bluuebunny/crossref_metadata_2025_split huggingface dataset:
WE‐DE‐BRC‐03: Failure Mode and Effect Analysis
Authors: Dunscombe P. 
Published: July 2016

This SAMs Therapy Educational Course will introduce participants to the tools recommended by TG 100 for use in the development of a risk‐based Quality Management Program. The Course will start with an Overview of the background and rationale behind the TG 100 initiative, from which its charge was developed. After setting the scene, four 15 minute presentations will introduce the principal components of the soon to be published Report of TG 100. These are Process Mapping, Failure Modes and Effects Analysis, Fault Tree Analysis and the development of a QA/QM risk‐based Program. There will be time for two short exercises based on Failure Modes and Effects Analysis and a Discussion before the SAMs questions which will conclude the session.

Learning Objectives:
To appreciate the underlying philosophy of the TG 100 initiative.
To gain a brief overview of the principal risk‐based tools recommended by TG 100.
In an informal workshop format, to explore, at an introductory level, the use of risk analysis as proposed by TG 100 as a prelude to the development of a Quality Management Program.
WE‐DE‐BRA‐11: A Study of Motion Tracking Accuracy of Robotic Radiosurgery Using a Novel CCD Camera Based End‐To‐End Test System
Authors: Wang L , Nelson B , M Yang Y 
Published: July 2016

Purpose:A novel end‐to‐end test system using a CCD camera and a scintillator based phantom (XRV‐124, Logos Systems Int'l) capable of measuring the beam‐by‐beam delivery accuracy of Robotic Radiosurgery (CyberKnife) was developed and reported in our previous work. This work investigates its application in assessing the motion tracking (Synchrony) accuracy for CyberKnife.Methods:A QA plan with Anterior and Lateral beams (with 4 different collimator sizes) was created (Multiplan v5.3) for the XRV‐124 phantom. The phantom was placed on a motion platform (superior and inferior movement), and the plans were delivered on the CyberKnife M6 system using four motion patterns: static, Sine‐ wave, Sine with 15° phase shift, and a patient breathing pattern composed of 2cm maximum motion with 4 second breathing cycle. Under integral recording mode, the time‐averaged beam vectors (X, Y, Z) were measured by the phantom and compared with static delivery. In dynamic recording mode, the beam spots were recorded at a rate of 10 frames/second. The beam vector deviation from average position was evaluated against the various breathing patterns.Results:The average beam position of the six deliveries with no motion and three deliveries with Synchrony tracking on ideal motion (sinewave without phase shift) all agree within −0.03±0.00 mm, 0.10±0.04, and 0.04±0.03 in the X, Y, and X directions. Radiation beam width (FWHM) variations are within ±0.03 mm. Dynamic video record showed submillimeter tracking stability for both regular and irregular breathing pattern; however the tracking error up to 3.5 mm was observed when a 15 degree phase shift was introduced.Conclusion:The XRV‐124 system is able to provide 3D and 4D targeting accuracy for CyberKnife delivery with Synchrony. The experimental results showed sub‐millimeter delivery in phantom with excellent correlation in target to breathing motion. The accuracy was degraded when irregular motion and phase shift was introduced.
WE‐DE‐206‐01: MRI Signal in Biological Tissues ‐ Proton, Spin, T1, T2, T2*
Authors: Gorny K. 
Published: July 2016

Magnetic resonance imaging (MRI) has become an essential part of clinical imaging due to its ability to render high soft tissue contrast. Instead of ionizing radiation, MRI use strong magnetic field, radio frequency waves and field gradients to create diagnostic useful images. It can be used to image the anatomy and also functional and physiological activities within the human body. Knowledge of the basic physical principles underlying MRI acquisition is vitally important to successful image production and proper image interpretation.This lecture will give an overview of the spin physics, imaging principle of MRI, the hardware of the MRI scanner, and various pulse sequences and their applications. It aims to provide a conceptual foundation to understand the image formation process of a clinical MRI scanner.

Learning Objectives:
Understand the origin of the MR signal and contrast from the spin physics level.
Understand the main hardware components of a MRI scanner and their purposes
Understand steps for MR image formation including spatial encoding and image reconstruction
Understand the main kinds of MR pulse sequences and their characteristics.
WE‐FG‐207B‐04: Noise Suppression for Energy‐Resolved CT Via Variance Weighted Non‐Local Filtration
Authors: Harms J , Zhu L 
Published: July 2016

Purpose:The photon starvation problem is exacerbated in energy‐resolved CT, since the detected photons are shared by multiple energy channels. Using pixel similarity‐based non‐local filtration, we aim to produce accurate and high‐resolution energy‐resolved CT images with significantly reduced noise.Methods:Averaging CT images reconstructed from different energy channels reduces noise at the price of losing spectral information, while conventional denoising techniques inevitably degrade image resolution. Inspired by the fact that CT images of the same object at different energies share the same structures, we aim to reduce noise of energy‐resolved CT by averaging only pixels of similar materials ‐ a non‐local filtration technique. For each CT image, an empirical exponential model is used to calculate the material similarity between two pixels based on their CT values and the similarity values are organized in a matrix form. A final similarity matrix is generated by averaging these similarity matrices, with weights inversely proportional to the estimated total noise variance in the sinogram of different energy channels. Noise suppression is achieved for each energy channel via multiplying the image vector by the similarity matrix.Results:Multiple scans on a tabletop CT system are used to simulate 6‐channel energy‐resolved CT, with energies ranging from 75 to 125 kVp. On a low‐dose acquisition at 15 mA of the Catphan©600 phantom, our method achieves the same image spatial resolution as a high‐dose scan at 80 mA with a noise standard deviation (STD) lower by a factor of >2. Compared with another non‐local noise suppression algorithm (ndiNLM), the proposed algorithms obtains images with substantially improved resolution at the same level of noise reduction.Conclusion:We propose a noise‐suppression method for energy‐resolved CT. Our method takes full advantage of the additional structural information provided by energy‐resolved CT and preserves image values at each energy level.Research reported in this publication was supported by the National Institute Of Biomedical Imaging And Bioengineering of the National Institutes of Health under Award Number R21EB019597. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
WE‐G‐204‐02: So You Want to Do Research: Two Approaches to Beginning a Career in Medical Physics Research
Authors: Deasy J. 
Published: July 2016

While many indicators for academic medical physics are distressing – jobs are tight, demands on clinical time are high (and getting worse) and national funding has been flat for several years (meaning less money in reality) the present is perhaps one of the most exciting times in cancer research history, and medical physicists have an opportunity to make a difference.Many of us predict the impact of medical physics on cancer research over the next decade to be more significant than ever. Why is that? First, medical imaging is used for every cancer patient in developed countries. Every improvement in the acquisition, processing or analysis of radiological images has the potential to impact patients. The use of radiation therapy is at an all‐time high – and virtually cannot be performed without medical physics. Many of the advances in both biomedical imaging and radiation oncology are the result of the hard work of academic medical physicists who are thinking of the next generation of technologies that will be used against cancer or an even broader spectrum of diseases.A career in academic medical physics is demanding, particularly for those with clinical responsibilities. As the demands for justification of their clinical effort become increasingly metricized, the ability to do “unfunded research” will become even more difficult. This means that many will have to generate external salary support to justify their efforts in research and development. This comes at a time when funding for research is compressed and harder to obtain. Generally speaking, if you are not contributing 50% or more of your effort to research, you are competing at a disadvantage and it is very unlikely you will get an NIH/NCI/NIBIB grant.Furthermore, in the ongoing effort to improve patient care and safety, we have developed credentialing pathways that now require at least two‐years of residency training. This full‐time clinical training creates a gap in the research trajectory of graduate students who aspire to academic positions with an expectation for extramural funding. To address this, several residency programs have created hybrid programs where the two‐years of clinical training is combined with one or two years of research effort to allow candidates to further establish an academic identity and to ensure adequate academic productivity to compete for a beginning faculty position.In conclusion, while the path to a successful career in academic medical physics is steep and sometimes hard to follow, reaching the apex is worth the journey. Different paths to a career in medical physics are available, you just have to decide which one is right for you. If improving cancer care is your goal as a physicist, then academic medical physics is the job for you!
WE‐H‐BRC‐05: Catastrophic Error Metrics for Radiation Therapy
Authors: Murphy S , Molloy J 
Published: July 2016

Purpose:Intuitive evaluation of complex radiotherapy treatments is impractical, while data transfer anomalies create the potential for catastrophic treatment delivery errors. Contrary to prevailing wisdom, logical scrutiny can be applied to patient‐specific machine settings. Such tests can be automated, applied at the point of treatment delivery and can be dissociated from prior states of the treatment plan, potentially revealing errors introduced early in the process.Methods:Analytical metrics were formulated for conventional and intensity modulated RT (IMRT) treatments. These were designed to assess consistency between monitor unit settings, wedge values, prescription dose and leaf positioning (IMRT). Institutional metric averages for 218 clinical plans were stratified over multiple anatomical sites. Treatment delivery errors were simulated using a commercial treatment planning system and metric behavior assessed via receiver‐operator‐characteristic (ROC) analysis. A positive result was returned if the erred plan metric value exceeded a given number of standard deviations, e.g. 2. The finding was declared true positive if the dosimetric impact exceeded 25%. ROC curves were generated over a range of metric standard deviations.Results:Data for the conventional treatment metric indicated standard deviations of 3%, 12%, 11%, 8%, and 5 % for brain, pelvis, abdomen, lung and breast sites, respectively. Optimum error declaration thresholds yielded true positive rates (TPR) between 0.7 and 1, and false positive rates (FPR) between 0 and 0.2. Two proposed IMRT metrics possessed standard deviations of 23% and 37%. The superior metric returned TPR and FPR of 0.7 and 0.2, respectively, when both leaf position and MUs were modelled. Isolation to only leaf position errors yielded TPR and FPR values of 0.9 and 0.1.Conclusion:Logical tests can reveal treatment delivery errors and prevent large, catastrophic errors. Analytical metrics are able to identify errors in monitor units, wedging and leaf positions with favorable sensitivity and specificity.In part by Varian
WE‐H‐BRA‐03: Development of a Model to Include the Evolution of Resistant Tumor Subpopulations Into the Treatment Optimization Process for Schedules Involving Targeted Agents in Chemoradiation Therapy
Authors: Grassberger C , Paganetti H 
Published: July 2016

Purpose:To develop a model that includes the process of resistance development into the treatment optimization process for schedules that include targeted therapies. Further, to validate the approach using clinical data and to apply the model to assess the optimal induction period with targeted agents before curative treatment with chemo‐radiation in stage III lung cancer.Methods:Growth of the tumor and its subpopulations is modeled by Gompertzian growth dynamics, resistance induction as a stochastic process. Chemotherapy induced cell kill is modeled by log‐cell kill dynamics, targeted agents similarly but restricted to the sensitive population. Radiation induced cell kill is assumed to follow the linear‐quadratic model. The validation patient data consist of a cohort of lung cancer patients treated with tyrosine kinase inhibitors that had longitudinal imaging data available.Results:The resistance induction model was successfully validated using clinical trial data from 49 patients treated with targeted agents. The observed recurrence kinetics, with tumors progressing from 1.4–63 months, result in tumor growth equaling a median volume doubling time of 92 days [34–248] and a median fraction of pre‐existing resistance of 0.035 [0–0.22], in agreement with previous clinical studies. The model revealed widely varying optimal time points for the use of curative therapy, reaching from ∼1m to >6m depending on the patient's growth rate and amount of pre‐existing resistance. This demonstrates the importance of patient‐specific treatment schedules when targeted agents are incorporated into the treatment.Conclusion:We developed a model including evolutionary dynamics of resistant sub‐populations with traditional chemotherapy and radiation cell kill models. Fitting to clinical data yielded patient specific growth rates and resistant fraction in agreement with previous studies. Further application of the model demonstrated how proper timing of chemo‐radiation could minimize the probability of resistance, increasing tumor control significantly.
WE‐H‐BRA‐06: Experimental Investigation of RBE for Lung Cancer Cell Lines as a Function of Dose and LET in Proton, Helium and Carbon Beams
Authors: Patel D , Bronk L , Guan F , Peeler C , Mirkovic D , Grosshans D , Jakel O , Abdollahi A , Titt U , Mohan R 
Published: July 2016

Purpose:Investigate and quantify the effect of dose and LET on the RBE of protons, helium and carbon ions.Methods:High throughput, high accuracy experimental setups were custom designed to investigate the Relative Biological Effectiveness (RBE) dependence on the dose and Linear Energy Transfer (LET) values for proton, helium and carbon ion beams. The experiment was conducted at the HIT facility in collaboration with the DKFZ in Heidelberg/Germany. Clonogenic assays of two human lung cancer cell lines, H460 and H1437, were investigated in this study. γH2AX foci staining on the H460 cell line was also undertaken to facilitate the study of differential DNA double‐strand break induction and repair between low‐design available at the HIT facility. Specific points along the Bragg curve corresponding to well‐defined doses and LET values were chosen by appropriate selection of the pre‐absorber thicknesses. With a setup design for horizontal beam lines we were able to minimize ion scattering in the cell plate, resulting in narrower energy spectra and hence LET distributions in the Bragg peak and in the distal falloff regions, compared to the earlier experiments.Results:Approximately 16,000 samples of cancer cells were irradiated during 23 hours of beam time. The preliminary results of the survival curves for both cell lines show a distinct dependence on LET for a given dose with decreased survival fractions at increasing LET values, encountered at the Bragg peak and in the distal falloff.Conclusion:Our preliminary findings are indicative of the importance of novel variable‐RBE models for proton therapy and provide insight into the RBE of heavy ions for possible future heavy ion therapy facilities in the US.Funding support: SINF 2015/16
WE‐H‐202‐00: Session in Memory of Jean Pouliot: Next‐Generation Deformable Image Registration
Authors: Hugo Geoffrey 
Published: July 2016

Deformable image registration has now been commercially available for several years, with solid performance in a number of sites and for several applications including contour and dose mapping. However, more complex applications have arisen, such as assessing response to radiation therapy over time, registering images pre‐ and post‐surgery, and auto‐segmentation from atlases. These applications require innovative registration algorithms to achieve accurate alignment. The goal of this session is to highlight emerging registration technology and these new applications. The state of the art in image registration will be presented from an engineering perspective. Translational clinical applications will also be discussed to tie these new registration approaches together with imaging and radiation therapy applications in specific diseases such as cervical and lung cancers.

Learning Objectives:
To understand developing techniques and algorithms in deformable image registration that are likely to translate into clinical tools in the near future.
To understand emerging imaging and radiation therapy clinical applications that require such new registration algorithms.Research supported in part by the National Institutes of Health under award numbers P01CA059827, R01CA166119, and R01CA166703. Disclosures: Phillips Medical systems (Hugo), Roger Koch (Christensen) support, Varian Medical Systems (Brock), licensing agreements from Raysearch (Brock) and Varian (Hugo).; K. Brock, Licensing Agreement ‐ RaySearch Laboratories. Research Funding ‐ Varian Medical Systems; G. Hugo, Research grant from National Institutes of Health, award number R01CA166119.; G. Christensen, Research support from NIH grants CA166119 and CA166703 and a gift from Roger Koch. There are no conflicts of interest.
WE‐H‐207B‐00: MRgRT
Authors: Stanescu Teo 
Published: July 2016

In recent years, steady progress has been made towards the implementation of MRI in external beam radiation therapy for processes ranging from treatment simulation to in‐room guidance. Novel procedures relying mostly on MR data are currently implemented in the clinic. This session will cover topics such as (a) commissioning and quality control of the MR in‐room imagers and simulators specific to RT, (b) treatment planning requirements, constraints and challenges when dealing with various MR data, (c) quantification of organ motion with an emphasis on treatment delivery guidance, and (d) MR‐driven strategies for adaptive RT workflows. The content of the session was chosen to address both educational and practical key aspects of MR guidance.

Learning Objectives:
Good understanding of MR testing recommended for in‐room MR imaging as well as image data validation for RT chain (e.g. image transfer, filtering for consistency, spatial accuracy, manipulation for task specific);
Familiarity with MR‐based planning procedures: motivation, core workflow requirements, current status, challenges;
Overview of the current methods for the quantification of organ motion;
Discussion on approaches for adaptive treatment planning and delivery.T. Stanescu ‐ License agreement with Modus Medical Devices to develop a phantom for the quantification of MR image system‐related distortions.; T. Stanescu, N/A
TH‐AB‐201‐04: Clinical Protocol for Reuse of Optically Stimulated Luminescence Detectors
Authors: Graeper G , Pillai S 
Published: July 2016

Purpose:OSLDs made of Al2O3:C have many useful dosimetric characteristics including their ability to be reused. The signal on an OSLD can be removed through heat or light. The objective of this study was to characterize the change in sensitivity associated with annealing OSLDs with light and in doing so define a range through which reuse is viable.Methods:Four groups of nanoDot OSLDs were repeatedly irradiated and bleached to create accumulated dose history. Each group's repeated irradiation remained constant at either 50, 100, 200, or 500 cGy. Before both irradiation and bleaching the OSLDs were read out, giving the dose reading and ensuring that ample bleaching had occurred, respectively. New and used OSLDs were compared in several clinical situations to verify accuracy. One final test involved correcting the readout dose based on the loss of sensitivity seen in the accumulated dose data.Results:In the first 40 Gy of accumulated dose the sensitivity can be broken into two regions: a region of sensitivity change and a region of no sensitivity change. From 0 cGy to an average of 1080 cGy the sensitivity does not change. After 1080 cGy the sensitivity begins to decrease linearly with an average slope of 0.00456 cGy lost per cGy accumulated after the cutoff point. The slope and cutoff point were used to correct readings in the final test, reducing the error from 6.8% to 3.9%.Conclusion:In the region of no sensitivity change OSLDs can be reused without concern to the validity of their result. Readings must be corrected if OSLDs are to be used in the region of sensitivity change, above 1080 cGy. After 40 Gy OSLDs must be retired because the sensitivity change reverses, making linear correction no longer feasible.
TH‐AB‐201‐08: Ion Chamber Dose Measurements ‐ Problems with the Temperature‐Pressure Correction Factor
Authors: Bourgouin A , McEwen M 
Published: July 2016

Purpose:To investigate the behavior of ionization chambers over a wide pressure range.Methods:Three cylindrical and two parallel‐plate designs of ion chamber were investigated. The ion chambers were placed in vessel where the pressure was varied from atmospheric (101 kPa) down to 5 kPa. Measurements were made using 60Co and high‐energy electron beams. The pressure was measured to better than 0.1% and multiple data sets were obtained for each chamber at both polarities to investigate pressure cycling and dependency on the sign of the charge collected.Results:For all types of chamber, the ionization current, corrected using the standard PTP, showed a similar behaviour. Deviations from the standard theory were generally small for Co‐60 but very significant for electron beams, up to 20 % below P = 10 kPa. The effect was found to be always larger when collecting negative charge, suggesting a dependence on free‐electron collection. The most likely source of such electrons is low‐energy electrons emitted from the electrodes. This signal would be independent of air pressure within the chamber cavity. The data was analyzed to extract this signal and it was found to be a non‐negligible component of the ionization current at atmospheric pressure. In the case of the parallel plate chambers, the effect was approximately 0.25 %. For the cylindrical chambers the effect was larger ‐ up to 1.2 % ‐ and dependent on the chamber type, which would be consistent with electron emission from different wall materials. For the electron beams, the correction factor was dependent on the electron energy and approximately double that observed in 60Co.Conclusion:Measurements have indicated significant deviations of the standard pressure correction that are consistent with electron emission from chamber electrodes. This has implications for both primary standard and reference ion chamber‐based dosimetry.