A mathematical expression for %DD accurate from Co-60 to 24 MV

Bruce J. Gerbi

Research output: Contribution to journalLetterpeer-review

8 Scopus citations


Obtaining accurate %DD values for routine treatment calculations is essential in radiation therapy. Many papers have presented expressions to calculate this or related parameters but these expressions often required that the parameters needed by the equation be determined for each individual treatment unit. This paper presents an expression that calculates %DD values with a mean-square accuracy of — 1.0% versus measured values. The expression is applicable to beam energies ranging from Co-60 to 24 MV, field sizes from 4 X 4 to 40 X 40 cm2, and depths from 1 cm deeper than dmax to 30 cm. The only information required by this expression that is machine specific is the ionization ratio.

Original languageEnglish (US)
Pages (from-to)724-726
Number of pages3
JournalMedical Physics
Issue number4
StatePublished - Jul 1991
Externally publishedYes


  • dose calculation
  • mathematical expression
  • percentage depth dose


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