Feasibility of quantitative diffusion-weighted imaging during intra-procedural MRI-guided brachytherapy of locally advanced cervical and vaginal cancers.

PURPOSE: To determine the feasibility of quantitative apparent diffusion coefficient (ADC) acquisition during magnetic resonance imaging-guided brachytherapy (MRgBT) using reduced field-of-view (rFOV) diffusion-weighted imaging (DWI). METHODS AND MATERIALS: T2-weighted (T2w) MR and full-FOV single-shot echo planar (ssEPI) DWI were acquired in 7 patients with cervical or vaginal malignancy at baseline and prior to brachytherapy, while rFOV-DWI was acquired during MRgBT following brachytherapy applicator placement. The gross target volume (GTV) was contoured on the T2w images and registered to the ADC map. Voxels at the GTV's maximum Maurer distance comprised a central sub-volume (GTVcenter). Contour ADC mean and standard deviation were compared between timepoints using repeated measures ANOVA. RESULTS: ssEPI-DWI mean ADC increased between baseline and prebrachytherapy from 1.03 ± 0.18 10-3 mm2/s to 1.34 ± 0.28 10-3 mm2/s for the GTV (p = 0.06) and from 0.84 ± 0.13 10-3 mm2/s to 1.26 ± 0.25 10-3 mm2/s at the level of the GTVcenter (p = 0.03), consistent with early treatment response. rFOV-DWI during MRgBT demonstrated mean ADC values of 1.28 ± 0.14 10-3 mm2/s and 1.28 ± 0.19 10-3 mm2/s for the GTV and GTVcenter, respectively (p = 0.02 and p = 0.03 relative to baseline). No significant differences were observed between ssEPI-DWI and rFOV-DWI ADC measurements. CONCLUSIONS: Quantitative ADC measurement in the setting of MRI guided brachytherapy implant placement for cervical and vaginal cancers is feasible using rFOV-DWI, with comparable mean ADC comparable to prebrachytherapy ssEPI-DWI, and may enable MRI-guided radiotherapy targeting of low ADC, radiation resistant sub-volumes of tumor.

Hazard testing to reduce risk in the development of automated planning tools.

PURPOSE: Hazard scenarios were created to assess and reduce the risk of planning errors in automated planning processes. This was accomplished through iterative testing and improvement of examined user interfaces. METHODS: Automated planning requires three user inputs: a computed tomography (CT), a prescription document, known as the service request, and contours. We investigated the ability of users to catch errors that were intentionally introduced into each of these three stages, according to an FMEA analysis. Five radiation therapists each reviewed 15 patient CTs, containing three errors: inappropriate field of view, incorrect superior border, and incorrect identification of isocenter. Four radiation oncology residents reviewed 10 service requests, containing two errors: incorrect prescription and treatment site. Four physicists reviewed 10 contour sets, containing two errors: missing contour slices and inaccurate target contour. Reviewers underwent video training prior to reviewing and providing feedback for various mock plans. RESULTS: Initially, 75% of hazard scenarios were detected in the service request approval. The visual display of prescription information was then updated to improve the detectability of errors based on user feedback. The change was then validated with five new radiation oncology residents who detected 100% of errors present. 83% of the hazard scenarios were detected in the CT approval portion of the workflow. For the contour approval portion of the workflow none of the errors were detected by physicists, indicating this step will not be used for quality assurance of contours. To mitigate the risk from errors that could occur at this step, radiation oncologists must perform a thorough review of contour quality prior to final plan approval. CONCLUSIONS: Hazard testing was used to pinpoint the weaknesses of an automated planning tool and as a result, subsequent improvements were made. This study identified that not all workflow steps should be used for quality assurance and demonstrated the importance of performing hazard testing to identify points of risk in automated planning tools.

Addition of Metastasis-Directed Therapy to Intermittent Hormone Therapy for Oligometastatic Prostate Cancer: The EXTEND Phase 2 Randomized Clinical Trial.

Importance: Despite evidence demonstrating an overall survival benefit with up-front hormone therapy in addition to established synergy between hormone therapy and radiation, the addition of metastasis-directed therapy (MDT) to hormone therapy for oligometastatic prostate cancer, to date, has not been evaluated in a randomized clinical trial. Objective: To determine in men with oligometastatic prostate cancer whether the addition of MDT to intermittent hormone therapy improves oncologic outcomes and preserves time with eugonadal testosterone compared with intermittent hormone therapy alone. Design, Setting, Participants: The External Beam Radiation to Eliminate Nominal Metastatic Disease (EXTEND) trial is a phase 2, basket randomized clinical trial for multiple solid tumors testing the addition of MDT to standard-of-care systemic therapy. Men aged 18 years or older with oligometastatic prostate cancer who had 5 or fewer metastases and were treated with hormone therapy for 2 or more months were enrolled to the prostate intermittent hormone therapy basket at multicenter tertiary cancer centers from September 2018 to November 2020. The cutoff date for the primary analysis was January 7, 2022. Interventions: Patients were randomized 1:1 to MDT, consisting of definitive radiation therapy to all sites of disease and intermittent hormone therapy (combined therapy arm; n = 43) or to hormone therapy only (n = 44). A planned break in hormone therapy occurred 6 months after enrollment, after which hormone therapy was withheld until progression. Main Outcomes and Measures: The primary end point was disease progression, defined as death or radiographic, clinical, or biochemical progression. A key predefined secondary end point was eugonadal progression-free survival (PFS), defined as the time from achieving a eugonadal testosterone level (≥150 ng/dL; to convert to nanomoles per liter, multiply by 0.0347) until progression. Exploratory measures included quality of life and systemic immune evaluation using flow cytometry and T-cell receptor sequencing. Results: The study included 87 men (median age, 67 years [IQR, 63-72 years]). Median follow-up was 22.0 months (range, 11.6-39.2 months). Progression-free survival was improved in the combined therapy arm (median not reached) compared with the hormone therapy only arm (median, 15.8 months; 95% CI, 13.6-21.2 months) (hazard ratio, 0.25; 95% CI, 0.12-0.55; P < .001). Eugonadal PFS was also improved with MDT (median not reached) compared with the hormone therapy only (6.1 months; 95% CI, 3.7 months to not estimable) (hazard ratio, 0.32; 95% CI, 0.11-0.91; P = .03). Flow cytometry and T-cell receptor sequencing demonstrated increased markers of T-cell activation, proliferation, and clonal expansion limited to the combined therapy arm. Conclusions and Relevance: In this randomized clinical trial, PFS and eugonadal PFS were significantly improved with combination treatment compared with hormone treatment only in men with oligometastatic prostate cancer. Combination of MDT with intermittent hormone therapy may allow for excellent disease control while facilitating prolonged eugonadal testosterone intervals. Trial Registration: ClinicalTrials.gov Identifier: NCT03599765.

AAPM medical physics practice guideline 13.a: HDR brachytherapy, part A.

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines (MPPGs) will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. The following terms are used in the AAPM practice guidelines: (1) Must and must not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. (2) Should and should not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances. Approved by AAPM's Executive Committee April 28, 2022.

AAPM BTSC Report 377: Physicist Brachytherapy Training in 2021-A survey of therapeutic medical physics residency program directors.

BACKGROUND: Brachytherapy (BT) was the first radiotherapeutic technique used to treat human disease and remains an essential modality in radiation oncology. A decline in the utilization of BT as a treatment modality has been observed and reported, which may impact training opportunities for medical physics residents. A survey of therapeutic medical physics residency program directors was performed as part of an assessment of the current state of BT training during residency. METHODS: In March 2021, a survey consisting of 23 questions was designed by a working unit of the Brachytherapy Subcommittee of the American Association of Physicists in Medicine (AAPM) and approved for distribution by the Executive Committee of the AAPM. The survey was distributed to the directors of the Commission on Accreditation of Medical Physics Education Programs (CAMPEP)-accredited therapeutic medical physics residency programs by the AAPM. The participant response was recorded anonymously in an online platform and then analyzed using MATLAB and Microsoft Excel software. RESULTS: The survey was distributed to the program directors of 110 residency programs. Over the course of 6 weeks, 72 directors accessed the survey online, and 55 fully completed the survey. Individual responses from the directors (including partial submissions) were evaluated and analyzed. Nearly all participating programs (98%) utilize high dose rate BT treatments with 74% using low dose rate BT techniques. All programs treated gynecological sites using BT, and the next most common treatment sites were prostate (80%) and breast (53%). Overall, the residency program directors had a positive outlook toward BT as a radiotherapeutic treatment modality. Caseload and time limitations were identified as primary barriers to BT training by some programs. CONCLUSIONS: Based on the responses of the program directors, it was identified that the residency programs might benefit from additional resources such as virtual BT training, interinstitutional collaborations as well as resident fellowships. Programs might also benefit from additional guidance related to BT-specific training requirements to help program directors attest Authorized Medical Physicist eligibility for graduating residents.

Gender-Based Discrimination and Sexual Harassment in Medical Physics.

PURPOSE: Gender-based discrimination and sexual harassment have been well-studied in the fields of science, technology, engineering, math, and medicine. However, less is known about these topics and their effect within the profession of medical physics. We aimed to better understand and clarify the views and experiences of practicing medical physicists and medical physics residents regarding gender-based discrimination and sexual harassment. METHODS AND MATERIALS: We conducted in-depth, semistructured, and confidential interviews with 32 practicing medical physicists and medical physics residents across the United States. The interviews were broad and covered the topics of discrimination, mentorship, and work/life integration. All participants were associated with a department with a residency program accredited by the Commission on Accreditation of Medical Physics Education Programs and had appointments with a clinical component. RESULTS: Participants shared views about gender-based discrimination and sexual harassment that were polarized. Some perceived that discrimination and harassment were a current concern within medical physics, while some either perceived that they were not a concern or that discrimination positively affected women and minoritized populations. Many participants shared personal experiences of discrimination and harassment, including those related to unequal compensation, discrimination against mothers, discrimination during the hiring process, gender-biased assumptions about behaviors or goals, communication biases, and overt and persistent sexual harassment. CONCLUSIONS: There is an urgent need to acknowledge, better understand, and address gender-based discrimination and sexual harassment in the field of medical physics.

Learning from the past: a century of accuracy, aspirations, and aspersions in brachytherapy.

The oldest form of radiation therapy, brachytherapy, has been investigated and reported in the scientific and medical literature for well over a century. Known by many names over the years, radium-based, empirical practices evolved over decades to contemporary practice. This includes treatment at various dose rates using multiple radionuclides or even electrically generated photon sources. Predictions or prognostications of what may happen in the future enjoy a history that spans centuries, e.g. those by Nostradamus in the 1500s. In this review article, publications from several eras of past practice between the early 1900s and the late 2010s where the authors address the "future of brachytherapy" are presented, and for many of these publications, one can use the benefit of the intervening years to comment on the accuracy or the inaccuracies inherent in those publications. Finally, recently published papers are reviewed to examine current expectations for the future practice of brachytherapy.

Contemporary image-guided cervical cancer brachytherapy: Consensus imaging recommendations from the Society of Abdominal Radiology and the American Brachytherapy Society.

PURPOSE: To present recommendations for the use of imaging for evaluation and procedural guidance of brachytherapy for cervical cancer patients. METHODS: An expert panel comprised of members of the Society of Abdominal Radiology Uterine and Ovarian Cancer Disease Focused Panel and the American Brachytherapy Society jointly assessed the existing literature and provide data-driven guidance on imaging protocol development, interpretation, and reporting. RESULTS: Image-guidance during applicator implantation reduces rates of uterine perforation by the tandem. Postimplant images may be acquired with radiography, computed tomography (CT), or magnetic resonance imaging (MRI), and CT or MRI are preferred due to a decrease in severe complications. Pre-brachytherapy T2-weighted MRI may be used as a reference for contouring the high-risk clinical target volume (HR-CTV) when CT is used for treatment planning. Reference CT and MRI protocols are provided for reference. CONCLUSIONS: Image-guided brachytherapy in locally advanced cervical cancer is essential for optimal patient management. Various imaging modalities, including orthogonal radiographs, ultrasound, computed tomography, and magnetic resonance imaging, remain integral to the successful execution of image-guided brachytherapy.

Gender Differences in Work-Life Integration Among Medical Physicists.

PURPOSE: To generate an understanding of the primary concerns facing medical physicists regarding integration of a demanding technical career with their personal lives. METHODS AND MATERIALS: In 2019, we recruited 32 medical physics residents, faculty, and staff via emails to US medical physics residency program directors to participate in a 1-hour, semistructured interview that elicited their thoughts on several topics, including work-life integration. Standard techniques of qualitative thematic analysis were used to generate the research findings. RESULTS: Of the participants, 50% were women and 69% were non-Hispanic White individuals, with a mean (SD) age of 37.5 (7.4) years. They were evenly split between residents and faculty or staff. Participant responses centered around 5 primary themes: the gendered distribution of household responsibilities, the effect of career or work on home and family life, the effect of family on career or work, support and strategies for reconciling work-life conflicts, and the role of professional societies in addressing work-life integration. Participants expressed concern about the effect of heavy workloads on home life, with female respondents more likely to report carrying the majority of the household burden. CONCLUSIONS: Medical physicists experience challenges in managing work-life conflict amid a diverse array of personal and professional responsibilities. Further investigations are needed to quantitatively assess the division of work and household labor by gender in medical physics, particularly after the outbreak of the COVID-19 pandemic, but this study's qualitative findings suggest that the profession should consider ways to address root causes of work-life conflict to promote the future success and well-being of all medical physicists, and perhaps women in particular.

Dose-rate considerations for the INTRABEAM electronic brachytherapy system: Report from the American association of physicists in medicine task group no. 292.

The purpose of this report is to provide detailed guidance on the dosimetry of the INTRABEAM® (Carl Zeiss Medical AG, Jena, Germany) electronic brachytherapy (eBT) system as it stands at the present time. This report has been developed by the members of American Association of Physicists in Medicine (AAPM) Task Group 292 and endorsed by the AAPM. Members of AAPM Task Group 292 on Electronic-Brachytherapy Dosimetry have reviewed pertinent publications and user manuals regarding the INTRABEAM system dosimetry and manufacturer-supplied dose calculation protocols. Formal written correspondence with Zeiss has also provided further clarification. Dose-rate calculations for the INTRABEAM system are highly dependent on choice of dosimetry protocol. Even with careful protocol selection, large uncertainties remain due to the incomplete characterization of the ionization chambers used for verification with respect to their energy dependence as well as manufacturing variations. There are two distinct sets of dose-rate data provided by Zeiss for the INTRABEAM system. One dataset (Calibration V4.0) is representative of the physical dose surrounding the source and the other dataset (TARGIT) has been adjusted to be consistent with a clinical trial named TARGIT (TARGeted Intraoperative RadioTherapy). The adjusted TARGIT doses are quite dissimilar to the physical doses, with differences ranging from 14% to 30% at the surface of a spherical applicator, depending on its diameter, and up to a factor of two at closer distances with the smaller needle applicators. In addition, ion chamber selection and associated manufacturing tolerances contribute to significant additional uncertainties. With these substantial differences in dose rates and their associated uncertainties, it is important for users to be aware of how each value is calculated and whether it is appropriate to be used for the intended treatment. If users intend to deliver doses that are the same as they were in 1998 at the onset of the TARGIT trial, then the TARGIT dose-rate tables should be used. The Calibration V4.0 dose rates may be more appropriate to use for applications other than TARGIT trial treatments, since they more closely represent the physical doses being delivered. Users should also be aware of the substantial uncertainties associated with the provided dose rates, which are due to beam hardening, chamber geometry, and selection of the point-of-measurement for a given ionization chamber. This report serves to describe the details and implications of the manufacturer-recommended dosimetry formalism for users of the INTRABEAM system.

Development and comprehensive commissioning of an automated brachytherapy plan checker.

PURPOSE: To present on the commissioning of an automated brachytherapy plan checker (BPC) for the evaluation of high-dose-rate brachytherapy treatment plans in support of standardized workflows and patient safety. METHODS AND MATERIALS: A BPC was developed using an applications programming interface in a commercial treatment planning system based on different inputs (e.g., regulations, professional society recommendations, and user feedback) and leveraged our experience with an in-house developed external beam plan checker. The BPC was commissioned using a comprehensive suite of test plans with known errors and anonymized clinical plans. RESULTS: During commissioning, the BPC was successfully executed on a total of 87 test plans. Commissioning tests spanned a range of treatment sites and evaluated that pass and fail states were correct. Administration settings were changed in a nonclinical database to evaluate tests involving the source and afterloader. Clinical testing of the BPC was then performed in parallel with a manual review process before clinical implementation. CONCLUSIONS: To commission the BPC for clinical use, a comprehensive suite of test plans was developed and used to ensure the BPC correctly detected and reported errors. A summary of the test plans is presented to help guide users developing similar automated tools. The BPC represents a process-improvement initiative designed to reduce errors and improve safety for brachytherapy patients. By using a comprehensive test suite for commissioning, tests are available for periodic quality assurance and after software upgrades.

A modified dose calculation formalism for electronic brachytherapy sources.

PURPOSE: To propose a modification of the current dose calculation formalism introduced in the Task Group No. 43 Report (TG-43) to accommodate an air-kerma rate standard for electronic brachytherapy sources as an alternative to an air-kerma strength standard. METHODS: Electronic brachytherapy sources are miniature x-ray tubes emitting low energies with high-dose-rates. The National Institute of Standards and Technology (NIST) has introduced a new primary air-kerma rate standard for one of these sources, in contrast to air-kerma strength. A modification of the TG-43 protocol for calculation of dose-rate distributions around electronic brachytherapy sources including sources in an applicator is presented. It cannot be assumed that the perturbations from sources in an applicator are negligible, and thus, the applicator is incorporated in the formalism. The modified protocol mimics the fundamental methodology of the original TG-43 formalism, but now incorporates the new NIST-traceable source strength metric of air-kerma rate at 50 cm and introduces a new subscript, i, to denote the presence of an applicator used in treatment delivery. Applications of electronic brachytherapy sources for surface brachytherapy are not addressed in this Technical Note since they are well documented in other publications. RESULTS: A modification of the AAPM TG-43 protocol has been developed to accommodate an air-kerma rate standard for electronic brachytherapy sources as an alternative to an air-kerma strength standard. CONCLUSIONS: The modified TG-43 formalism allows dose calculations to be performed using a new NIST-traceable source strength metric and introduces the concept of applicator-specific formalism parameters denoted with subscript, i.