The AAPM/ASTRO 2023 Core Physics Curriculum for Radiation Oncology Residents.

PURPOSE: The American Association of Physicists in Medicine Radiation Oncology Medical Physics Education Subcommittee (ROMPES) has updated the radiation oncology physics core curriculum for medical residents in the radiation oncology specialty. METHODS AND MATERIALS: Thirteen physicists from the United States and Canada involved in radiation oncology resident education were recruited to ROMPES. The group included doctorates and master's of physicists with a range of clinical or academic roles. Radiation oncology physician and resident representatives were also consulted in the development of this curriculum. In addition to modernizing the material to include new technology, the updated curriculum is consistent with the format of the American Board of Radiology Physics Study Guide Working Group to promote concordance between current resident educational guidelines and examination preparation guidelines. RESULTS: The revised core curriculum recommends 56 hours of didactic education like the 2015 curriculum but was restructured to provide resident education that facilitates best clinical practice and scientific advancement in radiation oncology. The reference list, glossary, and practical modules were reviewed and updated to include recent literature and clinical practice examples. CONCLUSIONS: ROMPES has updated the core physics curriculum for radiation oncology residents. In addition to providing a comprehensive curriculum to promote best practice for radiation oncology practitioners, the updated curriculum aligns with recommendations from the American Board of Radiology Physics Study Guide Working Group. New technology has been integrated into the curriculum. The updated curriculum provides a framework to appropriately cover the educational topics for radiation oncology residents in preparation for their subsequent career development.

Considerations for intensity modulated total body or total marrow and lymphoid irradiation.

We compiled a sampling of the treatment techniques of intensity-modulated total body irradiation, total marrow irradiation and total marrow and lymphoid irradiation utilized by several centers across North America and Europe. This manuscript does not serve as a consensus guideline, but rather is meant to serve as a convenient reference for centers that are considering starting an intensity-modulated program.

Different Re-Irradiation Techniques after Breast-Conserving Surgery for Recurrent or New Primary Breast Cancer.

Breast re-irradiation (reRT) after breast-conserving surgery (BCS) using external beam radiation is an increasingly used salvage approach for women presenting with recurrent or new primary breast cancer. However, radiation technique, dose and fractionation as well as eligibility criteria differ between studies. There is also limited data on efficacy and safety of external beam hypofractionation and accelerated partial-breast irradiation (APBI) regimens. This paper reviews existing retrospective and prospective data for breast reRT after BCS, APBI reRT outcomes and delivery at our institution and the need for a randomized controlled trial using shorter courses of radiation to better define patient selection for different reRT fractionation regimens.

Accelerated partial breast irradiation in early stage breast cancer.

Accelerated partial breast irradiation (APBI) is increasingly used to treat select patients with early stage breast cancer. However, radiation technique, dose and fractionation as well as eligibility criteria differ between studies. This has led to controversy surrounding appropriate patients for APBI and an assessment of the toxicity and cosmetic outcomes of APBI as compared to whole breast irradiation (WBI). This paper reviews existing data for APBI, APBI delivery at our institution, and ongoing research to better define patient selection, treatment delivery, dosimetric considerations and toxicity outcomes.

Pulmonary Toxic Effects After Myeloablative Conditioning With Total Body Irradiation Delivered via Volumetric Modulated Arc Therapy With Fludarabine.

We present the case of a 56-year-old female with a diagnosis of acute T-cell lymphoblastic leukemia who received myeloablative conditioning for bone marrow transplant with total body irradiation (TBI) using volumetric modulated arc therapy (VMAT) to the upper body and anterior-posterior/posterior-anterior (AP/PA) open fields to the lower body followed by hematopoietic stem cell transplant. Her clinical course was complicated by high-grade pulmonary toxic effects 55 days after treatment that resulted in death. We discuss the case, planning considerations by radiation oncologists and radiation physicists, and the multidisciplinary medical management of this patient.

Interprofessional Image Verification Workshop for Physician and Physics Residents: A Multi-Institutional Experience.

PURPOSE: Verification of patient position through pretreatment setup imaging is crucial in modern radiation therapy. As treatment complexity increases and technology evolves, physicist-physician collaboration becomes imperative for safe and successful radiation delivery. Despite the importance of both, residency programs lack formal interprofessional education (IPE) activities or structured training for image verification. Here we show the impact of an interprofessional image verification workshop for residents in a multi-institutional setting. METHODS: The workshop included a lecture by the attending physicist and physician, and hands-on image registration practice by learners (medical physics residents, MP; and radiation oncology residents, RO). All participants filled out pre- and postactivity surveys and rated their comfort from 1 to 10 in (A) selecting what type of imaging to order for a given case and (B) independently assessing the setup quality based on imaging. A paired 1-tailed t test (α = 0.05) was used to evaluate significance; Spearman rank correlation coefficient was used to assess correlation of ratings and RO postgraduate year (PGY). Surveys had free-response questions about IPE and image verification activities in residency. RESULTS: A total of 71 residents from 7 institutions participated between 2018 and 2020. Pre- and postsurveys were completed by 50 residents (38RO, 12MP) and showed an increase in (A) from 5.5 ± 2.2 to 7.1 ± 1.6 (P < .001) and in (B) from 5.1 ± 2.3 to 6.8 ± 1.5 (P < .001), with significant increases per subgroup (AΔ, RO = 1.8 ± 1.7, P < .001; BΔ, RO = 1.9 ± 1.8, P <. 001; AΔ, MP = 1.1 ± 1.4, P = .012; BΔ, MP = 1.2 ± 1.6, P = .016). RO confidence scores moderately correlated with PGY. Survey responses indicated that image verification training is mostly unstructured, with extent of exposure varying by program and attending; most with little-to-no training. Time constraints were identified as the main barrier. IPE was noted as a useful way to incorporate different perspectives into the process. CONCLUSIONS: Formal image verification training increases resident comfort with setup imaging review and provides opportunities for interprofessional collaboration in radiation oncology residency programs.

Assessing the reproducibility of CBCT-derived radiomics features using a novel three-dimensional printed phantom.

PURPOSE: Radiomics modeling is an exciting avenue for enhancing clinical decision making and personalized treatment. Radiation oncology patients often undergo routine imaging for position verification, particularly using LINAC-mounted cone beam computed tomography (CBCT). The wealth of imaging data collected in modern radiation therapy presents an ideal use case for radiomics modeling. Despite this, texture feature (TF) calculation can be limited by concerns over feature stability and reproducibility; in theory, this issue is compounded by the relatively poor image quality of CBCT, as well as variation of acquisition and reconstruction parameters. METHODS: In this study, we developed and validated a novel three-dimensional (3D) printed phantom for evaluating CBCT-based TF reliability. The phantom has a cylindrical shape (22 cm diameter and 25.5 cm height) with five inner inserts designed to hold custom-printed rods (1 cm diameter and 10-20 cm height) of various materials, infill shapes, and densities. TF reproducibility was evaluated across and within three LINACs from a single vendor using sets of three consecutive CBCT taken with the head, thorax, and pelvis clinical imaging protocols. PyRadiomics was used to extract a standard set of TFs from regions of interest centered on each rod. Two-way mixed effects absolute agreement intra-class correlation coefficient (ICC) was used to evaluate TF reproducibility, with features showing ICC values above 0.9 considered robust if their Bonferroni-corrected p-value was below 0.05. RESULTS: A total of 63, 87, and 83 features exhibited test-retest reliability for the head, thorax, and pelvis imaging protocols respectively. When assessing stability between discreet imaging sessions on the same LINAC, these numbers were reduced to 5, 63, and 70 features, respectively. The thorax and pelvis protocols maintained a rich candidate feature space in inter-LINAC analysis with 61 and 65 features, respectively, exceeding the ICC criteria. Crucially, no features were deemed reproducible when compared between protocols. CONCLUSIONS: We have developed a 3D phantom for consistent evaluation of TF stability and reproducibility. For LINACs from a single vendor, our study found a substantial number of features available for robust radiomics modeling from CBCT imaging. However, some features showed variations across LINACs. Studies involving CBCT-based radiomics must preselect features prior to their use in clinical-based models.

Automatic treatment planning for VMAT-based total body irradiation using Eclipse scripting.

The purpose of this work is to establish an automated approach for a multiple isocenter volumetric arc therapy (VMAT)-based TBI treatment planning approach. Five anonymized full-body CT imaging sets were used. A script was developed to automate and standardize the treatment planning process using the Varian Eclipse v15.6 Scripting API. The script generates two treatment plans: a head-first VMAT-based plan for upper body coverage using four isocenters and a total of eight full arcs; and a feet-first AP/PA plan with three isocenters that covers the lower extremities of the patient. PTV was the entire body cropped 5 mm from the patient surface and extended 3 mm into the lungs and kidneys. Two plans were generated for each case: one to a total dose of 1200 cGy in 8 fractions and a second one to a total dose of 1320 cGy in 8 fractions. Plans were calculated using the AAA algorithm and 6 MV photon energy. One plan was created and delivered to an anthropomorphic phantom containing 12 OSLDs for in-vivo dose verification. For the plans prescribed to 1200 cGy total dose the following dosimetric results were achieved: median PTV V100% = 94.5%; median PTV D98% = 89.9%; median lungs Dmean = 763 cGy; median left kidney Dmean = 1058 cGy; and median right kidney Dmean = 1051 cGy. For the plans prescribed to 1320 cGy total dose the following dosimetric results were achieved: median PTV V100% = 95.0%; median PTV D98% = 88.7%; median lungs Dmean = 798 cGy; median left kidney Dmean = 1059 cGy; and median right kidney Dmean = 1064 cGy. Maximum dose objective was met for all cases. The dose deviation between the treatment planning dose and the dose measured by the OSLDs was within ±4%. In summary, we have demonstrated that scripting can produce high-quality plans based on predefined dose objectives and can decrease planning time by automatic target and optimization contours generation, plan creation, field and isocenter placement, and optimization objectives setup.

Glamour, expression, and consequences of tattoos in radiation treatment.

It is estimated that approximately 24% of the US population has at least one tattoo. However, tattoo ink ingredients include heavy metals (high atomic number Z) that are not regulated, which can cause skin reactions. This study investigates the dosimetric effects in surface dose due to high-Z elements in tattoo ink under electron beam irradiation. Four commercially available tattoo ink colors, black, red, yellow, and blue were chosen. The elemental composition of the tattoo ink samples was analyzed using X-ray Fluorescence (XRF). An ultrathin-window parallel plate ion chamber was used to measure the surface dose perturbation (ratio of ionizations with and without tattoo ink) for 6 - 20 MeV electron beams. The elemental concentration in the tattoo ink samples showed high-Z elements, with Z ranging from 11 to 92. The dose perturbation ranged from 1.4% up to 6% for the yellow ink for the 6 MeV electron beam, with similar values across the rest of the electron energies, whereas the black, red, and blue inks presented up to 3% dose perturbation for the same range of energies. Based on this initial study, we conclude that commercially available tattoo inks contain large amounts of high-Z metals that may contribute to dose perturbation. Therefore treatment of superficial lesions with electron beams in a tattooed area should be monitored for signs of early skin reaction during radiation therapy treatments.

Characterization of the plastic scintillation detector Exradin W2 for small field dosimetry.

PURPOSE: Small field dosimetry has been an active area of research for over a decade. It is now known that large dosimetric errors can be introduced if proper detectors or correction factors are not used. The International Atomic Energy Agency (IAEA) through the technical report series No. 483 provides guidelines for small field dosimetry procedures as well as correction factors for most detectors available in the market. The plastic scintillator detector (PSD) Exradin W1 has been found to have a correction factor close to unity; however, it is not designed for beam scanning. To overcome this limitation, the new PSD Exradin W2 has been developed to be used as a scanning as well as a relative dosimeter. Characterization of this detector in small field dosimetry is presented in this study. METHODS: A 6 MV beam from a Varian-Edge linac was used to collect data for the characterization of a W2 detector. Cerenkov light ratio (CLR) is corrected through a separate new electrometer system that comes with the W2 detector. The parameters investigated include the dose and dose rate linearity, beam profiles, percent depth dose (PDD), field output factors, and temperature response. The results were compared with Gafchromic film (EBT-3 film) for beam profiles. The field output factor and temperature response were compared to the Exradin W1 detector. RESULTS: The dose linearity measured with 600 MU/min dose rate showed minimal variations (<0.5%) even for small MU, and similar results were seen for dose rate linearity. The comparison of field output factors between the W2 and W1 showed small differences for various depth and field sizes. The temperature response showed small variation when the temperature was varied from 6 ∘ C to 50 ∘ C . The slope was - 0.0017 / ∘ C and - 0.0016 / ∘ C for the W2 and the W1 detector, respectively. The differences in profiles are 0.5% in umbra and penumbra region for 1 × 1 cm 2 field size when compared to the EBT-3 film profile. CONCLUSIONS: The W2 scintillator detector showed similar dosimetric and temperature properties to the W1 scintillator detector. The main advantage of the W2 detector among other plastic scintillators is the beam scanning capabilities that, combined with its correction factor of 1.0, make it an ideal detector for commissioning of SRS and SBRT techniques.

Toward a standard for the evaluation of PET-Auto-Segmentation methods following the recommendations of AAPM task group No. 211: Requirements and implementation.

PURPOSE: The aim of this paper is to define the requirements and describe the design and implementation of a standard benchmark tool for evaluation and validation of PET-auto-segmentation (PET-AS) algorithms. This work follows the recommendations of Task Group 211 (TG211) appointed by the American Association of Physicists in Medicine (AAPM). METHODS: The recommendations published in the AAPM TG211 report were used to derive a set of required features and to guide the design and structure of a benchmarking software tool. These items included the selection of appropriate representative data and reference contours obtained from established approaches and the description of available metrics. The benchmark was designed in a way that it could be extendable by inclusion of bespoke segmentation methods, while maintaining its main purpose of being a standard testing platform for newly developed PET-AS methods. An example of implementation of the proposed framework, named PETASset, was built. In this work, a selection of PET-AS methods representing common approaches to PET image segmentation was evaluated within PETASset for the purpose of testing and demonstrating the capabilities of the software as a benchmark platform. RESULTS: A selection of clinical, physical, and simulated phantom data, including "best estimates" reference contours from macroscopic specimens, simulation template, and CT scans was built into the PETASset application database. Specific metrics such as Dice Similarity Coefficient (DSC), Positive Predictive Value (PPV), and Sensitivity (S), were included to allow the user to compare the results of any given PET-AS algorithm to the reference contours. In addition, a tool to generate structured reports on the evaluation of the performance of PET-AS algorithms against the reference contours was built. The variation of the metric agreement values with the reference contours across the PET-AS methods evaluated for demonstration were between 0.51 and 0.83, 0.44 and 0.86, and 0.61 and 1.00 for DSC, PPV, and the S metric, respectively. Examples of agreement limits were provided to show how the software could be used to evaluate a new algorithm against the existing state-of-the art. CONCLUSIONS: PETASset provides a platform that allows standardizing the evaluation and comparison of different PET-AS methods on a wide range of PET datasets. The developed platform will be available to users willing to evaluate their PET-AS methods and contribute with more evaluation datasets.

Variability of textural features in FDG PET images due to different acquisition modes and reconstruction parameters.

BACKGROUND: Characterization of textural features (spatial distributions of image intensity levels) has been considered as a tool for automatic tumor segmentation. The purpose of this work is to study the variability of the textural features in PET images due to different acquisition modes and reconstruction parameters. MATERIAL AND METHODS: Twenty patients with solid tumors underwent PET/CT scans on a GE Discovery VCT scanner, 45-60 minutes post-injection of 10 mCi of [(18)F]FDG. Scans were acquired in both 2D and 3D modes. For each acquisition the raw PET data was reconstructed using five different reconstruction parameters. Lesions were segmented on a default image using the threshold of 40% of maximum SUV. Fifty different texture features were calculated inside the tumors. The range of variations of the features were calculated with respect to the average value. RESULTS: Fifty textural features were classified based on the range of variation in three categories: small, intermediate and large variability. Features with small variability (range ≤ 5%) were entropy-first order, energy, maximal correlation coefficient (second order feature) and low-gray level run emphasis (high-order feature). The features with intermediate variability (10% ≤ range ≤ 25%) were entropy-GLCM, sum entropy, high gray level run emphsis, gray level non-uniformity, small number emphasis, and entropy-NGL. Forty remaining features presented large variations (range > 30%). CONCLUSION: Textural features such as entropy-first order, energy, maximal correlation coefficient, and low-gray level run emphasis exhibited small variations due to different acquisition modes and reconstruction parameters. Features with low level of variations are better candidates for reproducible tumor segmentation. Even though features such as contrast-NGTD, coarseness, homogeneity, and busyness have been previously used, our data indicated that these features presented large variations, therefore they could not be considered as a good candidates for tumor segmentation.