MSCT and C-arm units: doses to patients in the chest angiography procedures

Since the late 1990', computed tomography (CT) technique has become an alternative solution to 'traditional' angiographies. Angio-CT (CTA) is most frequently used in cardiovascular procedures. Evaluation of patient doses in both CTA and 'traditional' cardio-angiography was the aim of the presented study. The measurements were performed using three multislice CT scanners (MSCT) for exposures covering the chest area and three C-arm units for conventional coronary angiographies. The patient was represented by a Rando Man phantom and organ doses were evaluated on the basis of readings from thermoluminescent dosimeters. Results: Doses absorbed during CT angiography (CTA) were evaluated for eight exposures at 'chest-angio' protocols and two exposures at 'coronary' protocols. Doses absorbed during conventional coronary angiography were also evaluated for eight exposures on the three C-arm units. Conclusions: 1. In coronary angiography carried out by C-arm units patient organ doses are distributed nonuniformly inside patient body (from up to 100 mGy in area of primary x-ray beam to about zero in quite near vicinity). Therefore, a low effective dose does not mean the low absorbed doses at all. 2. Doses to patients in CTA procedures covered the chest are distributed more uniformly and are dependent on exposure pattern (i.e. configuration of projections). 3. The lowest doses in CTA covered the chest are higher then those measured at conventional cardio-angiography. (author)