SU‐FF‐I‐48: Normalized Conceptus Doses for Multi‐Detector CT Examinations : A Monte Carlo Study

Abstract

Purpose: To provide normalized conceptus dose data for the estimation of the conceptus dose from examinations performed using a 16‐slice CT scanner. Method and Materials: The Monte Carlo N‐Particle (MCNP) radiation transport code was employed in this study to model the Siemens Sensation 16 CT scanner. Four mathematical phantoms were used simulating women at 0, 3, 6 and 9 months of gestation. The contribution to the conceptus dose from a single scan was measured at various positions across the phantom. To verify MCNP results, conceptus dose measurements were carried out by means of (a) three physical anthropomorphic phantoms simulating pregnancy at 0, 3 and 6 months of gestation and (b) thermoluminescence dosimetry. The scans were carried out using a Siemens Sensation 16 scanner. Results: The results consist of normalized conceptus dose coefficients for single slices of 2 cm width across the 4 mathematical phantoms. These coefficients were defined as the conceptus dose contribution from a single slice divided by the CTDI free‐in‐air measured with identical scanning parameters. Normalized conceptus dose data were calculated for (a) 120 kV and 140 kV and (b) 12 mm and 24 mm beam collimation. The mean conceptus dose can be calculated using the following formula: urn:x-wiley:00942405:media:mp0425:mp0425-math-0001 where Dc is the dose to the conceptus, CTDIF is the CTDI free‐in‐air, BC is the beam collimation in mm, fz the normalized conceptus dose coefficients and z1, z2 the boundaries of the scanned volume. Taking into account phantom differences, there was a good agreement between the results of the TLD measurements and the mathematical simulation. Conclusion: Accurate estimation of conceptus doses from MDCT examinations performed using a multi‐detector scanner can be made using the dose data provided in this study.