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Novel Radiochromic Films for Dosimetry in Gamma Knife Stereotactic Radiosurgery

A Mittal1*, N Gopishankar2, A Verma3, P Kumar4, (1) All India Institute Of Medical Sciences, New Delhi, IN (2) All India Institute of Medical Sciences, New Delhi, IN (3) University Of Delhi, Delhi, IN (4) All India Institute Of Medical Sciences, New Delhi, IN

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose:
Indigenous development of new radiochromic films and evaluation of their performance in gamma knife dosimetry.

Methods:
Amine functionalized diacetylene compound was synthesized by organic chemistry route. The synthesized monomer was used to obtain 200µm thick radiochromic film. The film was cut into 2x2 cm² sized pieces and positioned in a spherical solid water phantom at x = 100, y = 100 and z = 100. The films were irradiated to 0.8, 1.6, 3.2, 6.4, 12.8 Gy calibration doses. A separate film from the same batch was positioned for treatment irradiation purpose in the same phantom. The quantitative study of color change in the film was performed by using high resolution scanner (Epson 10000XL) in reflection mode at 48 bit and 720 dpi. The scanned images were saved in tiff format and analyzed using ImageJ and MATLAB software coding. Same irradiation and scanning procedure were performed with Gafchromic EBT3 film for comparison. A calibration plot was made between optical density and dose for generating dose maps. The spectral absorbance of the irradiated films was determined using UV Vis spectrophotometer.

Results:
The developed films exhibited significant color change at minimum irradiation of 0.8 Gy. The films exhibited a linear dose response with 1.87% uncertainty and were tissue equivalent. A maximum absorbance peak at 624nm was observed. Gamma analysis with respect to EBT3 films showed 90% and 98% pixel pass rate at 2%-2mm and 3%-3mm gamma pass criteria respectively. There were mismatches at some points in the isodose lines which were attributed to the defects during film preparation which requires further improvements.

Conclusion:
This work led to the development of novel radiochromic films for gamma knife dosimetry. The dose response curve and gamma analysis confirmed that the performance of the films is comparable with that of the commercially available films.

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Funding Support, Disclosures, and Conflict of Interest: This research has been funded by Indian Council of Medical Research (File number: ICMR 5/3/8/346/2018-ITR), New Delhi, India.

Keywords

Gamma Knife, Radiochromic Film, Dosimetry

Taxonomy

TH- Radiation Dose Measurement Devices: Radiochromic film

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