ultra-low-dose computed tomography in urolithiasis-effect of an additional tin filter on image quality and radiation dose

To compare radiation dose and image quality of three CT-scanners using optimal dose protocols in patients with suspected urolithiasis regarding additional hardware (tin filter) and software (iterative reconstruction). Examinations from a single-source CT-scanner (A2) and a dual-source CT-scanner (DSCT) (A1) were compared to a tin filter DSCT (B) regarding dose-length product (DLP) and volume-weighted CT dose-index (CTDI_vol). DLP of B was 51 and 53% lower in comparison to A1 and A2 (78.62, 159.20 and 165.80 mGy.cm, respectively; P < 0.0001). CTDI_vol of B was 53% and 56% significantly lower compared to A1 and A2, respectively (1.52 vs. 3.22 vs. 3.46 mGy; P < 0.0001). Image quality in B proved to be similar to A1 and A2 (3.57, 3.51 and 3.60, respectively; P > 0.05). Inter-rater agreement regarding image quality was good for all CT-scanners (K = 0.62). Modern CTs with a built-in tin filter allow a significant reduction of radiation exposure in patients with suspected urolithiasis by optimizing the X-ray spectrum. (authors)