title: Energy imparted to the patient in diagnostic radiology: calculation of conversion factors for determining the energy imparted from measurements of the air collision kerma integrated over beam area.
abstract: The energy imparted to the patient in diagnostic radiology, related to radiation risk in examinations of the trunk and head, can be deduced from a measurement of the air collision kerma (or exposure) of the incident primary photons integrated over beam area by using a thin, flat ionisation chamber covering the entire roentgen beam. Factors for converting the integral of the air collision kerma to energy imparted to the patient have been calculated using a Monte Carlo method. The patient is simulated by laterally infinite water slabs with thicknesses from 100-300 mm. Calculations are performed for monoenergetic photons (5-300 keV) and energy spectra commonly used in diagnostic radiology (40-130 kV acceleration potential differences and values of the half-value thickness of air collision kerma in aluminium from 0.9 to 9.9 mm). Correction factors which take into account the additional escape of scattered photons from the sides of a laterally finite water slab as a function of field size and focal distance are also given.
mesh_terms: D006801:Humans; D008722:Methods; D008961:Models, Structural; D011829:Radiation Dosage; D011859:Radiography / Q000009:adverse effects*; D012306:Risk