bluuebunny/crossref_metadata_2025_split huggingface dataset:
TU‐H‐201‐04: Panel Discussion Member
Authors: Dobbins J. 
Published: July 2016

The New New Symposium is a symposium for members relatively new to the organization to learn about the organizational structure and operational procedures of the society; how decisions are made, how the council and committee leadership is appointed and operates, opportunities for volunteer involvement, and a brief overview of the services and efforts provided by the HQ staff and the website. Attendees will hear from council chairs, key staff and chairs, and members with volunteer experience.After the symposium a social hour ensues with opportunities to interact with key AAPM members. The New Member Symposium is a (free) ticket option when you register online for the Annual Meeting. And don't forget registrants receive one (free) ticket for a beverage of your choice during the social afterwards.
TU‐H‐BRC‐05: Stereotactic Radiosurgery Optimized with Orthovoltage Beams
Authors: Fagerstrom J , Bender E , Culberson W 
Published: July 2016

Purpose:To achieve improved stereotactic radiosurgery (SRS) dose distributions using orthovoltage energy fluence modulation with inverse planning optimization techniques.Methods:A pencil beam model was used to calculate dose distributions from the institution's orthovoltage unit at 250 kVp. Kernels for the model were derived using Monte Carlo methods as well as measurements with radiochromic film. The orthovoltage photon spectra, modulated by varying thicknesses of attenuating material, were approximated using open‐source software. A genetic algorithm search heuristic routine was used to optimize added tungsten filtration thicknesses to approach rectangular function dose distributions at depth. Optimizations were performed for depths of 2.5, 5.0, and 7.5 cm, with cone sizes of 8, 10, and 12 mm.Results:Circularly‐symmetric tungsten filters were designed based on the results of the optimization, to modulate the orthovoltage beam across the aperture of an SRS cone collimator. For each depth and cone size combination examined, the beam flatness and 80–20% and 90–10% penumbrae were calculated for both standard, open cone‐collimated beams as well as for the optimized, filtered beams. For all configurations tested, the modulated beams were able to achieve improved penumbra widths and flatness statistics at depth, with flatness improving between 33 and 52%, and penumbrae improving between 18 and 25% for the modulated beams compared to the unmodulated beams.Conclusion:A methodology has been described that may be used to optimize the spatial distribution of added filtration material in an orthovoltage SRS beam to result in dose distributions at depth with improved flatness and penumbrae compared to standard open cones. This work provides the mathematical foundation for a novel, orthovoltage energy fluence‐modulated SRS system.
TU‐H‐BRC‐06: Temperature Simulation of Tungsten and W25Re Targets to Deliver High Dose Rate 10 MV Photons
Authors: Wang J , Trovati S , Loo B , Maxim P , Borchard P , Fahrig R 
Published: July 2016

Purpose:To study the impact of electron beam size, target thickness, and target temperature on the ability of the flattening filter‐free mode (FFF) treatment head to deliver high‐dose‐rate irradiations.Methods:The dose distribution and transient temperature of the X‐ray target under 10 MeV electron beam with pulse length of 5 microseconds, and repetition rate of 1000 Hz was studied. A MCNP model was built to calculate the percentage depth dose (PPD) distribution in a water phantom at a distance of 100 cm. ANSYS software was used to run heat transfer simulations. The PPD and temperature for both tungsten and W25Re targets for different electron beam sizes (FHWM 0.2, 0.5, 1 and 2 mm) and target thickness (0.2 to 2 mm) were studied.Results:Decreasing the target thickness from 1 mm to 0.5 mm, caused a surface dose increase about 10 percent. For both target materials, the peak temperature was about 1.6 times higher for 0.5 mm electron beam compared to the 1 mm beam after reaching their equilibrium. For increasing target thicknesses, the temperature rise caused by the first pulse is similar for all thicknesses, however the temperature difference for subsequent pulses becomes larger until a constant ratio is reached. The target peak temperature after reaching equilibrium can be calculated by adding the steady state temperature and the amplitude of the temperature oscillation.Conclusion:This work indicates the potential to obtain high dose rate irradiation by selecting target material, geometry and electron beam parameters. W25Re may not outperformed tungsten when the target is thick due to its relatively low thermal conductivity. The electron beam size only affects the target temperature but not the PPD. Thin target is preferred to obtain high dose rate and low target temperature, however, the resulting high surface dose is a major concern.NIH funding:R21 EB015957‐01; DOD funding:W81XWH‐13‐1‐0165BL, PM, PB, and RF are founders of TibaRay, Inc. BL is also a borad member. BL and PM have received research grants from Varian Medical System, Inc. and RaySearch Laboratory. RF is an employee of Siemens Healthcare GmbH
TU‐H‐BRA‐01: The Physics of High Power Radiofrequency Isolation in a Novel Compact Linear Accelerator Based MRI Guided Radiation Therapy System
Authors: Lamb J , Low D , Mutic S , Shvartsman S , Chmielewski T , Fought G , Sharma A , Dempsey J 
Published: July 2016

Purpose:To develop a method for isolating the radiofrequency waves emanating from linear accelerator components from the magnetic resonance imaging (MRI) system of an integrated MRI‐linac.Methods:An MRI‐guided radiation therapy system has been designed that integrates a linear accelerator with simultaneous MR imaging. The radiofrequency waves created by the accelerating process would degrade MR image quality, so a method for containing the radiofrequency waves and isolating the MR imager from them was developed. The linear accelerator radiofrequency modulator was placed outside the room, so a filter was designed to eliminate the radiofrequency corresponding to the proton Larmour frequency of 14.7 MHz. Placing the radiofrequency emitting components in a typical Faraday cage would have reduced the radiofrequency emissions, but the design would be susceptible to small gaps in the shield due to the efficiency of the Faraday cage reflecting internal radiofrequency emissions. To reduce internal radiofrequency reflections, the Faraday cage was lined with carbon fiber sheets. Carbon fiber has the property of attenuating the radiofrequency energy so that the overall radiofrequency field inside the Faraday cage is reduced, decreasing any radiofrequency energy emitted from small gaps in the cage walls.Results:Within a 1.2 MHz band centered on the Larmor frequency, the radiofrequency (RF) leakage from the Faraday cage was measured to be −90 dB with no RF on, −40 dB with the RF on and no shield, returning to −90 dB with the RF on and shields in place. The radiofrequency filter attenuated the linear accelerator modulator emissions in the 14.7 MHz band by 70 dB.Conclusions:One of the major challenges in designing a compact linear accelerator based MRI‐guided radiation therapy system, that of isolating the high power RF system from the MRI, has been solved. The measured radiofrequency emissions are sufficiently small to enable system integration.This research was funded by ViewRay, Inc., Oakwood, OH
TU‐H‐BRA‐04: A Novel Superconducting Magnet Design for Optimized Patient Access and Minimal SSD for Use in a Linac‐MR Hybrid
Authors: Yaghoobpour Tari S , Wachowicz K , Fallone B 
Published: July 2016

Purpose:A prototype rotating hybrid MR imaging system and linac has been developed to allow for simultaneous imaging and radiation delivery parallel to B0. However, the design of a compact magnet capable of rotation in a small vault with sufficient patient access and a typical clinical source‐to‐surface distance (SSD) is challenging. This work presents a novel superconducting magnet design that allows for a reduced SSD and ample patient access by moving the superconducting coils to the side of the yoke. The yoke and pole‐plate structures are shaped to direct the magnetic flux appropriately.Methods:The surface of the pole plate for the magnet assembly is optimized. The magnetic field calculations required in this work are performed with the 3D finite element method software package Opera‐3D. Each tentative design strategy is virtually modeled in this software package and externally controlled by MATLAB, with its key geometries defined as variables. The particle swarm optimization algorithm is used to optimize the variables subject to the minimization of a cost function. At each iteration, Opera‐3D will solve the magnetic field solution over a field‐of‐view suitable for MR imaging and the degree of field uniformity will be assessed to calculate the value of the cost function associated with that iteration.Results:An optimized magnet assembly that generates a homogenous 0.2T magnetic field over an ellipsoid with large axis of 30 cm and small axes of 20 cm is obtained.Conclusion:The distinct features of this model are the minimal distance between the yoke's top and the isocentre and the improved patient access. On the other hand, having homogeneity over an ellipsoid give us a larger field‐of‐view, essential for geometric accuracy of the MRI system. The increase of B0 from 0.2T in the present model to 0.5T is the subject of future work.Funding Sources: Alberta Innovates ‐ Health Solutions (AIHS)| Disclosure and Conflict of Interest: B. Gino Fallone is a co‐founder and CEO of MagnetTx Oncology Solutions (under discussions to license Alberta biplanar linac MR for commercialization).
TU‐H‐BRA‐05: A System Design for Integration of An Interior MRI and a Linear Accelerator
Authors: Mao W , Wang G 
Published: July 2016

Purpose:MRI is a highly desirable modality to guide radiation therapy but it is difficult to combine a conventional MRI scanner directly with a linear accelerator (linac). An interior MRI (iMRI) concept has been proposed to acquire MRI images within a small field of view only covering targets and immediate surrounding tissues. The objective of this project is to design an interior MRI system to work with a linac using a magnet to provide a field around 0.2T in a cube of 20cm per side, and perform image reconstruction with a slightly inhomogeneous static magnetic fields.Methods:All the results are simulated using a commercially available software package, FARADY. In our design, a ring structure holds the iMRI system and also imbeds a linac treatment head. The ring is synchronized to the linac gantry rotation. Half of the ring is made of steel and becomes a magnetic flux return path (yoke) so that a strong magnetic field will be limited inside the iron circuit and fringe fields will be very weak. In order to increase the static magnetic field homogeneity, special steel magnet boots or tips were simulated. Three curved boots were designed based on two‐dimensional curves: arc, parabola and hyperbola.Results:Different boot surfaces modify magnetic field distributions differently. With the same pair of neodymium‐iron‐boron (NdFeB) magnets, the magnetic induction at the centers are 0.217T, 0.201T, 0.204T, and 0.212T for flat, arc, parabola and hyperbola boots, respectively. The hyperbola boots lead to the most homogeneous results, the static magnetic field deviations are within 0.5% in a cube of 20cm, and can be further improved using shimming techniques.Conclusion:This study supports the concept of an iMRI design. Successful development of iMRI will provide crucial information for tumor delineation in radiation therapy.
TU‐H‐202‐04: The VAMPIRE Challenge: Preliminary Results From a Multi‐Institutional Study of CT Ventilation Image Accuracy
Authors: Kipritidis J. 
Published: July 2016

CT ventilation imaging is an exciting functional imaging modality that combines four‐dimensional computed tomography (4DCT) and deformable image registration (DIR) to provide exquisite ventilation maps of the lung. CT ventilation imaging can be used for:

Functional avoidance in thoracic radiation therapy,
Imaging longitudinal changes in regional lung function for treatment assessment and adaptation,
Image‐assisted diagnosis of non‐oncologic respiratory diseases.CT ventilation imaging uses CT, a predominantly anatomic imaging modality, and through imaging processing creates functional images. CT ventilation imaging provides functional images that are higher resolution, faster and cheaper to perform than the clinical standard, SPECT. Indeed the number of CT ventilation abstracts presented at the AAPM meeting has been doubling every two years. With the world's‐first clinical trial of CT ventilation functional image‐guided radiation therapy now underway, the first dedicated scientific symposium will educate and stimulate AAPM members from both radiology and radiation oncology.This symposium will compare the foundations of CT ventilation imaging with competing MRI, PET and SPECT ventilation imaging methods, and details the first clinical trial of CT ventilation imaging for functional avoidance in lung cancer radiation therapy. The spatial‐temporal nature of pulmonary ventilation, response maps to radiation and the design of predictive models will be presented. Validation efforts and challenges will also be discussed, from clinical outcome correlations in single time point and longitudinal studies, to cross‐modality image comparisons in the first multi‐institutional CT ventilation imaging challenge.The panel will discuss the future role of CT ventilation imaging, and what level of physiologic validation is needed for applications in radiation oncology and beyond.

Learning Objectives:
Learn the principles of CT ventilation imaging and how ventilation images are acquired with MRI, PET and SPECT
Understand the methods used to benchmark CT ventilation and the correlations between CT ventilation imaging and clinical outcomes
Recognize the clinical applications of CT ventilation imaging in radiation oncology and beyondAustralian NHMRC Fellowship. Australian NSW Cancer Institute Fellowship.; Y. Vinogradskiy, The authors acknowledge NIH R01CA200817 grant and Stat of Colorado grant.; T. Yamamoto, This study was supported in part by the American Cancer Society and the Dean of the University of California Davis School of Medicine (ACS IRG‐95‐125‐13). Philips Radiation Oncology Systems loaned us a research version of the Pinnacle3 treatment planning system.; J. Bayouth, Funding support from NCIR01 CA166703; J. Kipritidis, This work has been supported by a Cancer Institute NSW Early Career Fellowship and an NHMRC Australia Fellowship.No commercial funding was received for this work.
TU‐H‐207A‐02: Relative Importance of the Various Factors Influencing the Accuracy of Monte Carlo Simulated CT Dose Index
Authors: Marous L , Morgan A , Dong F , Muryn J , Liptak C , Primak A , Li X 
Published: July 2016

Purpose:Monte Carlo simulation is a frequently used technique for assessing patient dose in CT. The accuracy of a Monte Carlo program is often validated using the standard CT dose index (CTDI) phantoms by comparing simulated and measured CTDI100. To achieve good agreement, many input parameters in the simulation (e.g., energy spectrum and effective beam width) need to be determined. However, not all the parameters have equal importance. Our aim was to assess the relative importance of the various factors that influence the accuracy of simulated CTDI100.Methods:A Monte Carlo program previously validated for a clinical CT system was used to simulate CTDI100. For the standard CTDI phantoms (32 and 16 cm in diameter), CTDI100 values from central and four peripheral locations at 70 and 120 kVp were first simulated using a set of reference input parameter values (treated as the truth). To emulate the situation in which the input parameter values used by the researcher may deviate from the truth, additional simulations were performed in which intentional errors were introduced into the input parameters, the effects of which on simulated CTDI100 were analyzed.Results:At 38.4‐mm collimation, errors in effective beam width up to 5.0 mm showed negligible effects on simulated CTDI100 (<1.0%). Likewise, errors in acrylic density of up to 0.01 g/cm3 resulted in small CTDI100 errors (<2.5%). In contrast, errors in spectral HVL produced more significant effects: slight deviations (±0.2 mm Al) produced errors up to 4.4%, whereas more extreme deviations (±1.4 mm Al) produced errors as high as 25.9%. Lastly, ignoring the CT table introduced errors up to 13.9%.Conclusion:Monte Carlo simulated CTDI100 is insensitive to errors in effective beam width and acrylic density. However, they are sensitive to errors in spectral HVL. To obtain accurate results, the CT table should not be ignored.This work was supported by a Faculty Research and Development Award from Cleveland State University.
TU‐H‐206‐07: Assessment of Geometric Distortion in EPI with a SPAMM Tagged Acquisition
Authors: Hwang K , Meier J , Yung J , Stafford R 
Published: July 2016

Purpose:Echo planar imaging (EPI) is known to exhibit gross geometric distortion caused by multiple factors, including B0 inhomgeneity and transient eddy currents. However, diffusion weighted (DW) EPI has become indispensable for diagnosis and therapy assessment. We propose a methodology for quantifying distortion in EPI sequences that does not require the use of dedicated spatial accuracy phantoms, enabling flexibility in phantom design for QA of distortion effects in EPI protocols.Methods:The proposed methodology utilizes a saturation technique known as Spatial Modulation of Magnetization (SPAMM) that tags the imaging subject with saturated grid lines. Originally intended for tracking cardiac motion, these grids are applied to assess differences between diffusion weighting directions and b‐values, or against a more geometrically robust sequence such as fast spin echo (FSE). The saturation preparation sequence consists of binomially weighted (e.g. 1‐3‐3‐1) pulses interleaved with gradient blips along the frequency encode direction, followed by the same sequence with gradient blips in the phase encode direction. Three phantoms were assessed with these sequences: a spherical head‐sized phantom, a large shimming phantom, and a modified PET ACR phantom that included compartments of water, air, oil, and Teflon. Each phantom was acquired with three sequences using parameters from a clinically appropriate protocol (22 cm head or 46 cm abdomen): a conventional DW‐EPI sequence (3 DW directions), and both the DW‐EPI and FSE sequences with tagging. Differences in grid locations were visualized with minimum intensity projection between images, and measured using intersecting locations on the grids.Results:Grid lines were clearly visualized on tagged images and enabled quantification of distortions. Maximum eddy current induced errors of 10.8 to 14.8 mm were observed in areas away from isocenter with DW gradients applied in various directions.Conclusion:SPAMM tagging provides a promising mechanism for assessing spatial distribution of distortion in EPI sequences.
TU‐H‐209‐02: Quality Assurance and QMP for Brachytherapy Treatment Delivery and Treatment Planning System
Authors: Chilukuri M. 
Published: July 2016

Learnings Objectives:
Although brachytherapy is the oldest form of radiation therapy, the rapid advancement of the methods of dose calculation, treatment planning and treatment delivery pushes us to keep updating our knowledge and experience to new procedures all the time. Our purpose is to present the newest applicators used in Accelerated Partial Breast Irradiation (APBI) and the techniques of using them for a maximum effective treatment. Our objective will be to get the user familiar with the Savi, Contura and ML Mammosite from the detailed description and measurements to cavity eval and choice or size, to acceptance tests and use of each.
At the end of the session the attendants will be able to assist at the scanning of the patient for the first treatment, decide on the proper localization and immobilization devices, import the scans in the treatment planning system, perform the structure segmentation, reconstruct the catheters and develop a treatment plan using inverse planning (IPSA) or volume optimization. The attendant should be able to evaluate the quality of a treatment plan according to the ABS protocols and B39 after this session.
Our goal is that all the attendants to gain knowledge of all the quality assurance procedures required to be performed prior to a treatment, at the beginning of a treatment day, weekly, monthly and annualy on the remote afterloader, the treatment planning system and the secondary check system. We will provide tips for a consistent treatment delivery of the 10 fractions in a BID (twice daily) regimen.
TU‐H‐209‐03: Planning and Treatment Delivery for APBI Using Savi, Contura and ML Mammosite
Authors: Pella S. 
Published: July 2016

Learnings Objectives:
Although brachytherapy is the oldest form of radiation therapy, the rapid advancement of the methods of dose calculation, treatment planning and treatment delivery pushes us to keep updating our knowledge and experience to new procedures all the time. Our purpose is to present the newest applicators used in Accelerated Partial Breast Irradiation (APBI) and the techniques of using them for a maximum effective treatment. Our objective will be to get the user familiar with the Savi, Contura and ML Mammosite from the detailed description and measurements to cavity eval and choice or size, to acceptance tests and use of each.
At the end of the session the attendants will be able to assist at the scanning of the patient for the first treatment, decide on the proper localization and immobilization devices, import the scans in the treatment planning system, perform the structure segmentation, reconstruct the catheters and develop a treatment plan using inverse planning (IPSA) or volume optimization. The attendant should be able to evaluate the quality of a treatment plan according to the ABS protocols and B39 after this session.
Our goal is that all the attendants to gain knowledge of all the quality assurance procedures required to be performed prior to a treatment, at the beginning of a treatment day, weekly, monthly and annualy on the remote afterloader, the treatment planning system and the secondary check system. We will provide tips for a consistent treatment delivery of the 10 fractions in a BID (twice daily) regimen.
TU‐H‐207B‐02: Funding (NCI) for Radiomics
Authors: Jacobs P. 
Published: July 2016

Research and development in radiomics for precision medicine have been advancing at a rapid pace, and can be extended to eventually be mature enough for integration into clinical practice. To facilitate advances in this field, investigators need updated information on research funding, regulatory matters, and clinical translation efforts. In this special radiomics symposium, the attendee will learn of various novel funding mechanisms – both past and present – that have been used to support a number of quantitative imaging and radiomics research and resource infrastructures. In addition, a regulatory presentation will be given to provide the attendee with an understanding of when a radiomics tool might require FDA clearance or approval, and with what supporting performance data. We will end with insights from a clinical radiologist who is greatly involved in quantitative imaging in order to enable the attendee to appreciate the needs and subtleties involved in moving radiomics into the clinical workflow.J. Boone, This is a memorial and not a funded event.