Analysis of Tissue Phantom Ratio of the Megavoltage Photon Beams
DOI:
https://doi.org/10.18034/mjmbr.v5i2.452Keywords:
TPR, PDD, Dosimetry, Photon beam, Radiation MeasurementAbstract
Iso-centric beam data, phantom tissue ratios (TPR) are a dosimetric quantity commonly used to describe the change in dose with depth in tissue. Measurement of this is time-consuming and has the possibility of lose the consistency. The value of this quantity of any filed size in any depth is possible to calculate conveniently by the newly developed formula using only percentage depth dose (PDD) data of two fields. PDD for square fields ranging from 2 to 30 cm and various depths in increment of 0.4 cm up to maximum 30 cm have been measured in water at a fixed source surface distance (SSD) of 90 cm for 4, 6 and 15 MV photon beams in Ahsania Mission Cancer & General Hospital (AMCGH), Dhaka, Bangladesh. TPR values calculating for these energies of the same field sizes, depths and SSD by using the developed formula compared with those determined from the measured PDD data using a standard formula and had the good agreement. Mean error less than 1% observed between these TPR values.
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References
Bedford JL, Childs PJ, Nordmark Hansen V et al. Commissioning and quality assurance of the Pinnacle(3) radiotherapy treatment planning system for external beam photons. Br J Radiol 2003; 76: 163-76
Bjarngard BE, Bar-Aroma R, Corrao A. A survey of methods to calculate monitor settings. Int J Radiat Oncol Biol Phys 1994; 28: 749
Bjärngard BE, Zhu TC, Cyborg C.Tissue-phantom ratio and percentage depth doses. Med phys1996; 23: 629.
Das I J et al. Characteristics of a dedicated linear accelerator-based stereotactic radiosurgery –radiotherapy unit Radiotherapy, Oncol1996; 38: 61-8.
G. X Ding and Rob Krauss. An empirical formula to obtain tissue-phantom ratios from and percentage depth dose curves for small fields. Phys. Med. Biol 2013; 58: 4781.
Ganesh Narayanasamy, Wilbert Cruz, Niko Papanikolaou, Sotirios Stathakis. TPR comparison with & without PSF correction. Int. J. Cancer ther Oncol 2015; 3; 3024.
M. Jahangir Alam et al. A modified formula for defining tissue phantom ratio of photon beams. Bangladesh Med. Coun Bull 2007; 33: 92-97.
Neil Richmond and Robert Brackenridge. A comparison of small-field tissue phantom ratio data generation methods for an Elekta Agility 6 MV photon beam. Medical Dosimetry 2014; 39: 60-63.
Purdy J A. Relationship between tissue-phantom ratio and percentage depth dose. Med phys1977; 4: 66-7.
Rahman M A , M. Jahangir Alam and M. Akhtaruzzaman, Characteristics analysis of high energy external radiotherapy beams in water. Malays. j. med. biol. Res 2016. Accepted, 3:1
Sharma S C et al. J. Appl. Clin. Med. Phys 2007; 8: 119-125
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