AAPM Medical Physics Practice Guideline 14.a: Yttrium-90 microsphere radioembolization.

Radioembolization using Yttrium-90 (90 Y) microspheres is widely used to treat primary and metastatic liver tumors. The present work provides minimum practice guidelines for establishing and supporting such a program. Medical physicists play a key role in patient and staff safety during these procedures. Products currently available are identified and their properties and suppliers summarized. Appropriateness for use is the domain of the treating physician. Patient work up starts with pre-treatment imaging. First, a mapping study using Technetium-99m (Tc-99m ) is carried out to quantify the lung shunt fraction (LSF) and to characterize the vascular supply of the liver. An MRI, CT, or a PET-CT scan is used to obtain information on the tumor burden. The tumor volume, LSF, tumor histology, and other pertinent patient characteristics are used to decide the type and quantity of 90 Y to be ordered. On the day of treatment, the appropriate dose is assayed using a dose calibrator with a calibration traceable to a national standard. In the treatment suite, the care team led by an interventional radiologist delivers the dose using real-time image guidance. The treatment suite is posted as a radioactive area during the procedure and staff wear radiation dosimeters. The treatment room, patient, and staff are surveyed post-procedure. The dose delivered to the patient is determined from the ratio of pre-treatment and residual waste exposure rate measurements. Establishing such a treatment modality is a major undertaking requiring an institutional radioactive materials license amendment complying with appropriate federal and state radiation regulations and appropriate staff training commensurate with their respective role and function in the planning and delivery of the procedure. Training, documentation, and areas for potential failure modes are identified and guidance is provided to ameliorate them.

A special report of current state of the medical physicist workforce - results of the 2012 ASTRO Comprehensive Workforce Study.

The medical physics profession is undergoing significant changes. Starting in 2014, candidates registering for certification exams by the American Board of Radiology must have completed a CAMPEP-accredited residency. This requirement, along with tightened state regulations, uncertainty in future reimbursement, and a stronger emphasis on board certification, have raised questions concerning the state of the medical physics workforce and its ability to adapt to changing requirements. In 2012, ASTRO conducted a workforce study of the comprehensive field of radiation oncology. This article reviews the findings of the medical physics section of the study, including age and gender distribution, educational background, workload, and primary work setting. We also report on job satisfaction, the perceived supply and demand of medical physicists, and the medical physicists' main concerns pertaining to patient safety and quality assurance.

Failure Mode and Effects Analysis for Experimental Use of FLASH on a Clinical Accelerator.

PURPOSE: The use of a linear accelerator (LINAC) in ultrahigh-dose-rate (UHDR) mode can provide a conduit for wider access to UHDR FLASH effects, sparing normal tissue, but care needs to be taken in the use of such systems to ensure errors are minimized. The failure mode and effects analysis was carried out in a team that has been involved in converting a LINAC between clinical use and UHDR experimental mode for more than 1 year after the proposed methods of TG100. METHODS AND MATERIALS: A team of 9 professionals with extensive experience were polled to outline the process map and workflow for analysis, and developed fault trees for potential errors, as well as failure modes that would result. The team scored the categories of severity magnitude, occurrence likelihood, and detectability potential in a scale of 1 to 10, so that a risk priority number (RPN = severity×occurrence×detectability) could be assessed for each. RESULTS: A total of 46 potential failure modes were identified, including 5 with an RPN >100. These failure modes involved (1) patient set up, (2) gating mechanisms in delivery, and (3) detector in the beam stop mechanism. The identified methods to mitigate errors included the (1) use of a checklist post conversion, (2) use of robust radiation detectors, (3) automation of quality assurance and beam consistency checks, and (4) implementation of surface guidance during beam delivery. CONCLUSIONS: The failure mode and effects analysis process was considered critically important in this setting of a new use of a LINAC, and the expert team developed a higher level of confidence in the ability to safely move UHDR LINAC use toward expanded research access.

One Year of Clinic-Wide Cherenkov Imaging for Discovery of Quality Improvement Opportunities in Radiation Therapy.

PURPOSE: Cherenkov imaging is clinically available as a radiation therapy treatment verification tool. The aim of this work was to discover the benefits of always-on Cherenkov imaging as a novel incident detection and quality improvement system through review of all imaging at our center. METHODS AND MATERIALS: Multicamera Cherenkov imaging systems were permanently installed in 3 treatment bunkers, imaging continuously over a year. Images were acquired as part of normal treatment procedures and reviewed for potential treatment delivery anomalies. RESULTS: In total, 622 unique patients were evaluated for this study. We identified 9 patients with treatment anomalies occurring over their course of treatment, which were only detected with Cherenkov imaging. Categorizing each event indicated issues arising in simulation, planning, pretreatment review, and treatment delivery, and none of the incidents were detected before this review by conventional measures. The incidents identified in this study included dose to unintended areas in planning, dose to unintended areas due to positioning at treatment, and nonideal bolus placement during setup. CONCLUSIONS: Cherenkov imaging was shown to provide a unique method of detecting radiation therapy incidents that would have otherwise gone undetected. Although none of the events detected in this study reached the threshold of reporting, they identified opportunities for practice improvement and demonstrated added value of Cherenkov imaging in quality assurance programs.

Performance comparison of quantitative metrics for analysis of in vivo Cherenkov imaging incident detection during radiotherapy.

OBJECTIVES: Examine the responses of multiple image similarity metrics to detect patient positioning errors in radiotherapy observed through Cherenkov imaging, which may be used to optimize automated incident detection. METHODS: An anthropomorphic phantom mimicking patient vasculature, a biological marker seen in Cherenkov images, was simulated for a breast radiotherapy treatment. The phantom was systematically shifted in each translational direction, and Cherenkov images were captured during treatment delivery at each step. The responses of mutual information (MI) and the γ passing rate (%GP) were compared to that of existing field-shape matching image metrics, the Dice coefficient, and mean distance to conformity (MDC). Patient images containing other incidents were analyzed to verify the best detection algorithm for different incident types. RESULTS: Positional shifts in all directions were registered by both MI and %GP, degrading monotonically as the shifts increased. Shifts in intensity, which may result from erythema or bolus-tissue air gaps, were detected most by %GP. However, neither metric detected beam-shape misalignment, such as that caused by dose to unintended areas, as well as currently employed metrics (Dice and MDC). CONCLUSIONS: This study indicates that different radiotherapy incidents may be detected by comparing both inter- and intrafractional Cherenkov images with a corresponding image similarity metric, varying with the type of incident. Future work will involve determining appropriate thresholds per metric for automatic flagging. ADVANCES IN KNOWLEDGE: Classifying different algorithms for the detection of various radiotherapy incidents allows for the development of an automatic flagging system, eliminating the burden of manual review of Cherenkov images.

Clinical implementation of the first Cherenkov imaging system in a community-based hospital.

Purpose: To document experiences with one year of clinical implementation of the first Cherenkov imaging system and share the methods that we developed to utilize Cherenkov imaging to improve treatment delivery accuracy in real-time. Methods: A Cherenkov imaging system was installed commissioned and calibrated for clinical use. The optimal room lighting conditions and imaging setup protocols were developed to optimize both image quality and patient experience. The Cherenkov images were analyzed for treatment setup and beam delivery verification. Results: We have successfully implemented a clinical Cherenkov imaging system in a community-based hospital. Several radiation therapy patient setup anomalies were found in 1) exit dose to the contralateral breast, 2) dose to the chin due to head rotation for a supraclavicular field, 3) intrafractional patient motion during beam delivery, and 4) large variability (0.5 cm to 5 cm) in arm position between fractions. The system was used to deliver deep inspiration breath hold (DIBH) treatment delivery of an electron treatment beam. Clinical process and procedures were improved to mitigate the identified issues to ensure treatment delivery safety and to improve treatment accuracy. Conclusion: The Cherenkov imaging system has proven to be a valuable clinical tool for the improvement of treatment delivery safety and accuracy at our hospital. With only minimal training the therapists were able to adjust or correct treatment positions during treatment delivery as needed. With future Cherenkov software developments Cherenkov imaging systems could provide daily surface guided radiotherapy (SGRT) and real time treatment delivery quality control for all 3D and clinical setup patients without adding additional radiation image dose as in standard kV, MV and CBCT image verifications. Cherenkov imaging can greatly improve clinical efficiency and accuracy, making real time dose delivery consistency verification and SGRT a reality.

The American Society for Radiation Oncology 2017 Radiation Oncologist Workforce Study.

PURPOSE: The aim of this study is to report the American Society for Radiation Oncology 2017 radiation oncologist (RO) workforce survey results; identify demographic, technology utilization, and employment trends; and assess the profession's ability to meet patients' needs, offer job satisfaction, and attract high-caliber trainees. METHODS: In spring 2017, the American Society for Radiation Oncology distributed an online survey to 3856 US RO members. The questionnaire was patterned after the 2012 workforce survey for trend analysis. The 31% response rate yielded 1174 individual responses (726 practices) for analysis. RESULTS: ROs' mean age was 50.9 years. Compared to 2012, female representation (28.9%) increased and white representation (69.8%) dropped. The proportion in rural practice (12.6%) decreased, whereas the number of suburban ROs (40.6%) increased and urban ROs (46.8%) remained high. Most ROs worked full-time, averaging 51.4 h/wk. Stereotactic body radiation therapy, cone beam computed tomography, and magnetic resonance/positron emission tomography-computed tomography fusion utilization increased, whereas low-dose-rate brachytherapy decreased by >15 percentage points. Hypofractionation utilization was 95.3% and was highest in academic/university systems and lowest in private solo practices (P < .001). More respondents were concerned about an RO oversupply rather than shortage. ROs reported 250 consults (median) and 20 on-treatment patients (median) in 2016 and greater time allocation to electronic health record management compared with 3 years earlier. Approximately 15% of ROs reported job vacancies, which were more prevalent in urban practices and academic/university systems. ROs were employed by academic/university systems, private practices, and nonacademic hospitals in a respective ratio of 2:2:1. Comparison with 2012 survey findings showed a shift from private practice toward academic/university systems and nonacademic hospitals. Compensation was predominantly productivity-based at private practices and a fixed salary or a base salary at academic/university systems and nonacademic hospitals. Practice merger/buyout was the lead reason for ROs to change employers. CONCLUSIONS: Since 2012, race and gender gaps narrowed, but geographic disparities persisted, with ROs gravitating toward resource-rich suburban and urban locations over rural practices. The workforce has shifted from predominantly private practice to more equal balance with academic/university systems. These findings reflect the current US RO landscape and serve to underscore the need for collective action to ensure equitable RO care for all patients.