Validation of a Monte Carlo simulation for Microbeam Radiation Therapy on the Imaging and Medical Beamline at the Australian Synchrotron

Microbeam Radiation Therapy (MRT) is an emerging cancer treatment modality characterised by the use of high-intensity synchrotron-generated x-rays, spatially fractionated by a multi-slit collimator (MSC), to ablate target tumours. The implementation of an accurate treatment planning system, coupled with simulation tools that allow for independent verification of calculated dose distributions are required to ensure optimal treatment outcomes via reliable dose delivery. In this article we present data from the first Geant4 Monte Carlo radiation transport model of the Imaging and Medical Beamline at the Australian Synchrotron. We have developed the model for use as an independent verification tool for experiments in one of three MRT delivery rooms and therefore compare simulation results with equivalent experimental data. The normalised x-ray spectra produced by the Geant4 model and a previously validated analytical model, SPEC, showed very good agreement using wiggler magnetic field strengths of 2 and 3 T. However, the validity of absolute photon flux at the plane of the Phase Space File (PSF) for a fixed number of simulated electrons was unable to be established. This work shows a possible limitation of the G4SynchrotronRadiation process to model synchrotron radiation when using a variable magnetic field. To account for this limitation, experimentally derived normalisation factors for each wiggler field strength determined under reference conditions were implemented. Experimentally measured broadbeam and microbeam dose distributions within a Gammex RMI457 Solid Water® phantom were compared to simulated distributions generated by the Geant4 model. Simulated and measured broadbeam dose distributions agreed within 3% for all investigated configurations and measured depths. Agreement between the simulated and measured microbeam dose distributions agreed within 5% for all investigated configurations and measured depths

Higher Education and behavior analysis in Europe::Creating a unified approach for the training of autism professionals

Training of behaviour analysts for autism services, has improved notably within a European higher education context. However, regional discrepancies associated with economic, health care, social services, and institutional policies magnify the importance of creating appropriate unified training and consumer protection. Although the European Association for Behaviour Analysis (EABA) has endorsed the Behavior Analyst Certification Board’s (BACB) designations, the absence of European and national regulations, recognition, and accreditation remain significant barriers to quality training and implementation. These challenges are  particularly pertinent in light of BACB decision to limit certification to residents in the USA and Canada after 2022. Advances, challenges, and future directions are discussed within the context of higher education in the United Kingdom, the Czech Republic, Greece, Iceland, Italy, Norway, and Sweden. The post-Bologna European agenda for higher education, globalization and opportunities for the training of behaviour analysts within European higher education are outlined

Silicon strip detector for quality assurance in synchrotron microbeam radiation therapy

Abstract of an oral communication that presented at the 53es Journées Scientifiques de la Société Française de Physique Médicale, 4-6 June 2014, Deauville, France

Silicon strip detector for quality assurance in synchrotron microbeam radiation therapy

Abstract of an oral communication that presented at the 53es Journées Scientifiques de la Société Française de Physique Médicale, 4-6 June 2014, Deauville, France

Polo-like kinase 1 inhibitor BI6727 sensitizes 9L gliosarcoma cells to ionizing irradiation

Surgery, chemotherapy and radiotherapy remain as the major treatment strategies for cancers. Some agents such as anti-cancer drugs have capacity to enhance the radiation sensitivity of cancer cells at G2/M phase, leading to an improved radiotherapeutic efficacy. BI6727 is an ATP-competitive pololike kinase 1 (Plk 1)inhibitor and an anti-cancer drug. Using the radio-resistant 9L rat gliosarcoma cells as model, we examined the effect of BI6727 on cell growth and assessed the chemoradiotherapeutic efficiency between 150 kVp conventional irradiation (dose rate of 0.76 Gy min−1 ) and 66 keV synchrotron x-ray broad beam irradiation (dose rate of 46 Gy s−1). Our studies showed that BI6727 significantly caused cell growth arrest at G2/M phase and inhibited 9L cell proliferation with EC50 of 58.1 nM. In combinatory treatment, irradiation of BI6727-treated 9L cells with synchrotron x-rays at a dose rate of 46 Gy s−1 resulted in significant reduction of the cell survival compared to the conventional x-rays at a dose rate of 0.76 Gy min−1. These results indicated that Plk1 inhibitor BI6727 enhanced radio-sensitization of 9L cells in a dose rate dependent manner. For clinical application, irradiation with high dose rate is a promising strategy to improve chemo-radiotherapeutic efficacy for gliosarcoma cancer

Characterisation and evaluation of a PNP strip detector for synchrotron microbeam radiation therapy

The Quality Assurance requirements of detectors for Synchrotron Micro-beam Radiation Therapy are such that there are limited commercial systems available. The high intensity and spatial fractionation of synchrotron microbeams requires detectors be radiation hard and capable of measuring high dose gradients with high spatial resolution sensitivity. Silicon single strip detectors are a promising candidate for such applications. The PNP strip detector is an alternative design of an already proven technology and is assessed on its contextual viability. In this study, the electrical and charge collection efficiency properties of the device are characterised. In addition, a dedicated TCAD model is used to support ion beam induced charge measurements to determine the spatial resolution of the detector. Lastly, the detector was used to measure the full width half maximum and peak to valley dose ratio for microbeams with only a slight over response. With the exception of radiation hardness the PNP detector is a promising candidate for quality assurance in microbeam radiation therapy

New 3D Silicon detectors for dosimetry in Microbeam Radiation Therapy

Microbeam Radiation Therapy (MRT) involves the use of a spatially fractionated beam of synchrotron generated X-rays to treat tumours. MRT treatment is delivered via an array of high dose \u27peaks\u27 separated by low dose \u27valleys\u27. A good Peak to Valley Dose Ratio (PVDR) is an important indicator of successful treatment outcomes. MRT dosimetry requires a radiation hard detector with high spatial resolution, large dynamic range, which is ideally real-time and tissue equivalent. We have developed a Silicon Strip Detector (SSD) and very recently, a new 3D MESA SSD to meet the very stringent requirements of MRT dosimetry. We have compared these detectors through the characterisation of the MRT radiation field at the Australian Synchrotron Imaging and Medical Beamline. The EPI SSD was able to measure the microbeam profiles and PVDRs, however the effective spatial resolution was limited by the detector alignment options available at the time. The geometry of the new 3D MESA SSD is less sensitive to this alignment restriction was able to measure the microbeam profiles within 2 ¿m of that expected. The 3D MESA SSD measured PVDRs were possibly affected by undesired and slow charge collection outside the sensitive volume and additional scattering from the device substrate

Experimental evaluation of the dosimetric impact of intrafraction prostate rotation using film measurement with a 6DoF robotic arm.

PurposeTumor motion during radiotherapy can cause a reduction in target dose coverage and an increase in healthy tissue exposure. Tumor motion is not strictly translational and often exhibits complex six degree-of-freedom (6DoF) translational and rotational motion. Although the dosimetric impact of prostate tumor translational motion is well investigated, the dosimetric impact of 6DoF motion has only been studied with simulations or dose reconstruction. This study aims to experimentally quantify the dose error caused by 6DoF motion. The experiment was designed to test the hypothesis that 6DoF motion would cause larger dose errors than translational motion alone through gamma analyses of two-dimensional film measurements.MethodsFour patient-measured intrafraction prostate motion traces and four VMAT 7.25 Gy/Fx SBRT treatment plans were selected for the experiment. The traces represented typical motion patterns, including small-angle rotations (6°). Gafchromic film was placed inside a custom-designed phantom, held by a high-precision 6DoF robotic arm for dose measurements in the coronal plane during treatment delivery. For each combination of the motion trace and treatment plan, two film measurements were made, one with 6DoF motion and the other with the three-dimensional (3D) translation components of the same trace. A gamma pass rate criteria of 2% relative dose/2 mm distance-to-agreement was used in this study and evaluated for each measurement with respect to the static reference film. Two test thresholds, 90% and 50% of the reference dose, were applied to investigate the difference in dose coverage for the PTV region and surrounding areas, respectively. The hypothesis was tested using a Wilcoxon signed-rank test.ResultsFor each of the 16 plan and motion trace pairs, a reduction in the gamma pass rate was observed for 6DoF motion compared with 3D translational motion. With 90% gamma-test threshold, the reduction was 5.8% ± 7.1% (P ConclusionFor the first time, the dosimetric impact of intrafraction prostate rotation during SBRT treatment was measured experimentally. The experimental results support the hypothesis that 6DoF tumor motion causes higher dose error than translation motion alone

Experimental Evaluation of the Dosimetric Impact of Intrafraction Prostate Rotations Using Film Measurement with a 6 DoF Robotic Arm

Purpose Tumor motion during radiotherapy can cause a reduction in target dose coverage and an increase in healthy tissue exposure. Tumor motion is not strictly translational and often exhibits complex six degree‐of‐freedom (6DoF) translational and rotational motion. Although the dosimetric impact of prostate tumor translational motion is well investigated, the dosimetric impact of 6DoF motion has only been studied with simulations or dose reconstruction. The present study aims to experimentally quantify the dose error caused by 6DoF motion. The experiment was designed to test the hypothesis that 6DoF motion would cause larger dose errors than translational motion alone through gamma analyses of 2D film measurements. Methods Four patient‐measured intrafraction prostate motion traces and four VMAT 7.25Gy/Fx SBRT treatment plans were selected for the experiment. The traces represented typical motion patterns, including small‐angle rotations (\u3c4°), transient movement, persistent excursion and erratic rotations (\u3e6°). Gafchromic film was placed inside a custom‐designed phantom, held by a high precision 6DoF robotic arm for dose measurements in the coronal plane during treatment delivery. For each combination of the motion trace and treatment plan, two film measurements were made, one with 6DoF motion and the other with the 3D translation components of the same trace. A gamma pass rate criteria of 2% relative dose/2 mm distance‐to‐agreement was used in this study and evaluated for each measurement with respect to the static reference film. Two test thresholds, 90% and 50% of the reference dose, were applied to investigate the difference in dose coverage for the PTV region and surrounding areas, respectively. The hypothesis was tested using a Wilcoxon signed‐rank test. Results For each of the sixteen plan and motion trace pairs, a reduction of the gamma pass rate was observed for 6DoF motion compared with 3D translational motion. With 90% gamma‐test threshold, the reduction was 5.8% ± 7.1% (p\u3c0.01). With 50% gamma‐test threshold, the reduction was 4.1% ± 4.8%(p\u3c0.01). Conclusion For the first time, the dosimetric impact of intrafraction prostate rotation during SBRT treatment was measured experimentally. The experimental results support the hypothesis that 6DoF tumor motion causes higher dose error than translation motion alone