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Real-time In Vivo Dose Verification Using Metal-Oxide Semiconductor Field Effect Transistor (MOSFET) in HDR Brachytherapy
Poster Title: Real-time In Vivo Dose Verification Using Metal-Oxide Semiconductor Field Effect Transistor (MOSFET) in HDR Brachytherapy
Submitted on 23 Mar 2021
Author(s): Rahman, S.H.A 1 , Md. Radzi, Y. 1, Aziz, M.Z.A 2, Azahari, A.N.2
Affiliations: 1School of Physics, Universiti Sains Malaysia, Penang, Malaysia. 2Advanced Medical and Dental Institute (AMDI), Universiti Sains Malaysia, Penang, Malaysia
This poster was presented at 20th Asia-Oceania Congress on Medical Physics (AOCMP)
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Poster Information
Abstract: Introduction: High dose rate (HDR) brachytherapy requires a highly conformal dose to the tumour volume. Hence, in vivo dosimetric for verification during treatment is deem very important and crucial to provide a accurate, highly reliable and precise dose delivery1-4.
Purpose: In this work, we introduced the used of real-time in vivo dosimetry using MOSFET as a reliable quality assurance tool for HDR brachytherapy instead of widely used thermoluminescence dosimeters (TLDs)5-7.
Methods: Calibration of MOSFETs detector was done following the vendor’s specification under HDR Ir-192 brachytherapy source available at our centre. The distance of the source-to-detector (SDD) was measured at 3cm. The detectors and source were positioned in a “sandwich set-up”8. The positional accuracy of the source was verified using Gafchromic EBT3 film. A plan was optimised to deliver 100 cGy at 3cm depth using Oncentra Treatment Planning System (TPS). The detector’s reproducibility, linearity, distance dependency and in-phantom verification were tested for its suitability as an in vivo detector.
Results: Five individual detectors gave maximum sensitivity deviation of 2.66%. Measured values for the reference dose data showed a good agreement with the calculated data, with maximum deviation of –2.86%. The calibration factors were ranged from 1.40 to 1.44 mV/cGy. The MOSFET detector has good reproducibility (<3%) and excellent dose linearity (R2=1). While distance dependency response showed a linear fit with R2 value of 0.9844 (2cm to 5.5cm). In-phantom dose measurements using MOSFET detectors showed that maximum deviation was -4.35%. The percentage deviations between the measured doses and the TPS doses were below 5% for all measurements.
Conclusion: MOSFET has demonstrated as a suitable and good detector of choice for real-time in-vivo dosimetry in HDR brachytherapy. Additionally, MOSFET can be used as one of the reliable QA tools for HDR brachytherapy due to its special characteristic of being small in size.
Summary: This poster explains about the characterization of MOSFET detector in real-time brachytherapy. This poster has been presented in previous AOCMP which has been held virtually on 3-5 Dec 2020 in Phuket, Thailand.References: 1. R. Phurailatpam, R. Upreti, S. Nojin Paul, S. V. Jamema, and D. D. Deshpande, “Characterization of commercial MOSFET detectors and their feasibility for in-vivo HDR brachytherapy,” Phys. Medica, vol. 32, no. 1, pp. 208–212, 2016.
2. C. Melchert, T. Soror, and G. Kovács, “Quality assurance during interstitial brachytherapy: in vivo dosimetry using MOSFET dosimeters,” J. Contemp. Brachytherapy, vol. 10, no. 3, pp. 232–237, 2018.
3. J. Mason, A. Mamo, B. Al-Qaisieh, A. M. Henry, and P. Bownes, “Real-time in vivo dosimetry in high dose rate prostate brachytherapy,” Radiother. Oncol., vol. 120, no. 2, pp. 333–338, 2016.
4. Z. Y. Qi et al., “Verification of the plan dosimetry for high dose rate brachytherapy using metal-oxide-semiconductor field effect transistor detectors,” Med. Phys., vol. 34, no. 6, pp. 2007–2013, 2007.
5. Das, R., Toye, W., Kron, T. et al. Thermoluminescence dosimetry for in-vivo verification of high dose rate brachytherapy for prostate cancer. Austral
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