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. 2021 Feb 25;26(1):93-100.
doi: 10.5603/RPOR.a2021.0016. eCollection 2021.

In-vivo dose measurements with MOSFET dosimeters during MV portal imaging

Sathish Kumar  1 , Rabi Raja Singh  1 , Henry Finlay Godson  1 , Retna Ponmalar  1 , Paul Ravindran  1 , Sunil Dutt Sharma  2 , Subhashini John  1
Affiliations

In-vivo dose measurements with MOSFET dosimeters during MV portal imaging

Sathish Kumar et al. Rep Pract Oncol Radiother. .

Abstract

Background: The purpose of this study was to investigate the feasibility of MOSFET dosimeter in measuring eye dose during 2D MV portal imaging for setup verification in radiotherapy.

Materials and methods: The in-vivo dose measurements were performed by placing the dosimeters over the eyes of 30 brain patients during the acquisition of portal images in linear accelerator by delivering 1 MU with the field sizes of 10 × 10 cm2 and 15 × 15 cm2.

Results: The mean doses received by the left and right eyes of 10 out of 30 patients when both eyes were completely inside the anterior portal field were found to be 2.56 ± 0.2 cGy and 2.75 ± 0.2, respectively. Similarly, for next 10 patients out of the same 30 patients the mean doses to left and right eyes when both eyes were completely out of the anterior portal fields were found to be 0.13 ± 0.02 cGy and 0.17 ± 0.02 cGy, respectively. The mean doses to ipsilateral and contralateral eye for the last 10 patients when one eye was inside the anterior portal field were found to be 3.28 ± 0.2 cGy and 0.36 ± 0.1 cGy, respectively.

Conclusion: The promising results obtained during 2D MV portal imaging using MOSFET have shown that this dosimeter is well suitable for assessing low doses during imaging thereby enabling to optimize the imaging procedure using the dosimetric data obtained. In addition, the documentation of the dose received by the patient during imaging procedure is possible with the help of an in-built software in conjunction with the MOSFET reader module.

Keywords: MOSFET; MV portal imaging; in vivo dosimetry; setup verification.

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Conflict of interest statement

Conflicts of interest None declared.

Figures

Figure 1
Figure 1
MOSFET dosimeter and reader module
Figure 2
Figure 2
Brass buildup cap (front and back view)
Figure 4
Figure 4
Position of standard sensitivity MOSFET dosimeter with buildup cap on the eye level in Rando phantom
Figure 3
Figure 3
Setup to determine calibration factor using MOSFET dosimeter
Figure 5
Figure 5
Both eyes inside the portal field during imaging
Figure 6
Figure 6
Both eyes away from the portal field during imaging
Figure 7
Figure 7
One eye inside the portal field during imaging
Figure 8
Figure 8
Calibration curve for standard sensitivity MOSFET dosimeter for 6 MV photon beam
Figure 9
Figure 9
Eye dose from both anterior and lateral portal fields (A) when both eyes were inside the field (B) when both the eyes were outside the field
See this image and copyright information in PMC

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