bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐C‐303‐06: Treatment Planning Study for Non‐Invasive Cardiac Arrhythmia Ablation with Scanned Carbon Ions in An Animal Model
Authors: Eichhorn A , Constantinescu A , Lehmann H I , Lugenbiel P , Takami M , Richter D , Prall M , Kaderka R , Thomas D , Bert C , Packer D L , Durante M , Graeff C
Published: June 2015

Purpose:

Scanned carbon ion beams might offer a non‐invasive alternative treatment for cardiac arrhythmia, which are a major health‐burden. We studied the feasibility of this procedure in an animal model. The underlying treatment planning and motion mitigation strategies will be presented.

Methods:

The study was carried out in 15 pigs, randomly distributed to 3 target groups: atrioventricular node (AVN, 8 animals with 25, 40, and 55 Gy target dose), left ventricular free‐wall (LV, 4 animals with 40 Gy) and superior pulmonary vein (SPV, 3 animals with 40 Gy). Breathing motion was suppressed by repeated enforced breathholds at end exhale. Cardiac motion was mitigated by an inhomogeneous rescanning scheme with up to 15 rescans. The treatment planning was performed using the GSI in‐house software TRiP4D on cardiac‐gated 4DCTs, applying a range‐considering ITV based on an extended CTV. For AVN and SPV isotropic 5 mm margins were applied to the CTV, while for the LV 2mm+2% range margins were used. The opposing fields for AVN and LV targets were optimized independently (SFUD), while SPV treatments were optimized as IMPT deliveries, including dose restrictions to the radiosensitive AVN.

Results:

Median value of D95 over all rescanning simulations was 99.1% (AVN), 98.0% (SPV) and 98.3% (LV) for the CTV and 94.7% (AVN) and 92.7% (SPV) for the PTV, respectively. The median D5‐D95 was improved with rescanning compared to unmitigated delivery from 13.3 to 6.5% (CTV) and from 23.4 to 11.6% (PTV). ICRP dose limits for aorta, trachea, esophagus and skin were respected. The maximal dose in the coronary arteries was limited to 30 Gy.

Conclusion:

We demonstrated the feasibility of a homogeneous dose delivery to different cardiac structures in a porcine model using a time‐optimized inhomogeneous rescanning scheme. The presented treatment planning strategies were applied in a pig study with the analysis ongoing.

Funding: This work was supported in part by the Helmholtz Association, the American Heart Association Midwest Affiliate Postdoctoral Fellowship Grant, the Mayo Clinic Foundation, and the Goldsmith Foundation.
SU‐C‐204‐04: Patient Specific Proton Stopping Powers Estimation by Combining Proton Radiography and Prior‐Knowledge X‐Ray CT Information
Authors: Collins‐Fekete CA , Brousmiche S , Hansen D , Beaulieu L , Seco J
Published: June 2015

Purpose:

The material relative stopping power (RSP) uncertainty is the highest contributor to the range uncertainty in proton therapy. The purpose of this work is to develop a robust and systematic method that yields accurate, patient specific, RSP by combining 1) pre‐treatment x‐ray CT and 2) daily proton radiograph of the patient.

Methods:

The method is formulated as a linear least‐square optimization problem (min||Ax‐B||2). The parameter A represents the pathlength crossed by the proton in each material. The RSPs for the materials (water equivalent thickness (WET)/physical thickness) are denoted by x. B is the proton radiograph expressed as WET crossed. The problem is minimized using a convex‐conic optimization algorithm with xi<xi+1 constraint. The Gammex RMI‐465 phantom, with 13 material inserts, is used to investigate the optimal RSPs. The proton radiograph (B) is produced using Geant4 simulation. The matrix A is computed by calculating proton trajectories through the CT with the cubic‐spline approach. Geant4 RSPs are used as reference and the clinical HU‐RSP calibration curve is used as comparison. The convergence is investigated as a function of the number of angles and protons used. The radiographs angle which yield the most accurate RSPs are investigated.

Results:

Optimization with 9 angles and 104 protons/angle yields precise RSP (<0.75%) for all materials, except plastic lung (1.5%). Average deviation relative to Geant4 RSP is 0.5% and 3.5% using HU‐RSP. Using more than two angles or more than 4×103 proton does not further increase the RSP estimate accuracy. The insert distance to the beam initial plane is related to the RSP error for this insert material. Specific filters are applied on the proton angle and energy loss to remove nuclear interaction artefacts.

Conclusion:

The proposed formulation of the problem with prior knowledge x‐ray CT demonstrates serious potential to increase the accuracy of present RSP estimates.
SU‐C‐204‐07: The Production of Short‐Lived Positron Emitters in Proton Therapy
Authors: Buitenhuis H J T , Dendooven P , Diblen F , Biegun A K , van Goethem M‐J , van der Graaf E R , Brandenburg S
Published: June 2015

Purpose:

To investigate the production and effect of short‐lived positron emitters when using PET for in‐vivo range verification during a proton therapy irradiation.

Methods:

The integrated production of short‐lived positron emitters in the stopping of 55 MeV protons was measured in water, carbon, phosphorus and calcium targets. The experimental production rates are used to calculate the production on PMMA and a representative set of 4 tissue materials. The number of decays integrated over an irradiation in these materials is calculated as function of the duration of the irradiation, considering irradiations with the same total number of protons.

Results:

The most copiously produced short‐lived nuclides and their production rates relative to the relevant long‐lived nuclides are: 12‐N (T1/2 = 11 ms) on carbon (9.5% of the 11‐C production), 29‐P (T1/2 = 4.1 s) on phosphorus (20% of the 30‐P production) and 38m‐K (T1/2 = 0.92 s) on calcium (113% of the 38g‐K production). No short‐lived nuclides are produced on water. The most noticeable Result is that for an irradiation in (carbon‐rich) adipose tissue, 12‐N will dominate the PET image up to an irradiation duration of 70 s. On bone tissue, 15‐O dominates over 12‐N after 7–15 s (depending on the carbon‐to‐oxygen ratio).

Conclusions:

The presence of 12‐N needs to be considered in PET imaging during proton beam irradiations as, depending on tissue composition and PET scanning protocol, it may noticeably deteriorate image quality due to the large positron range blurring. The results presented warrant investigations into the energy‐dependent production of 12‐N, 29‐P and 38m‐K and their effect on PET imaging during proton irradiations.
SU‐C‐207‐04: Reconstruction Artifact Reduction in X‐Ray Cone Beam CT Using a Treatment Couch Model
Authors: Lasio G , Hu E , Zhou J , Lee M , Yi B
Published: June 2015

Purpose:

to mitigate artifacts induced by the presence of the RT treatment couch in on‐board CBCT and improve image quality

Methods:

a model of a Varian IGRT couch is constructed using a CBCT scan of the couch in air. The model is used to generate a set of forward projections (FP) of the treatment couch at specified gantry angles. The model couch forward projections are then used to process CBCT scan projections which contain the couch in addition to the scan object (Catphan phantom), in order to remove the attenuation component of the couch at any given gantry angle. Prior to pre‐processing with the model FP, the Catphan projection data is normalized to an air scan with bowtie filter. The filtered Catphan projections are used to reconstruct the CBCT with an in‐house FDK algorithm. The artifact reduction in the processed CBCT scan is assessed visually, and the image quality improvement is measured with the CNR over a few selected ROIs of the Catphan modules.

Results:

Sufficient match between the forward projected data and the x‐ray projections is achieved to allow filtering in attenuation space. Visual improvement of the couch induced artifacts is achieved, with a moderate expense of CNR.

Conclusion:

Couch model‐based correction of CBCT projection data has a potential for qualitative improvement of clinical CBCT scans, without requiring position specific correction data. The technique could be used to produce models of other artifact inducing devices, such as immobilization boards, and reduce their impact on patient CBCT images.
SU‐C‐207‐05: A Comparative Study of Noise‐Reduction Algorithms for Low‐Dose Cone‐Beam Computed Tomography
Authors: Mukherjee S , Yao W
Published: June 2015

Purpose:

To study different noise‐reduction algorithms and to improve the image quality of low dose cone beam CT for patient positioning in radiation therapy.

Methods:

In low‐dose cone‐beam CT, the reconstructed image is contaminated with excessive quantum noise. In this study, three well‐developed noise reduction algorithms namely, a) penalized weighted least square (PWLS) method, b) split‐Bregman total variation (TV) method, and c) compressed sensing (CS) method were studied and applied to the images of a computer–simulated “Shepp‐Logan” phantom and a physical CATPHAN phantom. Up to 20% additive Gaussian noise was added to the Shepp‐Logan phantom. The CATPHAN phantom was scanned by a Varian OBI system with 100 kVp, 4 ms and 20 mA. For comparing the performance of these algorithms, peak signal‐to‐noise ratio (PSNR) of the denoised images was computed.

Results:

The algorithms were shown to have the potential in reducing the noise level for low‐dose CBCT images. For Shepp‐Logan phantom, an improvement of PSNR of 2 dB, 3.1 dB and 4 dB was observed using PWLS, TV and CS respectively, while for CATPHAN, the improvement was 1.2 dB, 1.8 dB and 2.1 dB, respectively.

Conclusion:

Penalized weighted least square, total variation and compressed sensing methods were studied and compared for reducing the noise on a simulated phantom and a physical phantom scanned by low‐dose CBCT. The techniques have shown promising results for noise reduction in terms of PSNR improvement. However, reducing the noise without compromising the smoothness and resolution of the image needs more extensive research.
SU‐C‐207‐07: Quantification of Coronary Artery Cross‐Sectional Area in CT Angiography Using Integrated Density: A Phantom Study
Authors: Johnson T , Ding H , Torabzadeh M , Molloi S
Published: June 2015

Purpose:

To investigate the feasibility of quantifying the cross‐sectional area (CSA) of coronary arteries using integrated density in a physics‐based model with a phantom study.

Methods:

In this technique the total integrated density of the object as compared with its local background is measured so it is possible to account for the partial volume effect. The proposed method was compared to manual segmentation using CT scans of a 10 cm diameter Lucite cylinder placed inside a chest phantom. Holes with cross‐sectional areas from 1.4 to 12.3 mm2 were drilled into the Lucite and filled with iodine solution, producing a contrast‐to‐noise ratio of approximately 26. Lucite rods 1.6 mm in diameter were used to simulate plaques. The phantom was imaged with and without the Lucite rods placed in the holes to simulate diseased and normal arteries, respectively. Linear regression analysis was used, and the root‐mean‐square deviations (RMSD) and errors (RMSE) were computed to assess the precision and accuracy of the measurements. In the case of manual segmentation, two readers independently delineated the lumen in order to quantify the inter‐reader variability.

Results:

The precision and accuracy for the normal vessels using the integrated density technique were 0.32 mm2 and 0.32 mm2, respectively. The corresponding results for the manual segmentation were 0.51 mm2 and 0.56 mm2. In the case of diseased vessels, the precision and accuracy of the integrated density technique were 0.46 mm2 and 0.55 mm2, respectively. The corresponding results for the manual segmentation were 0.75 mm2 and 0.98 mm2. The mean percent difference for the two readers was found to be 8.4%.

Conclusion:

The CSA based on integrated density had improved precision and accuracy as compared with manual segmentation in a Lucite phantom. The results indicate the potential for using integrated density to improve CSA measurements in CT angiography.
SU‐C‐201‐02: Quantitative Small‐Animal SPECT Without Scatter Correction Using High‐Purity Germanium Detectors
Authors: Gearhart A , Peterson T , Johnson L
Published: June 2015

Purpose:

To evaluate the impact of the exceptional energy resolution of germanium detectors for preclinical SPECT in comparison to conventional detectors.

Methods:

A cylindrical water phantom was created in GATE with a spherical Tc‐99m source in the center. Sixty‐four projections over 360 degrees using a pinhole collimator were simulated. The same phantom was simulated using air instead of water to establish the true reconstructed voxel intensity without attenuation. Attenuation correction based on the Chang method was performed on MLEM reconstructed images from the water phantom to determine a quantitative measure of the effectiveness of the attenuation correction. Similarly, a NEMA phantom was simulated, and the effectiveness of the attenuation correction was evaluated. Both simulations were carried out using both NaI detectors with an energy resolution of 10% FWHM and Ge detectors with an energy resolution of 1%.

Results:

Analysis shows that attenuation correction without scatter correction using germanium detectors can reconstruct a small spherical source to within 3.5%. Scatter analysis showed that for standard sized objects in a preclinical scanner, a NaI detector has a scatter‐to‐primary ratio between 7% and 12.5% compared to between 0.8% and 1.5% for a Ge detector. Preliminary results from line profiles through the NEMA phantom suggest that applying attenuation correction without scatter correction provides acceptable results for the Ge detectors but overestimates the phantom activity using NaI detectors. Due to the decreased scatter, we believe that the spillover ratio for the air and water cylinders in the NEMA phantom will be lower using germanium detectors compared to NaI detectors.

Conclusion:

This work indicates that the superior energy resolution of germanium detectors allows for less scattered photons to be included within the energy window compared to traditional SPECT detectors. This may allow for quantitative SPECT without implementing scatter correction, reducing uncertainties introduced by scatter correction algorithms.

Funding provided by NIH/NIBIB grant R01EB013677; Todd Peterson, Ph.D., has had a research contract with PHDs Co., Knoxville, TN
SU‐D‐201‐03: Imaging Cellular Pharmacokinetics of 18F‐FDG in Inflammatory/Stem Cells
Authors: Zaman R , Tuerkcan S , Mahmoudi M , Toshinobu T , Kosuge H , Yang P , Chin F , McConnell M , Xing L
Published: June 2015

Purpose:

Atherosclerosis is a progressive inflammatory condition that underlies coronary artery disease (CAD)—the leading cause of death in the USA. Thus, understating the metabolism of inflammatory cells can be a valuable tool for investigating CAD. To the best of our knowledge, we are the first to successfully investigate the pharmacokinetics of [18F]fluoro‐deoxyglucose (18F‐FDG) uptake in a single macrophages and compared with induced pluripotent stem cells (iPSCs) and mesenchymal stem cells (MSCs) with a novel imaging technique, radioluminescence microscopy, initially developed for cancer imaging.

Methods:

Live cells were cultured sparsely on Matrigel in a glass‐bottom dish and starved for 1 hour before incubation with 250 microCi of 18F‐FDG for 45 minutes. Excess radiotracer was removed using DMEM medium without glucose. Before imaging, DMEM (1 mL) was added to the cell culture and a 100 microm‐thin CdWO4 scintillator plate was placed on top of the cells. Light produced following beta decay was imaged with a highly sensitive inverted microscope (LV200, Olympus) fitted with a 40x/1.3 high‐NA oil objective, and an EM‐CCD camera. The images were collected over 18,000 frames with 4×4 binning (1200 MHz EM Gain, 300ms exposure). Custom‐written software was developed in MATLAB for image processing (Figure 1). For statistical analysis 10 different region‐of‐interests (ROIs) were selected for each cell type.

Results:

Figures 2A–2B show bright‐field/fusion images for all three different cell types. The relationship between cell‐to‐cell comparisons was found to be linear for macrophages unlike iPSCs and MSCs, which were best fitted with moving or rolling average (Figure 2C). The average observed decay of 18F‐FDG in a single cell of MSCs per second (0.067) was 20% and 36% higher compared to iPSCs (0.054) and macrophages (0.043), respectively (Figure 2D).

Conclusion:

MSCs was found to be 2–3x more sensitive to glucose molecule despite constant parameters for each cell type examined.
SU‐D‐201‐04: Study On the Impact of Tumor Shape and Size On Drug Delivery to Pancreatic Tumors
Authors: Soltani M , Bazmara H , Sefidgar M , Subramaniam R , Rahmim A
Published: June 2015

Purpose:

Drug delivery to solid tumors can be expressed physically using transport phenomena such as convection and diffusion for the drug of interest within extracellular matrices. We aimed to carefully model these phenomena, and to investigate the effect of tumor shape and size on drug delivery to solid tumors in the pancreas.

Methods:

In this study, multiple tumor geometries as obtained from clinical PET/CT images were considered. An advanced numerical method was used to simultaneously solve fluid flow and solute transport equations. Data from n=45 pancreatic cancer patients with non‐resectable locoregional disease were analyzed, and geometrical information from the tumors including size, shape, and aspect ratios were classified. To investigate effect of tumor shape, tumors with similar size but different shapes were selected and analyzed. Moreover, to investigate effect of tumor size, tumors with similar shapes but different sizes, ranging from 1 to 77 cm3, were selected and analyzed. A hypothetical tumor similar to one of the analyzed tumors, but scaled to reduce its size below 0.2 cm3, was also analyzed.

Results:

The results showed relatively similar average drug concentration profiles in tumors with different sizes. Generally, smaller tumors had higher absolute drug concentration. In the hypothetical tumor, with volume less than 0.2 cm3, the average drug concentration was 20% higher in comparison to its counterparts. For the various real tumor geometries, however, the maximum difference between average drug concentrations was 10% for the smallest and largest tumors. Moreover, the results demonstrated that for pancreatic tumors the shape is not significant. The negligible difference of drug concentration in different tumor shapes was due to the minimum effect of convection in pancreatic tumors.

Conclusion:

In tumors with different sizes, smaller tumors have higher drug delivery; however, the impact of tumor shape in the case of pancreatic tumors is not significant.
SU‐D‐201‐06: Random Walk Algorithm Seed Localization Parameters in Lung Positron Emission Tomography (PET) Images
Authors: Soufi M , Asl A Kamali , Geramifar P
Published: June 2015

Purpose:

The objective of this study was to find the best seed localization parameters in random walk algorithm application to lung tumor delineation in Positron Emission Tomography (PET) images.

Methods:

PET images suffer from statistical noise and therefore tumor delineation in these images is a challenging task. Random walk algorithm, a graph based image segmentation technique, has reliable image noise robustness. Also its fast computation and fast editing characteristics make it powerful for clinical purposes. We implemented the random walk algorithm using MATLAB codes. The validation and verification of the algorithm have been done by 4D‐NCAT phantom with spherical lung lesions in different diameters from 20 to 90 mm (with incremental steps of 10 mm) and different tumor to background ratios of 4:1 and 8:1. STIR (Software for Tomographic Image Reconstruction) has been applied to reconstruct the phantom PET images with different pixel sizes of 2×2×2 and 4×4×4 mm3. For seed localization, we selected pixels with different maximum Standardized Uptake Value (SUVmax) percentages, at least (70%, 80%, 90% and 100%) SUVmax for foreground seeds and up to (20% to 55%, 5% increment) SUVmax for background seeds. Also, for investigation of algorithm performance on clinical data, 19 patients with lung tumor were studied. The resulted contours from algorithm have been compared with nuclear medicine expert manual contouring as ground truth.

Results:

Phantom and clinical lesion segmentation have shown that the best segmentation results obtained by selecting the pixels with at least 70% SUVmax as foreground seeds and pixels up to 30% SUVmax as background seeds respectively. The mean Dice Similarity Coefficient of 94% ± 5% (83% ± 6%) and mean Hausdorff Distance of 1 (2) pixels have been obtained for phantom (clinical) study.

Conclusion:

The accurate results of random walk algorithm in PET image segmentation assure its application for radiation treatment planning and diagnosis.
SU‐E‐E‐01: Revamping the Classroom for An Active Learning Environment
Authors: Rutel IB
Published: June 2015

Purpose:

Removing traditional didactic lecture from session contact time provides the opportunity to keep the classroom interaction active, keeping both the students and instructor engaged.

Methods:

Participant survey evaluation analysis for a non‐traditional teaching environment during a technical graduate course, conducted over three course offerings (81 sessions, total) and 23 graduate medical physics student participants is offered. The modified course structure utilizes multiple alternate teaching methods, including the flipped classroom, online lecture offerings, peer teaching, problem based learning and guided discussions for each session. Viewing online lectures and textbook reading were prerequisites for class sessions, while scheduled open question time, guided interrogative sections, problem‐based whiteboard activities and peer teaching were the focus of class designated contact time. Effectiveness and student perception/satisfaction were gauged by end of course, participant survey responses (both scaled questions and free‐form response).

Results:

In general, students responded with positive feedback and indicated better understanding when the course was viewed as a whole. Granularity of understanding was further broken into the various components in broad categories which includes utilizing only the online lecture material, using only the interrogative classroom experience and the use of the text book as the sole source of learning material. Analysis of the survey results and a description of the classroom activities are presented.

Conclusion:

The modified classroom environment is conducive to more active engagement between the students and the instructor, leading to better perceived information retention and overall satisfaction with the course offering.
SU‐E‐E‐02: An Excel‐Based Study Tool for ABR‐Style Exams
Authors: Cline K , Stanley D , Defoor D , Stathakis S , Gutierrez A , Papanikolaou N , Kirby N
Published: June 2015

Purpose:

As the landscape of learning and testing shifts toward a computer‐based environment, a replacement for paper‐based methods of studying is desirable. Using Microsoft Excel, a study tool was developed that allows the user to populate multiple‐choice questions and then generate an interactive quiz session to answer them.

Methods:

The code for the tool was written using Microsoft Excel Visual Basic for Applications with the intent that this tool could be implemented by any institution with Excel. The base tool is a template with a setup macro, which builds out the structure based on user's input. Once the framework is built, the user can input sets of multiple‐choice questions, answer choices, and even add figures. The tool can be run in random‐question or sequential‐question mode for single or multiple courses of study. The interactive session allows the user to select answer choices and immediate feedback is provided. Once the user is finished studying, the tool records the day's progress by reporting progress statistics useful for trending.

Results:

Six doctoral students at UTHSCSA have used this tool for the past two months to study for their qualifying exam, which is similar in format and content to the American Board of Radiology (ABR) Therapeutic Part II exam. The students collaborated to create a repository of questions, met weekly to go over these questions, and then used the tool to prepare for their exam.

Conclusion:

The study tool has provided an effective and efficient way for students to collaborate and be held accountable for exam preparation. The ease of use and familiarity of Excel are important factors for the tool's use. There are software packages to create similar question banks, but this study tool has no additional cost for those that already have Excel. The study tool will be made openly available.
SU‐E‐E‐03: Shared Space Fosters Didactic and Professional Learning Across Professions for Medical and Physics Residents
Authors: Dieterich S , Perks J , Fragoso R
Published: June 2015

Purpose:

Medical Physicists and Radiation Oncologists are two professions who should be working as a team for optimal patient care, yet lack of mutual understanding about each others respective role and work environment creates barriers To improve collaboration and learning, we designed a shared didactic and work space for physics and radiation oncology residents to maximize interaction throughout their professional training.

Methods:

Physician and Physics residents are required to take the same didactic classes, including journal clubs and respective seminars. The residents also share an office environment among the seven physician and two physic residents.

Results:

By maximizing didactic overlap and sharing office space, the two resident groups have developed a close professional relationship and supportive work environment. Several joint research projects have been initiated by the residents. Awareness of physics tasks in the clinic has led to a request by the physician residents to change physics didactics, converting the physics short course into a lab‐oriented course for the medical residents which is in part taught by the physics residents. The physics seminar is given by both residency groups; increased motivation and interest in learning about physics has led to several medical resident‐initiated topic selections which generated lively discussion. The physics long course has changed toward including more discussion among residents to delve deeper into topics and study beyond what passing the boards would require. A supportive work environment has developed, embedding the two physics residents into a larger residents group, allowing them to find mentor and peers more easily.

Conclusion:

By creating a shared work and didactic environment, physician and physics residents have improved their understanding of respective professional practice. Resident‐initiated changes in didactic practice have led to improved learning and joint research. A strong social support system has developed, embedding physics residents into a larger peer group.
SU‐E‐E‐06: Teaching About the Gamma Camera and Ultrasound Imaging
Authors: Lowe M , Spiro A , Vogel R , Donaldson N , Gosselin C
Published: June 2015

Purpose:

Instructional modules on applications of physics in medicine are being developed. The target audience consists of students who have had an introductory undergraduate physics course. This presentation will concentrate on an active learning approach to teach the principles of the gamma camera. There will also be a description of an apparatus to teach ultrasound imaging.

Methods:

Since a real gamma camera is not feasible in the undergraduate classroom, we have developed two types of optical apparatus that teach the main principles. To understand the collimator, LEDS mimic gamma emitters in the body, and the photons pass through an array of tubes. The distance, spacing, diameter, and length of the tubes can be varied to understand the effect upon the resolution of the image. To determine the positions of the gamma emitters, a second apparatus uses a movable green laser, fluorescent plastic in lieu of the scintillation crystal, acrylic rods that mimic the PMTs, and a photodetector to measure the intensity. The position of the laser is calculated with a centroid algorithm.To teach the principles of ultrasound imaging, we are using the sound head and pulser box of an educational product, variable gain amplifier, rotation table, digital oscilloscope, Matlab software, and phantoms.

Results:

Gamma camera curriculum materials have been implemented in the classroom at Loyola in 2014 and 2015. Written work shows good knowledge retention and a more complete understanding of the material. Preliminary ultrasound imaging materials were run in 2015.

Conclusion:

Active learning methods add another dimension to descriptions in textbooks and are effective in keeping the students engaged during class time. The teaching apparatus for the gamma camera and ultrasound imaging can be expanded to include more cases, and could potentially improve students’ understanding of artifacts and distortions in the images.
SU‐E‐E‐15: Design of a Water Calorimeter for Dual Use in An Integrated MRI‐Linac and Gamma‐Knife
Authors: Entezari N , Renaud J , Ly D , Sarfehnia A
Published: June 2015

Purpose:

To design a water calorimeter for dual use in an integrated MRI‐linac and Gamma‐Knife. In calorimetry, dose to water is measured based on the assumption that energy absorbed in a sensitive volume is completely converted to temperature rise ₍ΔΤ₎ according to the specific heat capacity of the medium c: D=c*ΔT*k, where k is heat transfer correction factor and compensates for heat gain or loss at point of measurement due to conductive effects.

Methods:

A commercial finite element method software package was used to model four different water calorimeter designs. The long term (48 h) thermal stability of each design was accurately modeled, and the optimization of the final design was based on evaluation of the standard deviation of k for ten consecutive irradiation runs (lower standard deviation translates to greater thermal stability). Several insulator materials of varying thicknesses were investigated, and a sensitivity study of thermal stability to variations in ambient temperature fluctuations was undertaken. Specifically, we evaluated the effect of possible variations in coolant temperature circulating around the calorimeter tank in several scenarios (constant, slowly increasing, or fluctuating).

Results:

Due to MRI‐compatibility requirements, the calorimeter is to be built entirely out of plastic. Among all insulation materials tested, solid state aerogel‐based insulation resulted in least heat loss and thermal stability. The final design is cylindrical on top (to be used upright in MRI‐linac) and semi‐spherical at bottom (for use in GammaKnife). The range of k was found to be 1.002 ± 0.013 (k = 1), comparable with a k of 1.002 ± 0.014 for typical water calorimeters used in high energy beams. A long term stability of 0.36 µK/hr was evaluated.

Conclusion:

Optimization of a water calorimeter design for dual use in MRI‐linac and Gamma‐Knife has been completed and the device is currently in production.

Supported by NSERC RGPIN 435608
SU‐E‐P‐05: Electronic Brachytherapy: A Physics Perspective On Field Implementation
Authors: Pai S , Ayyalasomayajula S , Lee S
Published: June 2015

Purpose:

We want to summarize our experience implementing a successful program of electronic brachytherapy at several dermatology clinics with the help of a cloud based software to help us define the key program parameters and capture physics QA aspects. Optimally developed software helps the physicist in peer review and qualify the physical parameters.

Methods:

Using the XOFT™ Axxent™ electronic brachytherapy system in conjunction with a cloud‐based software, a process was setup to capture and record treatments. It was implemented initially at about 10 sites in California. For dosimetric purposes, the software facilitated storage of the physics parameters of surface applicators used in treatment and other source calibration parameters. In addition, the patient prescription, pathology and other setup considerations were input by radiation oncologist and the therapist. This facilitated physics planning of the treatment parameters and also independent check of the dwell time. From 2013–2014, nearly1500 such calculation were completed by a group of physicists. A total of 800 patients with multiple lesions have been treated successfully during this period. The treatment log files have been uploaded and documented in the software which facilitated physics peer review of treatments per the standards in place by AAPM and ACR.

Results:

The program model was implemented successfully at multiple sites. The cloud based software allowed for proper peer review and compliance of the program at 10 clinical sites. Dosimtery was done on 800 patients and executed in a timely fashion to suit the clinical needs. Accumulated physics data in the software from the clinics allows for robust analysis and future development.

Conclusion:

Electronic brachytherapy implementation experience from a quality assurance perspective was greatly enhanced by using a cloud based software. The comprehensive database will pave the way for future developments to yield superior physics outcomes.
SU‐E‐P‐06: A Graphical User Interface (GUI) Toolkit Created for Multi‐Phase Biological Effective Dose (BED) Calculations Including Statistical Analyses
Authors: Kauweloa K , Gutierrez A , Stathakis S , Papanikolaou N , Mavroidis P
Published: June 2015

Purpose:

There is growing interest amongst clinics in applying the biological effective dose (BED) to their treatment plan evaluations, as well as potential optimizations due to its stronger correlation with radiobiological effects. An approximate, multi‐phase biological effective dose (BEDA) equation was introduced in order to simplify BED calculations using many current treatment planning systems (TPS). The purpose of this work is to create a MATLAB graphical user interface (GUI) in order to determine the accuracy and precision of BEDA in common clinical treatments.

Methods:

A number of algorithms were written in order to read exported treatment plans from the TPS Pinnacle. Those algorithms were then tested and compared with the results on Pinnacle in order to determine its accuracy. BED algorithms were then created in order to calculate the BEDT and BEDA distributions. The algorithms for the DVH statistics, the Bland‐Altman Analysis, and the Percent Error were written and added to this GUI in order to study the accuracy and precision of BEDA.

Results:

When comparing the DVH results from the created MATLAB GUI to those from Pinnacle, there was less than a 1% difference in the dose distribution statistics such as the maximum, minimum, mean, and standard deviation for the dose in the specific region of interest. The amount of time needed to calculate the BED distributions ranged anywhere from 5 to 90 seconds due to its dependence on the size of the dose distribution matrix.

Conclusion:

Due to the dose distribution accuracy, it is safe to use this MATLAB GUI toolkit to study the approximate BED calculation method. It can also be used to analyze patient treatment plans using the true BED distributions and the biological effective dose volume histograms (BEDVHs). In addition, further studies can be performed in determining BED constraints for different organs and endpoints.
SU‐E‐P‐07: Retrospective Analysis of Incident Reports at a Radiology Department: Feedback From Incident Reporting System
Authors: Kakinohana Y , Toita T , Heianna J , Murayama S
Published: June 2015

Purpose:

To provide an overview of reported incidents that occurred in a radiology department and to describe the most common causal source of incidents.

Methods:

Incident reports from the radiology department at the University of the Ryukyus Hospital between 2008 and 2013 were collected and analyzed retrospectively. The incident report form contains the following items, causal factors of the incident and desirable corrective actions to prevent recurrence of similar incidents. These items allow the institution to investigate/analyze root causes of the incidents and suggest measures to be taken to prevent further, similar incidents. The ‘causal factors of the incident’ item comprises multiple selections from among 24 selections and includes some synonymous selections. In this study, this item was re‐categorized into four causal source types: (i) carelessness, (ii) lack of skill or knowledge, (iii) deficiencies in communication, and (iv) external factors.

Results:

There were a total of 7490 incident reports over the study period and 276 (3.7%) were identified as originating from the radiology department. The most frequent causal source type was carelessness (62%). The other three types showed similar frequencies (10–14%). The staff members involved in incidents indicate three predominant desirable corrective actions to prevent or decrease the recurrence of similar incidents. These are ‘improvement in communication’ (24%), ‘staff training/education’ (19%), and ‘daily medical procedures’ (22%), and the most frequent was ‘improvement in communication’. Even though the most frequent causal factor was related to carelessness, the most desirable corrective action indicated by the staff members was related to communication.

Conclusion:

Our finding suggests that the most immediate causes are strongly related to carelessness. However, the most likely underlying causes of incidents would be related to deficiencies in effective communication. At our department, therefore, the primary action to prevent/reduce similar incidents should be ‘communication improvement’.
SU‐E‐P‐13: Quantifying the Geometric Error Due to Irregular Motion in Four‐Dimensional Computed Tomography (4DCT)
Authors: Sawant A
Published: June 2015

Purpose:

Respiratory correlated 4DCT images are generated under the assumption of a regular breathing cycle. This study evaluates the error in 4DCT‐based target position estimation in the presence of irregular respiratory motion.

Methods:

A custom‐made programmable externally‐and internally‐deformable lung motion phantom was placed inside the CT bore. An abdominal pressure belt was placed around the phantom to mimic clinical 4DCT acquisitio and the motion platform was programmed with a sinusoidal (±10mm, 10 cycles per minute) motion trace and 7 motion traces recorded from lung cancer patients. The same setup and motion trajectories were repeated in the linac room and kV fluoroscopic images were acquired using the on‐board imager. Positions of 4 internal markers segmented from the 4DCT volumes were overlaid upon the motion trajectories derived from the fluoroscopic time series to calculate the difference between estimated (4DCT) and “actual” (kV fluoro) positions.

Results:

With a sinusoidal trace, absolute errors of the 4DCT estimated markers positions vary between 0.78mm and 5.4mm and RMS errors are between 0.38mm to 1.7mm. With irregular patient traces, absolute errors of the 4DCT estimated markers positions increased significantly by 100 to 200 percent, while the corresponding RMS error values have much smaller changes. Significant mismatches were frequently found at peak‐inhale or peak‐exhale phase.

Conclusion:

As expected, under conditions of well‐behaved, periodic sinusoidal motion, the 4DCT yielded much better estimation of marker positions. When an actual patient trace is used 4DCT‐derived positions showed significant mismatches with the fluoroscopic trajectories, indicating the potential for geometric and therefore dosimetric errors in the presence of cycle‐to‐cycle respiratory variations.
SU‐E‐P‐17: Flipping the Classroom: Improving Physics Education in a Clinical Environment
Authors: Rasmussen K , Ferreira C , Corbett M , Stephenson S , Naves J
Published: June 2015

Purpose:

The traditional model of an active presenter with a passive audience is one of the least effective methods of education availiable.1 Additionally, it is difficult for an instructor to balance time preparing for course lectures with clinical duties. An alternative method would be to reduce the amount of lecture time in the class, with a greater emphasis on outside readings or videos that students watch prior to attending scheduled class hours.

Methods:

The Clinical Rotation course at ECU was revamped to incorporate >30 TG Reports to develop deeper understanding of clinical aspects. Students were expected to read and bring questions on the topics to a weekly discussion session. Additional questions were asked by the instructor to verify understanding and emphasize key points of the reports. A final oral exam was given in the style of ABR part 3 to determine comprehensive analysis of the students understanding.

Results:

Over the past five semesters of the course, students have consistently had positive feedback on the course and overall scores have been good. Students benefited greatly from active learning during class discussions. A comparison with previous average grades was not possible. Time for preparation of the discussion is greatly reduced from time consuming powerpoint presentations.

Conclusion:

It is important to balance time in clinic and time teaching to optimize efficiency in education without sacrificing patient care. It is also important to deliver a quality education to students. This method also has the added benefit of emphasizing the importance of task group reports to students which will be a primary source of reference in clinical settings.1McIntosh, N.,&Sullivan, N. (1996). Delivering effective lectures. JHPIEGO Strategy Papers.
SU‐E‐P‐18: Intensity‐Modulated Radiation Therapy for Cervical Esophageal Squamous Cell Carcinoma
Authors: Bai W , Qiao X , Zhou Z , Song Y , Zhang R , Zhen C
Published: June 2015

Purpose:

To retrospectively analyze the outcomes and prognostic factors of cervical esophageal squamous cell carcinoma (SCC) treated with intensity modulated radiation therapy (IMRT).

Methods:

Thirty‐seven patients with cervical esophageal SCC treated with IMRT were analyzed retrospectively. They received 54–66 Gy in 27–32 fractions. Nineteen patients received concurrent (n=12) or sequential (n=7) platinum‐based two drugs chemoradiotherapy. Overall survival (OS), local control rates (LCR) and prognostic factors were evaluated. Acute toxicities and patterns of first failures were observed.

Results:

The median follow‐up was 46 months for alive patients. The l‐, 3‐, 4‐ and 5‐year OS of the all patients were 83.8%, 59.1%, 47.5% and 32.6% respectively. The median survival time was 46 months. The l‐, 3‐,4‐ and 5‐year LCR were 82.9%, 63.0%, 54.5% and 54.5%, respectively. Univariate and Multivariate analysis all showed that size of GTV was an independent prognostic factor (p=0.033, p=0.039). There were no patients with Grade 3 acute radiation esophagitis and Grade 2–4 acute pneumonitis. The local failure accounted for 70.0% of all treatment‐related failures.

Conclusion:

IMRT is safe and effective in the treatment of cervical esophageal squamous cell carcinoma. Size of GTV is an independent prognostic factor. Local failure still remains the main reason of treatment failures.

The authors declare no conflicts of interest in preparing this article.
SU‐E‐P‐26: Oncospace: A Shared Radiation Oncology Database System Designed for Personalized Medicine, Decision Support, and Research
Authors: Bowers M , Robertson S , Moore J , Wong J , Phillips M , Hendrickson K , Song W , Kwok P , DeWeese T , McNutt T
Published: June 2015

Purpose:

Advancement in Radiation Oncology (RO) practice develops through evidence based medicine and clinical trial. Knowledge usable for treatment planning, decision support and research is contained in our clinical data, stored in an Oncospace database. This data store and the tools for populating and analyzing it are compatible with standard RO practice and are shared with collaborating institutions. The question is ‐ what protocol for system development and data sharing within an Oncospace Consortium? We focus our example on the technology and data meaning necessary to share across the Consortium.

Methods:

Oncospace consists of a database schema, planning and outcome data import and web based analysis tools.1) Database: The Consortium implements a federated data store; each member collects and maintains its own data within an Oncospace schema. For privacy, PHI is contained within a single table, accessible to the database owner.2) Import: Spatial dose data from treatment plans (Pinnacle or DICOM) is imported via Oncolink. Treatment outcomes are imported from an OIS (MOSAIQ).3) Analysis: JHU has built a number of webpages to answer analysis questions. Oncospace data can also be analyzed via MATLAB or SAS queries.These materials are available to Consortium members, who contribute enhancements and improvements.

Results:

1) The Oncospace Consortium now consists of RO centers at JHU, UVA, UW and the University of Toronto. These members have successfully installed and populated Oncospace databases with over 1000 patients collectively.2) Members contributing code and getting updates via SVN repository. Errors are reported and tracked via Redmine. Teleconferences include strategizing design and code reviews.3) Successfully remotely queried federated databases to combine multiple institutions’ DVH data for dose‐toxicity analysis (see below – data combined from JHU and UW Oncospace).

Conclusion:

RO data sharing can and has been effected according to the Oncospace Consortium model: http://oncospace.radonc.jhmi.edu/.

John Wong ‐ SRA from Elekta; Todd McNutt ‐ SRA from Elekta; Michael Bowers ‐ funded by Elekta
SU‐E‐P‐29: Testing Display Monitors for GSDF Compliance ‐ a Practical Approach
Authors: Gauntt D
Published: June 2015

Purpose:

To develop a simple technique for testing display monitors for compliance with the DICOM Grayscale Standard Display Function (GSDF), in accordance with the recommendations of AAPM Task Group 18.

Methods:

We have developed a spreadsheet that can be used to compare both the luminance response and contrast response of a display to the GSDF, using luminance measurements of the SMPTE test pattern. The contrast response compares the slope of the GSDF j‐index as a function of pixel value to that of the GSDF function, and should lie within the range 0.85 to 1.15.

Results:

We present the results of measurements both of primary diagnostic displays and of ultrasound and acquisition workstations, all at a tertiary care hospital. The Barco displays in the radiographic reading rooms are GSDF compliant or nearly so, while those in the ultrasound reading rooms and at the acquisition workstations generally show significantly higher contrast at low luminance levels than they would if GSDF compliant, and lower contrast at high luminance levels.

Conclusion:

The spreadsheet that we developed allows a simple comparison of measured display contrast response to the GSDF. Although we used the SMPTE pattern, the same technique could be used with other grayscale patterns, such as TG18‐QC and TG18‐PQC.