Reducing radiation in CT urography for hematuria: Effect of using 100 kilovoltage protocol

Objective: To compare 128-slice multidetector computed tomography (MDCT) at 100 kVp and 120 kVp for image quality and radiation dose. Materials and methods: Our study had approval of our institutional review board. We retrospectively selected 25 patients who underwent CT urography for the evaluation of hematuria. The CT scans were taken with 128-slice MDCT, with three phases (precontrast, nephrographic, and excretory), using an automatic tube current modulation with reference tube level of 180 mA s and tube voltages of either 100 kVp (n = 14, mean age 26.71) or 120 kVp (n = 11, mean age 25.54). The signal-to-noise-ratio (SNR) and contrast-to-noise-ratio (CNR) of the urinary tract, the subjective image quality of the urinary tract evaluated with a five point scale by two radiologists and the effective dose calculated on the basis of dose-length-product (DLP) and volume-CT-dose-index (CTDIvol) were compared between the groups with Student's t test or Mann-Whitney U test. Results: There was no significant difference in the SNR (p = 0.358), CNR (p = 0.303) and the subjective image quality (p = 0.486) between the two protocols. The mean CTDIvol, DLP and the effective dose in the 100 kVp protocol were significantly lower than the 120 kVp protocol (p = 0.000, 0.000). Conclusion: CT urography using 100 kVp protocol resulted in reduction of radiation dose without loss of objective or subjective image quality.