Bridging the proton gap: A proton therapy consultation service for Canadian radiation oncologists.

Purpose: Canada is the only G7 country without a clinical proton beam therapy (PBT) facility. Patients can access publicly funded PBT through provincial out-of-country approval programs. We created a consultation service to inform health care providers regarding the potential dosimetric benefits of PBT.

Operational Improvement of a Proton Therapy System From Reduced Energy Layer Switching Time.

Purpose: This study reports the potential operational improvement provided by reduced energy layer switching time and total beam delivery time of a 3-room IBA ProteusPLUS system.

Materials And Methods: Eight treatment fields, including various disease sites and a reference cube, were analyzed for energy layer switching time and total delivery time before and after an energy layer switching time upgrade. The upgraded beam delivery time estimated the total treatment capacity for a 12-h treatment day using a 3-room system with a single common cyclotron.

Secondary cancer risk in six anatomical sites when using PAT, IMPT, and VMAT/IMRT radiotherapy.

Background And Purpose: Compared to intensity modulated proton therapy (IMPT), proton arc therapy (PAT) is expected to improve dose conformality, delivery efficiency, and provide a more favorable LET distribution. Alternatively, the low-dose bath is potentially spread over larger volumes, which could impact the likelihood of developing a radiation-induced, secondary cancer (SC). The goal of this study was to evaluate this risk in several anatomical sites using newly developed commercial tools.

AAPM WGPE report 394: Simulated error training for the physics plan and chart review.

Background: Simulated error training is a method to practice error detection in situations where the occurrence of error is low. Such is the case for the physics plan and chart review where a physicist may check several plans before encountering a significant problem. By simulating potentially hazardous errors, physicists can become familiar with how they manifest and learn from mistakes made during a simulated plan review.

Patient posture correction and alignment using mixed reality visualization and the HoloLens 2.

Purpose: The purpose of this study was to develop and preliminarily test a radiotherapy system for patient posture correction and alignment using mixed reality (MixR) visualization. The write-up of this work also provides an opportunity to introduce the concepts and technology of MixR for a medical physics audience who may be unfamiliar with the topic.

Methods: A MixR application was developed for on optical-see-through head-mounted display (HoloLens 2) allowing a user to simultaneously and directly view a patient and a reference hologram derived from their simulation CT scan.

Effective Organs-at-Risk Dose Sparing in Volumetric Modulated Arc Therapy Using a Half-Beam Technique in Whole Pelvic Irradiation.

Background: Although there are some controversies regarding whole pelvic radiation therapy (WPRT) due to its gastrointestinal and hematologic toxicities, it is considered for patients with gynecological, rectal, and prostate cancer. To effectively spare organs-at-risk (OAR) doses using multi-leaf collimator (MLC)'s optimal segments, potential dosimetric benefits in volumetric modulated arc therapy (VMAT) using a half-beam technique (HF) were investigated for WPRT.

Methods: While the size of a fully opened field (FF) was decided to entirely include a planning target volume in all beam's eye view across arc angles, the HF was designed to use half the FF from the isocenter for dose optimization.

Data for optimizing Gamma Knife radiosurgery using the shot within shot technique.

The tables included in this article will allow the user to implement shot within shot optimization for Gamma Knife radiosurgery planning and delivery. The method is intended to reduce treatment time when treating small to medium sized brain metastasis. The tables were previously developed by extracting profiles from Gamma Plan for three collimator settings and modeling their behavior when combined or prescribed at different isodose lines.

Clinical Evaluation of Shot-Within-Shot Optimization for Gamma Knife Radiosurgery Planning and Delivery.

Objective: Shot-within-shot (SWS) optimization is a new planning technique that relies on various combinations of shot weighting and prescription isodose line (IDL) to reduce beam-on time. The method differs from other planning techniques that incorporate mixed collimation, multiple stereotactic coordinates, and traditionally low prescription IDLs (<60%). In this work, we evaluate the percentage of brain metastasis for which the method can be applied, the magnitude of the resultant time savings, and the possible tradeoffs in plan quality.

Quantitative radiomics: Validating image textural features for oncological PET in lung cancer.

Background And Purpose: Radiomics textural features derived from PET imaging are of broad and current interest due to recent evidence of their prognostic value during cancer management. An inherent assumption is the link between these imaging features and the underlying tumoral phenotypic spatial heterogeneity. The purpose of this work was to validate this assumption for tumors within the lung through a comparison of image based textural features and the ground truth activity distribution from which the images were created.

Optimization of the prescription isodose line for Gamma Knife radiosurgery using the shot within shot technique.

Background: This work explores how the choice of prescription isodose line (IDL) affects the dose gradient, target coverage, and treatment time for Gamma Knife radiosurgery when a smaller shot is encompassed within a larger shot at the same stereotactic coordinates (shot within shot technique).

Methods: Beam profiles for the 4, 8, and 16 mm collimator settings were extracted from the treatment planning system and characterized using Gaussian fits. The characterized data were used to create over 10,000 shot within shot configurations by systematically changing collimator weighting and choice of prescription IDL.

Quantitative imaging: Correlating image features with the segmentation accuracy of PET based tumor contours in the lung.

The purpose of this study was to investigate the correlation between image features extracted from PET images and the accuracy of manually drawn lesion contours in the lung. Such correlations are interesting in that they could potentially be used in predictive models to help guide physician contouring. In this work, 26 synthetic PET datasets were created using an anthropomorphic phantom and Monte Carlo simulation.

Evaluation of the tool "Reg Refine" for user-guided deformable image registration.

"Reg Refine" is a tool available in the MIM Maestro v6.4.5 platform (www.

Benchmarking of five commercial deformable image registration algorithms for head and neck patients.

Benchmarking is a process in which standardized tests are used to assess system performance. The data produced in the process are important for comparative purposes, particularly when considering the implementation and quality assurance of DIR algorithms. In this work, five commercial DIR algorithms (MIM, Velocity, RayStation, Pinnacle, and Eclipse) were benchmarked using a set of 10 virtual phantoms.

An image guided small animal stereotactic radiotherapy system.

Small animal radiotherapy studies should be performed preferably on irradiators capable of focal tumor irradiation and healthy tissue sparing. In this study, an image guided small animal arc radiation treatment system (iSMAART) was developed which can achieve highly precise radiation targeting through the utilization of onboard cone beam computed tomography (CBCT) guidance. The iSMAART employs a unique imaging and radiation geometry where animals are positioned upright.

Skin dose mapping for fluoroscopically guided interventions.

Purpose: To introduce a new skin dose mapping software system for interventional fluoroscopy dose assessment and to analyze the benefits and limitations of patient-phantom matching.

Methods: In this study, a new software system was developed for visualizing patient skin dose during interventional fluoroscopy procedures. The system works by translating the reference point air kerma to the location of the patient's skin, which is represented by a computational model.

The impact of anthropometric patient-phantom matching on organ dose: a hybrid phantom study for fluoroscopy guided interventions.

Purpose: To investigate the benefits and limitations of patient-phantom matching for determining organ dose during fluoroscopy guided interventions.

Methods: In this study, 27 CT datasets representing patients of different sizes and genders were contoured and converted into patient-specific computational models. Each model was matched, based on height and weight, to computational phantoms selected from the UF hybrid patient-dependent series.