Impact of abdominal compression on heart and stomach motion for stereotactic arrhythmia radioablation.

Purpose: To evaluate the effectiveness of abdominal compression (AC) as a respiratory motion management method for the heart and stomach during stereotactic arrhythmia radioablation (STAR).

Methods: 4D computed tomography (4DCT) scans of patients imaged with AC or without AC (free-breathing: FB) were obtained from ventricular-tachycardia (VT) (n = 3), lung cancer (n = 18), and liver cancer (n = 18) patients. Patients treated for VT were imaged both FB and with AC.

Stereotactic Optimized Automated Radiotherapy (SOAR): a novel automated planning solution for multi-metastatic SRS compared to HyperArc™.

Automated Stereotactic Radiosurgery (SRS) planning solutions improve clinical efficiency and reduce treatment plan variability. Available commercial solutions employ a template-based strategy that may not be optimal for all SRS patients. This study compares a novel beam angle optimized Volumetric Modulated Arc Therapy (VMAT) planning solution for multi-metastatic SRS to the commercial solution HyperArc.

Can machine learning models improve early detection of brain metastases using diffusion weighted imaging-based radiomics?

Background: Metastatic complications are a major cause of cancer-related morbidity, with up to 40% of cancer patients experiencing at least one brain metastasis. Earlier detection may significantly improve patient outcomes and overall survival. We investigated machine learning (ML) models for early detection of brain metastases based on diffusion weighted imaging (DWI) radiomics.

High replication stress and limited Rad51-mediated DNA repair capacity, but not oxidative stress, underlie oligodendrocyte precursor cell radiosensitivity.

Cranial irradiation is part of the standard of care for treating pediatric brain tumors. However, ionizing radiation can trigger serious long-term neurologic sequelae, including oligodendrocyte and brain white matter loss enabling neurocognitive decline in children surviving brain cancer. Oxidative stress-mediated oligodendrocyte precursor cell (OPC) radiosensitivity has been proposed as a possible explanation for this.

Fast stereotactic radiosurgery planning using patient-specific beam angle optimization and automation.

Background And Purpose: Linac-based stereotactic radiosurgery (SRS) planning for multi-metastatic cases is a complex and intensive process. A manual planning strategy starts with a template-based set of beam angles and applies modifications though a trial and error process. Beam angle optimization uses patient specific geometric heuristics to determine beam angles that provide optimal target coverage and avoid treating through Organs-at-Risk (OARs).

Investigating diffusion patterns of brain metastases pre- and post-stereotactic radiosurgery: a feasibility study.

Metastatic complications are responsible for 90% of cancer-associated mortality. Magnetic resonance imaging (MRI) can be used to observe the brain's microstructure and potentially correlate changes with metastasis occurrence. Diffusion weighted imaging (DWI) is an MRI technique that utilizes the kinetics of water molecules within the body.

Auto-delineation framework for the focal liver reaction observed in post Stereotactic Body Radiation Therapy (SBRT) Primovist MRI scans.

Development of a novel auto-delineation methodology for observed hypointensity from focal liver reaction in hepatobiliary-specific contrast (Primovist) enhanced MRI acquired post Stereotactic Body Radiation Therapy (SBRT). Additionally, the methodology for the quantification of the threshold dose associated with the observed focal liver reaction was also established. An auto-delineation algorithm was created based on the correlation between intensity and radiation dose information.

Direct visualization and correlation of liver stereotactic body radiation therapy treatment delivery accuracy with interfractional motion.

This study used the visualization of hypo-intense regions on liver-specific MRI to directly quantify stereotactic body radiation therapy (SBRT) spatial delivery accuracy. Additionally, the interfractional motion of the liver region was determined and compared with the MRI-based evaluation of liver SBRT spatial treatment delivery accuracy. Primovist -enhanced MRI scans were acquired from 17 patients, 8-12 weeks following the completion of liver SBRT treatment.

Review of Stereotactic Arrhythmia Radioablation Therapy for Cardiac Tachydysrhythmias.

Cardiac tachyarrhythmias are a major cause of morbidity and mortality. Treatments for these tachyarrhythmias include antiarrhythmic drugs, catheter ablation, surgical ablation, cardiac implantable electronic devices, and cardiac transplantation. Each of these treatment approaches is effective in some patients but there is considerable room for improvement, particularly with respect to the most common of the tachydysrhythmias, atrial fibrillation, and the most dangerous of the tachydysrhythmias, ventricular tachycardia (VT) or ventricular fibrillation.

A high-throughput alpha particle irradiation system for monitoring DNA damage repair, genome instability and screening in human cell and yeast model systems.

Ionizing radiation (IR) is environmentally prevalent and, depending on dose and linear energy transfer (LET), can elicit serious health effects by damaging DNA. Relative to low LET photon radiation (X-rays, gamma rays), higher LET particle radiation produces more disease causing, complex DNA damage that is substantially more challenging to resolve quickly or accurately. Despite the majority of human lifetime IR exposure involving long-term, repetitive, low doses of high LET alpha particles (e.

Structure guided deformable image registration for treatment planning CT and post stereotactic body radiation therapy (SBRT) Primovist (Gd-EOB-DTPA) enhanced MRI.

The purpose of this study was to assess the performance of structure-guided deformable image registration (SG-DIR) relative to rigid registration and DIR using TG-132 recommendations. This assessment was performed for image registration of treatment planning computed tomography (CT) and magnetic resonance imaging (MRI) scans with Primovist contrast agent acquired post stereotactic body radiation therapy (SBRT). SBRT treatment planning CT scans and posttreatment Primovist MRI scans were obtained for 14 patients.

Dosimetric and radiobiological impact of abdominal compression on adjacent gastro-intestinal critical structures for patients treated with upper and mid-abdominal stereotactic body radiotherapy.

Objectives: We evaluated the dosimetric and radiobiological impact of abdominal compression (AC) on nearby gastrointestinal critical structures (GI-CS) and reported toxicities of patients treated with non-hepatic abdominal stereotactic body radiotherapy (SBRT).

Methods: Two sets of CT scans, planning scans with AC and pre-treatment diagnostic scans without AC (non-AC) were compared for patients treated with a prescription dose to planning target volume (PTV) ≥25 Gy/5-fractions at a single institution. Target volumes were delineated on both sets of scans and PTV was expanded isotropically by 2 cm (PTV+2) and 4 cm (PTV+4).

Development and clinical implementation of eclipse scripting-based automated patient-specific collision avoidance software.

Purpose: Increased use of Linac-based stereotactic radiosurgery (SRS), which requires highly noncoplanar gantry trajectories, necessitates the development of efficient and accurate methods of collision detection during the treatment planning process. This work outlines the development and clinical implementation of a patient-specific computed tomography (CT) contour-based solution that utilizes Eclipse Scripting to ensure maximum integration with clinical workflow.

Methods: The collision detection application uses triangle mesh structures of the gantry and couch, in addition to the body contour of the patient taken during CT simulation, to virtually simulate patient treatments.

Technical Note: A novel quality assurance test to identify gantry angle inaccuracies in respiratory-gated VMAT treatments.

Purpose: During respiratory-gated volumetric-modulated arc therapy (VMAT), the radiation beam is turned off each time the target exits the gating window. At the same time, the gantry slows, stops, and rewinds before the beam is turned back on. A quality assurance (QA) test was developed to detect inaccuracies in the gantry angle position between beam-off and beam-on events during respiratory-gated VMAT.

Unexpected Symptomatic Pneumonitis Following Breast Tangent Radiation: A Case Report.

Symptomatic radiation pneumonitis (RP) following radiation therapy (RT) to the breast alone is very uncommon. We report a case of an 80-year-old female who presented with fatigue, exertional dyspnea, fever, and cough 11.5 weeks following adjuvant breast RT with tangent fields alone.

Use of novel fibre-coupled radioluminescence and RADPOS dosimetry systems for total scatter factor measurements in small fields.

A dosimetry system based on Al2O3:C radioluminescence (RL), and RADPOS, a novel 4D dosimetry system using microMOSFETs, were used to measure total scatter factors, (S(c,p))(f(clin))(det), for the CyberKnife robotic radiosugery system. New Monte Carlo calculated correction factors are presented and applied for the RL detector response for the 5, 7.5 and 10 mm collimators in order to correct for the detector geometry and increased photoelectric cross section of Al2O3:C relative to water.

Sci-Fri PM: Delivery - 07: Cyberknife relative output factor measurements using fiber-coupled luminescence, MOSFETS and RADPOS dosimetry system.

Novel dosimetry systems based on Al O :C radioluminescence (RL) and a 4D dosimetry system (RADPOS) from Best Medical Canada were used to measure the relative output factor (ROF) on Cyberknife. Measurements were performed in a solid water phantom at the depth of 1.5 cm and SSD = 78.

Sci-Thur AM: Planning - 10: Improved dosimetric accuracy for patient specific quality assurance using a dual-detector measurement method for cyberknife output factors.

The measurement of output factors for small fields is challenging and can lead to large dose errors in patient treatments if corrections for detector size and scatter from high-Z material are not applied. Due to its high spatial resolution and near tissue equivalence, GAFCHROMIC® film potentially provides a correction free measure of output factors but it can be challenging to obtain high quality dosimetric results using this film. We propose minimizing errors in the clinical determination of small field output factors by employing diode measurements with Monte-Carlo generated corrections for small fields ≤10 mm diameter and using small volume ion chambers for apertures >10 mm diameter with independent validation using radiochromic film.

Position-probability-sampled Monte Carlo calculation of VMAT, 3DCRT, step-shoot IMRT, and helical tomotherapy dose distributions using BEAMnrc/DOSXYZnrc.

Purpose: The commercial release of volumetric modulated arc therapy techniques using a conventional linear accelerator and the growing number of helical tomotherapy users have triggered renewed interest in dose verification methods, and also in tools for exploring the impact of machine tolerance and patient motion on dose distributions without the need to approximate time-varying parameters such as gantry position, MLC leaf motion, or patient motion. To this end we have developed a Monte Carlo-based calculation method capable of simulating a wide variety of treatment techniques without the need to resort to discretization approximations.

Methods: The ability to perform complete position-probability-sampled Monte Carlo dose calculations was implemented in the BEAMnrc/DOSXZYnrc user codes of EGSnrc.

IMRT for the breast: a comparison of tangential planning techniques.

Three intensity-modulated tangential beam radiotherapy plan types for breast cancer treatment were evaluated based on PTV homogeneity index (HI) and equivalent uniform dose (EUD), heart V30 and EUD, whole lung V20 and EUD, and typical planning time compared to conventional 2D plans. 20 early-stage breast cancer patients were CT-scanned in the supine position, and tangential field extent, gantry and collimator angles were chosen. Four treatment plans were created for each patient: conventional, dynamically wedged plan based on the dose distribution on the central axial slice; forward planned IMRT; surface compensated plan created using an Eclipse tool and hybrid IMRT plan combining open and inverse-optimized fields.

A cost-outcome analysis of Image-Guided Patient Repositioning in the radiation treatment of cancer of the prostate.

Background And Purpose: With Image-Guided Radiation Therapy (IGRT) rapidly gaining acceptance in the clinic it is timely to commence an assessment of its potential outcome benefit versus costs.

Materials And Methods: Using Activity-Based Costing we have calculated the incremental cost of adding Image-Guided Patient Repositioning (IGPR), a significant component of IGRT, to both Intensity-Modulated Radiation Therapy (IMRT) and Three-Dimensional Conformal Radiation Therapy (3DCRT) for prostate cancer. The dosimetric outcome benefit resulting from the implementation of IGPR is estimated from a publication describing the improvement in set-up accuracy using each of four correction protocols.

Phantom evaluation of a commercially available three modality image guided radiation therapy system.

The authors describe a detailed evaluation of the capabilities of imaging and image registration systems available with Varian linear accelerators for image guided radiation therapy (IGRT). Specifically, they present modulation transfer function curves for megavoltage planar, kilovoltage (kV) planar, and cone beam computed tomography imaging systems and compare these with conventional computed tomography. While kV planar imaging displayed the highest spatial resolution, all IGRT imaging techniques were assessed as adequate for their intended purpose.

Evaluation of linear accelerator performance standards using an outcome oriented approach.

Radiation therapy, along with other branches of medicine, is moving towards a firmer basis in evidence to optimally utilize resources. As new treatment technology and strategies place greater demands on quality assurance resources, the need to objectively evaluate equipment and process performance standards from the perspective of predicted clinical impact becomes more urgent. This study evaluates the appropriateness of recommended quality control tolerance and action levels for linear accelerators based on the calculated dosimetric impact of suboptimal equipment performance.

The cost of radiation therapy.

Background And Purpose: The rising cost of health care is of universal concern. If the cost effectiveness of conventional and novel radiotherapeutic strategies is to be established we need to have confidence in our estimates of both cost and effectiveness. The purpose of this study is to explore the degree of consistency of recently published cost estimates for radiation therapy.

Towards an objective evaluation of tolerances for beam modeling in a treatment planning system.

The performance of a convolution/superposition based treatment planning system depends on the ability of the dose calculation algorithm to accurately account for physical interactions taking place in the tissue, key components of the linac head and on the accuracy of the photon beam model. Generally the user has little or no control over the performance of the dose calculation algorithm but is responsible for the accuracy of the beam model within the constraints imposed by the system. This study explores the dosimetric impact of limitations in photon beam modeling accuracy on complex 3D clinical treatment plans.