# New formula for Calculation of Cobalt-60 Percent Depth Dose

Tahmasebi Birgani, M. J. and Ghorbani, M. (2005) New formula for Calculation of Cobalt-60 Percent Depth Dose. Iranian Journal of Medical Physics, 2 (3). pp. 53-60.  Preview
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Official URL: http://ijmp.mums.ac.ir/article_8121.html

## Abstract

Introduction: Â On Â the Â basis Â of Â percent Â depth Â dose Â (PDD) Â calculation, Â the Â application Â ofÂ dosimetry Â in Â radiotherapy Â has Â an Â important Â role Â to Â play Â in Â reducing Â the Â chance Â of Â tumorÂ recurrence. The aim of this study is to introduce a new formula for calculating the centeral axisÂ percent depth doses of Cobalt-60 beam. Â Materials and Methods: In the present study, based on the British Journal of Radiology (BJR)Â table, nine new formulas are developed and evaluated for depths of 0.5 - 30 cm and fields ofÂ )4 4( Ã� ) 45 45 ( Ã� â�� cm2. Â Â To Â evaluate Â the Â agreement Â between Â the Â formulas Â and Â the Â table, Â theÂ average of the absolute differences between the values was used and the formula with the leastÂ average was selected as the best fitted formula. The Microsoft Excel 2000 and the Datafit 8.0 softÂ wares were used to perform the calculations. Â Â Â Results: The results of this study indicated that one amongst the nine formulas gave a betterÂ agreement with the PDDs listed in the table of BJR. The new formula has two parts in terms ofÂ log (A/P). The first part as a linear function with the depth in the range of 0.5 to 5 cm and theÂ other one as a second order polynomial with the depth in the range of 6 to 30 cm. The average ofÂ the differences between the tabulated and the calculated data using the formula ( Î� ) is equal toÂ 0.3152. Â Discussion Â and Â Conclusion: Â Therefore, Â the Â calculated Â percent Â depth Â dose Â data Â based Â on Â thisÂ formula has a better ageement with the published data for Cobalt-60 source. This formula could beÂ used to calculate the percent depth dose for the depths and the field sizes not listed in the BJR table. Â

Item Type: Article WA Public HealthWN Radiology . Diagnostic Imaging Journals > Iranian J Medical Physics ijmp ijmp 21 Jan 2018 15:47 21 Jan 2018 15:47 http://eprints.mums.ac.ir/id/eprint/9012

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