Radiation dosimetry of N-([11C]methyl)benperidol as determined by whole-body PET imaging of primates

    PubMed Central

    Antenor-Dorsey, Jo Ann V.; Laforest, Richard; Moerlein, Stephen M.; Videen, Tom O.

    2010-01-01

    Purpose N-([11C]methyl)benperidol ([11C]NMB) can be used for positron emission tomography (PET) measurements of D2-like dopamine receptor binding in vivo. We report the absorbed radiation dosimetry of i.v.-administered 11C-NMB, a critical step before applying this radioligand to imaging studies in humans. Materials and methods Whole-body PET imaging with a CTI/Siemens ECAT 953B scanner was done in a male and a female baboon. After i.v. injection of 444–1221 MBq of 11C-NMB, sequential images taken from the head to the pelvis were collected for 3 h. Volumes of interest (VOIs) were identified that entirely encompassed small organs (whole brain, striatum, eyes, and myocardium). Large organs (liver, lungs, kidneys, lower large intestine, and urinary bladder) were sampled by drawing representative regions within the organ volume. Time–activity curves for each VOI were extracted from the PET, and organ residence times were calculated by analytical integration of a multi-exponential fit of the time–activity curves. Human radiation doses were estimated using OLINDA/EXM 1.0 and the standard human model. Results Highest retention was observed in the blood and liver, each with total residence times of 1.5 min. The highest absorbed radiation doses were to the heart (10.5 mGy/kBq) and kidney (9.19 mGy/kBq), making these the critical organs for [11C]NMB. A heart absorption of 50 mGy would result from an injected dose of 4,762 MBq [11C]NMB. Conclusions Thus, this study suggests that up to 4,762 MBq of [11C]NMB can be safely administered to human subjects for PET studies. Total body dose and effective dose for [11C] NMB are 2.82 mGy/kBq and 3.7 mSv/kBq, respectively. PMID:18071701

  10. (Biological dosimetry)

    SciTech Connect

    Preston, R.J.

    1990-12-17

    The traveler attended the 1st International Conference on Biological Dosimetry in Madrid, Spain. This conference was organized to provide information to a general audience of biologists, physicists, radiotherapists, industrial hygiene personnel and individuals from related fields on the current ability of cytogenetic analysis to provide estimates of radiation dose in cases of occupational or environmental exposure. There is a growing interest in Spain in biological dosimetry because of the increased use of radiation sources for medical and occupational uses, and with this the anticipated and actual increase in numbers of overexposure. The traveler delivered the introductory lecture on Biological Dosimetry: Mechanistic Concepts'' that was intended to provide a framework by which the more applied lectures could be interpreted in a mechanistic way. A second component of the trip was to provide advice with regard to several recent cases of overexposure that had been or were being assessed by the Radiopathology and Radiotherapy Department of the Hospital General Gregorio Maranon'' in Madrid. The traveler had provided information on several of these, and had analyzed cells from some exposed or purportedly exposed individuals. The members of the biological dosimetry group were referred to individuals at REACTS at Oak Ridge Associated Universities for advice on follow-up treatment.

  11. Comparison of imaging plates with track detectors for fast-neutron dosimetry.

    PubMed

    Belafrites, A; Nourreddine, A; Mouhssine, D; Nachab, A; Pape, A; Boucenna, A; Fernández, F

    2004-01-01

    Imaging plate (IP) radiation detectors are widely used in industrial radiography, medical imagery and autoradiography. When an IP is exposed to ionising radiation, some of the energy is absorbed to form a latent image. The energy stored, which is proportional to the dose received, can be liberated by a selective optical stimulation and collected to reconstitute the distribution of the ionising radiation on the IP. In this work, IPs for use in fast-neutron measurements are characterised. The response of our IP dosemeters in conjunction with their reading system was found to be linear in dose between 75 microSv and 10 mSv. This performance is compared with those of dosemeters based on the plastic track detectors PN3 and CR-39.

  12. Cherenkov radiation dosimetry in water tanks - video rate imaging, tomography and IMRT & VMAT plan verification

    NASA Astrophysics Data System (ADS)

    Pogue, Brian W.; Glaser, Adam K.; Zhang, Rongxiao; Gladstone, David J.

    2015-01-01

    This paper presents a survey of three types of imaging of radiation beams in water tanks for comparison to dose maps. The first was simple depth and lateral profile verification, showing excellent agreement between Cherenkov and planned dose, as predicted by the treatment planning system for a square 5cm beam. The second approach was 3D tomography of such beams, using a rotating water tank with camera attached, and using filtered backprojection for the recovery of the 3D volume. The final presentation was real time 2D imaging of IMRT or VMAT treatments in a water tank. In all cases the match to the treatment planning system was within what would be considered acceptable for clinical medical physics acceptance.

  13. Dosimetry and Image Quality in Control Studies in Computerised Tomography Realized to Paediatric Patients

    SciTech Connect

    Hernandez, M. R.; Gamboa-deBuen, I.; Dies, P.; Rickards, J.; Ruiz, C.

    2008-08-11

    Computerised tomography (CT) is a favourite method of medical diagnosis. Its use has thus increased rapidly throughout the world, particularly in studies relating to children. However to avoid administering unnecessarily high doses of radiation to paediatric patients it is important to have correct dose reference levels to minimize risk. The research is being developed within the public health sector at the Hospital Infantil de Mexico 'Dr. Federico Gomez.' We measured the entrance surface air kerma (K{sub P}) in paediatric patients, during the radiological studies of control in CT (studies of head, thorax and abdomen). Phantom was used to evaluate image quality as the tomograph requires a high resolution image in order to operate at its optimum level.

  14. Comparison of imaging plates with track detectors for fast-neutron dosimetry.

    PubMed

    Belafrites, A; Nourreddine, A; Mouhssine, D; Nachab, A; Pape, A; Boucenna, A; Fernández, F

    2004-01-01

    Imaging plate (IP) radiation detectors are widely used in industrial radiography, medical imagery and autoradiography. When an IP is exposed to ionising radiation, some of the energy is absorbed to form a latent image. The energy stored, which is proportional to the dose received, can be liberated by a selective optical stimulation and collected to reconstitute the distribution of the ionising radiation on the IP. In this work, IPs for use in fast-neutron measurements are characterised. The response of our IP dosemeters in conjunction with their reading system was found to be linear in dose between 75 microSv and 10 mSv. This performance is compared with those of dosemeters based on the plastic track detectors PN3 and CR-39. PMID:15353669

  15. Use of the FLUKA Monte Carlo code for 3D patient-specific dosimetry on PET-CT and SPECT-CT images.

    PubMed

    Botta, F; Mairani, A; Hobbs, R F; Vergara Gil, A; Pacilio, M; Parodi, K; Cremonesi, M; Coca Pérez, M A; Di Dia, A; Ferrari, M; Guerriero, F; Battistoni, G; Pedroli, G; Paganelli, G; Torres Aroche, L A; Sgouros, G

    2013-11-21

    Patient-specific absorbed dose calculation for nuclear medicine therapy is a topic of increasing interest. 3D dosimetry at the voxel level is one of the major improvements for the development of more accurate calculation techniques, as compared to the standard dosimetry at the organ level. This study aims to use the FLUKA Monte Carlo code to perform patient-specific 3D dosimetry through direct Monte Carlo simulation on PET-CT and SPECT-CT images. To this aim, dedicated routines were developed in the FLUKA environment. Two sets of simulations were performed on model and phantom images. Firstly, the correct handling of PET and SPECT images was tested under the assumption of homogeneous water medium by comparing FLUKA results with those obtained with the voxel kernel convolution method and with other Monte Carlo-based tools developed to the same purpose (the EGS-based 3D-RD software and the MCNP5-based MCID). Afterwards, the correct integration of the PET/SPECT and CT information was tested, performing direct simulations on PET/CT images for both homogeneous (water) and non-homogeneous (water with air, lung and bone inserts) phantoms. Comparison was performed with the other Monte Carlo tools performing direct simulation as well. The absorbed dose maps were compared at the voxel level. In the case of homogeneous water, by simulating 10(8) primary particles a 2% average difference with respect to the kernel convolution method was achieved; such difference was lower than the statistical uncertainty affecting the FLUKA results. The agreement with the other tools was within 3–4%, partially ascribable to the differences among the simulation algorithms. Including the CT-based density map, the average difference was always within 4% irrespective of the medium (water, air, bone), except for a maximum 6% value when comparing FLUKA and 3D-RD in air. The results confirmed that the routines were properly developed, opening the way for the use of FLUKA for patient-specific, image

  16. Use of the FLUKA Monte Carlo code for 3D patient-specific dosimetry on PET-CT and SPECT-CT images*

    PubMed Central

    Botta, F; Mairani, A; Hobbs, R F; Vergara Gil, A; Pacilio, M; Parodi, K; Cremonesi, M; Coca Pérez, M A; Di Dia, A; Ferrari, M; Guerriero, F; Battistoni, G; Pedroli, G; Paganelli, G; Torres Aroche, L A; Sgouros, G

    2014-01-01

    Patient-specific absorbed dose calculation for nuclear medicine therapy is a topic of increasing interest. 3D dosimetry at the voxel level is one of the major improvements for the development of more accurate calculation techniques, as compared to the standard dosimetry at the organ level. This study aims to use the FLUKA Monte Carlo code to perform patient-specific 3D dosimetry through direct Monte Carlo simulation on PET-CT and SPECT-CT images. To this aim, dedicated routines were developed in the FLUKA environment. Two sets of simulations were performed on model and phantom images. Firstly, the correct handling of PET and SPECT images was tested under the assumption of homogeneous water medium by comparing FLUKA results with those obtained with the voxel kernel convolution method and with other Monte Carlo-based tools developed to the same purpose (the EGS-based 3D-RD software and the MCNP5-based MCID). Afterwards, the correct integration of the PET/SPECT and CT information was tested, performing direct simulations on PET/CT images for both homogeneous (water) and non-homogeneous (water with air, lung and bone inserts) phantoms. Comparison was performed with the other Monte Carlo tools performing direct simulation as well. The absorbed dose maps were compared at the voxel level. In the case of homogeneous water, by simulating 108 primary particles a 2% average difference with respect to the kernel convolution method was achieved; such difference was lower than the statistical uncertainty affecting the FLUKA results. The agreement with the other tools was within 3–4%, partially ascribable to the differences among the simulation algorithms. Including the CT-based density map, the average difference was always within 4% irrespective of the medium (water, air, bone), except for a maximum 6% value when comparing FLUKA and 3D-RD in air. The results confirmed that the routines were properly developed, opening the way for the use of FLUKA for patient-specific, image

  17. SU-E-J-215: Towards MR-Only Image Guided Identification of Calcifications and Brachytherapy Seeds: Application to Prostate and Breast LDR Implant Dosimetry

    SciTech Connect

    Elzibak, A; Fatemi-Ardekani, A; Soliman, A; Mashouf, S; Safigholi, H; Ravi, A; Morton, G; Song, WY; Han, D

    2015-06-15

    Purpose: To identify and analyze the appearance of calcifications and brachytherapy seeds on magnitude and phase MRI images and to investigate whether they can be distinguished from each other on corrected phase images for application to prostate and breast low dose rate (LDR) implant dosimetry. Methods: An agar-based gel phantom containing two LDR brachytherapy seeds (Advantage Pd-103, IsoAid, 0.8mm diameter, 4.5mm length) and two spherical calcifications (large: 7mm diameter and small: 4mm diameter) was constructed and imaged on a 3T Philips MR scanner using a 16-channel head coil and a susceptibility weighted imaging (SWI) sequence (2mm slices, 320mm FOV, TR/ TE= 26.5/5.3ms, 15 degree flip angle). The phase images were unwrapped and corrected using a 32×32, 2D Hanning high pass filter to remove background phase noise. Appearance of the seeds and calcifications was assessed visually and quantitatively using Osirix (http://www.osirix-viewer.com/). Results: As expected, calcifications and brachytherapy seeds appeared dark (hypointense) relative to the surrounding gel on the magnitude MRI images. The diameter of each seed without the surrounding artifact was measured to be 0.1 cm on the magnitude image, while diameters of 0.79 and 0.37 cm were measured for the larger and smaller calcifications, respectively. On the corrected phase images, the brachytherapy seeds and the calcifications appeared bright (hyperintense). The diameter of the seeds was larger on the phase images (0.17 cm) likely due to the dipole effect. Conclusion: MRI has the best soft tissue contrast for accurate organ delineation leading to most accurate implant dosimetry. This work demonstrated that phase images can potentially be useful in identifying brachytherapy seeds and calcifications in the prostate and breast due to their bright appearance, which helps in their visualization and quantification for accurate dosimetry using MR-only. Future work includes optimizing phase filters to best identify

  18. Small field of view cone beam CT temporomandibular joint imaging dosimetry

    PubMed Central

    Lukat, T D; Wong, J C M; Lam, E W N

    2013-01-01

    Objectives: Cone beam CT (CBCT) is generally accepted as the imaging modality of choice for visualisation of the osseous structures of the temporomandibular joint (TMJ). The purpose of this study was to compare the radiation dose of a protocol for CBCT TMJ imaging using a large field of view Hitachi CB MercuRay™ unit (Hitachi Medical Systems, Tokyo, Japan) with an alternative approach that utilizes two CBCT acquisitions of the right and left TMJs using the Kodak 9000® 3D system (Carestream, Rochester, NY). Methods: 25 optically stimulated luminescence dosemeters were placed in various locations of an anthropomorphic RANDO® Man phantom (Alderson Research Laboratories, Stanford, CT). Dosimetric measurements were performed for each technique, and effective doses were calculated using the 2007 International Commission on Radiological Protection tissue weighting factor recommendations for all protocols. Results: The radiation effective dose for the CB MercuRay technique was 223.6 ± 1.1 μSv compared with 9.7 ± 0.1 μSv (child), 13.5 ± 0.9 μSv (adolescent/small adult) and 20.5 ± 1.3 μSv (adult) for the bilateral Kodak acquisitions. Conclusions: Acquisitions of individual right and left TMJ volumes using the Kodak 9000 3D CBCT imaging system resulted in a more than ten-fold reduction in the effective dose compared with the larger single field acquisition with the Hitachi CB MercuRay. This decrease is made even more significant when lower tube potential and tube current settings are used. PMID:24048693

  19. aSi EPIDs for the in-vivo dosimetry of static and dynamic beams

    NASA Astrophysics Data System (ADS)

    Piermattei, A.; Cilla, S.; Azario, L.; Greco, F.; Russo, M.; Grusio, M.; Orlandini, L.; Fidanzio, A.

    2015-10-01

    Portal imaging by amorphous silicon (aSi) photodiode is currently the most applied technology for in-vivo dosimetry (IVD) of static and dynamic radiotherapy beams. The strategy, adopted in this work to perform the IVD procedure by aSi EPID, is based on: in patient reconstruction of the isocenter dose and day to day comparison between 2D-portal images to verify the reproducibility of treatment delivery. About 20.000 tests have been carried out in this last 3 years in 8 radiotherapy centers using the SOFTDISO program. The IVD results show that: (i) the procedure can be implemented for linacs of different manufacturer, (ii) the IVD analysis can be obtained on a computer screen, in quasi real time (about 2 min after the treatment delivery) and (iii) once the causes of the discrepancies were eliminated, all the global IVD tests for single patient were within the acceptance criteria defined by: ±5% for the isocenter dose, and Pγ<1≥90% of the checked points for the 2D portal image γ-analysis. This work is the result of a project supported by the Istituto Nazionale di Fisica Nucleare (INFN) and Università Cattolica del S.Cuore (UCSC).

  20. Neutron personnel dosimetry

    SciTech Connect

    Griffith, R.V.

    1981-06-16

    The current state-of-the-art in neutron personnel dosimetry is reviewed. Topics covered include dosimetry needs and alternatives, current dosimetry approaches, personnel monitoring devices, calibration strategies, and future developments. (ACR)

  1. Radiation dosimetry of iodine-123 HEAT, an alpha-1 receptor imaging agent

    SciTech Connect

    Thomas, K.D.; Greer, D.M.; Couch, M.W.; Williams, C.M.

    1987-11-01

    Biologic distribution data in the rat were obtained for the alpha-1 adrenoceptor imaging agent (+/-) 2-(beta-(iodo-4-hydroxyphenyl)ethylaminomethyl)tetralone (HEAT) labeled with (/sup 123/I). The major excretory routes were through the liver (67%) and the kidney (33%). Internal radiation absorbed dose estimates to nine source organs, total body, the GI tract, gonads, and red bone marrow were calculated for the human using the physical decay data for (/sup 123/I). The critical organ was found to be the lower large intestine, receiving 1.1 rad per mCi of (/sup 123/I)HEAT administered. The total-body dose was found to be 58 mrad per mCi.

  2. Biological dosimetry by chromosome aberration scoring with parallel image processing with the Heidelberg POLYP Polyprocessor system

    SciTech Connect

    Bille, J.; Scharfenberg, H.; Maenner, R.

    1983-01-01

    Chromosome aberrations in human peripheral blood are recognized parameters of cellular damage and are used as indicators of exposure to ionizing radiation. In order to reach the low dose range, up to 10,000 metaphase cells each consisting of 46 chromosomes have to be analysed for each radiation exposed person. In order to perform this task within reasonable time limits the application of the Heidelberg POLYP Polyprocessor is considered. The POLYP consists of a number of processor modules and several global memory modules which are interconnected by a multi-common-bus for parallel data transfers and a multiple synchronization bus for processor/task-scheduling. The system is designed for handling large amounts of data in real time as is typical for image processing applications.

  3. Effect of image uncertainty on the dosimetry of trigeminal neuralgia irradiation

    SciTech Connect

    Jursinic, Paul A. . E-mail: Pjursinic@radonc.mcw.edu; Rickert, Kim; Gennarelli, Thomas A.; Schultz, Christopher J.

    2005-08-01

    Objective: Our objective was to quantify the uncertainty in localization of the trigeminal nerve (TGN) with magnetic resonance imaging (MRI) and computed tomography (CT) and to determine the effect of this uncertainty on gamma-knife dose delivery. Methods: An MR/CT test phantom with 9, 0.6-mm diameter, copper rings was devised. The absolute ring positions in stereotactic space were determined by the angiographic module of the LGP software. The standard deviation, {sigma}, in the difference between the absolute and MR-measured or CT-measured coordinates of the rings was determined. The trigeminal nerve in 52 previously treated patients was contoured and expanded by 1{sigma} and 2{sigma} margins to model the uncertainty in the location of the nerve. For gamma-knife treatment, a single isocenter was used and was located at the distal cisternal portion of the trigeminal nerve root. Irradiation methods included a 4-mm collimator, 90 Gy to isocenter and a 4 and 8-mm collimator, 70 Gy to isocenter. A patient outcome survey that sampled pain relief and morbidity was done. Results: The MR coordinate {sigma} was 0.7 mm left-right, 0.8 mm anterior-posterior, and 0.6 mm superior-inferior, and the CT coordinate {sigma} was 0.4 mm left-right, 0.2 mm anterior-posterior, and 0.2 mm superior-inferior. A 45% higher dose line covered the TGN with the 4 and 8-mm method. No significant increase in pain reduction or morbidity occurred. Conclusions: The uncertainty of target location by MRI is more than twice that found in CT imaging. The 4 and 8-mm collimator method covers the trigeminal root cross section with a higher isodose line than does the 4-mm method. This higher dose did not significantly reduce pain or increase morbidity.

  4. Nd: YAG interstitial laser phototherapy guided by magnetic resonance imaging in an ex vivo model: Dosimetry of laser-MR-tissue interaction

    SciTech Connect

    Anzai, Y.; Lufkin, R.B.; Saxton, R.E.; Fetterman, H.; Farahani, K.; Layfield, L.J.; Jolesz, F.C.; Hanafee, W.H.; Castro, D.J. )

    1991-07-01

    Interstitial laser phototherapy (ILP) is a promising technique in which laser energy is delivered percutaneously to various depths of tumors. This technique will become clinically useful only when efficient, sensitive, and noninvasive monitoring systems are developed. In this study, the spatial distribution of ILP in bovine liver tissue, induced by a Nd: YAG laser with an interstitial sapphire-frosted contact probe, was evaluated by magnetic resonance imaging (MRI). Tissue was exposed to three energy densities of the Nd:YAG laser by a reproducible method of dosimetry. Thermal profiles were measured with a probe inserted 5 mm from the laser tip. T1-weighted magnetic resonance images were taken after the laser exposure. Tissue specimens were then evaluated for standard quantification of laser-induced damages. A linear correlation between the level of laser energy, induced temperature change, lesion size on T1 magnetic resonance image, and volume of histological damage was observed. Further improvement of this technique of dosimetry in an in vivo model should allow the development of software for MRI which will correlate the above parameters and render this technique of ILP clinically useful.

  5. A survey on performance status of mammography machines: image quality and dosimetry studies using a standard mammography imaging phantom.

    PubMed

    Sharma, Reena; Sharma, Sunil Dutt; Mayya, Y S

    2012-07-01

    It is essential to perform quality control (QC) tests on mammography equipment in order to produce an appropriate image quality at a lower radiation dose to patients. Imaging and dosimetric measurements on 15 mammography machines located at the busiest radiology centres of Mumbai, India were carried out using a standard CIRS breast imaging phantom in order to see the level of image quality and breast doses. The QC tests include evaluations of image quality and the mean glandular doses (MGD), which is derived from the breast entrance exposure, half-value layer (HVL), compressed breast thickness (CBT) and breast tissue compositions. At the majority of the centres, film-processing and darkroom conditions were not found to be maintained, which is required to meet the technical development specifications for the mammography film in use as recommended by the American College of Radiology (ACR). In most of the surveyed centres, the viewbox luminance and room illuminance conditions were not found to be in line with the mammography requirements recommended by the ACR. The measured HVL values of the machines were in the range of 0.27-0.39 mm aluminium (Al) with a mean value of 0.33±0.04 mm Al at 28 kV(p) following the recommendation provided by ACR. The measured MGDs were in the range of 0.14-3.80 mGy with a mean value of 1.34 mGy. The measured MGDs vary between centre to centre by a factor of 27.14. Referring to patient doses and image quality, it was observed that only one mammography centre has exceeded the recommended MGD, i.e. 3.0 mGy per view with the value of 3.80 mGy and at eight mammography centres the measured central background density (CBD) values for mammography phantom image are found to be less than the recommended CBD limit value of 1.2-2.0 optical density. PMID:22090414

  6. Evaluation of spatial resolution in image acquisition by optical flatbed scanners for radiochromic film dosimetry

    NASA Astrophysics Data System (ADS)

    Asero, G.; Greco, C.; Gueli, A. M.; Raffaele, L.; Spampinato, S.

    2016-03-01

    Introduction: Radiochromic films are two-dimensional dosimeters that do not require developing and give values of absorbed dose with accuracy and precision. Since this dosimeter colours directly after irradiation, it can be digitized with commercial optical flatbed scanners to obtain a calibration curve that links blackening of the film with dose. Although the film has an intrinsic high spatial resolution, the scanner determines the actual resolution of this dosimeter, in particular the "dot per inch" (dpi) parameter. The present study investigates the effective spatial resolution of a scanner used for Gafchromic® XR-QA2 film (designed for radiology Quality Assurance) analysis. Material and methods: The quantitative evaluation of the resolution was performed with the Modulation Transfer Function (MTF) method, comparing the nominal resolution with the experimental one. The analysis was performed with two procedures. First, the 1951 USAF resolution test chart, a tool that tests the performance of optical devices, was used. Secondly, a combined system of mammography X-ray tube, XR-QA2 film and a bar pattern object was used. In both cases the MTF method has been applied and the results were compared. Results: The USAF and the film images have been acquired with increasing dpi and a standard protocol for radiochromic analysis, to evaluate horizontal and vertical and resolution. The effective resolution corresponds to the value of the MTF at 50%. In both cases and for both procedures, it was verified that, starting from a dpi value, the effective resolution saturates. Conclusion: The study found that, for dosimetric applications, the dpi of the scanner have to be adjusted to a reasonable value because, if too high, it requires high scanning and computational time without providing additional information.

  7. Dosimetry for Radiopharmaceutical Therapy

    PubMed Central

    Sgouros, George; Hobbs, Robert F.

    2014-01-01

    Radiopharmaceutical therapy (RPT) involves the use of radionuclides that are either conjugated to tumor-targeting agents (eg, nanoscale constructs, antibodies, peptides, and small molecules) or concentrated in tissue through natural physiological mechanisms that occur predominantly in neoplastic or otherwise targeted cells (eg, Graves disease). The ability to collect pharmacokinetic data by imaging and use this to perform dosimetry calculations for treatment planning distinguishes RPT from other systemic treatment modalities. Treatment planning has not been widely adopted, in part, because early attempts to relate dosimetry to outcome were not successful. This was partially because a dosimetry methodology appropriate to risk evaluation rather than efficacy and toxicity was being applied to RPT. The weakest links in both diagnostic and therapeutic dosimetry are the accuracy of the input and the reliability of the radiobiological models used to convert dosimetric data to the relevant biologic end points. Dosimetry for RPT places a greater demand on both of these weak links. To date, most dosimetric studies have been retrospective, with a focus on tumor dose-response correlations rather than prospective treatment planning. In this regard, transarterial radioembolization also known as intra-arterial radiation therapy, which uses radiolabeled (90Y) microspheres of glass or resin to treat lesions in the liver holds much promise for more widespread dosimetric treatment planning. The recent interest in RPT with alpha-particle emitters has highlighted the need to adopt a dosimetry methodology that specifically accounts for the unique aspects of alpha particles. The short range of alpha-particle emitters means that in cases in which the distribution of activity is localized to specific functional components or cell types of an organ, the absorbed dose will be equally localized and dosimetric calculations on the scale of organs or even voxels (~5 mm) are no longer sufficient

  8. Image reconstruction algorithm for optically stimulated luminescence 2D dosimetry using laser-scanned Al2O3:C and Al2O3:C,Mg films

    NASA Astrophysics Data System (ADS)

    Ahmed, M. F.; Schnell, E.; Ahmad, S.; Yukihara, E. G.

    2016-10-01

    The objective of this work was to develop an image reconstruction algorithm for 2D dosimetry using Al2O3:C and Al2O3:C,Mg optically stimulated luminescence (OSL) films imaged using a laser scanning system. The algorithm takes into account parameters associated with detector properties and the readout system. Pieces of Al2O3:C films (~8 mm  ×  8 mm  ×  125 µm) were irradiated and used to simulate dose distributions with extreme dose gradients (zero and non-zero dose regions). The OSLD film pieces were scanned using a custom-built laser-scanning OSL reader and the data obtained were used to develop and demonstrate a dose reconstruction algorithm. The algorithm includes corrections for: (a) galvo hysteresis, (b) photomultiplier tube (PMT) linearity, (c) phosphorescence, (d) ‘pixel bleeding’ caused by the 35 ms luminescence lifetime of F-centers in Al2O3, (e) geometrical distortion inherent to Galvo scanning system, and (f) position dependence of the light collection efficiency. The algorithm was also applied to 6.0 cm  ×  6.0 cm  ×  125 μm or 10.0 cm  ×  10.0 cm  ×  125 µm Al2O3:C and Al2O3:C,Mg films exposed to megavoltage x-rays (6 MV) and 12C beams (430 MeV u‑1). The results obtained using pieces of irradiated films show the ability of the image reconstruction algorithm to correct for pixel bleeding even in the presence of extremely sharp dose gradients. Corrections for geometric distortion and position dependence of light collection efficiency were shown to minimize characteristic limitations of this system design. We also exemplify the application of the algorithm to more clinically relevant 6 MV x-ray beam and a 12C pencil beam, demonstrating the potential for small field dosimetry. The image reconstruction algorithm described here provides the foundation for laser-scanned OSL applied to 2D dosimetry.

  9. Recommendations of the American Association of Physicists in Medicine on dosimetry, imaging, and quality assurance procedures for {sup 90}Y microsphere brachytherapy in the treatment of hepatic malignancies

    SciTech Connect

    Dezarn, William A.; Cessna, Jeffery T.; DeWerd, Larry A.; and others

    2011-08-15

    Yttrium-90 microsphere brachytherapy of the liver exploits the distinctive features of the liver anatomy to treat liver malignancies with beta radiation and is gaining more wide spread clinical use. This report provides a general overview of microsphere liver brachytherapy and assists the treatment team in creating local treatment practices to provide safe and efficient patient treatment. Suggestions for future improvements are incorporated with the basic rationale for the therapy and currently used procedures. Imaging modalities utilized and their respective quality assurance are discussed. General as well as vendor specific delivery procedures are reviewed. The current dosimetry models are reviewed and suggestions for dosimetry advancement are made. Beta activity standards are reviewed and vendor implementation strategies are discussed. Radioactive material licensing and radiation safety are discussed given the unique requirements of microsphere brachytherapy. A general, team-based quality assurance program is reviewed to provide guidance for the creation of the local procedures. Finally, recommendations are given on how to deliver the current state of the art treatments and directions for future improvements in the therapy.

  10. TH-C-17A-03: Dynamic Visualization and Dosimetry of IMRT and VMAT Treatment Plans by Video-Rate Imaging of Cherenkov Radiation in Pure Water

    SciTech Connect

    Glaser, A; Andreozzi, J; Davis, S; Zhang, R; Fox, C; Gladstone, D; Pogue, B

    2014-06-15

    Purpose: A novel optical dosimetry technique for the QA and verification of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) radiotherapy plans was investigated for the first time by capturing images of the induced Cherenkov radiation in water. Methods: An intensified CCD camera (ICCD) was used to acquire a two-dimensional (2D) projection image of the Cherenkov radiation induced by IMRT and VMAT plans, based on the Task Group 119 C-Shape geometry. Plans were generated using the Varian Eclipse treatment planning system (TPS) and delivered using 6 MV x-rays from a Varian TrueBeam Linear Accelerator (Linac) incident on a water tank. The ICCD acquisition was gated to the Linac, operated for single pulse imaging, and binned to a resolution of 512×512 pixels. The resulting videos were analyzed temporally for regions of interest (ROI) covering the planning target volume (PTV) and organ at risk (OAR) and summed to obtain an overall light distribution, which was compared to the expected dose distribution from the TPS using a gammaindex analysis. Results: The chosen camera settings resulted in data at 23.5 frames per second. Temporal intensity plots of the PTV and OAR ROIs confirmed the preferential delivery of dose to the PTV versus the OAR, and the gamma analysis yielded 95.2% and 95.6% agreement between the light distribution and expected TPS dose distribution based upon a 3% / 3 mm dose difference and distance-to-agreement criterion for the IMRT and VMAT plans respectively. Conclusion: The results from this initial study demonstrate the first documented use of Cherenkov radiation for optical dosimetry of dynamic IMRT and VMAT treatment plans. The proposed modality has several potential advantages over alternative methods including the real-time nature of the acquisition, and upon future refinement may prove to be a robust and novel dosimetry method with both research and clinical applications. NIH R01CA109558 and R21EB017559.

  11. Portal radiation monitor

    DOEpatents

    Kruse, Lyle W.

    1985-01-01

    A portal radiation monitor combines 0.1% FAR with high sensitivity to special nuclear material. The monitor utilizes pulse shape discrimination, dynamic compression of the photomultiplier output and scintillators sized to maintain efficiency over the entire portal area.

  12. Portal radiation monitor

    DOEpatents

    Kruse, L.W.

    1982-03-23

    A portal radiation monitor combines .1% FAR with high sensitivity to special nuclear material. The monitor utilizes pulse shape discrimination, dynamic compression of the photomultiplier output and scintillators sized to maintain efficiency over the entire portal area.

  13. Cirrhosis and Portal Hypertension

    MedlinePlus

    MENU Return to Web version Cirrhosis and Portal Hypertension Overview What is cirrhosis? In people who have ... lead to coma and death. What is portal hypertension? Normally, blood is carried to the liver by ...

  14. Evaluation of IsoCal geometric calibration system for Varian linacs equipped with on-board imager and electronic portal imaging device imaging systems.

    PubMed

    Gao, Song; Du, Weiliang; Balter, Peter; Munro, Peter; Jeung, Andrew

    2014-01-01

    The purpose of this study is to evaluate the accuracy and reproducibility of the IsoCal geometric calibration system for kilovoltage (kV) and megavoltage (MV) imagers on Varian C-series linear accelerators (linacs). IsoCal calibration starts by imaging a phantom and collimator plate using MV images with different collimator angles, as well as MV and kV images at different gantry angles. The software then identifies objects on the collimator plate and in the phantom to determine the location of the treatment isocenter and its relation to the MV and kV imager centers. It calculates offsets between the positions of the imaging panels and the treatment isocenter as a function of gantry angle and writes a correction file that can be applied to MV and kV systems to correct for those offsets in the position of the panels. We performed IsoCal calibration three times on each of five Varian C-series linacs, each time with an independent setup. We then compared the IsoCal calibrations with a simplified Winston-Lutz (WL)-based system and with a Varian cubic phantom (VC)-based system. The maximum IsoCal corrections ranged from 0.7 mm to 1.5 mm for MV and 0.9 mm to 1.8 mm for kV imagers across the five linacs. The variations in the three calibrations for each linac were less than 0.2 mm. Without IsoCal correction, the WL results showed discrepancies between the treatment isocenter and the imager center of 0.9 mm to 1.6 mm (for the MV imager) and 0.5 mm to 1.1 mm (for the kV imager); with IsoCal corrections applied, the differences were reduced to 0.2 mm to 0.6 mm (MV) and 0.3 mm to 0.6 mm (kV) across the five linacs. The VC system was not as precise as the WL system, but showed similar results, with discrepancies of less than 1.0 mm when the IsoCal corrections were applied. We conclude that IsoCal is an accurate and consistent method for calibration and periodic quality assurance of MV and kV imaging systems.

  15. SU-E-J-84: Quantitative Dosimetry Assessment of the Impact of Image Artifacts of Metal Implants in Spinal SABR Treatment

    SciTech Connect

    Chen, T; Zhang, M; Hanft, S; Green, R; Yue, N; Goyal, S

    2015-06-15

    Purpose: Metal rods are frequently used to stabilize the spine in patients with metastatic disease. The high Z material causes imaging artifacts in the surrounding tissue in CT scans, which introduces dosimetric uncertainty when inhomogeneity correction is enabled for radiation treatment planning. The purpose of this study is to quantify the dosimetric deviations caused by the imaging artifacts and to evaluate the effectiveness of using Hounsfield units (HU) overwriting to reduce dosimetric uncertainties. Methods: We retrospectively reviewed treatment plans for 4 patients with metal implants who received stereotactic ablative radiation therapy (SABR) for metastatic disease to the spine on Tomotherapy HiArt. For all four patients, the region of imaging artifact surrounding the metal implants was contoured and the pixel HU’s were overwritten to be water equivalent. We then generated adaptive treatment plans for these patients using the MVCT pretreatment set up images and batched beamlets in the original treatment plans. The dosimetry deviation between the adaptive and original plans were compared and quantitatively analyzed. Results: For three out of four patient, the major OAR (spinal cord) dose (0.35cc or 10% according to protocols and fractionation) increased (2.7%, 5.5%, 0%, 3.9%, mean=3.0±2.3%, p=0.04), and the PTV dose (D90 or D95 as per prescription) increased for all four patients ( 2%, 5%, 0.7%, 3.6%, mean=2.8±1.9%, p=0.03) in the adaptive plan with HU overwriting. The average point dose deviation of the Tomotherapy DQA for the same patients was −1.0±1.0%. For plans without HU overwriting, the dose deviation from the treatment plan will increase. Conclusion: The metal implant and the imaging artifacts may cause a significant dosimetric impact on radiation treatment plans for spinal disease. The dose to the PTV and the spinal cord was under-calculated in treatment plans without considering the imaging artifacts. HU overwriting can reduce the dosimetry

  16. The Advent of Portals.

    ERIC Educational Resources Information Center

    Jackson, Mary E.

    2002-01-01

    Explains portals as tools that gather a variety of electronic information resources, including local library resources, into a single Web page. Highlights include cross-database searching; integration with university portals and course management software; the ARL (Association of Research Libraries) Scholars Portal Initiative; and selected vendors…

  17. Evaluating Open Source Portals

    ERIC Educational Resources Information Center

    Goh, Dion; Luyt, Brendan; Chua, Alton; Yee, See-Yong; Poh, Kia-Ngoh; Ng, How-Yeu

    2008-01-01

    Portals have become indispensable for organizations of all types trying to establish themselves on the Web. Unfortunately, there have only been a few evaluative studies of portal software and even fewer of open source portal software. This study aims to add to the available literature in this important area by proposing and testing a checklist for…

  18. Classification of cryo electron microscopy images, noisy tomographic images recorded with unknown projection directions, by simultaneously estimating reconstructions and application to an assembly mutant of Cowpea Chlorotic Mottle Virus and portals of the bacteriophage P22

    NASA Astrophysics Data System (ADS)

    Lee, Junghoon; Zheng, Yili; Yin, Zhye; Doerschuk, Peter C.; Johnson, John E.

    2010-08-01

    Cryo electron microscopy is frequently used on biological specimens that show a mixture of different types of object. Because the electron beam rapidly destroys the specimen, the beam current is minimized which leads to noisy images (SNR substantially less than 1) and only one projection image per object (with an unknown projection direction) is collected. For situations where the objects can reasonably be described as coming from a finite set of classes, an approach based on joint maximum likelihood estimation of the reconstruction of each class and then use of the reconstructions to label the class of each image is described and demonstrated on two challenging problems: an assembly mutant of Cowpea Chlorotic Mottle Virus and portals of the bacteriophage P22.

  19. Segmental portal hypertension.

    PubMed Central

    Madsen, M S; Petersen, T H; Sommer, H

    1986-01-01

    Isolated obstruction of the splenic vein leads to segmental portal hypertension, which is a rare form of extrahepatic portal hypertension, but it is important to diagnose, since it can be cured by splenectomy. In a review of the English literature, 209 patients with isolated splenic vein obstruction were found. Pancreatitis caused 65% of the cases and pancreatic neoplasms 18%, whereas the rest was caused by various other diseases. Seventy-two per cent of the patients bled from gastroesophageal varices, and most often the bleeding came from isolated gastric varices. The spleen was enlarged in 71% of the patients. A correct diagnosis in connection with the first episode of bleeding was made in only 49%; 22% were operated on because of gastrointestinal bleeding, but the cause of bleeding was not found. The diagnosis should be suspected in patients with gastroesophageal varices, but without signs of a liver disease, especially if isolated gastric varices are found. The diagnosis is confirmed by portography. Images FIG. 1. FIG. 2. PMID:3729585

  20. Evaluation of dosimetric uncertainties and transit dosimetry feasibility in pulmonary stereotactic body radiotherapy (SBRT)

    NASA Astrophysics Data System (ADS)

    Hsu, Shu-Hui

    The aims of this dissertation were to develop a method with improved accuracy for various heterogeneous geometries and to evaluate the feasibility of using EPID transit dosimetry for error detection. This dissertation examined phantom geometries with an emphasis on a tumor-in-lung geometry that may occur in hypo-fractionated SBRT treatments. For dose investigation in heterogeneous geometries, a multi-planar film measurement system was used with a measurement accuracy (within 3%) by using specific procedures to reduce the film perturbation in a low density medium. Measurements were used to validate a Monte Carlo (MC) method, and the results indicated that this MC method can be used as a reference to validate other calculation algorithms or to evaluate the doses delivered to patients for lung treatment. For developing an error detection method, a commercial electronic portal imaging device (EPID) composed of amorphous silicon was characterized for dosimetry application. A general calibration method was explored to use this device as a water-equivalent dosimeter, allowing for direct comparison to calculated doses from treatment planning systems. The calibration method was validated for a range of situations, field shapes, and intensities. The EPID transit dosimetry was sensitive to delivery errors, such as variations in treatment field shape, machine output and patient setup. The correlation between in-patient and transit dose variations may be established and used to determine acceptance or rejection criteria when the error is found. This dissertation showed the potential of using EPID dosimetry during treatment for on-line error correction and for estimating the in-patient dose error.

  1. Noncirrhotic Portal Hypertension

    PubMed Central

    Rajekar, Harshal; Vasishta, Rakesh K; Chawla, Yogesh K; Dhiman, Radha K

    2011-01-01

    Portal hypertension is characterized by an increase in portal pressure (> 10 mmHg) and could be a result of cirrhosis of the liver or of noncirrhotic diseases. When portal hypertension occurs in the absence of liver cirrhosis, noncirrhotic portal hypertension (NCPH) must be considered. The prognosis of this disease is much better than that of cirrhosis. Noncirrhotic diseases are the common cause of portal hypertension in developing countries, especially in Asia. NCPH is a heterogeneous group of diseases that is due to intrahepatic or extrahepatic etiologies. In general, the lesions in NCPH are vascular in nature and can be classified based on the site of resistance to blood flow. In most cases, these disorders can be explained by endothelial cell lesions, intimal thickening, thrombotic obliterations, or scarring of the intrahepatic portal or hepatic venous circulation. Many different conditions can determine NCPH through the association of these various lesions in various degrees. Many clinical manifestations of NCPH result from the secondary effects of portal hypertension. Patients with NCPH present with upper gastrointestinal bleeding, splenomegaly, ascites after gastrointestinal bleeding, features of hypersplenism, growth retardation, and jaundice due to portal hypertensive biliopathy. Other sequelae include hyperdynamic circulation, pulmonary complications, and other effects of portosystemic collateral circulation like portosystemic encephalopathy. At present, pharmacologic and endoscopic treatments are the treatments of choice for portal hypertension. The therapy of all disorders causing NCPH involves the reduction of portal pressure by pharmacotherapy or portosystemic shunting, apart from prevention and treatment of complications of portal hypertension. PMID:25755321

  2. SU-C-12A-04: Diagnostic Imaging Research Using Decedents as a Proxy for the Living: Are Radiation Dosimetry and Tissue Property Measurements Affected by Post-Mortem Changes?

    SciTech Connect

    Sandoval, D; Heintz, P; Weber, W; Melo, D; Adolphi, N; Hatch, P

    2014-06-01

    Purpose: Radiation dose (RD) from diagnostic imaging is a growing public health concern. Implanting dosimeters is a more accurate way to assess organ dose, relative to commonly used mathematical estimations. However, performing accurate dosimetry using live subjects is hindered by patient motion and safety considerations, which limit the RD and placement of implanted dosimeters. Performing multiple scans on the same subject would be the ideal way to assess the impact of dose reduction on image quality; however, performing multiple non-standard-of-care scans on live subjects for dosimetry and image quality measurements is generally prohibited by IRB committees. Our objective is to assess whether RD and tissue property (TP) measurements in post-mortem (PM) subjects are sufficiently similar to those in live subjects to justify the use of deceased subjects in future dosimetry and image quality studies. Methods: 4 MOSFET radiation dosimeters were placed enterically in each subject (2 sedated Rhesus Macaques) to measure the RD at 4 levels (carina, lung, heart, and liver) during CT scanning. The CT protocol was performed ante-mortem (AM) and 2 and 3 hours PM. For TP analysis, additional scans were taken at 24 hours PM. To compare AM and PM TP, regions-of-interest were drawn on selected organs and the average CT density with standard deviation (in units of HU) were taken; additionally, visual comparisons of images were made at each PM interval. Results: No significant difference was observed in 8 of 9 measurements comparing AM and PM RD. Only one measurement (liver of the first subject) showed a significant difference (7% lower on PM measurement), possibly due to subject re-positioning. Initial TP visual and quantitative analyses show little to no change PM. Conclusion: Our results suggest that realistic radiation dosimetry and image quality measurements based on tissue properties can be performed reliably on recently deceased subjects.

  3. SU-E-T-494: A MOSFET-Based In-Vivo Dosimetry System for MR Image-Guided Radiation Therapy (MR-IGRT)

    SciTech Connect

    Knutson, N; Li, H; Rodriguez, V; Hu, Y; Kashani, R; Wooten, H; Tanderup, K; Mutic, S; Green, O

    2014-06-01

    Purpose: To determine if a MOSFET based in-vivo dosimetry system can be used for patients undergoing MR-IGRT. Methods: Standard and high sensitivity MOSFET detectors were used for in-field and out-of-field measurements respectively. The systems were benchmarked and calibrated against a calibrated ionization chamber on a standard 6 MV linear accelerator, and then on the MR-IGRT system. Known doses were delivered to a water phantom with the MOSFETs placed between the top of the phantom and underneath a layer of bolus and water equivalent plastic, using a 6 MV beam and a {sup 6} {sup 0}Co MR-IGRT beam. The latter was performed with and without real-time MRI-guidance during the beam delivery (MRIGRT). Results: The in-field dosimeter response was linear from 50-500 cGy with little evidence of energy dependence or change in response due to the permanent static magnetic field of the MR-IGRT system. The detector response varied by < 2% between 6 MV and {sup 6} {sup 0}Co without image guided delivery. The out-of-field dosimeter response was linear from 1-50 cGy; however the detectors did display dose rate and energy dependence as the response varied by > 20% depending on distance from isocenter used during calibration. Therefore, to use the dosimeters for out-of-field measurements they must be calibrated out-of-field. Regardless of the detector orientation in the coronal plan, the response of the MOSFETs during MRI-guided delivery increased by 5% due to induced currents from the dynamic magnetic field present with image guidance. During the MRI-guided delivery, some loss in image quality was seen when the MOSFETs were present in the imaging plane. This was mitigated by using a handheld reader without a transmitting wireless receiver. Conclusion: A MOSFET-based in-vivo dosimetry system can be used for patients receiving MR-IGRT; however the change in detector response due to the dynamic magnetic field requires a special calibration.

  4. Quantification of activity by alpha-camera imaging and small-scale dosimetry within ovarian carcinoma micrometastases treated with targeted alpha therapy.

    PubMed

    Chouin, N; Lindegren, S; Jensen, H; Albertsson, P; Bäck, T

    2012-12-01

    Targeted alpha therapy (TAT) a promising treatment for small, residual, and micrometastatic diseases has questionable efficacy against malignant lesions larger than the α-particle range, and likely requires favorable intratumoral activity distribution. Here, we characterized and quantified the activity distribution of an alpha-particle emitter radiolabelled antibody within >100-µm micrometastases in a murine ovarian carcinoma model. Nude mice bearing ovarian micrometastases were injected intra-peritoneally with 211At-MX35 (total injected activity 6 MBq, specific activity 650 MBq/mg). Animals were sacrificed at several time points, and peritoneal samples were excised and prepared for alpha-camera imaging. Spatial and temporal activity distributions within micrometastases were derived and used for small-scale dosimetry. We observed two activity distribution patterns: uniform distribution and high stable uptake (>100% IA/g at all time points) in micrometastases with no visible stromal compartment, and radial distribution (high activity on the edge and poor uptake in the core) in tumor cell lobules surrounded by fibroblasts. Activity distributions over time were characterized by a peak (140% IA/g at 4 h) in the outer tumor layer and a sharp drop beyond a depth of 50 µm. Small-scale dosimetry was performed on a multi-cellular micrometastasis model, using time-integrated activities derived from the experimental data. With injected activity of 400 kBq, tumors exhibiting uniform activity distribution received <25 Gy (EUD=13 Gy), whereas tumors presenting radial activity distribution received mean absorbed doses of <8 Gy (EUD=5 Gy). These results provide new insight into important aspects of TAT, and may explain why micrometastases >100 µm might not be effectively treated by the examined regimen. PMID:23358400

  5. Quantification of activity by alpha-camera imaging and small-scale dosimetry within ovarian carcinoma micrometastases treated with targeted alpha therapy.

    PubMed

    Chouin, N; Lindegren, S; Jensen, H; Albertsson, P; Bäck, T

    2012-12-01

    Targeted alpha therapy (TAT) a promising treatment for small, residual, and micrometastatic diseases has questionable efficacy against malignant lesions larger than the α-particle range, and likely requires favorable intratumoral activity distribution. Here, we characterized and quantified the activity distribution of an alpha-particle emitter radiolabelled antibody within >100-µm micrometastases in a murine ovarian carcinoma model. Nude mice bearing ovarian micrometastases were injected intra-peritoneally with 211At-MX35 (total injected activity 6 MBq, specific activity 650 MBq/mg). Animals were sacrificed at several time points, and peritoneal samples were excised and prepared for alpha-camera imaging. Spatial and temporal activity distributions within micrometastases were derived and used for small-scale dosimetry. We observed two activity distribution patterns: uniform distribution and high stable uptake (>100% IA/g at all time points) in micrometastases with no visible stromal compartment, and radial distribution (high activity on the edge and poor uptake in the core) in tumor cell lobules surrounded by fibroblasts. Activity distributions over time were characterized by a peak (140% IA/g at 4 h) in the outer tumor layer and a sharp drop beyond a depth of 50 µm. Small-scale dosimetry was performed on a multi-cellular micrometastasis model, using time-integrated activities derived from the experimental data. With injected activity of 400 kBq, tumors exhibiting uniform activity distribution received <25 Gy (EUD=13 Gy), whereas tumors presenting radial activity distribution received mean absorbed doses of <8 Gy (EUD=5 Gy). These results provide new insight into important aspects of TAT, and may explain why micrometastases >100 µm might not be effectively treated by the examined regimen.

  6. WE-E-18A-08: Towards a Next-Generation Electronic Portal Device for Simultaneous Imaging and Dose Verification in Radiotherapy

    SciTech Connect

    Blake, S; Vial, P; Holloway, L; Kuncic, Z

    2014-06-15

    Purpose: This work forms part of an ongoing study to develop a next-generation electronic portal imaging device (EPID) for simultaneous imaging and dose verification in radiotherapy. Monte Carlo (MC) simulations were used to characterize the imaging performance of a novel EPID that has previously been demonstrated to exhibit a water-equivalent response. The EPID ' s response was quantified in several configurations and model parameters were empirically validated against experimental measurements. Methods: A MC model of a novel a-Si EPID incorporating an array of plastic scintillating fibers was developed. Square BCF-99-06A scintillator fibers with PMMA cladding (Saint-Gobain Crystals) were modelled in a matrix with total area measuring 150×150 mm{sup 2}. The standard electromagnetic and optical physics Geant4 classes were used to simulate radiation transport from an angled slit source (6 MV energy spectrum) through the EPID and optical photons reaching the photodiodes were scored. The prototype's modulation transfer function (MTF) was simulated and validated against experimental measurements. Several optical transport parameters, fiber lengths and thicknesses of an air gap between the scintillator and photodiodes were investigated to quantify their effects on the prototype's detection efficiency, sensitivity and MTF. Results: Simulated EPID response was more sensitive to variations in geometry than in the optical parameters studied. The MTF was particularly sensitive to the introduction of a 0.5–1.0 mm air gap between the scintillator and photodiodes, which lowered the MTF relative to that simulated without the gap. As expected, increasing the fiber length increased the detector efficiency and sensitivity while decreasing the MTF. Conclusion: A model of a novel water-equivalent EPID has been developed and benchmarked against measurements using a physical prototype. We have demonstrated the feasibility of this new device and are continuing to optimize the design

  7. Development and implementation in the Monte Carlo code PENELOPE of a new virtual source model for radiotherapy photon beams and portal image calculation

    NASA Astrophysics Data System (ADS)

    Chabert, I.; Barat, E.; Dautremer, T.; Montagu, T.; Agelou, M.; Croc de Suray, A.; Garcia-Hernandez, J. C.; Gempp, S.; Benkreira, M.; de Carlan, L.; Lazaro, D.

    2016-07-01

    This work aims at developing a generic virtual source model (VSM) preserving all existing correlations between variables stored in a Monte Carlo pre-computed phase space (PS) file, for dose calculation and high-resolution portal image prediction. The reference PS file was calculated using the PENELOPE code, after the flattening filter (FF) of an Elekta Synergy 6 MV photon beam. Each particle was represented in a mobile coordinate system by its radial position (r s ) in the PS plane, its energy (E), and its polar and azimuthal angles (φ d and θ d ), describing the particle deviation compared to its initial direction after bremsstrahlung, and the deviation orientation. Three sub-sources were created by sorting out particles according to their last interaction location (target, primary collimator or FF). For each sub-source, 4D correlated-histograms were built by storing E, r s , φ d and θ d values. Five different adaptive binning schemes were studied to construct 4D histograms of the VSMs, to ensure histogram efficient handling as well as an accurate reproduction of E, r s , φ d and θ d distribution details. The five resulting VSMs were then implemented in PENELOPE. Their accuracy was first assessed in the PS plane, by comparing E, r s , φ d and θ d distributions with those obtained from the reference PS file. Second, dose distributions computed in water, using the VSMs and the reference PS file located below the FF, and also after collimation in both water and heterogeneous phantom, were compared using a 1.5%-0 mm and a 2%-0 mm global gamma index, respectively. Finally, portal images were calculated without and with phantoms in the beam. The model was then evaluated using a 1%-0 mm global gamma index. Performance of a mono-source VSM was also investigated and led, as with the multi-source model, to excellent results when combined with an adaptive binning scheme.

  8. Development and implementation in the Monte Carlo code PENELOPE of a new virtual source model for radiotherapy photon beams and portal image calculation

    NASA Astrophysics Data System (ADS)

    Chabert, I.; Barat, E.; Dautremer, T.; Montagu, T.; Agelou, M.; Croc de Suray, A.; Garcia-Hernandez, J. C.; Gempp, S.; Benkreira, M.; de Carlan, L.; Lazaro, D.

    2016-07-01

    This work aims at developing a generic virtual source model (VSM) preserving all existing correlations between variables stored in a Monte Carlo pre-computed phase space (PS) file, for dose calculation and high-resolution portal image prediction. The reference PS file was calculated using the PENELOPE code, after the flattening filter (FF) of an Elekta Synergy 6 MV photon beam. Each particle was represented in a mobile coordinate system by its radial position (r s ) in the PS plane, its energy (E), and its polar and azimuthal angles (φ d and θ d ), describing the particle deviation compared to its initial direction after bremsstrahlung, and the deviation orientation. Three sub-sources were created by sorting out particles according to their last interaction location (target, primary collimator or FF). For each sub-source, 4D correlated-histograms were built by storing E, r s , φ d and θ d values. Five different adaptive binning schemes were studied to construct 4D histograms of the VSMs, to ensure histogram efficient handling as well as an accurate reproduction of E, r s , φ d and θ d distribution details. The five resulting VSMs were then implemented in PENELOPE. Their accuracy was first assessed in the PS plane, by comparing E, r s , φ d and θ d distributions with those obtained from the reference PS file. Second, dose distributions computed in water, using the VSMs and the reference PS file located below the FF, and also after collimation in both water and heterogeneous phantom, were compared using a 1.5%–0 mm and a 2%–0 mm global gamma index, respectively. Finally, portal images were calculated without and with phantoms in the beam. The model was then evaluated using a 1%–0 mm global gamma index. Performance of a mono-source VSM was also investigated and led, as with the multi-source model, to excellent results when combined with an adaptive binning scheme.

  9. The Detectability and Localization Accuracy of Implanted Fiducial Markers Determined on In-Room Computerized Tomography (CT) and Electronic Portal Images (EPI)

    SciTech Connect

    Owen, Rebecca Kron, Tomas; Foroudi, Farshad; Cox, Jennifer; Zhu Li; Cramb, Jim; Sparks, Laura; Duchesne, Gillian

    2008-10-01

    Many different methods of image guidance are available for radiotherapy treatment (IGRT). The aims of the study were (1) to determine the optimal diameter of gold markers for IGRT to the prostate; (2) to compare, using the Siemens Primatom, the relative merits of in-room computerized tomography (CT) and electronic portal image (EPI) for locating the marker seeds. Gold markers of differing widths were embedded in 2 phantoms (perspex slabs and anthropomorphic). Images were acquired with an amorphous silicon flat panel detector (Siemens Optivue 500) and with the in-room CT scanner (Siemens Somatom Balance). The EPIs were reviewed independently by 6 operators to determine which diameter marker could be best visualized. The optimal marker technique was determined by comparing the investigators' observed marker co-ordinates with the known locations within the phantom. The visibility of all markers on anterior-posterior EPIs was 100%. On the lateral EPI, of a possible 180 visualizations of 1.2-, 1.0-, and 0.8-mm diameter markers, 176 (97.8%), 151 (83.9%), and 132 (73.3%), respectively, were successful. On EPI, the average deviation of fiducial markers from the known position was less than 0.5 mm in any direction. On CT, the largest deviation (2.17 mm) of markers from the known coordinate position was in the superior-inferior direction, reflecting the 3.0-mm slice thickness used. EPI accurately located internal markers in all dimensions. The availability of 'gold standard' CT imagery at the treatment unit does not improve how accurately the position of markers in a phantom can be defined compared with EPI. However, CT imagery does provide important soft tissue information, the benefits of which are being investigated further.

  10. Development of Fast and Highly Efficient Gas Ionization Chamber For Patient Imaging and Dosimetry in Radiation Therapy

    SciTech Connect

    R. Hinderler; H. Keller; T.R. Mackie; M.L. Corradini

    2003-09-08

    In radiation therapy of cancer, more accurate delivery techniques spur the need for improved patient imaging during treatment. To this purpose, the megavoltage radiation protocol that is used for treatment is also used for imaging.

  11. Skeletal dosimetry for external exposures to photons based on {mu}CT images of spongiosa: Consideration of voxel resolution, cluster size, and medullary bone surfaces

    SciTech Connect

    Kramer, R.; Khoury, H. J.; Vieira, J. W.; Brown, K. A. Robson

    2009-11-15

    Skeletal dosimetry based on {mu}CT images of trabecular bone has recently been introduced to calculate the red bone marrow (RBM) and the bone surface cell (BSC) equivalent doses in human phantoms for external exposure to photons. In order to use the {mu}CT images for skeletal dosimetry, spongiosa voxels in the skeletons were replaced at run time by so-called micromatrices, which have exactly the size of a spongiosa voxel and contain segmented trabecular bone and marrow microvoxels. A cluster (=parallelepiped) of 2x2x2=8 micromatrices was used systematically and periodically throughout the spongiosa volume during the radiation transport calculation. Systematic means that when a particle leaves a spongiosa voxel to enter into a neighboring spongiosa voxel, then the next micromatrix in the cluster will be used. Periodical means that if the particle travels through more than two spongiosa voxels in a row, then the cluster will be repeated. Based on the bone samples available at the time, clusters of up to 3x3x3=27 micromatrices were studied. While for a given trabecular bone volume fraction the whole-body RBM equivalent dose showed converging results for cluster sizes between 8 and 27 micromatrices, this was not the case for the BSC equivalent dose. The BSC equivalent dose seemed to be very sensitive to the number, form, and thickness of the trabeculae. In addition, the cluster size and/or the microvoxel resolution were considered to be possible causes for the differences observed. In order to resolve this problem, this study used a bone sample large enough to extract clusters containing up to 8x8x8=512 micromatrices and which was scanned with two different voxel resolutions. Taking into account a recent proposal, this investigation also calculated the BSC equivalent dose on medullary surfaces of cortical bone in the arm and leg bones. The results showed (1) that different voxel resolutions have no effect on the RBM equivalent dose but do influence the BSC equivalent

  12. Reference dosimetry at the Australian Synchrotron's imaging and medical beamline using free-air ionization chamber measurements and theoretical predictions of air kerma rate and half value layer

    SciTech Connect

    Crosbie, Jeffrey C.; Rogers, Peter A. W.; Stevenson, Andrew W.; Hall, Christopher J.; Lye, Jessica E.; Nordstroem, Terese; Midgley, Stewart M.; Lewis, Robert A.

    2013-06-15

    Purpose: Novel, preclinical radiotherapy modalities are being developed at synchrotrons around the world, most notably stereotactic synchrotron radiation therapy and microbeam radiotherapy at the European Synchrotron Radiation Facility in Grenoble, France. The imaging and medical beamline (IMBL) at the Australian Synchrotron has recently become available for preclinical radiotherapy and imaging research with clinical trials, a distinct possibility in the coming years. The aim of this present study was to accurately characterize the synchrotron-generated x-ray beam for the purposes of air kerma-based absolute dosimetry. Methods: The authors used a theoretical model of the energy spectrum from the wiggler source and validated this model by comparing the transmission through copper absorbers (0.1-3.0 mm) against real measurements conducted at the beamline. The authors used a low energy free air ionization chamber (LEFAC) from the Australian Radiation Protection and Nuclear Safety Agency and a commercially available free air chamber (ADC-105) for the measurements. The dimensions of these two chambers are different from one another requiring careful consideration of correction factors. Results: Measured and calculated half value layer (HVL) and air kerma rates differed by less than 3% for the LEFAC when the ion chamber readings were corrected for electron energy loss and ion recombination. The agreement between measured and predicted air kerma rates was less satisfactory for the ADC-105 chamber, however. The LEFAC and ADC measurements produced a first half value layer of 0.405 {+-} 0.015 and 0.412 {+-} 0.016 mm Cu, respectively, compared to the theoretical prediction of 0.427 {+-} 0.012 mm Cu. The theoretical model based upon a spectrum calculator derived a mean beam energy of 61.4 keV with a first half value layer of approximately 30 mm in water. Conclusions: The authors showed in this study their ability to verify the predicted air kerma rate and x-ray attenuation

  13. Electronic portal imaging registration in breast cancer radiotherapy verification: analysis of inter-observer agreement among different categories of health practitioners.

    PubMed

    Jereczek-Fossa, B A; Santoro, L; Colangione, S P; Morselli, L; Fodor, C; Vischioni, B; Rozza, D; Leppa, A; Cambria, R; Leonardi, M C; Morra, A; Baroni, G; Zurrida, S; Orecchia, R

    2013-01-01

    Electronic portal imaging (EPI) is commonly used to identify and correct for inter-fraction variability in tangential breast irradiation. Based on the institutional policy, EPI registration is performed by either radiation oncologist or therapist. Little data is available on the inter-observer agreement in EPI registration among different health practitioners. The aim of our study was to analyze inter-observer agreement among radiation oncologists and therapists in the evaluation of EPI for breast cancer radiotherapy verification. EPI data of 40 patients treated with tangential fields were independently reviewed by a radiation oncologist (on-line, just before treatment) and off-line by junior and senior therapists. Displacement of each EPI image with respect to the digital reconstructed radiographs (DRRs) was quantified using manual EPI registration based on bony marks with the corresponding DRRs. Agreement between observers was evaluated using weighted Cohen's Kappa statistics. In 95% out of 720 EPI-DRR comparisons, the EPI-DRR misalignment was < 5 mm. The difference between observers was < 2 mm in 666 (92.5%) out of all 720 delta values. High inter-observer agreement was found, with weighted Cohen's Kappa values attesting evaluation overlaps ranging from moderate (among therapists) to almost perfect (among radiation oncologist and therapists). The high agreement among the observers demonstrated the precision of breast localization using EPI. These findings suggest that routine EPI-based patient set-up verification in breast cancer radiotherapy can be safely entrusted to trained therapists (supervision should be assured based on the local tasks definition). Our study might be useful in quality assurance and in the optimization of workload in the radiotherapy departments. They might allow for wider implementation of complex and evolving radiotherapy technologies. PMID:23374000

  14. SU-C-304-02: Robust and Efficient Process for Acceptance Testing of Varian TrueBeam Linacs Using An Electronic Portal Imaging Device (EPID)

    SciTech Connect

    Yaddanapudi, S; Cai, B; Sun, B; Li, H; Noel, C; Goddu, S; Mutic, S; Harry, T; Pawlicki, T

    2015-06-15

    Purpose: The purpose of this project was to develop a process that utilizes the onboard kV and MV electronic portal imaging devices (EPIDs) to perform rapid acceptance testing (AT) of linacs in order to improve efficiency and standardize AT equipment and processes. Methods: In this study a Varian TrueBeam linac equipped with an amorphous silicon based EPID (aSi1000) was used. The conventional set of AT tests and tolerances was used as a baseline guide, and a novel methodology was developed to perform as many tests as possible using EPID exclusively. The developer mode on Varian TrueBeam linac was used to automate the process. In the current AT process there are about 45 tests that call for customer demos. Many of the geometric tests such as jaw alignment and MLC positioning are performed with highly manual methods, such as using graph paper. The goal of the new methodology was to achieve quantitative testing while reducing variability in data acquisition, analysis and interpretation of the results. The developed process was validated on two machines at two different institutions. Results: At least 25 of the 45 (56%) tests which required customer demo can be streamlined and performed using EPIDs. More than half of the AT tests can be fully automated using the developer mode, while others still require some user interaction. Overall, the preliminary data shows that EPID-based linac AT can be performed in less than a day, compared to 2–3 days using conventional methods. Conclusions: Our preliminary results show that performance of onboard imagers is quite suitable for both geometric and dosimetric testing of TrueBeam systems. A standardized AT process can tremendously improve efficiency, and minimize the variability related to third party quality assurance (QA) equipment and the available onsite expertise. Research funding provided by Varian Medical Systems. Dr. Sasa Mutic receives compensation for providing patient safety training services from Varian Medical

  15. Portal Schools. Final Report.

    ERIC Educational Resources Information Center

    Lutonsky, Linda, Ed.

    The Portal School concept envisions a group of schools established in school systems that work closely with a university and that desire to participate in teacher education. This monograph represents a collection of experiences shared by initial developers of the Portal School strategy -- Florida State University, the University of Georgia, and…

  16. CT head-scan dosimetry in an anthropomorphic phantom and associated measurement of ACR accreditation-phantom imaging metrics under clinically representative scan conditions

    SciTech Connect

    Brunner, Claudia C.; Stern, Stanley H.; Chakrabarti, Kish; Minniti, Ronaldo; Parry, Marie I.; Skopec, Marlene

    2013-08-15

    Purpose: To measure radiation absorbed dose and its distribution in an anthropomorphic head phantom under clinically representative scan conditions in three widely used computed tomography (CT) scanners, and to relate those dose values to metrics such as high-contrast resolution, noise, and contrast-to-noise ratio (CNR) in the American College of Radiology CT accreditation phantom.Methods: By inserting optically stimulated luminescence dosimeters (OSLDs) in the head of an anthropomorphic phantom specially developed for CT dosimetry (University of Florida, Gainesville), we measured dose with three commonly used scanners (GE Discovery CT750 HD, Siemens Definition, Philips Brilliance 64) at two different clinical sites (Walter Reed National Military Medical Center, National Institutes of Health). The scanners were set to operate with the same data-acquisition and image-reconstruction protocols as used clinically for typical head scans, respective of the practices of each facility for each scanner. We also analyzed images of the ACR CT accreditation phantom with the corresponding protocols. While the Siemens Definition and the Philips Brilliance protocols utilized only conventional, filtered back-projection (FBP) image-reconstruction methods, the GE Discovery also employed its particular version of an adaptive statistical iterative reconstruction (ASIR) algorithm that can be blended in desired proportions with the FBP algorithm. We did an objective image-metrics analysis evaluating the modulation transfer function (MTF), noise power spectrum (NPS), and CNR for images reconstructed with FBP. For images reconstructed with ASIR, we only analyzed the CNR, since MTF and NPS results are expected to depend on the object for iterative reconstruction algorithms.Results: The OSLD measurements showed that the Siemens Definition and the Philips Brilliance scanners (located at two different clinical facilities) yield average absorbed doses in tissue of 42.6 and 43.1 m

  17. Imaging, Biodistribution, and Dosimetry of Radionuclide-Labeled PD-L1 Antibody in an Immunocompetent Mouse Model of Breast Cancer.

    PubMed

    Josefsson, Anders; Nedrow, Jessie R; Park, Sunju; Banerjee, Sangeeta Ray; Rittenbach, Andrew; Jammes, Fabien; Tsui, Benjamin; Sgouros, George

    2016-01-15

    The programmed cell death ligand 1 (PD-L1) participates in an immune checkpoint system involved in preventing autoimmunity. PD-L1 is expressed on tumor cells, tumor-associated macrophages, and other cells in the tumor microenvironment. Anti-PD-L1 antibodies are active against a variety of cancers, and combined anti-PD-L1 therapy with external beam radiotherapy has been shown to increase therapeutic efficacy. PD-L1 expression status is an important indicator of prognosis and therapy responsiveness, but methods to precisely capture the dynamics of PD-L1 expression in the tumor microenvironment are still limited. In this study, we developed a murine anti-PD-L1 antibody conjugated to the radionuclide Indium-111 ((111)In) for imaging and biodistribution studies in an immune-intact mouse model of breast cancer. The distribution of (111)In-DTPA-anti-PD-L1 in tumors as well as the spleen, liver, thymus, heart, and lungs peaked 72 hours after injection. Coinjection of labeled and 100-fold unlabeled antibody significantly reduced spleen uptake at 24 hours, indicating that an excess of unlabeled antibody effectively blocked PD-L1 sites in the spleen, thus shifting the concentration of (111)In-DTPA-anti-PD-L1 into the blood stream and potentially increasing tumor uptake. Clearance of (111)In-DTPA-anti-PD-L1 from all organs occurred at 144 hours. Moreover, dosimetry calculations revealed that radionuclide-labeled anti-PD-L1 antibody yielded tolerable projected marrow doses, further supporting its use for radiopharmaceutical therapy. Taken together, these studies demonstrate the feasibility of using anti-PD-L1 antibody for radionuclide imaging and radioimmunotherapy and highlight a new opportunity to optimize and monitor the efficacy of immune checkpoint inhibition therapy.

  18. Biodistribution and dosimetry of [123I]iodo-PK 11195: a potential agent for SPET imaging of the peripheral benzodiazepine receptor.

    PubMed

    Versijpt, J; Dumont, F; Thierens, H; Jansen, H; De Vos, F; Slegers, G; Santens, P; Dierckx, R A; Korf, J

    2000-09-01

    The highest concentrations of the peripheral benzodiazepine receptor (PBR) are found in the kidneys and heart. In addition, the PBR has been reported to reflect neuro-inflammatory damage by co-localisation with activated microglia. PK 11195 is a high-affinity ligand for the PBR. The aim of this study was to investigate in humans the biodistribution and dosimetry of [123I]iodoPK 11195, a potential single-photon emission tomography tracer for the PBR. Five healthy volunteers were injected with 112 MBq of [123I]iodo-PK 11195. Sequential whole-body scans were performed up to 72 h post injection. Multiple blood samples were taken, and urine was collected to measure the fraction voided by the renal system. Decay-corrected regions of interest of the whole-body images were analysed, and geometric mean count rates were used to determine organ activity. Organ absorbed doses and effective dose were calculated using the MIRD method. [123I]iodo-PK 11195 was rapidly cleared from the blood, mainly by the hepatobiliary system. Approximately 22% was voided in urine after 48 h. Average organ residence times were 0.74, 0.44 and 0.29 h for the liver, upper large intestine and lower large intestine, respectively. The testes received the highest dose, 109.4 microGy/MBq. All other organs investigated received doses of less than 50 microGy/MBq. The effective dose was 40.3 microSv/MBq. In conclusion, [123I]iodo-PK 11195 is a suitable agent for the visualisation of the PBR and indirectly for the imaging of neuro-inflammatory lesions. Taking into account the radiation burden of 7.46 mSv following an administration of 185 MBq, a [123I]iodo-PK 11195 investigation has to be considered an ICRP risk category IIb investigation. PMID:11007514

  19. Quasi real time in vivo dosimetry for VMAT

    SciTech Connect

    Fidanzio, A.; Azario, L.; Porcelli, A.; Greco, F.; Cilla, S.; Grusio, M.; Balducci, M.; Valentini, V.; Piermattei, A.

    2014-06-15

    Purpose: Results about the feasibility of a method for quasi real timein vivo dosimetry (IVD) at the isocenter point for volumetric modulated arc therapy (VMAT) are here reported. The method is based on correlations between the EPID signal and the dose on the beam central axis. Moreover, the γ-analysis of EPID images was adopted to verify off-axis reproducibility of fractionated plan delivery. Methods: An algorithm to reconstructin vivo the isocenter dose, D{sub iso}, for RapidArc treatments has been developed. 20 VMAT plans, optimized with two opposite arcs, for prostate, pancreas, and head treatments have been delivered by a Varian linac both to a conic PMMA phantom with elliptical section and to patients. The ratios R between reconstructed D{sub iso} and the planned doses were determined for phantom and patient irradiations adopting an acceptance criterion of ±5%. In total, 40 phantom checks and 400 patient checks were analyzed. Moreover, 3% and 3 mm criteria were adopted for portal image γ-analysis to assess patient irradiation reproducibility. Results: The average ratio R, between reconstructed and planned doses for the PMMA phantom irradiations was equal to 1.007 ± 0.024. When the IVD method was applied to the 20 patients, the average R ratio was equal to 1.003 ± 0.017 and 96% of the tests were within the acceptance criteria. The portal image γ-analysis supplied 88% of the tests within the pass rates γ{sub mean} ≤ 0.4 and P{sub γ<1} ≥ 98%. All the warnings were understood comparing the CT and the cone beam CT images and in one case a patient's setup error was detected and corrected for the successive fractions. Conclusions: This preliminary experience suggests that the method is able to detect dosimetric errors in quasi real time at the end of the therapy session. The authors intend to extend this procedure to other pathologies with the integration of in-room imaging verification by cone beam CT.

  20. Linear array measurements of enhanced dynamic wedge and treatment planning system (TPS) calculation for 15 MV photon beam and comparison with electronic portal imaging device (EPID) measurements

    PubMed Central

    Petrovic, Borislava; Grzadziel, Aleksandra; Rutonjski, Laza; Slosarek, Krzysztof

    2010-01-01

    Introduction. Enhanced dynamic wedges (EDW) are known to increase drastically the radiation therapy treatment efficiency. This paper has the aim to compare linear array measurements of EDW with the calculations of treatment planning system (TPS) and the electronic portal imaging device (EPID) for 15 MV photon energy. Materials and methods. The range of different field sizes and wedge angles (for 15 MV photon beam) were measured by the linear chamber array CA 24 in Blue water phantom. The measurement conditions were applied to the calculations of the commercial treatment planning system XIO CMS v.4.2.0 using convolution algorithm. EPID measurements were done on EPID-focus distance of 100 cm, and beam parameters being the same as for CA24 measurements. Results Both depth doses and profiles were measured. EDW linear array measurements of profiles to XIO CMS TPS calculation differ around 0.5%. Profiles in non-wedged direction and open field profiles practically do not differ. Percentage depth doses (PDDs) for all EDW measurements show the difference of not more than 0.2%, while the open field PDD is almost the same as EDW PDD. Wedge factors for 60 deg wedge angle were also examined, and the difference is up to 4%. EPID to linear array differs up to 5%. Conclusions The implementation of EDW in radiation therapy treatments provides clinicians with an effective tool for the conformal radiotherapy treatment planning. If modelling of EDW beam in TPS is done correctly, a very good agreement between measurements and calculation is obtained, but EPID cannot be used for reference measurements. PMID:22933916

  1. TU-C-BRE-10: A Streamlined Approach to EPID Transit Dosimetry

    SciTech Connect

    Morris, B; Fontenot, J

    2014-06-15

    Purpose: To investigate the feasibility of a simple and efficient transit dosimetry method using the electronic portal imaging device (EPID) for dose delivery error detection and prevention. Methods: In the proposed method, 2D reference transit images are generated for comparison with online images acquired during treatment. Reference transit images are generated by convolving through-air EPID measurements of each field with pixel-specific kernels selected from a library of pre-calculated Monte Carlo pencil kernels of varying radiological thickness. The kernel used for each pixel is selected based on the calculated radiological thickness of the patient along a line joining the pixel and the virtual source. The accuracy of the technique was evaluated in flat homogeneous and heterogeneous plastic water phantoms, a heterogeneous cylindrical phantom, and an anthropomorphic head phantom. Gamma criteria of 3%/3 mm was used to quantify the accuracy of the technique for the various cases. Results: An average of 99.9% and 99.7% of the points in the comparison between the measured and predicted images passed a 3%/3mm gamma for the homogeneous and heterogeneous plastic water phantoms, respectively. 97.1% of the points passed for the analysis of the heterogeneous cylindrical phantom. For the anthropomorphic head phantom, an average of 97.8% of points passed the 3%/3mm gamma criteria for all field sizes. Failures were observed primarily in areas of drastic thickness or material changes and at the edges of the fields. Conclusion: The data suggest that the proposed transit dosimetry method is a feasible approach to in vivo dose monitoring. Future research efforts could include implementation for more complex fields and sensitivity testing of the method to setup errors and changes in anatomy. Oncology Data Systems provided partial funding support but did not participate in the collection or analysis of data.

  2. Portal Vein Thrombosis

    PubMed Central

    Chawla, Yogesh K.; Bodh, Vijay

    2015-01-01

    Portal vein thrombosis is an important cause of portal hypertension. PVT occurs in association with cirrhosis or as a result of malignant invasion by hepatocellular carcinoma or even in the absence of associated liver disease. With the current research into its genesis, majority now have an underlying prothrombotic state detectable. Endothelial activation and stagnant portal blood flow also contribute to formation of the thrombus. Acute non-cirrhotic PVT, chronic PVT (EHPVO), and portal vein thrombosis in cirrhosis are the three main variants of portal vein thrombosis with varying etiological factors and variability in presentation and management. Procoagulant state should be actively investigated. Anticoagulation is the mainstay of therapy for acute non-cirrhotic PVT, with supporting evidence for its use in cirrhotic population as well. Chronic PVT (EHPVO) on the other hand requires the management of portal hypertension as such and with role for anticoagulation in the setting of underlying prothrombotic state, however data is awaited in those with no underlying prothrombotic states. TIPS and liver transplant may be feasible even in the setting of PVT however proper selection of candidates and type of surgery is warranted. Thrombolysis and thrombectomy have some role. TARE is a new modality for management of HCC with portal vein invasion. PMID:25941431

  3. International Reactor Dosimetry Data.

    1982-06-28

    Version 00 IRDF-82 contains 620 neutron group cross sections (SAND-II format) based on the ENDF/B-V Special Purpose Dosimetry File as well as other reaction cross sections important for dosimetry applications. In addition, multigroup spectra for ten reference benchmarks are also provided.

  4. Transit dosimetry in IMRT with an a-Si EPID in direct detection configuration

    NASA Astrophysics Data System (ADS)

    Sabet, Mahsheed; Rowshanfarzad, Pejman; Vial, Philip; Menk, Frederick W.; Greer, Peter B.

    2012-08-01

    In this study an amorphous silicon electronic portal imaging device (a-Si EPID) converted to direct detection configuration was investigated as a transit dosimeter for intensity modulated radiation therapy (IMRT). After calibration to dose and correction for a background offset signal, the EPID-measured absolute IMRT transit doses for 29 fields were compared to a MatriXX two-dimensional array of ionization chambers (as reference) using Gamma evaluation (3%, 3 mm). The MatriXX was first evaluated as reference for transit dosimetry. The accuracy of EPID measurements was also investigated by comparison of point dose measurements by an ionization chamber on the central axis with slab and anthropomorphic phantoms in a range of simple to complex fields. The uncertainty in ionization chamber measurements in IMRT fields was also investigated by its displacement from the central axis and comparison with the central axis measurements. Comparison of the absolute doses measured by the EPID and MatriXX with slab phantoms in IMRT fields showed that on average 96.4% and 97.5% of points had a Gamma index<1 in head and neck and prostate fields, respectively. For absolute dose comparisons with anthropomorphic phantoms, the values changed to an average of 93.6%, 93.7% and 94.4% of points with Gamma index<1 in head and neck, brain and prostate fields, respectively. Point doses measured by the EPID and ionization chamber were within 3% difference for all conditions. The deviations introduced in the response of the ionization chamber in IMRT fields were<1%. The direct EPID performance for transit dosimetry showed that it has the potential to perform accurate, efficient and comprehensive in vivo dosimetry for IMRT.

  5. Dosimetry for radiation processing

    NASA Astrophysics Data System (ADS)

    Miller, Arne

    During the past few years significant advances have taken place in the different areas of dosimetry for radiation processing, mainly stimulated by the increased interest in radiation for food preservation, plastic processing and sterilization of medical products. Reference services both by international organizations (IAEA) and national laboratories have helped to improve the reliability of dose measurements. Several dosimeter systems like calorimetry, perspex, and radiochromic dye films are being improved and new systems have emerged, e.g. spectrophotometry of dichromate solution for reference and sterilization dosimetry, optichromic dosimeters in the shape of small tubes for food processing, and ESR spectroscopy of alanine for reference dosimetry. In this paper the special features of radiation processing dosimetry are discussed, several commonly used dosimeters are reviewed, and factors leading to traceable and reliable dosimetry are discussed.

  6. Mechanical characterization of the Varian Exact-arm and R-arm support systems for eight aS500 electronic portal imaging devices

    SciTech Connect

    Grattan, Mark W. D.; McGarry, Conor K.

    2010-04-15

    Purpose: The aim of this study is to compare the positioning accuracy at different gantry angles of two electronic portal imaging devices (EPIDs) support arm systems by using EPID difference images as a measure for displacement. This work presents a comparison of the mechanical performance of eight Varian aS500 (Varian Medical Systems, Palo Alto, CA) EPIDs, mounted using either the Varian Exact-arm or R-arm. Methods: The mechanical performance of the two arm systems was compared by investigating the variation in sensitivity with gantry angle, both before and after the EPID position was adjusted after gantry rotation. Positional errors were investigated by subtracting images from a reference image taken at gantry 0 deg., and the amplitude of the peaks and troughs at the field edges for longitudinal (radial) and lateral (transverse) profiles across the resulting image was related to the distance of displacement. Calibration curves based on a pixel-by-pixel shift were generated for each EPID and the Varian hand pendant accuracy was compared to the calibration data. Results: The response of the EPIDs was found to change with gantry rotation, with the largest difference at 180 deg. The Exact-arm was found to correct well for any displacement, while the R-arm tended to overcorrect following repositioning using the hand pendant. The calibration curves were consistent within each set of matched linacs, and the hand pendant accuracy was similar for both arm systems, although generally in different directions. With respect to gantry rotation effects, the mechanical performance of the Exact-arm systems was found to be much better than that of the R-arm systems. At gantry positions 90 deg., 270 deg., and 180 deg. the average misalignment in the longitudinal direction was +4.2{+-}0.2, +1.8{+-}1.6, and +7.4{+-}0.5 mm for the R-arms, and +2.9{+-}0.2, +2.1{+-}0.8, and +4.9{+-}0.7 mm for the Exact-arms. In the lateral direction the average positional errors were +2.1{+-}0.4, -4

  7. High-precision γ -ray spectroscopy of the cardiac PET imaging isotope 82Rb and its impact on dosimetry

    NASA Astrophysics Data System (ADS)

    Nino, M. N.; McCutchan, E. A.; Smith, S. V.; Lister, C. J.; Greene, J. P.; Carpenter, M. P.; Muench, L.; Sonzogni, A. A.; Zhu, S.

    2016-02-01

    82Rb is a positron-emitting isotope used in cardiac positron emission tomography (PET) imaging which has been reported to deliver a significantly lower effective radiation dose than analogous imaging isotopes like 201Tl and 99 mTc sestamibi. High-quality β -decay data are essential to accurately appraise the total dose received by the patients. A source of 82Sr was produced at the Brookhaven Linac Isotope Producer (BLIP), transported to Argonne National Laboratory, and studied with the Gammasphere facility. Significant revisions have been made to the level scheme of 82Kr including 12 new levels, 50 new γ -ray transitions, and the determination of many new spin assignments through angular correlations. These new high-quality data allow a precise reappraisal of the β -decay strength function and thus the consequent dose received by patients.

  8. Multi-spectral wide-field imaging for PplX PDT dosimetry of skin (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    LaRochelle, Ethan; Chun, Hayden H.; Hasan, Tayyaba; Pogue, Brian W.; Maytin, Edward V.; Chapman, Michael S.; Davis, Scott C.

    2016-03-01

    Actinic Kertoses (AK) are common pre-cancerous lesions associated with sun-damaged skin. While generally benign, the condition can progress to squamous cell carcinoma (SCC) and is a particular concern for immunosuppressed patients who are susceptible to uncontrolled AK and SCC. Among the FDA-approved treatment options for AK, ALA-based photodynamic therapy is unique in that it is non-scarring and can be repeated on the same area. However, response rates vary widely due to variations in drug and light delivery, PpIX production, and tissue oxygenation. Thus, developing modalities to predict response is critical to enable patient-specific treatment-enhancing interventions. To that end, we have developed a wide-field spectrally-resolved fluorescence imaging system capable of red and blue light excitation. While blue light excites PpIX efficiently, poor photon penetration limits the image content to superficial layers of skin. Red light excitation, on the other hand, can reveal fluorescence information originating from deeper in tissue, which may provide relevant information about PpIX distribution. Our instrument illuminates the skin via a fiber-based ring illuminator, into which is coupled sequentially a white light source, and blue and red laser diodes. Light emitted from the tissue passes through a high-speed filter wheel with filters selected to resolve the PpIX emission spectrum. This configuration enables the use of spectral fitting to decouple PpIX fluorescence from background signal, improving sensitivity to low concentrations of PpIX. Images of tissue-simulating phantoms and animal models confirm a linear response to PpIX, and the ability to image sub-surface PpIX inaccessible with blue light using red excitation.

  9. Molecular Imaging, Pharmacokinetics, and Dosimetry of 111In-AMBA in Human Prostate Tumor-Bearing Mice

    PubMed Central

    Ho, Chung-Li; Liu, I-Hsiang; Wu, Yu-Hsien; Chen, Liang-Cheng; Chen, Chun-Lin; Lee, Wan-Chi; Chuang, Cheng-Hui; Lee, Te-Wei; Lin, Wuu-Jyh; Shen, Lie-Hang; Chang, Chih-Hsien

    2011-01-01

    Molecular imaging with promise of personalized medicine can provide patient-specific information noninvasively, thus enabling treatment to be tailored to the specific biological attributes of both the disease and the patient. This study was to investigate the characterization of DO3A-CH2CO-G-4-aminobenzoyl-Q-W-A-V-G-H-L-M-NH2 (AMBA) in vitro, MicroSPECT/CT imaging, and biological activities of 111In-AMBA in PC-3 prostate tumor-bearing SCID mice. The uptake of 111In-AMBA reached highest with 3.87 ± 0.65% ID/g at 8 h. MicroSPECT/CT imaging studies suggested that the uptake of 111In-AMBA was clearly visualized between 8 and 48 h postinjection. The distribution half-life (t1/2α) and the elimination half-life (t1/2β) of 111In-AMBA in mice were 1.53 h and 30.7 h, respectively. The Cmax and AUC of 111In-AMBA were 7.57% ID/g and 66.39 h∗% ID/g, respectively. The effective dose appeared to be 0.11 mSv/MBq−1. We demonstrated a good uptake of 111In-AMBA in the GRPR-overexpressed PC-3 tumor-bearing SCID mice. 111In-AMBA is a safe, potential molecular image-guided diagnostic agent for human GRPR-positive tumors, ranging from simple and straightforward biodistribution studies to improve the efficacy of combined modality anticancer therapy. PMID:21660132

  10. Space Development Grid Portal

    NASA Technical Reports Server (NTRS)

    Vaziri, Arsi

    2004-01-01

    This viewgraph presentation provides information on the development of a portal to provide secure and distributed grid computing for Payload Operations Integrated Center and Mission Control Center ground services.

  11. Patient-Specific Dosimetry Using Pretherapy [124I]m-iodobenzylguanidine ([124I]mIBG) Dynamic PET/CT Imaging Before [131I]mIBG Targeted Radionuclide Therapy for Neuroblastoma

    PubMed Central

    Huang, Shih-ying; Bolch, Wesley E.; Lee, Choonsik; Van Brocklin, Henry F.; Pampaloni, Miguel H.; Hawkins, Randall A.; Sznewajs, Aimee; DuBois, Steven G.; Matthay, Katherine K.; Seo, Youngho

    2014-01-01

    Purpose Iodine-131-m-iodobenzylguanidine ([131I]mIBG) targeted radionuclide therapy (TRT) is a standard treatment for recurrent or refractory neuroblastoma with response rates of 30–40%. The aim of this study is to demonstrate patient-specific dosimetry using quantitative [124I]mIBG PET/CT imaging with a Geant4-based Monte Carlo method for better treatment planning. Procedures A Monte Carlo dosimetry method was developed using the Geant4 toolkit with voxelized anatomical geometry and source distribution as input. The pre-segmented hybrid computational human phantoms developed by the University of Florida and the National Cancer Institute (UF/NCI) were used as a surrogate to characterize the anatomy of a given patient. S-values for I-131 were estimated by the phantoms coupled with Geant4 and compared with those estimated by OLINDA|EXM and MCNPX for the newborn model. To obtain patient-specific biodistribution of [131I]mIBG, a 10-year-old girl with relapsed neuroblastoma was imaged with [124I]mIBG PET/CT at four time points prior to the planned [131I]mIBG TRT. The organ and tumor absorbed dose of the clinical case were estimated with the Geant4 method using the modified UF/NCI 10-year-old phantom with tumors and the patient-specific residence time. Results For the newborn model, the Geant4 S-values were consistent with the MCNPX S- values. The S-value ratio of the Geant4 method to OLINDA|EXM ranged from 0.08 to 6.5 of all major organs. The [131I]mIBG residence time quantified from the pretherapy [124I]mIBG PET/CT imaging of the 10-year-old patient was mostly comparable to those previously reported. Organ absorbed dose for the salivary glands were 98.0 Gy, heart wall, 36.5 Gy, and liver, 34.3 Gy; while tumor absorbed dose ranged from 143.9 Gy to 1641.3 Gy in different sites. Conclusions Patient-specific dosimetry for [131I]mIBG targeted radionuclide therapy was accomplished using pretherapy [124I]mIBG PET/CT imaging and a Geant4-based Monte Carlo dosimetry method

  12. Commissioning and Implementation of an EPID Based IMRT QA System "Dosimetry Check" for 3D Absolute Dose Measurements and Quantitative Comparisons to MapCheck

    NASA Astrophysics Data System (ADS)

    Patel, Jalpa A.

    The software package "Dosimetry Check" by MathResolutions, LLC, provides an absolute 3D volumetric dose measurement for IMRT QA using the existing Electronic Portal Imaging Device (EPID) mounted on most linear accelerators. This package provides a feedback loop using the patient's treatment planning CT data as the phantom for dose reconstruction. The aim of this work is to study the difference between point, planar and volumetric doses with MapCheck and Dosimetry Check via the use of the EPID and the diode array respectively. Evaluating tools such as point doses at isocenter, 1-D profiles, gamma volume histograms, and dose volume histograms are used for IMRT dose comparison in three types of cases: head and neck, prostate, and lung. Dosimetry Check can be a valuable tool for IMRT QA as it uses patient specific attenuation corrections and the superiority of the EPID as compared to the MapCheck diode array. This helps reduce the uncertainty in dose for less variability in delivery and a more realistic measured vs computed dose verification system as compared to MapCheck.

  13. Time dependent pre-treatment EPID dosimetry for standard and FFF VMAT

    NASA Astrophysics Data System (ADS)

    Podesta, Mark; Nijsten, Sebastiaan M. J. J. G.; Persoon, Lucas C. G. G.; Scheib, Stefan G.; Baltes, Christof; Verhaegen, Frank

    2014-08-01

    Methods to calibrate Megavoltage electronic portal imaging devices (EPIDs) for dosimetry have been previously documented for dynamic treatments such as intensity modulated radiotherapy (IMRT) using flattened beams and typically using integrated fields. While these methods verify the accumulated field shape and dose, the dose rate and differential fields remain unverified. The aim of this work is to provide an accurate calibration model for time dependent pre-treatment dose verification using amorphous silicon (a-Si) EPIDs in volumetric modulated arc therapy (VMAT) for both flattened and flattening filter free (FFF) beams. A general calibration model was created using a Varian TrueBeam accelerator, equipped with an aS1000 EPID, for each photon spectrum 6 MV, 10 MV, 6 MV-FFF, 10 MV-FFF. As planned VMAT treatments use control points (CPs) for optimization, measured images are separated into corresponding time intervals for direct comparison with predictions. The accuracy of the calibration model was determined for a range of treatment conditions. Measured and predicted CP dose images were compared using a time dependent gamma evaluation using criteria (3%, 3 mm, 0.5 sec). Time dependent pre-treatment dose verification is possible without an additional measurement device or phantom, using the on-board EPID. Sufficient data is present in trajectory log files and EPID frame headers to reliably synchronize and resample portal images. For the VMAT plans tested, significantly more deviation is observed when analysed in a time dependent manner for FFF and non-FFF plans than when analysed using only the integrated field. We show EPID-based pre-treatment dose verification can be performed on a CP basis for VMAT plans. This model can measure pre-treatment doses for both flattened and unflattened beams in a time dependent manner which highlights deviations that are missed in integrated field verifications.

  14. Time dependent pre-treatment EPID dosimetry for standard and FFF VMAT.

    PubMed

    Podesta, Mark; Nijsten, Sebastiaan M J J G; Persoon, Lucas C G G; Scheib, Stefan G; Baltes, Christof; Verhaegen, Frank

    2014-08-21

    Methods to calibrate Megavoltage electronic portal imaging devices (EPIDs) for dosimetry have been previously documented for dynamic treatments such as intensity modulated radiotherapy (IMRT) using flattened beams and typically using integrated fields. While these methods verify the accumulated field shape and dose, the dose rate and differential fields remain unverified. The aim of this work is to provide an accurate calibration model for time dependent pre-treatment dose verification using amorphous silicon (a-Si) EPIDs in volumetric modulated arc therapy (VMAT) for both flattened and flattening filter free (FFF) beams. A general calibration model was created using a Varian TrueBeam accelerator, equipped with an aS1000 EPID, for each photon spectrum 6 MV, 10 MV, 6 MV-FFF, 10 MV-FFF. As planned VMAT treatments use control points (CPs) for optimization, measured images are separated into corresponding time intervals for direct comparison with predictions. The accuracy of the calibration model was determined for a range of treatment conditions. Measured and predicted CP dose images were compared using a time dependent gamma evaluation using criteria (3%, 3 mm, 0.5 sec). Time dependent pre-treatment dose verification is possible without an additional measurement device or phantom, using the on-board EPID. Sufficient data is present in trajectory log files and EPID frame headers to reliably synchronize and resample portal images. For the VMAT plans tested, significantly more deviation is observed when analysed in a time dependent manner for FFF and non-FFF plans than when analysed using only the integrated field. We show EPID-based pre-treatment dose verification can be performed on a CP basis for VMAT plans. This model can measure pre-treatment doses for both flattened and unflattened beams in a time dependent manner which highlights deviations that are missed in integrated field verifications.

  15. Thermoluminescence in medical dosimetry.

    PubMed

    Rivera, T

    2012-12-01

    Thermoluminescence dosimetry (TLD) is applied worldwide for personal and medical dosimetry. TLD method has resulted in many interesting findings in medicine as TL dosimeters have many relevant advantages such as high sensitivity, small physical size, tissue equivalence, etc. The main characteristics of various TL materials used in radiation measurements and their practical consequences are overviewed: well defined TL glow curve, batch homogeneity, signal stability after irradiation, precision and accuracy, response with dose, and influence of energy. In this paper a brief summary of the advances in the application of thermally stimulated luminescence (TSL) to dosimetry in radiation therapy application is presented.

  16. Properties of thin film radiation detectors and their application to dosimetry and quality assurance in x-ray imaging

    NASA Astrophysics Data System (ADS)

    Elshahat, Bassem

    The characteristics of two different types of thin-film radiation detectors are experimentally investigated: organic photovoltaic cells (OPV) and a new self-powered detector that operates based on high-energy secondary electrons (HEC). Although their working principles are substantially different, they both can be used for radiation detection and image formation in medical applications. OPVs with different active layer material thicknesses and aluminum electrode areas were fabricated. The OPV cell consisted of P3HT: PCBM photoactive materials, composed of donor and acceptor semiconducting organic materials, sandwiched between an aluminum electrode as anode and an indium tin oxide (ITO) electrode as a cathode. The detectors were exposed to 60150 kVp x rays, which generated photocurrent in the active layer. The electric charge production in the OPV cells was measured. The net current as function of beam energy (kVp) was proportional to ~1/kVp0.45 when adjusted for x-ray beam output. The best combination of parameters for these cells was 270-nm active layer thicknesses for 0.7cm-2 electrode area. The measured current ranged from about 0.7 to 2.4 nA/cm2 for 60-150 kVp, corresponding to about 0.09 -- 0.06 nA/cm2/mGy, respectively, when adjusted for the output x-ray source flux. The HEC detection concept was recently proposed and experimentally demonstrated by a UML/HMS research group. HEC detection employs direct conversion of high-energy electron current to detector signal without external power and amplification. The potential of using HEC detectors for diagnostic imaging application was investigated by using a heterogeneous phantom consisting of a water cylinder with Al and wax rod inserts.

  17. Spontaneous Resolution of Portal Vein Thrombosis

    PubMed Central

    Banumukala, Vishnu; Babu, Adarsh

    2008-01-01

    A 56-year-old male was admitted with symptoms of belching, abdominal pain and weight loss of 2 weeks duration. Examination revealed hepatosplenomegaly which was confirmed by computed tomography (CT). CT images also revealed filling defects in the portal vein and intrahepatic branches consistent with thrombosis and hepatosplenic infarcts. Alkaline phosphatase was elevated at 688 units, all other investigations, including full blood count, coagulation screen and tumour markers, were normal. Magnetic resonance cholangiopancreatography did not reveal any mass in the porta hepatis. Upper gastrointestinal endoscopy and colonoscopy were normal. Liver biopsy was normal and did not reveal any evidence of lymphoma. The raised alkaline phosphatase settled to reference range over a period of 3 weeks. Thrombophilia screen was negative. Contrast CT of the abdomen performed after 4 weeks displayed revascularisation of the previously thrombosed portal vein and intrahepatic branches. The patient has remained asymptomatic since and we note spontaneous recanalisation of the previously occluded portal vein. PMID:21490872

  18. Spontaneous resolution of portal vein thrombosis.

    PubMed

    Banumukala, Vishnu; Babu, Adarsh

    2008-01-01

    A 56-year-old male was admitted with symptoms of belching, abdominal pain and weight loss of 2 weeks duration. Examination revealed hepatosplenomegaly which was confirmed by computed tomography (CT). CT images also revealed filling defects in the portal vein and intrahepatic branches consistent with thrombosis and hepatosplenic infarcts. Alkaline phosphatase was elevated at 688 units, all other investigations, including full blood count, coagulation screen and tumour markers, were normal. Magnetic resonance cholangiopancreatography did not reveal any mass in the porta hepatis. Upper gastrointestinal endoscopy and colonoscopy were normal. Liver biopsy was normal and did not reveal any evidence of lymphoma. The raised alkaline phosphatase settled to reference range over a period of 3 weeks. Thrombophilia screen was negative. Contrast CT of the abdomen performed after 4 weeks displayed revascularisation of the previously thrombosed portal vein and intrahepatic branches. The patient has remained asymptomatic since and we note spontaneous recanalisation of the previously occluded portal vein. PMID:21490872

  19. A dynamic dosimetry system for prostate brachytherapy

    NASA Astrophysics Data System (ADS)

    Kuo, Nathanael; Dehghan, Ehsan; Deguet, Anton; Song, Danny Y.; Prince, Jerry L.; Lee, Junghoon

    2013-03-01

    The lack of dynamic dosimetry tools for permanent prostate brachytherapy causes otherwise avoidable problems in prostate cancer patient care. The goal of this work is to satisfy this need in a readily adoptable manner. Using the ubiquitous ultrasound scanner and mobile non-isocentric C-arm, we show that dynamic dosimetry is now possible with only the addition of an arbitrarily configured marker-based fiducial. Not only is the system easily configured from accessible hardware, but it is also simple and convenient, requiring little training from technicians. Furthermore, the proposed system is built upon robust algorithms of seed segmentation, fiducial detection, seed reconstruction, and image registration. All individual steps of the pipeline have been thoroughly tested, and the system as a whole has been validated on a study of 25 patients. The system has shown excellent results of accurately computing dose, and does so with minimal manual intervention, therefore showing promise for widespread adoption of dynamic dosimetry.

  20. Synteny Portal: a web-based application portal for synteny block analysis.

    PubMed

    Lee, Jongin; Hong, Woon-Young; Cho, Minah; Sim, Mikang; Lee, Daehwan; Ko, Younhee; Kim, Jaebum

    2016-07-01

    Recent advances in next-generation sequencing technologies and genome assembly algorithms have enabled the accumulation of a huge volume of genome sequences from various species. This has provided new opportunities for large-scale comparative genomics studies. Identifying and utilizing synteny blocks, which are genomic regions conserved among multiple species, is key to understanding genomic architecture and the evolutionary history of genomes. However, the construction and visualization of such synteny blocks from multiple species are very challenging, especially for biologists with a lack of computational skills. Here, we present Synteny Portal, a versatile web-based application portal for constructing, visualizing and browsing synteny blocks. With Synteny Portal, users can easily (i) construct synteny blocks among multiple species by using prebuilt alignments in the UCSC genome browser database, (ii) visualize and download syntenic relationships as high-quality images, (iii) browse synteny blocks with genetic information and (iv) download the details of synteny blocks to be used as input for downstream synteny-based analyses, all in an intuitive and easy-to-use web-based interface. We believe that Synteny Portal will serve as a highly valuable tool that will enable biologists to easily perform comparative genomics studies by compensating limitations of existing tools. Synteny Portal is freely available at http://bioinfo.konkuk.ac.kr/synteny_portal.

  1. Synteny Portal: a web-based application portal for synteny block analysis

    PubMed Central

    Lee, Jongin; Hong, Woon-young; Cho, Minah; Sim, Mikang; Lee, Daehwan; Ko, Younhee; Kim, Jaebum

    2016-01-01

    Recent advances in next-generation sequencing technologies and genome assembly algorithms have enabled the accumulation of a huge volume of genome sequences from various species. This has provided new opportunities for large-scale comparative genomics studies. Identifying and utilizing synteny blocks, which are genomic regions conserved among multiple species, is key to understanding genomic architecture and the evolutionary history of genomes. However, the construction and visualization of such synteny blocks from multiple species are very challenging, especially for biologists with a lack of computational skills. Here, we present Synteny Portal, a versatile web-based application portal for constructing, visualizing and browsing synteny blocks. With Synteny Portal, users can easily (i) construct synteny blocks among multiple species by using prebuilt alignments in the UCSC genome browser database, (ii) visualize and download syntenic relationships as high-quality images, (iii) browse synteny blocks with genetic information and (iv) download the details of synteny blocks to be used as input for downstream synteny-based analyses, all in an intuitive and easy-to-use web-based interface. We believe that Synteny Portal will serve as a highly valuable tool that will enable biologists to easily perform comparative genomics studies by compensating limitations of existing tools. Synteny Portal is freely available at http://bioinfo.konkuk.ac.kr/synteny_portal. PMID:27154270

  2. NMR mechanisms in gel dosimetry

    NASA Astrophysics Data System (ADS)

    Schreiner, L. J.

    2009-05-01

    Nuclear magnetic resonance was critical to the development of gel dosimetry, as it established the potential for three dimensional dosimetry with chemical dosimeter systems through magnetic resonance imaging [1]. In the last two decades MRI has served as the gold standard for imaging, while NMR relaxometry has played an important role in the development and understanding of the behaviour of new gel dosimetry systems. Therefore, an appreciation of the relaxation mechanisms determining the NMR behaviour of irradiated gel dosimeters is important for a full comprehension of a considerable component of the literature on gel dosimetry. A number of excellent papers have presented this important theory, this brief review will highlight some of the salient points made previously [1-5]. The spin relaxation of gel dosimeters (which determines the dose dependence in most conventional MR imaging) is determined principally by the protons on water molecules in the system. These water protons exist in different environments, or groups (see Figure 1): on bulk water, on water hydrating the chemical species that are being modified under irradiation, and on water hydrating the gel matrix used to spatially stabilize the dosimeter (e.g., gelatin, agarose, etc). The spin relaxation depends on the inherent relaxation rate of each spin group, that is, on the relaxation rate which would be observed for the specific group if it were isolated. Also, the different water environments are not isolated from each other, and the observed relaxation rate also depends on the rate of exchange of magnetization between the groups, and on the fraction of protons in each group. In fact, the water exchanges quickly between the environments, so that relaxation is in what is usually termed the fast exchange regime. In the limit of fast exchange, the relaxation of the water protons is well characterized by a single exponential and hence by a single apparent relaxation rate. In irradiated gel dosimeters this

  3. Nitroglycerine effects on portal vein mechanics and oxidative stress in portal hypertension

    PubMed Central

    Vujanac, Andreja; Jakovljevic, Vladimir; Djordjevic, Dusica; Zivkovic, Vladimir; Stojkovic, Mirjana; Celikovic, Dragan; Andjelkovic, Nebojsa; Skevin, Aleksandra Jurisic; Djuric, Dragan

    2012-01-01

    AIM: Тo examine the effects of nitroglycerine on portal vein haemodynamics and oxidative stress in patients with portal hypertension. METHODS: Thirty healthy controls and 39 patients with clinically verified portal hypertension and increased vascular resistance participated in the study. Liver diameters, portal diameters and portal flow velocities were recorded using color flow imaging/pulsed Doppler detection. Cross-section area, portal flow and index of vascular resistance were calculated. In collected blood samples, superoxide anion radical (O2-), hydrogen peroxide (H2O2), index of lipid peroxidation (measured as TBARS) and nitric oxide (NO) as a marker of endothelial response (measured as nitrite-NO2-) were determined. Time-dependent analysis was performed at basal state and in 10th and 15th min after nitroglycerine (sublingual 0.5 mg) administration. RESULTS: Oxidative stress parameters changed significantly during the study. H2O2 decreased at the end of study, probably via O2- mediated disassembling in Haber Weiss and Fenton reaction; O2- increased significantly probably due to increased diameter and tension and decreased shear rate level. Consequently O2- and H2O2 degradation products, like hydroxyl radical, initiated lipid peroxidation. Increased blood flow was to some extent lower in patients than in controls due to double paradoxes, flow velocity decreased, shear rate decreased significantly indicating non Newtonian characteristics of portal blood flow. CONCLUSION: This pilot study could be a starting point for further investigation and possible implementation of some antioxidants in the treatment of portal hypertension. PMID:22294839

  4. Radioisotopic flow scanning for portal blood flow and portal hypertension

    SciTech Connect

    Hesdorffer, C.S.; Bezwoda, W.R.; Danilewitz, M.D.; Esser, J.D.; Tobias, M.

    1987-08-01

    The use of a simple, noninvasive, isotope scanning technique for the determination of relative portal blood flow and detection of portal hypertension is described. Using this technique the presence of portal hypertension was demonstrated in seven of nine patients known to have elevated portal venous pressure. By contrast, esophageal varices were demonstrated in only five of these patients, illustrating the potential value of the method. Furthermore, this technique has been adapted to the study of portal blood flow in patients with myeloproliferative disorders with splenomegaly but without disturbances in hepatic architecture. Results demonstrate that the high relative splenic flow resulting from the presence of splenomegaly may in turn be associated with elevated relative portal blood flow and portal hypertension. The theoretic reasons for the development of flow-related portal hypertension and its relationship to splenic blood flow are discussed.

  5. 8. EAST PORTAL AND DECK VIEW, FROM EAST, SHOWING PORTAL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. EAST PORTAL AND DECK VIEW, FROM EAST, SHOWING PORTAL CONFIGURATION AND LATERAL BRACING, STEEL MESH FLOOR, METAL RAILINGS, AND PORTION OF EAST APPROACH - Glendale Road Bridge, Spanning Deep Creek Lake on Glendale Road, McHenry, Garrett County, MD

  6. 7. WEST PORTAL AND DECK VIEW, FROM WEST, SHOWING PORTAL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. WEST PORTAL AND DECK VIEW, FROM WEST, SHOWING PORTAL CONFIGURATION AND LATERAL BRACING, STEEL MESH FLOOR, AND METAL RAILINGS - Glendale Road Bridge, Spanning Deep Creek Lake on Glendale Road, McHenry, Garrett County, MD

  7. Perspective view of south portal. Note how portal angles about ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Perspective view of south portal. Note how portal angles about 5' forward over the approach. - Red Oak Creek Bridge, Spanning (Big) Red Oak Creek, Huel Brown Road (Covered Bridge Road), Woodbury, Meriwether County, GA

  8. Elevation, west portal. Sign on portal reads Watson Mill Bridge, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Elevation, west portal. Sign on portal reads Watson Mill Bridge, est. 1885. - Watson Mill Bridge, Spanning South Fork Broad River, Watson Mill Road, Watson Mill Bridge State Park, Comer, Madison County, GA

  9. Optically stimulated luminescence dosimetry

    NASA Astrophysics Data System (ADS)

    McKeever, Stephen W. S.

    2001-09-01

    Models and the conceptual framework necessary for an understanding of optically stimulated luminescence (OSL) are described. Examples of various OSL readout schemes are described, along with examples of the use of OSL in radiation dosimetry.

  10. Pregnancy with Portal Hypertension

    PubMed Central

    Aggarwal, Neelam; Negi, Neha; Aggarwal, Aakash; Bodh, Vijay; Dhiman, Radha K.

    2014-01-01

    Even though pregnancy is rare with cirrhosis and advanced liver disease, but it may co-exist in the setting of non-cirrhotic portal hypertension as liver function is preserved but whenever encountered together is a complex clinical dilemma. Pregnancy in a patient with portal hypertension presents a special challenge to the obstetrician as so-called physiological hemodynamic changes associated with pregnancy, needed for meeting demands of the growing fetus, worsen the portal hypertension thereby putting mother at risk of potentially life-threatening complications like variceal hemorrhage. Risks of variceal bleed and hepatic decompensation increase many fold during pregnancy. Optimal management revolves round managing the portal hypertension and its complications. Thus management of such cases requires multi-speciality approach involving obstetricians experienced in dealing with high risk cases, hepatologists, anesthetists and neonatologists. With advancement in medical field, pregnancy is not contra-indicated in these women, as was previously believed. This article focuses on the different aspects of pregnancy with portal hypertension with special emphasis on specific cause wise treatment options to decrease the variceal bleed and hepatic decompensation. Based on extensive review of literature, management from pre-conceptional period to postpartum is outlined in order to have optimal maternal and perinatal outcomes. PMID:25755552

  11. Optical tomography for radiation dosimetry and treatment plan verification by videographic imaging of ferrous sulphate xylenol orange gelatin dosimeters

    NASA Astrophysics Data System (ADS)

    Wolodzko, John George

    1999-08-01

    Recent advances in computer and radiation delivery technologies have led to new and complex methods in radiotherapy which involve the deposition of radiation in the human body at high doses or dose rates. Both these and more traditional approaches to radiotherapy would benefit from a means to provide detailed information about the distribution of radiation dose in multiple dimensions for the purposes of treatment planning and verification. Several investigations have been carried out over the past few years to evaluate the utility of various formulations of ferrous sulphate, or Fricke, get dosimeters in the measurement of radiation fields. These have been proposed to be of particular value in the determination of three-dimensional radiation dose distributions associated with emerging and complex approaches to cancer treatment such as `gamma knife', pencil beam, stereotactic, or conformal radiotherapies. Hitherto, the emphasis in the majority of approaches has been on measuring the difference in effect on paramagnetic properties between the initial ferrous ion concentration of the solution, and the ferric ions which a produced following irradiation. Although many positive and confirmative results have been published regarding this method, it relies on access to clinical MRI units for imaging the irradiated gel; an expensive and logistical challenge for the majority of potential users. We report here a study carried out to determine the feasibility of analyzing one form of this dosimeter through tomographic reconstruction of two-dimensional optical projections acquired using an ordinary, diffuse light source, video camera, standard tomographic reconstruction software, and other components designed and/or assembled by the author. Qualitative, quantitative and statistical analyses yield highly linear and reproducible results with r2 from regression analyses typically on the order of 0.98. Comparisons of the measured dose distribution patterns to the treatment plan

  12. Target detection portal

    DOEpatents

    Linker, Kevin L.; Brusseau, Charles A.

    2002-01-01

    A portal apparatus for screening persons or objects for the presence of trace amounts of target substances such as explosives, narcotics, radioactive materials, and certain chemical materials. The portal apparatus can have a one-sided exhaust for an exhaust stream, an interior wall configuration with a concave-shape across a horizontal cross-section for each of two facing sides to result in improved airflow and reduced washout relative to a configuration with substantially flat parallel sides; air curtains to reduce washout; ionizing sprays to collect particles bound by static forces, as well as gas jet nozzles to dislodge particles bound by adhesion to the screened person or object. The portal apparatus can be included in a detection system with a preconcentrator and a detector.

  13. Clinical Manifestations of Portal Hypertension

    PubMed Central

    Al-Busafi, Said A.; McNabb-Baltar, Julia; Farag, Amanda; Hilzenrat, Nir

    2012-01-01

    The portal hypertension is responsible for many of the manifestations of liver cirrhosis. Some of these complications are the direct consequences of portal hypertension, such as gastrointestinal bleeding from ruptured gastroesophageal varices and from portal hypertensive gastropathy and colopathy, ascites and hepatorenal syndrome, and hypersplenism. In other complications, portal hypertension plays a key role, although it is not the only pathophysiological factor in their development. These include spontaneous bacterial peritonitis, hepatic encephalopathy, cirrhotic cardiomyopathy, hepatopulmonary syndrome, and portopulmonary hypertension. PMID:23024865

  14. A Librarian's Perspective on Portals.

    ERIC Educational Resources Information Center

    Little, John R.

    2001-01-01

    Explains what Web portals are and discusses the benefits of a strategic alliance in portal building among campus information technology, libraries, and other campus groups. Suggests that by using robust channel capabilities, an enterprise portal can provide content from various parts of the university and promote resource discovery. (EV)

  15. Ten Keys to the Portal

    ERIC Educational Resources Information Center

    Schaffhauser, Dian

    2011-01-01

    Successful web portals help users stay informed, in touch, and up to speed. They are also a telling window into the efficiency of one's institution. To develop a cutting-edge portal takes planning, communication, and research. In this article, the author presents and discusses 10 keys to portal success: (1) make critical info visible; (2) make the…

  16. Improvement of Varian a-Si EPID dosimetry measurements using a lead-shielded support-arm

    SciTech Connect

    Rowshanfarzad, Pejman; Sabet, Mahsheed; O'Connor, Daryl J.; Greer, Peter B.

    2012-07-01

    Dosimetry measurements with Varian amorphous silicon electronic portal imaging devices (a-Si EPIDs) are affected by the backscattered radiation from the EPID support arm. In this study, the nonuniform backscatter from an E-type support arm was reduced by fixing a thick (12.2 Multiplication-Sign 10.5 Multiplication-Sign 0.5 cm{sup 3}) piece of lead on top of the arm, and the remaining backscatter was modeled and included in an existing dose prediction algorithm. The applied backscatter kernel was the average of kernels on different regions of the EPID over the arm. The lead-shielded arm reduced the nonuniform backscatter component by about 50% for field sizes ranging from 3 Multiplication-Sign 3 to 30 Multiplication-Sign 30 cm{sup 2} and the field symmetry improved for medium to large fields up to 3%. Gamma evaluation of the measured and modeled doses (2%, 2-mm criteria) showed that using the lead-shielded arm in the model increased the number of points with Gamma index <1 by 5.7% and decreased the mean Gamma by 0.201. Even using the lead alone (no modeling) could increase the number of points with Gamma index <1 by 4.7% and decrease the mean Gamma by 0.153. This is a simple and easy method to decrease the nonuniform arm backscatter and improve the accuracy of dosimetry measurements with the existing EPIDs used for clinical applications.

  17. Application of the smart portal in transportation

    NASA Astrophysics Data System (ADS)

    Kercel, Stephen W.; Baylor, Vivian M.; Dress, William B.; Hickerson, Tim W.; Jatko, W. Bruce; Labaj, Leo E.; Muhs, Jeffrey D.; Pack, Richard M.

    1997-02-01

    Under a program sponsored by the Department of Energy, the Oak Ridge complex is developing a `Portal-of-the-Future', or `smart portal.' This is a security portal for vehicular traffic which is intended to quickly detect explosives, hidden passengers, etc. It uses several technologies, including microwaves, weigh-in-motion, digital image processing, and electroacoustic wavelet-based heartbeat detection. A novel component of particular interest is the Enclosed Space Detection System (ESDS), which detects the presence of persons hiding in a vehicle. The system operates by detecting the presence of a human ballistocardiographic signature. Each time the heart beats, it generates a small but measurable shock wave that propagates through the body. The wave, whose graph is called a ballistocardiogram, is the mechanical analog of the electrocardiograms, which is routinely used for medical diagnosis. The wave is, in turn, coupled to any surface or object with which the body is in contact. If the body is located in an enclosed space, this will result in a measurable deflection of the surface of the enclosure. Independent testing has shown ESDS to be highly reliable. The technologies used in the smart portal operate in real time and allow vehicles to be checked through the portal in much less time than would be required for human inspection. Although not originally developed for commercial transportation, the smart portal has the potential to solve several transportation problems. It could relieve congestion at international highway border crossings by reducing the time required to inspect each vehicle while increasing the level of security. It can reduce highway congestion at the entrance of secure facilities such as prisons. Also, it could provide security at intermodal transfer points, such as airport parking lots and car ferry terminals.

  18. Application of the smart portal in transportation

    SciTech Connect

    Kercel, S.W.; Baylor, V.M.; Dress, W.B.; Hickerson, T.W.; Jatko, W.B.; Labaj, L.E.; Muhs, J.D.; Pack, R.M.

    1996-12-31

    Under a program sponsored by the Department of Energy, the Oak Ridge complex is developed a ``Portal-of-the-Future``, or ``smart portal``. This is a security portal for vehicular traffic which is intended to quickly detect explosives, hidden passengers, etc. It uses several technologies, including microwaves, weigh-in-motion, digital image processing, and electroacoustic wavelet-based heartbeat detection. A novel component of particular interest is the Enclosed Space Detection System (ESDS), which detects the presence of persons hiding in a vehicle. The system operates by detecting the presence of a human ballistocardiographic signature. Each time the heart beats, it generates a small but measurable shock wave that propagates through the body. The wave, whose graph is called a ballistocardiogram, is the mechanical analog of the electrocardiogram, which is routinely used for medical diagnosis. The wave is, in turn, coupled to any surface or object with which the body is in contact. If the body is located in an enclosed space, this will result in a measurable deflection of the surface of the enclosure. Independent testing has shown ESDS to be highly reliable. The technologies used in the smart portal operate in real time and allow vehicles to be checked through the portal in much less time than would be required for human inspection. Although not originally developed for commercial transportation, the smart portal has the potential to solve several transportation problems. It could relieve congestion at international highway border crossings by reducing the time required to inspect each vehicle while increasing the level of security. It can reduce highway congestion at the entrance of secure facilities such as prisons. Also, it could provide security at intermodal transfer points, such as airport parking lots and car ferry terminals.

  19. Clinical experience with EPID dosimetry for prostate IMRT pre-treatment dose verification

    SciTech Connect

    McDermott, L. N.; Wendling, M.; Asselen, B. van; Stroom, J.; Sonke, J.-J.; Herk, M. van; Mijnheer, B. J.

    2006-10-15

    The aim of this study was to demonstrate how dosimetry with an amorphous silicon electronic portal imaging device (a-Si EPID) replaced film and ionization chamber measurements for routine pre-treatment dosimetry in our clinic. Furthermore, we described how EPID dosimetry was used to solve a clinical problem. IMRT prostate plans were delivered to a homogeneous slab phantom. EPID transit images were acquired for each segment. A previously developed in-house back-projection algorithm was used to reconstruct the dose distribution in the phantom mid-plane (intersecting the isocenter). Segment dose images were summed to obtain an EPID mid-plane dose image for each field. Fields were compared using profiles and in two dimensions with the {gamma} evaluation (criteria: 3%/3 mm). To quantify results, the average {gamma} ({gamma}{sub avg}), maximum {gamma} ({gamma}{sub max}), and the percentage of points with {gamma}<1(P{sub {gamma}}{sub lt1}) were calculated within the 20% isodose line of each field. For 10 patient plans, all fields were measured with EPID and film at gantry set to 0 deg. . The film was located in the phantom coronal mid-plane (10 cm depth), and compared with the back-projected EPID mid-plane absolute dose. EPID and film measurements agreed well for all 50 fields, with <{gamma}{sub avg}>=0.16, <{gamma}{sub max}>=1.00, and =100%. Based on these results, film measurements were discontinued for verification of prostate IMRT plans. For 20 patient plans, the dose distribution was re-calculated with the phantom CT scan and delivered to the phantom with the original gantry angles. The planned isocenter dose (plan{sub iso}) was verified with the EPID (EPID{sub iso}) and an ionization chamber (IC{sub iso}). The average ratio, , was 1.00 (0.01 SD). Both measurements were systematically lower than planned, with and =0.99 (0.01 SD). EPID mid-plane dose images for

  20. Epid cine acquisition mode for in vivo dosimetry in dynamic arc radiation therapy

    NASA Astrophysics Data System (ADS)

    Fidanzio, Andrea; Mameli, Alessandra; Placidi, Elisa; Greco, Francesca; Stimato, Gerardina; Gaudino, Diego; Ramella, Sara; D'Angelillo, Rolando; Cellini, Francesco; Trodella, Lucio; Cilla, Savino; Grimaldi, Luca; D'Onofrio, Guido; Azario, Luigi; Piermattei, Angelo

    2008-02-01

    In this paper the cine acquisition mode of an electronic portal imaging device (EPID) has been calibrated and tested to determine the in vivo dose for dynamic conformal arc radiation therapy (DCAT). The EPID cine acquisition mode, that allows a frame acquisition rate of one image every 1.66 s, was studied with a monitor unit rate equal to 100 UM/min. In these conditions good signal stability, ±1% (2SD) evaluated during three months, signal reproducibility within ±0.8% (2SD) and linearity with dose and dose rate within ±1% (2SD) were obtained. The transit signal, St, (due to the transmitted beam below the phantom) measured by the EPID cine acquisition mode was used to determine, (i) a set of correlation functions, F(w,L), defined as the ratio between St and the dose at half thickness, Dm, measured in solid water phantoms of different thicknesses, w and with square fields of side L, (ii) a set of factors, f(d,L), that take into account the different X-ray scatter contribution from the phantom to the St signal as a function of the variation, d, of the air gap between the phantom and the EPID. The reconstruction of the isocenter dose, Diso, for DCAT was obtained convolving the transit signal values, obtained at different gantry angles, with the respective reconstruction factors determined by a house-made software. The method was tested with cylindrical and anthropomorphic phantoms and the results show that the reconstructed Diso values can be obtained with an accuracy within ±2.5% in cylindrical phantom and within ±3.4% for anthropomorphic phantom. In conclusion, the transit dosimetry by EPID was assessed to be adequate to perform DCAT in vivo dosimetry, that is not realizable with the other traditional techniques. Moreover, the method proposed here could be implemented to supply in vivo dose values in real time.

  1. Extensive portal venous gas: Unlikely etiology and outcome.

    PubMed

    Schatz, Tiffany P; Nassif, Mohammed O; Farma, Jeffrey M

    2015-01-01

    Portal venous gas or hepatic portal venous gas (HPVG) found on imaging portends grave outcomes for patients suffering from ischemic bowel disease or mesenteric ischemia. HPVG is more rarely seen with severe but treatable abdominal infection as well as multiple benign conditions, and therefore must be aggressively evaluated. We report a 70-year old female who developed extensive intra- and extra-hepatic portal venous gas, pneumatosis intestinalis and free air associated with a perforation of the jejunojejunostomy after a gastrectomy for gastric carcinoma.

  2. Portal annular pancreas: the pancreatic duct ring sign on MRCP

    PubMed Central

    Lath, Chinar O.; Agrawal, Dilpesh S.; Timins, Michael E.; Wein, Melissa M.

    2015-01-01

    Portal annular pancreas is a rare pancreatic variant in which the uncinate process of the pancreas extends and fuses to the dorsal surface of the body of the pancreas by surrounding the portal vein. It is asymptomatic, but it can be mistaken for a pancreatic head mass on imaging and could also have serious consequences during pancreatic surgery, if unrecognized. We report this case of a 53-year-old female patient who was diagnosed to have portal annular pancreas on the basis of an unusual course (ring appearance) of the main pancreatic duct on magnetic resonance cholangiopancreatography, not described earlier in the radiology literature. PMID:26649117

  3. Radiation dosimetry of the fibrin-binding probe 64Cu-FBP8 and its feasibility for positron emission tomography imaging of deep vein thrombosis and pulmonary embolism in rats

    PubMed Central

    Blasi, Francesco; Oliveira, Bruno L; Rietz, Tyson A; Rotile, Nicholas J; Day, Helen; Naha, Pratap C; Cormode, David P; Izquierdo-Garcia, David; Catana, Ciprian; Caravan, Peter

    2016-01-01

    The diagnosis of deep venous thromboembolic disease is still challenging despite the progress of current thrombus imaging modalities and new diagnostic algorithms. We recently reported the high target uptake and thrombus imaging efficacy of the novel fibrin-specific positron emission tomography probe 64Cu-FBP8. Here, we tested the feasibility of 64Cu-FBP8-PET to detect source thrombi and culprit emboli after deep vein thrombosis and pulmonary embolism (DVT-PE). To support clinical translation of 64Cu-FBP8, we performed a human dosimetry estimation using time-dependent biodistribution in rats. Methods Sprague-Dawley rats (n=7) underwent ferric chloride application on the femoral vein to trigger thrombosis. Pulmonary embolism was induced 30 min or 2 days after deep vein thrombosis by intrajugular injection of a preformed blood clot labeled with 125I-Fibrinogen. PET imaging was performed to detect the clots, and single-photon emission tomography (SPECT) was used to confirm in vivo the location of the pulmonary emboli. Ex vivo gamma-counting and histopathology were used to validate the imaging findings. Detailed biodistribution was performed in healthy rats (n=30) at different time-points after 64Cu-FBP8 administration to estimate human radiation dosimetry. Longitudinal whole-body PET/MR imaging (n=2) was performed after 64Cu-FBP8 administration to further assess radioactivity clearance. Results 64Cu-FBP8-PET imaging detected the location of lung emboli and venous thrombi after DVT-PE, revealing significant differences in uptake between target and background tissues (P<0.001). In vivo SPECT imaging and ex vivo gamma-counting confirmed the location of the lung emboli. PET quantification of the venous thrombi revealed that probe uptake was greater in younger clots than in older ones, a result confirmed by ex vivo analyses (P<0.001). Histopathology revealed an age-dependent reduction of thrombus fibrin content (P=0.006), further supporting the imaging findings

  4. Kidney dosimetry in ¹⁷⁷Lu and ⁹⁰Y peptide receptor radionuclide therapy: influence of image timing, time-activity integration method, and risk factors.

    PubMed

    Guerriero, F; Ferrari, M E; Botta, F; Fioroni, F; Grassi, E; Versari, A; Sarnelli, A; Pacilio, M; Amato, E; Strigari, L; Bodei, L; Paganelli, G; Iori, M; Pedroli, G; Cremonesi, M

    2013-01-01

    Kidney dosimetry in (177)Lu and (90)Y PRRT requires 3 to 6 whole-body/SPECT scans to extrapolate the peptide kinetics, and it is considered time and resource consuming. We investigated the most adequate timing for imaging and time-activity interpolating curve, as well as the performance of a simplified dosimetry, by means of just 1-2 scans. Finally the influence of risk factors and of the peptide (DOTATOC versus DOTATATE) is considered. 28 patients treated at first cycle with (177)Lu DOTATATE and 30 with (177)Lu DOTATOC underwent SPECT scans at 2 and 6 hours, 1, 2, and 3 days after the radiopharmaceutical injection. Dose was calculated with our simplified method, as well as the ones most used in the clinic, that is, trapezoids, monoexponential, and biexponential functions. The same was done skipping the 6 h and the 3 d points. We found that data should be collected until 100 h for (177)Lu therapy and 70 h for (90)Y therapy, otherwise the dose calculation is strongly influenced by the curve interpolating the data and should be carefully chosen. Risk factors (hypertension, diabetes) cause a rather statistically significant 20% increase in dose (t-test, P < 0.10), with DOTATATE affecting an increase of 25% compared to DOTATOC (t-test, P < 0.05).

  5. Optically stimulated luminescence dosimetry

    NASA Astrophysics Data System (ADS)

    McKeever, Stephen W.

    1999-02-01

    Optically Stimulated Luminescence (OSL) dosimetry is attractive to the health physics and dosimetry community due to its all-optical character, fast data acquisition and the avoidance of heating the detector. Until recently there was no luminescent material sensitive enough to radiation, and at the same time suitable for stimulation with visible light, for use in this application. However, anion-deficient aluminum oxide doped with carbon (Al2O3:C) appears to be not only an extremely sensitive thermoluminescence (TL) material, but is also well-suited to OSL applications. Several OSL readout protocols have been suggested, including cw-OSL, pulsed OSL (POSL), and 'delayed' OSL (DOSL). The paper discusses the physical mechanisms that give rise to the OSL signals and the dependence of these signals upon absorbed dose. Example applications of the use of OSL from Al2O3:C in environmental radiation and ultraviolet-B dosimetry are discussed.

  6. Direct dose to water dosimetry for pretreatment IMRT verification using a modified EPID

    SciTech Connect

    Gustafsson, Helen; Vial, Philip; Kuncic, Zdenka; Baldock, Clive; Denham, James W.; Greer, Peter B.

    2011-11-15

    Purpose: Electronic portal imaging devices (EPIDs) are high resolution systems that produce electronic dose maps with minimal time required for equipment setup, and therefore potentially present a time-saving alternative for intensity modulated radiation therapy (IMRT) pretreatment verification. A modified commercial EPID was investigated operated with an opaque sheet blocking the optical signal produced in the phosphor layer as a precursor to a switched mode dual dosimetry-imaging EPID system. The purpose of this study was to investigate the feasibility of using this system for direct dose to water dosimetry for pretreatment IMRT verification. Methods: A Varian amorphous silicon EPID was modified by placing an opaque sheet between the Gd{sub 2}S{sub 2}O:Tb phosphor layer and the photodiode array to block the optical photons. The EPID was thus converted to a direct-detecting system (dEPID), in which the high energy radiation deposits energy directly in the photodiode array. The copper build-up was replaced with d{sub max} solid water. Sixty-one IMRT beams of varying complexity were delivered to the EPID, to EDR2 dosimetric film and to a 2D ion chamber array (MapCheck). EPID data was compared to film and MapCheck data using gamma analysis with 3%, 3mm pass criteria. Results: The fraction of points that passed the gamma test was on average 98.1% and 98.6%, for the EPID versus film and EPID versus MapCheck comparisons, respectively. In the case of comparison with film, the majority of observed discrepancies were associated with problems related to film sensitivity or processing. Conclusions: The very close agreement between EPID and both film and MapCheck data demonstrates that the modified EPID is suitable for direct dose to water measurement for pretreatment IMRT verification. These results suggest a reconfigured EPID could be an efficient and accurate dosimeter. Alternatively, optical switching methods could be developed to produce a dual-mode EPID with both

  7. Dosimetry with diamond detectors

    NASA Astrophysics Data System (ADS)

    Gervino, G.; Marino, C.; Silvestri, F.; Lavagno, A.; Truc, F.

    2010-05-01

    In this paper we present the dosimetry analysis in terms of stability and repeatability of the signal and dose rate dependence of a synthetic single crystal diamond grown by Chemical Vapor Deposition (CVD) technique. The measurements carried out by 5 MeV X-ray photons beam show very promising results, even if the dose rate detector response points out that the charge trapping centers distribution is not uniform inside the crystal volume. This handicap that affects the detectors performances, must be ascribed to the growing process. Synthetic single crystal diamonds could be a valuable alternative to air ionization chambers for quality beam control and for intensity modulated radiation therapy beams dosimetry.

  8. Portal systemic encephalopathy.

    PubMed

    Schenker, S; Bay, M K

    1997-05-01

    The goal of this article is to update the status of Portal systemic encephalopathy (PSE) in the light of new data. First, PSE is the context of other types of hepatic encephalopathy. Subsequently, current views of the pathogenesis of the disorder are discussed, followed by an analysis of therapeutic options. Diagnosis will not be considered, as no major new developments have recently been documented in this area.

  9. Portal Annular Pancreas

    PubMed Central

    Harnoss, Jonathan M.; Harnoss, Julian C.; Diener, Markus K.; Contin, Pietro; Ulrich, Alexis B.; Büchler, Markus W.; Schmitz-Winnenthal, Friedrich H.

    2014-01-01

    Abstract Portal annular pancreas (PAP) is an asymptomatic congenital pancreas anomaly, in which portal and/or mesenteric veins are encased by pancreas tissue. The aim of the study was to determine the role of PAP in pancreatic surgery as well as its management and potential complication, specifically, postoperative pancreatic fistula (POPF). On the basis of a case report, the MEDLINE and ISI Web of Science databases were systematically reviewed up to September 2012. All articles describing a case of PAP were considered. In summary, 21 studies with 59 cases were included. The overall prevalence of PAP was 2.4% and the patients' mean (SD) age was 55.9 (16.2) years. The POPF rate in patients with PAP (12 pancreaticoduodenectomies and 3 distal pancreatectomies) was 46.7% (in accordance with the definition of the International Study Group of Pancreatic Surgery). Portal annular pancreas is a quite unattended pancreatic variant with high prevalence and therefore still remains a clinical challenge to avoid postoperative complications. To decrease the risk for POPF, attentive preoperative diagnostics should also focus on PAP. In pancreaticoduodenectomy, a shift of the resection plane to the pancreas tail should be considered; in extensive pancreatectomy, coverage of the pancreatic remnant by the falciform ligament could be a treatment option. PMID:25207658

  10. Ion-kill dosimetry

    NASA Technical Reports Server (NTRS)

    Katz, R.; Cucinotta, F. A.; Fromm, M.; Chambaudet, A.

    2001-01-01

    Unanticipated late effects in neutron and heavy ion therapy, not attributable to overdose, imply a qualitative difference between low and high LET therapy. We identify that difference as 'ion kill', associated with the spectrum of z/beta in the radiation field, whose measurement we label 'ion-kill dosimetry'.

  11. Audits for advanced treatment dosimetry

    NASA Astrophysics Data System (ADS)

    Ibbott, G. S.; Thwaites, D. I.

    2015-01-01

    Radiation therapy has advanced rapidly over the last few decades, progressing from 3D conformal treatment to image-guided intensity modulated therapy of several different flavors, both 3D and 4D and to adaptive radiotherapy. The use of intensity modulation has increased the complexity of quality assurance and essentially eliminated the physicist's ability to judge the validity of a treatment plan, even approximately, on the basis of appearance and experience. Instead, complex QA devices and procedures are required at the institutional level. Similarly, the assessment of treatment quality through remote and on-site audits also requires greater sophistication. The introduction of 3D and 4D dosimetry into external audit systems must follow, to enable quality assurance systems to perform meaningful and thorough audits.

  12. Automated synthesis and dosimetry of 6-deoxy-6-[18F]fluoro-D-fructose (6-[18F]FDF): a radiotracer for imaging of GLUT5 in breast cancer

    PubMed Central

    Bouvet, Vincent; Jans, Hans S; Wuest, Melinda; Soueidan, Olivier-Mohamad; Mercer, John; McEwan, Alexander JB; West, Frederick G; Cheeseman, Chris I; Wuest, Frank

    2014-01-01

    6-Deoxy-6-[18F]fluoro-D-fructose (6-[18F]FDF) is a promising PET radiotracer for imaging GLUT5 in breast cancer. The present work describes GMP synthesis of 6-[18F]FDF in an automated synthesis unit (ASU) and dosimetry calculations to determine radiation doses in humans. GMP synthesis and dosimetry calculations are important prerequisites for first-in-human clinical studies of 6-[18F]FDF. The radiochemical synthesis of 6-[18F]FDF was optimized and adapted to an automated synthesis process using a Tracerlab FXFN ASU (GE Healthcare). Starting from 30 GBq of cyclotron-produced n.c.a. [18F]fluoride, 2.9 ± 0.1 GBq of 6-[18F]FDF could be prepared within 50 min including HPLC purification resulting in an overall decay-corrected radiochemical yield of 14 ± 3% (n = 11). Radiochemical purity exceeded 95%, and the specific activity was greater than 5.1 GBq/μmol. Sprague-Dawley rats were used for biodistribution experiments, and dynamic and static small animal PET experiments. Biodistribution studies served as basis for allometric extrapolation to the standard man anatomic model and normal organ-absorbed dose calculations using OLINDA/EXM software. The calculated human effective dose for 6-[18F]FDF was 0.0089 mSv/MBq. Highest organ doses with a dose equivalent of 0.0315 mSv/MBq in a humans were found in bone. Injection of 370 MBq (10 mCi) of 6-[18F]FDF results in an effective whole body radiation dose of 3.3 mSv in humans, a value comparable to that of other 18F-labeled PET radiopharmaceuticals. The optimized automated synthesis under GMP conditions, the good radiochemical yield and the favorable human radiation dosimetry estimates support application of 6-[18F]FDF in clinical trials for molecular imaging of GLUT5 in breast cancer patients. PMID:24795839

  13. COMPUTED TOMOGRAPHIC AND ULTRASONOGRAPHIC CHARACTERISTICS OF CAVERNOUS TRANSFORMATION OF THE OBSTRUCTED PORTAL VEIN IN SMALL ANIMALS.

    PubMed

    Specchi, Swan; Pey, Pascaline; Ledda, Gianluca; Lustgarten, Meghann; Thrall, Donald; Bertolini, Giovanna

    2015-01-01

    In humans, the process of development of collateral vessels with hepatopetal flow around the portal vein in order to bypass an obstruction is called "cavernous transformation of the portal vein." The purpose of this retrospective, cross-sectional, multicentric study was to describe presumed cavernous transformation of the portal vein in small animals with portal vein obstruction using ultrasound and multidetector-row computed tomography (MDCT). Databases from three different institutions were searched for patients with an imaging diagnosis of cavernous transformation of the portal vein secondary to portal vein obstruction of any cause. Images were retrieved and reanalyzed. With MDCT-angiography, two main portoportal collateral pathways were identified: short tortuous portoportal veins around/inside the thrombus and long portoportal collaterals bypassing the site of portal obstruction. Three subtypes of the long collaterals, often coexisting, were identified. Branches of the hepatic artery where involved in collateral circulation in nine cases. Concomitant acquired portosystemic shunts were identified in six patients. With ultrasound, cavernous transformation of the portal vein was suspected in three dogs and one cat based on visualization of multiple and tortuous vascular structures corresponding to periportal collaterals. In conclusion, the current study provided descriptive MDCT and ultrasonographic characteristics of presumed cavernous transformation of the portal vein in a sample of small animals. Cavernous transformation of the portal vein could occur as a single condition or could be concurrent with acquired portosystemic shunts.

  14. COMPUTED TOMOGRAPHIC AND ULTRASONOGRAPHIC CHARACTERISTICS OF CAVERNOUS TRANSFORMATION OF THE OBSTRUCTED PORTAL VEIN IN SMALL ANIMALS.

    PubMed

    Specchi, Swan; Pey, Pascaline; Ledda, Gianluca; Lustgarten, Meghann; Thrall, Donald; Bertolini, Giovanna

    2015-01-01

    In humans, the process of development of collateral vessels with hepatopetal flow around the portal vein in order to bypass an obstruction is called "cavernous transformation of the portal vein." The purpose of this retrospective, cross-sectional, multicentric study was to describe presumed cavernous transformation of the portal vein in small animals with portal vein obstruction using ultrasound and multidetector-row computed tomography (MDCT). Databases from three different institutions were searched for patients with an imaging diagnosis of cavernous transformation of the portal vein secondary to portal vein obstruction of any cause. Images were retrieved and reanalyzed. With MDCT-angiography, two main portoportal collateral pathways were identified: short tortuous portoportal veins around/inside the thrombus and long portoportal collaterals bypassing the site of portal obstruction. Three subtypes of the long collaterals, often coexisting, were identified. Branches of the hepatic artery where involved in collateral circulation in nine cases. Concomitant acquired portosystemic shunts were identified in six patients. With ultrasound, cavernous transformation of the portal vein was suspected in three dogs and one cat based on visualization of multiple and tortuous vascular structures corresponding to periportal collaterals. In conclusion, the current study provided descriptive MDCT and ultrasonographic characteristics of presumed cavernous transformation of the portal vein in a sample of small animals. Cavernous transformation of the portal vein could occur as a single condition or could be concurrent with acquired portosystemic shunts. PMID:25877678

  15. Direct-detection EPID dosimetry: investigation of a potential clinical configuration for IMRT verification

    NASA Astrophysics Data System (ADS)

    Vial, Philip; Gustafsson, Helen; Oliver, Lyn; Baldock, Clive; Greer, Peter B.

    2009-12-01

    The routine use of electronic portal imaging devices (EPIDs) as dosimeters for radiotherapy quality assurance is complicated by the non-water equivalence of the EPID's dose response. A commercial EPID modified to a direct-detection configuration was previously demonstrated to provide water-equivalent dose response with dmax solid water build-up and 10 cm solid water backscatter. Clinical implementation of the direct EPID (dEPID) requires a design that maintains the water-equivalent dose response, can be incorporated onto existing EPID support arms and maintains sufficient image quality for clinical imaging. This study investigated the dEPID dose response with different configurations of build-up and backscatter using varying thickness of solid water and copper. Field size output factors and beam profiles measured with the dEPID were compared with ionization chamber measurements of dose in water for both 6 MV and 18 MV. The dEPID configured with dmax solid water build-up and no backscatter (except for the support arm) was within 1.5% of dose in water data for both energies. The dEPID was maintained in this configuration for clinical dosimetry and image quality studies. Close agreement between the dEPID and treatment planning system was obtained for an IMRT field with 98.4% of pixels within the field meeting a gamma criterion of 3% and 3 mm. The reduced sensitivity of the dEPID resulted in a poorer image quality based on quantitative (contrast-to-noise ratio) and qualitative (anthropomorphic phantom) studies. However, clinically useful images were obtained with the dEPID using typical treatment field doses. The dEPID is a water-equivalent dosimeter that can be implemented with minimal modifications to the standard commercial EPID design. The proposed dEPID design greatly simplifies the verification of IMRT dose delivery.

  16. Direct-detection EPID dosimetry: investigation of a potential clinical configuration for IMRT verification.

    PubMed

    Vial, Philip; Gustafsson, Helen; Oliver, Lyn; Baldock, Clive; Greer, Peter B

    2009-12-01

    The routine use of electronic portal imaging devices (EPIDs) as dosimeters for radiotherapy quality assurance is complicated by the non-water equivalence of the EPID's dose response. A commercial EPID modified to a direct-detection configuration was previously demonstrated to provide water-equivalent dose response with d(max) solid water build-up and 10 cm solid water backscatter. Clinical implementation of the direct EPID (dEPID) requires a design that maintains the water-equivalent dose response, can be incorporated onto existing EPID support arms and maintains sufficient image quality for clinical imaging. This study investigated the dEPID dose response with different configurations of build-up and backscatter using varying thickness of solid water and copper. Field size output factors and beam profiles measured with the dEPID were compared with ionization chamber measurements of dose in water for both 6 MV and 18 MV. The dEPID configured with d(max) solid water build-up and no backscatter (except for the support arm) was within 1.5% of dose in water data for both energies. The dEPID was maintained in this configuration for clinical dosimetry and image quality studies. Close agreement between the dEPID and treatment planning system was obtained for an IMRT field with 98.4% of pixels within the field meeting a gamma criterion of 3% and 3 mm. The reduced sensitivity of the dEPID resulted in a poorer image quality based on quantitative (contrast-to-noise ratio) and qualitative (anthropomorphic phantom) studies. However, clinically useful images were obtained with the dEPID using typical treatment field doses. The dEPID is a water-equivalent dosimeter that can be implemented with minimal modifications to the standard commercial EPID design. The proposed dEPID design greatly simplifies the verification of IMRT dose delivery. PMID:19904032

  17. Dosimetry in radiotherapy using a-Si EPIDs: Systems, methods, and applications focusing on 3D patient dose estimation

    NASA Astrophysics Data System (ADS)

    McCurdy, B. M. C.

    2013-06-01

    An overview is provided of the use of amorphous silicon electronic portal imaging devices (EPIDs) for dosimetric purposes in radiation therapy, focusing on 3D patient dose estimation. EPIDs were originally developed to provide on-treatment radiological imaging to assist with patient setup, but there has also been a natural interest in using them as dosimeters since they use the megavoltage therapy beam to form images. The current generation of clinically available EPID technology, amorphous-silicon (a-Si) flat panel imagers, possess many characteristics that make them much better suited to dosimetric applications than earlier EPID technologies. Features such as linearity with dose/dose rate, high spatial resolution, realtime capability, minimal optical glare, and digital operation combine with the convenience of a compact, retractable detector system directly mounted on the linear accelerator to provide a system that is well-suited to dosimetric applications. This review will discuss clinically available a-Si EPID systems, highlighting dosimetric characteristics and remaining limitations. Methods for using EPIDs in dosimetry applications will be discussed. Dosimetric applications using a-Si EPIDs to estimate three-dimensional dose in the patient during treatment will be overviewed. Clinics throughout the world are implementing increasingly complex treatments such as dynamic intensity modulated radiation therapy and volumetric modulated arc therapy, as well as specialized treatment techniques using large doses per fraction and short treatment courses (ie. hypofractionation and stereotactic radiosurgery). These factors drive the continued strong interest in using EPIDs as dosimeters for patient treatment verification.

  18. Collateral Pathways in Portal Hypertension

    PubMed Central

    Sharma, Malay; Rameshbabu, Chittapuram S.

    2012-01-01

    Presence of portosystemic collateral veins (PSCV) is common in portal hypertension due to cirrhosis. Physiologically, normal portosystemic anastomoses exist which exhibit hepatofugal flow. With the development of portal hypertension, transmission of backpressure leads to increased flow in these patent normal portosystemic anastomoses. In extrahepatic portal vein obstruction collateral circulation develops in a hepatopetal direction and portoportal pathways are frequently found. The objective of this review is to illustrate the various PSCV and portoportal collateral vein pathways pertinent to portal hypertension in liver cirrhosis and EHPVO. PMID:25755456

  19. Animal models of portal hypertension

    PubMed Central

    Abraldes, Juan G; Pasarín, Marcos; García-Pagán, Juan Carlos

    2006-01-01

    Animal models have allowed detailed study of hemodynamic alterations typical of portal hypertension and the molecular mechanisms involved in abnormalities in splanchnic and systemic circulation associated with this syndrome. Models of prehepatic portal hypertension can be used to study alterations in the splanchnic circulation and the pathophysiology of the hyperdynamic circulation. Models of cirrhosis allow study of the alterations in intrahepatic microcirculation that lead to increased resistance to portal flow. This review summarizes the currently available literature on animal models of portal hypertension and analyzes their relative utility. The criteria for choosing a particular model, depending on the specific objectives of the study, are also discussed. PMID:17075968

  20. Patient dosimetry in nuclear medicine.

    PubMed

    Mattsson, Sören

    2015-07-01

    In diagnostic nuclear medicine, the biokinetics of the radiopharmaceutical (actually of the radionuclide) is determined for a number of representative patients. At therapy, it is essential to determine the patient's individual biokinetics of the radiopharmaceutical in order to calculate the absorbed doses to critical normal organs/tissues and to the target volume(s) with high accuracy. For the diagnostic situations, there is still a lack of quantitative determinations of the organ/tissue contents of radiopharmaceuticals and their variation with time. Planar gamma camera imaging using the conjugate view technique combined with a limited number of SPECT/CT images is the main method for such studies. In a similar way, PET/CT is used for 3D image-based internal dosimetry for PET substances. The transition from stylised reference phantoms to voxel phantoms will lead to improved dose estimates for diagnostic procedures. Examples of dose coefficients and effective doses for diagnostic substances are given. For the therapeutic situation, a pre-therapeutic low activity administration is used for quantitative measurements of organ/tissue distribution data by a gamma camera or a SPECT- or PET-unit. Together with CT and/or MR images this will be the base for individual dose calculations using Monte Carlo technique. Treatments based on administered activity should only be used if biological variations between patients are small or if a pre-therapeutic activity administration is impossible.

  1. Massive superior mesenteric venous aneurysm with portal venous thrombosis.

    PubMed

    Starikov, Anna; Bartolotta, Roger J

    2015-01-01

    Portal venous aneurysm is a rare and sometimes dangerous vascular pathology, which can result in thrombosis or rupture. We present the computed tomography, magnetic resonance, and sonographic imaging of a 27-year-old man with superior mesenteric venous aneurysm and subsequent thrombosis following acute pancreatitis. This multimodality imaging approach can prove useful in the evaluation of these rare aneurysms.

  2. TU-C-BRE-11: 3D EPID-Based in Vivo Dosimetry: A Major Step Forward Towards Optimal Quality and Safety in Radiation Oncology Practice

    SciTech Connect

    Mijnheer, B; Mans, A; Olaciregui-Ruiz, I; Rozendaal, R; Spreeuw, H; Herk, M van

    2014-06-15

    Purpose: To develop a 3D in vivo dosimetry method that is able to substitute pre-treatment verification in an efficient way, and to terminate treatment delivery if the online measured 3D dose distribution deviates too much from the predicted dose distribution. Methods: A back-projection algorithm has been further developed and implemented to enable automatic 3D in vivo dose verification of IMRT/VMAT treatments using a-Si EPIDs. New software tools were clinically introduced to allow automated image acquisition, to periodically inspect the record-and-verify database, and to automatically run the EPID dosimetry software. The comparison of the EPID-reconstructed and planned dose distribution is done offline to raise automatically alerts and to schedule actions when deviations are detected. Furthermore, a software package for online dose reconstruction was also developed. The RMS of the difference between the cumulative planned and reconstructed 3D dose distributions was used for triggering a halt of a linac. Results: The implementation of fully automated 3D EPID-based in vivo dosimetry was able to replace pre-treatment verification for more than 90% of the patient treatments. The process has been fully automated and integrated in our clinical workflow where over 3,500 IMRT/VMAT treatments are verified each year. By optimizing the dose reconstruction algorithm and the I/O performance, the delivered 3D dose distribution is verified in less than 200 ms per portal image, which includes the comparison between the reconstructed and planned dose distribution. In this way it was possible to generate a trigger that can stop the irradiation at less than 20 cGy after introducing large delivery errors. Conclusion: The automatic offline solution facilitated the large scale clinical implementation of 3D EPID-based in vivo dose verification of IMRT/VMAT treatments; the online approach has been successfully tested for various severe delivery errors.

  3. Comparison of Real-Time Intraoperative Ultrasound-Based Dosimetry With Postoperative Computed Tomography-Based Dosimetry for Prostate Brachytherapy

    SciTech Connect

    Nag, Subir; Shi Peipei; Liu Bingren; Gupta, Nilendu; Bahnson, Robert R.; Wang, Jian Z.

    2008-01-01

    Purpose: To evaluate whether real-time intraoperative ultrasound (US)-based dosimetry can replace conventional postoperative computed tomography (CT)-based dosimetry in prostate brachytherapy. Methods and Materials: Between December 2001 and November 2002, 82 patients underwent {sup 103}Pd prostate brachytherapy. An interplant treatment planning system was used for real-time intraoperative transrectal US-guided treatment planning. The dose distribution was updated according to the estimated seed position to obtain the dose-volume histograms. Postoperative CT-based dosimetry was performed a few hours later using the Theraplan-Plus treatment planning system. The dosimetric parameters obtained from the two imaging modalities were compared. Results: The results of this study revealed correlations between the US- and CT-based dosimetry. However, large variations were found in the implant-quality parameters of the two modalities, including the doses covering 100%, 90%, and 80% of the prostate volume and prostate volumes covered by 100%, 150%, and 200% of the prescription dose. The mean relative difference was 38% and 16% for doses covering 100% and 90% of the prostate volume and 10% and 21% for prostate volumes covered by 100% and 150% of the prescription dose, respectively. The CT-based volume covered by 200% of the prescription dose was about 30% greater than the US-based one. Compared with CT-based dosimetry, US-based dosimetry significantly underestimated the dose to normal organs, especially for the rectum. The average US-based maximal dose and volume covered by 100% of the prescription dose for the rectum was 72 Gy and 0.01 cm{sup 3}, respectively, much lower than the 159 Gy and 0.65 cm{sup 3} obtained using CT-based dosimetry. Conclusion: Although dosimetry using intraoperative US-based planning provides preliminary real-time information, it does not accurately reflect the postoperative CT-based dosimetry. Until studies have determined whether US-based dosimetry

  4. In vivo dosimetry for IMRT

    SciTech Connect

    Vial, Philip

    2011-05-05

    In vivo dosimetry has a well established role in the quality assurance of 2D radiotherapy and 3D conformal radiotherapy. The role of in vivo dosimetry for IMRT is not as well established. IMRT introduces a range of technical issues that complicate in vivo dosimetry. The first decade or so of IMRT implementation has largely relied upon pre-treatment phantom based dose verification. During that time, several new devices and techniques for in vivo dosimetry have emerged with the promise of providing the ultimate form of IMRT dose verification. Solid state dosimeters continue to dominate the field of in vivo dosimetry in the IMRT era. In this report we review the literature on in vivo dosimetry for IMRT, with an emphasis on clinical evidence for different detector types. We describe the pros and cons of different detectors and techniques in the IMRT setting and the roles that they are likely to play in the future.

  5. In vivo dosimetry for IMRT

    NASA Astrophysics Data System (ADS)

    Vial, Philip

    2011-05-01

    In vivo dosimetry has a well established role in the quality assurance of 2D radiotherapy and 3D conformal radiotherapy. The role of in vivo dosimetry for IMRT is not as well established. IMRT introduces a range of technical issues that complicate in vivo dosimetry. The first decade or so of IMRT implementation has largely relied upon pre-treatment phantom based dose verification. During that time, several new devices and techniques for in vivo dosimetry have emerged with the promise of providing the ultimate form of IMRT dose verification. Solid state dosimeters continue to dominate the field of in vivo dosimetry in the IMRT era. In this report we review the literature on in vivo dosimetry for IMRT, with an emphasis on clinical evidence for different detector types. We describe the pros and cons of different detectors and techniques in the IMRT setting and the roles that they are likely to play in the future.

  6. Portal hypertension due to portal venous thrombosis: Etiology, clinical outcomes

    PubMed Central

    Harmanci, Ozgur; Bayraktar, Yusuf

    2007-01-01

    The thrombophilia in adult life has major implications in the hepatic vessels. The resulting portal vein thrombosis has various outcomes and complications. Esophageal varices, portal gastropathy, ascites, severe hypersplenism and liver failure needing liver transplantation are known well. The newly formed collateral venous circulation showing itself as pseudocholangicarcinoma sign and its possible clinical reflection as cholestasis are also known from a long time. The management strategies for these complications of portal vein thrombosis are not different from their counterpart which is cirrhotic portal hypertension, but the prognosis is unquestionably better in former cases. In this review we present and discuss the portal vein thrombosis, etiology and the resulting clinical pictures. There are controversial issues in nomenclature, management (including anticoagulation problems), follow up strategies and liver transplantation. In the light of the current knowledge, we discuss some controversial issues in literature and present our experience and our proposals about this group of patients. PMID:17552000

  7. Electron Paramagnetic Resonance Retrospective Dosimetry

    SciTech Connect

    Romanyukha, Alex; Trompier, Francois

    2011-05-05

    Necessity for, principles of, and general concepts of the electron paramagnetic resonance (EPR) retrospective dosimetry are presented. Also presented and given in details are examples of EPR retrospective dosimetry applications in tooth enamel, bone, and fingernails with focus on general approaches for solving technical and methodological problems. Advantages, drawbacks, and possible future developments are discussed and an extensive bibliography on EPR retrospective dosimetry is provided.

  8. Neutron beam measurement dosimetry

    SciTech Connect

    Amaro, C.R.

    1995-11-01

    This report describes animal dosimetry studies and phantom measurements. During 1994, 12 dogs were irradiated at BMRR as part of a 4 fraction dose tolerance study. The animals were first infused with BSH and irradiated daily for 4 consecutive days. BNL irradiated 2 beagles as part of their dose tolerance study using BPA fructose. In addition, a dog at WSU was irradiated at BMRR after an infusion of BPA fructose. During 1994, the INEL BNCT dosimetry team measured neutron flux and gamma dose profiles in two phantoms exposed to the epithermal neutron beam at the BMRR. These measurements were performed as a preparatory step to the commencement of human clinical trials in progress at the BMRR.

  9. All Roads Lead to Portal

    ERIC Educational Resources Information Center

    Heid, Susan D.

    2007-01-01

    Portals are taking off on campuses nationwide. According to "Campus Computing 2006," the Campus Computing Project's survey of 540 two- and four-year public and private colleges and universities across the US, portal deployment for four-year public residential universities jumped from 28 to 74 percent of responding institutions between the…

  10. NSTA Portal to Science Safety

    ERIC Educational Resources Information Center

    Roy, Ken

    2010-01-01

    The National Science Teachers Association's (NSTA) Science Safety Advisory Board recently launched the Safety in the Science Classroom portal. This portal serves as a gateway to safety resources for teachers, supervisors, and administrators. It also contains an evolving list of safety resources for elementary, middle, and high schools. The list…

  11. [Innovation in gynaecological brachytherapy: new technologies, pulse dose-rate brachytherapy, image, definition of new volumes of interest and their impact on dosimetry: application in a clinical research programme "STIC"].

    PubMed

    Haie-Meder, C; Peiffert, D

    2006-11-01

    Brachytherapy plays a fundamental role in the therapeutic approach of patients with stage I-IV cervical carcinoma. Technical modalities have evolved during the last decades: stepping source technology, imaging modalities development, specially IMN, treatment planning system integrating 3D images. Images from CT-Scan and MRI have contributed to a better knowledge of tumoral extension and critical organs. CT and/or MRI compatible applicators allow a sectional image based approach with a better definition of tumour volume compared to traditional approaches. The introduction of 3D image based approach for GTV and CTV requires new definitions and a common language. In 2000, a working group within GEC-ESTRO was created to support 3D image based 3D treatment planning approach in cervix cancer BT. The task was to determine a common terminology enabling various groups to use a common language. Recommendations were described and proposed based on clinical experience and dosimetric concepts of different institutions. Two CTVs were described en relation to the risk for recurrence: high-risk CTV and intermediate risk CTV. In order to better define the role of such definitions and their potential impact on the complication incidence in patients with cervical cancer, a special French programme was developed. The aim of this programme is to study the incidence of the severe 2-year complication rate in two comparable patient populations: one population is treated using PDR brachytherapy with CT-Scan or MRI with the applicators in place allowing a 3D dosimetry with optimization, the second population is treated using standard X-rays radiographs without any delineation of the target nor optimisation. Each population arm includes 425 patients. A medicoeconomic assessment is performed, allowing a real cost of the most sophisticated approach compared to a historical dosimetric system.

  12. The Portuguese Climate Portal

    NASA Astrophysics Data System (ADS)

    Gomes, Sandra; Deus, Ricardo; Nogueira, Miguel; Viterbo, Pedro; Miranda, Miguel; Antunes, Sílvia; Silva, Alvaro; Miranda, Pedro

    2016-04-01

    The Portuguese Local Warming Website (http://portaldoclima.pt) has been developed in order to support the society in Portugal in preparing for the adaptation to the ongoing and future effects of climate change. The climate portal provides systematic and easy access to authoritative scientific data ready to be used by a vast and diverse user community from different public and private sectors, key players and decision makers, but also to high school students, contributing to the increase in knowledge and awareness on climate change topics. A comprehensive set of regional climate variables and indicators are computed, explained and graphically presented. Variables and indicators were built in agreement with identified needs after consultation of the relevant social partners from different sectors, including agriculture, water resources, health, environment and energy and also in direct cooperation with the Portuguese National Strategy for Climate Change Adaptation (ENAAC) group. The visual interface allows the user to dynamically interact, explore, quickly analyze and compare, but also to download and import the data and graphics. The climate variables and indicators are computed from state-of-the-art regional climate model (RCM) simulations (e.g., CORDEX project), at high space-temporal detail, allowing to push the limits of the projections down to local administrative regions (NUTS3) and monthly or seasonal periods, promoting local adaptation strategies. The portal provides both historical data (observed and modelled for the 1971-2000 period) and future climate projections for different scenarios (modelled for the 2011-2100 period). A large effort was undertaken in order to quantify the impacts of the risk of extreme events, such as heavy rain and flooding, droughts, heat and cold waves, and fires. Furthermore the different climate scenarios and the ensemble of RCM models, with high temporal (daily) and spatial (~11km) detail, is taken advantage in order to

  13. The International Reactor Dosimetry File.

    1994-01-19

    Version 01 The International Reactor Dosimetry File (IRDF-90) contains recommended neutron cross-section data to be used for reactor neutron dosimetry by foil activation. It also contains selected recommended values for radiation damage cross-sections and benchmark neutron spectra. This library supersedes all earlier versions of IRDF.

  14. The highly accurate anteriolateral portal for injecting the knee

    PubMed Central

    2011-01-01

    Background The extended knee lateral midpatellar portal for intraarticular injection of the knee is accurate but is not practical for all patients. We hypothesized that a modified anteriolateral portal where the synovial membrane of the medial femoral condyle is the target would be highly accurate and effective for intraarticular injection of the knee. Methods 83 subjects with non-effusive osteoarthritis of the knee were randomized to intraarticular injection using the modified anteriolateral bent knee versus the standard lateral midpatellar portal. After hydrodissection of the synovial membrane with lidocaine using a mechanical syringe (reciprocating procedure device), 80 mg of triamcinolone acetonide were injected into the knee with a 2.0-in (5.1-cm) 21-gauge needle. Baseline pain, procedural pain, and pain at outcome (2 weeks and 6 months) were determined with the 10 cm Visual Analogue Pain Score (VAS). The accuracy of needle placement was determined by sonographic imaging. Results The lateral midpatellar and anteriolateral portals resulted in equivalent clinical outcomes including procedural pain (VAS midpatellar: 4.6 ± 3.1 cm; anteriolateral: 4.8 ± 3.2 cm; p = 0.77), pain at outcome (VAS midpatellar: 2.6 ± 2.8 cm; anteriolateral: 1.7 ± 2.3 cm; p = 0.11), responders (midpatellar: 45%; anteriolateral: 56%; p = 0.33), duration of therapeutic effect (midpatellar: 3.9 ± 2.4 months; anteriolateral: 4.1 ± 2.2 months; p = 0.69), and time to next procedure (midpatellar: 7.3 ± 3.3 months; anteriolateral: 7.7 ± 3.7 months; p = 0.71). The anteriolateral portal was 97% accurate by real-time ultrasound imaging. Conclusion The modified anteriolateral bent knee portal is an effective, accurate, and equivalent alternative to the standard lateral midpatellar portal for intraarticular injection of the knee. Trial Registration ClinicalTrials.gov: NCT00651625 PMID:21447197

  15. Dose calibration optimization and error propagation in polymer gel dosimetry

    NASA Astrophysics Data System (ADS)

    Jirasek, A.; Hilts, M.

    2014-02-01

    This study reports on the relative precision, relative error, and dose differences observed when using a new full-image calibration technique in NIPAM-based x-ray CT polymer gel dosimetry. The effects of calibration parameters (e.g. gradient thresholding, dose bin size, calibration fit function, and spatial remeshing) on subsequent errors in calibrated gel images are reported. It is found that gradient thresholding, dose bin size, and fit function all play a primary role in affecting errors in calibrated images. Spatial remeshing induces minimal reductions or increases in errors in calibrated images. This study also reports on a full error propagation throughout the CT gel image pre-processing and calibration procedure thus giving, for the first time, a realistic view of the errors incurred in calibrated CT polymer gel dosimetry. While the work is based on CT polymer gel dosimetry, the formalism is valid for and easily extended to MRI or optical CT dosimetry protocols. Hence, the procedures developed within the work are generally applicable to calibration of polymer gel dosimeters.

  16. The parallel virtual file system for portals.

    SciTech Connect

    Schutt, James Alan

    2004-04-01

    This report presents the result of an effort to re-implement the Parallel Virtual File System (PVFS) using Portals as the transport. This report provides short overviews of PVFS and Portals, and describes the design and implementation of PVFS over Portals. Finally, the results of performance testing of both stock PVFS and PVFS over Portals are presented.

  17. Heavy-ion dosimetry

    SciTech Connect

    Schimmerling, W.

    1980-03-01

    This lecture deals with some of the more important physical characteristics of relativistic heavy ions and their measurement, with beam delivery and beam monitoring, and with conventional radiation dosimetry as used in the operation of the BEVALAC biomedical facility for high energy heavy ions (Lyman and Howard, 1977; BEVALAC, 1977). Even so, many fundamental aspects of the interaction of relativistic heavy ions with matter, including important atomic physics and radiation chemical considerations, are not discussed beyond the reminder that such additional understanding is required before an adequte perspective of the problem can be attained.

  18. Uranium Dispersion & Dosimetry Model.

    SciTech Connect

    MICHAEL,; MOMENI, H.

    2002-03-22

    The Uranium Dispersion and Dosimetry (UDAD) program provides estimates of potential radiation exposure to individuals and to the general population in the vicinity of a uranium processing facility such as a uranium mine or mill. Only transport through the air is considered. Exposure results from inhalation, external irradiation from airborne and ground-deposited activity, and ingestion of foodstuffs. Individual dose commitments, population dose commitments, and environmental dose commitments are computed. The program was developed for application to uranium mining and milling; however, it may be applied to dispersion of any other pollutant.

  19. Uranium Dispersion & Dosimetry Model.

    2002-03-22

    The Uranium Dispersion and Dosimetry (UDAD) program provides estimates of potential radiation exposure to individuals and to the general population in the vicinity of a uranium processing facility such as a uranium mine or mill. Only transport through the air is considered. Exposure results from inhalation, external irradiation from airborne and ground-deposited activity, and ingestion of foodstuffs. Individual dose commitments, population dose commitments, and environmental dose commitments are computed. The program was developed for applicationmore » to uranium mining and milling; however, it may be applied to dispersion of any other pollutant.« less

  20. Fast neutron dosimetry

    SciTech Connect

    DeLuca, P.M. Jr.; Pearson, D.W.

    1992-01-01

    This progress report concentrates on two major areas of dosimetry research: measurement of fast neutron kerma factors for several elements for monochromatic and white spectrum neutron fields and determination of the response of thermoluminescent phosphors to various ultra-soft X-ray energies and beta-rays. Dr. Zhixin Zhou from the Shanghai Institute of Radiation Medicine, People's Republic of China brought with him special expertise in the fabrication and use of ultra-thin TLD materials. Such materials are not available in the USA. The rather unique properties of these materials were investigated during this grant period.

  1. The NOAO NVO Portal: Overall Design & Implementation

    NASA Astrophysics Data System (ADS)

    Fuentes, E.; Miller, C. J.; Gasson, D.

    2007-10-01

    We present an overview and design of the NOAO National Virtual Observatory (NVO) Portal. This is a web application providing one-stop discovery, analysis, and access to VO-compliant imaging data and services. It strictly follows the Model-View-Controller (MVC) design pattern and relies heavily on Asynchronous Javascript And XML (AJAX) in the browser. Because of the heavy use of AJAX, the relatively simple database schemas, and, most importantly, the rapid development/iteration schedule, Ruby-on-Rails (RoR) was chosen as the implementation language and PostgreSQL as the database engine.

  2. Reduction of the effect of non-uniform backscatter from an E-type support arm of a Varian a-Si EPID used for dosimetry

    NASA Astrophysics Data System (ADS)

    Rowshanfarzad, Pejman; Sabet, Mahsheed; O'Connor, Daryl J.; Greer, Peter B.

    2010-11-01

    Backscatter from the metallic components in the support arm is one of the sources of inaccuracy in dosimetry with Varian amorphous silicon electronic portal imaging devices (a-Si EPIDs). In this study, the non-uniform arm backscatter is blocked by adding lead sheets between the EPID and an E-type support arm. By comparing the EPID responses on and off the arm, with and without lead and considering the extra weight on the imager, 2 mm of lead was determined as the optimum thickness for both 6 and 18 MV beam energies. The arm backscatter at the central axis with the 2 mm lead in place decreased to 0.1% and 0.2% for the largest field size of 30 × 30 cm2 using 6 and 18 MV beams, from 2.3% and 1.3% without lead. Changes in the source-to-detector distance (SDD) did not affect the backscatter component more than 1%. The symmetry of the in-plane profiles improved for all field sizes for both beam energies. The addition of lead decreased the contrast-to-noise ratio and resolution by 1.3% and 0.84% for images taken in 6 MV and by 0.5% and 0.38% for those in 18 MV beams. The displacement of the EPID central pixel was measured during a 360° gantry rotation with and without lead which was 1 pixel different. While the backscatter reduces with increasing lead thickness, a 2 mm lead sheet seems sufficient for acceptable dosimetry results without any major degradation to the routine performance of the imager. No increase in patient skin dose was detected.

  3. Hidden Magnetic Portals Around Earth

    NASA Video Gallery

    A NASA-sponsored researcher at the University of Iowa has developed a way for spacecraft to hunt down hidden magnetic portals in the vicinity of Earth. These gateways link the magnetic field of our...

  4. SU-E-T-291: Sensitivity of a Simple 2D EPID in Vivo Dosimetry

    SciTech Connect

    Peca, S; Brown, D

    2014-06-01

    Purpose: As radiotherapy (RT) increases in complexity, so does motivation for in vivo dosimetry (IVD), which may detect errors such as: setup, beam shaping and dose delivered. We have recently developed an easy-toimplement method for two-dimensional IVD based on images taken with the electronic portal imaging device (EPID) in cine mode during treatment. The purpose of this work is to characterize its sensitivity to possible RT delivery errors. Methods: We introduced a series of modifications to a simple RT field (10×10, 100MU, 300RR, 20cm homogeneous phantom) to simulate errors. These modifications included multi-leaf collimator (MLC) position, number of MUs, and collimator angle. We quantified the sensitivity to inhomogeneities by inserting variable amounts of solid lung and bone. Finally we delivered realistic fields to an anthropomorphic phantom to estimate sensitivity to gantry angle and setup errors. Results: Our EPIDIVD is sensitive to MLC positioning errors of 1mm and 3mm in the closed and open directions respectively, and to 3% MU variations. Sensitivity to collimator angle depends on field shape irregularity; in the case of a 10x10 field, we are sensitive to errors of 0.8°. The sensitivity to inhomogeneities is limited by the nature of MV imaging: approximately 1% signal change is noted when switching 5cm of water to equal amounts of bone or lung. This suggests that the EPID-IVD is likely not sensitive to small setup or gantry angle errors, as confirmed by anthropomorphic tests. Conclusion: We have characterized a simple method of 2D dose reconstruction at isocenter depth inside the patient, which is sensitive to possible RT delivery errors. This method may be useful as a secondary safety check, to prevent large errors from being carried on to following fractions, and to record delivered dose. By using readily available hardware, it is easily implemented and may prove especially useful in centers with limited resources.

  5. The SmartGeo Portal: A retrospective

    NASA Astrophysics Data System (ADS)

    Heilmann, Zeno; Satta, Guido; Bonomi, Ernesto

    2016-04-01

    The SmartGeo portal was created in a follow-up project that evolved from the geophysical data imaging services of a Grid computing portal for Geoscience, called GRIDA3. The scope of the project was to support commercial geotechnical service providers as well as academic researchers working in near-surface geoscience. Starting from the existing services, the SmartGeo portal was set up on new hardware, using the latest version of the grid portal environment EnginFrame. After a first working version was established, the services were reviewed, updated and accompanied by new services according to the feedback we received from our partners. One partner for instance experienced large difficulties in a project that aimed at delineating the aquifer for finding water pollutant substances in an industrial area of Basel. The seismic imaging service inherited from the previous portal was employing a data-driven algorithm optimized to provide, directly during data acquisition, nearly in real-time a first image of the subsurface structure. Different to this, our user needed for his data from a geologically very complex and noisy urban environment the maximum lateral resolution and noise reduction possible. For this purpose we added two cutting edge data imaging algorithms able to deliver such high precision results by simultaneously optimizing, for every single image point, all parameters of the mathematical model---a procedure which increased the computational effort by one or two magnitudes, respectively. Thus, parallel computing on grid infrastructure served for maximizing the image resolution instead for generating real-time results. This proved also very useful for the data of an academic partner, recorded for imaging the structure of a shallow sedimentary basin, where we could obtain strongly improved seismic velocity information using these new algorithms. A general user request was to implement interactive data visualization tools. To fulfill this demand we took

  6. Portal vein thrombosis treated using danaparoid sodium and antithrombin III.

    PubMed

    Uchiyama, T; Hirokazu, Takahashi; Hosono, K; Endo, H; Akiyama, T; Yoneda, K; Inamori, M; Abe, Y; Kubota, K; Saito, S; Nakajima, A

    2010-01-01

    A 45-year-old man under treatment for liver cirrhosis (LC) due to chronic hepatitis C and hemophilia A was seen in our emergency room because of a 10-kg weight gain in the previous week due to ascites. Portal vein thrombosis (PVT) was detected with computer tomography (CT) and ultrasonographic (US). Danaparoid sodium (DS) and antithrombin III (AT III) were administrated and doppler US images showed improvement of portal venous blood flow. DS or AT III may be safe and alternative therapies for PVT. PMID:20422871

  7. Evaluation of an a-Si EPID in direct detection configuration as a water-equivalent dosimeter for transit dosimetry

    SciTech Connect

    Sabet, Mahsheed; Menk, Frederick W.; Greer, Peter B.

    2010-04-15

    Purpose: A major problem associated with amorphous silicon (a-Si) electronic portal imaging devices (EPIDs) for transit dosimetry is the presence of a phosphor layer, which can introduce large deviations from water-equivalent behavior due to energy-dependent response and visible light scattering. In this study, an amorphous silicon EPID was modified to a direct detection configuration by removing the phosphor layer, and the accuracy of using it for transit dosimetry measurements was investigated for 6 and 18 MV treatment beams by comparison to ion-chamber in water measurements. Methods: Solid water and copper were both evaluated as buildup materials. Using the optimum buildup thickness in each case, effects of changes in radiation field size, source to detector distance, and patient/phantom thickness were investigated by comparison to reference measurements made by an ionization chamber on the central axis. The off-axis response of the imager was also investigated by comparison of EPID image profiles to dose profiles obtained by a scanning ionization chamber in a water tank with various thicknesses of slab phantoms, and an anthropomorphic phantom in the beam using Gamma evaluation (3%, 3 mm criteria). The imaging characteristics of the direct EPID were investigated by comparison to a commercial EPID using QC3V phantom, and by taking images of an anthropomorphic pelvic phantom containing fiducial gold markers. Results: Either 30 mm of solid water or 3.3 mm of copper were found to be the most suitable buildup thicknesses with solid water providing more accurate results. Using solid water buildup, the EPID response compared to the reference dosimeter within 2% for all conditions except phantom thicknesses larger than 25 cm in 6 MV beams, which was up to 6.5%. Gamma evaluation results comparing EPID profiles and reference ionization chamber profiles showed that for 6 and 18 MV beams, at least 91.8% and 90.9% of points had a Gamma<1 for all phantoms, respectively. But

  8. Internal dosimetry technical basis manual

    SciTech Connect

    Not Available

    1990-12-20

    The internal dosimetry program at the Savannah River Site (SRS) consists of radiation protection programs and activities used to detect and evaluate intakes of radioactive material by radiation workers. Examples of such programs are: air monitoring; surface contamination monitoring; personal contamination surveys; radiobioassay; and dose assessment. The objectives of the internal dosimetry program are to demonstrate that the workplace is under control and that workers are not being exposed to radioactive material, and to detect and assess inadvertent intakes in the workplace. The Savannah River Site Internal Dosimetry Technical Basis Manual (TBM) is intended to provide a technical and philosophical discussion of the radiobioassay and dose assessment aspects of the internal dosimetry program. Detailed information on air, surface, and personal contamination surveillance programs is not given in this manual except for how these programs interface with routine and special bioassay programs.

  9. SU-E-T-294: Simulations to Investigate the Feasibility of ‘dry’ Optical-CT Imaging for 3D Dosimetry

    SciTech Connect

    Chisholm, K; Rankine, L; Oldham, M

    2014-06-01

    Purpose: To perform simulations investigating the feasibility of “dry” optical-CT, and determine optimal design and scanning parameters for a novel dry tank telecentric optical-CT 3D dosimetry system. Such a system would have important advantages in terms of practical convenience and reduced cost. Methods: A Matlab based ray-tracing simulation platform, ScanSim, was used to model a telecentric system with a polyurethane dry tank, cylindrical dosimeter, and surrounding fluid. This program's capabilities were expanded for the geometry and physics of dry scanning. To categorize the effects of refractive index (RI) mismatches, simulations were run for several dosimeter (RI = 1.5−1.48) and fluid (RI = 1.55−1.33) combinations. Additional simulations examined the effect of increasing gap size (1–5mm) between the dosimeter and tank wall, and of changing the telecentric lens tolerance (0.5°−5°). The evaluation metric is the usable radius; the distance from the dosimeter center where the measured and true doses differ by less than 2%. Results: As the tank/dosimeter RI mismatch increases from 0–0.02, the usable radius decreases from 97.6% to 50.2%. The fluid RI for matching is lower than either the tank or dosimeter RI. Changing gap sizes has drastic effects on the usable radius, requiring more closely matched fluid at large gap sizes. Increasing the telecentric tolerance through a range from 0.5°–5.0° improved the usable radius for every combination of media. Conclusion: Dry optical-CT with telecentric lenses is feasible when the dosimeter and tank RIs are closely matched (<0.01 difference), or when data in the periphery is not required. The ScanSim tool proved very useful in situations when the tank and dosimeter have slight differences in RI by enabling estimation of the optimal choice of RI of the small amount of fluid still required. Some spoiling of the telecentric beam and increasing the tolerance helps recover the usable radius.

  10. Fundamentals of Radiation Dosimetry

    NASA Astrophysics Data System (ADS)

    Bos, Adrie J. J.

    2011-05-01

    The basic concepts of radiation dosimetry are reviewed on basis of ICRU reports and text books. The radiation field is described with, among others, the particle fluence. Cross sections for indirectly ionizing radiation are defined and indicated is how they are related to the mass energy transfer and mass energy absorption coefficients. Definitions of total and restricted mass stopping powers of directly ionizing radiation are given. The dosimetric quantities, kerma, absorbed dose and exposure together with the relations between them are discussed in depth. Finally it is indicated how the absorbed dose can be measured with a calorimeter by measuring the temperature increase and with an ionisation chamber measuring the charge produced by the ionizing radiation and making use of the Bragg-Gray relation.

  11. Fundamentals of Radiation Dosimetry

    SciTech Connect

    Bos, Adrie J. J.

    2011-05-05

    The basic concepts of radiation dosimetry are reviewed on basis of ICRU reports and text books. The radiation field is described with, among others, the particle fluence. Cross sections for indirectly ionizing radiation are defined and indicated is how they are related to the mass energy transfer and mass energy absorption coefficients. Definitions of total and restricted mass stopping powers of directly ionizing radiation are given. The dosimetric quantities, kerma, absorbed dose and exposure together with the relations between them are discussed in depth. Finally it is indicated how the absorbed dose can be measured with a calorimeter by measuring the temperature increase and with an ionisation chamber measuring the charge produced by the ionizing radiation and making use of the Bragg-Gray relation.

  12. Hanford internal dosimetry program manual

    SciTech Connect

    Carbaugh, E.H.; Sula, M.J.; Bihl, D.E.; Aldridge, T.L.

    1989-10-01

    This document describes the Hanford Internal Dosimetry program. Program Services include administrating the bioassay monitoring program, evaluating and documenting assessments of internal exposure and dose, ensuring that analytical laboratories conform to requirements, selecting and applying appropriate models and procedures for evaluating internal radionuclide deposition and the resulting dose, and technically guiding and supporting Hanford contractors in matters regarding internal dosimetry. 13 refs., 16 figs., 42 tabs.

  13. The International Reactor Dosimetry File.

    2008-08-07

    Version 01 The International Reactor Dosimetry File (IRDF-2002) contains recommended neutron cross-section data to be used for reactor neutron dosimetry by foil activation and subsequent neutron spectrum unfolding. It also contains selected recom�mended values for radiation damage cross-sections and benchmark neutron spectra. Two related programs available from NEADB and RSICC are: SPECTER-ANL (PSR-263) & STAY’SL (PSR-113).

  14. Fifth international radiopharmaceutical dosimetry symposium

    SciTech Connect

    Watson, E.E.; Schlafke-Stelson, A.T.

    1992-05-01

    This meeting was held to exchange information on how to get better estimates of the radiation absorbed dose. There seems to be a high interest of late in patient dosimetry; discussions were held in the light of revised risk estimates for radiation. Topics included: Strategies of Dose Assessment; Dose Estimation for Radioimmunotherapy; Dose Calculation Techniques and Models; Dose Estimation for Positron Emission Tomography (PET); Kinetics for Dose Estimation; and Small Scale Dosimetry and Microdosimetry. (VC)

  15. Laser heated thermoluminescence dosimetry

    SciTech Connect

    Justus, B.L.; Huston, A.L.

    1996-06-01

    We report a novel laser-heated thermoluminescence dosimeter that is radically different from previous laser-heated dosimeters. The dosimeter is a semiconductor and metal ion doped silica glass that has excellent optical transparency. The high optical quality of the glass essentially eliminates laser power loss due to light scattering. This efficient utilization of the laser power permits operation of the dosimeter without strong absorption of the laser, as is required in traditional laser-heated dosimetry. Our laser-heated dosimeter does not rely on the diffusion of heat from a separate, highly absorbing substrate, but operates via intimate, localized heating within the glass dosimeter due to the absorption of the laser light by rare earth ion dopants in the glass. Following absorption of the laser light, the rare earth ions transfer energy to the surrounding glass via nonradiative relaxation processes, resulting in rapid, localized temperature increases sufficient to release all the filled traps near the ions. As the heat diffuses radially away from the rare earth ions the temperature plummets dramatically on a manometer distance scale and the release of additional filled traps subsides. A key distinguishing feature of this laser-heated dosimeter is the ability to read the dose information more than once. While laser-heating provides complete information about the radiation exposure experienced by the glass due to the release of locally heated traps, the process leaves the remaining filled bulk traps undisturbed. The bulk traps can be read using traditional bulk heating methods and can provide a direct determination of an accumulated dose, measured following any number of laser-heated readouts. Laser-heated dosimetry measurements have been performed using a solid state diode laser for the readout following radiation exposure with a {sup 60}Co source.

  16. Image-Guided Stereotactic Spine Radiosurgery on a Conventional Linear Accelerator

    SciTech Connect

    Wang Jiazhu Rice, Roger; Mundt, Arno; Sandhu, Ajay; Murphy, Kevin

    2010-04-01

    Stereotactic radiosurgery for spinal metastasis consists of a high radiation dose delivered to the tumor in 1 to 5 fractions. Due to the high radiation dose in a single or fewer treatments, the precision of tumor localization and dose delivery is of great concern. Many groups have published their experiences of spinal radiosurgery with the use of CyberKnife System (Accuray Inc.). In this study, we report in detail our approach to stereotactic spine radiosurgery (SSRS) using a conventional linear accelerator (Varian Trilogy), utilizing the features of kilovolt on-board imaging (kV-OBI) and cone beam computed tomography (CBCT) for image guidance. We present our experience in various aspects of the SSRS procedure, including patient simulation and immobilization, intensity-modulated radiation treatment (IMRT) planning and beam selection, portal dosimetry for patient planning quality assurance (QA), and the use of image guidance in tumor localization prior to and during treatment delivery.

  17. Case Report: Gallbladder Varices in a Patient with Portal Vein Thrombosis Secondary to Hepatocellular Carcinoma

    PubMed Central

    Gnerre, Jeffrey; Sun, Yankai; Jedynak, Andrzej; Gilet, Anthony

    2016-01-01

    Gallbladder varices are a rare form of collateralization that develop in patients with portal hypertension. We present here a case of gallbladder varices accurately diagnosed by contrast enhanced CT imaging of the abdomen and confirmed by Color Doppler Sonography. A 76-year-old patient with hepatocellular carcinoma developed portal vein thrombosis due to tumor extension during the course of treatment and was incidentally discovered to have gallbladder varices. While most commonly asymptomatic, gallbladder varices are associated with increased risk of massive bleeding, either spontaneously or during cholecystectomy. As a result, the existence of such varices should be well documented if the patient is to undergo any abdominal surgical procedures. In addition, because of a particular association with portal vein thrombosis, patients with portal hypertension that are found to possess gallbladder varices should be evaluated for portal vein thrombosis. PMID:27761177

  18. Evaluation of dosimetry and image of very low-dose computed tomography attenuation correction for pediatric positron emission tomography/computed tomography: phantom study

    NASA Astrophysics Data System (ADS)

    Bahn, Y. K.; Park, H. H.; Lee, C. H.; Kim, H. S.; Lyu, K. Y.; Dong, K. R.; Chung, W. K.; Cho, J. H.

    2014-04-01

    In this study, phantom was used to evaluate attenuation correction computed tomography (CT) dose and image in case of pediatric positron emission tomography (PET)/CT scan. Three PET/CT scanners were used along with acryl phantom in the size for infant and ion-chamber dosimeter. The CT image acquisition conditions were changed from 10 to 20, 40, 80, 100 and 160 mA and from 80 to 100, 120 and 140 kVp, which aimed at evaluating penetrate dose and computed tomography dose indexvolume (CTDIvol) value. And NEMA PET Phantom™ was used to obtain PET image under the same CT conditions in order to evaluate each attenuation-corrected PET image based on standard uptake value (SUV) value and signal-to-noise ratio (SNR). In general, the penetrate dose was reduced by around 92% under the minimum CT conditions (80 kVp and 10 mA) with the decrease in CTDIvol value by around 88%, compared with the pediatric abdomen CT conditions (100 kVp and 100 mA). The PET image with its attenuation corrected according to each CT condition showed no change in SUV value and no influence on the SNR. In conclusion, if the minimum dose CT that is properly applied to body of pediatric patient is corrected for attenuation to ensure that the effective dose is reduced by around 90% or more compared with that for adult patient, this will be useful to reduce radiation exposure level.

  19. The Reusable Astronomy Portal (TRAP)

    NASA Astrophysics Data System (ADS)

    Donaldson, T.; Rogers, A.; Wallace, G.

    2012-09-01

    The Reusable Astronomy Portal (TRAP) aims to provide a common platform for rapidly deploying Astronomy Archives to the web. TRAP is currently under development for both the VAO Data Discovery Portal and the MAST Multi-Mission Portal (Figure 1). TRAP consists of 2 major software packages: the TRAP Client and the TRAP Server. The TRAP framework allows developers to deploy the Server, connect to data resources, then focus on building custom tools for the Client. TRAP is built upon proven industry technologies including the Ext/JS JavaScript Component Library, Mono.NET Web Services, and JSON message based APIs. The multi-layered architecture of TRAP decouples each layer: Client, Service and Data Access, enabling each to evolve independently over time. Although currently deployed to provide astronomy science data access, the TRAP architecture is flexible enough to thrive in any distributed data environment.

  20. Web Portal for Multicast Delivery Management.

    ERIC Educational Resources Information Center

    Mannaert, H.; De Gruyter, B.; Adriaenssens, P.

    2003-01-01

    Presents a Web portal for multicast communication management, which provides fully automatic service management with integrated provisioning of hardware equipment. Describes the software architecture, the implementation, and the application usage of the Web portal for multicast delivery. (Author/AEF)

  1. ODISEES Data Portal Announcement

    Atmospheric Science Data Center

    2015-11-13

    ... larger image The Ontology-Driven Interactive Search Environment for Earth Science, developed at the Atmospheric Science Data Center ... The Ontology-Driven Interactive Search Environment for Earth Science, developed at the Atmospheric Science Data Center ...

  2. Dosimetry for audit and clinical trials: challenges and requirements

    NASA Astrophysics Data System (ADS)

    Kron, T.; Haworth, A.; Williams, I.

    2013-06-01

    Many important dosimetry audit networks for radiotherapy have their roots in clinical trial quality assurance (QA). In both scenarios it is essential to test two issues: does the treatment plan conform with the clinical requirements and is the plan a reasonable representation of what is actually delivered to a patient throughout their course of treatment. Part of a sound quality program would be an external audit of these issues with verification of the equivalence of plan and treatment typically referred to as a dosimetry audit. The increasing complexity of radiotherapy planning and delivery makes audits challenging. While verification of absolute dose delivered at a reference point was the standard of external dosimetry audits two decades ago this is often deemed inadequate for verification of treatment approaches such as Intensity Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT). As such, most dosimetry audit networks have successfully introduced more complex tests of dose delivery using anthropomorphic phantoms that can be imaged, planned and treated as a patient would. The new challenge is to adapt this approach to ever more diversified radiotherapy procedures with image guided/adaptive radiotherapy, motion management and brachytherapy being the focus of current research.

  3. From EGEE Operations Portal towards EGI Operations Portal

    NASA Astrophysics Data System (ADS)

    Cordier, Hélène; L'Orphelin, Cyril; Reynaud, Sylvain; Lequeux, Olivier; Loikkanen, Sinikka; Veyre, Pierre

    Grid operators in EGEE have been using a dedicated dashboard as their central operational tool, stable and scalable for the last 5 years despite continuous upgrade from specifications by users, monitoring tools or data providers. In EGEE-III, recent regionalisation of operations led the Operations Portal developers to conceive a standalone instance of this tool. We will see how the dashboard reorganization paved the way for the re-engineering of the portal itself. The outcome is an easily deployable package customized with relevant information sources and specific decentralized operational requirements. This package is composed of a generic and scalable data access mechanism, Lavoisier; a renowned php framework for configuration flexibility, Symfony and a MySQL database. VO life cycle and operational information, EGEE broadcast and Downtime notifications are next for the major reorganization until all other key features of the Operations Portal are migrated to the framework. Features specifications will be sketched at the same time to adapt to EGI requirements and to upgrade. Future work on feature regionalisation, on new advanced features or strategy planning will be tracked in EGI- Inspire through the Operations Tools Advisory Group, OTAG, where all users, customers and third parties of the Operations Portal are represented from January 2010.

  4. Portal Monitor Future Development Work: Hardware Improvements

    SciTech Connect

    Browne, Michael C.

    2012-07-03

    LANL portal monitor was a modification of a previously installed (permanent) unattended monitoring system (UMS). Modifications to the UMS to make the portal were sometimes based on mistaken assumptions about exercise-specific installation and access. Philosophical approach to real-time portal differs in some areas from UMS.

  5. Characterising an aluminium oxide dosimetry system.

    PubMed

    Conheady, Clement F; Gagliardi, Frank M; Ackerly, Trevor

    2015-09-01

    In vivo dosimetry is recommended as a defence-in-depth strategy in radiotherapy treatments and is currently employed by clinics around the world. The characteristics of a new optically stimulated luminescence dosimetry system were investigated for the purpose of replacing an aging thermoluminescence dosimetry system for in vivo dosimetry. The stability of the system was not sufficient to satisfy commissioning requirements and therefore it has not been released into clinical service at this time. PMID:26224358

  6. Midline Dose Verification with Diode In Vivo Dosimetry for External Photon Therapy of Head and Neck and Pelvis Cancers During Initial Large-Field Treatments

    SciTech Connect

    Tung, Chuan-Jong; Yu, Pei-Chieh; Chiu, Min-Chi; Yeh, Chi-Yuan; Lee, Chung-Chi; Chao, Tsi-Chian

    2010-01-01

    During radiotherapy treatments, quality assurance/control is essential, particularly dose delivery to patients. This study was designed to verify midline doses with diode in vivo dosimetry. Dosimetry was studied for 6-MV bilateral fields in head and neck cancer treatments and 10-MV bilateral and anteroposterior/posteroanterior (AP/PA) fields in pelvic cancer treatments. Calibrations with corrections of diodes were performed using plastic water phantoms; 190 and 100 portals were studied for head and neck and pelvis treatments, respectively. Calculations of midline doses were made using the midline transmission, arithmetic mean, and geometric mean algorithms. These midline doses were compared with the treatment planning system target doses for lateral or AP (PA) portals and paired opposed portals. For head and neck treatments, all 3 algorithms were satisfactory, although the geometric mean algorithm was less accurate and more uncertain. For pelvis treatments, the arithmetic mean algorithm seemed unacceptable, whereas the other algorithms were satisfactory. The random error was reduced by using averaged midline doses of paired opposed portals because the asymmetric effect was averaged out. Considering the simplicity of in vivo dosimetry, the arithmetic mean and geometric mean algorithm should be adopted for head/neck and pelvis treatments, respectively.

  7. Portosystemic shunting in portal hypertension: evaluation with portal scintigraphy with transrectally administered I-123 IMP

    SciTech Connect

    Kashiwagi, T.; Azuma, M.; Ikawa, T.; Takehara, T.; Matsuda, H.; Yoshioka, H.; Mitsutani, N.; Koizumi, T.; Kimura, K.

    1988-10-01

    Portosystemic shunting was evaluated with rectal administration of iodine-123 iodoamphetamine (IMP) in seven patients without liver disease and 53 patients with liver cirrhosis. IMP (2-3 mCi (74-111 MBq)) was administered to the rectum through a catheter. Images of the chest and abdomen were obtained for up to 60 minutes with a scintillation camera interfaced with a computer. In all patients, images of the liver and/or lungs were observed within 5-10 minutes and became clear with time. In patients without liver disease, only liver images could be obtained, whereas the lung was visualized with or without the liver in all patients with liver cirrhosis. The portosystemic shunt index was calculated by dividing counts of lungs by counts of liver and lung. These values were significantly higher in liver cirrhosis, especially in the decompensated stage. Transrectal portal scintigraphy with IMP appears to be a useful method for noninvasive and quantitative evaluation of portosystemic shunting in portal hypertension.

  8. Taurine for EPR dosimetry.

    PubMed

    Maghraby, A; Mansour, A; Tarek, E

    2012-08-01

    EPR dosimetry is characterized by its non-destructive read-out and the possibility of dose archival. Here, taurine is proposed as a radiation dosimeter using EPR spectroscopy. The EPR spectrum of taurine was studied and assigned, and changes in the taurine EPR spectrum as a result of the change in both modulation amplitude and microwave power were quantified. For gamma radiation, the energy absorption coefficient and the collision mass stopping power of taurine were compared to the corresponding values of soft tissue and alanine, in addition to calculation of effective atomic numbers. The response of taurine to gamma radiation doses in the range from 0.1 to 50 kGy was investigated, as well as that in the range from 1.0 to 20.0 Gy using numerically enhanced EPR taurine spectra. Both response curves showed a linear behavior. In addition, the time dependence of radiation-induced radicals was studied for short (during the first 6 h after irradiation) and long (during about 3 months after irradiation) time periods, and a reasonable degree of stability of the taurine radicals was observed. It is concluded that taurine is a promising dosimeter, which is characterized by its simple spectrum, radical stability, and wide range of linear response to gamma radiation.

  9. Initial radiation dosimetry at Hiroshima and Nagasaki

    SciTech Connect

    Loewe, W.E.

    1983-09-01

    The dosimetry of A-bomb survivors at Hiroshima and Nagasaki is discussed in light of the new dosimetry developed in 1980 by the author. The important changes resulting from the new dosimetry are the ratios of neutron to gamma doses, particularly at Hiroshima. The implications of these changes in terms of epidemiology and radiation protection standards are discussed. (ACR)

  10. 4.2 Methods for Internal Dosimetry

    NASA Astrophysics Data System (ADS)

    Noßke, D.; Mattsson, S.; Johansson, L.

    This document is part of Subvolume A 'Fundamentals and Data in Radiobiology, Radiation Biophysics, Dosimetry and Medical Radiological Protection' of Volume 7 'Medical Radiological Physics' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It contains the Section '4.2 Methods for Internal Dosimetry' of the Chapter '4 Dosimetry in Nuclear Medicine Diagnosis and Therapy' with the contents:

  11. The new IAGOS Database Portal

    NASA Astrophysics Data System (ADS)

    Boulanger, Damien; Gautron, Benoit; Thouret, Valérie; Fontaine, Alain

    2016-04-01

    IAGOS (In-service Aircraft for a Global Observing System) is a European Research Infrastructure which aims at the provision of long-term, regular and spatially resolved in situ observations of the atmospheric composition. IAGOS observation systems are deployed on a fleet of commercial aircraft. The IAGOS database is an essential part of the global atmospheric monitoring network. It contains IAGOS-core data and IAGOS-CARIBIC (Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container) data. The IAGOS Database Portal (http://www.iagos.fr, damien.boulanger@obs-mip.fr) is part of the French atmospheric chemistry data center AERIS (http://www.aeris-data.fr). The new IAGOS Database Portal has been released in December 2015. The main improvement is the interoperability implementation with international portals or other databases in order to improve IAGOS data discovery. In the frame of the IGAS project (IAGOS for the Copernicus Atmospheric Service), a data network has been setup. It is composed of three data centers: the IAGOS database in Toulouse; the HALO research aircraft database at DLR (https://halo-db.pa.op.dlr.de); and the CAMS data center in Jülich (http://join.iek.fz-juelich.de). The CAMS (Copernicus Atmospheric Monitoring Service) project is a prominent user of the IGAS data network. The new portal provides improved and new services such as the download in NetCDF or NASA Ames formats, plotting tools (maps, time series, vertical profiles, etc.) and user management. Added value products are available on the portal: back trajectories, origin of air masses, co-location with satellite data, etc. The link with the CAMS data center, through JOIN (Jülich OWS Interface), allows to combine model outputs with IAGOS data for inter-comparison. Finally IAGOS metadata has been standardized (ISO 19115) and now provides complete information about data traceability and quality.

  12. Dosimetry of radium-223 and progeny

    SciTech Connect

    Fisher, D.R.; Sgouros, G.

    1999-01-01

    Radium-223 is a short-lived (11.4 d) alpha emitter with potential applications in radioimmunotherapy of cancer. Radium-223 can be complexed and linked to protein delivery molecules for specific tumor-cell targeting. It decays through a cascade of short-lived alpha- and beta-emitting daughters with emission of about 28 MeV of energy through complete decay. The first three alpha particles are essentially instantaneous. Photons associated with Ra-223 and progeny provide the means for tumor and normal-organ imaging and dosimetry. Two beta particles provide additional therapeutic value. Radium-223 may be produced economically and in sufficient amounts for widescale application. Many aspects of the chemistry of carrier-free isotope preparation, complexation, and linkage to the antibody have been developed and are being tested. The radiation dosimetry of a Ra-223-labeled antibody shows favorable tumor to normal tissue dose ratios for therapy. The 11.4-d half-life of Ra-223 allows sufficient time for immunoconjugate preparation, administration, and tumor localization by carrier antibodies before significant radiological decay takes place. If 0.01 percent of a 37 MBq (1 mCi) injection deposits in a one gram tumor mass, and if the activity is retained with a typical effective half-time (75 h), the absorbed dose will be 163 mGy MBq{sup {minus}1} (600 rad mCi{sup {minus}1}) administered. 49 refs., 5 figs., 2 tabs.

  13. Developing Interoperable Air Quality Community Portals

    NASA Astrophysics Data System (ADS)

    Falke, S. R.; Husar, R. B.; Yang, C. P.; Robinson, E. M.; Fialkowski, W. E.

    2009-04-01

    Web portals are intended to provide consolidated discovery, filtering and aggregation of content from multiple, distributed web sources targeted at particular user communities. This paper presents a standards-based information architectural approach to developing portals aimed at air quality community collaboration in data access and analysis. An important characteristic of the approach is to advance beyond the present stand-alone design of most portals to achieve interoperability with other portals and information sources. We show how using metadata standards, web services, RSS feeds and other Web 2.0 technologies, such as Yahoo! Pipes and del.icio.us, helps increase interoperability among portals. The approach is illustrated within the context of the GEOSS Architecture Implementation Pilot where an air quality community portal is being developed to provide a user interface between the portals and clearinghouse of the GEOSS Common Infrastructure and the air quality community catalog of metadata and data services.

  14. Dual Panal Planar Portal

    2000-12-01

    The D3P system is designed to provide a very fast imaging system in order to search for weapons on persons in an airport environment. The complete vision of the D3P system is to have two array systems facing each other. Version 2.3 of the software is designed to control and process data from a single panel. A second panel is expected to be added at a future date and the software will be modified atmore » that time to integrate the images from two panels at one time. The D3P software can be segmented into three specific tasks. The first task is data acquisition and scanner control. At the operator's request, this task commands the scanner to move and the radar transceiver-array to send data to the computer system in a known and well-ordered manner. The array is moved over the complete aperture in 1 to 2 seconds. At the completion of the array movement the second software task reconstructs the high-resolution image from the radar data utilizing the integrated DSP board. The third task displays the result to the computer screen for user review and analysis.« less

  15. Extrahepatic Portal Vein Obstruction and Portal Vein Thrombosis in Special Situations: Need for a New Classification

    PubMed Central

    Wani, Zeeshan A.; Bhat, Riyaz A.; Bhadoria, Ajeet S.; Maiwall, Rakhi

    2015-01-01

    Extrahepatic portal vein obstruction is a vascular disorder of liver, which results in obstruction and cavernomatous transformation of portal vein with or without the involvement of intrahepatic portal vein, splenic vein, or superior mesenteric vein. Portal vein obstruction due to chronic liver disease, neoplasm, or postsurgery is a separate entity and is not the same as extrahepatic portal vein obstruction. Patients with extrahepatic portal vein obstruction are generally young and belong mostly to Asian countries. It is therefore very important to define portal vein thrombosis as acute or chronic from management point of view. Portal vein thrombosis in certain situations such as liver transplant and postsurgical/liver transplant period is an evolving area and needs extensive research. There is a need for a new classification, which includes all areas of the entity. In the current review, the most recent literature of extrahepatic portal vein obstruction is reviewed and summarized. PMID:26021771

  16. Extrahepatic portal vein obstruction and portal vein thrombosis in special situations: Need for a new classification.

    PubMed

    Wani, Zeeshan A; Bhat, Riyaz A; Bhadoria, Ajeet S; Maiwall, Rakhi

    2015-01-01

    Extrahepatic portal vein obstruction is a vascular disorder of liver, which results in obstruction and cavernomatous transformation of portal vein with or without the involvement of intrahepatic portal vein, splenic vein, or superior mesenteric vein. Portal vein obstruction due to chronic liver disease, neoplasm, or postsurgery is a separate entity and is not the same as extrahepatic portal vein obstruction. Patients with extrahepatic portal vein obstruction are generally young and belong mostly to Asian countries. It is therefore very important to define portal vein thrombosis as acute or chronic from management point of view. Portal vein thrombosis in certain situations such as liver transplant and postsurgical/liver transplant period is an evolving area and needs extensive research. There is a need for a new classification, which includes all areas of the entity. In the current review, the most recent literature of extrahepatic portal vein obstruction is reviewed and summarized.

  17. Advances in kilovoltage x-ray beam dosimetry

    NASA Astrophysics Data System (ADS)

    Hill, Robin; Healy, Brendan; Holloway, Lois; Kuncic, Zdenka; Thwaites, David; Baldock, Clive

    2014-03-01

    This topical review provides an up-to-date overview of the theoretical and practical aspects of therapeutic kilovoltage x-ray beam dosimetry. Kilovoltage x-ray beams have the property that the maximum dose occurs very close to the surface and thus, they are predominantly used in the treatment of skin cancers but also have applications for the treatment of other cancers. In addition, kilovoltage x-ray beams are used in intra operative units, within animal irradiators and in on-board imagers on linear accelerators and kilovoltage dosimetry is important in these applications as well. This review covers both reference and relative dosimetry of kilovoltage x-ray beams and provides recommendations for clinical measurements based on the literature to date. In particular, practical aspects for the selection of dosimeter and phantom material are reviewed to provide suitable advice for medical physicists. An overview is also presented of dosimeters other than ionization chambers which can be used for both relative and in vivo dosimetry. Finally, issues related to the treatment planning and the use of Monte Carlo codes for solving radiation transport problems in kilovoltage x-ray beams are presented.

  18. 1. West portal of the mudshed abutting the west portal ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. West portal of the mudshed abutting the west portal of Tunnel 5, view to the northwest, 135mm lens. The flat-roofed reinforced concrete mudsheds, rocksheds, and snowsheds are a common feature of the Natron Cutoff over the summit of the Cascades. With the railroad located on a sidehill bench cut into the precipitous slopes, the sheds protect the track from rock and mud slides, as well as from avalanches. With a solid wall on the uphill side and a series of columns on the downhill side, they form a gallery-like effect from within. This mudshed was built concurrent with the tunnel, in 1927. Though none of the mudsheds on the line are scheduled to be modified, this shed was documented as an integral element of Tunnel 5. - Southern Pacific Railroad Natron Cutoff, Tunnel 5, Milepost 545.2, McCredie Springs, Lane County, OR

  19. Final Report Summary: Radiation dosimetry of Cu-64-labeled radiotherapy agents using PET [Positron Emission Tomography

    SciTech Connect

    Anderson, Carolyn J.; Cutler, P.D.

    2002-09-01

    This project began in 1996, and was completed in July 2001. The overall goals were to compare various methods of dosimetry of PET imaging agents, as well as develop more optimal methods. One of the major accomplishments of this grant was the human PET imaging studies of a positron-emitting radiopharmaceutical for somatostatin-receptor imaging, and subsequent dosimetry calculations resulting from this study. In addition, we collaborated with Darrell Fisher and Edmund Hui to develop a MIRD-hamster program for calculating hamster organ and tumor dosimetry in hamster models. Progress was made towards a point kernel approach to more accurately determining absorbed doses to normal organs, as well as towards co-registration of PET and MRI images. This report focuses on the progress made in the last 15 months of the grant, which in general is a summary of the progress over the 5 years the project was ongoing.

  20. Poster — Thur Eve — 25: Sensitivity to inhomogeneities for an in-vivo EPID dosimetry method

    SciTech Connect

    Peca, Stefano; Brown, Derek

    2014-08-15

    Introduction: The electronic portal imaging device (EPID) has the potential to be used for in vivo dosimetry during radiotherapy as an additional dose delivery check. We recently proposed a simple method of using the EPID for 2D-IVD based on correlation ratios. In this work we have investigated the sensitivity of our EPID-IVD to inhomogeneities. Methods: We used slab phantoms that simulate water, bone, and lung, arranged in various geometries. To simulate body contours non-orthogonal to the field, we used a water wedge. CT data of these phantoms was imported into MATLAB, in conjunction with EPID images acquired during irradiation, to calculate dose inside the phantom in isocenter plane. Each phantom was irradiated using a linear accelerator while images were acquired with the EPID (cine mode). Comparisons between EPID-calculated and TPS dose maps were: pixel-by-pixel dose difference, and 3%,3mm gamma evaluation. Results: In the homogeneous case, CAX dose difference was <1%, and 3%,3mm gamma analysis yielded 99% of points with gamma<1. For the inhomogeneous phantoms, agreement decreased with increasing inhomogeneity reaching up to 10% CAX dose difference with 10cm of lung. Results from the water wedge phantom suggest that the EPID-calculated dose can account for surface irregularities of approximately ±3cm. Conclusions: The EPID-based IVD investigated has limitations in the presence of large inhomogeneities. Nonetheless, CAX doses never differed by >15% from the TPS. This suggests that this EPID-IVD is capable of detecting gross dose delivery errors even in the presence of inhomogeneities, supporting its utility as an additional patient safety device.

  1. Biodistribution and Radiation Dosimetry in Humans of a New PET Ligand, 18F-PBR06, to Image Translocator Protein (18 kDa)

    PubMed Central

    Fujimura, Yota; Kimura, Yasuyuki; Siméon, Fabrice G.; Dickstein, Leah P.; Pike, Victor W.; Innis, Robert B.; Fujita, Masahiro

    2010-01-01

    As a PET biomarker for inflammation, translocator protein (18 kDa) (TSPO) can be measured with an 18F-labeled aryloxyanilide, 18F-N-fluoroacetyl-N-(2,5-dimethoxybenzyl)-2-phenoxyaniline (18F-PBR06), in the human brain. The objective of this study was to estimate the radiation absorbed doses of 18F-PBR06 based on biodistribution data in humans. Methods After the injection of 18F-PBR06, images were acquired from head to thigh in 7 healthy humans. Urine was collected at various time points. Radiation absorbed doses were estimated by the MIRD scheme. Results Moderate to high levels of radioactivity were observed in organs with high densities of TSPO and in organs of metabolism and excretion. Bone had low levels of radioactivity. The effective dose was 18.5 µSv/MBq. Conclusion The effective dose of 18F-PBR06, compared with other 18F radioligands, was moderate. This radioligand had negligible defluorination, as indirectly assessed by bone radioactivity. Doses to the gallbladder wall and spleen may limit the amount of permissible injected radioactivity. PMID:20008980

  2. Biodistribution and radiation dosimetry of a positron emission tomographic ligand, 18F-SP203, to image metabotropic glutamate subtype 5 receptors in humans

    PubMed Central

    Kimura, Yasuyuki; Siméon, Fabrice G.; Hatazawa, Jun; Mozley, P. David; Pike, Victor W.; Innis, Robert B.; Fujita, Masahiro

    2011-01-01

    Purpose A new PET ligand, 3-fluoro-5-(2-(2-18F-(fluoromethyl)-thiazol-4-yl)ethynyl)benzonitrile (18F-SP203), is a positron emission tomographic radioligand selective for metabotropic glutamate subtype 5 receptors. The purposes of this study were to estimate the radiation-absorbed doses of 18F-SP203 in humans and to determine from the distribution of radioactivity in bone structures with various proportions of bone and red marrow whether 18F-SP203 undergoes defluorination. Methods Whole-body images were acquired for 5 h after injecting 18F-SP203 in seven healthy humans. Urine was collected at various time points. Radiation-absorbed doses were estimated by the Medical Internal Radiation Dose scheme. Results After injecting 18F-SP203, the two organs with highest radiation exposure were urinary bladder wall and gallbladder wall, consistent with both urinary and fecal excretion. In the skeleton, most of the radioactivity was in bone structures that contain red marrow and not in those without red marrow. Although the dose to red marrow (30.9 μSv/MBq) was unusually high, the effective dose (17.8 μSv/MBq) of 18F-SP203 was typical of that of other 18F radiotracers. Conclusion 18F-SP203 causes an effective dose in humans typical of several other 18F radioligands and undergoes little defluorination. PMID:20585776

  3. 3D EPID-based in vivo dosimetry for IMRT and VMAT

    NASA Astrophysics Data System (ADS)

    Mijnheer, B.; Olaciregui-Ruiz, I.; Rozendaal, R.; Sonke, J.-J.; Spreeuw, H.; Tielenburg, R.; van Herk, M.; Vijlbrief, R.; Mans, A.

    2013-06-01

    In this paper the various approaches of EPID-based in vivo IMRT and VMAT dose verification, and their clinical implementation, are described. It will be shown that EPID-based in vivo dosimetry plays an important role in the total chain of verification procedures in a radiotherapy department. EPID-based dosimetry, in combination with in-room imaging, is a fast and accurate tool for 3D in vivo verification of VMAT delivery. EPID-based in vivo dosimetry provides clinically more useful information and is less time consuming than patient-specific pre-treatment dose verification. In addition to accurate 3D dose verification, in vivo EPID-based dosimetry will also detect major errors in the dose received by individual patients, and provides a safety net for advanced treatments such as IMRT and VMAT.

  4. Vertical flow chemical detection portal

    DOEpatents

    Linker, K.L.; Hannum, D.W.; Conrad, F.J.

    1999-06-22

    A portal apparatus is described for screening objects or persons for the presence of trace amounts of chemical substances such as illicit drugs or explosives. The apparatus has a test space, in which a person may stand, defined by two generally upright sides spanned by a horizontal transom. One or more fans in the transom generate a downward air flow (uni-directional) within the test space. The air flows downwardly from a high pressure upper zone, past the object or person to be screened. Air moving past the object dislodges from the surface thereof both volatile and nonvolatile particles of the target substance. The particles are entrained into the air flow which continues flowing downward to a lower zone of reduced pressure, where the particle-bearing air stream is directed out of the test space and toward preconcentrator and detection components. The sides of the portal are specially configured to partially contain and maintain the air flow. 3 figs.

  5. Vertical flow chemical detection portal

    DOEpatents

    Linker, Kevin L.; Hannum, David W.; Conrad, Frank James

    1999-01-01

    A portal apparatus for screening objects or persons for the presence of trace amounts of chemical substances such as illicit drugs or explosives. The apparatus has a test space, in which a person may stand, defined by two generally upright sides spanned by a horizontal transom. One or more fans in the transom generate a downward air flow (uni-directional) within the test space. The air flows downwardly from a high pressure upper zone, past the object or person to be screened. Air moving past the object dislodges from the surface thereof both volatile and nonvolatile particles of the target substance. The particles are entrained into the air flow which continues flowing downward to a lower zone of reduced pressure, where the particle-bearing air stream is directed out of the test space and toward preconcentrator and detection components. The sides of the portal are specially configured to partially contain and maintain the air flow.

  6. True 3D chemical dosimetry (gels, plastics): Development and clinical role

    NASA Astrophysics Data System (ADS)

    Schreiner, L. J.

    2015-01-01

    Since the introduction of volumetric chemical dosimetry with Fricke gel dosimeters in the 1980s, three-dimensional (3D) dosimetry has been a promising technique for the clinic, since it provides a unique methodology for 3D dose measurement of the complex conformal dose distributions achieved by modern techniques such as Intensity Modulated and Volumetric Arc Radiation Therapy. In the last decade, the potential for improved clinical applicability has been advanced by the development of improved 3D dosimeters such as normoxic polymer gel systems, radiochromic plastics (such as PRESAGE) and, recently, newer radiochromic gel dosimeters. Some of these new 3D dosimetry systems were enabled by the availability of optical computed tomography imaging systems for fast dose readout. However, despite its promise, true 3D dosimetry is still not widely practiced in the community. Its use has been confined primarily to select centres of expertise and to specialised quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. In this paper I review some of the current 3D chemical dosimeters available, discuss the requirements for their use and briefly review the roles that these systems can provide to complement the other dose delivery validation approaches available in the clinic. I conclude by describing two roles that may be uniquely served by 3D chemical dosimetry in end-to-end process testing and validation in the complex environment coming into play with the development of Image Guided Adaptive Radiation Therapy.

  7. Plutonium worker dosimetry.

    PubMed

    Birchall, Alan; Puncher, M; Harrison, J; Riddell, A; Bailey, M R; Khokryakov, V; Romanov, S

    2010-05-01

    Epidemiological studies of the relationship between risk and internal exposure to plutonium are clearly reliant on the dose estimates used. The International Commission on Radiological Protection (ICRP) is currently reviewing the latest scientific information available on biokinetic models and dosimetry, and it is likely that a number of changes to the existing models will be recommended. The effect of certain changes, particularly to the ICRP model of the respiratory tract, has been investigated for inhaled forms of (239)Pu and uncertainties have also been assessed. Notable effects of possible changes to respiratory tract model assumptions are (1) a reduction in the absorbed dose to target cells in the airways, if changes under consideration are made to the slow clearing fraction and (2) a doubling of absorbed dose to the alveolar region for insoluble forms, if evidence of longer retention times is taken into account. An important factor influencing doses for moderately soluble forms of (239)Pu is the extent of binding of dissolved plutonium to lung tissues and assumptions regarding the extent of binding in the airways. Uncertainty analyses have been performed with prior distributions chosen for application in epidemiological studies. The resulting distributions for dose per unit intake were lognormal with geometric standard deviations of 2.3 and 2.6 for nitrates and oxides, respectively. The wide ranges were due largely to consideration of results for a range of experimental data for the solubility of different forms of nitrate and oxides. The medians of these distributions were a factor of three times higher than calculated using current default ICRP parameter values. For nitrates, this was due to the assumption of a bound fraction, and for oxides due mainly to the assumption of slower alveolar clearance. This study highlights areas where more research is needed to reduce biokinetic uncertainties, including more accurate determination of particle transport rates

  8. Z-portal dark matter

    SciTech Connect

    Arcadi, Giorgio; Mambrini, Yann; Richard, Francois

    2015-03-11

    We propose to generalize the extensions of the Standard Model where the Z boson serves as a mediator between the Standard Model sector and the dark sector χ. We show that, like in the Higgs portal case, the combined constraints from the recent direct searches restrict severely the nature of the coupling of the dark matter to the Z boson and set a limit m{sub χ}≳200 GeV (except in a very narrow region around the Z-pole region). Using complementarity between spin dependent, spin independent and FERMI limits, we predict the nature of this coupling, more specifically the axial/vectorial ratio that respects a thermal dark matter coupled through a Z-portal while not being excluded by the current observations. We also show that the next generation of experiments of the type LZ or XENON1T will test Z-portal scenario for dark matter mass up to 2 TeV. The condition of a thermal dark matter naturally predicts the spin-dependent scattering cross section on the neutron to be σ{sub χn}{sup SD}≃10{sup −40} cm{sup 2}, which then becomes a clear prediction of the model and a signature testable in the near future experiments.

  9. Uzbekistan Radiation Portal Monnitoring System

    SciTech Connect

    Richardson, J; Knapp, R; Loshak, A; Yuldashev, B; Petrenko, V

    2005-06-10

    The work proposed in this presentation builds on the foundation set by the DTRA funded demonstration project begun in 2000 and completed in December of 2003. This previous work consisted of two phases whose overall objective was to install portal radiation monitors at four select ports-of-entry in Uzbekistan (Tashkent International Airport, Gisht-Kuprik (Kazakhstan border), Alat (Turkmenistan border), and Termez (Afghanistan border)) in order to demonstrate their effectiveness in preventing the illicit trafficking of nuclear materials. The objectives also included developing and demonstrating capabilities in the design, installation, operation, training, and maintenance of a radiation portal monitoring system. The system and demonstration project has proved successful in many ways. An effective working relationship among the Uzbekistan Customs Services, Uzbekistan Border Guards, and Uzbekistan Institute of Nuclear Physics has been developed. There has been unprecedented openness with the sharing of portal monitor data with Lawrence Livermore National Laboratory. The system has proved to be effective, with detection of illicit trafficking, and, at Alat, an arrest of three persons illegally transporting radioactive materials into Turkmenistan. The demonstration project has made Uzbekistan a model nonproliferation state in Central Asia and, with an expanded program, places them in a position to seal a likely transit route for illicit nuclear materials. These results will be described. In addition, this work is currently being expanded to include additional ports-of-entry in Uzbekistan. The process for deciding on which additional ports-of-entry to equip will also be described.

  10. The Higgs portal above threshold

    DOE PAGES

    Craig, Nathaniel; Lou, Hou Keong; McCullough, Matthew; Thalapillil, Arun

    2016-02-18

    The discovery of the Higgs boson opens the door to new physics interacting via the Higgs Portal, including motivated scenarios relating to baryogenesis, dark matter, and electroweak naturalness. In this study, we systematically explore the collider signatures of singlet scalars produced via the Higgs Portal at the 14TeV LHC and a prospective 100TeV hadron collider. We focus on the challenging regime where the scalars are too heavy to be produced in the decays of an on-shell Higgs boson, and instead are produced primarily via an o ff-shell Higgs. Assuming these scalars escape the detector, promising channels include missing energy inmore » association with vector boson fusion, monojets, and top pairs. In addition, we forecast the sensitivity of searches in these channels at √s = 14 & 100 TeV and compare collider reach to the motivated parameter space of singlet-assisted electroweak baryogenesis, Higgs Portal dark matter, and neutral naturalness.« less

  11. Reflections of pressure waves at tunnel portals

    NASA Astrophysics Data System (ADS)

    Brown, J. M. B.; Vardy, A. E.

    1994-05-01

    Reflections of plane waves from the open ends (portals) of axisymmetric pipes and plane two-dimensional (2-D) channels are investigated analytically, numerically, and experimentally. An analytical approach developed by Rudinger for pressure decay at an axisymmetric, flanged portal is extended to longer times, and equivalent analyses are developed for reflections from unflanged portals - both axisymmetric and plane 2-D. Predictions for the latter case are compared with numerical results from a computer program based on a 2-D method of bicharacteristics. The theoretical results are compared with measurements from a low pressure shock tube, which was used to investigate alternative end configurations including scarfed portals with and without flange plates. These confirm that the rate of pressure decay is much slower in the plane 2-D case and that flange plates further reduce the rate of decay, albeit slightly. Scarfed portals are shown to cause more uniform decay rates than 90 deg portals.

  12. Noncirrhotic portal fibrosis after Wilms' tumor therapy

    SciTech Connect

    Barnard, J.A.; Marshall, G.S.; Neblett, W.W.; Gray, G.; Ghishan, F.K.

    1986-04-01

    A 9-yr-old girl developed massive hemorrhage from esophageal varices 2 yr after combined modality therapy for Wilms' tumor. Evaluation showed a patent extrahepatic portal venous system and an elevated splenic pulp pressure. In contrast to previous reports of hepatopathy after irradiation injury, histologic sections of the liver did not demonstrate occlusion of the central veins, but rather a diffuse obliteration of intrahepatic portal venous radicles. This pattern of noncirrhotic portal fibrosis has not been described following antitumor therapy.

  13. Preduodenal portal vein: its surgical significance.

    PubMed

    Makey, D A; Bowen, J C

    1978-11-01

    Preduodenal portal vein is a rare anatomical variant which may be one of many anomalies in the neonate with duodenal "atresia." Preduodenal portal vein also may be an occasional finding in an adult undergoing biliary, gastric, or pancreatic surgery. Awareness and recognition of the anomaly are essential for the avoidance of injury during such operations. We report here a symptomless patient whose preduodenal portal vein was discovered at cholecystectomy.

  14. Ascites due to pre-sinusoidal portal hypertension in dogs: a retrospective analysis of 17 cases.

    PubMed

    James, F E; Knowles, G W; Mansfield, C S; Robertson, I D

    2008-05-01

    Accumulation of a pure transudate abdominal effusion in the absence of significant hypoalbuminaemia is uncommon in dogs and is due to pre-sinusoidal portal hypertension. Reported causes of pre-sinusoidal portal hypertension vary, but suggest a reasonable prognosis. A retrospective analysis of 17 dogs that presented to our institution with ascites due to pre-sinusoidal portal hypertension identified idiopathic hepatic fibrosis or canine chronic hepatitis as the underlying cause in the majority of cases. Twelve (70.5%) dogs were 4 years of age or younger at time of presentation. Total serum protein was higher in dogs with chronic hepatitis than it was in dogs without inflammatory disease. The prognosis was generally poor and no histological, imaging or biochemical parameters were useful as prognostic indicators. Dogs died or were euthanased due to severe clinical signs associated with the portal hypertension and/or perceived poor prognosis.

  15. The design and fabrication of two portal vein flow phantoms by different methods

    SciTech Connect

    Yunker, Bryan E. Lanning, Craig J.; Shandas, Robin; Hunter, Kendall S.; Chen, S. James

    2014-02-15

    Purpose: This study outlines the design and fabrication techniques for two portal vein flow phantoms. Methods: A materials study was performed as a precursor to this phantom fabrication effort and the desired material properties are restated for continuity. A three-dimensional portal vein pattern was created from the Visual Human database. The portal vein pattern was used to fabricate two flow phantoms by different methods with identical interior surface geometry using computer aided design software tools and rapid prototyping techniques. One portal flow phantom was fabricated within a solid block of clear silicone for use on a table with Ultrasound or within medical imaging systems such as MRI, CT, PET, or SPECT. The other portal flow phantom was fabricated as a thin walled tubular latex structure for use in water tanks with Ultrasound imaging. Both phantoms were evaluated for usability and durability. Results: Both phantoms were fabricated successfully and passed durability criteria for flow testing in the next project phase. Conclusions: The fabrication methods and materials employed for the study yielded durable portal vein phantoms.

  16. SU-E-T-05: A 2D EPID Transit Dosimetry Model Based On An Empirical Quadratic Formalism

    SciTech Connect

    Tan, Y; Metwaly, M; Glegg, M; Baggarley, S; Elliott, A

    2014-06-01

    Purpose: To describe a 2D electronic portal imaging device (EPID) transit dosimetry model, based on an empirical quadratic formalism, that can predict either EPID or in-phantom dose distribution for comparisons with EPID captured image or treatment planning system (TPS) dose respectively. Methods: A quadratic equation can be used to relate the reduction in intensity of an exit beam to the equivalent path length of the attenuator. The calibration involved deriving coefficients from a set of dose planes measured for homogeneous phantoms with known thicknesses under reference conditions. In this study, calibration dose planes were measured with EPID and ionisation chamber (IC) in water for the same reference beam (6MV, 100mu, 20×20cm{sup 2}) and set of thicknesses (0–30cm). Since the same calibration conditions were used, the EPID and IC measurements can be related through the quadratic equation. Consequently, EPID transit dose can be predicted from TPS exported dose planes and in-phantom dose can be predicted using EPID distribution captured during treatment as an input. The model was tested with 4 open fields, 6 wedge fields, and 7 IMRT fields on homogeneous and heterogeneous phantoms. Comparisons were done using 2D absolute gamma (3%/3mm) and results were validated against measurements with a commercial 2D array device. Results: The gamma pass rates for comparisons between EPID measured and predicted ranged from 93.6% to 100.0% for all fields and phantoms tested. Results from this study agreed with 2D array measurements to within 3.1%. Meanwhile, comparisons in-phantom between TPS computed and predicted ranged from 91.6% to 100.0%. Validation with 2D array device was not possible for inphantom comparisons. Conclusion: A 2D EPID transit dosimetry model for treatment verification was described and proven to be accurate. The model has the advantage of being generic and allows comparisons at the EPID plane as well as multiple planes in-phantom.

  17. Web-based Service Portal in Healthcare

    NASA Astrophysics Data System (ADS)

    Silhavy, Petr; Silhavy, Radek; Prokopova, Zdenka

    Information delivery is one the most important task in healthcare. The growing sector of electronic healthcare has an important impact on the information delivery. There are two basic approaches towards information delivering. The first is web portal and second is touch-screen terminal. The aim of this paper is to investigate the web-based service portal. The most important advantage of web-based portal in the field of healthcare is an independent access for patients. This paper deals with the conditions and frameworks for healthcare portals

  18. Portal hypertension: state of the art.

    PubMed

    Gatta, A; Sacerdoti, D; Bolognesi, M; Merkel, C

    1999-05-01

    In the last decade, the knowledge of the pathogenesis of portal hypertension has increased dramatically. Indeed, apart from the well-known pathogenetic importance of structural factors, the role of vasoactive factors, which enhance the increase in intrahepatic resistance, has been highlighted. The two pathogenetic factors of portal hypertension are: the increase in portal outflow resistance and an increase in splanchnic blood flow, which worsens and maintains the increased pressure in the portal vein. The increase in portal inflow is part of the hyperdynamic circulatory syndrome, which is a haemodynamic characteristic of cirrhotic patients. In portal hypertensive patients, almost all the known vasoactive systems/substances are activated or increased and the most recent studies have stressed the importance of the endothelial factors, such as endothelins, nitric oxide and prostaglandins. Knowledge of the haemodynamic mechanisms allows a pathogenetic approach to the treatment of portal hypertension, particularly as far as medical therapy is concerned. The main categories of drugs used are: the vasoconstrictors (i.e., vasopressin, glypressin, somatostatin, non-selective beta-blockers), which act by decreasing portal inflow, and the vasodilators (i.e., nitroderivatives), which act mainly by decreasing intrahepatic portal resistance. Moreover, technological developments have introduced new tools for diagnosis, such as echo-colour-Doppler, and therapy, like variceal banding and transjugular intrahepatic porto-systemic shunt.

  19. The Latin American Biological Dosimetry Network (LBDNet).

    PubMed

    García, O; Di Giorgio, M; Radl, A; Taja, M R; Sapienza, C E; Deminge, M M; Fernández Rearte, J; Stuck Oliveira, M; Valdivia, P; Lamadrid, A I; González, J E; Romero, I; Mandina, T; Guerrero-Carbajal, C; ArceoMaldonado, C; Cortina Ramírez, G E; Espinoza, M; Martínez-López, W; Di Tomasso, M

    2016-09-01

    Biological Dosimetry is a necessary support for national radiation protection programmes and emergency response schemes. The Latin American Biological Dosimetry Network (LBDNet) was formally founded in 2007 to provide early biological dosimetry assistance in case of radiation emergencies in the Latin American Region. Here are presented the main topics considered in the foundational document of the network, which comprise: mission, partners, concept of operation, including the mechanism to request support for biological dosimetry assistance in the region, and the network capabilities. The process for network activation and the role of the coordinating laboratory during biological dosimetry emergency response is also presented. This information is preceded by historical remarks on biological dosimetry cooperation in Latin America. A summary of the main experimental and practical results already obtained by the LBDNet is also included.

  20. Results from 2010 Caliban Criticality Dosimetry Intercomparison

    SciTech Connect

    Veinot, K. G.

    2011-10-12

    The external dosimetry program participated in a criticality dosimetry intercomparison conducted at the Caliban facility in Valduc, France in 2010. Representatives from the dosimetry and instrumentation groups were present during testing which included irradiations of whole-body beta/gamma (HBGT) and neutron thermoluminescent dosimeters (TLDs), a fixed nuclear accident dosimeter (FNAD), electronic alarming dosimeters, and a humanoid phantom filled with reference man concentrations of sodium. This report reviews the testing procedures, preparations, irradiations, and presents results of the tests.

  1. [Diagnosis and treatment of portal thrombosis in liver cirrhosis].

    PubMed

    Seijo, Susana; García-Criado, Angeles; Darnell, Anna; García-Pagán, Juan Carlos

    2012-11-01

    Improved imaging techniques and the routine use of color Doppler ultrasound in the follow-up of patients with liver cirrhosis has increased diagnosis of portal vein thrombosis (PVT) in these patients. The extension of PVT should be evaluated with computed tomography angiography or magnetic resonance angiography. The natural history of PVT in cirrhosis and its impact on liver disease is unknown but it seems clear that PVT could increase the morbidity and mortality associated with liver transplantation and can even be a contraindication to this procedure when the thrombus extends to the superior mesenteric vein. Anticoagulation is a relatively safe and effective treatment in achieving recanalization of the splenoportal axis or in preventing progression of thrombosis and is therefore frequently used. The use of transjugular intrahepatic portosystemic shunts (TIPS) is reserved for patients unresponsive to anticoagulation or in those with severe complications of portal hypertension.

  2. NCRP Program Area Committee 6: Radiation Measurements and Dosimetry.

    PubMed

    Simon, Steven L; Zeman, Gary H

    2016-02-01

    Program Area Committee (PAC) 6 of the National Council on Radiation Protection and Measurements provides guidance for radiation measurements and dosimetry--one of the most fundamental scientific areas of the Council's expertise. Seminal reports published by PAC 6 over many decades have documented the scientific and technical foundations of radiation measurements and dosimetry for generations of radiation scientists and radiation protection professionals. Ongoing work of PAC 6 is driven by advancing technology, such as development of new types of instruments, biodosimetry and nanotechnology; by evolving understanding of radiation hazards, such as effects on the lens of the eye and risks as from some high-dose medical imaging procedures; and by new situations faced in the modern socio-political environment including radiological and nuclear threats. The activities of PAC 6 are intended to formulate and document the dosimetric framework for radiological science to address these ever-emerging challenges. PMID:26717161

  3. NCRP Program Area Committee 6: Radiation Measurements and Dosimetry.

    PubMed

    Simon, Steven L; Zeman, Gary H

    2016-02-01

    Program Area Committee (PAC) 6 of the National Council on Radiation Protection and Measurements provides guidance for radiation measurements and dosimetry--one of the most fundamental scientific areas of the Council's expertise. Seminal reports published by PAC 6 over many decades have documented the scientific and technical foundations of radiation measurements and dosimetry for generations of radiation scientists and radiation protection professionals. Ongoing work of PAC 6 is driven by advancing technology, such as development of new types of instruments, biodosimetry and nanotechnology; by evolving understanding of radiation hazards, such as effects on the lens of the eye and risks as from some high-dose medical imaging procedures; and by new situations faced in the modern socio-political environment including radiological and nuclear threats. The activities of PAC 6 are intended to formulate and document the dosimetric framework for radiological science to address these ever-emerging challenges.

  4. Methods and computer readable medium for improved radiotherapy dosimetry planning

    DOEpatents

    Wessol, Daniel E.; Frandsen, Michael W.; Wheeler, Floyd J.; Nigg, David W.

    2005-11-15

    Methods and computer readable media are disclosed for ultimately developing a dosimetry plan for a treatment volume irradiated during radiation therapy with a radiation source concentrated internally within a patient or incident from an external beam. The dosimetry plan is available in near "real-time" because of the novel geometric model construction of the treatment volume which in turn allows for rapid calculations to be performed for simulated movements of particles along particle tracks therethrough. The particles are exemplary representations of alpha, beta or gamma emissions emanating from an internal radiation source during various radiotherapies, such as brachytherapy or targeted radionuclide therapy, or they are exemplary representations of high-energy photons, electrons, protons or other ionizing particles incident on the treatment volume from an external source. In a preferred embodiment, a medical image of a treatment volume irradiated during radiotherapy having a plurality of pixels of information is obtained.

  5. Neutron personnel dosimetry intecomparison studies

    SciTech Connect

    Sims, C.S.

    1991-01-01

    The Dosimetry Applications Research (DOSAR) Group at the Oak Ridge National Laboratory (ORNL) has conducted sixteen Neutron Personnel Dosimetry Intercomparison Studies (PDIS) since 1974. During these studies dosimeters are mailed to DOSAR, exposed to low-level (typically in the 0.3 -- 5.0 mSv range) neutron dose equivalents in a variety of mixed neutron-gamma radiation fields, and then returned to the participants for evaluation. The Health Physics Research Reactor (HPRR) was used as the primary radiation source in PDIS 1--12 and radioisotopic neutron sources at DOSAR's Radiation Calibration Laboratory (RADCAL) were mainly used, along with sources and accelerators at cooperating institutions, in PDIS 13--16. Conclusions based on 13,560 measurements made by 146 different participating organizations (102 - US) are presented.

  6. Acquisition of Portal Venous Circulating Tumor Cells From Patients With Pancreaticobiliary Cancers by Endoscopic Ultrasound

    PubMed Central

    Catenacci, Daniel V. T.; Chapman, Christopher G.; Xu, Peng; Koons, Ann; Konda, Vani J.; Siddiqui, Uzma D.; Waxman, Irving

    2016-01-01

    BACKGROUND & AIMS Tumor cells circulate in low numbers in peripheral blood; their detection is used predominantly in metastatic disease. We evaluated the feasibility and safety of sampling portal venous blood via endoscopic ultrasound (EUS) to count portal venous circulating tumor cells (CTCs), compared with paired peripheral CTCs, in patients with pancreaticobiliary cancers (PBCs). METHODS In a single-center cohort study, we evaluated 18 patients with suspected PBCs. Under EUS guidance, a 19-gauge EUS fine needle was advanced transhepatically into the portal vein and as many as four 7.5-mL aliquots of blood were aspirated. Paired peripheral blood samples were obtained. Epithelial-derived CTCs were sorted magnetically based on expression of epithelial cell adhesion molecules; only those with a proper morphology and found to be CD45 negative and positive for cytokeratins 8, 18, and/ or 19 and 4′,6-diamidino-2-phenylindole were considered to be CTCs. For 5 samples, CTCs also were isolated by flow cytometry and based on CD45 depletion. ImageStream was used to determine the relative protein levels of P16, SMAD4, and P53. DNA was extracted from CTCs for sequencing of select KRAS codons. RESULTS There were no complications from portal vein blood acquisition. We detected CTCs in portal vein samples from all 18 patients (100%) vs peripheral blood samples from only 4 patients (22.2%). Patients with confirmed PBCs had a mean of 118.4 ± 36.8 CTCs/7.5 mL portal vein blood, compared with a mean of 0.8 ± 0.4 CTCs/7.5 mL peripheral blood (P < .01). The 9 patients with nonmetastatic, resectable, or borderline-resectable PBCs had a mean of 83.2 CTCs/7.5 mL portal vein blood (median, 62.0 CTCs/7.5 mL portal vein blood). In a selected patient, portal vein CTCs were found to carry the same mutations as those detected in a metastatic lymph node and expressed similar levels of P16, SMAD4, and P53 proteins. CONCLUSIONS It is feasible and safe to collect portal venous blood from

  7. ESO's User Portal: lessons learned

    NASA Astrophysics Data System (ADS)

    Chavan, A. M.; Tacconi-Garman, L. E.; Peron, M.; Sogni, F.; Dorigo, D.; Nass, P.; Fourniol, N.; Sforna, D.; Haggouchi, K.; Dolensky, M.

    2008-07-01

    ESO introduced a User Portal for its scientific services in November 2007. Registered users have a central entry point for the Observatory's offerings, the extent of which depends on the users' roles - see [1]. The project faced and overcame a number of challenging hurdles between inception and deployment, and ESO learned a number of useful lessons along the way. The most significant challenges were not only technical in nature; organization and coordination issues took a significant toll as well. We also indicate the project's roadmap for the future.

  8. Portal hypertensive polyps, a new entity?

    PubMed

    Martín Domínguez, Verónica; Díaz Méndez, Ariel; Santander, Cecilio; García-Buey, Luisa

    2016-05-01

    We present a case of a 62 year old woman with history of liver cirrhosis secondary to autoimmune hepatitis, with portal hypertension and coagulopathy. Gastroscopy findings were a polypoid and polylobed lesions in the gastric antrum. These were removed and the pathological study described hyperplastic polyps with edema, vascular congestion and hyperplasia of smooth muscle, corresponding to "portal hypertensive polyps" (PHP). PMID:27188590

  9. Factors Affecting Faculty Web Portal Usability

    ERIC Educational Resources Information Center

    Bringula, Rex P.; Basa, Roselle S.

    2011-01-01

    The study investigated the factors that might significantly affect web portal usability. Results of the study were intended to serve as inputs for faculty web portal development of the University of the East-Manila. Descriptive statistics utilized questionnaire data from 82 faculty members. The data showed that most of the respondents were…

  10. Pancreatic pseudocyst rupture into the portal vein.

    PubMed

    Dawson, Brian C; Kasa, David; Mazer, Mark A

    2009-07-01

    A patient with a pancreatic pseudocyst rupture into the portal vein with a resultant noninfectious systemic inflammatory response syndrome and subsequent portal vein thrombosis diagnosed by computed tomography and ultrasonography is reported. A review of the existing English literature on this rare complication is also provided. PMID:19561436

  11. Feasibility study of a dual detector configuration concept for simultaneous megavoltage imaging and dose verification in radiotherapy

    SciTech Connect

    Deshpande, Shrikant; McNamara, Aimee L.; Holloway, Lois; Metcalfe, Peter; Vial, Philip

    2015-04-15

    Purpose: To test the feasibility of a dual detector concept for comprehensive verification of external beam radiotherapy. Specifically, the authors test the hypothesis that a portal imaging device coupled to a 2D dosimeter provides a system capable of simultaneous imaging and dose verification, and that the presence of each device does not significantly detract from the performance of the other. Methods: The dual detector configuration comprised of a standard radiotherapy electronic portal imaging device (EPID) positioned directly on top of an ionization-chamber array (ICA) with 2 cm solid water buildup material (between EPID and ICA) and 5 cm solid backscatter material. The dose response characteristics of the ICA and the imaging performance of the EPID in the dual detector configuration were compared to the performance in their respective reference clinical configurations. The reference clinical configurations were 6 cm solid water buildup material, an ICA, and 5 cm solid water backscatter material as the reference dosimetry configuration, and an EPID with no additional buildup or solid backscatter material as the reference imaging configuration. The dose response of the ICA was evaluated by measuring the detector’s response with respect to off-axis position, field size, and transit object thickness. Clinical dosimetry performance was evaluated by measuring a range of clinical intensity-modulated radiation therapy (IMRT) beams in transit and nontransit geometries. The imaging performance of the EPID was evaluated quantitatively by measuring the contrast-to-noise ratio (CNR) and spatial resolution. Images of an anthropomorphic phantom were also used for qualitative assessment. Results: The measured off-axis and field size response with the ICA in both transit and nontransit geometries for both dual detector configuration and reference dosimetry configuration agreed to within 1%. Transit dose response as a function of object thickness agreed to within 0.5%. All

  12. Idiopathic noncirrhotic portal hypertension: current perspectives.

    PubMed

    Riggio, Oliviero; Gioia, Stefania; Pentassuglio, Ilaria; Nicoletti, Valeria; Valente, Michele; d'Amati, Giulia

    2016-01-01

    The term idiopathic noncirrhotic portal hypertension (INCPH) has been recently proposed to replace terms, such as hepatoportal sclerosis, idiopathic portal hypertension, incomplete septal cirrhosis, and nodular regenerative hyperplasia, used to describe patients with a hepatic presinusoidal cause of portal hypertension of unknown etiology, characterized by features of portal hypertension (esophageal varices, nonmalignant ascites, porto-venous collaterals), splenomegaly, patent portal, and hepatic veins and no clinical and histological signs of cirrhosis. Physicians should learn to look for this condition in a number of clinical settings, including cryptogenic cirrhosis, a disease known to be associated with INCPH, drug administration, and even chronic alterations in liver function tests. Once INCPH is clinically suspected, liver histology becomes mandatory for the correct diagnosis. However, pathologists should be familiar with the histological features of INCPH, especially in cases in which histology is not only requested to exclude liver cirrhosis. PMID:27555800

  13. Idiopathic noncirrhotic portal hypertension: current perspectives

    PubMed Central

    Riggio, Oliviero; Gioia, Stefania; Pentassuglio, Ilaria; Nicoletti, Valeria; Valente, Michele; d’Amati, Giulia

    2016-01-01

    The term idiopathic noncirrhotic portal hypertension (INCPH) has been recently proposed to replace terms, such as hepatoportal sclerosis, idiopathic portal hypertension, incomplete septal cirrhosis, and nodular regenerative hyperplasia, used to describe patients with a hepatic presinusoidal cause of portal hypertension of unknown etiology, characterized by features of portal hypertension (esophageal varices, nonmalignant ascites, porto-venous collaterals), splenomegaly, patent portal, and hepatic veins and no clinical and histological signs of cirrhosis. Physicians should learn to look for this condition in a number of clinical settings, including cryptogenic cirrhosis, a disease known to be associated with INCPH, drug administration, and even chronic alterations in liver function tests. Once INCPH is clinically suspected, liver histology becomes mandatory for the correct diagnosis. However, pathologists should be familiar with the histological features of INCPH, especially in cases in which histology is not only requested to exclude liver cirrhosis. PMID:27555800

  14. Therapeutic Challenges for Symptomatic Portal Cavernoma Cholangiopathy.

    PubMed

    Cavași, Adriana; Mercea, Voicu; Anton, Ofelia; Puia, Ion Cosmin

    2016-09-01

    Although transjugular intrahepatic portosystemic shunts are most frequently used for the management of portal hypertension, the surgical approach is preferred for symptomatic portal cavernoma cholangiopathy. We present the case of a 25-year old female patient with a portal cavernoma secondary to catheterization of the umbilical vein at birth. She had had two episodes of esophageal variceal bleeding, successfully treated by endoscopic banding. and an episode of acute cholangitis secondary to portal cavernoma cholangiopathy. Endoscopic sphincterotomy and biliary stenting were performed, and were followed by repeated episodes of biliary stent occlusion. The last biliary drainage procedure triggered a massive hemobilia. Since endoscopic therapy was ineffective, a surgical mesocaval shunt with graft interposition and splenectomy was performed with favorable outcome. In selected cases, the mesocaval shunting plays an essential role in the treatment of portal cavernoma cholangiopathy even in the era of interventional radiology. PMID:27689206

  15. Straddle carrier radiation portal monitoring

    NASA Astrophysics Data System (ADS)

    Andersen, Eric S.; Samuel, Todd J.; Mullen, O. Dennis

    2005-05-01

    U.S. Customs and Border Protection (CBP) is the primary enforcement agency protecting the nation"s ports of entry. CBP is enhancing its capability to interdict the illicit import of nuclear and radiological materials and devices that may be used by terrorists. Pacific Northwest National Laboratory (PNNL) is providing scientific and technical support to CBP in their goal to enable rapid deployment of nuclear and radiation detection systems at U. S. ports of entry to monitor 100% of the incoming international traffic and cargo while not adversely impacting the operations or throughput of the ports. The U.S. ports of entry include the following vectors: land border crossings, seaports, airports, rail crossings, and mail and express consignment courier facilities. U.S. Customs and Border Protection (CBP) determined that a screening solution was needed for Seaport cargo containers being transported by Straddle Carriers (straddle carriers). A stationary Radiation Portal Monitor (RPM) for Straddle Carriers (SCRPM) is needed so that cargo containers can be scanned while in transit under a Straddle Carrier. The Straddle Carrier Portal operational impacts were minimized by conducting a time-motion study at the Port, and adaptation of a Remotely Operated RPM (RO-RPM) booth concept that uses logical lighting schemes for traffic control, cameras, Optical Character Recognition, and wireless technology.

  16. Araport: the Arabidopsis Information Portal

    PubMed Central

    Krishnakumar, Vivek; Hanlon, Matthew R.; Contrino, Sergio; Ferlanti, Erik S.; Karamycheva, Svetlana; Kim, Maria; Rosen, Benjamin D.; Cheng, Chia-Yi; Moreira, Walter; Mock, Stephen A.; Stubbs, Joseph; Sullivan, Julie M.; Krampis, Konstantinos; Miller, Jason R.; Micklem, Gos; Vaughn, Matthew; Town, Christopher D.

    2015-01-01

    The Arabidopsis Information Portal (https://www.araport.org) is a new online resource for plant biology research. It houses the Arabidopsis thaliana genome sequence and associated annotation. It was conceived as a framework that allows the research community to develop and release ‘modules’ that integrate, analyze and visualize Arabidopsis data that may reside at remote sites. The current implementation provides an indexed database of core genomic information. These data are made available through feature-rich web applications that provide search, data mining, and genome browser functionality, and also by bulk download and web services. Araport uses software from the InterMine and JBrowse projects to expose curated data from TAIR, GO, BAR, EBI, UniProt, PubMed and EPIC CoGe. The site also hosts ‘science apps,’ developed as prototypes for community modules that use dynamic web pages to present data obtained on-demand from third-party servers via RESTful web services. Designed for sustainability, the Arabidopsis Information Portal strategy exploits existing scientific computing infrastructure, adopts a practical mixture of data integration technologies and encourages collaborative enhancement of the resource by its user community. PMID:25414324

  17. Isocurvature constraints on portal couplings

    NASA Astrophysics Data System (ADS)

    Kainulainen, Kimmo; Nurmi, Sami; Tenkanen, Tommi; Tuominen, Kimmo; Vaskonen, Ville

    2016-06-01

    We consider portal models which are ultraweakly coupled with the Standard Model, and confront them with observational constraints on dark matter abundance and isocurvature perturbations. We assume the hidden sector to contain a real singlet scalar s and a sterile neutrino ψ coupled to s via a pseudoscalar Yukawa term. During inflation, a primordial condensate consisting of the singlet scalar s is generated, and its contribution to the isocurvature perturbations is imprinted onto the dark matter abundance. We compute the total dark matter abundance including the contributions from condensate decay and nonthermal production from the Standard Model sector. We then use the Planck limit on isocurvature perturbations to derive a novel constraint connecting dark matter mass and the singlet self coupling with the scale of inflation: mDM/GeV lesssim 0.2λs3/8 (H*/1011 GeV)‑3/2. This constraint is relevant in most portal models ultraweakly coupled with the Standard Model and containing light singlet scalar fields.

  18. Straddle Carrier Radiation Portal Monitoring

    SciTech Connect

    Andersen, Eric S.; Samuel, Todd J.; Mullen, O Dennis

    2005-08-01

    U.S. Customs and Border Protection (CBP) is the primary enforcement agency protecting the nation’s ports of entry. CBP is enhancing its capability to interdict the illicit import of nuclear and radiological materials and devices that may be used by terrorists. Pacific Northwest National Laboratory (PNNL) is providing scientific and technical support to CBP in their goal to enable rapid deployment of nuclear and radiation detection systems at U. S. ports of entry to monitor 100% of the incoming international traffic and cargo while not adversely impacting the operations or throughput of the ports. The U.S. ports of entry include the following vectors: land border crossings, seaports, airports, rail crossings, and mail and express consignment courier facilities. U.S. Customs and Border Protection (CBP) determined that a screening solution was needed for Seaport cargo containers being transported by Straddle Carriers (straddle carriers). A stationary Radiation Portal Monitor (RPM) for Straddle Carriers (SCRPM) is needed so that cargo containers can be scanned while in transit under a Straddle Carrier. The Straddle Carrier Portal operational impacts were minimized by conducting a time-motion study at the Port, and adaptation of a Remotely Operated RPM (RO-RPM) booth concept that uses logical lighting schemes for traffic control, cameras, Optical Character Recognition, and wireless technology.

  19. Collaboration using open standards and open source software (examples of DIAS/CEOS Water Portal)

    NASA Astrophysics Data System (ADS)

    Miura, S.; Sekioka, S.; Kuroiwa, K.; Kudo, Y.

    2015-12-01

    The DIAS/CEOS Water Portal is a part of the DIAS (Data Integration and Analysis System, http://www.editoria.u-tokyo.ac.jp/projects/dias/?locale=en_US) systems for data distribution for users including, but not limited to, scientists, decision makers and officers like river administrators. One of the functions of this portal is to enable one-stop search and access variable water related data archived multiple data centers located all over the world. This portal itself does not store data. Instead, according to requests made by users on the web page, it retrieves data from distributed data centers on-the-fly and lets them download and see rendered images/plots. Our system mainly relies on the open source software GI-cat (http://essi-lab.eu/do/view/GIcat) and open standards such as OGC-CSW, Opensearch and OPeNDAP protocol to enable the above functions. Details on how it works will be introduced during the presentation. Although some data centers have unique meta data format and/or data search protocols, our portal's brokering function enables users to search across various data centers at one time. And this portal is also connected to other data brokering systems, including GEOSS DAB (Discovery and Access Broker). As a result, users can search over thousands of datasets, millions of files at one time. Users can access the DIAS/CEOS Water Portal system at http://waterportal.ceos.org/.

  20. JPL Genesis and Rapid Intensification Processes (GRIP) Portal

    NASA Technical Reports Server (NTRS)

    Knosp, Brian W.; Li, P. Peggy; Vu, Quoc A.; Turk, Francis J.; Shen, Tsae-Pyng J.; Hristova-Veleva, Svetla M.; Licata, Stephen J.; Poulsen, William L.

    2012-01-01

    Satellite observations can play a very important role in airborne field campaigns, since they provide a comprehensive description of the environment that is essential for the experiment design, flight planning, and post-experiment scientific data analysis. In the past, it has been difficult to fully utilize data from multiple NASA satellites due to the large data volume, the complexity of accessing NASA s data in near-real-time (NRT), as well as the lack of software tools to interact with multi-sensor information. The JPL GRIP Portal is a Web portal that serves a comprehensive set of NRT observation data sets from NASA and NOAA satellites describing the atmospheric and oceanic environments related to the genesis and intensification of the tropical storms in the North Atlantic Ocean. Together with the model forecast data from four major global atmospheric models, this portal provides a useful tool for the scientists and forecasters in planning and monitoring the NASA GRIP field campaign during the 2010 Atlantic Ocean hurricane season. This portal uses the Google Earth plug-in to visualize various types of data sets, such as 2D maps, wind vectors, streamlines, 3D data sets presented at series of vertical cross-sections or pointwise vertical profiles, and hurricane best tracks and forecast tracks. Additionally, it allows users to overlap multiple data sets, change the opacity of each image layer, generate animations on the fly with selected data sets, and compare the observation data with the model forecast using two independent calendars. The portal also provides the capability to identify the geographic location of any point of interest. In addition to supporting the airborne mission planning, the NRT data and portal will serve as a very rich source of information during the post-field campaign analysis stage of the airborne experiment. By including a diverse set of satellite observations and model forecasts, it provides a good spatial and temporal context for the

  1. Monoclonal antibodies for copper-64 PET dosimetry and radioimmunotherapy

    PubMed Central

    Bryan, Jeffrey N; Jia, Fang; Mohsin, Huma; Sivaguru, Geethapriya; Anderson, Carolyn J; Miller, William H; Henry, Carolyn J

    2011-01-01

    Background We previously described a two-antibody model of 64Cu radioimmunotherapy to evaluate low-dose, solid-tumor response. This model was designed to test the hypothesis that cellular internalization is critical in causing tumor cell death by mechanisms in addition to radiation damage. The purpose of the present study was to estimate radiation dosimetry for both antibodies (mAbs) using positron emission tomography (PET) imaging and evaluate the effect of internalization on tumor growth. Results Dosimetry was similar between therapy groups. Median time to tumor progression to 1 g ranged from 7–12 days for control groups and was 32 days for both treatment groups (p < 0.0001). No statistically significant difference existed between any control group or between the treatment groups. Material and Methods In female nude mice bearing LS174T colon carcinoma xenografts, tumor dosimetry was calculated using serial PET images of three mice in each group of either internalizing 64Cu-labeled DOTA-cBR96 (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) or non-internalizing 64Cu-labeled DOTA-cT84.66 from 3 to 48 h. For the therapy study, controls (n = 10) received saline, DOTA-cBR96 or DOTA-cT84.66. Treatment animals (n = 9) received 0.890 mCi of 64Cu-labeled DOTA-cBR96 or 0.710 mCi of 64Cu-labeled DOTA-cT84.66. Tumors were measured daily. Conclusions PET imaging allows the use of 64Cu for pre-therapy calculation of tumor dosimetry. In spite of highly similar tumor dosimetry, an internalizing antibody did not improve the outcome of 64Cu radioimmunotherapy. Radio-resistance of this tumor cell line and copper efflux may have confounded the study. Further investigations of the therapeutic efficacy of 64Cu-labeled mAbs will focus on interaction between 64Cu and tumor suppressor genes and copper chaperones. PMID:21464612

  2. Dosimetry in Nuclear Medicine Diagnosis and Therapy

    NASA Astrophysics Data System (ADS)

    Noßke, D.; Mattsson, S.; Johansson, L.

    This document is part of Subvolume A 'Fundamentals and Data in Radiobiology, Radiation Biophysics, Dosimetry and Medical Radiological Protection' of Volume 7 'Medical Radiological Physics' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It contains the Section '4.7 Necessity of Patient-Specific Dose Planning in Radionuclide Therapy' of the Chapter '4 Dosimetry in Nuclear Medicine Diagnosis and Therapy'.

  3. 10 CFR 35.630 - Dosimetry equipment.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 1 2011-01-01 2011-01-01 false Dosimetry equipment. 35.630 Section 35.630 Energy NUCLEAR REGULATORY COMMISSION MEDICAL USE OF BYPRODUCT MATERIAL Photon Emitting Remote Afterloader Units, Teletherapy Units, and Gamma Stereotactic Radiosurgery Units § 35.630 Dosimetry equipment. (a) Except for low...

  4. 10 CFR 35.630 - Dosimetry equipment.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Dosimetry equipment. 35.630 Section 35.630 Energy NUCLEAR REGULATORY COMMISSION MEDICAL USE OF BYPRODUCT MATERIAL Photon Emitting Remote Afterloader Units, Teletherapy Units, and Gamma Stereotactic Radiosurgery Units § 35.630 Dosimetry equipment. (a) Except for low...

  5. 10 CFR 35.630 - Dosimetry equipment.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Dosimetry equipment. 35.630 Section 35.630 Energy NUCLEAR REGULATORY COMMISSION MEDICAL USE OF BYPRODUCT MATERIAL Photon Emitting Remote Afterloader Units, Teletherapy Units, and Gamma Stereotactic Radiosurgery Units § 35.630 Dosimetry equipment. (a) Except for low...

  6. 10 CFR 35.630 - Dosimetry equipment.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Dosimetry equipment. 35.630 Section 35.630 Energy NUCLEAR REGULATORY COMMISSION MEDICAL USE OF BYPRODUCT MATERIAL Photon Emitting Remote Afterloader Units, Teletherapy Units, and Gamma Stereotactic Radiosurgery Units § 35.630 Dosimetry equipment. (a) Except for low...

  7. 10 CFR 35.630 - Dosimetry equipment.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 1 2013-01-01 2013-01-01 false Dosimetry equipment. 35.630 Section 35.630 Energy NUCLEAR REGULATORY COMMISSION MEDICAL USE OF BYPRODUCT MATERIAL Photon Emitting Remote Afterloader Units, Teletherapy Units, and Gamma Stereotactic Radiosurgery Units § 35.630 Dosimetry equipment. (a) Except for low...

  8. Front-end electronics for the Muon Portal project

    NASA Astrophysics Data System (ADS)

    Garozzo, S.; Marano, D.; Bonanno, G.; Grillo, A.; Romeo, G.; Timpanaro, M. C.; Lo Presti, D.; Riggi, F.; Russo, V.; Bonanno, D.; La Rocca, P.; Longhitano, F.; Bongiovanni, D. G.; Fallica, G.; Valvo, G.

    2016-10-01

    The Muon Portal Project was born as a joint initiative between Italian research and industrial partners, aimed at the construction of a real-size working detector prototype to inspect the content of traveling containers by means of secondary cosmic-ray muon radiation and recognize potentially dangerous hidden materials. The tomographic image is obtained by reconstructing the incoming and outgoing muon trajectories when crossing the inspected volume, employing two tracker planes located above and below the container under inspection. In this paper, the design and development of the front-end electronics of the Muon Portal detector is presented, with particular emphasis being devoted to the photo-sensor devices detecting the scintillation light and to the read-out circuitry which is in charge of processing and digitizing the analog pulse signals. In addition, the remote control system, mechanical housing, and thermal cooling system of all structural blocks of the Muon Portal tracker are also discussed, demonstrating the effectiveness and functionality of the adopted design.

  9. Fundamentals of materials, techniques and instrumentation for OSL and FNTD dosimetry

    NASA Astrophysics Data System (ADS)

    Akselrod, M. S.

    2013-02-01

    The optically stimulated luminescence (OSL) technique has already become a successful commercial tool in personal radiation dosimetry, medical dosimetry, diagnostic imaging, geological and archeological dating. This review briefly describes the history and fundamental principles of OSL materials, methods and instrumentation. The advantages of OSL technology and instrumentation in comparison with thermoluminescent technique are analyzed. Progress in material and detector engineering has allowed new and promising developments regarding OSL applications in the medical field. Special attention is dedicated to Al2O3:C as a material of choice for many dosimetric applications including fiberoptic OSL/RL sensors with diameters as small as 300 μm. A new RL/OSL fiberoptic system has a high potential for in vivo and in vitro dosimetry in both radiation therapy and diagnostic mammography. Different aspects of instrumentation, data processing algorithms, post-irradiation and real-time measurements are described. The next technological breakthrough was done with Fluorescent Nuclear Track detectors (FNTD) that has some important advantages in measuring fast neutron and high energy heavy charge particles that became the latest tool in radiation therapy. New Mg-doped aluminum oxide crystals and novel type of imaging instrumentation for FNTD technology were engineered and successfully demonstrated for occupational and accident dosimetry, for medical dosimetry and radiobiological research.

  10. Evaluation of a glassless photographic film scanner for high-gradient radiochromic film dosimetry.

    PubMed

    De Puysseleyr, A; Srivastava, R P; Paelinck, L; De Neve, W; De Wagter, C

    2012-01-01

    This study evaluates the performance of the Nikon Coolscan 9000 ED film scanner for high-gradient radiochromic film dosimetry. As a reference for comparison, analogue experiments were performed on the Epson Expression 10000XL flatbed scanner. Based on these results, a dosimetric protocol was established for the Nikon scanner and its overall performance for high-gradient dosimetry was evaluated. The Nikon scanner demonstrated a high sensitivity for radiochromic film dosimetry, resulting in more contrast in the digitized image. The scanner's optics also demonstrated excellent stability and did not necessitate warm-up scans prior to data acquisition. Moreover, negative effects of temperature changes of the film inside the scanner were shown to be limited. None of the digitized images showed significant disturbances by moiré-patterns, by virtue of the absence of a glass plate for film positioning. However, scanner response was found to vary considerably across the reading area, requiring an optical density-dependent correction procedure to be incorporated into the scanning protocol. The main limitation of the Nikon Coolscan 9000 ED transmission scanner remains its film size restriction to 6.2 × 20 cm2. Nevertheless, its excellent characteristics render it the preferential tool for high-gradient radiochromic film dosimetry in applications limited to small film sizes, such as dosimetry in the build-up region.

  11. Tumor dosimetry in radioimmunotherapy: Methods of calculation for beta particles

    SciTech Connect

    Leichner, P.K. ); Kwok, C.S. )

    1993-03-01

    Calculational methods of beta-particle dosimetry in radioimmunotherapy (RIT) are reviewed for clinical and experimental studies and computer modeling of tumors. In clinical studies, absorbed-dose estimates are usually based on the [ital in]-[ital vivo] quantitation of the activity in tumors from gamma camera images. Because of the limited spatial resolution of gamma cameras, clinical dosimetry is necessarily limited to the macroscopic level (macrodosimetry) and the MIRD formalism for absorbed-dose calculations is appropriate. In experimental RIT, tumor dimensions are often comparable to or smaller than the beta-particle range of commonly used radionuclides (for example, [sup 131]I, [sup 67]Cu, [sup 186]Re, [sup 188]Re, [sup 90]Y) and deviations from the equilibrium dose must be taken into account in absorbed-dose calculations. Additionally, if small tumors are growing rapidly at the time of RIT, the effects of tumor growth will need to be included in absorbed-dose estimates. In computer modeling of absorbed-dose distributions, analytical, numerical, and Monte Carlo methods have been used to investigate the consequences of uniform and nonuniform activity distributions and the effects of inhomogeneous media. Measurements and calculations of the local absorbed dose at the multicellular level have shown that variations in this dose are large. Knowledge of the absorbed dose is essential for any form of radiotherapy. Therefore, it is important that clinical, experimental, and theoretical investigations continue to provide information on tumor dosimetry that is necessary for a better understanding of the radiobiological effects of RIT.

  12. Radon Dosimetry and Monitoring in Mines

    NASA Astrophysics Data System (ADS)

    Pineau, J. F.

    The following sections are included: * Introduction * The Atmosphere in Underground Mines * Origin of the radioactivity of the atmosphere in underground mines * Main characteristics of the atmosphere of mines * Temperature * Relative humidity * Particle size distribution of the aerosols * Volume concentration of radon * Age of the ventilation air * Volume concentration of radon decay products * Volume concentration of long-lived aerosols (LLA) * Order of magnitude of the volume concentrations to be measured * Dosimetry: Application to Miners * Dosimetry of miners in France * Integrated dosimetry system * Measuring head * Unit for the detection and measurement of exposure to potential alpha energy * Treatment and reading of the detector films * Expression of the results * Other examples of operational dosimetry * Use of closed passive dosimeters for the dosimetry of miners * Monitoring of Physical Parameters of the Atmospheres * Qualification of non-uranium mines * Monitoring of the environment of mining sites * Optimisation of radiation protection using the dosimetric data * Concluding Remarks * References

  13. Source position verification and dosimetry in HDR brachytherapy using an EPID

    SciTech Connect

    Smith, R. L.; Taylor, M. L.; McDermott, L. N.; Franich, R. D.; Haworth, A.; Millar, J. L.

    2013-11-15

    Purpose: Accurate treatment delivery in high dose rate (HDR) brachytherapy requires correct source dwell positions and dwell times to be administered relative to each other and to the surrounding anatomy. Treatment delivery inaccuracies predominantly occur for two reasons: (i) anatomical movement or (ii) as a result of human errors that are usually related to incorrect implementation of the planned treatment. Electronic portal imaging devices (EPIDs) were originally developed for patient position verification in external beam radiotherapy and their application has been extended to provide dosimetric information. The authors have characterized the response of an EPID for use with an {sup 192}Ir brachytherapy source to demonstrate its use as a verification device, providing both source position and dosimetric information.Methods: Characterization of the EPID response using an {sup 192}Ir brachytherapy source included investigations of reproducibility, linearity with dose rate, photon energy dependence, and charge build-up effects associated with exposure time and image acquisition time. Source position resolution in three dimensions was determined. To illustrate treatment verification, a simple treatment plan was delivered to a phantom and the measured EPID dose distribution compared with the planned dose.Results: The mean absolute source position error in the plane parallel to the EPID, for dwells measured at 50, 100, and 150 mm source to detector distances (SDD), was determined to be 0.26 mm. The resolution of the z coordinate (perpendicular distance from detector plane) is SDD dependent with 95% confidence intervals of ±0.1, ±0.5, and ±2.0 mm at SDDs of 50, 100, and 150 mm, respectively. The response of the EPID is highly linear to dose rate. The EPID exhibits an over-response to low energy incident photons and this nonlinearity is incorporated into the dose calibration procedure. A distance (spectral) dependent dose rate calibration procedure has been

  14. Insight into congenital absence of the portal vein: Is it rare?

    PubMed Central

    Shen, Guo-Hua Hu‚ Lai-Gen; Zhu, Jin Yang‚ Jin-Hua Mei‚ Yue-Feng

    2008-01-01

    Congenital absence of portal vein (CAPV) was a rare event in the past. However, the number of detected CAPV cases has increased in recent years because of advances in imaging techniques. Patients with CAPV present with portal hypertension (PH) or porto-systemic encephalopathy (PSE), but these conditions rarely occur until the patients grow up or become old. The patients usually visit doctors for the complications of venous shunts, hepatic or cardiac abnormalities detected by ultrasonography (US), computed tomography (CT) and magnetic resonance imaging (MRI). The etiology of this disease is not clear, but most investigators consider that it is associated with abnormal embryologic development of the portal vein. Usually, surgical intervention can relieve the symptoms and prevent occurrence of complications in CAPV patients. Moreover, its management should be stressed on a case-by-case basis, depending on the type or anatomy of the disease, as well as the symptoms and clinical conditions of the patient. PMID:18932274

  15. Portal vein aneurysm: What to know.

    PubMed

    Laurenzi, Andrea; Ettorre, Giuseppe Maria; Lionetti, Raffaella; Meniconi, Roberto Luca; Colasanti, Marco; Vennarecci, Giovanni

    2015-11-01

    Portal vein aneurysm is an unusual vascular dilatation of the portal vein, which was first described by Barzilai and Kleckner in 1956 and since then less than 200 cases have been reported. The aim of this article is to provide an overview of the international literature to better clarify various aspects of this rare nosological entity and provide clear evidence-based summary, when available, of the clinical and surgical management. A systematic literature search of the Pubmed database was performed for all articles related to portal vein aneurysm. All articles published from 1956 to 2014 were examined for a total of 96 reports, including 190 patients. Portal vein aneurysm is defined as a portal vein diameter exceeding 1.9 cm in cirrhotic patients and 1.5 cm in normal livers. It can be congenital or acquired and portal hypertension represents the main cause of the acquired version. Surgical indication is considered in case of rupture, thrombosis or symptomatic aneurysms. Aneurysmectomy and aneurysmorrhaphy are considered in patients with normal liver, while shunt procedures or liver transplantation are the treatment of choice in case of portal hypertension. Being such a rare vascular entity its management should be reserved to high-volume tertiary hepato-biliary centres. PMID:26188840

  16. BSD Portals for LINUX 2.0

    NASA Technical Reports Server (NTRS)

    McNab, A. David; woo, Alex (Technical Monitor)

    1999-01-01

    Portals, an experimental feature of 4.4BSD, extend the file system name space by exporting certain open () requests to a user-space daemon. A portal daemon is mounted into the file name space as if it were a standard file system. When the kernel resolves a pathname and encounters a portal mount point, the remainder of the path is passed to the portal daemon. Depending on the portal "pathname" and the daemon's configuration, some type of open (2) is performed. The resulting file descriptor is passed back to the kernel which eventually returns it to the user, to whom it appears that a "normal" open has occurred. A proxy portalfs file system is responsible for kernel interaction with the daemon. The overall effect is that the portal daemon performs an open (2) on behalf of the kernel, possibly hiding substantial complexity from the calling process. One particularly useful application is implementing a connection service that allows simple scripts to open network sockets. This paper describes the implementation of portals for LINUX 2.0.

  17. Prototype Neutron Portal Monitor Detector

    NASA Astrophysics Data System (ADS)

    Schier, W.

    2014-05-01

    A very large drum-shaped neutron detector which could replace the 3He neutron portal monitor detector is under development. Detection is based on the 6Li(n,3H)4He reaction. 6Li metal is evaporated onto aluminum plates then covered with 22-cm x 27-cm ZnS(Ag) scintillation sheets and sealed about the edges. The equivalent of 40 detector plates will be arrayed in the 80-cm diameter drum housing and viewed by a single 20-cm diameter hemispherical photomultiplier tube without the use of light guides. Presently 25 detector plates are installed. Light collection tests are performed with a bare 210Po alpha source on a ZnS(Ag) disk. Neutron detection studies include neutrons from a 2-curie PuBe source and from a 0.255-gram 240Pu source.

  18. The Astrostatistics and Astroinformatics Portal

    NASA Astrophysics Data System (ADS)

    Feigelson, Eric; Hilbe, J. M.

    2014-01-01

    The Astrostatistics and Astroinformatics Portal (ASAIP, http://asaip.psu.edu) is a Web resource started in 2012 to foster research into advanced methodologies for astronomical research, and to promulgate such methods into the broader astronomy community. It provides searchable abstracts to Recent Papers in the field, several discussion Forums, various resources for researchers, brief Articles by experts, lists of Meetings, and access to various Web resources such as on-line courses, books and blogs. The material can be electronically searched. The site will be used for public outreach by organizations associated with the AAS, IAU, ISI (International Statistical Institute), and LSST. ASAIP has nearly 700 members who can contribute material, and its resources are readable by the general Web public. This presentation gives examples of recent ASAIP entries and encourages AAS members to use its resources.

  19. Freeze-in through portals

    SciTech Connect

    Blennow, Mattias; Fernandez-Martínez, Enrique; Zaldívar, Bryan E-mail: enrique.fernandez-martinez@uam.es

    2014-01-01

    The popular freeze-out paradigm for Dark Matter (DM) production, relies on DM-baryon couplings of the order of the weak interactions. However, different search strategies for DM have failed to provide a conclusive evidence of such (non-gravitational) interactions, while greatly reducing the parameter space of many representative models. This motivates the study of alternative mechanisms for DM genesis. In the freeze-in framework, the DM is slowly populated from the thermal bath while never reaching equilibrium. In this work, we analyse in detail the possibility of producing a frozen-in DM via a mediator particle which acts as a portal. We give analytical estimates of different freeze-in regimes and support them with full numerical analyses, taking into account the proper distribution functions of bath particles. Finally, we constrain the parameter space of generic models by requiring agreement with DM relic abundance observations.

  20. The future of medical dosimetry.

    PubMed

    Adams, Robert D

    2015-01-01

    The world of health care delivery is becoming increasingly complex. The purpose of this manuscript is to analyze current metrics and analytically predict future practices and principles of medical dosimetry. The results indicate five potential areas precipitating change factors: a) evolutionary and revolutionary thinking processes, b) social factors, c) economic factors, d) political factors, and e) technological factors. Outcomes indicate that significant changes will occur in the job structure and content of being a practicing medical dosimetrist. Discussion indicates potential variables that can occur within each process and change factor and how the predicted outcomes can deviate from normative values. Finally, based on predicted outcomes, future opportunities for medical dosimetrists are given.

  1. Solid-State Personal Dosimetry

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Fralick, Gustave C.; Wrbanek, Susan Y.

    2005-01-01

    This document is a web site page, and a data sheet about Personal protection (i.e., space suits) presented to the Radiation and Micrometeoroid Mitigation Technology Focus Group meeting. The website describes the work of the PI to improve solid state personal radiation dosimetry. The data sheet presents work on the active personal radiation detection system that is to provide real-time local radiation exposure information during EVA. Should undue exposure occur, knowledge of the dynamic intensity conditions during the exposure will allow more precise diagnostic assessment of the potential health risk to the exposed individual.

  2. The Future of Medical Dosimetry

    SciTech Connect

    Adams, Robert D.

    2015-07-01

    The world of health care delivery is becoming increasingly complex. The purpose of this manuscript is to analyze current metrics and analytically predict future practices and principles of medical dosimetry. The results indicate five potential areas precipitating change factors: a) evolutionary and revolutionary thinking processes, b) social factors, c) economic factors, d) political factors, and e) technological factors. Outcomes indicate that significant changes will occur in the job structure and content of being a practicing medical dosimetrist. Discussion indicates potential variables that can occur within each process and change factor and how the predicted outcomes can deviate from normative values. Finally, based on predicted outcomes, future opportunities for medical dosimetrists are given.

  3. Zolmitriptan: A Novel Portal Hypotensive Agent Which Synergizes with Propranolol in Lowering Portal Pressure

    PubMed Central

    Reboredo, Mercedes; Chang, Haisul C. Y.; Barbero, Roberto; Rodríguez-Ortigosa, Carlos M.; Pérez-Vizcaíno, Francisco; Morán, Asunción; García, Mónica; Banales, Jesús M.; Carreño, Norberto; Alegre, Félix; Herrero, Ignacio; Quiroga, Jorge

    2013-01-01

    Objective Only a limited proportion of patients needing pharmacological control of portal hypertension are hemodynamic responders to propranolol. Here we analyzed the effects of zolmitriptan on portal pressure and its potential interaction with propranolol. Methods Zolmitriptan, propranolol or both were tested in two rat models of portal hypertension: common bile duct ligation (CBDL) and CCl4-induced cirrhosis. In these animals we measured different hemodynamic parameters including portal venous pressure, arterial renal flow, portal blood flow and cardiac output. We also studied the changes in superior mesenteric artery perfusion pressure and in arterial wall cAMP levels induced by zolmitriptan, propranolol or both. Moreover, we determined the effect of splanchnic sympathectomy on the response of PVP to zolmitriptan. Results In both models of portal hypertension zolmitriptan induced a dose-dependent transient descent of portal pressure accompanied by reduction of portal flow with only slight decrease in renal flow. In cirrhotic rats, splanchnic sympathectomy intensified and prolonged zolmitriptan-induced portal pressure descent. Also, propranolol caused more intense and durable portal pressure fall when combined with zolmitriptan. Mesenteric artery perfusion pressure peaked for about 1 min upon zolmitriptan administration but showed no change with propranolol. However propranolol enhanced and prolonged the elevation in mesenteric artery perfusion pressure induced by zolmitriptan. In vitro studies showed that propranolol prevented the inhibitory effects of β2-agonists on zolmitriptan-induced vasoconstriction and the combination of propranolol and zolmitriptan significantly reduced the elevation of cAMP caused by β2-agonists. Conclusion Zolmitriptan reduces portal hypertension and non-selective beta-blockers can improve this effect. Combination therapy deserves consideration for patients with portal hypertension failing to respond to non-selective beta

  4. The Collaborative Information Portal and NASA's Mars Exploration Rover Mission

    NASA Technical Reports Server (NTRS)

    Mak, Ronald; Walton, Joan

    2005-01-01

    The Collaborative Information Portal was enterprise software developed jointly by the NASA Ames Research Center and the Jet Propulsion Laboratory for NASA's Mars Exploration Rover mission. Mission managers, engineers, scientists, and researchers used this Internet application to view current staffing and event schedules, download data and image files generated by the rovers, receive broadcast messages, and get accurate times in various Mars and Earth time zones. This article describes the features, architecture, and implementation of this software, and concludes with lessons we learned from its deployment and a look towards future missions.

  5. The GB/3D Type Fossils Online Web Portal

    NASA Astrophysics Data System (ADS)

    McCormick, T.; Howe, M. P.

    2013-12-01

    Fossils are the remains of once-living organisms that existed and played out their lives in 3-dimensional environments. The information content provided by a 3d representation of a fossil is much greater than that provided by a traditional photograph, and can grab the attention and imagination of the younger and older general public alike. The British Geological Survey has been leading a consortium of UK natural history museums including the Oxford University Museum of Natural History, the Sedgwick Museum Cambridge, the National Museum of Wales Cardiff, and a number of smaller regional British museums to construct a web portal giving access to metadata, high resolution images and interactive 3d models of type fossils from the UK. The web portal at www.3d-fossils.ac.uk was officially launched in August 2013. It can be used to discover metadata describing the provenance, taxonomy, and stratigraphy of the specimens. Zoom-able high resolution digital photographs are available, including for many specimens ';anaglyph' stereo images that can be viewed in 3d using red-cyan stereo spectacles. For many of the specimens interactive 3d models were generated by scanning with portable ';NextEngine 3D HD' 3d scanners. These models can be downloaded in zipped .OBJ and .PLY format from the web portal, or may be viewed and manipulated directly in certain web browsers. The images and scans may be freely downloaded subject to a Creative Commons Attribution ShareAlike Non-Commercial license. There is a simple application programming interface (API) allowing metadata to be downloaded, with links to the images and models, in a standardised format for use in data mash-ups and third party applications. The web portal also hosts ';open educational resources' explaining the process of fossilization and the importance of type specimens in taxonomy, as well as providing introductions to the most important fossil groups. We have experimented with using a 3d printer to create replicas of the

  6. [Idiopathic non-cirrhotic portal hypertension: An update].

    PubMed

    Bissonnette, Julien; Rautou, Pierre-Emmanuel; Valla, Dominique-Charles

    2015-10-01

    Idiopathic non-cirrhotic portal hypertension is an under-estimated cause of portal hypertension. The diagnosis requires the exclusion of cirrhosis, common causes of chronic liver disease and venous obstruction of the portal and hepatic veins. It has been associated with various extra-hepatic conditions that are most frequently immunologic, prothrombotic, hematologic and toxic. The most frequent clinical complications are variceal hemorrhage and portal vein thrombosis. Complications of portal hypertension should be managed as in patients with cirrhosis. PMID:26362514

  7. Advances in radiation therapy dosimetry

    PubMed Central

    Paliwal, Bhudatt; Tewatia, Dinesh

    2009-01-01

    During the last decade, there has been an explosion of new radiation therapy planning and delivery tools. We went through a rapid transition from conventional three-dimensional (3D) conformal radiation therapy to intensity-modulated radiation therapy (IMRT) treatments, and additional new techniques for motion-adaptive radiation therapy are being introduced. These advances push the frontiers in our effort to provide better patient care; and with the addition of IMRT, temporal dimensions are major challenges for the radiotherapy patient dosimetry and delivery verification. Advanced techniques are less tolerant to poor implementation than are standard techniques. Mis-administrations are more difficult to detect and can possibly lead to poor outcomes for some patients. Instead of presenting a manual on quality assurance for radiation therapy, this manuscript provides an overview of dosimetry verification tools and a focused discussion on breath holding, respiratory gating and the applications of four-dimensional computed tomography in motion management. Some of the major challenges in the above areas are discussed. PMID:20098555

  8. The Fukushima Daiichi Accident Study Information Portal

    SciTech Connect

    Shawn St. Germain; Curtis Smith; David Schwieder; Cherie Phelan

    2012-11-01

    This paper presents a description of The Fukushima Daiichi Accident Study Information Portal. The Information Portal was created by the Idaho National Laboratory as part of joint NRC and DOE project to assess the severe accident modeling capability of the MELCOR analysis code. The Fukushima Daiichi Accident Study Information Portal was created to collect, store, retrieve and validate information and data for use in reconstructing the Fukushima Daiichi accident. In addition to supporting the MELCOR simulations, the Portal will be the main DOE repository for all data, studies and reports related to the accident at the Fukushima Daiichi nuclear power station. The data is stored in a secured (password protected and encrypted) repository that is searchable and accessible to researchers at diverse locations.

  9. Single Portal Knee Arthroscopy: 2015 Technique Update

    PubMed Central

    Cooper, Daniel E.

    2016-01-01

    A technique of single portal knee arthroscopy was reported in 2013. Using a parallel working cannula assembled to the arthroscope cannula, the instruments are passed into the joint in line with the arthroscope. The original technique video in Arthroscopy Techniques shows the use of a 25 mm tube assembly with a parallel portal through which biters and proximally bent cutter instruments are used to perform procedures in the knee. This 2015 technical update shows the current preferred and most versatile method of single portal knee arthroscopy using a parallel locking and rotating hub for passage of biters and double-bend cutters. The video shows adequate completion of a partial meniscectomy using only 1 portal. PMID:27073772

  10. Single Portal Knee Arthroscopy: 2015 Technique Update.

    PubMed

    Cooper, Daniel E

    2016-02-01

    A technique of single portal knee arthroscopy was reported in 2013. Using a parallel working cannula assembled to the arthroscope cannula, the instruments are passed into the joint in line with the arthroscope. The original technique video in Arthroscopy Techniques shows the use of a 25 mm tube assembly with a parallel portal through which biters and proximally bent cutter instruments are used to perform procedures in the knee. This 2015 technical update shows the current preferred and most versatile method of single portal knee arthroscopy using a parallel locking and rotating hub for passage of biters and double-bend cutters. The video shows adequate completion of a partial meniscectomy using only 1 portal.

  11. 23. INCLINED END POST / VERTICAL / DIAGONAL / PORTAL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. INCLINED END POST / VERTICAL / DIAGONAL / PORTAL BRACING DETAIL. VIEW TO SOUTHEAST. - Abraham Lincoln Memorial Bridge, Spanning Missouri River on Highway 30 between Nebraska & Iowa, Blair, Washington County, NE

  12. Use of radiochromic dosimetry film for HDR brachytherapy quality assurance.

    PubMed

    Steidley, K D

    1998-01-01

    An important quality assurance (QA) procedure in high dose rate (HDR) remote afterloading brachytherapy is the verification of the system's control of the source by a direct test with dosimetry medium prior to the patient's first treatment. In this test radiochromic film is placed in direct contact with the applicator and the patient's proposed treatment is then run with their EPROM card. Examination of the film allows a quick appraisal of step size, number of steps, and offset. Advantages of this film include self-development so the image may be viewed immediately, insensitivity to normal room light, and archivability. The cost is about U.S. $2 per clinical case.

  13. Idiopathic Noncirrhotic Portal Hypertension: An Appraisal

    PubMed Central

    Lee, Hwajeong; Rehman, Aseeb Ur; Fiel, M. Isabel

    2016-01-01

    Idiopathic noncirrhotic portal hypertension is a poorly defined clinical condition of unknown etiology. Patients present with signs and symptoms of portal hypertension without evidence of cirrhosis. The disease course appears to be indolent and benign with an overall better outcome than cirrhosis, as long as the complications of portal hypertension are properly managed. This condition has been recognized in different parts of the world in diverse ethnic groups with variable risk factors, resulting in numerous terminologies and lack of standardized diagnostic criteria. Therefore, although the diagnosis of idiopathic noncirrhotic portal hypertension requires clinical exclusion of other conditions that can cause portal hypertension and histopathologic confirmation, this entity is under-recognized clinically as well as pathologically. Recent studies have demonstrated that variable histopathologic entities with different terms likely represent a histologic spectrum of a single entity of which obliterative portal venopathy might be an underlying pathogenesis. This perception calls for standardization of the nomenclature and formulation of widely accepted diagnostic criteria, which will facilitate easier recognition of this disorder and will highlight awareness of this entity. PMID:26563701

  14. Calibration facility for environment dosimetry instruments

    SciTech Connect

    Bercea, Sorin; Celarel, Aurelia; Cenusa, Constantin

    2013-12-16

    In the last ten years, the nuclear activities, as well as the major nuclear events (see Fukushima accident) had an increasing impact on the environment, merely by contamination with radioactive materials. The most conferment way to quickly identify the presence of some radioactive elements in the environment, is to measure the dose-equivalent rate H. In this situation, information concerning the values of H due only to the natural radiation background must exist. Usually, the values of H due to the natural radiation background, are very low (∼10{sup −9} - 10{sup −8} Sv/h). A correct measurement of H in this range involve a performing calibration of the measuring instruments in the measuring range corresponding to the natural radiation background lead to important problems due to the presence of the natural background itself the best way to overlap this difficulty is to set up the calibration stand in an area with very low natural radiation background. In Romania, we identified an area with such special conditions at 200 m dept, in a salt mine. This paper deals with the necessary requirements for such a calibration facility, as well as with the calibration stand itself. The paper includes also, a description of the calibration stand (and images) as well as the radiological and metrological parameters. This calibration facilities for environment dosimetry is one of the few laboratories in this field in Europe.

  15. Calibration facility for environment dosimetry instruments

    NASA Astrophysics Data System (ADS)

    Bercea, Sorin; Celarel, Aurelia; Cenusa, Constantin

    2013-12-01

    In the last ten years, the nuclear activities, as well as the major nuclear events (see Fukushima accident) had an increasing impact on the environment, merely by contamination with radioactive materials. The most conferment way to quickly identify the presence of some radioactive elements in the environment, is to measure the dose-equivalent rate H. In this situation, information concerning the values of H due only to the natural radiation background must exist. Usually, the values of H due to the natural radiation background, are very low (˜10-9 - 10-8 Sv/h). A correct measurement of H in this range involve a performing calibration of the measuring instruments in the measuring range corresponding to the natural radiation background lead to important problems due to the presence of the natural background itself the best way to overlap this difficulty is to set up the calibration stand in an area with very low natural radiation background. In Romania, we identified an area with such special conditions at 200 m dept, in a salt mine. This paper deals with the necessary requirements for such a calibration facility, as well as with the calibration stand itself. The paper includes also, a description of the calibration stand (and images) as well as the radiological and metrological parameters. This calibration facilities for environment dosimetry is one of the few laboratories in this field in Europe.

  16. Dosimetry of in situ activated dysprosium microspheres.

    PubMed

    Adnani, N

    2004-03-01

    This paper presents the results of a study aimed at investigating the dosimetry of stable dysprosium microspheres activated, in situ, by a linac generated photon beam. In phantom measurements of the neutron flux within an 18 MV photon beam were performed using CR-39 detectors and gold activation. The results were used in conjunction with a Monte Carlo computer simulation to investigate the dose distribution resulting from the activation of dysprosium (Dy) microspheres using an 18 MV photon beam. Different depths, lesion volumes and volume concentrations of microspheres are investigated. The linac lower collimator jaws are assumed completely closed to shield the tumour volume from the photon dose. Using a single AP field with 0 x 0 cm2 field size (closed jaws), a photon dose rate of 600 MU min(-1) and 80 cm SSD for 10 min, an average dose exceeding 1 Gy can be delivered to spherical lesions of 0.5 cm and higher diameter. The variation of the average dose with the size of the lesion reaches saturation for tumour volumes exceeding 1 cm in diameter. This report shows that the photon beam of a high-energy linac can be used to activate Dy microspheres in situ and, as a result, deliver a significant dose of beta radiation. Non-radioactive Dy microspheres do not have the toxicity and imaging problems associated with commercially available yttrium-90 based products. PMID:15070199

  17. Improved dosimetry techniques for intravascular brachytherapy

    NASA Astrophysics Data System (ADS)

    Sehgal, Varun

    using Monte Carlo-based radiation transport code MCNP and tabulated for a range of different coronary geometries and different radionuclides. A new technique using imaging techniques such as intravascular ultrasound and angiography to assess dosimetry for realistic coronary arteries is also introduced. The results indicate the need for accurate assessment of post-intervention clinical measurements such as minimal lumen diameter and residual plaque burden and incorporating them into dose calculations.

  18. EPID based in vivo dosimetry system: clinical experience and results.

    PubMed

    Celi, Sofia; Costa, Emilie; Wessels, Claas; Mazal, Alejandro; Fourquet, Alain; Francois, Pascal

    2016-01-01

    Mandatory in several countries, in vivo dosimetry has been recognized as one of the next milestones in radiation oncology. Our department has implemented clinically an EPID based in vivo dosimetry system, EPIgray, by DOSISOFT S.A., since 2006. An analysis of the measurements per linac and energy over a two-year period was performed, which included a more detailed examination per technique and treat-ment site over a six-month period. A comparison of the treatment planning system doses and the doses estimated by EPIgray shows a mean of the differences of 1.9% (± 5.2%) for the two-year period. The 3D conformal treatment plans had a mean dose difference of 2.0% (± 4.9%), while for intensity-modulated radiotherapy and volumetric-modulated arc therapy treatments the mean dose difference was -3.0 (± 5.3%) and -2.5 (± 5.2%), respectively. In addition, root cause analyses were conducted on the in vivo dosimetry measurements of two breast cancer treatment techniques, as well as prostate treatments with intensity-modulated radiotherapy and volumetric-modulated arc therapy. During the breast study, the dose differences of breast treatments in supine position were correlated to patient setup and EPID positioning errors. Based on these observations, an automatic image shift correc-tion algorithm is developed by DOSIsoft S.A. The prostate study revealed that beams and arcs with out-of-tolerance in vivo dosimetry results tend to have more complex modulation and a lower exposure of the points of interest. The statistical studies indicate that in vivo dosimetry with EPIgray has been successfully imple-mented for classical and complex techniques in clinical routine at our institution. The additional breast and prostate studies exhibit the prospects of EPIgray as an easy supplementary quality assurance tool. The validation, the automatization, and the reduction of false-positive results represent an important step toward adaptive radiotherapy with EPIgray. PMID:27167283

  19. The Portal to the Universe: A Comprehensive Gateway to What's New in Astronomy

    NASA Astrophysics Data System (ADS)

    Christensen, L. L.; Gay, P.

    2008-11-01

    One of the greatest difficulties in astronomy is staying current. On any given day, half a dozen or more press releases may announce the latest discoveries of the professional astronomy community, while blogs and forums are alive with the latest sky events and news that has not yet made it to peer reviewed publications. To help bring all this content together, the Portal to the Universe is being built as a central aggregator of astronomy online content, including press releases, blogs, podcasts, image feeds and widgets. The Portal to the Universe is a Cornerstone project under the International Year of Astronomy 2009.

  20. A probabilistic gastrointestinal tract dosimetry model

    NASA Astrophysics Data System (ADS)

    Huh, Chulhaeng

    In internal dosimetry, the tissues of the gastrointestinal (GI) tract represent one of the most radiosensitive organs of the body with the hematopoietic bone marrow. Endoscopic ultrasound is a unique tool to acquire in-vivo data on GI tract wall thicknesses of sufficient resolution needed in radiation dosimetry studies. Through their different echo texture and intensity, five layers of differing echo patterns for superficial mucosa, deep mucosa, submucosa, muscularis propria and serosa exist within the walls of organs composing the alimentary tract. Thicknesses for stomach mucosa ranged from 620 +/- 150 mum to 1320 +/- 80 mum (total stomach wall thicknesses from 2.56 +/- 0.12 to 4.12 +/- 0.11 mm). Measurements made for the rectal images revealed rectal mucosal thicknesses from 150 +/- 90 mum to 670 +/- 110 mum (total rectal wall thicknesses from 2.01 +/- 0.06 to 3.35 +/- 0.46 mm). The mucosa thus accounted for 28 +/- 3% and 16 +/- 6% of the total thickness of the stomach and rectal wall, respectively. Radiation transport simulations were then performed using the Monte Carlo N-particle transport code (MCNP) 4C transport code to calculate S values (Gy/Bq-s) for penetrating and nonpenetrating radiations such as photons, beta particles, conversion electrons and auger electrons of selected nuclides, I123, I131, Tc 99m and Y90 under two source conditions: content and mucosa sources, respectively. The results of this study demonstrate generally good agreement with published data for the stomach mucosa wall. The rectal mucosa data are consistently higher than published data compared with the large intestine due to different radiosensitive cell thicknesses (350 mum vs. a range spanning from 149 mum to 729 mum) and different geometry when a rectal content source is considered. Generally, the ICRP models have been designed to predict the amount of radiation dose in the human body from a "typical" or "reference" individual in a given population. The study has been performed to

  1. A National project for in vivo dosimetry procedures in radiotherapy: First results

    NASA Astrophysics Data System (ADS)

    Piermattei, Angelo; Greco, Francesca; Azario, Luigi; Porcelli, Andrea; Cilla, Savino; Zucca, Sergio; Russo, Aniello; di Castro, Elisabetta; Russo, Mariateresa; Caivano, Rocchina; Fusco, Vincenzo; Morganti, Alessio; Fidanzio, Andrea

    2012-03-01

    The paper reports the results of a National project financed by the Istituto Nazionale di Fisica Nucleare (INFN) for the development of in vivo dosimetric procedures in radiotherapy. In particular, a generalized procedure for the in vivo reconstruction of the isocenter dose, Diso, has been developed for 3D conformal radiotherapy treatments with open and wedged X-ray beams supplied by linacs of different manufacturers and equipped with aSi Electronic Portal Imaging Devices (EPIDs). In this way, the commissioning procedure is very simplified and applicable to Elekta, Siemens and Varian linacs. The method here reported is based on measurements in solid-water phantoms of different thicknesses, w, irradiated by square field sizes, L. Generalized mid-plane doses, D0, and transit signal by EPIDs, st0, obtained by 19 open and 38 wedged beams of 8 different linacs, were determined taking into account X-ray beam and EPID calibrations. Generalized ratios F0 = st0/D0 for open and wedged beams were fitted by surface equations and used by a dedicated software, for the Diso reconstruction. Moreover, for each beam the software supplied a set of transit signal profiles crossing the beam central axis to test the beam irradiation reproducibility. The tolerance level of the comparison between the Diso and the dose computed by the TPS, Diso,TPS, was estimated 5%. The generalized in vivo dosimetry procedure was adopted by 3 centers that used different linacs. The results of 480 tests showed that in absence of errors, the comparison between Diso and Diso,TPS resulted well-within the tolerance level. The presence of errors was detected in 10% of the tests and were due to essentially an incorrect set-up, presence of an attenuator on the beams and patient morphological changes. Moreover, the dedicated software used the information of the Record and Verify system of the centres and consequently the extra-time needed to obtain, for each beam, the Diso reconstruction after the dose delivery

  2. Digital Earth Portals to DLESE

    NASA Astrophysics Data System (ADS)

    Raskin, R.

    2001-05-01

    Digital Earth offers the promise to push the envelope of accessibility and usability of georeferenced digital data and reach out to non-traditional users. To realize this promise within the context of an educational digital library, the library can take advantage of existing Digital Earth components: viewers, catalogs, and data products - all of which conform to emerging open standards. Viewers vary in level of sophistication from standard web browsers to immersive or 3-D visualization tools. Datasets are currently the limiting ingredient in the mix, as providers must make data available using the open standards. However, the Earth Science Information Partnership (ESIP) Federation has developed a Digital Earth Cluster to insure that its members provide a source of compliant data products within a short time frame. A Digital Earth portal integrates all of the above components and provides the look and feel appropriate to the target educational level and classroom interests. DLESE is currently developing such an early prototype using existing components that can be used as a model for future development. A live demonstration will show the use of a Digital Earth viewer adapted for use with DLESE.

  3. Photonic dark matter portal revisited

    NASA Astrophysics Data System (ADS)

    Alavi, S. A.; Kazemian, F. S.

    2016-05-01

    In our previous paper, we studied a model of dark matter (DM) in which the hidden sector interacts with standard model particles via a hidden photonic portal (HP). We investigated the effects of this new interaction on the hydrogen atom and obtained an upper bound for the coupling of the model as f ≤ 10-12. In this work, we study the effects of HP on two interesting exotic atoms namely muonium and positronium. We obtain a tighter upper limit on the coupling as f ≤ 10-13. We also calculate the change (shift) in the Aharonov-Bohm phase due to HP and find that the phase shift is negligibly small (for DM particles mass in the GeV range). Recently a 3.5 keV X-ray line signal observed in the spectrum of 73 galaxy clusters, reported by the XXM-Newton X-ray observatory. Since in HP model the DM particles can decay directly into photons, so we finally calculate the value of the coupling constant f using the condition ΔEDM = 3.5 keV.

  4. The ENSEMBLES Statistical Downscaling Portal

    NASA Astrophysics Data System (ADS)

    Cofino, Antonio S.; San-Martín, Daniel; Gutiérrez, Jose M.

    2010-05-01

    The demand for high-resolution seasonal and ACC predictions is continuously increasing due to the multiple end-user applications in a variety of sectors (hydrology, agronomy, energy, etc.) which require regional meteorological inputs. To fill the gap between the coarse-resolution grids used by global weather models and the regional needs of applications, a number of statistical downscaling techniques have been proposed. Statistical downscaling is a complex multi-disciplinary problem which requires a cascade of different scientific tools to access and process different sources of data, from GCM outputs to local observations and to run complex statistical algorithms. Thus, an end-to-end approach is needed in order to link the outputs of the ensemble prediction systems to a range of impact applications. To accomplish this task in an interactive and user-friendly form, a Web portal has been developed within the European ENSEMBLES project, integrating the necessary tools and providing the appropriate technology for distributed data access and computing. In this form, users can obtain their downscaled data testing and validating different statistical methods (from the categories weather typing, regression or weather generators) in a transparent form, not worrying about the details of the downscaling techniques and the data formats and access.

  5. A Quality Assurance Method that Utilizes 3D Dosimetry and Facilitates Clinical Interpretation

    SciTech Connect

    Oldham, Mark; Thomas, Andrew; O'Daniel, Jennifer; Juang, Titania; Ibbott, Geoffrey; Adamovics, John; Kirkpatrick, John P.

    2012-10-01

    Purpose: To demonstrate a new three-dimensional (3D) quality assurance (QA) method that provides comprehensive dosimetry verification and facilitates evaluation of the clinical significance of QA data acquired in a phantom. Also to apply the method to investigate the dosimetric efficacy of base-of-skull (BOS) intensity-modulated radiotherapy (IMRT) treatment. Methods and Materials: Two types of IMRT QA verification plans were created for 6 patients who received BOS IMRT. The first plan enabled conventional 2D planar IMRT QA using the Varian portal dosimetry system. The second plan enabled 3D verification using an anthropomorphic head phantom. In the latter, the 3D dose distribution was measured using the DLOS/Presage dosimetry system (DLOS = Duke Large-field-of-view Optical-CT System, Presage Heuris Pharma, Skillman, NJ), which yielded isotropic 2-mm data throughout the treated volume. In a novel step, measured 3D dose distributions were transformed back to the patient's CT to enable calculation of dose-volume histograms (DVH) and dose overlays. Measured and planned patient DVHs were compared to investigate clinical significance. Results: Close agreement between measured and calculated dose distributions was observed for all 6 cases. For gamma criteria of 3%, 2 mm, the mean passing rate for portal dosimetry was 96.8% (range, 92.0%-98.9%), compared to 94.9% (range, 90.1%-98.9%) for 3D. There was no clear correlation between 2D and 3D passing rates. Planned and measured dose distributions were evaluated on the patient's anatomy, using DVH and dose overlays. Minor deviations were detected, and the clinical significance of these are presented and discussed. Conclusions: Two advantages accrue to the methods presented here. First, treatment accuracy is evaluated throughout the whole treated volume, yielding comprehensive verification. Second, the clinical significance of any deviations can be assessed through the generation of DVH curves and dose overlays on the patient

  6. INTERSPECIES DOSIMETRY MODELS FOR PULMONARY PHARMACOLOGY

    EPA Science Inventory

    Interspecies Dosimetry Models for Pulmonary Pharmacology

    Ted B. Martonen, Jeffry D. Schroeter, and John S. Fleming

    Experimental Toxicology Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangl...

  7. Cross sections required for FMIT dosimetry

    SciTech Connect

    Gold, R.; McElroy, W.N.; Lippincott, E.P.; Mann, F.M.; Oberg, D.L.; Roberts, J.H.; Ruddy, F.H.

    1980-05-02

    The Fusion Materials Irradiation Test (FMIT) facility, currently under construction, is designed to produce a high flux of high energy neutrons for irradiation effects experiments on fusion reactor materials. Characterization of the flux-fluence-spectrum in this rapidly varying neutron field requires adaptation and extension of currently available dosimetry techniques. This characterization will be carried out by a combination of active, passive, and calculational dosimetry. The goal is to provide the experimenter with accurate neutron flux-fluence-spectra at all positions in the test cell. Plans have been completed for a number of experimental dosimetry stations and provision for these facilities has been incorporated into the FMIT design. Overall needs of the FMIT irradiation damage program delineate goal accuracies for dosimetry that, in turn, create new requirements for high energy neutron cross section data. Recommendations based on these needs have been derived for required cross section data and accuracies.

  8. Development of dosimetry using detectors of diagnostic digital radiography systems

    SciTech Connect

    Ariga, Eiji; Ito, Shigeki; Deji, Shizuhiko; Saze, Takuya; Nishizawa, Kunihide

    2007-01-15

    Dosimetry using an imaging plate (IP) of computed radiography (CR) systems was developed for quality control of output of the x-ray equipment. Sensitivity index, or the S number, of the CR systems was used for estimating exposure dose under the routine condition: exposure dose from 1.0 to 1.0x10{sup 2} {mu}C kg{sup -1}, tube voltages from 50 to 120 kV, and added filtration from 0 to 4.0 mm Al. The IP was calibrated by using a 6 cc ionization chamber having traceability to the National Standard Ionization Chamber. The uncertainty concerning the fading effect was suppressed less than 1.9% by reading the latent image 4 min{+-}5 s after irradiation at the room temperature 25.9{+-}1.0 degree sign C. The S number decreased linearly on the logarithmic graph regardless of the beam quality as exposure dose increased. The relationship between the exposure dose (E) and the S number was fitted by the equation E=a{sup '}xS{sup -b}. The coefficient a{sup '} decreased when the added filtration and the tube voltage were increased. The coefficient b was 0.977{+-}0.007 in all beam qualities. The dosimetry using the IP and the equation can estimate the exposure dose in a range from 9.0x10{sup -2} to 5.0 {mu}C kg{sup -1} within an uncertainty of {+-}5% required by the Japanese Industry Standard. This dose range partially included the doses under routine condition. The doses between 1.0 and 1.0x10{sup 2} {mu}C kg{sup -1} under the routine condition can be shifted to the 5% region by using an absorber. The IP dosimetry is applicable to the quality control of the CR systems.

  9. 29 CFR 785.24 - Principles noted in Portal-to-Portal Bulletin.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 3 2013-07-01 2013-07-01 false Principles noted in Portal-to-Portal Bulletin. 785.24 Section 785.24 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR STATEMENTS OF GENERAL POLICY OR INTERPRETATION NOT DIRECTLY RELATED TO REGULATIONS HOURS WORKED Application of Principles Preparatory and...

  10. In vivo dosimetry in brachytherapy

    SciTech Connect

    Tanderup, Kari; Beddar, Sam; Andersen, Claus E.; Kertzscher, Gustavo; Cygler, Joanna E.

    2013-07-15

    In vivo dosimetry (IVD) has been used in brachytherapy (BT) for decades with a number of different detectors and measurement technologies. However, IVD in BT has been subject to certain difficulties and complexities, in particular due to challenges of the high-gradient BT dose distribution and the large range of dose and dose rate. Due to these challenges, the sensitivity and specificity toward error detection has been limited, and IVD has mainly been restricted to detection of gross errors. Given these factors, routine use of IVD is currently limited in many departments. Although the impact of potential errors may be detrimental since treatments are typically administered in large fractions and with high-gradient-dose-distributions, BT is usually delivered without independent verification of the treatment delivery. This Vision 20/20 paper encourages improvements within BT safety by developments of IVD into an effective method of independent treatment verification.

  11. Portal Hypertension and Ascites Due to an Arterioportal Fistula: Sequela of a Remote Traumatic Liver Laceration

    PubMed Central

    Hulkower, Benjamin M.; Butty, Sabah

    2016-01-01

    Arterioportal fistulas (APFs) are a group of vascular disorders, in which systemic arteries communicate with the portal circulation, presenting as a congenital syndrome or more commonly acquired from iatrogenic instrumentation or abdominal trauma. We report the case of a 58-year-old man who developed ascites without underlying risk factors for portal hypertension, which was attributed to an APF found on imaging, manifesting 43 years after sustaining a liver laceration. After angiographic embolization of the APF, the patient’s ascites resolved completely. The prolonged latent period between the patient’s abdominal trauma and eventual presentation with ascites highlights the need to consider vascular malformations in the differential diagnosis of unexplained noncirrhotic portal hypertension.

  12. Developing a Web 2.0 telemedical education system: the AJAX-Cocoon portal.

    PubMed

    Mohammed, S; Orabi, A; Fiaidhi, J; Orabi, M

    2008-01-01

    Web 2.0 technologies such as wikis, podcasts/vodcasting, blogs and semantic portals could be quite effective tools in e-learning for health professionals. If effectively deployed, such tools can offer a way to enhance students', clinicians' and patients' learning experiences, and deepens levels of learners' engagement and collaboration within medical learning environments. However, Web 2.0 requires simplicity of use as well as integration with modern web technologies. This article presents a Web 2.0 telemedical portal, which provides a social community-learning paradigm from the desk of the physician, the student, the hospital administrator, or the insurer. The presented portal utilises RESTful web services and techniques like content syndication, mushups and Asynchronous JavaScript API and XML (AJAX). The designed portal is based on the Apache Cocoon RESTful framework for sharing Digital Imaging and Communications in Medicine (DICOM) medical case studies. Central to this article is the integration between Cocoon and AJAX. The proposed AJAX-Cocoon portal utilises a JSP portlet architecture, which manages the interaction dynamics and overcomes the shortcomings of the JSR 168 and WSRP 1.0 standards. PMID:18583294

  13. The Sydney West Knowledge Portal: Evaluating the Growth of a Knowledge Portal to Support Translational Research

    PubMed Central

    2016-01-01

    Background The Sydney West Translational Cancer Research Centre is an organization funded to build capacity for translational research in cancer. Translational research is essential for ensuring the integration of best available evidence into practice and for improving patient outcomes. However, there is a low level of awareness regarding what it is and how to conduct it optimally. One solution to addressing this gap is the design and deployment of web-based knowledge portals to disseminate new knowledge and engage with and connect dispersed networks of researchers. A knowledge portal is an web-based platform for increasing knowledge dissemination and management in a specialized area. Objective To measure the design and growth of an web-based knowledge portal for increasing individual awareness of translational research and to build organizational capacity for the delivery of translational research projects in cancer. Methods An adaptive methodology was used to capture the design and growth of an web-based knowledge portal in cancer. This involved stakeholder consultations to inform initial design of the portal. Once the portal was live, site analytics were reviewed to evaluate member usage of the portal and to measure growth in membership. Results Knowledge portal membership grew consistently for the first 18 months after deployment, before leveling out. Analysis of site metrics revealed members were most likely to visit portal pages with community-generated content, particularly pages with a focus on translational research. This was closely followed by pages that disseminated educational material about translational research. Conclusions Preliminary data from this study suggest that knowledge portals may be beneficial tools for translating new evidence and fostering an environment of communication and collaboration. PMID:27357641

  14. The MISTRALS programme data portal

    NASA Astrophysics Data System (ADS)

    Brissebrat, Guillaume; Albert-Aguilar, Alexandre; Belmahfoud, Nizar; Cloché, Sophie; Darras, Sabine; Descloitres, Jacques; Ferré, Hélène; Fleury, Laurence; Focsa, Loredana; Henriot, Nicolas; Labatut, Laurent; Petit de la Villéon, Loïc; Ramage, Karim; Schmechtig, Catherine; Vermeulen, Anne

    2016-04-01

    different file formats and data processing tools. The MISTRALS data portal - http://mistrals.sedoo.fr/ - has been designed and developed as a unified tool for sharing scientific data in spite of many sources of heterogeneity, and for fostering collaboration between research communities. The metadata (data description) are standardized and comply with international standards (ISO 19115-19139; INSPIRE European Directive; Global Change Master Directory Thesaurus). A search tool allows to browse the catalog by keyword or multicriteria selection (area, period, physical property...) and to access data. Data sets managed by different data centres (ICARE, IPSL, SEDOO, CORIOLIS) are available through interoperability protocols (OPeNDAP, xml requests...) or archive synchronisation. Every in situ data set is available in the native format, but the most commonly used data sets have been homogenized (property names, units, quality flags...) and inserted in a relational database, in order to enable accurate data selection, and download of different data sets in a shared format. At present the MISTRALS data portal enables to access about 600 datasets. It counts more than 675 registered users and about 100 data requests every month. The number of available datasets is increasing daily, due to the provision of campaign datasets by several projects. Every scientist is invited to browse the catalog, complete the online registration form and use MISTRALS data. Feel free to contact mistrals-contact@sedoo.fr for any question.

  15. The MISTRALS programme data portal

    NASA Astrophysics Data System (ADS)

    Fleury, Laurence; Brissebrat, Guillaume; Belmahfoud, Nizar; Boichard, Jean-Luc; Brosolo, Laetitia; Cloché, Sophie; Descloitres, Jacques; Ferré, Hélène; Focsa, Loredana; Henriot, Nicolas; Labatut, Laurent; Mière, Arnaud; Petit de la Villéon, Loïc; Ramage, Karim; Schmechtig, Catherine; Vermeulen, Anne; André, François

    2015-04-01

    different file formats and data processing tools. The MISTRALS data portal - http://mistrals.sedoo.fr/ - has been designed and developed as a unified tool for sharing scientific data in spite of many sources of heterogeneity, and for fostering collaboration between research communities. The metadata (data description) are standardized and comply with international standards (ISO 19115-19139; INSPIRE European Directive; Global Change Master Directory Thesaurus). A search tool allows to browse the catalog by keyword or multicriteria selection (area, period, physical property...) and to access data. Data sets managed by different data centres (ICARE, IPSL, SEDOO, CORIOLIS) are available through interoperability protocols (OPeNDAP, xml requests...) or archive synchronisation. Every in situ data set is available in the native format, but the most commonly used data sets have been homogenized (property names, units, quality flags...) and inserted in a relational database, in order to enable accurate data selection, and download of different data sets in a shared format. At present the MISTRALS data portal enables to access about 550 datasets. It counts more than 600 registered users and about 100 data requests every month. The number of available datasets is increasing daily, due to the provision of campaign datasets (2012, 2013, 2014) by several projects. Every scientist is invited to browse the catalog, complete the online registration form and use MISTRALS data. Feel free to contact mistrals-contact@sedoo.fr for any question.

  16. The MISTRALS programme data portal

    NASA Astrophysics Data System (ADS)

    Fleury, Laurence; Brissebrat, Guillaume; Belmahfoud, Nizar; Boichard, Jean-Luc; Brosolo, Laetitia; Cloché, Sophie; Descloitres, Jacques; Ferré, Hélène; Focsa, Loredana; Labatut, Laurent; Mastrorillo, Laurence; Mière, Arnaud; Petit de la Villéon, Loïc; Ramage, Karim; Schmechtig, Catherine

    2014-05-01

    different file formats and data processing tools. The MISTRALS data portal - http://mistrals.sedoo.fr/ - has been designed and developed as a unified tool to share scientific data in spite of many sources of heterogeneity, and to foster collaboration between research communities. The metadata (data description) are standardized and comply with international standards (ISO 19115-19139; INSPIRE European Directive; Global Change Master Directory Thesaurus). A search tool allows to browse the catalogue by keyword or by multicriteria selection (location, period, physical property...) and to access data. Data sets managed by different data centres (ICARE, IPSL, SEDOO, CORIOLIS) are available through interoperability protocols (OPeNDAP, xml requests...) or archive synchronisation. At present the MISTRALS data portal allows to access more than 400 datasets and counts more than 500 registered users. The number of available datasets is increasing daily, due to the provision of campaign datasets (2012, 2013) by several projects. Every in situ data set is available in the native format, but the favorite data sets have been homogenized (property names, units, quality flags...) and inserted in a relational database, in order to enable more accurate data selection, and download of different datasets in a shared format. Every scientist is invited to make use of the different MISTRALS tools and data. Do not hesitate to browse the catalogue and fill the online registration form. Feel free to contact mistrals-contact@sedoo.fr for any question.

  17. Applications of Cherenkov Light Emission for Dosimetry in Radiation Therapy

    NASA Astrophysics Data System (ADS)

    Glaser, Adam Kenneth

    Since its discovery in the 1930's, the Cherenkov effect has been paramount in the development of high-energy physics research. It results in light emission from charged particles traveling faster than the local speed of light in a dielectric medium. The ability of this emitted light to describe a charged particle's trajectory, energy, velocity, and mass has allowed scientists to study subatomic particles, detect neutrinos, and explore the properties of interstellar matter. However, only recently has the phenomenon been considered in the practical context of medical physics and radiation therapy dosimetry, where Cherenkov light is induced by clinical x-ray photon, electron, and proton beams. To investigate the relationship between this phenomenon and dose deposition, a Monte Carlo plug-in was developed within the Geant4 architecture for medically-oriented simulations (GAMOS) to simulate radiation-induced optical emission in biological media. Using this simulation framework, it was determined that Cherenkov light emission may be well suited for radiation dosimetry of clinically used x-ray photon beams. To advance this application, several novel techniques were implemented to realize the maximum potential of the signal, such as time-gating for maximizing the signal to noise ratio (SNR) and Cherenkov-excited fluorescence for generating isotropic light release in water. Proof of concept experiments were conducted in water tanks to demonstrate the feasibility of the proposed method for two-dimensional (2D) projection imaging, three-dimensional (3D) parallel beam tomography, large field of view 3D cone beam tomography, and video-rate dynamic imaging of treatment plans for a number of common radiotherapy applications. The proposed dosimetry method was found to have a number of unique advantages, including but not limited to its non-invasive nature, water-equivalence, speed, high-resolution, ability to provide full 3D data, and potential to yield data in-vivo. Based on

  18. Analysis of metal/film and novel metal/amorphous selenium portal detectors

    NASA Astrophysics Data System (ADS)

    Falco, Tony

    Measurements of modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) for metal/film portal detectors are reported for the Cobalt-60 and 10 MV spectra. The detectors consist of a double-emulsion portal film secured between plates of aluminum, copper, brass or lead with thicknesses from 0 to 4.81 mm. The study of MTF, NPS, and DQE shows that both photons and secondary electrons produced within the front-plate and backscattered electrons from the back- plate affect metal/film portal imaging. Study of DQE indicates that the best portal detectors are those without back-plates, and with high density front-plates with thicknesses less than the maximum electron range. This MTF data was modeled with the logit analysis. It is shown that the parameters resulting from the logit analysis depend on the mass thickness and the atomic number of the metal plates. Metal/amorphous selenium (a-Se) electrostatic-based detectors have been developed for portal imaging. The detectors consist of a-Se photoconductive layers of varied thicknesses deposited on plates of varying thicknesses of aluminum, copper, and stainless steel. The metal-plates of the detectors face the incident 6 MV and Co-60 photon spectra during imaging. The sensitivity of the a-Se detectors to dose, electric field across the a- Se layer, plate type, and a-Se thickness is studied. A model showing a cubic relationship between the a-Se latent surface voltage and dose is derived and experimentally verified. A contrast-detail phantom is used to study the image quality and contrast-resolution characteristics of the metal/a-Se detectors. The metal/a- Se detectors produce better quality contrast-detailed images at a considerably lower dose than that offered by the other commercial available portal systems, mainly due to the low inherent noise of the novel detectors. A semi-automatic technique for the direct set-up alignment of radiosurgical circular fields from an isocentric

  19. The DIAS/CEOS Water Portal, distributed system using brokering architecture

    NASA Astrophysics Data System (ADS)

    Miura, Satoko; Sekioka, Shinichi; Kuroiwa, Kaori; Kudo, Yoshiyuki

    2015-04-01

    The DIAS/CEOS Water Portal is a one of the DIAS (Data Integration and Analysis System, http://www.editoria.u-tokyo.ac.jp/projects/dias/?locale=en_US) systems for data distribution for users including, but not limited to, scientists, decision makers and officers like river administrators. This portal has two main functions; one is to search and access data and the other is to register and share use cases which use datasets provided via this portal. This presentation focuses on the first function, to search and access data. The Portal system is distributed in the sense that, while the portal system is located in Tokyo, the data is located in archive centers which are globally distributed. For example, some in-situ data is archived at the National Center for Atmospheric Research (NCAR) Earth Observing Laboratory in Boulder, Colorado, USA. The NWP station time series and global gridded model output data is archived at the Max Planck Institute for Meteorology (MPIM) in cooperation with the World Data Center for Climate in Hamburg, Germany. Part of satellite data is archived at DIAS storage at the University of Tokyo, Japan. This portal itself does not store data. Instead, according to requests made by users on the web page, it retrieves data from distributed data centers on-the-fly and lets them download and see rendered images/plots. Although some data centers have unique meta data format and/or data search protocols, our portal's brokering function enables users to search across various data centers at one time, like one-stop shopping. And this portal is also connected to other data brokering systems, including GEOSS DAB (Discovery and Access Broker). As a result, users can search over thousands of datasets, millions of files at one time. Our system mainly relies on the open source software GI-cat (http://essi-lab.eu/do/view/GIcat), Opensearch protocol and OPeNDAP protocol to enable the above functions. Details on how it works will be introduced during the

  20. Very Early Presentation of Extrahepatic Portal Vein Obstruction Causing Portal Hypertension in an Infant: Uncertainties in the Management and Therapeutic Limitations.

    PubMed

    Khodayar-Pardo, Parisá; Peña Aldea, Andrés; Ramírez González, Ana; Meseguer Carrascosa, Adela; Calabuig Bayo, Cristina

    2016-01-01

    Extrahepatic portal vein obstruction, although rare in children, is a significant cause of portal hypertension (PHT) leading to life-threatening gastrointestinal bleeding in the pediatric age group. PHT may also lead to other complications such as hyperesplenism, cholangyopathy, ascites, and even hepatopulmonary syndrome and portopulmonary hypertension that may require organ transplantation. Herein we report the case of an asymptomatic 11-month-old infant wherein a hepatomegaly and cavernous transformation of the portal vein was detected by liver ultrasound. Neither signs of thrombosis in arteriovenous system, nor affectation of biliary tract were identified in the magnetic resonance imaging study. A significant enlargement of the caudate lobe of the liver was reported. No risk factors were detected. The differential diagnosis performed was extensive. Inherited thrombophilia and storage disorders were especially considered. Liver biopsy was normal. Upper gastrointestinal esophagogastroduodenoscopy detected two small varicose cords on the distal third of the esophagus. Finding a cavernous transformation of the portal vein with evidence of collateral circulation in such an early age is a challenging condition for professionals, since PHT may lead to severe complications during childhood and can compromise growth and development. Evidence-based guidelines for the management of PHT in adults have been published. However, follow-up and treatment of pediatric patients have not yet been standardized. Moreover, management of PHT in infants faces particular difficulties such as technical restrictions that could hinder their treatment. PMID:27504083

  1. Very Early Presentation of Extrahepatic Portal Vein Obstruction Causing Portal Hypertension in an Infant: Uncertainties in the Management and Therapeutic Limitations

    PubMed Central

    Khodayar-Pardo, Parisá; Peña Aldea, Andrés; Ramírez González, Ana; Meseguer Carrascosa, Adela; Calabuig Bayo, Cristina

    2016-01-01

    Extrahepatic portal vein obstruction, although rare in children, is a significant cause of portal hypertension (PHT) leading to life-threatening gastrointestinal bleeding in the pediatric age group. PHT may also lead to other complications such as hyperesplenism, cholangyopathy, ascites, and even hepatopulmonary syndrome and portopulmonary hypertension that may require organ transplantation. Herein we report the case of an asymptomatic 11-month-old infant wherein a hepatomegaly and cavernous transformation of the portal vein was detected by liver ultrasound. Neither signs of thrombosis in arteriovenous system, nor affectation of biliary tract were identified in the magnetic resonance imaging study. A significant enlargement of the caudate lobe of the liver was reported. No risk factors were detected. The differential diagnosis performed was extensive. Inherited thrombophilia and storage disorders were especially considered. Liver biopsy was normal. Upper gastrointestinal esophagogastroduodenoscopy detected two small varicose cords on the distal third of the esophagus. Finding a cavernous transformation of the portal vein with evidence of collateral circulation in such an early age is a challenging condition for professionals, since PHT may lead to severe complications during childhood and can compromise growth and development. Evidence-based guidelines for the management of PHT in adults have been published. However, follow-up and treatment of pediatric patients have not yet been standardized. Moreover, management of PHT in infants faces particular difficulties such as technical restrictions that could hinder their treatment. PMID:27504083

  2. Online dosimetry for temoporfin-mediated interstitial photodynamic therapy using the canine prostate as model

    NASA Astrophysics Data System (ADS)

    Swartling, Johannes; Höglund, Odd V.; Hansson, Kerstin; Södersten, Fredrik; Axelsson, Johan; Lagerstedt, Anne-Sofie

    2016-02-01

    Online light dosimetry with real-time feedback was applied for temoporfin-mediated interstitial photodynamic therapy (PDT) of dog prostate. The aim was to investigate the performance of online dosimetry by studying the correlation between light dose plans and the tissue response, i.e., extent of induced tissue necrosis and damage to surrounding organs at risk. Light-dose planning software provided dose plans, including light source positions and light doses, based on ultrasound images. A laser instrument provided therapeutic light and dosimetric measurements. The procedure was designed to closely emulate the procedure for whole-prostate PDT in humans with prostate cancer. Nine healthy dogs were subjected to the procedure according to a light-dose escalation plan. About 0.15 mg/kg temoporfin was administered 72 h before the procedure. The results of the procedure were assessed by magnetic resonance imaging, and gross pathology and histopathology of excised tissue. Light dose planning and online dosimetry clearly resulted in more focused effect and less damage to surrounding tissue than interstitial PDT without dosimetry. A light energy dose-response relationship was established where the threshold dose to induce prostate gland necrosis was estimated from 20 to 30 J/cm2.

  3. Pancreatic Adenocarcinoma Complicated by Sinistral Portal Hypertension

    PubMed Central

    Kaley, Kristin; Lamb, Lynne

    2016-01-01

    Pancreatic cancer is known for vague symptoms that lead to a delay in diagnosis, and hence most cases are found at an advanced stage. Many complications can happen secondary to pancreatic cancer including diabetes, malabsorption, and deep venous thrombosis. Sinistral (segmental or left-sided) portal hypertension (SPH) refers to portal hypertension confined to the left-sided segment of the portal venous system namely the splenic side, and the most common etiology is splenic vein thrombosis (SVT). We present here a case of a 66-year-old male with advanced pancreatic cancer who died due to bleeding secondary to SVT. We advise physicians caring for these patients to be aware of this complication, which may also be the manifestation of an undiagnosed pancreatic cancer. PMID:27555987

  4. The hospital library and the enterprise portal.

    PubMed

    Bandy, Margaret; Fosmire, Brenda

    2004-01-01

    At Exempla Healthcare, the medical librarians and the e-Business staff are creating an enterprise information portal where medical reference is targeted, easily accessible, and supported by the medical librarians. A team approach has been essential. The e-Business department has worked for nine months coordinating technical challenges required to support personalization, targeted communications, and a single access point for clinical patient data. Exempla medical librarians have been involved in the definition and design of information access needs from the very beginning. The Clinicians Portal was the first developed, with other customizations to follow. Many challenges remain, but by definition, a portal is designed to be flexible and adapt to the changing needs of the enterprise it supports.

  5. Best Practices for Building Web Data Portals

    NASA Astrophysics Data System (ADS)

    Anderson, R. A.; Drew, L.

    2013-12-01

    With a data archive of more than 1.5 petabytes and a key role as the NASA Distributed Active Archive Center (DAAC) for synthetic aperture radar (SAR) data, the Alaska Satellite Facility (ASF) has an imperative to develop effective Web data portals. As part of continuous enhancement and expansion of its website, ASF recently created two data portals for distribution of SAR data: one for the archiving and distribution of NASA's MEaSUREs Wetlands project and one for newly digitally processed data from NASA's 1978 Seasat satellite. These case studies informed ASF's development of the following set of best practices for developing Web data portals. 1) Maintain well-organized, quality data. This is fundamental. If data are poorly organized or contain errors, credibility is lost and the data will not be used. 2) Match data to likely data uses. 3) Identify audiences in as much detail as possible. ASF DAAC's Seasat and Wetlands portals target three groups of users: a) scientists already familiar with ASF DAAC's SAR archive and our data download tool, Vertex; b) scientists not familiar with SAR or ASF, but who can use the data for their research of oceans, sea ice, volcanoes, land deformation and other Earth sciences; c) audiences wishing to learn more about SAR and its use in Earth sciences. 4) Identify the heaviest data uses and the terms scientists search for online when trying to find data for those uses. 5) Create search engine optimized (SEO) Web content that corresponds to those searches. Because search engines do not yet search raw data, so Web data portals must include content that ties the data to its likely uses. 6) Create Web designs that best serves data users (user centered design), not for how the organization views itself or its data. Usability testing was conducted for the ASF DAAC Wetlands portal to improve the user experience. 7) Use SEO tips and techniques. The ASF DAAC Seasat portal used numerous SEO techniques, including social media, blogging

  6. Current management of sinusoidal portal hypertension.

    PubMed

    Ravindra, Kadiyala V; Eng, Mary; Marvin, Michael

    2008-01-01

    Portal hypertension resulting from cirrhosis was one of the biggest challenges faced by general surgeons up until the past two decades. The management of portal hypertensive variceal hemorrhage has undergone dramatic changes during this period. Endoscopic variceal ligation and transjugular intrahepatic portosystemic shunts are currently used with great success. The degree of liver dysfunction remains the most important determinant of outcome in these patients. Patients with cirrhosis who have good liver function and recurrent variceal bleed remain candidates for shunt surgery. However, the need for surgical intervention has become a rarity. The success of liver transplantation has ensured that portal hypertension is cured permanently and one does not often see the critically ill and decompensated patient with cirrhosis on the surgical service. A review of the current treatment options in this very ill patient population is the primary focus of this article.

  7. 340. Caltrans, Photographer October 14, 1935 "TUNNEL WEST PORTAL"; ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    340. Caltrans, Photographer October 14, 1935 "TUNNEL - WEST PORTAL"; VIEW OF TUNNEL - WEST PORTAL' UNDER CONSTRUCTION SHOWING EXCAVATION OF TUNNEL AFTER POUR. 5-1669 - San Francisco Oakland Bay Bridge, Spanning San Francisco Bay, San Francisco, San Francisco County, CA

  8. Patient portals - An online tool for your health

    MedlinePlus

    If your health care provider offers a patient portal, you will need a computer and internet connection to use it. Follow the instructions to register for an account. Once you are in your patient portal, you can ...

  9. 13. Detail, connection point of end post, top chord, portal ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. Detail, connection point of end post, top chord, portal strut, and tension members at upstream side of west portal, view to northwest. - Dry Creek Bridge, Spanning Dry Creek at Cook Road, Ione, Amador County, CA

  10. 43. VIEW OF THE RAMP ABOVE LOWER PORTAL AND RAMP, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    43. VIEW OF THE RAMP ABOVE LOWER PORTAL AND RAMP, LOOKING NORTHWEST. THE RAMP WAS USED TO GUIDE RUN-OFF FROM THUNDERSTORMS AWAY FROM THE PORTAL. - Independent Coal & Coke Company, Kenilworth, Carbon County, UT

  11. Beta particle dosimetry of the trabecular region of a thoracic vertebra utilizing NMR microscopy

    NASA Astrophysics Data System (ADS)

    Jokisch, Derek William

    Radiation damage to the hematopoietic bone marrow represents the primary limiting factor to the further development of internal emitter therapies such as radioimmunotherapy and the use of incorporated radiopharmaceuticals for bone pain palliation. Improvements in radiation dosimetry of bone marrow are believed to be a prerequisite to accurate predictions of myelotoxicity for these radionuclide therapies. Current radiation dosimetry models for the prediction of marrow dose utilize a scheme in which separate calculations of cumulated activity and dose per transition (radionuclide S value) must be made. The selection of an appropriate S value is generally limited to one of only three sources, all of which use as input the trabecular microstructure of an individual measured 20 years ago, and the tissue masses derived from different individuals measured 70 years ago. This work improves on previously developed methods, which may be used to expand the microstructural database (particularly for non-Reference Man patients). Techniques were developed to avoid voxel effects that arise when taking microstructural measurements across a digitized image. In addition, this work developed a basis for comparison of the existing dosimetry models to an accurate methodology allowing for radiation transport in a voxelized image. The images used are obtained using NMR microscopy methods. This work will be the first of its kind in skeletal dosimetry in that it will allow for S- value calculation using microstructural and mass data from the same source. A new method for performing skeletal dosimetry was developed, and absorbed fraction results are found to be consistent in shape with other models. At electron energies less than 100 keV, all models studied were found to be consistent for all source and target combinations. Finally, a dose example comparing accepted methodologies with the one developed in this study illustrated the variance and importance of skeletal tissue masses used in

  12. Breast dosimetry in clinical mammography

    NASA Astrophysics Data System (ADS)

    Benevides, Luis Alberto Do Rego

    The objective of this study was show that a clinical dosimetry protocol that utilizes a dosimetric breast phantom series based on population anthropometric measurements can reliably predict the average glandular dose (AGD) imparted to the patient during a routine screening mammogram. In the study, AGD was calculated using entrance skin exposure and dose conversion factors based on fibroglandular content, compressed breast thickness, mammography unit parameters and modifying parameters for homogeneous phantom (phantom factor), compressed breast lateral dimensions (volume factor) and anatomical features (anatomical factor). The protocol proposes the use of a fiber-optic coupled (FOCD) or Metal Oxide Semiconductor Field Effect Transistor (MOSFET) dosimeter to measure the entrance skin exposure at the time of the mammogram without interfering with diagnostic information of the mammogram. The study showed that FOCD had sensitivity with less than 7% energy dependence, linear in all tube current-time product stations, and was reproducible within 2%. FOCD was superior to MOSFET dosimeter in sensitivity, reusability, and reproducibility. The patient fibroglandular content was evaluated using a calibrated modified breast tissue equivalent homogeneous phantom series (BRTES-MOD) designed from anthropomorphic measurements of a screening mammography population and whose elemental composition was referenced to International Commission on Radiation Units and Measurements Report 44 tissues. The patient fibroglandular content, compressed breast thickness along with unit parameters and spectrum half-value layer were used to derive the currently used dose conversion factor (DgN). The study showed that the use of a homogeneous phantom, patient compressed breast lateral dimensions and patient anatomical features can affect AGD by as much as 12%, 3% and 1%, respectively. The protocol was found to be superior to existing methodologies. In addition, the study population anthropometric

  13. The CeDRES data portal

    NASA Astrophysics Data System (ADS)

    Albert-Aguilar, Alexandre; Delmotte, Pauline; André, François; Brissebrat, Guillaume; Canonici, Jean-Christophe; Piguet, Bruno

    2016-04-01

    SAFIRE is the French facility dedicated to airborne measurement for environmental research. The SAFIRE steering committee decided that access to its archives should be improved. If certain data, including recent campaigns, are available online, access to them is difficult for users because these data are dispersed in as many data portals as campaigns. Most of projects are not able to keep medium to long term online access to their database. Therefore, many airborne data, particularly the oldest, are not available online, stored on media whose sustainability is not guaranteed. SAFIRE also decided to identify old data stored in Meudon (France) on paper and hard media and to rescue with the help of an archivist. At the same time, the development of a centralized digital archive - containing data collected with the Fokker - 27 " ARAT " and Merlin IV aircraft - associated to a web portal was given to SEDOO. The first part of the project consisted in modelling the database. The second part, still in progess, was the development of the CeDRES (Centre de Données aéRoportées & SAFIRE) portal (http://cedres.sedoo.fr) which is responsive and bilingual (French and English) ; and metadata standardization (iso 19115). The main objectives of this project are data preservation and open data access. A first test version of CeDRES portal will be release in mid-February 2016. And operational version is planned for summer 2016. In the future, CeDRES portal will be able to receive and to distribute metadata and data of aircraft currently in service (FALCON-20, ATR-42 and PiperAztec-23). The interoperability implementation and data homogenization are planned in the medium term. The CeDRES portal is part of the French atmospheric chemistry data center AERIS (http://www.aeris-data.fr). Every scientist is invited to browse the catalog and use CEDRES data. Feel free to contact cedres-contact@sedoo.fr for any question.

  14. Aeromonas hydrophila bacteraemia and portal pyaemia.

    PubMed

    Tulsidas, H; Ong, Y Y; Chan, K C

    2008-04-01

    The Aeromonas species uncommonly cause disease in humans. We report portal pyaemia secondary to Aeromonas hydrophila bacteraemia occurring in a 71-year-old Chinese man with no history of hepatobiliary disease or malignancy. He presented with fever, rigors and abdominal bloating for four days and was subsequently found to have Aeromonas hydrophila bacteraemia, portal vein thrombosis and a psoas abscess. He was treated with ciprofloxacin and had a good recovery. Aeromonas hydrophila infection is an uncommon cause of intestinal and extraintestinal infection in man, but must be suspected in immunocompromised hosts and in those exposed to brackish or salt water. PMID:18418529

  15. Framework Development Supporting the Safety Portal

    SciTech Connect

    Prescott, Steven Ralph; Kvarfordt, Kellie Jean; Vang, Leng; Smith, Curtis Lee

    2015-07-01

    In a collaborating scientific research arena it is important to have an environment where analysts have access to a shared repository of information, documents, and software tools, and be able to accurately maintain and track historical changes in models. The new Safety Portal cloud-based environment will be accessible remotely from anywhere regardless of computing platforms given that the platform has available Internet access and proper browser capabilities. Information stored at this environment would be restricted based on user assigned credentials. This report discusses current development of a cloud-based web portal for PRA tools.

  16. Portal increases throughput with SCADA, distributed control

    SciTech Connect

    Bell, D.E.

    1983-06-01

    Portal Pipelines has added a distributed control system run by SCADA (supervisory control and data acquisition) in its Minot, North Dakota control center. The system keeps abreast of crude movements and quantities of oil being delivered. It was installed in specified stages from 5TI programmable controller, to a PM550 controller (in conjunction with FSK modems), to a full SCADA system. Expansion of the pipeline network in 1980 made integration to SCADA necessary. The Minot control center, CRT terminal, and alarm system are described. Backup consists of redundant computers. Portal's daily movement of 100,000 bbl of crude oil would not be possible without SCADA.

  17. Technical Basis Document for PFP Area Monitoring Dosimetry Program

    SciTech Connect

    COOPER, J.R.

    2000-04-17

    This document describes the phantom dosimetry used for the PFP Area Monitoring program and establishes the basis for the Plutonium Finishing Plant's (PFP) area monitoring dosimetry program in accordance with the following requirements: Title 10, Code of Federal Regulations (CFR), part 835, ''Occupational Radiation Protection'' Part 835.403; Hanford Site Radiological Control Manual (HSRCM-1), Part 514; HNF-PRO-382, Area Dosimetry Program; and PNL-MA-842, Hanford External Dosimetry Technical Basis Manual.

  18. Personnel neutron dosimetry at Department of Energy facilities

    SciTech Connect

    Brackenbush, L.W.; Endres, G.W.R.; Selby, J.M.; Vallario, E.J.

    1980-08-01

    This study assesses the state of personnel neutron dosimetry at DOE facilities. A survey of the personnel dosimetry systems in use at major DOE facilities was conducted, a literature search was made to determine recent advances in neutron dosimetry, and several dosimetry experts were interviewed. It was concluded that personnel neutron dosimeters do not meet current needs and that serious problems exist now and will increase in the future if neutron quality factors are increased and/or dose limits are lowered.

  19. Portal Hypertension Secondary to Spontaneous Arterio-Portal Venous Fistulas: Transcatheter Arterial Embolization with n-Butyl Cyanoacrylate and Microcoils

    SciTech Connect

    Yamagami, Takuji; Nakamura, Toshiyuki; Nishimura, Tsunehiko

    2000-09-15

    We report a 73-year-old man with recurrent variceal bleeding due to portal hypertension caused by multiple intrahepatic arterio-portal venous fistulas, which were successfully occluded by embolization with n-butyl cyanoacrylate and micro-coils.

  20. Factors Influencing Student Acceptance and Use of Academic Portals

    ERIC Educational Resources Information Center

    Presley, Adrien; Presley, Theresa

    2009-01-01

    Institutions of higher education have increasing turned to web portals as a way to connect with students. These portals are designed to provide students a centralized point of access to information and services. In spite of the efforts put into developing and maintaining these portals, their use by students can be disappointing. The study…

  1. The Monash Portal: More Than Just a Virtual Gateway.

    ERIC Educational Resources Information Center

    Kennedy, David; Webster, Len; Benson, Robyn; James, Di; Bailey, Nathan

    The My Monash Portal (Portal) at Monash University (Australia) provides a virtual gateway to support student-centered flexible learning by coordinating several of the university's key resources to meet the needs of students and staff. The Portal is intended to help deliver innovative learning programs, foster opportunities to undertake research,…

  2. User Needs of Digital Service Web Portals: A Case Study

    ERIC Educational Resources Information Center

    Heo, Misook; Song, Jung-Sook; Seol, Moon-Won

    2013-01-01

    The authors examined the needs of digital information service web portal users. More specifically, the needs of Korean cultural portal users were examined as a case study. The conceptual framework of a web-based portal is that it is a complex, web-based service application with characteristics of information systems and service agents. In…

  3. Considering User Satisfaction in Designing Web-Based Portals.

    ERIC Educational Resources Information Center

    Zazelenchuk, Todd W.; Boling, Elizabeth

    2003-01-01

    Discusses how Web portals can best serve higher education institutions if portal designers first understand and satisfy user needs. Shares findings from a usability study of an Indiana University enterprise portal application, which indicated that many existing interaction design principles still apply. (EV)

  4. The Lunar Mapping and Modeling Portal: Capabilities and Lunar Data Products to support Return to the Moon

    NASA Astrophysics Data System (ADS)

    Law, E.; Bui, B.; Chang, G.; Goodale, C. E.; Kim, R.; Malhotra, S.; Ramirez, P.; Rodriguez, L.; Sadaqathulla, S.; Nall, M.; Muery, K.

    2012-12-01

    The Lunar Mapping and Modeling Portal (LMMP), is a multi-center project led by NASA's Marshall Space Flight Center. The LMMP is a web-based Portal and a suite of interactive visualization and analysis tools to enable lunar scientists, engineers, and mission planners to access mapped lunar data products from past and current lunar missions, e.g., Lunar Reconnaissance Orbiter, Apollo, Lunar Orbiter, Lunar Prospector, and Clementine. The Portal allows users to search, view and download a vast number of the most recent lunar digital products including image mosaics, digital elevation models, and in situ lunar resource maps such as iron and hydrogen abundance. The Portal also provides a number of visualization and analysis tools that perform lighting analysis and local hazard assessments, such as, slope, surface roughness and crater/boulder distribution. In this talk, we will give a brief overview of the project. After that, we will highlight various key features and Lunar data products. We will further demonstrate image viewing and layering of lunar map images via our web portal as well as mobile devices.

  5. A radiation dosimetry model for radiolabeled monoclonal antibodies: Indium-111-labeled B72. 3-GYK-DTPA for colorectal cancer

    SciTech Connect

    Wilson, L.A.

    1990-01-01

    A foundation was developed for a dosimetry methodology that could be used to calculate absorbed doses in target and nontarget tissues using uniformly and nonuniformly distributed activity. In this methodology, a dosimetry model was developed which consisted of three independent models: (1) the SPECT Model, (2) the Monte Carlo Model, and (3) the Dosimetry Model. The SPECT Model uses Single-Photon Emission Computed Tomography (SPECT) images to determine the volume and radioactive uptake. A computer program was written to automatically read and analyze SPECT images. This program uses an edge detection method to determine the volume. Voxel elements within the identified volume are used to calculate the activity concentrations. THe Monte Carlo Model uses a monte carlso simulation method and results of the SPECT Model to calculate the fraction of photon energy deposited in target and nontarget tissues. The Dosimetry Model combines the results of the SPECT and Monte Carlo Models to determine the absorbed dose in target and nontarget tissues. Several phantom studies were conducted to verify the ability of the Dosimetry Model to evaluate organ and tumor uptake, sizes, and to calculate absorbed doses. Comparisons were made between the Dosimetry Model, other calculational methods (MIRDOSE2, Geometric Factor Method, MIRD Pamphlet No. 3), and TLD measurements. For diagnostic activity doses, the SPECT Model was found to calculate organ volumes of the order of 1,000 ml to within fifteen percent of the actual volumes but it failed to accurately calculate organ volumes of 200 ml or less. No meaningful relationship was found between the actual and SPECT measured activity concentrations. The Dosimetry Model agreed within 12% when compared with the Geometric Factor Method and the MIRD Pamphlet No. 3 results using homogeneously and heterogen