Results for “physicists” — Page 39

DOE OSTI2015

WE-G-BRA-07: Analyzing the Safety Implications of a Brachytherapy Process Improvement Project Utilizing a Novel System-Theory-Based Hazard-Analysis Technique

Purpose: To investigate the hazards in cervical-cancer HDR brachytherapy using a novel hazard-analysis technique, System Theoretic Process Analysis (STPA). The applicability and benefit of STPA to the field of radiation oncology is demonstrated. Methods: We analyzed the tandem and ring HDR procedure through observations, discussions with physicists and physicians, and the use of a previously developed process map. Controllers and their respective control actions were identified and arranged into a hierarchical control model of the system, modeling the workflow from applicator insertion through initiating treatment delivery. We then used the STPA process to identify potentially unsafe control actions. Scenarios were then generated from the identified unsafe control actions and used to develop recommendations for system safety constraints. Results: 10 controllers were identified and included in the final model. From these controllers 32 potentially unsafe control actions were identified, leading to more than 120 potential accident scenarios, including both clinical errors (e.g., using outdated imaging studies for planning), and managerial-based incidents (e.g., unsafe equipment, budget, or staffing decisions). Constraints identified from those scenarios include common themes, such as the need for appropriate feedback to give the controllers an adequate mental model to maintain safe boundaries of operations. As an example, one finding was that the likelihood of the potential accident scenario of the applicator breaking during insertion might be reduced by establishing a feedback loop of equipment-usage metrics and equipment-failure reports to the management controller. Conclusion: The utility of STPA in analyzing system hazards in a clinical brachytherapy system was demonstrated. This technique, rooted in system theory, identified scenarios both technical/clinical and managerial in nature. These results suggest that STPA can be successfully used to analyze safety in brachytherapy and may prove to be an alternative to other hazard analysis techniques.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

WE-G-BRA-09: Microsphere Brachytherapy Failure Mode and Effects Analysis in a Dual-Vendor Environment

Purpose: To improve the safety and quality of a dual-vendor microsphere brachytherapy program with failure mode and effects analysis (FMEA). Methods: A multidisciplinary team including physicists, dosimetrists, a radiation oncologist, an interventional radiologist, and radiation safety personnel performed an FMEA for our dual-vendor microsphere brachytherapy program employing SIR-Spheres (Sirtex Medical Limited, Australia) and Theraspheres (BTG, England). We developed a program process tree and step-by-step instructions which were used to generate a comprehensive list of failure modes. These modes were then ranked according to severity, occurrence rate, and detectability. Risk priority numbers (RPNs) were calculated by multiplying these three scores together. Three different severity scales were created: one each for harmful effects to the patient, staff, or the institution. Each failure mode was ranked on one or more of these scales. Results: The group identified 164 failure modes for the microsphere program. 113 of these were ranked using the patient severity scale, 52 using the staff severity scale, and 50 using the institution severity scale. The highest ranked items on the patient severity scale were an error in the automated dosimetry worksheet (RPN = 297.5), and the incorrect target specified on the planning study (RPN = 135). Some failure modes ranked differently between vendors, especially those corresponding to dose vial preparation because of the different methods used. Based on our findings, we made several improvements to our QA program, including documentation to easily identify which product is being used, an additional hand calculation during planning, and reorganization of QA steps before treatment delivery. We will continue to periodically review and revise the FMEA. Conclusion: We have applied FMEA to our dual-vendor microsphere brachytherapy program to identify potential key weaknesses in the treatment chain. Our FMEA results were used to improve the effectiveness of our overall microsphere program.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

WE-G-303-00: Nanotechnology for Imaging and Therapy

Over the last decade, there has been a growing interest in applying nanotechnology to cancer detection, treatment, and treatment monitoring. Advances in nanotechnology have enabled the fabrication of nanoparticles from various materials with different shapes and sizes. Nanoparticles can be accumulated preferentially within tumors by either “passive targeting” through a phenomenon typically known as “enhanced permeability and retention” or “active targeting” in which nanoparticles are conjugated with antibodies or peptides directed against tumor and/or stromal markers. The tumor specificity of nanoparticles in conjunction with their unique physicochemical properties offers many novel strategies for cancer treatment and detection. For example, notable approaches in the radiation oncology setting include the use of gold nanoparticles for radiation response modulation of tumor or normal tissue and thermal ablation or hyperthermia treatment of tumors. Some of these approaches are currently being tested either on humans or on animals and, very likely, will become the clinical reality in the near future. Various computational and experimental techniques have also been applied to address unique research issues associated with nanoparticles and may become the standard tools for future investigations and clinical translations. Therefore, both clinicians and researchers may need to be properly educated about the basic principles as well as the promise of nanoparticle-based applications with regard to the future of cancer diagnostics and therapeutics. This symposium will familiarize the audience with the potential applications of nanoparticles in oncologic imaging and therapy using specific illustrative examples. The audience will be properly oriented by these illustrative examples to the multiple avenues for collaborative research amongst interdisciplinary teams of physicists, clinicians, engineers, chemists, and biologists in industry and academia. Learning Objectives: Understand the physical bases of gold nanoparticle applications for radiosensitization and x-ray fluorescence imaging Understand the parameters that define gold nanoparticle-mediated radiosensitization in biological systems Understand the potential of magnetic nanoparticle characterization of the microenvironment Understand the various strategies for radiolabeling of nanoparticles and their applications S.C. and S.K. acknowledge support from MD Anderson Cancer Center, NIH (R01CA155446 and P30CA16672) and DoD (W81XWH-12-1-0198); J.W. acknowledges support from NIH (U54CA151662-01); W.C. acknowledges support from the University of Wisconsin-Madison, NIH (R01CA169365, P30CA014520, and T32CA009206), DoD (W81XWH-11-1-0644 and W81XWH-11-1-0648), and ACS (125246-RSG-13-099-01-CCE)

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

WE-G-303-01: Physical Bases for Gold Nanoparticle Applications in Radiation Oncology and X-Ray Imaging

Over the last decade, there has been a growing interest in applying nanotechnology to cancer detection, treatment, and treatment monitoring. Advances in nanotechnology have enabled the fabrication of nanoparticles from various materials with different shapes and sizes. Nanoparticles can be accumulated preferentially within tumors by either “passive targeting” through a phenomenon typically known as “enhanced permeability and retention” or “active targeting” in which nanoparticles are conjugated with antibodies or peptides directed against tumor and/or stromal markers. The tumor specificity of nanoparticles in conjunction with their unique physicochemical properties offers many novel strategies for cancer treatment and detection. For example, notable approaches in the radiation oncology setting include the use of gold nanoparticles for radiation response modulation of tumor or normal tissue and thermal ablation or hyperthermia treatment of tumors. Some of these approaches are currently being tested either on humans or on animals and, very likely, will become the clinical reality in the near future. Various computational and experimental techniques have also been applied to address unique research issues associated with nanoparticles and may become the standard tools for future investigations and clinical translations. Therefore, both clinicians and researchers may need to be properly educated about the basic principles as well as the promise of nanoparticle-based applications with regard to the future of cancer diagnostics and therapeutics. This symposium will familiarize the audience with the potential applications of nanoparticles in oncologic imaging and therapy using specific illustrative examples. The audience will be properly oriented by these illustrative examples to the multiple avenues for collaborative research amongst interdisciplinary teams of physicists, clinicians, engineers, chemists, and biologists in industry and academia. Learning Objectives: Understand the physical bases of gold nanoparticle applications for radiosensitization and x-ray fluorescence imaging Understand the parameters that define gold nanoparticle-mediated radiosensitization in biological systems Understand the potential of magnetic nanoparticle characterization of the microenvironment Understand the various strategies for radiolabeling of nanoparticles and their applications S.C. and S.K. acknowledge support from MD Anderson Cancer Center, NIH (R01CA155446 and P30CA16672) and DoD (W81XWH-12-1-0198); J.W. acknowledges support from NIH (U54CA151662-01); W.C. acknowledges support from the University of Wisconsin-Madison, NIH (R01CA169365, P30CA014520, and T32CA009206), DoD (W81XWH-11-1-0644 and W81XWH-11-1-0648), and ACS (125246-RSG-13-099-01-CCE)

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

WE-G-303-02: Gold Nanoparticles as Radiosensitizers - What Does It Take To Go From the Bench to the Bedside?

Over the last decade, there has been a growing interest in applying nanotechnology to cancer detection, treatment, and treatment monitoring. Advances in nanotechnology have enabled the fabrication of nanoparticles from various materials with different shapes and sizes. Nanoparticles can be accumulated preferentially within tumors by either “passive targeting” through a phenomenon typically known as “enhanced permeability and retention” or “active targeting” in which nanoparticles are conjugated with antibodies or peptides directed against tumor and/or stromal markers. The tumor specificity of nanoparticles in conjunction with their unique physicochemical properties offers many novel strategies for cancer treatment and detection. For example, notable approaches in the radiation oncology setting include the use of gold nanoparticles for radiation response modulation of tumor or normal tissue and thermal ablation or hyperthermia treatment of tumors. Some of these approaches are currently being tested either on humans or on animals and, very likely, will become the clinical reality in the near future. Various computational and experimental techniques have also been applied to address unique research issues associated with nanoparticles and may become the standard tools for future investigations and clinical translations. Therefore, both clinicians and researchers may need to be properly educated about the basic principles as well as the promise of nanoparticle-based applications with regard to the future of cancer diagnostics and therapeutics. This symposium will familiarize the audience with the potential applications of nanoparticles in oncologic imaging and therapy using specific illustrative examples. The audience will be properly oriented by these illustrative examples to the multiple avenues for collaborative research amongst interdisciplinary teams of physicists, clinicians, engineers, chemists, and biologists in industry and academia. Learning Objectives: Understand the physical bases of gold nanoparticle applications for radiosensitization and x-ray fluorescence imaging Understand the parameters that define gold nanoparticle-mediated radiosensitization in biological systems Understand the potential of magnetic nanoparticle characterization of the microenvironment Understand the various strategies for radiolabeling of nanoparticles and their applications S.C. and S.K. acknowledge support from MD Anderson Cancer Center, NIH (R01CA155446 and P30CA16672) and DoD (W81XWH-12-1-0198); J.W. acknowledges support from NIH (U54CA151662-01); W.C. acknowledges support from the University of Wisconsin-Madison, NIH (R01CA169365, P30CA014520, and T32CA009206), DoD (W81XWH-11-1-0644 and W81XWH-11-1-0648), and ACS (125246-RSG-13-099-01-CCE)

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

WE-G-303-03: Advances in in Vivo Magnetic NanoparticleSensing

Over the last decade, there has been a growing interest in applying nanotechnology to cancer detection, treatment, and treatment monitoring. Advances in nanotechnology have enabled the fabrication of nanoparticles from various materials with different shapes and sizes. Nanoparticles can be accumulated preferentially within tumors by either “passive targeting” through a phenomenon typically known as “enhanced permeability and retention” or “active targeting” in which nanoparticles are conjugated with antibodies or peptides directed against tumor and/or stromal markers. The tumor specificity of nanoparticles in conjunction with their unique physicochemical properties offers many novel strategies for cancer treatment and detection. For example, notable approaches in the radiation oncology setting include the use of gold nanoparticles for radiation response modulation of tumor or normal tissue and thermal ablation or hyperthermia treatment of tumors. Some of these approaches are currently being tested either on humans or on animals and, very likely, will become the clinical reality in the near future. Various computational and experimental techniques have also been applied to address unique research issues associated with nanoparticles and may become the standard tools for future investigations and clinical translations. Therefore, both clinicians and researchers may need to be properly educated about the basic principles as well as the promise of nanoparticle-based applications with regard to the future of cancer diagnostics and therapeutics. This symposium will familiarize the audience with the potential applications of nanoparticles in oncologic imaging and therapy using specific illustrative examples. The audience will be properly oriented by these illustrative examples to the multiple avenues for collaborative research amongst interdisciplinary teams of physicists, clinicians, engineers, chemists, and biologists in industry and academia. Learning Objectives: Understand the physical bases of gold nanoparticle applications for radiosensitization and x-ray fluorescence imaging Understand the parameters that define gold nanoparticle-mediated radiosensitization in biological systems Understand the potential of magnetic nanoparticle characterization of the microenvironment Understand the various strategies for radiolabeling of nanoparticles and their applications S.C. and S.K. acknowledge support from MD Anderson Cancer Center, NIH (R01CA155446 and P30CA16672) and DoD (W81XWH-12-1-0198); J.W. acknowledges support from NIH (U54CA151662-01); W.C. acknowledges support from the University of Wisconsin-Madison, NIH (R01CA169365, P30CA014520, and T32CA009206), DoD (W81XWH-11-1-0644 and W81XWH-11-1-0648), and ACS (125246-RSG-13-099-01-CCE)

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

WE-G-303-04: Intrinsically Radiolabeled Nanoparticles: An Emerging Paradigm

Over the last decade, there has been a growing interest in applying nanotechnology to cancer detection, treatment, and treatment monitoring. Advances in nanotechnology have enabled the fabrication of nanoparticles from various materials with different shapes and sizes. Nanoparticles can be accumulated preferentially within tumors by either “passive targeting” through a phenomenon typically known as “enhanced permeability and retention” or “active targeting” in which nanoparticles are conjugated with antibodies or peptides directed against tumor and/or stromal markers. The tumor specificity of nanoparticles in conjunction with their unique physicochemical properties offers many novel strategies for cancer treatment and detection. For example, notable approaches in the radiation oncology setting include the use of gold nanoparticles for radiation response modulation of tumor or normal tissue and thermal ablation or hyperthermia treatment of tumors. Some of these approaches are currently being tested either on humans or on animals and, very likely, will become the clinical reality in the near future. Various computational and experimental techniques have also been applied to address unique research issues associated with nanoparticles and may become the standard tools for future investigations and clinical translations. Therefore, both clinicians and researchers may need to be properly educated about the basic principles as well as the promise of nanoparticle-based applications with regard to the future of cancer diagnostics and therapeutics. This symposium will familiarize the audience with the potential applications of nanoparticles in oncologic imaging and therapy using specific illustrative examples. The audience will be properly oriented by these illustrative examples to the multiple avenues for collaborative research amongst interdisciplinary teams of physicists, clinicians, engineers, chemists, and biologists in industry and academia. Learning Objectives: Understand the physical bases of gold nanoparticle applications for radiosensitization and x-ray fluorescence imaging Understand the parameters that define gold nanoparticle-mediated radiosensitization in biological systems Understand the potential of magnetic nanoparticle characterization of the microenvironment Understand the various strategies for radiolabeling of nanoparticles and their applications S.C. and S.K. acknowledge support from MD Anderson Cancer Center, NIH (R01CA155446 and P30CA16672) and DoD (W81XWH-12-1-0198); J.W. acknowledges support from NIH (U54CA151662-01); W.C. acknowledges support from the University of Wisconsin-Madison, NIH (R01CA169365, P30CA014520, and T32CA009206), DoD (W81XWH-11-1-0644 and W81XWH-11-1-0648), and ACS (125246-RSG-13-099-01-CCE)

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

A round-robin gamma stereotactic radiosurgery dosimetry interinstitution comparison of calibration protocols

Purpose: Absorbed dose calibration for gamma stereotactic radiosurgery is challenging due to the unique geometric conditions, dosimetry characteristics, and nonstandard field size of these devices. Members of the American Association of Physicists in Medicine (AAPM) Task Group 178 on Gamma Stereotactic Radiosurgery Dosimetry and Quality Assurance have participated in a round-robin exchange of calibrated measurement instrumentation and phantoms exploring two approved and two proposed calibration protocols or formalisms on ten gamma radiosurgery units. The objectives of this study were to benchmark and compare new formalisms to existing calibration methods, while maintaining traceability to U.S. primary dosimetry calibration laboratory standards. Methods: Nine institutions made measurements using ten gamma stereotactic radiosurgery units in three different 160 mm diameter spherical phantoms [acrylonitrile butadiene styrene (ABS) plastic, Solid Water, and liquid water] and in air using a positioning jig. Two calibrated miniature ionization chambers and one calibrated electrometer were circulated for all measurements. Reference dose-rates at the phantom center were determined using the well-established AAPM TG-21 or TG-51 dose calibration protocols and using two proposed dose calibration protocols/formalisms: an in-air protocol and a formalism proposed by the International Atomic Energy Agency (IAEA) working group for small and nonstandard radiation fields. Each institution’s results were normalized to the dose-rate determined at that institution using the TG-21 protocol in the ABS phantom. Results: Percentages of dose-rates within 1.5% of the reference dose-rate (TG-21 + ABS phantom) for the eight chamber-protocol-phantom combinations were the following: 88% for TG-21, 70% for TG-51, 93% for the new IAEA nonstandard-field formalism, and 65% for the new in-air protocol. Averages and standard deviations for dose-rates over all measurements relative to the TG-21 + ABS dose-rate were 0.999 ± 0.009 (TG-21), 0.991 ± 0.013 (TG-51), 1.000 ± 0.009 (IAEA), and 1.009 ± 0.012 (in-air). There were no statistically significant differences (i.e., p > 0.05) between the two ionization chambers for the TG-21 protocol applied to all dosimetry phantoms. The mean results using the TG-51 protocol were notably lower than those for the other dosimetry protocols, with a standard deviation 2–3 times larger. The in-air protocol was not statistically different from TG-21 for the A16 chamber in the liquid water or ABS phantoms (p = 0.300 and p = 0.135) but was statistically different from TG-21 for the PTW chamber in all phantoms (p = 0.006 for Solid Water, 0.014 for liquid water, and 0.020 for ABS). Results of IAEA formalism were statistically different from TG-21 results only for the combination of the A16 chamber with the liquid water phantom (p = 0.017). In the latter case, dose-rates measured with the two protocols differed by only 0.4%. For other phantom-ionization-chamber combinations, the new IAEA formalism was not statistically different from TG-21. Conclusions: Although further investigation is needed to validate the new protocols for other ionization chambers, these results can serve as a reference to quantitatively compare different calibration protocols and ionization chambers if a particular method is chosen by a professional society to serve as a standardized calibration protocol.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2015

Vision 20/20: Mammographic breast density and its clinical applications

Breast density is a strong predictor of the failure of mammography screening to detect breast cancer and is a strong predictor of the risk of developing breast cancer. The many imaging options that are now available for imaging dense breasts show great promise, but there is still the question of determining which women are “dense” and what imaging modality is suitable for individual women. To date, mammographic breast density has been classified according to the Breast Imaging-Reporting and Data System (BI-RADS) categories from visual assessment, but this is known to be very subjective. Despite many research reports, the authors believe there has been a lack of physics-led and evidence-based arguments about what breast density actually is, how it should be measured, and how it should be used. In this paper, the authors attempt to start correcting this situation by reviewing the history of breast density research and the debates generated by the advocacy movement. The authors review the development of breast density estimation from pattern analysis to area-based analysis, and the current automated volumetric breast density (VBD) analysis. This is followed by a discussion on seeking the ground truth of VBD and mapping volumetric methods to BI-RADS density categories. The authors expect great improvement in VBD measurements that will satisfy the needs of radiologists, epidemiologists, surgeons, and physicists. The authors believe that they are now witnessing a paradigm shift toward personalized breast screening, which is going to see many more cancers being detected early, with the use of automated density measurement tools as an important component.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

Air-kerma strength determination of a new directional {sup 103}Pd source

Purpose: A new directional {sup 103}Pd planar source array called a CivaSheet™ has been developed by CivaTech Oncology, Inc., for potential use in low-dose-rate (LDR) brachytherapy treatments. The array consists of multiple individual polymer capsules called CivaDots, containing {sup 103}Pd and a gold shield that attenuates the radiation on one side, thus defining a hot and cold side. This novel source requires new methods to establish a source strength metric. The presence of gold material in such close proximity to the active {sup 103}Pd region causes the source spectrum to be significantly different than the energy spectra of seeds normally used in LDR brachytherapy treatments. In this investigation, the authors perform air-kerma strength (S{sub K}) measurements, develop new correction factors for these measurements based on an experimentally verified energy spectrum, and test the robustness of transferring S{sub K} to a well-type ionization chamber. Methods: S{sub K} measurements were performed with the variable-aperture free-air chamber (VAFAC) at the University of Wisconsin Medical Radiation Research Center. Subsequent measurements were then performed in a well-type ionization chamber. To realize the quantity S{sub K} from a directional source with gold material present, new methods and correction factors were considered. Updated correction factors were calculated using the MCNP 6 Monte Carlo code in order to determine S{sub K} with the presence of gold fluorescent energy lines. In addition to S{sub K} measurements, a low-energy high-purity germanium (HPGe) detector was used to experimentally verify the calculated spectrum, a sodium iodide (NaI) scintillating counter was used to verify the azimuthal and polar anisotropy, and a well-type ionization chamber was used to test the feasibility of disseminating S{sub K} values for a directional source within a cylindrically symmetric measurement volume. Results: The UW VAFAC was successfully used to measure the S{sub K} of four CivaDots with reproducibilities within 0.3%. Monte Carlo methods were used to calculate the UW VAFAC correction factors and the calculated spectrum emitted from a CivaDot was experimentally verified with HPGe detector measurements. The well-type ionization chamber showed minimal variation in response (<1.5%) as a function of source positioning angle, indicating that an American Association of Physicists in Medicine (AAPM) Accredited Dosimetry Calibration Laboratory calibrated well chamber would be a suitable device to transfer an S{sub K}-based calibration to a clinical user. S{sub K} per well-chamber ionization current ratios were consistent among the four dots measured. Additionally, the measurements and predictions of anisotropy show uniform emission within the solid angle of the VAFAC, which demonstrates the robustness of the S{sub K} measurement approach. Conclusions: This characterization of a new {sup 103}Pd directional brachytherapy source helps to establish calibration methods that could ultimately be used in the well-established AAPM Task Group 43 formalism. Monte Carlo methods accurately predict the changes in the energy spectrum caused by the fluorescent x-rays produced in the gold shield.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2016

Failure mode and effects analysis based risk profile assessment for stereotactic radiosurgery programs at three cancer centers in Brazil

Purpose: The goal of this study was to evaluate the safety and quality management program for stereotactic radiosurgery (SRS) treatment processes at three radiotherapy centers in Brazil by using three industrial engineering tools (1) process mapping, (2) failure modes and effects analysis (FMEA), and (3) fault tree analysis. Methods: The recommendations of Task Group 100 of American Association of Physicists in Medicine were followed to apply the three tools described above to create a process tree for SRS procedure for each radiotherapy center and then FMEA was performed. Failure modes were identified for all process steps and values of risk priority number (RPN) were calculated from O, S, and D (RPN = O × S × D) values assigned by a professional team responsible for patient care. Results: The subprocess treatment planning was presented with the highest number of failure modes for all centers. The total number of failure modes were 135, 104, and 131 for centers I, II, and III, respectively. The highest RPN value for each center is as follows: center I (204), center II (372), and center III (370). Failure modes with RPN ≥ 100: center I (22), center II (115), and center III (110). Failure modes characterized by S ≥ 7, represented 68% of the failure modes for center III, 62% for center II, and 45% for center I. Failure modes with RPNs values ≥100 and S ≥ 7, D ≥ 5, and O ≥ 5 were considered as high priority in this study. Conclusions: The results of the present study show that the safety risk profiles for the same stereotactic radiotherapy process are different at three radiotherapy centers in Brazil. Although this is the same treatment process, this present study showed that the risk priority is different and it will lead to implementation of different safety interventions among the centers. Therefore, the current practice of applying universal device-centric QA is not adequate to address all possible failures in clinical processes at different radiotherapy centers. Integrated approaches to device-centric and process specific quality management program specific to each radiotherapy center are the key to a safe quality management program.

61 RADIATION PROTECTION AND DOSIMETRY↗

DOE OSTI2016

Polarity effects and apparent ion recombination in microionization chambers

Purpose: Microchambers demonstrate anomalous voltage-dependent polarity effects. Existing polarity and ion recombination correction factors do not account for these effects. As a result, many commercial microchamber models do not meet the specification of a reference-class ionization chamber as defined by the American Association of Physicists in Medicine. The purpose of this investigation is to determine the cause of these voltage-dependent polarity effects. Methods: A series of microchamber prototypes were produced to isolate the source of the voltage-dependent polarity effects. Parameters including ionization-chamber collecting-volume size, stem and cable irradiation, chamber assembly, contaminants, high-Z materials, and individual chamber components were investigated. Measurements were performed with electrodes coated with graphite to isolate electrode conductivity. Chamber response was measured as the potential bias of the guard electrode was altered with respect to the collecting electrode, through the integration of additional power supplies. Ionization chamber models were also simulated using COMSOL Multiphysics software to investigate the effect of a potential difference between electrodes on electric field lines and collecting volume definition. Results: Investigations with microchamber prototypes demonstrated that the significant source of the voltage-dependent polarity effects was a potential difference between the guard and collecting electrodes of the chambers. The voltage-dependent polarity effects for each prototype were primarily isolated to either the guard or collecting electrode. Polarity effects were reduced by coating the isolated electrode with a conductive layer of graphite. Polarity effects were increased by introducing a potential difference between the electrodes. COMSOL simulations further demonstrated that for a given potential difference between electrodes, the collecting volume of the chamber changed as the applied voltage was altered, producing voltage-dependent polarity effects in the chamber response. Ionization chamber measurements and COMSOL simulations demonstrated an inverse relationship between the chamber collecting volume size and the severity of voltage-dependent polarity effects on chamber response. The effect of a given potential difference on chamber polarity effects was roughly ten times greater for microchambers as compared to Farmer-type chambers. Stem and cable irradiations, chamber assembly, contaminants, and high-Z materials were not found to be a significant source of the voltage-dependent polarity effects. Conclusions: A potential difference between the guard and collecting electrodes was found to be the primary source of the voltage-dependent polarity effects demonstrated by microchambers. For a given potential difference between electrodes, the relative change in the collecting volume is smaller for larger-volume chambers, illustrating why these polarity effects are not seen in larger-volume chambers with similar guard and collecting electrode designs. Thus, for small-volume chambers, it is necessary to reduce the potential difference between the guard and collecting electrodes in order to reduce polarity effects for reference dosimetry measurements.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

SU-C-202-03: A Tool for Automatic Calculation of Delivered Dose Variation for Off-Line Adaptive Therapy Using Cone Beam CT

Purpose: Monitoring the delivered dose is an important task for the adaptive radiotherapy (ART) and for determining time to re-plan. A software tool which enables automatic delivered dose calculation using cone-beam CT (CBCT) has been developed and tested. Methods: The tool consists of four components: a CBCT Colleting Module (CCM), a Plan Registration Moduel (PRM), a Dose Calculation Module (DCM), and an Evaluation and Action Module (EAM). The CCM is triggered periodically (e.g. every 1:00 AM) to search for newly acquired CBCTs of patients of interest and then export the DICOM files of the images and related registrations defined in ARIA followed by triggering the PRM. The PRM imports the DICOM images and registrations, links the CBCTs to the related treatment plan of the patient in the planning system (RayStation V4.5, RaySearch, Stockholm, Sweden). A pre-determined CT-to-density table is automatically generated for dose calculation. Current version of the DCM uses a rigid registration which regards the treatment isocenter of the CBCT to be the isocenter of the treatment plan. Then it starts the dose calculation automatically. The AEM evaluates the plan using pre-determined plan evaluation parameters: PTV dose-volume metrics and critical organ doses. The tool has been tested for 10 patients. Results: Automatic plans are generated and saved in the order of the treatment dates of the Adaptive Planning module of the RayStation planning system, without any manual intervention. Once the CTV dose deviates more than 3%, both email and page alerts are sent to the physician and the physicist of the patient so that one can look the case closely. Conclusion: The tool is capable to perform automatic dose tracking and to alert clinicians when an action is needed. It is clinically useful for off-line adaptive therapy to catch any gross error. Practical way of determining alarming level for OAR is under development.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

SU-C-209-07: Phantoms for Digital Breast Tomosynthesis Imaging System Evaluation

Purpose: Digital Breast Tomosynthesis (DBT) is gaining importance in breast imaging. There is a need for phantoms that can be used for image evaluation and comparison. Existing commercially available phantoms for DBT are expensive and may lack clinically relevant test objects. The purpose of this study is to develop phantoms for DBT evaluation. Methods Four phantoms have been designed and constructed to assess the image quality (IQ) of two DBT systems. The first contains a spiral of 0.3 mm SiC beads in gelatin to measure the tomographic slice thickness profile and uniformity of coverage in a series of tomographic planes. The second contains simulated tumors inclined with respect to the phantom base to assess tomographic image quality. The third has a tilted array of discs with varying contrast and diameter. This phantom was imaged alone and in a stack of TE slabs giving 2 to 10 cm thickness. The fourth has a dual wedge of glandular and adipose simulating materials. One wedge contains discs with varying diameter and thickness; the other supports a mass with six simulated spicules of varying size and a cluster of simulated calcifications. The simulated glandular tissue material varies between 35 and 100% of the total thickness (5.5 cm). Results: All phantoms were scanned successfully. The best IQ comparison was achieved with the dual wedge phantom as demonstrated by the spiculated mass and calcifications. Images were evaluated by two radiologists and one physicist. The projection images and corresponding set of tomographic planes were comparable and the synthesized projection images were inferior to the projection images for both systems. Conclusion: Four phantoms were designed, constructed and imaged on two DBT systems. They successfully demonstrated performance differences between two systems, and between true and synthesized projection images. Future work will incorporate these designs into a single phantom.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

SU-CD-PinS Room/Hall E-01

Medical Physicists are frequently involved in shipping radioactive materials or supervising those who do. Current U.S. Department of Transportation Hazardous Material Regulations, 49 CFR Parts 171 - 185, require hazmat employees to have documented training specified in 49 CFR 172 Subpart H. A hazmat employee is defined as an individual who: (1) loads, unloads or handles hazardous material; (2) manufactures, tests, reconditions, repairs, modifies, marks or otherwise represents containers, drums or packagings as qualified for use in the transportation of hazardous materials; (3) prepares hazardous materials for transportation; (4) is responsible for safety of transporting hazardous materials; or (5) operates a vehicle used to transport hazardous materials. Recurrent training is required at least once every three years. (The IATA two-year training interval is not applicable and is generally misunderstood.) FAA has escalated inspection and enforcement. Facilities who ship radiopharmaceuticals to other laboratories, return radiopharmaceuticals or radioactive sources to suppliers, or otherwise ship radioactive materials have been cited for failure to provide and document the required training. The interrelationship of transportation regulations, 49 CFR, IATA, ICAO and other transportation regulations, which are frequently misunderstood, will be explained. The course will cover typical shipments by air and highway which are encountered in a medical institution. Items such as fissile materials, highway route controlled quantities, rail shipments, vessel shipments and such will be omitted; although specific questions may be addressed. A major objective of the course is to present the process of shipping radioactive material in a sequential and logical fashion. How radioactive materials for transportation purposes are defined by activity concentrations for exempt materials and activity limits for exempt consignments will be explained. Radioactive material shipments of excepted packages and Type A packages will be emphasized. The program is designed to meet the function specific DOT training requirements for shippers of medical radioactive materials. General awareness training and security awareness training can be obtained from two free DOT training CDs. Safety training and security awareness training is generally satisfied by the training required under the institution’s radioactive material license. For shippers of radioactive Yellow III labeled packages an in-depth written security plan and training are no longer required as of April 8, 2010. In general almost all shippers of medical radioactive material are now not required to have an in-depth security plan. Contents of general awareness training, security awareness training and in-depth security plans will be briefly outlined. It is the hazmat employer’s responsibility to ensure that each hazmat employee is properly trained. No third party can fulfill that requirement. It is the hazmat employer’s responsibility to determine the degree to which this course meets the employer’s requirements, including contents of the course and the examination. Participants will gain sufficient knowledge to prepare hazmat training programs for others in their institutions. A handout will be posted which should be printed out and brought to the course for reference during the presentation. The handout will also satisfy part of the training documentation required by DOT. A feature handout section is a composite table which provides A1, A2, RQ, Exempt Concentration, and Exempt Consignment values in a single table in both Becquerel and Curie units. Course attendance will be certified through the AAPM CEU documentation system. Learning Objectives: Understand the regulatory requirements for shipping radioactive materials. Understand the regulatory requirements for training of hazmat employees. Comprehend how to classify, package, mark, label, document, placard, and transport radioactive materials.

61 RADIATION PROTECTION AND DOSIMETRY↗

DOE OSTI2016

SU-D-201-07: A Survey of Radiation Oncology Residents’ Training and Preparedness to Lead Patient Safety Programs in Clinics

Purpose: Safety and quality has garnered increased attention in radiation oncology, and physicians and physicists are ideal leaders of clinical patient safety programs. However, it is not clear whether residency programs incorporate formal patient safety training and adequately equip residents to assume this leadership role. A national survey was conducted to evaluate medical and physics residents’ exposure to safety topics and their confidence with the skills required to lead clinical safety programs. Methods: Radiation oncology residents were identified in collaboration with ARRO and AAPM. The survey was released in February 2016 via email using REDCap. This included questions about exposure to safety topics, confidence leading safety programs, and interest in training opportunities (i.e. workshops). Residents rated their exposure, skills, and confidence on 4 or 5-point scales. Medical and physics residents responses were compared using chi-square tests. Results: Responses were collected from 56 of 248 (22%) physics and 139 of 690 (20%) medical residents. More than two thirds of all residents had no or only informal exposure to incident learning systems (ILS), root cause analysis (RCA), failure mode and effects analysis (FMEA), and the concept of human factors engineering (HFE). Likewise, 63% of residents had not heard of RO-ILS. Response distributions were similar, however more physics residents had formal exposure to FMEA (p<0.0001) and felt they were adequately trained to lead FMEAs in clinic (p<0.001) than medical residents. Only 36% of residents felt their patient safety training was adequate, and 58% felt more training would benefit their education. Conclusion: These results demonstrate that, despite increasing desire for patient safety training, medical and physics residents’ exposure to relevant concepts is low. Physics residents had more exposure to FMEA than medical residents, and were more confident in leading FMEA. This suggests that increasing resident exposure to specific topics may increase their confidence.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

SU-F-E-10: Student-Driven Exploration of Radiographic Material Properties, Phantom Construction, and Clinical Workflows Or: The Extraordinary Life of CANDY MAN

Purpose: To develop a hands-on learning experience that explores the radiological and structural properties of everyday items and applies this knowledge to design a simple phantom for radiotherapy exercises. Methods: Students were asked to compile a list of readily available materials thought to have radiation attenuation properties similar to tissues within the human torso. Participants scanned samples of suggested materials and regions of interest (ROIs) were used to characterize bulk attenuation properties. Properties of each material were assessed via comparison to a Gammex Tissue characterization phantom and used to construct a list of inexpensive near-tissue-equivalent materials. Critical discussions focusing on samples found to differ from student expectations were used to revise and narrow the comprehensive list. From their newly acquired knowledge, students designed and constructed a simple thoracic phantom for use in a simulated clinical workflow. Students were tasked with setting up the phantom and acquiring planning CT images for use in treatment planning and dose delivery. Results: Under engineer and physicist supervision, students were trained to use a CT simulator and acquired images for approximately 60 different foodstuffs, candies, and household items. Through peer discussion, students gained valuable insights and were made to review preconceptions about radiographic material properties. From a subset of imaged materials, a simple phantom was successfully designed and constructed to represent a human thorax. Students received hands-on experience with clinical treatment workflows by learning how to perform CT simulation, create a treatment plan for an embedded tumor, align the phantom for treatment, and deliver a treatment fraction. Conclusion: In this activity, students demonstrated their ability to reason through the radiographic material selection process, construct a simple phantom to specifications, and exercise their knowledge of clinical workflows. Furthermore, the enjoyable and inexpensive nature of this project proved to attract participant interest and drive creative exploration. Mahon and Riblett have nothing to disclose; Hugo has a research agreement with Phillips Medical systems, a license agreement with Varian Medical Systems, research grants from the National Institute of Health. Authors do not have any potential conflicts of interest to disclose.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

SU-F-E-18: Training Monthly QA of Medical Accelerators: Illustrated Instructions for Self-Learning

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.

60 APPLIED LIFE SCIENCES↗