X-Tream: a novel dosimetry system for Synchrotron Microbeam Radiation Therapy

Microbeam Radiation Therapy (MRT) is a radiation treatment technique under development for inoperable brain tumors. MRT is based on the use of a synchrotron generated X-ray beam with an extremely high dose rate ( ~ 20 kGy/sec), striated into an array of X-ray micro-blades. In order to advance to clinical trials, a real-time dosimeter with excellent spatial resolution must be developed for absolute dosimetry. The design of a real-time dosimeter for such a radiation scenario represents a significant challenge due to the high photon flux and vertically striated radiation field, leading to very steep lateral dose gradients. This article analyses the striated radiation field in the context of the requirements for temporal dosimetric measurements and presents the architecture of a new dosimetry system based on the use of silicon detectors and fast data acquisition electronic interface. The combined system demonstrates micrometer spatial resolution and microsecond real time readout with accurate sensitivity and linearity over five orders of magnitude of input signal. The system will therefore be suitable patient treatment plan verification and may also be expanded for in-vivo beam monitoring for patient safety during the treatment

Museum of Fine Arts Bulletin

This article describes a study concerning micropump design for medical purposes. In particular the project is focused on treatment of Hydrocephalus. An actuator glued on a membrane, a pumping chamber and a certain number of valves constitute the micropumps. The actuator is a piezoelectric disc, controlled according to data collected by means of a pressure sensor. We have studied two different structures of micropump: the first with membrane valves, and the second with diffuser/nozzle valves, without moving parts. Modelling both micropumps with electrical equivalent networks, we are able to estimate the pump behaviour, in terms of flow rate, with a simulator such as SPICE, and to optimize the micropump design for best performances. © 2005 Taylor & Francis

Current topics in pharmacology

Radioiodine treatment is administered radioactive iodine to treat the thyroid cancer or to ablate a thyroid remnant. However, due to the risk of radiation, there is a possibility that the patient will experience side effects. Skin dose is an important parameter for quantifying patient dose. The aim of this study is to use a MOSFET detector for real time skin dosimetry. At the Centre for Medical Radiation Physics (CMRP), University of Wollongong, a new type of MOSFET detector called MOSkin is being developed to measure the skin dose, with real-time read out. This paper discusses the pre-clinical characterization the MOSkin and phantom study with radioiodine. In this study, the MOSkin is operated in active mode during irradiation, with +5 V gate bias supplied by a Lithium battery. The Electrical characterization, temperature response, dose linearity response, energy response, and sensitivity versus gate bias for MOSkin were investigated. For the detector characterization, the MOSkin had temperature instability Vth of 0.2 mV/°C under used readout current. The MOSkin energy response was like any MOSFET detector, the dose depending on photon energy. However for a photon energy of more than 250 keV the MOSkin had a flat response that allowed calibration of the MOSkin on a 6 MV LINAC. The sensitivity of the MOSkin was 1.72 mV/cGy and 2.54 mV/cGy under gate biases of +5 V and +15 V respectively. Sensitivity was constant and within 1% when MOSkin irradiated up to 10 Gy. A phantom study was performed with radioiodine 1-131 of activity 80 MBq. The absorbed skin doses for anterior neck and posterior neck were 63.95 and 2.92 cGy respectively. In conclusion, the unique design of the MOSkin appears to show great promise as a skin dosimetry device, with the added advantage of being small in size and having real-time dosimetry capabilities for radionuclide treatment in nuclear medicine

The feasibility study and characterziation of a two-dimensional diode array in “magic phantom” for high dose rate brachytherapy quality assurance

High dose rate (HDR) brachytherapy is a radiation treatment technique capable of delivering large dose rates to the tumor. Radiation is delivered using remote afterloaders to drive highly active sources (commonly 192Ir with an air KERMA strength range between 20 000 and 40 000 U, where 1 U = 1 uGy m2/h in air) through applicators directly into the patient\u27s prescribed region of treatment. Due to the obvious ramifications of incorrect treatment while using such an active source, it is essential that there are methods for quality assurance (QA) that can directly and accurately verify the treatment plan and the functionality of the remote afterloader. This paper describes the feasibility study of a QA system for HDR brachytherapy using a phantom based two-dimensional 11 x 11 epitaxial diode array, named magic phantom

Online in vivo dosimetry in high dose rate prostate brchytherapy with MOSkin detectors: In phantom feasibility study

MOSkin detectors were studied to perform real-time in vivo dose measurements in high dose rate prostate brachytherapy. Measurements were performed inside an urethral catheter in a gel phantom simulating a real prostate implant. Measured and expected doses were compared and the discrepancy was found to be within 8.9% and 3.8% for single MOSkin and dual-MOSkin configurations, respectively. Results show that dual-MOSkin detectors can be profitably adopted in prostate brachytherapy treatments to perform real-time in vivo dosimetry inside the urethra

Review of four novel dosimeters developed for use in radiotherapy

Centre for Medical Radiation Physics (CMRP) is a research strength at the University of Wollongong, the main research theme of this centre is to develop prototype novel radiation dosimeters. Multiple detector systems have been developed by Prof Rosenfelds’ group for various radiation detector applications. This paper focuses on four current detector systems being developed and studied at CMRP. Two silicon array detectors include the magic plate and dose magnifying glass (DMG), the primary focus of these two detectors is high spatial and temporal resolution dosimetry in intensity modulated radiation therapy (IMRT) beams. The third detector discussed is the MOSkin which is a high spatial resolution detector based on MOSFET technology, its primary role is in vivo dosimetry. The fourth detector system discussed is BrachyView, this is a high resolution dose viewing system based on Medipix detector technology

Multichannel Data Acquisition System comparison for Quality Assurance in external beam radiation therapy

Megavoltage photon radiation therapies are widely used in modern cancer treatment. The improvement of the treatment has lead to the need of Quality Assurance (QA) devices to detect malfunctioning or human mistakes during the planning phase and treatment verification. Active electronic devices for 2D or 3D QA in external beam radiotherapy are typically based on analogue/digital mixed signal Data Acquisition Systems (DAS) which are required to have high spatial resolution, large dynamic range, high sensitivity, large numbers of channels and fast real-time capabilities. The Centre of Medical Radiation Physics (CMRP) has developed several multichannel DAS architectures based on different analogue front-ends to suit a wide range of radiotherapy applications. For the purpose of this study, two DAS, with different front-ends, have been equipped with 128 channels and tested in a clinical environment. Data show a good agreement within 1% between the two systems and the ionising chamber currently used for daily QA