bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐F‐SPS‐10: The Dosimetric Comparison of GammaKnife and Cyberknife Treatment Plans for Brain SRS Treatment
Authors: Sanli E , Mabhouti H , Cebe M , Codel G , Pacaci P , Serin E , Kucuk N , Kucukmorkoc E , Doyuran M , Canoglu D , Altinok A , Acar H , Caglar Ozkok H
Published: July 2016

Purpose:

Brain stereotactic radiosurgery (SRS) involves the use of precisely directed, single session radiation to create a desired radiobiologic response within the brain target with acceptable minimal effects on surrounding structures or tissues. In this study, the dosimetric comparison of GammaKnife perfection and Cyberknife M6 treatment plans were made.

Methods:

Treatment plannings were done for GammaKnife perfection unit using Gammaplan treatment planning system (TPS) on the CT scan of head and neck randophantom simulating the treatment of sterotactic treatments for one brain metastasis. The dose distribution were calculated using TMR 10 algorithm. The treatment planning for the same target were also done for Cyberknife M6 machine using Multiplan (TPS) with Monte Carlo algorithm. Using the same film batch, the net OD to dose calibration curve was obtained using both machine by delivering 0‐ 800 cGy. Films were scanned 48 hours after irradiation using an Epson 1000XL flatbed scanner. Dose distribution were measured using EBT3 film dosimeter. The measured and calculated doses were compared.

Results:

The dose distribution in the target and 2 cm beyond the target edge were calculated on TPSs and measured using EBT3 film. For cyberknife treatment plans, the gamma analysis passing rates between measured and calculated dose distributions were 99.2% and 96.7% for target and peripheral region of target respectively. For gammaknife treatment plans, the gamma analysis passing rates were 98.9% and 93.2% for target and peripheral region of target respectively.

Conclusion:

The study shows that dosimetrically comparable plans are achievable with Cyberknife and GammaKnife. Although TMR 10 algorithm predicts the target dose
SU‐F‐SPS‐11: The Dosimetric Comparison of Truebeam 2.0 and Cyberknife M6 Treatment Plans for Brain SRS Treatment
Authors: Mabhouti H , Sanli E , Cebe M , Codel G , Pacaci P , Serin E , Kucuk N , Kucukmorkoc E , Doyuran M , Canoglu D , Altinok A , Acar H , Caglar Ozkok H
Published: July 2016

Purpose:

Brain stereotactic radiosurgery involves the use of precisely directed, single session radiation to create a desired radiobiologic response within the brain target with acceptable minimal effects on surrounding structures or tissues. In this study, the dosimetric comparison of Truebeam 2.0 and Cyberknife M6 treatment plans were made.

Methods:

For Truebeam 2.0 machine, treatment planning were done using 2 full arc VMAT technique with 6 FFF beam on the CT scan of Randophantom simulating the treatment of sterotactic treatments for one brain metastasis. The dose distribution were calculated using Eclipse treatment planning system with Acuros XB algorithm. The treatment planning of the same target were also done for Cyberknife M6 machine with Multiplan treatment planning system using Monte Carlo algorithm. Using the same film batch, the net OD to dose calibration curve was obtained using both machine by delivering 0‐ 800 cGy. Films were scanned 48 hours after irradiation using an Epson 1000XL flatbed scanner. Dose distribution were measured using EBT3 film dosimeter. The measured and calculated doses were compared.

Results:

The dose distribution in the target and 2 cm beyond the target edge were calculated on TPSs and measured using EBT3 film. For cyberknife plans, the gamma analysis passing rates between measured and calculated dose distributions were 99.2% and 96.7% for target and peripheral region of target respectively. For Truebeam plans, the gamma analysis passing rates were 99.1% and 95.5% for target and peripheral region of target respectively.

Conclusion:

Although, target dose distribution calculated accurately by Acuros XB and Monte Carlo algorithms, Monte carlo calculation algorithm predicts dose distribution around the peripheral region of target more accurately than Acuros algorithm.
SU‐F‐E‐01: Pitfalls: Reliability and Performance of Diagnostic X‐Sources
Authors: Behling R
Published: July 2016

Purpose:

Performance and reliability of medical X‐ray tubes for imaging are crucial from an ethical, clinical and economic perspective. This lecture will deliver insight into the aspects to consider during the decision making process to invest in X‐ray imaging equipment. Outdated metric still hampers realistic product comparison. It is time to change this and to comply with latest standards, which consider current technology. Failure modes and ways to avoid down‐time of the equipment shall be discussed. In view of the increasing number of interventional procedures and the hazards associated with ionizing radiation, toxic contrast agents, and the combination thereof, the aspect of system reliability is of paramount importance.

Methods:

A comprehensive picture of trends for different modalities (CT, angiography, general radiology) has been drawn and led to the development of novel X‐ray tube technology.

Results:

Recent X‐ray tubes feature enhanced reliability and unprecedented performance. Relevant metrics for product comparison still have to be implemented in practice.

Conclusion:

The speed of scientific and industrial development of new diagnostic and therapeutic X‐ray sources remains tremendous. Still, users suffer from gaps between desire and reality in day‐to‐day diagnostic routine. X‐ray sources are still limiting cutting‐edge medical procedures. Side‐effects of wear and tear, limitations of the clinical work flow, costs, the characteristics of the X‐ray spectrum and others topics need to be further addressed. New applications and modalities, like detection‐based color‐resolved X‐ray and phase‐contrast / dark‐field imaging will impact the course of new developments of X‐ray sources.

The author is employee of Royal Philips
SU‐F‐E‐03: PET/CT Guided Dose Boost to Hypoxic Sub‐Volume in Nasopharyngeal Carcinomas Using Self‐Optimizing Non‐Uniform VMAT
Authors: Qiu J , Zheng X , Liu H , Chen B , Zhuo W
Published: July 2016

Purpose:

This study is to evaluate the feasibility of simultaneously integrated boost (SIB) to hypoxic subvolume (HTV) in nasopharyngeal carcinomas under the guidance of 18F‐Fluoromisonidazole (FMISO) PET/CT using a novel non‐uniform volumetric modulated arc therapy (VMAT)technique.

Methods:

Eight nasopharyngeal carcinoma patients treated with conventional uniform VMAT were retrospectively analyzed. For each treatment, actual conventional uniform VMAT plan with two or more arcs (2–2.5 arcs, totally rotating angle < 1000o) was designed with dose boost to hopxic subvolume (total dose, 84Gy) in the gross tumor volme (GTV) under the guidance of 18F‐ FMISO PET/CT. Based on the same dataset, experimental single arc non‐uniform VAMT plans were generated with the same dose prescription using customized software tools. Dosimetric parameters, quality assurance and the efficiency of the treatment delivery were compared between the uniform and non‐uniform VMAT plans.

Results:

To develop the non‐uniform VMAT technique, a specific optimization model was successfully established. Both techniques generate high‐quality plans with pass rate (>98%) with the 3mm, 3% criterion. HTV received dose of 84.1±0.75Gy and 84.1±1.2Gy from uniform and non‐uniform VMAT plans, respectively. In terms of target coverage and dose homogeneity, there was no significant statistical difference between actual and experimental plans for each case. However, for critical organs at risk (OAR), including the parotids, oral cavity and larynx, dosimetric difference was significant with better dose sparing form experimental plans. Regarding plan implementation efficiency, the average machine time was 3.5 minutes for the actual VMAT plans and 3.7 minutes for the experimental nonuniform VMAT plans (p>0.050).

Conclusion:

Compared to conventional VMAT technique, the proposed non‐uniform VMAT technique has the potential to produce efficient and safe treatment plans, especially in cases with complicated anatomical structures and demanding dose boost to subvolumes.
SU‐F‐E‐05: Determination of Breakeven Points of in Vitro Meats and in Vivo Mice Based On Tissue Temperature Enhancement Pattern
Authors: Austerlitz C , Barros A , Gkigkitzis I , Haranas I , Zhu D , Campos D
Published: July 2016

Purpose:

To determine the breakeven points in fresh commercial meat and in vivo mice using the tissue temperature enhancement pattern.

Methods:

A 1 cm length and 0.1 cm diameter gold rod were implanted in fresh chicken breast, beef, fish, in vivo Mus Musculus white mice (medial dorsal region) and insonated with ultrasound. The temperature enhancement of gold rods was measured with a needle type thermistor over a temperature range from 35–50 oC. From these results the breakeven points were determined by plotting the gold rod temperature versus ultrasound exposure time and determining the interception point of two curves fitted by a linear regression of thermal response above and below 43 °C.

Results:

The linear correlation coefficients for all fitted curves lie within 0.97 and 0.99. The breakeven points were found to be the same for all kinds of fresh meat (fish = 42.1 ±1.1, chicken breast = 42.3 ±0.9, beef = 42.6 ±0.8) and in vivo Mus Musculus white mice (43.3 ±0.6). These temperatures agree with the standardized value (e.g. equivalent minutes at 43 °C) for comparison of thermal treatments (Proc. SPIE Int. Soc. Opt. Eng. 2003 June 2; 4954: 37).

Conclusion:

The interception of the thermal response curves above and below 43 °C may be used as a fast method and useful dosimetric tool in clinical research.
SU‐F‐E‐08: Medical Physics as a Teaching Tool for High School Science Curriculum
Authors: Buckley L
Published: July 2016

Purpose:

Delivering high school science curriculum in a timely manner and in way that is accessible to all students is a challenge for teachers. Although many high schools offer career workshops, these are typically directed at senior students and do not relate directly to details of the curriculum. The objective of this initiative was to create a series of lectures that use medical physics to relate many aspects of the high school science curriculum to tangible clinical applications and to introduce students to alternate pathways into a career in health sciences.

Methods:

A series of lectures has been developed based on the Ontario High School Science Curriculum. Each lecture uses a career in radiotherapy medical physics as the framework for discussion of topics specific to the high school course being addressed.

Results:

At present, these lectures have been delivered in five area high schools to students ranging from sophomores to seniors. Survey documents are given to the students before and after the lecture to assess their awareness of careers in health care, applications of physics and their general interest in the subject areas. As expected, students have limited up front awareness of the wide variety of health related career paths. The idea of combining a career lecture with topics specific to the classroom curriculum has been well‐received by teachers and students alike.

Conclusion:

Career talks for high school students are useful for students contemplating their post‐ secondary career path. Relating career discussion with direct course curriculum makes their studies more relevant and engaging. Students aspiring to a career in health sciences often focus their studies on life sciences due to limited knowledge of potential careers. An early introduction to medical physics presents them with an alternate path through the physical sciences into health care.
SU‐F‐E‐15: Initial Experience Implementing a Case Method Teaching Approach to Radiation Oncology Physics Residents, Graduate Students and Doctorate of Medical Physics Students
Authors: Gutierrez A
Published: July 2016

Purpose:

Case Method Teaching approach is a teaching tool used commonly in business school to challenge students with real‐world situations—i.e. cases. The students are placed in the role of the decision maker and have to provide a solution based on the multitude of information provided. Specifically, students must develop an ability to quickly make sense of a complex problem, provide a solution incorporating all of the objectives (at time conflicting) and constraints, and communicate that solution in a succinct, professional and effective manner. The validity of the solution is highly dependent on the auxiliary information provided in the case and the basic didactic knowledge of the student. A Case Method Teaching approach was developed and implemented into an on‐going course focused on AAPM Task Group reports at UTHSCSA.

Methods:

A current course at UTHSCSA reviews and discusses 15 AAPM Task Group reports per semester. The course is structured into three topic modules: Imaging QA, Stereotactic Radiotherapy, and Special Patient Measurements—i.e. pacemakers, fetal dose. After a topic module is complete, the students are divided into groups (2–3 people) and are asked to review a case study related to the module topic. Students then provide a solution presented in an executive summary and class presentation.

Results:

Case studies were created to address each module topic. Through team work and whole‐class discussion, a collaborative learning environment was established. Students additionally learned concepts such vendor relations, financial negotiations, capital project management, and competitive strategy.

Conclusion:

Case Method Teaching approach is an effective teaching tool to further enhance the learning experience of radiation oncology physics students by presenting them with though‐provoking dilemmas that require students to distinguish pertinent from peripheral information, formulate strategies and recommendations for action, and confront obstacles to implementation.
SU‐F‐E‐16: A Specific Training Package for Medical Physicists in Support to Nuclear and Radiological Emergency Situations
Authors: Meghzifene A , Berris T
Published: July 2016

Purpose:

To provide the professional medical physicists with adequate competencies and skills in order to help them get prepared to support Nuclear or Radiological Emergency (NRE) situations.

Methods:

Although clinical medical physicists working have in‐depth knowledge in radiation dosimetry, including dose reconstruction and dose measurements, they are usually not involved in NRE situations. However, in a few instances where medical physicists were involved in NREs, it appeared that many lacked specific knowledge and skills that are required in such situations. This lack of specific knowledge and skills is probably due to the fact that most current medical physics curricula do not include a specific module on this topic. As a response to this finding, the IAEA decided to initiate a project to develop a specific training package to help prepare medical physicists to support NRE situations. The training package was developed with the kind support of the Government of Japan and in collaboration with Fukushima Medical University (FMU) and the National Institute of Radiological Sciences (NIRS).

Results:

The first International Workshop to test the training package was held in Fukushima, Japan in June 2015. It consisted of lectures, demonstrations, simulation, role play, and practical sessions followed by discussions. The training was delivered through 14 modules which were prepared with the support of 12 lecturers. A knowledge assessment test was done before the workshop, followed by the same test done at the end of the Workshop, to assess the knowledge acquired during the training.

Conclusion:

The Workshop was successfully implemented. The overall rating of the workshop by the participants was excellent and all participants reported that they acquired a good understanding of the main issues that are relevant to medical physics support in case of NRE situations. They are expected to disseminate the knowledge to other medical physicists in their countries.
SU‐F‐E‐18: Training Monthly QA of Medical Accelerators: Illustrated Instructions for Self‐Learning
Authors: Court L , Brown D , Wang H , Maddox B , Aten D , MacGregor H , Chi P , Yock A , Gao S , Aristophanous M , Balter P
Published: July 2016

Purpose:

To develop and test clear illustrated instructions for training of monthly mechanical QA of medical linear accelerators.

Methods:

Illustrated instructions were created for monthly mechanical QA with tolerance tabulated, and underwent several steps of review and refinement. Testers with zero QA experience were then recruited from our radiotherapy department (1 student, 2 computational scientists and 8 dosimetrists). The following parameters were progressively de‐calibrated on a Varian C‐series linac: Group A = gantry angle, ceiling laser position, X1 jaw position, couch longitudinal position, physical graticule position (5 testers); Group B = Group A + wall laser position, couch lateral and vertical position, collimator angle (3 testers); Group C = Group B + couch angle, wall laser angle, and optical distance indicator (3 testers). Testers were taught how to use the linac, and then used the instructions to try to identify these errors. A physicist observed each session, giving support on machine operation, as necessary. The instructions were further tested with groups of therapists, graduate students and physics residents at multiple institutions. We have also changed the language of the instructions to simulate using the instructions with non‐English speakers.

Results:

Testers were able to follow the instructions. They determined gantry, collimator and couch angle errors within 0.4, 0.3, and 0.9degrees of the actual changed values, respectively. Laser positions were determined within 1mm, and jaw positions within 2mm. Couch position errors were determined within 2 and 3mm for lateral/longitudinal and vertical errors, respectively. Accessory positioning errors were determined within 1mm. ODI errors were determined within 2mm when comparing with distance sticks, and 6mm when using blocks, indicating that distance sticks should be the preferred approach for inexperienced staff.

Conclusion:

Inexperienced users were able to follow these instructions, and catch errors within the criteria suggested by AAPM TG142 for linacs used for IMRT.
SU‐F‐E‐19: A Novel Method for TrueBeam Jaw Calibration
Authors: Corns R , Zhao Y , Huang V
Published: July 2016

Purpose:

A simple jaw calibration method is proposed for Varian TrueBeam using an EPID‐Encoder combination that gives accurate fields sizes and a homogeneous junction dose. This benefits clinical applications such as mono‐isocentric half‐beam block breast cancer or head and neck cancer treatment with junction/field matching.

Methods:

We use EPID imager with pixel size 0.392 mm × 0.392 mm to determine the radiation jaw position as measured from radio‐opaque markers aligned with the crosshair. We acquire two images with different symmetric field sizes and record each individual jaw encoder values. A linear relationship between each jaw's position and its encoder value is established, from which we predict the encoder values that produce the jaw positions required by TrueBeam's calibration procedure. During TrueBeam's jaw calibration procedure, we move the jaw with the pendant to set the jaw into position using the predicted encoder value. The overall accuracy is under 0.1 mm.

Results:

Our in‐house software analyses images and provides sub‐pixel accuracy to determine field centre and radiation edges (50% dose of the profile). We verified the TrueBeam encoder provides a reliable linear relationship for each individual jaw position (R2>0.9999) from which the encoder values necessary to set jaw calibration points (1 cm and 19 cm) are predicted. Junction matching dose inhomogeneities were improved from >±20% to <±6% using this new calibration protocol. However, one technical challenge exists for junction matching, if the collimator walkout is large.

Conclusion:

Our new TrueBeam jaw calibration method can systematically calibrate the jaws to crosshair within sub‐pixel accuracy and provides both good junction doses and field sizes. This method does not compensate for a larger collimator walkout, but can be used as the underlying foundation for addressing the walkout issue.
SU‐F‐E‐20: A Mathematical Model of Linac Jaw Calibration Integrated with Collimator Walkout
Authors: Zhao Y , Corns R , Huang V
Published: July 2016

Purpose:

Accurate jaw calibration is possible, but it does not necessarily achieve good junctions because of collimator rotation walkout. We developed a mathematical model seeking to pick an origin for calibration that minimizes the collimator walkout effect.

Methods:

We use radioopaque markers aligned with crosshair on the EPID to determine the collimator walkout at collimator angles 0°, 90° and 270°. We can accurately calibrate jaws to any arbitrary origin near the radiation field centre. While the absolute position of an origin moves with the collimator walkout, its relative location to the crosshair is an invariant. We studied two approaches to select an optimal origin. One approach seeks to bring all three origin locations (0°–90°–270°) as close as possible by minimizing the perimeter of the triangle formed by these points. The other approach focuses on the gap for 0°–90° junctions.

Results:

Our perimeter cost function has two variables and non‐linear behaviour. Generally, it does not have zero‐perimeter‐length solution which leads to perfect jaw matches. The zero solution can only be achieved, if the collimator rotates about a single fixed axis. In the second approach, we can always get perfect 0°–0° and 0°–90° junctions, because we ignore the 0°–270° situation. For our TrueBeams, both techniques for selecting an origin improved junction dose inhomogeneities to less than ±6%.

Conclusion:

Our model considers the general jaw matching with collimator rotations and proposes two potential solutions. One solution optimizes the junction gaps by considering all three collimator angles while the other only considers 0°–90°. The first solution will not give perfect matching, but can be clinically acceptable with minimized collimator walkout effect, while the second can have perfect junctions at the expense of the 0°–270° junctions. Different clinics might choose between these two methods basing on their clinical practices.
SU‐F‐P‐05: Initial Experience with an Independent Certification Program for Stereotactic Radiosurgery and Stereotactic Body Radiation Therapy
Authors: Solberg T , Robar J , Gevaert T , Todorovic M , Howe J
Published: July 2016

Purpose:

The ASTRO document “Safety is no accident: A FRAMEWORK FOR QUALITY RADIATION ONCOLOGY AND CARE” recommends external reviews of specialized modalities. The purpose of this presentation is to describe the implementation of such a program for Stereotactic Radiosurgery (SRS) and Stereotactic Body radiation Therapy (SBRT).

Methods:

The margin of error for SRS and SBRT delivery is significantly smaller than that of conventional radiotherapy and therefore requires special attention and diligence. The Novalis Certified program was created to fill an unmet need for specialized SRS / SBRT credentialing. A standards document was drafted by a panel of experts from several disciplines, including medical physics, radiation oncology and neurosurgery. The document, based on national and international standards, covers requirements in program structure, personnel, training, clinical application, technology, quality management, and patient and equipment QA. The credentialing process was modeled after existing certification programs and includes an institution‐generated self‐study, extensive document review and an onsite audit. Reviewers generate a descriptive report, which is reviewed by a multidisciplinary expert panel. Outcomes of the review may include mandatory requirements and optional recommendations.

Results:

15 institutions have received Novalis Certification, including 3 in the US, 7 in Europe, 4 in Australia and 1 in Asia. 87 other centers are at various stages of the process. Nine reviews have resulted in mandatory requirements, however all of these were addressed within three months of the audit report. All reviews have produced specific recommendations ranging from programmatic to technical in nature. Institutions felt that the credentialing process addressed a critical need and was highly valuable to the institution.

Conclusion:

Novalis Certification is a unique peer review program assessing safety and quality in SRS and SBRT, while recognizing international practice standards. The approach is capable of highlighting outstanding requirements and providing recommendations to enhance both new and established programs.

Timothy Solberg is co‐owner of Global Radiosurgery services, LLC
SU‐F‐P‐15: Report On AAPM TG 178 Gamma Knife Dosimetry and Quality Assurance
Authors: Goetsch S
Published: July 2016

Purpose:

AAPM Task Group 178 Gamma Stereotactic Radiosurgery Dosimetry and Quality Assurance was formed in August, 2008. The Task Group has 12 medical physicists, two physicians and two consultants.

Methods:

A round robin dosimetry intercomparison of proposed ionization chambers, electrometer and dosimetry phantoms was conducted over a 15 month period in 2011 and 2012 (Med Phys 42, 11, Nov, 2015). The data obtained at 9 institutions (with ten different Elekta Gamma Knife units) was analyzed by the lead author using several protocols.

Results:

The most consistent results were obtained using the Elekta ABS 16cm diameter phantom, with the TG‐51 protocol modified as recommended by Alfonso et al (Med Phys 35, 11, Nov 2008). A key white paper (Med Phys, in press) sponsored by Elekta Corporation, was used to obtain correction factors for the ionization chambers and phantoms used in this intercomparison. Consistent results were obtained for both Elekta Gamma Knife Model 4C and Gamma Knife Perfexion units as measured with each of two miniature ionization chambers

Conclusion:

The full TG 178 report gives clinical history and background of gamma stereotactic radiosurgery, clinical examples and history, quality assurance recommendations and outline of possible dosimetry protocols. The report will be reviewed by the AAPM Working Group on Recommendations for Radiotherapy External Beam Quality Assurance and then by the AAPM Science Council before publication in Medical Physics.

Consultant to Elekta, Inc
SU‐F‐P‐16: Improving the MedPhys Match and Interview Process: Results From An Independent Survey of Applicants and Programs
Authors: Rodrigues A , Juang T , Vimolchalao S , Burmeister J , Hendrickson K
Published: July 2016

Purpose:

To provide recommendations from applicants and program directors on improving the Medical Physics Residency Matching Program (the “MedPhys” Match) and the associated interview process.

Methods:

A survey gauging interview and match experience was emailed to all applicants and program directors registered for the inaugural 2014/15 MedPhys Match. Detailed questions included satisfaction with the match experience, logistics and cost of interviewing for applicants, and specific suggestions to improve the match.

Results:

109 out of 402 applicants and 42 out of 77 programs completed the surveys. Of these applicants, 92 submitted rankings and 52 matched. 77% of matched applicants and only 7% of unmatched applicants were satisfied with the experience. Generally, 15% of applicants stated that the match needs no improvement, while 79% stated that it could use minor or major improvement. Primary suggestions from applicants included coordination of interviews into geographic regions and a fixed date by which interview invitations/dates are announced. 98% of programs were satisfied with the experience, with 75% stating that no improvements are needed, and 25% stating that the match could use minor improvement. Suggestions from programs included coordination of interviews in geographic locations, an earlier match date, and quicker turnaround on offer acceptances.

Conclusion:

Overall, matched applicants were satisfied and programs were very satisfied with the match experience. It is unclear whether the dissatisfaction among unmatched applicants is largely attributable to the process itself or to the fact that they may be shut out of the board certification process. Since a majority (79%) of applicants but only a minority (25%) of programs felt that the current match requires minor or major improvement, our applicants should be considered a valuable source of suggestions for improvement. Addressing these concerns early on may lead to more transparency and an improved experience for applicants and programs.
SU‐F‐P‐17: Making the Match: Selection Factors in the Medical Physics Residency Match
Authors: Juang T , Rodrigues A , Vimolchalao S , Burmeister J , Hendrickson K
Published: July 2016

Purpose:

To provide information on selection factors in the medical physics residency match process to assist both residency programs and future applicants in successfully matching with their preferred choices.

Methods:

A survey on the medical physics residency match and interview process, including questions regarding specific major and minor considerations for interview selection and match ranking, was emailed to all applicants and residency program directors registered in the 2015 MedPhys Match.

Results:

Survey respondents included 109 (27%) applicants and 42 (54%) program directors. Of the applicant respondent pool, 85% received interviews and 48% matched to a residency. These matched respondents also represent 48% of the 108 matched applicants from the 2015 cycle. Primary factors influencing applicants’ ranking of residency programs were location (69%), work environment (62%), and program structure (59%). Major considerations of residency programs in selecting candidates for interview were quality and content of reference letters (85%), personality fit (71%), and graduate program reputation (68%). The most influential factors in final candidate rankings, both of which were cited by all respondents, were impressions from the interview (94% as a major reason) and personality fit (80% as a major reason). Responses from program directors showed that candidates who communicated how they would rank a program did not improve their ranking. 32% of program directors indicated that they may consider post‐interview communication from a candidate's mentor or another advocate in that candidate's ranking.

Conclusion:

While many factors influence candidate selection for interview and ranking, future applicants can benefit from the results presented here: first in selecting a well‐regarded medical physics graduate program, then performing at a level that earns strong recommendation letters, and finally developing interview and interpersonal skills. Residency programs will make themselves most attractive to their top candidates by fostering a desirable work environment and developing a well‐organized training program.
SU‐F‐P‐18: Development of the Technical Training System for Patient Set‐Up Considering Rotational Correction in the Virtual Environment Using Three‐Dimensional Computer Graphic Engine
Authors: Imura K , Fujibuchi T , Kaneko K , Hamada E , Hirata H
Published: July 2016

Purpose:

Patient set‐up skills in radiotherapy treatment room have a great influence on treatment effect for image guided radiotherapy. In this study, we have developed the training system for improving practical set‐up skills considering rotational correction in the virtual environment away from the pressure of actual treatment room by using three‐dimensional computer graphic (3DCG) engine.

Methods:

The treatment room for external beam radiotherapy was reproduced in the virtual environment by using 3DCG engine (Unity). The viewpoints to perform patient set‐up in the virtual treatment room were arranged in both sides of the virtual operable treatment couch to assume actual performance by two clinical staffs. The position errors to mechanical isocenter considering alignment between skin marker and laser on the virtual patient model were displayed by utilizing numerical values expressed in SI units and the directions of arrow marks. The rotational errors calculated with a point on the virtual body axis as the center of each rotation axis for the virtual environment were corrected by adjusting rotational position of the body phantom wound the belt with gyroscope preparing on table in a real space. These rotational errors were evaluated by describing vector outer product operations and trigonometric functions in the script for patient set‐up technique.

Results:

The viewpoints in the virtual environment allowed individual user to visually recognize the position discrepancy to mechanical isocenter until eliminating the positional errors of several millimeters. The rotational errors between the two points calculated with the center point could be efficiently corrected to display the minimum technique mathematically by utilizing the script.

Conclusion:

By utilizing the script to correct the rotational errors as well as accurate positional recognition for patient set‐up technique, the training system developed for improving patient set‐up skills enabled individual user to indicate efficient positional correction methods easily.
SU‐F‐P‐19: Fetal Dose Estimate for a High‐Dose Fluoroscopy Guided Intervention Using Modern Data Tools
Authors: Moirano J
Published: July 2016

Purpose:

An accurate dose estimate is necessary for effective patient management after a fetal exposure. In the case of a high‐dose exposure, it is critical to use all resources available in order to make the most accurate assessment of the fetal dose. This work will demonstrate a methodology for accurate fetal dose estimation using tools that have recently become available in many clinics, and show examples of best practices for collecting data and performing the fetal dose calculation.

Methods:

A fetal dose estimate calculation was performed using modern data collection tools to determine parameters for the calculation. The reference point air kerma as displayed by the fluoroscopic system was checked for accuracy. A cumulative dose incidence map and DICOM header mining were used to determine the displayed reference point air kerma. Corrections for attenuation caused by the patient table and pad were measured and applied in order to determine the peak skin dose. The position and depth of the fetus was determined by ultrasound imaging and consultation with a radiologist. The data collected was used to determine a normalized uterus dose from Monte Carlo simulation data. Fetal dose values from this process were compared to other accepted calculation methods.

Results:

An accurate high‐dose fetal dose estimate was made. Comparison to accepted legacy methods were were within 35% of estimated values.

Conclusion:

Modern data collection and reporting methods ease the process for estimation of fetal dose from interventional fluoroscopy exposures. Many aspects of the calculation can now be quantified rather than estimated, which should allow for a more accurate estimation of fetal dose.
SU‐F‐P‐23: Setup Uncertainties for the Lung Stereotactic Body Radiation Therapy
Authors: Zhang Q , Cao Y , Jamshidi A , Vigneri P , Madu C , Potters L , Klein E
Published: July 2016

Purpose:

The Exactrack X‐ray system with six degree‐of‐freedom (6DoF) adjustment ability can be used for setup of lung stereotactic body radiation therapy. The setup uncertainties from ExacTrack 6D system were analyzed.

Methods:

The Exactrack X‐ray 6D image guided radiotherapy system is used in our clinic. The system is an integration of 2 subsystems: (1): an infrared based optical position system and (2) a radiography kV x‐ray imaging system. The infrared system monitors reflective body markers on the patient's skin to assistant in the initial setup. The radiographic kV devices were used for patient positions verification and adjustment. The position verification was made by fusing the radiographs with the digitally reconstructed radiograph (DRR) images generated by simulation CT images using 6DoF fusion algorithms. Those results were recorded in our system. Gaussian functions were used to fit the data.

Results:

For 37 lung SBRT patients, the image registration results for the initial setup by using surface markers and for the verifications, were measured. The results were analyzed for 143 treatments. The mean values for the lateral, longitudinal, vertical directions were 0.1, 0.3 and 0.3mm, respectively. The standard deviations for the lateral, longitudinal and vertical directions were 0.62, 0.78 and 0.75mm respectively. The mean values for the rotations around lateral, longitudinal and vertical directions were 0.1, 0.2 and 0.4 degrees respectively, with standard deviations of 0.36, 0.34, and 0.42 degrees.

Conclusion:

The setup uncertainties for the lung SBRT cases by using Exactrack 6D system were analyzed. The standard deviations of the setup errors were within 1mm for all three directions, and the standard deviations for rotations were within 0.5 degree.
SU‐F‐P‐29: Impact of Oral Contrast Agent for Assisting in Outlining Small Intestine On Pelvic IMAT Dose in Patients with Cervical Cancer
Authors: Zhang R , Bai W , Fan X
Published: July 2016

Purpose:

As the advanced intensity modulated arc therapy(IMAT) delivery systems becoming a main role of treatment ways, which places even greater demands on delivering accuracy. The impact of oral contrast agent (meglumine diatrizoate) for assisting in outlining the small intestine on pelvic IMAT dose in patients with cervical cancer was investigated.

Methods:

Ten cervical cancer patients for postoperative radiotherapy underwent CT scans, and the planning target volumes (PTV) and organs at risk (including the small intestine, rectum, bladder, colon and the left and right femoral head) were contoured. The IMAT plans were generated on Oncentra v4.1 planning system for each case, PTV was prescribed to 50.4 Gy in 28 fractions. Then another plan was generated by re‐calculating the radiation dose after changing the electron density of the small bowel. The first plan (plan A) was the conventional IMAT plan (with oral contrast agent), and the second one (plan B) specified the electron density of the small bowel (without oral contrast agent). Paired t‐test was used to compare the dose distribution between the two plans.

Results:

The PTV's D2, D50, D95, V110, conformity index, and homogeneity index of plans A and B were 5610.5 vs. 5611.4 cGy (P=0.175), 5348.5 vs. 5348.0 cGy (P=0.869), 5039 vs. 5042.3 (P=0.518), 6.0% vs. 6.1 %(P=0.886), 0.1269 vs. 0.1271 (P=0.34) and 0.8421 vs. 0.8416 (P=0.598), respectively. The volumes of the small bowel receiving at least 30 Gy (V30) and the minimum dose of 2% volume accepted (D2) for plans A and B were 31.6% vs. 31.9% (P=0.371) and 5067.8 vs. 5085.4 cGy (P=0.377), while rectum V50 of the two plans was 12.4% vs. 12.1% (P=0.489).

Conclusion:

The oral contrast agent (meglumine diatrizoate) filling the small intestine does not lead to a significant increase in the pelvic IMAT dose in patients with cervical cancer.
SU‐F‐P‐30: Clinical Assessment of Auto Beam‐Hold Triggered by Fiducial Localization During Prostate RapidArc Delivery
Authors: Atkinson P , Chen Q
Published: July 2016

Purpose:

To assess the clinical efficacy of auto beam hold during prostate RapidArc delivery, triggered by fiducial localization on kV imaging with a Varian True Beam.

Methods:

Prostate patients with four gold fiducials were candidates in this study. Daily setup was accomplished by aligning to fiducials using orthogonal kV imaging. During RapidArc delivery, a kV image was automatically acquired with a momentary beam hold every 60 degrees of gantry rotation. The position of each fiducial was identified by a search algorithm and compared to a predetermined 1.4 cm diameter target area. Treatment continued if all the fiducials were within the target area. If any fiducial was outside the target area the beam hold was not released, and the operators determined if the patient needed re‐alignment using the daily setup method.

Results:

Four patients were initially selected. For three patients, the auto beam hold performed seamlessly. In one instance, the system correctly identified misaligned fiducials, stopped treatment, and the patient was re‐positioned. The fourth patient had a prosthetic hip which sometimes blocked the fiducials and caused the fiducial search algorithm to fail. The auto beam hold was disabled for this patient and the therapists manually monitored the fiducial positions during treatment. Average delivery time for a 2‐arc fraction was increased by 59 seconds. Phantom studies indicated the dose discrepancy related to multiple beam holds is <0.1%. For a plan with 43 fractions, the additional imaging increased dose by an estimated 68 cGy.

Conclusion:

Automated intrafraction kV imaging can effectively perform auto beam holds due to patient movement, with the exception of prosthetic hip patients. The additional imaging dose and delivery time are clinically acceptable. It may be a cost‐effective alternative to Calypso in RapidArc prostate patient delivery. Further study is warranted to explore its feasibility under various clinical conditions.
SU‐F‐P‐34: Commission of Enhanced Dynamic Wedge of Varian Truebeam Linac System with Feature Study
Authors: Li K , Able A
Published: July 2016

Purpose:

To evaluate an Enhanced Dynamic Wedge (EDW) as part of machine commission process with feature study.

Methods:

The EDW system in this study was from a Truebeam, which is the Linear accelerator manufactured by Varian Medical Systems. The EDW feature vectors includes selected elements. These elements were dosimetric output spots check, field size, wedge angles, dose rate, collimator orientation, and different energy settings. Point dose measurement was done by a PTW farmer chamber, and profiles were measured by Gafchromic EBT2 films positing at different depths of the Solidwater based on the study elements. The output spot measurements were done with PTW farmer chamber with Solidwater setting for all orientation and wedge angles in the EDW system. The profiles comparisons were done by IMRT measurement function in RIT software at version 6.3. And the films were scanned by Vidar scanner. Dosimetry calculation were done by using the same Solidwater scanned by GE LightSpeed CT in Eclipse Treatment Planning System (TPS). Then measurements were compared to simulation results in TPS.

Results:

The energy average percentage difference between chamber measurement and TPS was 0.16% with standard deviation (SD) at 0.93%. For selected features, the average percentage difference between film measurement and computation was 0.93% with SD at 1.55% in horizontal profiles, and 1.18% with SD at 0.98% at vertical profiles. The average gamma difference for film measurement and TPS computing results was at 0.924 with SD at 0.314.

Conclusion:

A feature vector was developed to describe the commission of EDW, and developing a complete set of features for sufficiency of commission of a LINAC function could provide optimal commission instance with acceptable confident level of clinical application of the machine. Given the institution specific vector pattern and big data process, it could provide wide range clinical outcome comparison information in application of EDW.
SU‐F‐P‐39: End‐To‐End Validation of a 6 MV High Dose Rate Photon Beam, Configured for Eclipse AAA Algorithm Using Golden Beam Data, for SBRT Treatments Using RapidArc
Authors: Ferreyra M , Salinas Aranda F , Dodat D , Sansogne R , Arbiser S
Published: July 2016

Purpose:

To use end‐to‐end testing to validate a 6 MV high dose rate photon beam, configured for Eclipse AAA algorithm using Golden Beam Data (GBD), for SBRT treatments using RapidArc.

Methods:

Beam data was configured for Varian Eclipse AAA algorithm using the GBD provided by the vendor. Transverse and diagonals dose profiles, PDDs and output factors down to a field size of 2×2 cm2 were measured on a Varian Trilogy Linac and compared with GBD library using 2% 2mm 1D gamma analysis. The MLC transmission factor and dosimetric leaf gap were determined to characterize the MLC in Eclipse. Mechanical and dosimetric tests were performed combining different gantry rotation speeds, dose rates and leaf speeds to evaluate the delivery system performance according to VMAT accuracy requirements. An end‐to‐end test was implemented planning several SBRT RapidArc treatments on a CIRS 002LFC IMRT Thorax Phantom. The CT scanner calibration curve was acquired and loaded in Eclipse. PTW 31013 ionization chamber was used with Keithley 35617EBS electrometer for absolute point dose measurements in water and lung equivalent inserts. TPS calculated planar dose distributions were compared to those measured using EPID and MapCheck, as an independent verification method. Results were evaluated with gamma criteria of 2% dose difference and 2mm DTA for 95% of points.

Results:

GBD set vs. measured data passed 2% 2mm 1D gamma analysis even for small fields. Machine performance tests show results are independent of machine delivery configuration, as expected. Absolute point dosimetry comparison resulted within 4% for the worst case scenario in lung. Over 97% of the points evaluated in dose distributions passed gamma index analysis.

Conclusion:

Eclipse AAA algorithm configuration of the 6 MV high dose rate photon beam using GBD proved efficient. End‐to‐end test dose calculation results indicate it can be used clinically for SBRT using RapidArc.
SU‐F‐R‐38: Impact of Smoothing and Noise On Robustness of CBCT Textural Features for Prediction of Response to Radiotherapy Treatment of Head and Neck Cancers
Authors: Bagher‐Ebadian H , Chetty I , Liu C , Movsas B , Siddiqui F
Published: July 2016

Purpose:

To examine the impact of image smoothing and noise on the robustness of textural information extracted from CBCT images for prediction of radiotherapy response for patients with head/neck (H/N) cancers.

Methods:

CBCT image datasets for 14 patients with H/N cancer treated with radiation (70 Gy in 35 fractions) were investigated. A deformable registration algorithm was used to fuse planning CT's to CBCT's. Tumor volume was automatically segmented on each CBCT image dataset. Local control at 1‐year was used to classify 8 patients as responders (R), and 6 as non‐responders (NR). A smoothing filter [2D Adaptive Weiner (2DAW) with 3 different windows (ψ=3, 5, and 7)], and two noise models (Poisson and Gaussian, SNR=25) were implemented, and independently applied to CBCT images. Twenty‐two textural features, describing the spatial arrangement of voxel intensities calculated from gray‐level co‐occurrence matrices, were extracted for all tumor volumes.

Results:

Relative to CBCT images without smoothing, none of 22 textural features extracted showed any significant differences when smoothing was applied (using the 2DAW with filtering parameters of ψ=3 and 5), in the responder and non‐responder groups. When smoothing, 2DAW with ψ=7 was applied, one textural feature, Information Measure of Correlation, was significantly different relative to no smoothing. Only 4 features (Energy, Entropy, Homogeneity, and Maximum‐Probability) were found to be statistically different between the R and NR groups (Table 1). These features remained statistically significant discriminators for R and NR groups in presence of noise and smoothing.

Conclusion:

This preliminary work suggests that textural classifiers for response prediction, extracted from H&N CBCT images, are robust to low‐power noise and low‐pass filtering. While other types of filters will alter the spatial frequencies differently, these results are promising. The current study is subject to Type II errors. A much larger cohort of patients is needed to confirm these results.

This work was supported in part by a grant from Varian Medical Systems (Palo Alto, CA)