OBJECTIVE: The purpose of this study was to evaluate stone detection, assessment of secondary signs of stone disease, and diagnostic confidence utilizing submillisievert CT with model-based iterative reconstruction (MBIR) in a North American population with diverse body habitus.
MATERIALS AND METHODS: Fifty-two adults underwent stone CT using a split-dose protocol; weight-based projected volume CT dose index (CTDIvol) and dose-length product (DLP) were divided into two separate acquisitions at 80% and 20% dose levels. Images were reconstructed with MBIR. Five blinded readers counted stones in three size categories and rated "overall diagnostic confidence" and "detectability of secondary signs of stone disease" on a 0-4 scale at both dose levels. Effective dose (ED) in mSv was calculated as DLP multiplied by conversion coefficient, k, equal to 0.017.
RESULTS: Mean ED (80%, 3.90 ± 1.44 mSv; vs 20%, 0.97 ± 0.34 mSv (p < 0.001)) and number of stones detected (80%, 193.6 ± 25.0; vs 20%, 154.4 ± 15.4 (p = 0.03)) were higher in scans at 80% dose level. Intrareader correlation between scans at 80% and 20% dose levels was excellent (0.83-0.97). With 80% scans as reference standard, mean sensitivity and specificity at 20% varied with stone size (< 3 mm, 74% and 77%; ≥ 3 mm, 92% and 82%). The 20% scans scored lower than 80% scans in diagnostic confidence (2.46 ± 0.50; vs 3.21 ± 0.36 (p < 0.005)) and detectability of secondary signs (2.41 ± 0.39; vs 3.19 ± 0.29 (p < 0.005)).
CONCLUSION: Aggressively dose-reduced (~ 1 mSv) MBIR scans detected most urinary tract stones of 3 mm or larger but underperformed the low-dose reference standard (3-4 mSv) scans in small (< 3 mm) stone detection and diagnostic confidence.
Written by:
Glazer DI, Maturen KE, Cohan RH, Davenport MS, Ellis JH, Knoepp US, Weadock WJ, Platt JF. Are you the author?
Department of Radiology, University of Michigan Health System, UH B1 D502, 1500 E Medical Center Dr, Ann Arbor, MI 48109.
Reference: AJR Am J Roentgenol. 2014 Dec;203(6):1230-5.
doi: 10.2214/AJR.13.12271
PubMed Abstract
PMID: 25415699