title: Monte Carlo based investigations of electron contamination from telecobalt unit head in build up region and its impact on surface dose.
abstract: A Telecobalt unit has wide range of applications in cancer treatments and is used widely in many countries all around the world. Estimation of surface dose in Cobalt-60 teletherapy machine becomes important since clinically useful photon beam consist of contaminated electrons during the patient treatment. EGSnrc along with the BEAMnrc user code was used to model the Theratron 780E telecobalt unit. Central axis depth dose profiles including surface doses have been estimated for the field sizes of 0×0, 6×6, 10×10, 15×15, 20×20, 25×25, 30×30cm2and at Source-to-surface distance (SSD) of 60 and 80cm. Surface dose was measured experimentally by the Gafchromic RTQA2 films and are in good agreement with the simulation results. The central axis depth dose data are compared with the data available from the British Journal of Radiology report no. 25. Contribution of contaminated electrons has also been calculated using Monte Carlo simulation by the different parts of the Cobalt-60 head for different field size and SSD's. Moreover, depth dose curve in zero area field size is calculated by extrapolation method and compared with the already published data. They are found in good agreement.
authors.affiliation: School of Basic Medical Sciences, Department of Physics, Savitribai Phule Pune University, Pune 411007, India; Department of Radiotherapy, Cama & Albless Hospital, Mumbai, India.
authors.forename: A S
authors.initials: AS
authors.lastname: Jagtap
authors.affiliation: Radiological Physics and Advisory Division, Health, Safety and Environment Group, Bhabha Atomic Research Centre, Mumbai, India.
authors.forename: T
authors.initials: T
authors.lastname: Palani Selvam
authors.affiliation: Abasaheb Garware College, Pune, India. Electronic address: amolbhushan@gmail.com.
authors.forename: B J
authors.initials: BJ
authors.lastname: Patil
authors.affiliation: SAMEER, IIT Powai Campus, Mumbai 400076, India.
authors.forename: S T
authors.initials: ST
authors.lastname: Chavan
authors.affiliation: SAMEER, IIT Powai Campus, Mumbai 400076, India.
authors.forename: S N
authors.initials: SN
authors.lastname: Pethe
authors.affiliation: School of Basic Medical Sciences, Department of Physics, Savitribai Phule Pune University, Pune 411007, India.
authors.forename: Gauri
authors.initials: G
authors.lastname: Kulkarni
authors.affiliation: School of Basic Medical Sciences, Department of Physics, Savitribai Phule Pune University, Pune 411007, India.
authors.forename: S S
authors.initials: SS
authors.lastname: Dahiwale
authors.affiliation: School of Basic Medical Sciences, Department of Physics, Savitribai Phule Pune University, Pune 411007, India.
authors.forename: V N
authors.initials: VN
authors.lastname: Bhoraskar
authors.affiliation: School of Basic Medical Sciences, Department of Physics, Savitribai Phule Pune University, Pune 411007, India. Electronic address: sanjay@physics.unipune.ac.in.
authors.forename: S D
authors.initials: SD
authors.lastname: Dhole
mesh_terms: D003037:Cobalt Radioisotopes; D003198:Computer Simulation; D004583:Electrons; D004867:Equipment Design; D019544:Equipment Failure Analysis; D015233:Models, Statistical; D009010:Monte Carlo Method; D010315:Particle Accelerators / Q000295:instrumentation*; D011829:Radiation Dosage; D011878:Radiotherapy / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012542:Scattering, Radiation
chemical_list: D003037:Cobalt Radioisotopes; C000615395:Cobalt-60
keywords: Gafchromic film; Monte Carlo simulation; Percentage Depth Dose; Secondary electrons; Surface dose; Telecobalt unit