Dosimetric Accuracy Using the New Mathematical Tools for Inhomogeneous Denser Medium
International Journal of Clinical and Experimental Medical Sciences
Volume 3, Issue 2, March 2017, Pages: 23-29
Received: Apr. 6, 2017;
Accepted: Apr. 19, 2017;
Published: May 19, 2017
Views 541 Downloads 26
M. Jahangir Alam, Clinical Oncology Department, Ahsania Mission Cancer & General Hospital, Dhaka, Bangladesh
M. Ashrafur Rahman, Department of Arts & Sciences, AUST, Dhaka, Bangladesh
Khandoker Siddique-E. Rabbani, Department of Biomedical Physics & Technology, University of Dhaka, Dhaka, Bangladesh
Follow on us
It is possible to obtain a quality assurance (QA) of the dosimetry within a short time by using the new mathematical tools for a water phantom where dose measurements were made at two points only for a few square field sizes of the linear accelerator beam. The human body is not homogeneous. Water phantom makes it possible to create inhomogeneous phantoms by introducing blocks within it at suitable position to simulate body organs that may affect the dosage significantly. Two low cost inhomogeneous phantoms were developed using cork sheets and acrylic blocks to simulate the effects of normal lungs and cancerous lungs respectively using finite geometry and layer geometry. Monte Carlo Simulation was performed for each of these phantoms and detailed vertical and horizontal dose measurements were carried out. Percentage Depth Dose (PDD) measurements performed for the two point formalisms fixed at 100 cm Source to Surface Distance for both the homogeneous and inhomogeneous mediums and were compared with the doses generated by a Treatment Planning System. The quality of the methodology has ascertained firstly for a homogeneous medium. The formulated formalism of Tissue phantom ratio (TPR) was employed for inhomogeneous media particularly for finite and layer geometry using scattering factors obtained initially from detailed depth dose measurements. TPR conversion factors from homogeneous to inhomogeneous geometry were determined. The scattering factor was determined as a ratio of the depth dose in inhomogeneous medium and homogeneous medium. The quality factors of TPR values of homogeneous to inhomogeneous TPR conversion factor were also calculated. For all cases, the present results gave values which agreed very well to either actually measured values or with values calculated using TPS and these were also less than the international standard of deviation of 5%. The low cost inhomogeneous phantoms through modifications of the water phantom deliver better information on QA consuming less time than before and offering better QA than a detector array. The present work will have an impact on the quality assurance of dosimetry and safety of radiotherapy.
TPR = Tissue Phantom Ratio, TPR(EQS)H = Equation Simulated TPR for Homogeneous, TPR(TPS)H = TPR from TPS in Homogeneous, TPR(EQS)I = Simulated TPR for Inhomogeneous, TPR(TPS)I = TPR from TPS in Inhomogeneous, TPR(EQG)I = Generated TPR in Inhomogeneous, TPR(TPG)I = TPS Generated TPR in Inhomogeneous
To cite this article
M. Jahangir Alam,
M. Ashrafur Rahman,
Khandoker Siddique-E. Rabbani,
Dosimetric Accuracy Using the New Mathematical Tools for Inhomogeneous Denser Medium, International Journal of Clinical and Experimental Medical Sciences.
Vol. 3, No. 2,
2017, pp. 23-29.
Copyright © 2017 Authors retain the copyright of this article.
This article is an open access article distributed under the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/
) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The Physics of Radiology, Harold Elford Johns & John Robert Cunningham, Third edition, Fifth printing, 1978.
Sontag MR and Cunningham JR., Corrections to absorbed dose calculations for tissue in-homogeneities, Med. Phys, 1977; 4: 431–436.
Woo MK and Cunningham JR, The validity of the density scaling method in primary electron transport for electron and photon beams, Med. Phys, 1990; 17: 187–194.
Khan M. I, Runqing Jiang, Alexander Rehman Kiciak, Jalil ur, Muhammad Afzal, James C. L. Chow’ Dosimetric and radiobiological characterizations of prostate intensity-modulated radiotherapy and volumetric-modulated arc therapy. J. Med. Phys, 2016;41:162-168.
Purdy J. A. Relationship between tissue-phantom ratio and percentage depth dose. Med phys,1977; 4: 66-7.
Rahman M. A. and Jahangir Alam M.’ Analysis of Tissue Phantom Ratio of the Megavoltage Photon Beams’ Malays. j. med. biol. Res. 2016; 3: 61-68.
Rahman M. A., Jahangir Alam M., Akhtaruzzaman M. ‘Characteristics Analysis of High Energy External Radiotherapy Beams in Water’ Malays. j. med. biol. Res. 2016; 3, 51-60.
Jahangir Alam M. et al. A. modified formula for defining tissue phantom ratio of photon beams. Bangladesh Med. Coun Bull 2007; 33, 92-97.
Jari Viitanen, Development and evaluation of a Dose Planning system for radiation therapy, Espoo 1989.
Technical Report Series no.398, Absorbed Dose Determination in External Beam Radiotherapy. An International Code of Practice for Dosimetry Based on Standards of Absorbed Dose to Water, 2000.
Technical Reports Series No. 430: Commissioning and Quality Assurance of Computerized Planning Systems for Radiation Treatment of Cancer, International Atomic Energy Agency, Vienna, 2004.