This characterization of a new (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.

Magnetic resonance imaging (MRI) offers outstanding soft tissue contrast that may reduce uncertainties in target and organ-at-risk delineation and enable online adaptive image-guided treatment. Spatial distortions resulting from non-linearities in the gradient fields and nonuniformity in the main magnetic field must be accounted for across the imaging field-of-view to prevent systematic errors during treatment delivery. This work presents a modular phantom and software application to characterize geometric distortion (GD) within the large field-of-view MRI images required for radiation therapy simulation. The modular phantom is assembled from a series of rectangular foam blocks containing high-contrast fiducial markers in a known configuration. The modular phantom design facilitates transportation of the phantom between different MR scanners and MR-guided linear accelerators and allows the phantom to be adapted to fit different sized bores or coils. The phantom was evaluated using a 1.5 T MR-guided linear accelerator (MR-Linac) and 1.5 T and 3.0 T diagnostic scanners. Performance was assessed by varying acquisition parameters to induce image distortions in a known manner. Imaging was performed using T1 and T2 weighted pulse sequences with 2D and 3D distortion correction algorithms and the receiver bandwidth (BW) varied as 250-815 Hz pixel −1 . Phantom set-up reproducibility was evaluated across independent set-ups. The software was validated by comparison with a non-modular phantom. Average geometric distortion was 0.94 ± 0.58 mm for the MR-Linac, 0.90 ± 0.53 mm

Primary S measurements of the CivaDot demonstrated good repeatability and reproducibility of the free-air chamber measurements. Measurements of the CivaDot dose distribution using the EBT3 film stack phantom and its subsequent comparison to Monte Carlo-predicted dose distributions were encouraging, given the overall uncertainties. This work will aid in the eventual realization of a clinically viable dosimetric framework for the CivaSheet based on the CivaDot dose distribution.

The differences between the SK measurements determined from the seven-distance technique and the accredited UWADCL measurement results were within the k = 2 uncertainty reported for an accredited calibration. Excellent agreement was found between the measured SK and RAKR methods used at the UWMRRC and PTB, respectively. Additionally, the sensitivity study has shown that the seven-distance algorithm accurately determines the SK of a source while having a variable chamber offset among nominal positions; the uncertainty budget for the seven-distance method does not need to be expanded at this time. It has been determined that the current standard used by the UWADCL for well chamber calibrations is valid for the Bebig model Ir2.A85-2 192Ir brachytherapy source.

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, for example 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.

Purpose: The aim of this work is to propose a method to optimize radioactive source localization (RSL) for non‐palpable breast cancer surgery. RSL is commonly used as a guiding technique during surgery for excision of non‐palpable tumors. A collimated hand‐held detector is used to localize radioactive sources implanted in tumors. Incisions made by the surgeon are based on maximum observed detector counts, and tumors are subsequently resected based on an arbitrary estimate of the counts expected at the surgical margin boundary. This work focuses on building a framework to predict detector counts expected throughout the procedure to improve surgical margins. Methods: A gamma detection system called the Neoprobe GDS was used for this work. The probe consists of a cesium zinc telluride crystal and a collimator. For this work, an I‐125 Best Medical model 2301 source was used. The source was placed in three different phantoms, a PMMA, a Breast (25%‐ glandular tissue/75%‐ adipose tissue) and a Breast (75‐25) phantom with a backscatter thickness of 6 cm. Counts detected by the probe were recorded with varying amounts of phantom thicknesses placed on top of the source. A calibration curve was generated using MATLAB based on the counts recorded for the calibration dataset acquired with the PMMA phantom. Results: The observed detector counts data used as the validation set was accurately predicted to within ±3.2%, ±6.9%, ±8.4% for the PMMA, Breast (75‐25), Breast (25–75) phantom respectively. The average difference between predicted and observed counts was −0.4%, 2.4%, 1.4% with a standard deviation of 1.2 %, 1.8%, 3.4% for the PMMA, Breast (75‐25), Breast (25–75) phantom respectively. Conclusion: The results of this work provide a basis for characterization of a detector used for RSL. Counts were predicted to within ±9% for three different phantoms without the application of a density correction factor.

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.

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