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.

IJMP_Volume 2_Issue 3_Pages 53-60.pdf

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

Item Type: Article
Subjects: WA Public Health
WN Radiology . Diagnostic Imaging
Divisions: Journals > Iranian J Medical Physics
Depositing User: ijmp ijmp
Date Deposited: 21 Jan 2018 15:47
Last Modified: 21 Jan 2018 15:47

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