A new radiotherapy surface dose detector: The MOSFET

Butson, Martin J; Rozenfeld, Anatoly; Mathur, J. N.; Carolan, Martin G; Wong, Tony; Metcalfe, Peter E

doi:10.1118/1.597702

Cited by 113 publications

(71 citation statements)

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“…In build up region 0-4 mm response of MOSkin less then FOD and both of them under-responded when compared to the ionization chamber, which is related to the large size of FOD used and Farmer IC and error associated with this. Previous comparison of Monte Carlo simulations, ATTIX IC and bare MOSFET response demonstrated perfect agreement 5,10 in a build up region that is supporting assumption above. Table 1 shows the PDD values obtained when the MOSkin, fiber optic dosimeter, and Attix chamber were placed on the surface of the phantom and irradiated at field sizes of 5 5, 10 10, 20 20, and 40 40 cm 2 .…”

Section: Resultssupporting

confidence: 52%

“…MOSFET dosimeters have the added benefit of a micronscale sensitive volume, allowing them to measure the absorbed dose in steep dose gradient conditions. 5,6) Larger detectors can only measure a volume average dose, which lacks precision and results in a large uncertainty in the measurement like ionization chamber and TLD detectors in a build up region of MV X-ray from LINAC . In an X-ray field delivered by a medical LINAC, the thin sensitive volume of the MOSFET proves invaluable in the build-up region of the depth dose curve, where the dose gradient is very steep.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of the New MOSkin Detector and Fiber Optic Dosimetry System for Radiotherapy

Kwan

Lee

Yoo

et al. 2008

Journal of Nuclear Science and Technology

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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 readings taken with an Attix chamber. At depths greater than 15 mm, the MOSkin readings deviated from the ion chamber readings by up to 4%, while the fiber optic dosimeter always remained within 3% of the ionization chamber reading. In the build-up region, the MOSkin proved quite capable of measuring the dose at build up when compared to the Attix chamber results, while the fiber optic dosimeter was not able to measure the dose in this region with a high level of precision due to the thick sensitive volume of the scintillating crystal.

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Section: Resultssupporting

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Comparison of the New MOSkin Detector and Fiber Optic Dosimetry System for Radiotherapy

Kwan

Lee

Yoo

et al. 2008

Journal of Nuclear Science and Technology

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“…Until recently, MOSFETs were mainly used in radiotherapy, 10 , 11 , 12 , 13 but are now being more commonly used in different fields of diagnostic radiology 14 , 15 , 16 , 17 , 18 . A drawback with MOSFET dosimeters is that they have limited sensitivity when compared with TLD dosimeters.…”

Section: Introductionmentioning

confidence: 99%

Characterization of MOSFET dosimeters for low‐dose measurements in maxillofacial anthropomorphic phantoms

Koivisto

Wolff

Kiljunen

et al. 2015

J Applied Clin Med Phys

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The aims of this study were to characterize reinforced metal‐oxide‐semiconductor field‐effect transistor (MOSFET) dosimeters to assess the measurement uncertainty, single exposure low‐dose limit with acceptable accuracy, and the number of exposures required to attain the corresponding limit of the thermoluminescent dosimeters (TLD). The second aim was to characterize MOSFET dosimeter sensitivities for two dental photon energy ranges, dose dependency, dose rate dependency, and accumulated dose dependency. A further aim was to compare the performance of MOSFETs with those of TLDs in an anthropomorphic phantom head using a dentomaxillofacial CBCT device. The uncertainty was assessed by exposing 20 MOSFETs and a Barracuda MPD reference dosimeter. The MOSFET dosimeter sensitivities were evaluated for two photon energy ranges (50–90 kVp) using a constant dose and polymethylmethacrylate backscatter material. MOSFET and TLD comparative point‐dose measurements were performed on an anthropomorphic phantom that was exposed with a clinical CBCT protocol. The MOSFET single exposure low dose limit (25% uncertainty, normalk=2) was 1.69 mGy. An averaging of eight MOSFET exposures was required to attain the corresponding TLD (0.3 mGy) low‐dose limit. The sensitivity was 3.09±0.13 mV/mGy independently of the photon energy used. The MOSFET dosimeters did not present dose or dose rate sensitivity but, however, presented a 1% decrease of sensitivity per 1000 mV for accumulated threshold voltages between 8300 mV and 17500 mV. The point doses in an anthropomorphic phantom ranged for MOSFETs between 0.24 mGy and 2.29 mGy and for TLDs between 0.25 and 2.09 mGy, respectively. The mean difference was −8%. The MOSFET dosimeters presented statistically insignificant energy dependency. By averaging multiple exposures, the MOSFET dosimeters can achieve a TLD‐comparable low‐dose limit and constitute a feasible method for diagnostic dosimetry using anthropomorphic phantoms. However, for single in vivo measurements (<1.7 mGy) the sensitivity is too low.PACS number: 87.50.wj

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“…Theoretically, the dose deposited at the surface (surface dose) and in the buildup region (entrance dose) of photon fields has two main contributors [66]. One is in-phantom scatter, due to photon interactions with the phantom material and subsequent generation of secondary electrons, which deposit energy along their path.…”

Section: Mosfet Dosimetrymentioning

confidence: 99%

Advanced Semiconductor Dosimetry in Radiation Therapy

Rosenfeld

2011

AIP Conference Proceedings

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Modern radiation therapy is very conformal, resulting in a complexity of delivery that leads to many small radiation fields with steep dose gradients, increasing error probability. Quality assurance in delivery of such radiation fields is paramount and requires real time and high spatial resolution dosimetry. Semiconductor radiation detectors due to their small size, ability to operate in passive and active modes and easy real time multichannel readout satisfy many aspects of in vivo and in a phantom quality assurance in modern radiation therapy. Update on the recent developments and improvements in semiconductor radiation detectors and their application for quality assurance in radiation therapy, based mostly on the developments at the Centre for Medical Radiation Physics (CMRP), University of Wollongong, is presented. Abstract. Modern radiation therapy is very conformal, resulting in a complexity of delivery that leads to many small radiation fields with steep dose gradients, increasing error probability. Quality assurance in delivery of such radiation fields is paramount and requires real time and high spatial resolution dosimetry. Semiconductor radiation detectors due to their small size, ability to operate in passive and active modes and easy real time multichannel readout satisfy many aspects of in vivo and in a phantom quality assurance in modern radiation therapy. Update on the recent developments and improvements in semiconductor radiation detectors and their application for quality assurance in radiation therapy, based mostly on the developments at the Centre for Medical Radiation Physics (CMRP), University of Wollongong, is presented.

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A new radiotherapy surface dose detector: The MOSFET

Cited by 113 publications

References 0 publications

Comparison of the New MOSkin Detector and Fiber Optic Dosimetry System for Radiotherapy

Comparison of the New MOSkin Detector and Fiber Optic Dosimetry System for Radiotherapy

Characterization of MOSFET dosimeters for low‐dose measurements in maxillofacial anthropomorphic phantoms

Advanced Semiconductor Dosimetry in Radiation Therapy

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