Intro
: DSCT provides improved temporal resolution due to the simultaneous use of two x-ray sources & detectors. Although use of two sources may increase radiation, the DSCT offers key mechanisms to reduce dose (i.e. pitch adaptation, tube current modulation (TCM) & prospective triggering). Thus, our aim was to assess the patient radiation exposure associated with DSCT and identify variations based on the use of different scan related parameters.
Methods
: Prospective study of a single tertiary medical center where radiation and image quality related data was collected on 304 consecutive patients (pts) presenting for clinical CCT examination. Effective radiation dose was calculated by multiplying the dose-length product × (k=.017 mSv/mGy/cm). Image quality was rated on a subjective IQ score [1=poor to 4=excellent], as well as contrast (CNR) and signal-to-noise (SNR) ratios. Adjusted means of increased radiation dose were calculated based on linear regression models.
Results:
Among 304 consecutive studies (mean age 56.4, BMI 29.4 kg/m
2
, 37% Female), 60% were performed for coronary evaluation, 8% for CABG, 18% for pulmonary veins and 11% for aortic disease. The average radiation dose was 13.5±9.2mSv [range 0.5–55.5 mSv]. TABLE
provides unadjusted and adjusted mean radiation dose for parameters which had a significant univariate association with radiation dose. Independent predictors of lower radiation included low kV, use of TCM, higher pitch, smaller scan length, and regular heart rhythm. Selected use of various TCM algorithms & low KV resulted in no significant difference in IQ, CNR, or SNR.
Conclusions
: DSCT is associated with a wide range of patient radiation exposure. The variability in dose is due to both controllable parameters (i.e. use of TCM, low kV, scan length) as well as parameters that cannot be altered (i.e. irregular rhythm). These results suggest that individualizing scan protocols may result in lower radiation dose without compromising image quality.
Table:
Cardiac DSCT Parameters Affecting Patient Radiation Dose
Radiation dose in CT colonography–trends in time and differences between daily practice and screening protocols
