arXiv subjects

Scott B. Crowe

Publications and source records attributed to Scott B. Crowe.

8 recordsLinked to original sources

arXiv2026

Diversity, Equity and Inclusivity in the Australian and New Zealand Medical Physics Workforce

The consideration of diversity, equity and inclusivity (DEI) is an important part of promoting a robust and respectful workforce, and is critical to the continued success of organisations, including healthcare providers, academic institutions and professional societies. Many professional bodies representing medical physicists have made commitments to DEI principles in the form of mission statements, policies, steering groups, frameworks and workforce surveys. In the Australian and New Zealand medical physics community, DEI work has included reflecting on the impact of stereotypes, surveys on workforce experiences, and capturing workforce diversity metrics (including gender, nationality, age and professional background). These projects have been conducted with the support of the Australasian College of Physical Sciences and Engineering in Medicine (ACPSEM) and have contributed to the enhancement of DEI in the ACPSEM workforce. Most of this work has been focused on gender diversity, reflecting increasing involvement in the Australian and New Zealand workforce: women accounted for 41\% of medical physics trainees and 32\% of registered medical physicists in a 2020 survey. In 2021, the ACPSEM Professional Standards Board (PSB) incepted the creation of a DEI working group. This movement was supported not only by the ACPSEM Board but also the wider medical physics community, both nationally and inter-nationally. The establishment of this group will support best-practice governance, define the diversity metrics most relevant to our profession and use data collected on these metrics to effect positive change within the ACPSEM boards and committees as well as embedding DEI in policies and procedures for internal and external activities. The DEI working group will enhance the ACPSEM's reputation and ultimately ensure all members feel empowered, respected and represented.

physics.ed-ph↗

arXiv2026

Magnetic resonance imaging assessment of the suitability and consistency of radiotherapy treatment positioning achieved using intra-oral stents

As head-and-neck radiotherapy treatments grow more complex and precise, it becomes increasingly important to assess the anatomical separations that can be achieved using intra-oral stents. A series of twenty T2-weighted turbo spin echo magnetic resonance images (MRI) were acquired of one healthy participant, with a range of different wax and 3D printed intra-oral stents in situ. The resulting measurements showed that a 3D printed modular stent containing hard polylactic acid (PLA) and flexible thermoplastic polyurethane (TPU) components made the largest and most reproducible separation between the cheeks (70.8 +/- 0.3 mm), two hard PLA stents designed to exactly fit the participant's teeth produced the poorest positioning reproducibility (standard deviations of up to 3 mm between a range of landmarks measured in repeated images). Most stents were described as ``comfortable'' although the wax stents left small pieces of wax attached to the teeth after use. This MRI based comparison demonstrated that the materials and designs used for intra-oral stents can have substantial effects on the level of anatomical separation and positioning reproducibility that they produce.

physics.med-ph↗

arXiv2026

Generation of synthetic CT images from optical scanning for superficial mold brachytherapy

Optical 3D scanning systems allow the acquisition of accurate models of patient anatomy, suitable for use in the design of simple 3D-printable patient-matched medical devices with 3D modelling software. This study developed and demonstrated the use of superficial brachytherapy surface mold design workflow that utilizes data from optical 3D surface scanning and enables a commercial brachytherapy treatment planning system to be used for catheter positioning and dose optimization steps. Synthetic CT images were generated from 14 optically scanned anatomical models of human participants. Models and skin textures ac-quired from the optical scans were imported into Autodesk Meshmixer, where the treatment area was delineated, and treatment and device volumes produced. 3D Slicer was used to convert the body, treatment and device volumes to DICOM CT and RTSTRUCT data. The synthetic CT data and contoured volumes were imported into Varian Eclipse, where catheters were designed, and dwell positions and times optimised for dose coverage of the treatment volume. The lack of in-ternal anatomy did not compromise dose calculations, due to clinical use of a TG43 based algorithm. Once 3D printed, molds can be imaged in-situ during CT simulation, and reconstructed, for clinical dose calculation and plan approval.

physics.med-ph↗

arXiv2026

Characteristics of a 9 MeV electron beam for total skin electron radiotherapy evaluated in comparison to a 6 MeV electron beam

Characteristics of a 9 MeV electron beam were investigated, to evaluate potential benefits for patients with extensive mycosis fungoides lesions that are deeper than commonly treated with 6 MeV total skin electron therapy (TSET or TSE/TSEI/TSEB/TSEBT). A comprehensive commissioning measurement program was completed for TSET delivery using high-dose-rate 6 MeV and 9 MeV electron beams from a Varian TrueBeam linac. Various phantoms and dosimeters were set up 300 cm from isocenter, behind a 6 mm PMMA spoiler screen, and used for optimising beam-pair gantry angles, measuring depth-dose, lateral and horizontal profiles and B-factors, as well as performing end-to-end tests. The key clinical distinctions observed for the 9 MeV TSET beam pair compared to the 6 MeV TSET beam pair were that the 80% dose depth increased to nearly 1 cm and the practical range increased to 3.5 cm, while the maximum dose remained within 0.2 cm of the surface. Vertical and horizontal dose profiles measured with the two energies were almost indistinguishable. The 9 MeV TSET beam has been shown to achieve greater depth penetration compared to the commonly used 6 MeV TSET beam, without detrimentally affecting the dose uniformity achievable in the patient plane. TSET treatments with 9 MeV electrons may be advisable for patients with extensive lesions that are too deep for effective treatment with a 6 MeV beam.

physics.med-ph↗

arXiv2026

Adapting a 3D scanning water phantom for use in brachytherapy dosimetry

In external beam radiotherapy, 3D scanning water phantoms are the gold standard for obtaining relative dosimetry data. These phantoms, consisting of a water tank and mechanical arm, along with accompanying software, are de-signed to acquire dose profiles along and orthogonal to the beam axis. In brachy-therapy, the acquisition of analogous dose profiles is more difficult, and is generally achieved with complex custom-built phantoms or chemical dosimeters such as film or gel. In this study, a low-cost 3D-printed jig was designed and fabricated within a clinical department, to allow precise brachytherapy dose measurements using a PTW BeamScan water phantom. Specifically, this jig al-lowed applicators to be suspended securely and reproducibly within the water phantom. Protocols were developed to relate the scanning system coordinates to the physical source position, and to obtain isodose planes both parallel and radial to the source axis. The developed solution has the potential to be used for physical verification of TG43 dose calculation parameters (e.g. anisotropy functions), the characterization of dose for a single dwell position in a complex applicator containing non-water equivalent materials, or the collection of point dose measure-ments for treatments incorporating multiple dwell positions or catheters.

physics.med-ph↗

arXiv2026

Patient-specific immobilisation for radiotherapy treatment of extensive lower-limb carcinoma

When non-melanoma skin cancers extend over large areas of skin, effective radiotherapy treatments can be delivered using volumetric modulated arc therapy (VMAT) beams with narrow segments that rotate around the affected surfaces. For lower-limb carcinoma treatments, careful immobilisation is needed to achieve the degree of reproducible and stable positioning required to ensure the narrow field segments treat the targeted tissue and avoid underlying anatomy. To meet this need, a 3D printed patient-specific foot support was created in the form of a solid box containing a deep ``footprint'', shaped to match the outline of the patient's relaxed foot when lying supine, supported by a vacuum bag. For our first patient treated with a 3D printed foot support, image guidance data and clinical notes were evaluated against corresponding information from all recent lower-leg VMAT treatments. The patient feedback was recorded as ``good'', with no complaints of discomfort or poor fit, and the proportion of treatment fractions requiring shifts greater than 5 mm after setup imaging (20\%) compared favourably to the proportions for patients without a patient-specific foot support (23\%-84\%). The patient-specific foot support was particularly useful for minimising longitudinal shifts and leg rotations. Evidently, 3D-printed patient-specific immobilisation devices have the potential to enhance positioning stability, and therefore potentially improve accuracy and effectiveness of VMAT treatments, for patients with extensive lower-limb carcinomas.

physics.med-ph↗

arXiv2021

A Publicly Available Dataset of Out-of-Field Dose Profiles of a 6 MV Linear Accelerator

An increase in radiotherapy-induced secondary malignancies has led to recent developments in analytical modelling of out-of-field dose. These models must be validated against measurements, but currently available datasets are outdated or limited in scope. This study aimed to address these shortcomings by producing a large dataset of out-of-field dose profiles measured with modern equipment. A novel method was developed with the intention of allowing physicists in all clinics to perform these measurements themselves using commonly available dosimetry equipment. A standard 3D scanning water tank was used to collect 36 extended profiles. Each profile was measured in two sections, with the inner section measured with the beam directly incident on the tank, and the outer section with the beam incident on a water-equivalent phantom abutted next to the tank. The two sections were then stitched using a novel feature-matching approach. The profiles were compared against linac commissioning data and manually inspected for discontinuities in the overlap region. The dataset is presented as a publicly accessible comma separated variable file containing off-axis ratios at a range of off-axis distances. This dataset may be applied to the development and validation of analytical models of out-of-field dose. Additionally, it may be used to inform dose estimates to radiosensitive implants and anatomy. Physicists are encouraged to perform these out-of-field measurements in their own clinics and share their results with the community.

physics.med-ph↗

arXiv2021

Measuring foetal dose from tomotherapy treatments

Introduction: Treating pregnant women in the radiotherapy clinic is a rare occurrence. When it does occur, it is vital that the dose received by the developing embryo or foetus is understood as fully as possible. This study presents the first investigation of foetal doses delivered during helical tomotherapy treatments. Materials & Methods: Six treatment plans were delivered to an anthropomorphic phantom using a tomotherapy machine. These included treatments of the brain, unilateral and bilateral head-and-neck, chest wall, and upper lung. Measurements of foetal dose were made with an ionisation chamber positioned at various locations longitudinally within the phantom to simulate a variety of patient anatomies. Results: All measurements were below the established limit of 100 mGy for a high risk of damage during the first trimester. The largest dose encountered was 75 mGy (0.125% of prescription dose). The majority of treatments with measurement positions less than 30 cm fell into the range of uncertain risk (50 - 100 mGy). All treatments with measurement positions beyond 30 cm fell into the low risk category (< 50 mGy). Conclusions: For the cases in this study, tomotherapy resulted in foetal doses that are at least on par with, if not significantly lower than, similar 3D conformal or intensity-modulated treatments delivered with other devices. Recommendations were also provided for estimating foetal doses from tomotherapy plans.

physics.med-ph↗