A modified geometric factor approach to internal gamma ray dosimetry.
In internal gamma-ray dosimetry, the conventional geometric factor approach, where the "effective absorption coefficient" is taken as 0 or 0-028 cm-1, irrespective of source energy, leads to significant errors especially in the low energy region. An ettempt has been made in this paper to modify the approach to increase the accuracy of calculation and to extend its usefulness to low energies while retaining its inherent simplicity. The modification consists in replacing the effective absorption coefficient by the attenuation coefficients appropriate to the source energies and taking into account the effects due to multiple scattering by using point source build-up factor. The method has been applied for the particular case of dosimetry of a sphere. Comparison of the results obtained by this method with those got from Monte Carlo computations indicates excellent agreement at higher energies and a departure of around 15 per cent only at lower energies (as against a variation of 400 per cent when conventional geometric factor approach is used).
D000042:Absorption; D005720:Gamma Rays; D008433:Mathematics; D011829:Radiation Dosage