In vivo dose estimations through transit signal measured with thimble chamber positioned along the central axis at electronic portal imaging device level in medical linear accelerator in carcinoma of the middle‑third esophagus patients undergoing three‑dimensional conformal radiotherapy

*, Putha Suman Kumar and Banerjee, Sourjya and *, Arun Kumar E.S and Challapalli, Srinivas and *, Vadhiraja B. M. and Saxena, Prakash P U and *, Ramamoorthy Ravichandran and Pai, Dinesh Kasturi (2018) In vivo dose estimations through transit signal measured with thimble chamber positioned along the central axis at electronic portal imaging device level in medical linear accelerator in carcinoma of the middle‑third esophagus patients undergoing three‑dimensional conformal radiotherapy. Journal of Cancer Research and Therapeutics, 14 (2). pp. 300-307. ISSN 0973-1482

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Abstract

Objective: This study presents a method to estimate midplane dose (Diso,transit) in vivo from transit signal (St) measured with thimble ionization chamber in cancer of the middle‑third esophagus patients treated with three‑dimensional radiotherapy (RT). This detector is positioned at the level of electronic portal imaging device in the gantry of a medical linear accelerator. Materials and Methods: Efficacy of inhomogeneity corrections of three dose calculation algorithms available in XiO treatment planning system (TPS) for planned dose (for open fields) (Diso,TPS) was studied with three heterogeneous phantoms. Diso,transit represents measured signal at transit point (St) far away correlating to dose at isocenter. A locally fabricated thorax phantom was used to measure the in vivo midplane dose (Diso,mid) which was also estimated through St. Thirteen patients with carcinoma of the middle‑third esophagus treated with three‑dimensional conformal RT were studied. St was recorded (three times, with a gap of 5–6 fractions during the treatment) to estimate Diso,transit, which was compared with the doses calculated by TPS. Results: The dose predictions by superposition algorithm were superior compared to the other algorithms. Percentage deviation of Diso,transit, Diso,mid with Diso,TPS combined all fields was 2.7 and –2.6%, respectively, with the thorax phantom. The mean percentage deviation with standard deviation of estimated Diso,transit with Diso,TPS observed in patients was within standard deviation –0.73% ±2.09% (n = 39). Conclusions: Midplane dose estimates in vivo using this method provide accurate determination of delivered dose in the middle-third esophagus RT treatments. This method could be useful in similar clinical circumstances for dose confirmation and documentation

Item Type: Article
Uncontrolled Keywords: Conformal radiotherapy, esophagus cancer, in vivo dose, transit signal
Subjects: Medicine > KMC Mangalore > Radiotherapy and Oncology
Depositing User: KMCMLR User
Date Deposited: 07 Dec 2018 06:35
Last Modified: 07 Dec 2018 06:35
URI: http://eprints.manipal.edu/id/eprint/152410

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