A comparison of radiation dose in single and split bolus multidetector computed tomography urography

Abstract

Introduction: Routine multidetector computed tomography (MDCT) urography protocols include three phase scan with single bolus contrast material injection. To reduce the radiation dose a split bolus MDCT urography technique has been introduced. Methods: Nephrographic phase in single bolus was obtained by injecting 90 ml of Ioversol (Optiray320mgI/ml) contrast at the rate of 3ml/s during the preset time of 90 second. The excretory phase was taken at the delay of 10 minutes after the contrast injection. For split bolus only two phases (unenhanced and combined) were scanned from the diaphragm to the base of the urinary bladder. The combined phase in split bolus was performed by injecting the contrast in two bolus in which 40 ml at 2ml/s was injected in the first bolus and after a delay of 9 minutes, 60 ml at a rate of 3ml/s was injected, then the scan was obtained 90 second after the second bolus. The volume CT dose index (CTDIvol) and CT dose length product (CTDLP) were assessed in CT work station. Results: The mean effective radiation dose for single bolus MDCT urography was 40.5% more than the split bolus MDCT urography. Conclusion: Split bolus MDCT urography protocol was significantly better in effective radiation dose reduction compared with the single bolus MDCT urography protocol.