Radiation doses from phantom measurements at high-pitch dual-source computed tomography coronary angiography
Robert Goetti1, Sebastian Leschka, Markus Boschung
1Department of Diagnostic Radiology, University Hospital Zurich, Raemistrasse 100, CH-8091 Zurich, Switzerland. RobertPaul.Goetti@usz.ch
Objective:
To compare radiation doses delivered at prospectively ECG-triggered sequential- (SEQ), retrospectively ECG-gated spiral- (RETRO) and prospectively ECG-triggered high-pitch spiral- (HP) computed tomography coronary angiography (CTCA) protocols, as well as catheter coronary angiography (CCA) using an anthropomorphic phantom.
Materials And Methods:
An anthropomorphic Alderson phantom equipped with 50 thermoluminescent dosimeters (TLDs) was scanned using different CTCA protocols and an uncomplicated diagnostic CCA examination was simulated. Absorbed doses were experimentally determined and effective doses calculated using the dose-length product (DLP) for CTCA and the dose-area product (DAP) for CCA, as well as according to International Commission on Radiation Protection (ICRP) publications 60 and 103.
Results:
Effective organ doses were significantly lower for HP protocols (100kV: 0.17±0.26mSv; 120kV: 0.26±0.39mSv) compared to SEQ protocols (100kV: 0.50±0.79mSv; 120kV: 0.90±1.41mSv; each p<0.05) and compared to RETRO protocols (100kV: 1.59±2.12mSv; 120kV: 2.75±3.50mSv; each p<0.05). Effective organ doses at HP-CTCA tended to be lower than at CCA (0.37±0.40mSv), however this was not statistically significant (p=0.13). Effective doses calculated according to ICRP guidelines could be estimated using the DLP and a conversion coefficient of k=0.034mSv/[mGycm] (ICRP103) or k=0.028mSv/[mGycm] (ICRP60), respectively. HP-CTCA led to a dose reduction of 89% compared to RETRO-CTCA, regardless of the calculation method used.
Conclusions:
Radiation doses as determined by phantom measurements are significantly lower at HP-CTCA compared to SEQ-CTCA and RETRO-CTCA and comparable to uncomplicated diagnostic CCA.
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