On-line estimations of delivered radiation doses in three-dimensional conformal radiotherapy treatments of carcinoma uterine cervix patients in linear accelerator

Putha, Suman Kumar and Saxena, Prakash P U and Banerjee, Sourjya and Challapalli, Srinivas and *, Vadhiraja B. M and *, Ramamoorthy Ravichandran and Joan, Mary and Pai, Dinesh Kasturi (2016) On-line estimations of delivered radiation doses in three-dimensional conformal radiotherapy treatments of carcinoma uterine cervix patients in linear accelerator. Journal of Medical Physics, 41 (4). pp. 224-233. ISSN 09716203

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Abstract

Transmission of radiation fluence through patient’s body has a correlation to the planned target dose. A method to estimate the delivered dose to target volumes was standardized using a beam level 0.6 cc ionization chamber (IC) positioned at electronic portal imaging device (EPID) plane from the measured transit signal (St) in patients with cancer of uterine cervix treated with three-dimensional conformal radiotherapy (3DCRT). The IC with buildup cap was mounted on linear accelerator EPID frame with fixed source to chamber distance of 146.3 cm, using a locally fabricated mount. Sts were obtained for different water phantom thicknesses and radiation field sizes which were then used to generate a calibration table against calculated midplane doses at isocenter (Diso,TPS), derived from the treatment planning system. A code was developed using MATLAB software which was used to estimate the in vivo dose at isocenter (Diso,Transit) from the measured Sts. A locally fabricated pelvic phantom validated the estimations of Diso,Transit before implementing this method on actual patients. On-line dose estimations were made (3 times during treatment for each patient) in 24 patients. The Diso,Transit agreement with Diso,TPS in phantom was within 1.7% and the mean percentage deviation with standard deviation is −1.37% ±2.03% (n = 72) observed in patients. Estimated in vivo dose at isocenter with this method provides a good agreement with planned ones which can be implemented as part of quality assurance in pelvic sites treated with simple techniques, for example, 3DCRT where there is a need for documentation of planned dose delivery.

Item Type: Article
Uncontrolled Keywords: Cervix cancer; clinical dosimetry; conformal radiotherapy; on-line dose verification
Subjects: Medicine > KMC Mangalore > Radiotherapy and Oncology
Depositing User: KMCMLR User
Date Deposited: 15 Jul 2017 05:04
Last Modified: 15 Jul 2017 05:04
URI: http://eprints.manipal.edu/id/eprint/149360

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