title: On-line estimations of delivered radiation doses in three-dimensional conformal radiotherapy treatments of carcinoma uterine cervix patients in linear accelerator.
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 thein vivodose at isocenter (Diso,Transit) from the measured Sts. A locally fabricated pelvic phantom validated the estimations of Diso,Transitbefore implementing this method on actual patients. On-line dose estimations were made (3 times during treatment for each patient) in 24 patients. The Diso,Transitagreement with Diso,TPSin phantom was within 1.7% and the mean percentage deviation with standard deviation is -1.37% ±2.03% (n= 72) observed in patients. Estimatedin vivodose 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.
authors.affiliation: Department of Radiotherapy and Oncology, Kasturba Medical College Hospital (An Associated Teaching Hospital of Manipal University), Mangalore, Karnataka, India.
authors.forename: Suman Kumar
authors.initials: SK
authors.lastname: Putha
authors.affiliation: Department of Radiotherapy and Oncology, Kasturba Medical College Hospital (An Associated Teaching Hospital of Manipal University), Mangalore, Karnataka, India.
authors.forename: P U
authors.initials: PU
authors.lastname: Saxena
authors.affiliation: Department of Radiotherapy and Oncology, Kasturba Medical College Hospital (An Associated Teaching Hospital of Manipal University), Mangalore, Karnataka, India.
authors.forename: S
authors.initials: S
authors.lastname: Banerjee
authors.affiliation: Department of Radiotherapy and Oncology, Kasturba Medical College Hospital (An Associated Teaching Hospital of Manipal University), Mangalore, Karnataka, India.
authors.forename: Challapalli
authors.initials: C
authors.lastname: Srinivas
authors.affiliation: Department of Radiation Oncology, Manipal Hospital, Bengaluru, Karnataka, India.
authors.forename: B M
authors.initials: BM
authors.lastname: Vadhiraja
authors.affiliation: Department of Medical Radiation Physics, School of Allied Health Sciences, Manipal University, Manipal, Karnataka, India.
authors.forename: Ramamoorthy
authors.initials: R
authors.lastname: Ravichandran
authors.affiliation: Department of Radiological Physics, SMS Medical College, Jaipur, Rajasthan, India.
authors.forename: Mary
authors.initials: M
authors.lastname: Joan
authors.affiliation: Department of Radiotherapy and Oncology, Kasturba Medical College Hospital (An Associated Teaching Hospital of Manipal University), Mangalore, Karnataka, India.
authors.forename: K Dinesh
authors.initials: KD
authors.lastname: Pai
keywords: Cervix cancer; clinical dosimetry; conformal radiotherapy; on-line dose verification