Monte Carlo Simulation to Determine Deposition Ratio of Dosage in a-SI Epid with Dose Deposition on Water

Sri Herwiningsih, Sugeng Rianto, Firdy Yuana


The study aimed to explore the use of a-Si EPID as a dosimeter for IMRT delivery. The main objective of the study was to determine the ratio of dose deposited in a-Si EPID and the dose deposited in water. Linac used in the simulation was Electa Precise Linac and A-Si EPID model used in the study was based on the configuration of iView GT Elekta a-Si EPID. Study the characteristic of energy deposition at a-Si EPID and water detector shows that the energy deposition at a-Si EPID detector is higher than that of water detector at low photon energy (<0.1 MeV). This is caused by an enhancement of photoelectric interaction between photon beam and a-Si EPID detector at low energy X-rays. The simulation of dose deposition by using square fields show that the ratio between the dose deposition of a-Si EPID and the dose deposition of water detector (α) increases with an increase of the field size. The value of α ranges from 0.60 – 0.66. The similar result was shown in the simulation of dose deposition by using IMRT beam, in which the value of α ranges from 0.63 – 0.64. The α value is useful to relate the measured dose from detector to the equivalent dose of water, which is often used as a reference medium in radiotherapy dosimetry.  


a-Si EPID; Monte Carlo simulation; portal dosimetry; IMRT.

Full Text:



Antonuk, L.E. (2002), Electronic Portal Imaging Devices: A Review and Historical Perspective of Contemporary Technologies and Research, Physics in Medicine and Biology 47 (6): R31-65.

Herwiningsih, S. (2011), Validation of Elekta iViewGT a-Si EPID Model for Pre-Treatment Dose Verification of IMRT

Fields, Faculty of Science and Technology, Queensland University of Technology Brisbane.

Lewis, G. and E. Spezi. (2008), An Overview of Monte Carlo Treatment Planning for Radiotherapy, Radiation Protection Dosimetry 131 (1): 123-129.

Parent, L. (2006), The Use of Monte Carlo Methods to Study The Effect of X-Ray Spectral Variations on The Response of an Amorphous Silicon Electronic Portal Imaging Device. Doctor of Philosophy, University of London, London.

Parent, L., P.M. Evans, D.R. Dance, J. Seco and A. Fielding. (2006), Monte Carlo Modelling of a-Si EPID Response: The Effect of Spectral Variations with Field Size and Position, Medical Physics 33 (12): 4527-4540.

Staffurth, J. (2010), A Review of The Clinical Evidence for Intensity-Modulated Radiotherapy, Clinical Oncology 22 (8): 643 (Accessed 20 October 2010).

Van Elmpt, W., S. Nijsten, L. MCDermott, P. Lambin, B. Mijnheer and M. Wendling. (2008), A Literature Review of Electronic Portal Imaging for Radiotherapy Dosimetry, Radiotherapy and Oncology 88 (3): 289-309.

Verhaegen, F. and J. Seuntjens. (2003), Monte Carlo Modelling of External Radiotherapy Photon Beams, Physics in Medicine and Biology 48 (21): R107-R164.

Xing, L. and J.G.LI. (2000), Computer Verification of Fluence Map for Intensity Modulated Radiation Therapy, Medical Physics 27 (9): 2084-92. http://www.ncbi.



  • There are currently no refbacks.