bluuebunny/crossref_metadata_2025 huggingface dataset:
WE‐C‐116‐06: Reducing the Background Field Variations Using the Geometry Information
Authors: Katkuri Y , Buch S , Haacke E , Latif Z , Neelavalli J , Xuan Y
Published: July 2013

Purpose: To demonstrate a new approach for reducing background phase variations in the susceptibility weighted image (SWI)[1]. Methods: In order to perform this experiment, we acquired high resolution sagittal 3D SWI images of the left leg. Background phase variations were removed to significantly reduce the phase due to the geometry and improve the data quality. This was done using forward modeling approach to simulate phase generated only due to the geometry of the leg [2–5]. Results: The collected data indicated that the phase effects due to the background are very large, so we used forward modeling approach to remove the unwanted phase variations in the image background. This approach uses a kernel described by the Green's function in k‐space to generate point dipole effects across the tissues using its magnetic susceptibility properties. The data resulting from this technique gave us improved phase images and also helped in collecting water‐fat out of phase information using complex division of flow compensated (FC) 5.2ms and 6.5ms data sets. To further see the potential of this technique, we complex divided the FC 7.8ms and not FC 7.8ms data sets resulting in data with direct flow information. Conclusion: We have demonstrated that using a homodyne high‐pass filter alone does not remove the phase due to the geometry. Using the proposed novel technique we were able to significantly reduce the phase due to the geometry and improve the quality of the data for further analysis of water and fat separation as well as visualizing veins. The remaining weakness of this method is that the veins appear as fat in the muscle part of the image but the next step in this processing is to due susceptibility mapping which will then remove the veins and leave a pristine fat map. We are currently evaluating this approach.
WE‐C‐116‐11: Prediction of Prostate Gleason Score Using Neural Network and Multi‐Parametric MRI
Authors: Chen S , D' Souza W , Gullapalli R , Mistry N
Published: July 2013

Purpose: To predict prostate Gleason score (Gleason score >6) using neural network and multi‐parametric MRI. Methods: This study included 17 radical prostatectomy patients who underwent in‐vivo multi‐parametric MRI: Diffusion weighted images (DWI), T2‐Mapping, dynamic‐contrast enhanced (DCE) images, and MR spectroscopy (MRS) prior to surgery. The prostate gland was transversely sectioned and each tissue slice was radially divided into 8 sections. Two hundred thirty one of these sections were examined by a pathologist and a Gleason score was graded individually. For each section, distributions of corresponding parameters extracted from MRI images were used in our analysis. These parameters included the apparent diffusion coefficient (ADC) from DWI, T2‐map, forward volume transfer constant (Ktrans) from DCE, and MRS. The mean and standard deviation of the ADC, T2‐map, Ktrans, and their 95th, 90th, 10th, and 5th percentile values were derived from their distributions. A feed‐forward neural network was constructed using a growth algorithm. In this method, among the above variables, only the variables which increased the model performance were selected as input features of network. The network model was validated using a five‐fold cross‐validation Method: data were randomly divided into 5 groups of approximately equal size; four groups of data were used to train network and the remaining one was used to test the network, in turn. The model performance was evaluated with area under the Receiver Operating Characteristics (ROC) curve. Results: MRS, mean value of 90th percentage of Ktrans, mean and standard deviation of 10th percentage of ADC, and mean of 10th percentage of T2‐map were five predictors selected by the neural network model. The area under the ROC curve was 0.77 for cross‐validation data (sensitivity=72%, specificity=71%). Conclusion: Prostate Gleason score can be accurately predicted using multi‐parametric MRI and a neural network model. This provides a non‐invasive way to identify the prostate cancer aggressiveness.
WE‐C‐116‐12: Camer‐Rao Lower Bound Analysis of 1H Magnetic Resonance Spectroscopic Imaging for Breast with Singular Value Decomposition, LCModel and QUEST
Authors: Feng W , Xuan Y , Chu A , Hu J
Published: July 2013

Purpose: LCModel and QUEST supply error estimate capability, however no standard basis available for unknown lipids mixture in breast. Singular Value Decomposition (SVD) with Linear Combination method was developed to implement desired CRLB function. The purpose of this study is to evaluate SVD, QUEST and LCModel quantification for breast MRSI with Camer‐Rao Lower Bound (CRLB) analysis. Methods: Spectrum for 6 metabolite were simulated with Vespa (STEAM SVS, 3.0T, TE=42ms, TM=10ms), mixture spectrum was simulate with known ratio. jMRUI 4.0 (QUEST function) and LCModel 6.3 was used in the study, metabolite basis was generated from individually simulated data. In‐house SVD was developed with Matlab 7.6 to combine Hankel SVD and Linear Combination method. The estimated FID signals are constructed from the quantification parameters, residue error spectrum was calculated by FFT of the difference of original FID and estimated FID. In order to study the CRLB, known simulated spectrum without noise was analyzed with SVD, QUEST and LCModel. Then introduce random noise, quantification residue was analyzed, and estimated parameters with CRLB were compared with results without noise. Sample patient breast MRSI data was collected with Siemens TrioTim (PRESS CSI, 3.0T, TE=80ms). Results: For simulated data, both Quest and LCModel can reliably quantify with SNR of 5 and signal as low as 17% of maximum; while SVD method can quantify with SNR of 10.Representative breast MRSI data were analyzed, LCModel residue error is 13.3% of original maximum and Cho CRLB is 56%; while SVD can achieve 3.7% and 3.6% respectively. Conclusions: For all methods, CRLB estimations increase with decrease the SNR. SVD is sensitive to noise, since it has no prior knowledge to reduce noise, if noise is larger than signal, fake peak can be introduced; while LCModel and QUEST can not quantify breast data well with limited simulated lipid basis.
WE‐E‐137‐01: RSO Refresher Training
Authors: Martel C , Fahey F
Published: July 2013

The Role of the Radiation Safety Officer in the Medical InstitutionMedical institutions generally have a variety of sources of ionizing radiation including radioactive materials, x‐ray devices, and linear accelerators. The role of the RSO can vary widely from one facility to the next. The authority for the regulatory oversight of radioactive materials is delegated to the RSO via a radioactive materials license, and the responsibilities are clearly established. However, authority over other sources of ionizing radiation is less clear which can Result in significant gaps in radiation safety management programs. The responsibility of the RSO is least clear in the area of Radiation Therapy. The RSO may be involved in oversight where radioactive materials are used, but rarely are involved in oversight of external beam therapy. The lack of clarity regarding oversight authority, roles and responsibilities has led to medical events and serious gaps in radiation safety that leave patients, workers and the public at risk. Each institution must perform a thorough review to ensure that a consistent framework for managing radiation safety for all sources of ionizing radiation is applied. The Role of the Radiation Safety Officer in Nuclear MedicineNuclear medicine needs be practiced in a manner that is effective, safe for both employees and patients and compliant with all local, state and federal regulations. It is also imperative to meet the standards set by accrediting bodies such as the Joint Commission. Therefore, it is essential that the radiation safety officer work closely with the professional and technical staff working in nuclear medicine to accomplish this. In this presentation, the role of the radiation safety officer in nuclear medicine and the partnership between radiation safety and nuclear medicine will be discussed. This discussion will be in the context of both smaller programs with a specific radioactive materials license as well as larger programs with a broad license where institutional radiation safety committee may also be established. The items that will be review will be establishment of a hot laboratory for handling radiopharmaceuticals, the planning of an imaging room, particularly in the context of hybrid imaging, the acceptance of radiopharmaceutical shipments, personnel monitoring and the implementation of a set of good practices for radiation safety. Lastly, the communication of radiation dose and its potential, associated risk with patients and their families will be discussed.

Learning Objectives:

1. To understand the role and responsibilities of the Radiation Safety Officer within a medical institution

2. To understand the role and responsibilities of the Radiation Safety Officer in a Nuclear Medicine Department.

3. To be aware of health physics responsibilities that often are part of the responsibilities of the medical physicist.

4. To understand the responsibility for safety with all sources of radiation, machines and materials.
WE‐E‐108‐01: BEST IN PHYSICS (THERAPY) ‐ Radiotherapy Enhancement with a Novel Class of Hollow Nanoconstructs
Authors: Mao W , Huang C , Kearney V , Song K , Christensen P , Sun X , Hao Y , Solberg T
Published: July 2013

Purpose: Gold nanoparticles have been studied as radiation sensitizers to enhance radiotherapy. It has been reported that hollow shell‐shaped nanoparticles may lead to higher radiation enhancement than solid nanoparticles. We have developed a new gold nanoparticle in the shape of a hollow capsule. In this work we investigate the radiotherapy enhancement of this NanoCapsule system. Methods: Hollow shells nanoconstructs with a diameter of approximately 120 nm were synthesized and used for all experiments. Radiotherapy enhancement was evaluated through cytotoxicity of gold NanoCapsules in MDA‐MB‐231 human breast cancer cells in‐vitro. 100–4000 cells were plated in P60 Petri‐dishes and incubated for 24 hours. Sterilized gold nanoparticles were subsequently added to the cultures, in concentrations ranging from 0–350 μM. 48 hours after plating, cell colonies were irradiated using x‐rays from a small animal irradiator (Precision X‐ray, North Branford, CT) or a 6 MV x‐rays in flattening‐filter free mode from a commercial linear accelerator (Truebeam, Varian Medical Systems, Palo Alto, CA). The cell colonies were fixed 8 days after irradiation, stained, and counted. Results: The total intracellular Au concentration was confirmed by ICP‐Mass spectrometry. Control experiments demonstrated no significant cytotoxicity of Au‐NanoCapsules up to an Au concentration of 350 μM. The radiation enhancement was quantified by analyzing the survival fraction, the ratio between the between the numbers of survival colonies of irradiated samples and control samples (no irradiation). The survival fraction dropped from 0.37 to 0.24 using a Truebeam and from 0.17 to 0.03 with a small animal irradiator at a dose of 4 Gy with an Au concentration of 140 μM. Conclusion: Taking advantage of this novel Au‐NanoCapsule geometric configuration allows for gold nanoparticles to permeate the cell membrane and deliver dose locally, greatly reducing the amount of radiation required to achieve the same local control, whereby minimizing dose to sensitive structures.
WE‐E‐108‐02: Tumor Vasculature Dose‐Painting with FDA Approved Concentrations of Cisplatin, Oxaliplatin, and Carboplatin Nanoparticles During External Beam Radiotherapy
Authors: Ngwa W , Altundal Y , Sajo E , Makrigiorgos G , Berbeco R
Published: July 2013

Purpose: Recent studies have cogently demonstrated major dose enhancement to tumor endothelial cells (EC) when targeted with gold nanoparticles (GNPs) during external beam radiotherapy (EBR). This study investigates the endothelial dose enhancement for FDA approved concentrations of platinum‐based nanoparticles: cisplatin nanoparticles (CNPs), Oxaliplatin nanoparticles (ONPs) and carboplatin nanoparticles (CBNPs) as potential alternative to GNPs. Methods: As in previous work for GNPs, analytic calculations were carried out to estimate the dose to the EC caused by radiation‐induced photoelectrons from platinum nanoparticles during EBR. Here, Monte Carlo generated 6 MVp energy spectra at depth of 20 cm (10 × 10 cm2 field) was employed. The endothelial dose enhancement factor (EDEF), representing the ratio of the dose to the EC with and without the presence of nanoparticles was calculated. The Result was then appropriately scaled to reflect the percentage of platinum in CNPs, ONPs, and CBNPs. For the first time, the investigated concentration range took into account a potential clinical scenario where the nanoparticles are released in situ from routinely used fiducials loaded with the nanoparticles. Results: As expected, the results showed increase in EDEF with increased concentration of the nanoparticles for both GNPs and platinum NPs, with the highest contribution to the EDEF coming from the lower kV‐energy part of the EBR beam spectrum. At FDA concentration limits of in situ released nanoparticles results revealed EDEF values of up to ca. 1.8 for 60 mg/g CNPs, 1.6 for 50 mg/g ONPs and 2.2 for 120 mg/g CBNPs. Conclusions: The results predict that substantial photon‐induced dose boost to tumor endothelial cells can be achieved by applying tumor vasculature‐targeted CNPs, ONPs or CBNPs during external beam radiotherapy. Such radiation boosting or vasculature dose painting could be customized to work complementarily with the chemotherapy effect of these nanoparticles for more effective treatment outcomes.
WE‐E‐108‐04: X‐Ray Fluorescence Imaging Guided Microbeam Radiation Therapy
Authors: Chtcheprov P , Hadsell M , Burk L , Ger R , Inscoe C , Yuan H , Chang S , Lu J , Zhou O
Published: July 2013

Purpose: We demonstrate the feasibility of x‐ray fluorescence for quick and accurate image guidance for targeted irradiation of small animal tumor models in Microbeam Radiation Therapy (MRT). Methods: A reduced‐dose treatment beam excites x‐ray fluorescence from contrast agents preferentially‐accumulating at tumor sites. Intensity profiles of the fluorescence signal are mapped as the mouse injected with the contrast agent is moved through the field of view. The tumor location is identified as the regions with high fluorescence intensities. For this feasibility study, our compact small‐animal MRT system and a mouse head phantom were used. The MRT device uses a carbon nanotube (CNT) field emission x‐ray source array operating at 160kVp and adjustable‐width external collimator to generate microbeam radiation at a microbeam dose rate of ∼1Gy/min. A phantom consisting of an acrylic rod inserted into a mouse skull accurately represents the attenuation of the head. The rod contains ∼1.5mm diameter holes separated by 4mm, filled with 12mg/mL iodine solution, similar to the reported tumor concentration from IC injection. The phantom was translated through the treatment beam in 600um steps, 20 seconds per step. The fluorescence signal was recorded using a slit‐collimated spectrum analyzer. Results: Processed spectra displayed fluorescent intensity peaks corresponding with locations of iodine solution in the phantom. The FWHMs of these peaks are 1.78mm and 1.72mm. The actual diameters of corresponding regions are 1.56mm and 1.47mm, indicating ∼250um uncertainty. Conclusion: Preliminary results demonstrated feasibility of x‐ray fluorescence for guidance in MRT. The acquisition time for a 15mm head phantom is ∼8 minutes, within the reported retention time of the contrast agent. ∼250um uncertainty is comparable to results from our in vivo brain tumor‐bearing mouse experiment using MRI and x‐ray image guidance. The x‐ray fluorescent method is substantially faster. The process will be further optimized and validated with in‐vivo studies.
WE‐E‐141‐02: An Improvement in IMRT QA Results and Beam Matching in LINACs Using Statistical Process Control
Authors: Gagneur J , Ezzell G
Published: July 2013

Purpose: The purpose of this study is to apply the principles of Statistical Process Control (SPC) in the context of patient specific IMRT QA to set clinic specific action limits and evaluate the impact of changes to the MLC calibrations on IMRT QA results. Methods: Ten months of IMRT QA data with 247 unique QAs collected on three beam matched LINACS were retrospectively analyzed with a focus on the Gamma Pass Rate (GPR) and the average ratio between the measured and planned doses. Initial control charts and action limits were calculated. Based on this data, changes were made to the leaf gap parameter for the MLCs to improve the consistency between LINACS. This leaf gap parameter is tested monthly using a MLC sweep test. A follow up data set with 119 unique QAs was used to evaluate the impact of the leaf gap parameter change. Results: The initial data average GPR was 98.6 % with an SPC action limit of 93.7%. The average ratio of doses was 1.003 with an upper action limit of 1.017 and a lower action limit of .989. The sweep test results for the LINACS were −1.8%, 0%, and +1.2% from nominal. After the adjustment of the leaf gap parameter all sweep test results were within .4% of nominal. Subsequently, the average GPR was 99.4 % with an SPC action limit of 97.3%. The average ratio of doses was 1.003 with an upper action limit of 1.017 and a lower action limit of .989. Conclusion: Applying the principles of SPC to IMRT QA allowed small differences between closely matched LINACS to be identified and reduced. Ongoing analysis will monitor the process and be used to refine the clinical action limits for IMRT QA.
WE‐E‐141‐03: Comparative Study of Novel Versus Conventional Scanning Modalities for Radiochromic Film Dosimetry
Authors: Rosen B , Soares C , Minniti R , DeWerd L
Published: July 2013

Purpose: To compare the dose response of GAFCHROMIC(R) EBT3 film as measured using conventional document scanner readout to that of a custom‐built laser densitometry system (LDS), and to assess the intrinsic film orientation dependence to coherent light in order to optimize its use in radiation dosimetry. Methods: 108 1×1 cm2 pieces of EBT3 film were cut from a single sheet and read on an Epson 10000XL document scanner (DOC) and on a point‐to‐point LDS equipped with a 635nm diode laser and spectrally matched photodetector. Pixel values were converted to optical density (OD) using calibrated neutral‐density filters. Packets of six films were sealed and mounted at 5cm depth in water perpendicular to a 60Co beam, then exposed to one of 16 dose levels between 30 mGy and 10 Gy. Films were then re‐read to obtain net change in OD (NOD) using both readout modalities. The DOC readouts were repeated for two orthogonal film orientations, and for LDS, with the laser oriented at 9 evenly spaced angles between 0 and 180 degrees. Results: Four to five‐fold increases in NOD measured with LDS as compared to DOC were found over the full dose range. A sinusoidal relationship of NOD versus angle was found at each dose level, and its amplitude increased with dose. The ability for LDS over DOC to distinguish between films exposed to low doses was statistically significant, especially when optimized for scanning angle. Conclusion: This work indicates the potential of radiochromic film, in conjunction with novel scanning methods, to form a dosimetric standard by extending and improving the usable range as a Result of increased NOD, primarily through exploitation of the emulsion polarization to coherent light. Future work will attempt to quantify energy dependence in order to form a fully characterized dosimetry system that can be traced to primary dose standards. Acknowledgement: The authors wish to thank Dr. David Lewis of Ashland, Inc. of Wayne, NJ for making the EBT3 film available to us for these measurements.
WE‐E‐141‐07: Automating Linac QA for Delivery and Analysis
Authors: Eckhause T , Al‐Hallaq H , Ritter T , DeMarco J , Farrey K , Kim G , Popple R , Sharma V , Perez M , Park S , Booth J , Thorwarth R , Moran J
Published: July 2013

Purpose: To assess the quantitative performance and reproducibility of a new generation linear accelerator using images and trajectory log files across institutions. Methods: A test suite was created to include tests recommended by TG142 (e.g, picket fence at cardinal static gantry angles and during VMAT) and TG179 (e.g. image quality). The test suite, distributed to a consortium of 7 institutions, consisted of DICOM‐RT files and a phantom with BBs at known locations. During each delivery, EPID images were acquired along with trajectory log files. Baseline for each irradiation was set with a flood field without the table or phantom. The phantom was then placed in position and the remaining tests were performed. An analysis program, created in Matlab, assessed the accuracy of leaf, jaw, and collimator positions utilizing the EPID images. Trajectory log files were analyzed as well to assess dynamic parameters such as the reproducibility of gantry motion during arc delivery. Results: Fifteen irradiations were performed on 5 accelerators. Leaf position reproducibility was 0.095 mm for a standard MLC and 0.110 mm for an HDMLC, with maximum standard deviations of 0.019, 0.053, and 0.002 mm for static, IMRT, and arc fields over all linacs. Trajectory logs were consistent with measurements. The maximum gantry deviation was 0.247 ± 0.0160 degrees. Using two different materials, the contrast‐to‐noise ratio was 1.43 ±0.740 and 7.41 ±0.24 for kV and MV images with kV CNR varying by more than a factor of 2 between different machines. Conclusion: EPID and trajectory logs demonstrated thresholds for detection of leaf position errors that were an order of magnitude less than TG142 requirements for different delivery types across institutions. Trajectory log files provided more detailed information regarding stability of gantry position. When tracked over time, these data can be used to reassess the frequency of different test types. This work is supported by Varian Medical Systems.
WE‐E‐103‐02: Past, Present and Future Roles of ROC Analysis in Medical Imaging and Quantitative Image Analysis
Authors: Giger M , Toledano A , Myers K , Jiang Y
Published: July 2013

Receiver Operating Characteristic (ROC) analysis has been a mainstay of many research developments as well as various clinical studies/trials. It has provided medical physicists with a way to objectively measure how data are presented in an image, how people perceive those images, and how one can compare different observers or different imaging modalities with each other. ROC analysis plays an important role in both technology assessment and clinical decision‐making, especially as various aspects of imaging biomarkers and personalized medicine are evaluated. Over the past five years, on average, almost 40 papers/year that were published in MEDICAL PHYSICS utilized ROC analysis. The challenges and opportunities in ROC analysis research and in its application in various tasks are active areas, including expanding the mathematical formulation for multiple lesions per image, location‐based sensitivity, and evaluation without ground truth, as well as expanding its role in imaging biomarker validation, assessing response to therapy, theranostics, and image‐based phenotyping with genomics (image‐omics).

Learning Objectives:

1. Review the mathematical foundations and implementation of ROC analysis in basic research and clinical trials; and understand the role and limitations of ROC analysis in large scale clinical studies/trials

2. Recognize advances in ROC analysis in order to incorporate multiple lesions per image, location‐based sensitivity, evaluation without ground truth, theranostics, and others

3. Appreciate the evolving role of ROC analysis in the evaluation of imaging biomarkers and image‐based phenotyping

Research supported by NIH, DOE, and DOD.

COI: Stockholder, Hologic, Inc Shareholder, Quantitative Insights, Inc Royalties, Hologic, Inc Royalties, General Electric Company Royalties, MEDIAN Technologies Royalties, Riverain Technologies, LLC Royalties, Mitsubishi Corporation Royalties, Toshiba Maryellen Giger Corporation Researcher, Koninklijke Philips Electronics NV Researcher, U‐Systems, Inc
WE‐E‐134‐05: Noncontact Ultrasound Applied to Osteroporosis Diagnostics Updated to Include Broadband Ultrasonic Attenuation and Offline Data Analysis
Authors: Ganezer K , Neeson I , Halcrow P , Bulman J
Published: July 2013

Purpose: The purpose was to push forward our efforts on applying noncontact ultrasound to quantitative imaging of cortical bone as described in our recent paper on speed of sound and attenuation, and integrated response to ultrasound spectroscopy including Broadband ultrasound attenuation (BUA) and to replace our noisy piezoelectric transducers with much quieter velocity correcting capacitive transducers at frequencies of 500 kHz and 850kHz. Methods: An NCU imaging system, a pair of broadband capacitive .500 and .850 MHz, non‐contact transducers, and cortical bone phantoms were used to determine bone mineral density (BMD), speed of sound (SOS), integrated acoustical response (IR), and ultrasonic transmittance. Air gaps of greater than 3 cm, two transmission and reflection paths, and a digital signal processor were used to collect data from phantoms of nominal mass density and (BMD) from 1.17 g/cm3 to 2.25 g/cm3 and from 0 g/cm3 to 1.7 g/cm3. Spectra were analyzed offline using Matlab, including its signal processing and Simulink tool boxes as well as customized Matlab based files, therefore providing much more detailed methods then online approaches, as used in our initial paper. Results: Good correlations between known BMD and measured SOS, IR, and transmittance were obtained for all 14 phantoms obtained in the original studies were complimented with spectroscopic and BUA measurements obtained with capacitive transducers that had much better stability then the original measurements and provided strong correlations with the known BMD of phantoms. Conclusion: The results suggest that the usage of capacitive transducers, offline analysis with Matlab including customized simulations and data analysis algorithms yields much better results than those in our original paper. The new results give us all the more impetus to extend the NCU methods to bone phantoms that more closely mimic human cortical bone and to subsequently apply our methods in vivo.
WE‐E‐134‐06: Pilot Project to Test the Feasibility of Automating Quantitative Ultrasound Performance Testing
Authors: Hoeprich D , Davros W
Published: July 2013

Purpose: A pilot project to test the feasibility of automating quantitative ultrasound performance testing in an effort to increase repeatability, accuracy, and efficiency. Methods: Images were acquired from the same phantom (Model ATS 570) with different transducers and base units. The phantom tests for image uniformity, near field ring down (1 mm to 9 mm), depth of penetration (up to 18 cm), vertical and horizontal distance accuracy (nominal distances of 30 to 40 mm), axial and lateral spatial resolution (down to 1 mm), and contrast resolution (+/− 6 dB and +/− 3dB). Images were loaded into MatLab software where algorithms were developed and used to identify phantom fiducials. Various spatial and frequency filters were applied to enhance image uniformity for processing. Performance of the MatLab analyzed images were assessed by verifying the correct identification of objects. Results: The program is semi autonomous in its ability to locate the image and adjust subsequent inspections with changing images. The software is capable of detecting the objects of interest. Examination of the MatLab analyzed images indicate the quantitative assessment of the ultrasound instruments can indeed be performed with comparable results to human evaluation. Location of fiducial edges and fiducial centroids can be reliably and repeatably identified to carry out the performance evaluation of the instrument. Intensities of contrast fiducials can be compared to background intensities for evaluation of system contrast. Conclusion: The positive results of the initial testing give reason to further develop the algorithms to more completely automate the ultrasound quantitative analysis. More work will be performed to automatically identify manufacturer and transducer type from a default naming scheme and auto‐populate report sheets to increase testing efficiency and measurement repeatability. Conceivably, this type of program can be used in remote areas where physicists are scare and remote testing is feasible.
WE‐E‐134‐09: Evaluation of the Performance of Cardiac Displacement and Strain Imaging Using Radiofrequency and Envelope Signals
Authors: Ma C , Varghese T
Published: July 2013

Purpose: Echocardiographic strain imaging is a promising method for detecting deformation of cardiac muscle. In addition to fidelity to the underlying deformation, high spatial and temporal resolution are required for accurate analysis of regional myocardial function. However, all current clinical approaches use speckle‐tracking algorithms applied to B‐mode images derived from envelope signals. Such approaches are inherently of lower spatial resolution, since they require larger data blocks for deformation tracking due to the absence of phase information. Methods: In this study, we evaluate the performance of local strain estimators using B‐mode, envelope and radiofrequency signals, utilizing data acquired from a uniformly elastic tissue mimicking phantom, 3D cardiac simulation, and clinical data on a healthy volunteer. Results: Signal‐to‐noise ratio improvements using radiofrequency signals for linear and phased array geometries were 5.80 dB and 9.48 dB over that obtained with envelope signals (at peak strain) in phantom studies. Cardiac simulation studies over two cardiac cycles, indicate that the standard deviation of estimated strain using envelope signals from two of the six segments for a short‐axis view (anterior and anterolateral) were 48% and 44% higher than that obtained using radiofrequency signals. In a similar manner, analysis on a healthy volunteer also indicate that the standard deviation of the estimated strain using B‐mode and envelope signals were 16% and 42% higher than that obtained using radiofrequency signals in the anteroseptal segment, and 45% and 27% in the anterior segment. Conclusion: These results show the significant reduction in the variability of the strain estimated as well as improvements in the spatial resolution and signal‐to‐noise ratios obtained using radiofrequency signals.
WE‐E‐134‐10: Correlation of Cognitive Function with Ultrasound Strain Indices
Authors: Wang X , Mitchell C , Jackson D , Varghese T , Hermann B , Kliewer M , Dempsey R
Published: July 2013

Purpose: Instability in vulnerable plaque that generates microemboli, may be related to cognitive decline. Strain imaging to detect plaque vulnerability may be able to determine cognitive impairment. Methods: Plaque instability may be characterized by increased strain variations. Radiofrequency signals for ultrasound strain imaging was acquired on the carotid arteries of 24 human subjects using a Siemens S2000 with a 18L5 transducer. These patients were also scored for cognitive function using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Plaque regions were segmented by a radiologist at end‐diastole using the medical interaction toolkit (MITK). A hierarchical block‐matching motion tracking algorithm was utilized to estimate the cumulated axial, lateral, and shear strains within the imaging plane. Maximum, minimum and peak‐to‐peak strain indices in the plaque computed from the mean cumulated strain over a small region of interest (ROI) in the plaque with large deformations (10–20 data points), were obtained. Maximum and peak‐to‐peak mean cumulated strain over the entire plaque region was also computed. All the strain indices were then correlated to the total RBANS score and a Pearson coefficient along with significance was obtained. Results: Our results indicate correlations of the total RBANS score with maximum axial strain (r=−0.491, p=0.014), peak‐to‐peak axial strain (r=−0.401, p=0.041), maximum lateral strain (r=−0.501, p=0.012), and peak‐to‐peak lateral strain (r=−0.507, p=0.011). There was no significant correlation between the total RBANS score and shear strain, and strain indices averaged over the entire identified plaque. Conclusion: Results reveal a direct relationship between the maximum axial and lateral strain indices in carotid plaque with cognitive impairment. Ultrasound strain imaging estimates deformation and elastic properties of plaque, predicting the probability of plaque rupture, which in turn causes emboli. The correlation study indicates that these microemboli may be related to cognitive impairment. This work was supported in part by NIH grants R21 EB010098‐02, R01 NS064034‐04, and 2R01 CA112192‐06.
WE‐F‐105‐03: Development of GPMC V2.0, a GPU‐Based Monte Carlo Dose Calculation Package for Proton Radiotherapy
Authors: Jia X , Schuemann J , Paganetti H , Jiang S
Published: July 2013

Purpose: Monte Carlo (MC) simulation is considered the most accurate method for proton therapy dose calculations. To improve its efficiency, we have previously developed a MC proton dose calculation package, gPMC, on a graphics‐processing unit (GPU) platform. This abstract reports our recent progress towards developing a new version gPMC v2.0, which aims at improving its clinical usability and evaluating it using proton therapy treatment plans. Methods: gPMC v2.0 supports loading source particles from a phase space file. Source particles are first placed to different energy bins according to their energies. Simulation is conducted to transport particles in each bin sequentially. This enforces that particles transported at the same time have similar energies and hence similar computational thread lengths, ensuring computational efficiency in parallel processing. Realistic treatment geometry is supported. A multi‐dose‐counter technique is developed, where multiple dose counters are allocated. Each dose deposition event is randomly assigned to one of the counters. This alleviates memory‐writing conflict problem, when multiple threads attempts to deposit dose to the same voxel. The final dose distribution and statistical uncertainty are obtained based on results at those counters. gPMC v2.0 also supports scoring dose‐to‐water. We have tested the new version in head‐and‐neck patient cases. Results: Computation time is ∼5 seconds for a typical patient case, where 2.1 million protons in a phase space file are simulated. It takes additional ∼8 seconds to load the phase space file. The dose distribution agrees well with that from TOPAS/Geant4. Inside a region of interest defined by the 50% iso‐dose line, gamma passing rate is ∼98% (3mm/3%) and ∼95% (2mm/2%) compared with TOPAS/Geant4 Result. The average relative uncertainty is 1.1%. Conclusion: gPMC has achieved accuracy and efficiency well beyond what was previously accomplished. It supports the recalculation of proton therapy treatment plans, making it feasible for routine clinical applications. This work is supported in part by the University of California Lab Fees Research Program and in part by R01 CA140735
WE‐F‐105‐05: A Web Interface to Cloud‐Based Treatment Head Simulations
Authors: Sawkey D , Constantin M , Svatos M
Published: July 2013

Purpose: Monte Carlo simulations of linear accelerator treatment heads have traditionally involved building the simulated treatment head from specifications provided by the manufacturer. Here, we make pre‐compiled applications available through a web interface, with processors running in the cloud. Methods: Simulations are run on computers on Amazon Web Services, a cloud provider. A machine image (AMI) was created from which multiple instances can be used on a pay‐as‐you‐go basis. The instances present a web interface, where input parameters (such as the target and flattening filter, code version, and parameters of the incident electron beam) are entered. The web form is converted to an input file for the simulation code by a php script. Simulations of the Varian TrueBeam accelerator using Geant4 simulation code are currently available. Phase space files can be written either above the jaws, or below the MLC, and then imported into a separate simulation. Alternatively the dose deposited in a phantom can be calculated. Modifications to the treatment head, for example custom targets, are also possible. The AMI is available to researchers through their own Amazon account. We share the AMI without additional cost; the user is responsible for the Amazon charges (typically USD 0.01/hr/core). Results: The code was verified by matching commissioning data. The web interface was used by collaborators who both matched commissioning data and investigate treatment head modifications. The treatment head was simulated, and modified in the simulation, without disclosure of proprietary information. Input of phase spaces files into EGSnrc was verified. Conclusion: Geant4‐based simulations of the Varian TrueBeam can be run in the cloud, without need for treatment head specifications or a computer cluster. The methods readily generalize to other codes or geometries. As noted in the affiliations, the authors are employees of Varian Medical Systems.
WE‐G‐137‐01: Medical Physics Economics
Authors: Goodwin J , White G , Dirksen B , Fuss W
Published: July 2013

This presentation will review the aspects of medical physics economics and reimbursement that are relevant to the practicing clinical medical physicist. Covered topics will include:CPT© code development, valuation and useMedicare payment systems: Hospital Outpatient Prospective Payment System, Medicare Physician Fee Schedule and Ambulatory Surgical CentersGeneral coding and billing practicesUpcoming changes in reimbursementSources of informationAAPM economic activitiesKnowledge of these topics is essential to the practicing physicist to ensure that his/her work is recognized and billed for correctly. The presentation will not be a comprehensive billing seminar as coverage policies vary with location. However, general guidelines will be reviewed and sources of authoritative billing information will be included.

Learning Objectives:

1. Understand the three primary Medicare reimbursement systems, how they differ in coverage and in the way they determine reimbursement levels.

2. Understand how CPT© codes are utilized to report billable work.

3. Understand where to find authoritative billing and coding information.
WE‐G‐108‐03: Development of a Computer Software Program to Perform Comprehensive Plan Quality Evaluation
Authors: Yang D , Tan J , Li H , Appenzoller L , Mutic S
Published: July 2013

Purpose: The goals are to develop a computer system that performs an automatic and comprehensive plan quality check (QC) according to institutional guidelines, QUANTEC, and RTOG standards, and to standardize and streamline the evaluation, approval, and review of radiotherapy treatment plans. Methods: A computer software program (and backend database) was developed to automatically 1) read the plan data directly from the TPS, 2) process data, 3) match ROI names, 4) compute DVHs, 5) compute plan quality metrics from the DVHs, 6) evaluate the metrics against the QC rules, and 7) create a report. A rule defines a plan metric that should be satisfied, e.g. V95%>95% for PTV. Rules are organized in groups, and multiple groups are defined for each disease site corresponding to different prescriptions or treatment modalities. On‐the‐fly management of groups and rules is implemented to allow creating, editing, copying, and deleting. The tool can create new isodose structures and composite ROIs on‐the‐fly to support comprehensive yet flexible rules. The tool supports a number of plan quality metrics based on DVH or volumetric data and checks complex metrics including hot spots and conformity ratio. OARs that are not covered by the rules are automatically checked against standard OAR tolerances defined in QUANTEC or RTOG protocols. The report is presented to users with multiple tabulated forms containing color coded results and references. Results: This plan QC tool has been successfully tested. The computed DVH and plan quality metrics were verified to be within 0.5% of the TPS computation. It takes less than 1 minute to load data from a TPS, check all the rules, and generate a report, demonstrating the efficiency of this tool. Conclusion: This software program efficiently checks plan quality and is useful for assisting dosimetrists/physicists in treatment planning and physicians in plan evaluation, approval, and chart review.
WE‐G‐108‐04: Establishing a Quantitative Relation Between the Spectrum‐Sampling Rate On the Dose Distribution Accuracy Using a GPU Based Convolution/superposition Algorithm
Authors: Neylon J , Santhanam A , Sheng K , Low D , Kupelian P
Published: July 2013

Purpose: The focus of this work was to determine the quantitative relationship between the spectrum‐sampling rate and the dose calculation accuracy of a GPU‐accelerated convolution/superposition dose algorithm. Methods and Materials: The GPU‐accelerated dose algorithm is a convolution/superposition that samples, in a hyper‐spherical fashion, the volume surrounding a voxel of primary interaction. A set of 8 static phantoms and 14 deformable physics‐based lung models were used for this study. The static phantoms provided a performance baseline to gauge the more clinically relevant dynamic lung dose delivery and dose accuracy. Respiration simulations used a simple sinusoidal breathing pattern to divide the inhalation and exhalation phases equally into 20 total breathing sub‐phases. The spectrum sampling parameters used for the convolution were the azimuthal and elevation angles, and the radial step sampling surrounding the point of primary interaction. The angular sampling parameters were varied between 8 and 48 steps while the radial sampling parameter was varied between 1 mm to 10mm. The sampling combination of 48/48/1mm was taken as the ground truth. A γ‐statistics based dose distribution agreement of greater than 99% of voxels in the calculation with γ(2%, 2mm)<1% and γ(1%, 1mm)<1% was documented. Results: For γ (2%,2 mm) the sampling parameters of 8/8/1mm satisfied the criteria for both phantom and lungs, while γ (1%, 1mm), a sampling parameter of 8/8/1mm satisfied the criteria for phantoms and a sampling parameter of 12/12/1mm satisfied the criteria for lungs. The GPU implementation provided an additional acceleration of up to 70–80x, ∼200x, and ∼2000X for both the phantoms and lung models as compared to CPU implementation with sampling parameters of 8/8/1mm, 12/12/1mm, and 48/48/1mm, respectively. Conclusion: The relation between the spectrum‐sampling rate and the dose accuracy was quantified using a GPU based dose convolution/superposition satisfying two different γ criteria.
WE‐G‐108‐05: A Technique to Detect Dosimetric Errors as Low as 0.5% Arising From MLC Leaf Shifts in Rapid Arc
Authors: Wijesooriya K , Nawrocki J , Read P , Larner J
Published: July 2013

Purpose: RapidArc is a more complicated technique than fixed field IMRT both in terms of treatment planning and delivery. Due to its speedy delivery, RapidArc (RA) is becoming popular in the clinics. Previous work has shown that the detectors used to perform patient specific IMRT QA cannot detect MLC leaf position error induced dosimetric differences even large as 5.6%. We present a patient specific QA technique with the ability to detect MLC leaf error induced dosimetric errors as small as 0.5%. Methods: Dual arc RA plans were made for treatment of head and neck, gastrointestinal and spine cancers of 10 patients on a Trilogy unit. For each patient, four plans were created: i) clinically acceptable RA plan ii) RA plan with a single MLC leaf shifted for only three consecutive control points iii) delivered original plan recreated using linac log file measurements iv) delivered shifted plan recreated using linac log file measurements. Delivered plans were recreated using only MLC positional errors from linac log file measurements. The results were analyzed by comparing voxel by voxel 3D dose differences. To quantify the actual dose difference errors due to intentional MLC shifts, a comparison was performed between the shifted dose map and the original dose map. Results: Simulated MLC shifts gave rise to a trajectory of dose differences with maximum percentage dose differences mean (range) of 0.52 (0.31 – 0.80)%, while measurements from linac log files show a maximum percentage dose differences mean (range) of 0.56 (0.31 – 0.81)%. Maximum background percentage dose differences mean (range) were 0.19 (0.05 – 0.35)%. Measurement related 3D dose map had an average signal to noise ratio of 3.89 for the set of patients analyzed. Conclusion: Linac log file measurements provide the means to detect MLC shift induced dosimetric deviations as small as 0.5% from the prescription dose. UVA Radiation Oncology George Amarino Grants ‐ 2011
WE‐G‐108‐08: A Novel Technique for VMAT QA with EPID in Cine Mode On Varian TrueBeam
Authors: Liu B , Adamson J , Rodrigues A , Zhou F , Yin F , Wu Q
Published: July 2013

Purpose: Volumetric modulated arc therapy (VMAT) is a relatively new treatment modality for dynamic photon radiation therapy. Pre‐treatment quality assurance (QA) is necessary and many efforts have been taken to apply electronic portal imaging device (EPID) based IMRT QA methods to VMAT. It is important to verify the gantry angles during delivery as this is new variable that is also modulated in VMAT. The purpose of this study is to develop and validate a new technique that is accurate and efficient to perform VMAT QA using EPID. Methods: The method utilized EPID cine mode and was tested on Varian TrueBeam in research mode. The cine images were acquired during delivery and converted to dose matrices after profile correction and dose calibration. Sub‐arc corresponding to each cine image was extracted from the original plan and its portal image prediction was calculated. Several analyses were performed including 3D γ analysis (2D images plus gantry angle axis), 2D γ analysis, and other statistical analyses. The method was applied to 21 VMAT beams of 6MV photons and the accuracy of cine image information was investigated. Furthermore, this method's sensitivity to machine delivery errors was studied. Results: The pass rate (97.8±1.1%) for 3D γ analysis was comparable to that from Delta4 (99.9±0.1%) under similar criteria (3%, 3mm, 5% threshold and 3°angle to agreement). The recorded gantry angle and start/stop MUs were found to have sufficient accuracy for clinical QA. Machine delivery errors can be detected through combined analyses of 3D γ index, gantry angle, and percentage dose difference. Conclusion: We have developed and validated a QA technique that can simultaneously verify the gantry angle and delivered MLC fluence for VMAT treatment. The method is efficient and its accuracy is comparable to other methods. B Liu's work was supported by the Chinese Scholarship Council.