Engineering Commons^™

Characterization Of An Innovative P-Type Epitaxial Diode For Dosimetry In Modern External Beam Radiotherapy, A Aldosari, A Espinoza, D Robinson, I Fuduli, C Porumb, S Alshaikh, M Carolan, M Lerch, V Perevertaylo, Anatoly Rosenfeld, M Petasecca

Anthony A Espinoza Mr

Due to the ever-increasing complexity of treatment modalities in radiation therapy, there has been a greater need for detectors to perform quality assurance to ensure patients are treated correctly and safely. Modern radiation therapy techniques involve small field sizes, high dose gradients, and varying intensity of energy and rate. The ideal dosimeter for this treatment should display high spatial resolution, high linearity, accuracy, and radiation hardness. Silicon detectors have been widely used for radiotherapy measurements and have many attractive qualities as a dosimeter; weaknesses of silicon detectors are, however, decreases in sensitivity with accumulated dose. The Centre for Medical Radiation …

A Silicon Strip Detector Dose Magnifying Glass For Imrt Dosimetry, J.H.D Wong, Martin Carolan, Michael Lerch, Marco Petasecca, Sutinder Khanna, V Perevertaylo, Peter Metcalfe, Anatoly Rosenfeld

Michael L.F. Lerch

Purpose: Intensity modulated radiation therapy (IMRT) allows the delivery of escalated radiation dose to tumor while sparing adjacent critical organs. In doing so, IMRT plans tend to incorporate steep dose gradients at interfaces between the target and the organs at risk. Current quality assurance (QA) verification tools such as 2D diode arrays, are limited by their spatial resolution and conventional films are nonreal time. In this article, the authors describe a novel silicon strip detector (CMRP DMG) of high spatial resolution (200 μm) suitable for measuring the high dose gradients in an IMRT delivery. Methods: A full characterization of the …

Comparison Of The New Moskin Detector And Fiber Optic Dosimetry System For Radiotherapy, Ian Kwan, Bong Soo Lee, Wook Jae Yoo, Donghyun Cho, Kyoungwon Jang, Sanghun Shin, Martin Carolan, Michael Lerch, V Perevertaylo, Anatoly Rosenfeld

Michael L.F. Lerch

In radiotherapy, interest in real-time dosimetry stems from the desire to monitor the dose delivered to the target volume and the surrounding normal tissue to enable clinicians to track the progress of the treatment, and prevent surrounding tissue from receiving too much radiation dose. In this study, the dosimetric performance of the new MOSkin dosimeter and a Bicron BCF-20 scintillating fiber was compared to depth dose measurements taken with a Farmer-type ionization chamber. The performance of the MOSkin and BCF-20 detectors in the build-up region of the depth dose curve, where the dose gradient is steep, is also compared to …

Evaluation Of A Thin Microstrip Detector For High Spatial Resolution Dosimetry, J Kalliopuska, Ashley Cullen, Michael Lerch, Marco Petasecca, M Santala, Anatoly Rosenfeld

Michael L.F. Lerch

VTT and Aalto University have supplied thin microstrip detector prototypes to CMRP for evaluation for the high spatial resolution dosimetry. The evaluation for dosimetry in microbeam radiation therapy (MRT) was done in a synchrotron microbeam at ESRF, France. Measurements studied a response of a single strip on the synchrotron microbeam in face-on and edge-on modes using CMRP designed and developed readout electronics for a parallel readout of single strips. Measurements were done in a passive mode without bias voltage and the detector was scanned through an array of intensive planar microbeams with the nominal width of 50 μm. The face-on …

From Hep To Medical Radiation Dosimetry - The Silicon Strip Detector Dose Magnifying Glass, J.H.D Wong, Dean Cutajar, Michael Lerch, Marco Petasecca, T Knittel, Martin Carolan, V Perevertaylo, Peter Metcalfe, Anatoly Rosenfeld

Michael L.F. Lerch

High energy physics (HEP) experiments and research gave rise to the development of high spatial resolution tracking vertex detectors and the accompanying data acquisition systems (DAQ) capable of high temporal resolution measurements. The technology translation from HEP to the day to day medical radiation dosimetry is gradual but certain. This paper discusses the design and development of a high spatial resolution (0.2 mm pitch) silicon strip detector referred to as the Dose Magnifying Glass designed and prototyped by the Centre for Medical Radiation Physics (CMRP), University of Wollongong. The DMG has 128 phosphor implanted n+ strips on a p-type silicon …

Real-Time In Vivo Dosimetry With Mosfet Detectors In Serial Tomotherapy For Head And Neck Cancer Patients, Zhen-Yu Qi, Xiao-Wu Deng, Shao-Min Huang, Almon Shiu, Michael Lerch, Peter Metcalfe, Anatoly Rosenfeld, Tomas Kron

Michael L.F. Lerch

Purpose

A real-time dose verification method using a recently designed metal oxide semiconductor field effect transistor (MOSFET) dosimetry system was evaluated for quality assurance (QA) of intensity-modulated radiation therapy (IMRT).

Methods and Materials

Following the investigation of key parameters that might affect the accuracy of MOSFET measurements (i.e., source surface distance [SSD], field size, beam incident angles and radiation energy spectrum), the feasibility of this detector in IMRT dose verification was demonstrated by comparison with ion chamber measurements taken in an IMRT QA phantom. Real-time in vivo measurements were also performed with the MOSFET system during serial tomotherapy …

Dosimetry Of Intensive Synchrotron Microbeams, Michael Lerch, Marco Petasecca, A Cullen, A Hamad, H Requardt, E Brauer-Krisch, A Bravin, V Perevertaylo, Anatoly Rosenfeld

Michael L.F. Lerch

Intensive synchrotron X-ray microbeams form an integral part of microbeam radiation therapy (MRT). MRT is a novel radiation medicine modality being developed for inoperable and otherwise untreatable brain tumours. The extremely high dose rate (∼20 kGy/s), laterally fractionated radiation field and steep dose gradients utilized in this therapy make real-time dosimetry a significant challenge. In order for this treatment to advance to the clinical trial stage of development real-time dosimetry systems must be developed. This paper demonstrates the capabilities of a new dosimetry system based on an epitaxial silicon detector. The system combines high spatial resolution and real-time readout and …

Verification Of The Plan Dosimetry For High Dose Rate Brachytherapy Using Metal-Oxide-Semiconductor Field Effect Transistor Detectors, Zhen-Yu Qi, Xiao-Wu Deng, Shao-Min Huang, Jie Lu, Michael Lerch, Dean Cutajar, Anatoly Rosenfeld

Michael L.F. Lerch

The feasibility of a recently designed metal–oxide–semiconductor field effect transistor (MOSFET) dosimetry system for dose verification of high dose rate (HDR) brachytherapy treatment planning was investigated. MOSFET detectors were calibrated with a 0.6 cm3 NE-2571 Farmer-type ionization chamber in water. Key characteristics of the MOSFET detectors, such as the energy dependence, that will affect phantom measurements with HDR 192Ir sources were measured. The MOSFET detector was then applied to verify the dosimetric accuracy of HDR brachytherapy treatments in a custom-made water phantom. Three MOSFET detectors were calibrated independently, with the calibration factors ranging from 0.187 to 0.215 cGy∕mV. A distance …

Miniature Semiconductor Detectors For In Vivo Dosimetry, Anatoly Rosenfeld, Dean Cutajar, Michael Lerch, George Takacs, Iwan Cornelius, M Yudelev, M Zaider

Michael L.F. Lerch

Silicon mini-semiconductor detectors are found in wide applications for in vivo personal dosimetry and dosimetry and microdosimetry of different radiation oncology modalities. These applications are based on integral and spectroscopy modes of metal oxide semiconductor field effect transistor and silicon p–n junction detectors. The advantages and limitations of each are discussed.

Skin Dosimetry With New Mosfet Detectors, Ian Kwan, Anatoly Rosenfeld, Zhen Yu Qi, Dean Wilkinson, Michael Lerch, Dean Cutajar, Mark Safavi-Naeini, Martin Butson, J Bucci, Y Chin, V Perevertaylo

Michael L.F. Lerch

The MOSkin, a new MOSFET-based detector designed by the Centre for Radiation Physics, was engineered to provide accurate measurements of skin doses in radiotherapy and personal monitoring. The International Commission on Radiological Protection (ICRP) estimates the radiosensitive basal layer to be at an average depth of 0.070 mm. Current commercially available MOSFETs utilize an epoxy bubble encapsulation, making measurements at equivalent depths of 0.070mm difficult. The MOSkin utilizes a novel packaging design that allows the measurement of doses at this equivalent depth. The MOSkin has shown excellent agreement with the Attix chamber for surface measurements in a 6MV photon beam …

Verification Of The Plan Dosimetry For High Dose Rate Brachytherapy Using Metal-Oxide-Semiconductor Field Effect Transistor Detectors, Zhen-Yu Qi, Xiao-Wu Deng, Shao-Min Huang, Jie Lu, Michael Lerch, Dean Cutajar, Anatoly Rosenfeld

Dean Cutajar

The feasibility of a recently designed metal–oxide–semiconductor field effect transistor (MOSFET) dosimetry system for dose verification of high dose rate (HDR) brachytherapy treatment planning was investigated. MOSFET detectors were calibrated with a 0.6 cm3 NE-2571 Farmer-type ionization chamber in water. Key characteristics of the MOSFET detectors, such as the energy dependence, that will affect phantom measurements with HDR 192Ir sources were measured. The MOSFET detector was then applied to verify the dosimetric accuracy of HDR brachytherapy treatments in a custom-made water phantom. Three MOSFET detectors were calibrated independently, with the calibration factors ranging from 0.187 to 0.215 cGy∕mV. A distance …

From Hep To Medical Radiation Dosimetry - The Silicon Strip Detector Dose Magnifying Glass, J.H.D Wong, Dean Cutajar, Michael Lerch, Marco Petasecca, T Knittel, Martin Carolan, V Perevertaylo, Peter Metcalfe, Anatoly Rosenfeld

Dean Cutajar

High energy physics (HEP) experiments and research gave rise to the development of high spatial resolution tracking vertex detectors and the accompanying data acquisition systems (DAQ) capable of high temporal resolution measurements. The technology translation from HEP to the day to day medical radiation dosimetry is gradual but certain. This paper discusses the design and development of a high spatial resolution (0.2 mm pitch) silicon strip detector referred to as the Dose Magnifying Glass designed and prototyped by the Centre for Medical Radiation Physics (CMRP), University of Wollongong. The DMG has 128 phosphor implanted n+ strips on a p-type silicon …