bluuebunny/crossref_metadata_2025 huggingface dataset:
MO‐D‐134‐09: Assessing DNA Damage Repair From CT Studies in Whole Blood
Authors: Elgart SR , Adibi A , Khatonabadi M , Ruehm S , Enzmann D , McNitt‐Gray M , Iwamoto K
Published: July 2013

Purpose: To assess biological damage due to radiation from CT studies using in vivo and ex vivo blood samples processed with a newly developed protocol involving flow cytometry. Methods: This study was carried out under IRB approval. Blood samples were collected from 21 patients undergoing clinically‐indicated CT exams. Blood was procured prior to, immediately after and 30minutes following irradiation. For each patient, a sample of pre‐scan blood was transferred into a vial and positioned on the patient within the scan region for ex vivo comparative analysis. Whole blood samples were fixed immediately following each collection to arrest cellular metabolism. The cellular response to DNA double strand breaks (DSBs) was analyzed by flow cytometric quantification of gammaH2AX fluorescence. Median fluorescence of treatment samples were compared to non‐irradiated control blood samples for each patient. Results: Four patient samples were excluded due to technical issues in collection and analysis. The remaining 17 showed two major trends for gammaH2AX signal following irradiation in vivo. Some samples showed an increase immediately following irradiation and a further increase at 30minutes. Others showed an increase immediately following irradiation then a subsequent decrease at 30minutes. However, ex vivo samples showed different kinetics to in vivo counterparts. Interestingly, two patients had high basal gammaH2AX fluorescent signal (p<0.01) and exhibited large increases following irradiation. This Result was apparent for both patients after in vivo analysis, but only one patient after ex vivo analysis. Conclusion: These results indicate significant variation in damage and repair kinetics across a small sample of patients; furthermore, we demonstrated differences between in vivo and ex vivo samples. Rapid analysis and accurate timing offer the ability to assess a large number of patients to establish baseline population data. Additionally, this method may serve as an indicator to identify patients for further analysis of radiation sensitivity. Research partially supported by a grant from Siemens AG
MO‐D‐134‐11: Anomalous Scanner‐Reported Values of CTDIvol
Authors: Dixon R , Boone J
Published: July 2013

Purpose: Significant anomalies in scanner reported values of CTDIvol for stationary table protocols (with aberrant, elevated values of CTDIvol up to 300 % higher than the actual dose to the phantom), have been observed; well beyond the typical accuracy expected of CTDIvol as a phantom dose. Recognition of these outliers as bad data is important to users of CT dose index tracking systems (e.g. ACR DIR), and a method for recognition and correction is provided. A second anomaly is that the reported CTDIvol for automatic tube current modulation (TCM) has a different physical meaning from the traditional CTDIvol at constant mA, resulting in the dichotomy CTDIvol of the first and second kinds. Methods: Rigorous equations are derived to describe the accumulated dose distributions for auto TCM and for stationary table CT. A comparison with formulae for scanner reported values of CTDIvol clearly identifies the source of these anomalies. Results: For the stationary table, use of the CTDI100 formula (applicable to a moving phantom only) generates extra scatter and an over beaming correction, both of which are non existent if the phantom is held stationary. It is shown that CTDIvol is not robust between fixed mA and auto TCM in this case only DLP is robust. Conclusion: For the case of a stationary phantom, correction of CTDI100 prior to its use in the calculation of CTDIvol using the approach to equilibrium formula H(a) serves as a method of recognition of bad data and as a correction factor for same. In the case of auto TCM, the use of CTDIvol is compromised, and an alternative (approximate) physical interpretation is suggested. However, the reported DLP value (integral dose) remains robust between the fixed and auto mA modes.
MO‐D‐116‐01: MRI Applications in Radiation Oncology
Authors: Olsen J , Hu Y , Low D , Cao Y
Published: July 2013

Computed tomography (CT) is the standard imaging modality for radiation oncology. CT simulation, together with advanced dose delivery techniques, has moved radiotherapy from the 2D to the 3D era, enabling conformal dose delivery such as 3D conformal radiation therapy and intensity‐modulated radiation therapy. CT simulation has greatly advanced our capability to manage cancer in the last two decades. However, suboptimal soft tissue contrast may limit accuracy of target and organ‐at‐risk delineation. Magnetic Resonance Imaging (MRI) has superior soft tissue contrast. Unlike CT, MRI acquisition sequences can even be tailored to highlight tumors or improve contrast between organs. In addition, MRI can provide valuable functional information to aid target definition and evaluate treatment response. MRI has been increasingly used in radiation oncology in support of CT to improve tumor and organ‐at‐risk delineation in radiation therapy. In this session, we will discuss how MRI can benefit radiation oncology clinics from a physician perspective, current status of MRI guided radiotherapy systems, feasibility and challenges in MRI‐based radiotherapy treatment planning and advanced MRI techniques to study tumor response to radiation therapy.

Learning Objectives:

1. Identify cases where MRI can provide valuable information for radiation therapy

2. Learn the basis of MRI guided radiotherapy systems

3. Understand the current status and the challenges in MRI‐based treatment planning for radiation therapy4. Become familiar with advanced quantitative MRI techniques such as DWI and DCE‐MRI to assess radiotherapy treatment response.
MO‐E‐105‐01: How To Be A Journal Referee
Authors: Becker S , Boone J , Orton C , Starkschall G , Thomadsen B
Published: July 2013

Being a referee for a journal article is an important yet daunting task. It is especially worrisome for someone who has little reviewing experience. It is important to remember is that it is an honor and perhaps a duty, but not a burden. Someone considers you to be an expert in the subject and it is with that mindset that you should approach the task. Each part of the review process has its own difficulties:• Grammar and Language: How much of this do you need to do? Does poor grasp of the English language warrant rejection. Is it effective or excessively verbose?• Science: Is this project novel? How do you determine that? How similar can it be to other previously published manuscripts?• References: Are the proper studies referenced? How much does this affect the review?• Methods: How do you determine if the methods are sound? How much can you suggest without trying to be a collaborator?• Results: Are graphs and tables being utilized wisely? Are there an excessive number of them?All of these issues are important part of the review process and need to be considered. But how do you weight them in your final recommendation and communicate them to the authors and editors? This panel of senor medical physics, which has extensive experience in refereeing, will help guide the audience through the entire review process. These experts will share their experiences and methods to help new referees best prepare for the opportunity of reviewing manuscripts.

Learning Objectives:

1. Learn the role of the referee and what is expected of them.

2. Learn how to perform a review.

3. Learn how to communicate a review with authors and editors.
MO‐F‐137‐01: Controlling Stuff, Beating Stress, and Finding Work‐Life Balance
Authors: Jordan D
Published: July 2013

Many busy professionals are susceptible to stress, burnout, and other work‐related conditions that detract from their quality of life. Medical physicists are no exception, and in some ways are even more susceptible to these pressures and difficulties than other professionals. The challenges to maintaining physical and mental stamina are real and fast‐changing due to advances in technology, economic forces, and generational shifts and trends in the workforce. A stressed or burned‐out individual is probably working harder than he or she needs to due to inefficient workflow. Such people tend to take a lot of work home with them, negatively impacting their priorities outside the workplace. As the stress mounts, it is typical to feel that one needs to “get organized” or improve “time management” in order to improve the situation. Most such efforts fail, if they are even begun.There are a number of popular approaches to time management and goal‐setting which fail to address these challenges because they take an unrealistic approach. These methods fail because they don' t give the user control over his or her situation. Unpleasant and difficult circumstances generate the most stress when the individual feels out of control. A successful approach to time, task, and stress management must be based on principles, but these principles must be tied to implementing clear and simple practices. This session will introduce a set of principles for managing time, tasks, and resources, beginning with attention. Examples of specific practices that support the principles will be discussed. The meaning of “work‐life balance” will be explored as it relates to the medical physics profession. Attendees will learn an approach to controlling their attention and focus so they can move toward aligning their day‐to‐day activities with their longer‐term goals.

Learning Objectives:

1. Explain what work‐life balance means to you.

2. Describe the principles of self‐direction and control that are needed to align activities with goals and priorities.

3. List three practices that lead to greater personal control and greater efficiency.
MO‐F‐108‐02: A Retrospective Study On the Potential Clinical Gain of On‐Line Adaptive Re‐Planning for Pancreatic Cancer SBRT
Authors: Li Y , Hoisak J , Li N , Graves Y , Gautier Q , Tian Z , Zarepisheh M , Cervino L , Jia X , Jiang S , Murphy J
Published: July 2013

Purpose: Stereotactic body radiotherapy (SBRT) shows promise in unresectable pancreatic cancer with high rates of local control compared to conventionally fractionated radiotherapy. One critical limitation with pancreas SBRT arises from toxicity in the nearby duodenum, which is a dynamic and distensible organ that changes shape daily. The purpose of this pilot study was to evaluate the potential gains of daily adaptive re‐planning with SBRT in pancreatic cancer. Methods: Pancreas SBRT patients were re‐planned using our previously developed GPU‐based supercomputing online re‐planning environment (SCORE), which automatically and quickly generates plans from daily cone‐beam CT (CBCT) data with the original plan and DVH as a reference. For each patient, the tumor volume and normal structure contours were deformed from the original planning CT to each daily CBCT. The deformed contours were reviewed and edited by a physician, and then the plan was re‐optimized to account for daily changes in anatomy. The daily adaptive re‐planned dose was compared to the actual dose received for the target volume and nearby duodenum. Results: Fourteen daily CBCT scans were used to generate daily adaptive radiation plans. For all patients, the average target coverage for the PTV improved, and the cold spot decreased with daily adaptive re‐planning. The cold spot (minimum dose to 1% of PTV) decreased on average from 25.1% to 4.6% (p=0.002, paired t‐test). With daily adaptive re‐planning the hot spot in the duodenum (volume that received 100% of dose) decreased from 2.8% to 1.7% (p=0.09). Doses to other organs were clinically insignificant, and did not significantly change with daily adaptive radiotherapy. Conclusion: This pilot study shows that daily adaptive re‐planning with pancreas SBRT has the potential to improve target coverage, and reduce dose to normal organs. Further study into the technical implementation of daily adaptive re‐planning is ongoing. Varian Medical Systems through a Master Research Agreement
MO‐F‐108‐04: Inverse Planning for Multi‐Stage Robotic Stereotactic Radiosurgery for Large Cerebral Arteriovenous Malformations
Authors: Ding C , Solberg T , Hrycushko B , Medin P , Whitworth L , Timmerman R
Published: July 2013

Purpose: A new inverse treatment planning technique was developed for multi‐staged robotic stereotactic radiosurgery of large cerebral arteriovenous malformations. Methods: Eleven patients with large (>15 cm3) cerebral arteriovenous malformations (AVMs) were selected in this study. The AVMs were contoured and divided into 3 to 8 sub‐targets with volumes of 3–7 cm3 to be treated sequentially in a staged approach at one to four week intervals. The prescription dose was 16 Gy to 20 Gy depending on the sub‐target volume and location. Inverse robotic radiosurgery treatment plans were generated for the total AVM volume and optimized to achieve 95% coverage. Staged plans for individual sub‐targets were generated from the total AVM plan usingthe weighting MUs based on beam lengths within each sub‐targets. Forward plans were created for comparison. Dose‐volume analysis was used to evaluate the PTV coverage, conformity index (CI), R50 and V12Gy values. Results: Inverse optimization outperformed forward planning for most patients for each index considered. In eight of the eleven patients the inversely optimized plans had better target coverage (96.0+/− 0.6% vs.95.8+/−1.3% for forward plan) while all of the patients had improved high dose conformality with the inversely optimized plans (1.23+/−0.16 vs. 1.44+/−0.16). Moderate dose spillage within the brain, as represented by the R50 parameter, was shown to improve in ten of the eleven patients for inversely optimized plans (3.2+/−0.7 vs. 3.9+/−0.7). Conclusion: Inverse treatment planning for staged, robotic radiosurgery of large AVMs was shown to improve target coverage, target dose conformality, and reduce normal tissue dose compared to forward treatment planning.
MO‐F‐108‐06: A Novel Analytic Approach to Assessing Rotation‐Induced Dosimetric Errors of Stereotactic Radiosurgery Cases
Authors: Zhang Q , Song Y , Chan M , Burman C , Yamada Y
Published: July 2013

Purpose: To assess 3D rotational setup error effect on dose distribution, we derive a new set of beams such that the beams‐eye‐views of this new set of beams with respect to the planning CT are the same as those of the original plan for the patient, but with setup rotation errors incorporated. Methods: To assess the rotation effects on the dose distribution of stereotactic radiosurgery (SRS) cases, a methodology was developed and two sets of table, gantry, and collimator angles were obtained in analytical forms. Those new angles emulate the rotation effects of setup errors. Eight SRS cases were computed with a series of different combinations of patient rotation errors, ranging from (−5°, −5°, −5°) to (5°, 5°, 5°) (roll, pitch and yaw) with an increment of 1°. For each set of rotational errors, its corresponding equivalent beams were computed using our analytical solution and used for dose calculation. Results: The above new beams were implemented in a treatment planning system (TPS). Based on all the plans that accounted for different rotations, we have found that rotations have an insignificant effect on the minimum, maximum, mean doses, and V80% of the planning target volume when the rotations were relatively small. This was particularly true for the small and near‐spherical targets. They, however, did change V95% significantly when the rotations approached 5°. Our theory has been validated with SRS cases and proven to be practical and viable. Conclusions: We have derived analytical solutions to a new set of table, gantry and collimator angles for a given beam configuration as a function of patient rotation errors. Compared to the traditional method of rotational effect assessment by importing rotated CT images into TPS, our equivalent beam approach is simple and accurate. It is a promising technique for real time adaptive treatment planning.
MO‐F‐108‐08: A Revolving Collimator for Proton Stereotactic Radiosurgery (pSRS)
Authors: Moskvin V , Cheng C , McDonald M , Das I
Published: July 2013

Purpose: Stereotactic radiosurgery (SRS) is a non‐invasive treatment modality appropriate for a wide array of tumors. Particularly in patients with benign tumors receiving proton SRS (pSRS), the generation of secondary neutrons from brass apertures may be associated with higher risk of secondary radiation‐induced tumors. A specially designed revolving titanium alloy collimator system with multiple sized collimator openings in circular and elliptical shapes is proposed and investigated in this study. Methods: Simulations of the passage of a proton beam through the proposed collimator system was performed using the FLUKA Monte Carlo general purpose code with treatment nozzle model implemented. The set of materials potentially applicable for the collimator fabrication, i.e. brass, stainless steel (SS), tungsten alloy (WA) and titanium alloy (TiA) (Ti‐6A1‐4V Grade 5) were simulated. The neutron fluence, dose equivalent, activation of the collimator material, the cooling times and beam shaping properties are analyzed. Results: Utilization of TiA results in less neutron dose equivalent at the patient compared to brass, WA or SS. The neutron flux spectra for TiA is an order of magnitude lower than those for the other materials in the energy interval with the maximum neutron weighting factor. The activation of TiA is lower and the cooling time 10 times shorter compared to WA. Dose shaping with the pSRS collimator is similar to a brass aperture. Dose enhancement at shallow depths for small proton fields limits the practical collimator opening size. Conclusion: The specially designed revolving pSRS titanium alloy collimator proposed in this study may reduce secondary neutron dose to the patient compared to other collimator materials investigated. This may reduce the risk of secondary tumors and malignancies and reduce late effects to the patient. The pSRS collimator allows the establishment of a pSRS system and methodology without the need for a dedicated pSRS treatment vault.
MO‐F‐500‐01: Clinical Applications of Surface Imaging
Authors: Al‐Hallaq H , Cervino L , Sonke J
Published: July 2013

Non‐invasive 3D surface matching systems have become clinically available for patient positioning and tracking throughout treatment. This session will focus on the current clinical applications of surface imaging, specifically for breast radiotherapy and cranial radiosurgery. First, acceptance and commissioning of surface imaging systems will be reviewed. Next, workflows and resulting data will be presented for the use of surface imaging to position patients receiving whole‐breast irradiation. Additionally, workflows and data describing the use of surface imaging to track patients during breath‐hold breast cancer treatments and frameless radiosurgery will also be described. The session outline is: a. An overview of commissioning and acceptance testing of surface imaging systems, including incorporation of routine QA into current clinical practice for a comprehensive IGRT program b. The use of surface imaging for daily positioning of patients receiving whole‐breast radiotherapy c. Surface imaging applications for breath‐hold treatment of left‐sided breast cancer patients d. Surface imaging applications for frameless cranial radiosurgery.

Learning Objectives:

1. Learn to incorporate QA for surface imaging into current QA procedures for IGRT.

2. Understand the advantages and limitations of surface imaging for clinical use in breast radiotherapy and cranial radiosurgery.

3. Learn about the potential use of surface imaging for real‐time motion tracking.

Jan‐Jakob Sonke's research is sponsored by Elekta Corporation.

Elekta Corporation sponsors research by Jan‐Jakob Sonke.
MO‐F‐WAB‐03: Trajectory Imaging: Exploring Options of Kilovoltage Digital Tomosynthesis During Intensity Modulated Radiation Therapy
Authors: Zhang P , Hunt M , Pham H , Mageras G
Published: July 2013

Purpose: To integrate novel kilovoltage (kV) digital tomosynthesis (DTS) sequences into intensity modulated radiation therapy (IMRT) to determine 3D fiducial positions for intrafractional motion monitoring. Method: In one method, we converted a static gantry IMRT beam into a series of arcs in which dose index and multileaf collimator positions for all control points were kept intact, but gantry angles were modified to oscillate +/−3° around the original angle. kV projections were acquired continuously throughout delivery and reconstructed to provide a series of 6° arc DTS images which were used to evaluate in‐plane positions of gold fiducials embedded in an anthropomorphic phantom. To obtain out‐of‐plane positions via triangulation, a 20° gantry rotation with beam held‐off was inserted during delivery to produce a pair of 6° DTS images separated by 14°. In a second method, the gantry remained stationary, but both kV source and detector moved over a 15° longitudinal arc via pitch and translational adjustment of the robotic arms. Evaluation of localization accuracy in phantom during simulated intrafractional motion used programmed couch translations from customized scripts. In‐house software was used to reconstruct DTS images, register them to reference DTS images and calculate 3D fiducial positions. Result No significant dose difference (<0.5%) was found between the original and converted IMRT beams. For a typical hypofractionated spine treatment, 200 single DTS (6° arc) and 10 paired DTS (20° arc) were acquired for each IMRT beam, providing in‐plane (IP) and out‐of‐plane (OP) monitoring every 1.5 and 30 seconds, respectively. Mean (standard deviation) error in predicted position was −0.3(0.2)mm, −0.1(0.1)mm IP, and 0.2(0.4)mm OP with rotational gantry, −0.1(0.1)mm, 0.7(0.3)mm IP and 1.9(1.1)mm OP with translational source/detector. Conclusion: Acquiring 3D fiducial positions from kV‐DTS during IMRT delivery is technically feasible. Enabling movement of kV‐source and detector during delivery could further reduce imaging time overhead. Part of the research is sponsored by Varian Medical System.
MO‐F‐WAB‐09: Improvement of Digitally Reconstructed Radiograph Quality of Thoracic 4D Cone Beam Computed Tomography
Authors: Wang M , Sharp G , Rit S , Delmon V , Wang G
Published: July 2013

Purpose: 4D cone beam computed tomography (4DCBCT) suffers from poor image quality, which limits its use as a reference image for image‐guided procedures that use radiography and fluoroscopy. This abstract demonstrates improved image quality in Digitally Reconstructed Radiographs (DRR) derived from thoracic 4DCBCT. Methods: In our method, projection images are used to create both a phase‐rebinned 4D volume and streak‐free 3D volume. These volumes are combined into a new 4DCBCT that includes stationary voxels from 3D volume and moving voxels from 4D volume. Stationary voxels include the chest wall, which has only small motion during breathing, and moving voxels include the soft tissues inside chest wall, such as lung, heart, and abdomen. The chest wall was segmented from 3D volume, and the segmented Result was used to replace corresponding voxels in 4D volume. To generate the DRR, only high intensity voxels, including chest wall, heart, abdomen, main vessels and bronchi, and tumor, were used. This method reduced streak artifacts of 4DCBCT volume, but preserved the motion information present within the lungs and diaphragm. Results: DRR images computed from 4DCBCT are visually poor because of the streak artifacts, while DRR images computed from 3DCBCT suffer from motion blur. The DRR computed from the combined 3D and 4D volumes are visually more similar to the original projection images at corresponding projection angles. Conclusion: DRR image quality declined because of the streak artifacts in 4DCBCT. By combining 4D volume and streak‐free 3D volume and extracting the high intensity voxels to generate DRR, the streak artifacts can be effectively reduced, which results in improvement of the DRR image quality. This work was supported by the National Basic Research Program of China (973) under Grant 2011CB707701 and research foundation of Tsinghua University.
MO‐F‐WAB‐10: Evaluation of Scan Time Required for Motion Tracking in Four‐Dimensional Cone Beam CT Using Patient Data Sets
Authors: Martin R , Ahmad M , Hugo G , Pan T
Published: July 2013

Purpose: Applying four‐dimensional cone beam CT in a radiation treatment setting requires a tradeoff between image quality and scan time. The aim of this study is to assess the minimum scan time required to determine the motion of tumors immediately prior to radiation treatment. Methods: Long CBCT scans of approximately 10 minutes were taken from 11 patients with lung lesions. Shorter scan times (down to about 1 minute) for these patients were simulated by removing projections. Four dimensional images were created from each full and simulated scan time using a ROI based FDK reconstruction algorithm with 8 breathing phases. Tumor motion for each phase relative to the first phase was determined through deformable image registration in a region of interest. The ability to track motion was assessed by comparing the results of the image registration of the simulated scans to the results for the full data scan. Results: For each comparison between the full data set and a reduced data set, a root‐mean‐square error was calculated comparing the two motions on a phase by phase basis, with the summation being over the phases. As anticipated, the RMS error as well as the spread in the RMS error increased with decreasing scan time. Good tumor tracking was observed down to 2 minute scan times (RMS error = 1.9 ± 0.6 mm), while 1 minute scan times demonstrated a large spread in the error (RMS error = 2.4 ± 1.8 mm). Conclusion: This study suggests scan times down to two minutes are sufficient for the extraction of tumor motion trajectories from 4D CBCT images. Additionally, this study sets up the ability to compare other reconstruction methods to the traditional FDK method.
MO‐F‐WAB‐11: Investigation of CBCT‐Based Patient Positioning Accuracy in Lung SBRT: Correlation with Breathing Irregularity
Authors: Turner K , Zhang Y , Vergalasova I , Ren L , Segars P , Kelsey C , Yoo D , Yin F , Cai J
Published: July 2013

Purpose: To evaluate breathing irregularity induced error in CBCT‐based patient positioning in lung SBRT and correlate the error with a measure of breathing variability. Methods: The 4D extended cardiac‐torso (XCAT) digital phantom was used to generate 10‐phase 4DCT and CBCT images using in‐house developed simulation programs. Images were generated for various respiratory profiles (one regular sinusoidal and 10 irregular) and tumor sizes (1 cm, 2 cm, 3 cm). Maximum intensity projection (MIP) and average intensity projection (AIP) images were generated from 4DCT images. Image registrations between CBCT and AIP were performed for each respiratory profile and tumor size by four clinicians (two physicians and two physicists) based on target volume matching. Error of registration was determined as the difference between manual CBCT‐to‐AIP registration and known registration between the two. Breathing irregularities of the respiratory profiles were measured and correlated to errors of registration. Results: Inter‐observer variation of registration was 0.15 mm, 0.34 mm, and 0.69 mm, in the medial‐lateral (ML), anterior‐posterior (AP), and superior‐inferior (SI) direction, respectively. For the regular profile, negligible errors of registration were found in all directions (median<0.5 mm). For the irregular profiles and all tumor sizes, small errors (median=0.5 mm) were found in the ML and AP directions, while non‐trivial errors were seen in the SI direction (median (+/− SD): 2.10 (+/− 2.27) mm). No significant difference in mean error of registration was found for different tumor sizes (p>0.6). Maximum error of registration in the ML, AP, and SI direction was 1.2 mm, 2.6 mm, and 8.4 mm, respectively. Mild correlations (R2 range: 0.37 to 0.47) were observed between error of registration error and breathing irregularity for all tumor sizes. Conclusion: Irregular breathing can induce error in CBCT‐based image registration in lung SBRT. This error increases as the breathing irregularity increases.
MO‐F‐134‐03: Designing a Low Cost Digital Imaging System for Medical Physics Education
Authors: Brown C , Polf J
Published: July 2013

Purpose: Due to the increasing demand for trained Medical Physicists and increased interest in Medical Physics by students, many academic physics departments have begun to offer Medical Physics courses as well as graduate programs. To institute a new program, it helps to have feasible equipment that will provide hands on experience and teaching of the concepts central to Medical Physics. For example, clinical digital radiography systems are typically used for teaching the basic concepts of digital imaging. However, such systems can cost >$100,000, posing a financial barrier, and making alternatives to commercial systems desirable for most academic departments. The purpose of this work was to develop a low cost digital radiography system for teaching purposes using used or surplus materials. Methods and Materials:We first identified five essential components of a radiography system, namely, the x‐ray source, the detector, data acquisition, image display and processing, and radiation shielding/protection. We then acquired used or surplus items for each component. A lead‐lined wood box was built and each component installed to produce the imaging system. We then performed several basic commissioning tests to characterize the contrast, spatial resolution and noise of the acquired x‐ray images. Results: Our results show that the system is capable of producing digital x‐ray images with optimal spatial resolution and noise levels of 0.77mm and 4%, respectively. Characteristic contrast curves show adequate contrast is produced in the image over a wide range of material thicknesses and densities. Conclusion: These results show that an educational digital radiography system can be produced from cheap (or free) used/surplus items, thus fitting within the budgets of most academic physics departments. The design and construction of such a system has shown to be a great exercise for students learning the basics concepts of digital medical imaging systems. Department of Health and Human Services, Grant# D1ARH20090
TU‐A‐500‐01: Deformable Image Registration, Contour Propagation and Dose Mapping: 101 and 201
Authors: Kessler M , Pouliot J
Published: July 2013

Deformable image registration, contour propagation and dose mapping have become common, possibly essential tools for modern image‐guided radiation therapy. Historically, these tools have been largely developed at academic medical centers and used in a rather limited and well controlled fashion. Today these tools are now available to the radiotherapy community at large, both as stand‐alone applications and as integrated components of treatment planning and treatment delivery systems. Unfortunately, the details of how these tools work and their limitations are not generally documented or described by the vendors that provide them. Although “it looks right”, determining that unphysical deformations may have occurred is crucial. Because of this, understanding how and when to use, and not use these tools to support everyday clinical decisions is far from straight forward.The goal of this session will be to present both the theory (basic and advanced) and practical clinical use of deformable image registration, contour propagation and dose mapping. To the extent possible, the “secret sauce” that different vendor use to produce reasonable/acceptable results will be described. A detailed explanation of the possible sources of errors and actual examples of these will be presented. Knowing the underlying principles of the process and understanding the confounding factors will help the practicing medical physicist be better able to make decisions (about making decisions) using the tools available.

Learning Objectives:

1. Understand the basic (101) and advanced (201) principles of deformable image registration, contour propagation and dose mapping data mapping

2. Understand the sources and impact of errors in registration and data mapping and the methods for evaluating the performance of these tools

3. Understand the clinical use and value of these tools, especially when used as a “black box”
TU‐C‐500‐01: Evaluating Benefits and Challenges of Multi‐Modality Co‐Registration
Authors: Benedict S , Vedam S , Cai J , Wijesooriya K , Murphy M
Published: July 2013

Multi‐imaging modalities has afforded tremendous treatment planning opportunities to better define and delineate tumor volumes, and effectively apply highly conformal targeted therapy techniques such as IMRT and SBRT. With 4D CT imaging providing motion specifc information, PET yielding tumor molecular physiologic imaging, and MRI enhanced soft tissue diffentiation, these multi‐imaging modalities can introduce a comprehensive image of the planned target volumes. However, each of these technological innovations come with limitations specific to each image acquisition modality, and importing these various imaging studies into the planning system requires the employment of image registration tools, and in some case non‐rigid, deformation image registration, in order to successfully delineate tumor and target volumes for planning. This session will present strategies for management of tumor delineation using multi imaging modalities safely and effectively, including an overview of the benefits and pitfalls of tumor volume delineation using 4D CT, PET, MRI, and the various tools of deformation image registration.
TU‐C‐137‐01: Your First Job; Finding and Keeping It
Authors: Clements J , Tarver R
Published: July 2013

New members to the field of Medical Physics find themselves in a very competitive market and will benefit from guidance on job seeking skills, negotiating salary/benefits, what type of job to look for, etc. Additionally, expectations may be different between employer and employee, and an understanding of how the clinical environment works as well as how it is changing will help newly employed physicists excel at their job.

Learning Objectives:

1. To understand the job market and how to successfully perform a job search

2. To understand the importance of negotiating salary and benefits prior to employment

3. To understand the nuances of today's clinical environment and how it is changing, in order to more easily adapt and excel.
TU‐C‐108‐02: Novel Full 3D Water‐Equivalent Dosimetry Technique Using a Single Light‐Field Camera for Photons, Electrons and Ion‐Beams Dosimetry
Authors: Goulet M , Gingras L , Beddar S , Beaulieu L , Archambault L
Published: July 2013

Purpose: Using an array of micro‐lenses coupled with its active sensor, a light‐field camera samples the incoming optical photons in both the spatial and angular domain. This work presents the proof‐of‐concept and experimental validation of a 3D dosimeter based on the reconstruction of the light pattern emitted from a plastic scintillator volume and recorded using a light‐field camera. Using a single, fixed camera device, this technology enables real‐time, multi‐plane experimental measurement of static and dynamic radiotherapy delivery. Method: A Raytrix R5 light‐field camera was used to image a 10×10×10cm3 EJ‐260 plastic scintillator immersed in a water tank and irradiated with both square field and small MLC segments on a Clinac iX linear accelerator. The 3D light distribution emitted by the scintillator volume was reconstructed at a 5mm resolution in all dimensions by backprojecting the light collected by each pixel of the light‐field camera using a total variation minimization iterative reconstruction algorithm. Results: Signal contamination by Cerenkov emission was evaluated to less than 0.5% of the collected scintillation light for all field investigated, and as such Cerenkov light filtration was deemed unnecessary. Light‐field acquisition rate of at least 1 frame per second was achieved by the camera at a 600MU/min dose rate. The absolute dose difference between the reconstructed 3D dose and the expected dose calculated using the treatment planning software Pinnacle3 was on average below 3% for square fields and 5% for MLC segments in the high dose, low gradient region of each acquired field. Conclusions: Millimeter resolution dosimetry over an entire 3D volume is achievable in real‐time using a single light‐field camera. Because no moving parts are required in the dosimeter, the incident dose distribution can be acquired as a function of time, thus enabling the validation of static and dynamic radiation delivery with photons, electrons and ions.
TU‐C‐108‐05: High Density Organic Scintillator Arrays for High Resolution Stereotactic Body Radiation Therapy Dosimetry
Authors: Izaguirre EW , Yaddanapudi S , Price S , Wooten H , Rangaraj D
Published: July 2013

Purpose: Radiation oncology patients receiving stereotactic body radiation therapy (SBRT) are treated with high dose and high dose rate treatment procedures in which delivered dose should be recorded, and verified for quality assurance and patient safety. We implemented a high resolution scintillating fiber detector array to perform high resolution dosimetry of SBRT fields. Materials: Scintillating fibers have a water equivalent attenuation coefficient, excellent reproducibility, stability and a linear response versus dose, do not require any polarizing voltage, and are water impermeable. We constructed a high resolution dosimeter based on an array of sub‐millimeter organic fiber sensors mounted on a supporting frame that provides support, alignment, and buildup material. The fiber detector interface consists of a high density linear array of high speed linear photodetectors. The analog output is transmitted to a high throughput parallel data acquisition system integrated with a dedicated computer for signal processing, analysis, and recording. The detector was specially designed to perform high resolution dosimetric verification of small SBRT fields delivered with conventional dose rates (600 MU/min) to high dose rate flattening filter free beams (up to 2400 MU/min). Results: We determined fiber sensor sensitivity and linearity response with respect to beam intensity field size and dose. Detector spatial resolution is 0.5 mm and linearity response with respect to beam intensity and field size was within 2% for photon beams from 6MV to 18 MV and electron beams from 6 MeV to 20 MeV. Spatial beam profiles were compared with film dosimetry showing excellent agreement within 3% in the penumbra region. Conclusions: The development of this technology addresses the need for high resolution dosimeters for SBRT. The developed detector provides accurate dose, beam localization, and beam profile verification and will be a valuable tool for quality assurance of SBRT treatments.
TU‐C‐108‐06: Performance of KCl:Eu2+ Storage Phosphor Dosimeters for Low Dose Measurements
Authors: Xiao Z , Hansel R , Knutson N , Yang D , Li H
Published: July 2013

Purpose: Recent research has demonstrated that europium doped potassium chloride (KCl:Eu2+) storage phosphor material has the potential to become the physical foundation of a novel and reusable dosimetry system using either film‐like devices or devices similar to thermoluminescent dosimeter chips. In this work, we will quantify the low dose detection resolution of the KCl:Eu2+ prototype dosimeter and demonstrate how it can be incorporated into clinical application for in vivo peripheral dose measurements. Methods: The prototype KCl:Eu2+ dosimeters used in this study were manufactured according to standard materials processes, and had a physical makeup similar to thermoluminescent dosimeter chips. The lowest dose‐to‐water of 0.01 cGy in this work was achieved underneath a fully closed multileaf collimator at a source‐to‐surface distance of ∼200 cm. For doses greater than 100 Gy, prototype dosimeters were irradiated using the XRLM4 beamline at the Center for Advanced Mircrostructure and Devices synchrotron facility at Louisiana State University in Baton Rouge, LA. To compare sensitivity, two commercial storage phosphor detectors were also irradiated under the same conditions. The dosimeters were read using a laboratory photostimulated luminescence detection system. Results: KCl:Eu2+ prototype storage phosphor dosimeter is capable of measuring a dose‐to‐water as low as 0.01 cGy from a 6MV photon beam with a signal‐to‐noise ratio greater than 6. Agfa MD10, Fuji STIII and KCl:Eu2+ prototypes were within 10% in sensitivity. A pre‐readout thermal annealing procedure enables the dosimeter to be read within an hour post irradiation. The dosimeter retains a constant response after receiving large accumulated doses (∼10 kGy). The energy‐dependence encountered during low dose peripheral measurements can be accounted for via a single point outside‐field calibration per each beam quality. Conclusions: With further development the KCl:Eu2+− based dosimeter could become a versatile and durable dosimetry tool with large dynamic range (sub‐cGy to 100 Gy). This work was supported in part by NIH Grant No. R01CA148853.
TU‐C‐108‐07: Transmission Detector Array System for RT Delivery Monitoring: Validation Testing
Authors: Li T , Wu Q Jackie , Matzen T , O' Daniel J
Published: July 2013

Purpose: To quantify the influence of the gantry‐mounted Delta4‐AT detector array on beam quality, and the detection sensitivity to machine output and MLC position deviations. Methods: A Delta4‐AT prototype was attached to the accessory holder mount of a Varian 21EX linear accelerator. The system utilizes an array of ∼4,000 transmission diodes (40 per MLC leaf, every 2.5mm along the direction of motion) to measure the fluence of photon beams during treatment deliveries. To quantify the influence from the detector array on beam quality, the percentage depth dose curves were measured with an IBA PFD3G diode in water and compared between with and without detector array. A static field with comb‐shaped MLC pattern was used to evaluate the systems ability to detect machine output and MLC position deviations. 1–5% MU deviations and 1–5 mm MLC offsets were introduced to the static plan. The modified plans were then delivered and the measurements by Delta4‐AT were compared to the original delivery. Results: For the 6MV beam tested in this study, the transmission reduction due to the presence of the detector array is ∼1% at both dmax and 10 cm depths for multiple field sizes. The skin dose measured at 1mm depth increases by < 0.5% relative to dose at dmax for field sizes up to 10cm, and by 4% and 7% for 20×20cm and 34×34cm fields, respectively. For plans with introduced MU deviations, the detected MU errors matched the planned errors within 0.8%. MLC position errors of 1‐5 mm are also identifiable through measured dose profiles by Delta4‐AT. The measured leaf position deviation is within 0.5 mm from the actual offsets introduced. Conclusion: The prototype Delta4‐AT transmission detector array has small influence on the beam quality, and successfully detected machine output deviations and MLC position offsets as low as 1% and 1mm, respectively.

This research was partially supported by a grant from Scandidos Inc.
TU‐C‐108‐09: What VMAT Delivery Errors Can Be Detected with Commercial Dosimetric Systems? ‐ A Comparison of Three Dosimetric Systems
Authors: Arumugam S , Young T , Xing A , Holloway L
Published: July 2013

Purpose: To study the sensitivity of three commercial dosimetric systems MULTIcube (MatriXX Evolution), ArcCHECK and Octavius‐4D, in detecting errors during the delivery of Volumetric Modulated Arc Therapy (VMAT). Methods: A simple VMAT arc with 111 Control‐Points (CP) was created in Pinnacle using a 6MV photon beam model for an Elekta‐Synergy accelerator. The aperture size for each CP was set to 5 × 10 cm2 and equal weights were assigned to all CPs. Three error scenarios considering Multi Leaf Collimator (MLC) position and dose delivery were simulated: Type1: Systematic shift in MLC position (from 1mm to 5mm) to the whole arc and systematic variation in output (from 1% to 10%) to the whole arc, Type2: Sag in MLC position as a function of gantry angle (amplitude ranging from 1mm to 5mm) and output variation as a function of gantry angle (amplitude ranging from 1% to 10%), Type3: MLC and output errors (ranging from 1mm to 10mm and 1% to 100% respectively) introduced to only two of the CPs. The difference in gamma (γ) pass rate between the error‐free and error‐simulated measurements with 2%/2mm tolerance was calculated to assess the sensitivity of dosimetric systems in detecting errors. Results: All three dosimetric systems detected type1 error. The γ pass rate reduced gradually as the error value increased beyond 2%/2mm tolerance. The MULTIcube system failed to detect the type2 errors whereas the γ pass rate in ArcCHECK and Octavius measurements decreased as the simulated error value increased. For type3 errors MULTIcube and Octavius measurements showed no change in pass rate whereas Arccheck measurements showed 5.9% and 2.6% decrease in pass rate at 10mm MLC error and 100% dose error respectively. Conclusion: ArcCHECK was shown to be sensitive to all types of simulated error. MULTIcube showed the least sensitivity, detecting only systematic errors in whole arc
TU‐C‐108‐11: A Novel Optical Calorimeter Applied to Proton Beam Dosimetry
Authors: Cavan A , Meyer J
Published: July 2013

Purpose: To demonstrate the proof‐of‐principle and feasibility of a novel optical calorimeter to determine radiation absorbed dose to water of a proton beam. Methods: The rise in temperature resulting from irradiation of a medium can be exploited by the use of a laser optics technique, named digital holographic interferometry (DHI). DHI can detect miniscule temperature changes in a transparent medium by measuring the corresponding change in the refractive index. A prototype of a lensless Fourier Transform digital holography (LFTDH) interferometer was developed and applied to the University of Washington experimental 30 MeV proton beam of 2 mm width. The output of the interferometer was digitally reconstructed and mathematically converted to absorbed dose through the calorimetric equations, resulting in a time series of high resolution two dimensional maps of absorbed dose. Results: The measurements qualitatively revealed the Bragg peak and relative dose profiles across the beam, in 2D dose maps with dimensions of ∼6 × 8 mm (defined by the area of the optoelectronic sensor used). Heat diffusion within the water sample caused a blurring effect on the determined dose profiles but this can be accounted for by use of the heat equation. Experimental noise can further be reduced by improved isolation from the ambient conditions. Conclusion: A prototype DHI detector has been developed and shown to resolve small temperature changes resulting from irradiation of a water sample with a high dose rate proton beam. The results are high resolution (25 pixels/mm) and independent of beam type, energy and dose rate. These results present a proof‐of‐principle of DHI detectors and indicate the feasibility of the approach for high dose rate dosimetry applications. Alicia Cavan acknowledges support from a Claude McCarthy fellowship (Universities New Zealand) for the proton beam research.