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

Abstract

Objective: To compare 128-slice multidetector computed tomography (MDCT) at 100kVp and 120kVp 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 180mAs and tube voltages of either 100kVp (n=14, mean age 26.71) or 120kVp (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 100kVp protocol were significantly lower than the 120kVp protocol (p=0.000, 0.000).

Conclusion: CT urography using 100kVp protocol resulted in reduction of radiation dose without loss of objective or subjective image quality.