Radiation dose reduction in dual-energy CT: Does it affect the accuracy of urinary stone characterization?

Mingliang Qu, Lifeng Yu, Daniel Gomez Cardona, Yu Liu, Xinhui Duan, Songtao Ai, Shuai Leng, Maria Shiung, Cynthia H. McCollough

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


OBJECTIVE. The purpose of this article is to assess the effect of radiation dose reduction in dual-energy CT (DECT) on the performance of renal stone characterization using a patient cohort. MATERIALS AND METHODS. CT data from 39 unenhanced DECT examinations performed for stone characterization were retrospectively analyzed in this study. Reduceddose images were simulated at 75%, 50%, and 25% of the routine dose using a previously validated noise-insertion algorithm. Differentiation between uric acid (UA) and non-UA stones was performed using a fixed cutoff value for the dual-energy ratio. ROC analysis was performed to determine optimal cutoff values and the associated sensitivity and specificity. RESULTS. Of the 206 stones found, 43 were UA and 163 were non-UA. The mean (± SD) volume CT dose index (CTDIvol) was 16.0 ± 4.0 mGy at the 100% dose level. The mean noise in 100-kV images increased from 40.9 ± 6.8 HU at 100% dose to 46.8 ± 8.8 HU, 57.7 ± 12.5 HU, and 85.4 ± 22.9 HU at 75%, 50%, and 25% dose levels, respectively. Using the default cutoff value, for stones 10 mm3 or larger, the sensitivity/specificity were 100.0%/98.8%, 82.8%/98.8%, and 89.3%/98.7%, at 75%, 50%, and 25% dose levels, respectively. ROC analysis showed varying optimal cutoff values at different dose levels. The sensitivity and specificity improved with use of these optimal cutoff values. Differentiation capability decreased for stones smaller than 10 mm3. CONCLUSION. At 75% of the 16-mGy routine dose, the sensitivity and specificity for differentiating UA from non-UA stones were minimally affected for stones 10 mm3 or larger. The use of optimal cutoff values for dual-energy ratio as dose decreased (and noise increased) provided improved performance.

Original languageEnglish (US)
Pages (from-to)W172-W176
JournalAmerican Journal of Roentgenology
Issue number2
StatePublished - Aug 1 2015


  • Dual-energy CT
  • Dual-energy ratio
  • Radiation dose reduction
  • Renal stone composition
  • Uric acid stones
  • Urinary stones

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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