BACKGROUND: The purpose of this prospective trial was to compare the performance of ultra-low-dose computed tomography (CT) reconstruction algorithms with routine low-dose CT for the detection of urolithiasis.
METHODS: 48 consenting adults prospectively underwent routine low-dose non-contrast CT immediately followed by ultra-low-dose series targeted at 70-90% reduction from routine low-dose technique (sub-mSv range). Ultra-low-dose series were reconstructed with FBP, ASIR, and MBIR techniques. Transverse (axial) and coronal images were sequentially reviewed by three relatively inexperienced trainees (radiology resident, urology fellow, and abdominal imaging fellow). Three experienced abdominal radiologists independently reviewed the routine low-dose FBP images, which served as the reference standard.
RESULTS: Mean effective dose for the ultra-low-dose scans was 0.91 mSv (median, 0.82 mSV), a 78 ± 5% reduction compared with routine low-dose. The overall per-stone sensitivity/PPV for ultra-low-dose CT at a 4 mm threshold was 0.91/0.98, respectively, with per-patient sensitivity/specificity/PPV/NPV/accuracy of 0.87/1.00/1.00/0.94/0.96. At a 4-mm threshold, per-stone sensitivity/PPV of the ultra-low-dose series for FBP, ASIR, and MBIR was 0.89/0.96, 0.91/0.98, and 0.93/1.00, respectively. Per-patient sensitivity/specificity/PPV/NPV/accuracy at the 4 mm threshold was 0.82/1.00/1.00/0.91/0.94 for FBP; 0.85/1.00/1.00/0.93/0.95 for ASIR; and 0.94/1.00/1.00/0.97/0.98 for MBIR. Sequential review of coronal images changed the final stone read in 13% of cases and improved diagnostic confidence in 49% of cases.
CONCLUSIONS: At a renal calculus size threshold of 4-mm, ultra-low-dose CT is accurate for detection when referenced against routine low-dose series with dose reduction to below the level of a typical 2-view KUB. Small differences were seen between reconstruction algorithms, with mild improvement with MBIR over FBP and ASIR. Coronal images improved both detection and diagnostic confidence over axial alone.
Written by:
Dustin Pooler B, Lubner MG, Kim DH, Ryckman EM, Sivalingam S, Tang J, Nakada SY, Chen GH, Pickhardt PJ. Are you the author?
Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI; Department of Urology, University of Wisconsin School of Medicine and Public Health, Madison, WI; Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI; Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI.
Reference: J Urol. 2014 May 21. pii: S0022-5347(14)03621-0.
doi: 10.1016/j.juro.2014.05.089
PubMed Abstract
PMID: 24859440
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