Original Investigation| Volume 30, ISSUE 6, P1033-1038, June 2023

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Tin-filtered 100 kV Ultra-low-dose Abdominal CT for Calculi Detection in the Urinary Tract: A Comparative Study of 510 Cases

Published:August 10, 2022DOI:


      • Tin prefiltration allows for considerable dose reduction in ultra-low-dose scans for detection of urinary calculi.
      • Sn100 kVp-based protocols may bear a radiation dose advantage over Sn150 kVp which is more frequently evaluated in literature.
      • With spectral shaping, image quality in ultra-low-dose settings remains comparable to standard low-dose scans.


      For detection of urinary calculi, unenhanced low-dose computed tomography is the method of choice, outperforming radiography and ultrasound. This retrospective monocentric study aims to compare a clinically established, dedicated low-dose imaging protocol for detection of urinary calculi with an ultra-low-dose protocol employing tin prefiltration at a standardized tube voltage of 100 kVp.


      Two study arms included a total of 510 cases. The “low-dose group” was comprised of 290 individuals (96 women; age 49 ± 16 years; BMI 27.23 ± 5.60 kg/m2). The “ultra-low-dose group” with Sn100 kVp consisted of 220 patients (84 women; age 47 ± 17 years; BMI 26.82 ± 5.62 kg/m2). No significant difference was ascertained for comparison of age (p = 0.132) and BMI (p = 0.207) between cohorts. For quantitative assessment of image quality, image noise was assessed.


      No significant difference regarding frequency of calculi detection was found between groups (p = 0.596). Compared to the low-dose protocol (3.08 mSv; IQR 2.22–4.02 mSv), effective dose was reduced by 62.35% with the ultra-low-dose protocol employing spectral shaping (1.16 mSv; IQR 0.89–1.54 mSv). Image noise was calculated at 18.90 (IQR 17.39–21.20) for the low-dose protocol and at 18.69 (IQR 17.30–21.62) for the ultra-low-dose spectral shaping protocol. No significant difference was ascertained for comparison between groups (p = 0.793).


      For urinary calculi detection, ultra-low-dose scans utilizing spectral shaping by means of tin prefiltration at 100 kVp allow for considerable dose reduction of up to 62% over conventional low-dose CT without compromising image quality.

      Key Words

      Abbreviations and acronyms:

      ACR (American College of Radiology), BMI (body mass index), CT (computed tomography), ED (effective dose), HU (Hounsfield units), IR (iterative reconstruction), IQR (interquartile range), ROI (region of interest)
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