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CC BY 4.0 · Indian Journal of Neurosurgery
DOI: 10.1055/s-0045-1810088
Original Article

In-House Developed Dose Verification Phantom and Film Analysis Software for Gamma Knife Radiosurgery

Gopishankar Natanasabapathi
1   Department of Radiation Oncology, Dr B R Ambedkar Institute Rotary Cancer Hospital, All India Institute of Medical Sciences, New Delhi, India
2   Gamma Knife Unit, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi, India
,
Dhanabalan Rajasekaran
1   Department of Radiation Oncology, Dr B R Ambedkar Institute Rotary Cancer Hospital, All India Institute of Medical Sciences, New Delhi, India
,
Vellaiyan Subramani
1   Department of Radiation Oncology, Dr B R Ambedkar Institute Rotary Cancer Hospital, All India Institute of Medical Sciences, New Delhi, India
,
Daya Nand Sharma
1   Department of Radiation Oncology, Dr B R Ambedkar Institute Rotary Cancer Hospital, All India Institute of Medical Sciences, New Delhi, India
,
Shashank Sharad Kale
2   Gamma Knife Unit, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi, India
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Abstract

Objective

The aim of the study was to design a simple and quick plan verification system for Gamma Knife radiosurgery (GKSRS).

Materials and Methods

The latest Icon model of GKSRS includes cone beam computed tomography (CBCT) imaging. An in-house-developed phantom consists of an outer cylinder of 16-cm diameter and a circular nylon plate with threaded groove upon which an inner acrylic cylinder was fixed. This inner cylinder, further divided into two equal parts, holds EBT3 radiochromic film (Ashland Advanced Materials, NJ, United States) in the midportion for irradiation. The phantom was mounted on the Leksell stereotactic frame and set up for CBCT imaging in the treatment couch. The CBCT images were imported into the treatment planning system (TPS) for planning. A prescription dose of 2.5 Gy at the 50% isodose line was planned and a phantom with film was set in the GKSRS couch for irradiation. An in-house-developed MATLAB software (MathWorks, United States) calibrated the film, converted optical density to dose map and performed a comparison with the TPS dose. Film calibration with various doses of 0.5, 1.5, 3, and 5.5 Gy was performed with the same phantom setup as well. All films were scanned 24 hours postirradiation using an EPSON12000XL scanner at 48-bit resolution, 300 dpi, and saved as TIFF images.

Results

Gamma index analysis showed 90.5% pixel pass rate for dose difference (DD) and distance to agreement (DTA) of 3%/2-mm pass criteria. This study demonstrates a quick way to verify the TPS dose distribution during commissioning.

Conclusion

The newly designed apparatus is an effective end-to-end test dosimetry tool for GKSRS, specifically during clinically commissioning.

Keywords

film dosimetry - Gamma Knife - head phantom - gamma index analysis

Note

This work was presented as poster discussion at the AAPM 66th Annual Meeting & Exhibition (AAPM2024) held in Los Angeles, California, United States, from July 21 to 25, 2024.




Publication History

Article published online:
28 July 2025

© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/)

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