Keywords:
Radiation physics, Radioprotection / Radiation dose, CT, Dosimetry, Radiation safety, Physics
Authors:
T. Johnson, R. P. Marcus, K. Neumair, M. F. Reiser, F. Bamberg; Munich/DE
DOI:
10.1594/ecr2012/C-0788
Purpose
In CT examinations of normal weight subjects,
standard conversion factors can be used to estimate radiation exposure.
In obese patients,
a large share of the dose is absorbed in subcutaneous fat,
so that the standard factors yield false high values for radiation doses.
The actual biologically relevant exposure of the organs is certainly lower,
but the quantification is difficult,
i.e.
it is difficult to estimate the dose increase due to limited transmission and scattered radiation on the one hand and “shielding” of the organs due to the fat distribution on the other hand.
In clinical practice,
CT frequently remains the only option for diagnostic imaging in morbidly obese patients,
and except for life-threatening conditions,
an estimation and weighing of diagnostic information against the risk of cancer due to the relatively high radiation exposure is required in most countries.
The aim of this study is to establish corrected conversion factors for obese patients,
also taking image quality and diagnostic value into account.