![]() This has resulted in a general lack of trust in US by the urology community as a primary modality for imaging renal stones, as accurate detection and sizing are important for surgical treatment planning and monitoring stone burden. 2–6 Anecdotally, many urologists feel US reports a significantly larger size than CT. 2–6 The accuracy of US for sizing stones compared with CT has also been shown to differ widely, particularly with size and depth. 1 The sensitivity of US for diagnosing renal stones compared with CT varies widely, from 24% to 70%. ![]() U ltrasound (US) has proven effective in the diagnosis of symptomatic renal and ureteral stones in the emergency department setting however, US is limited for treatment planning by low sensitivity, user dependence, and inaccurate stone sizing. Stones that do not shadow are most likely <5 mm and small enough to pass spontaneously. With S-mode, sizing of the stone itself and the posterior acoustic shadow were similarly accurate. S-mode stone and shadow measurements differed from CT by 1.6 ± 1.0 mm and 0.8 ± 0.6 mm, respectively, compared with 2.0 ± 1.5 mm and 1.6 ± 1.0 mm for the clinical system.Ĭonclusions: S-mode offers improved visualization and sizing of renal stones. S-mode visualized 78% of stones, versus 61% for the clinical system. ![]() A posterior acoustic shadow was present in 89% of stones over 5 mm versus 53% of stones under 5 mm. Seventy-three percent of the stone measurements and 85% of the shadow measurements were within 2 mm of the size on CT. Results: Overall, 84% of stones identified on CT were detected on S-mode and 66% of these shadowed. Stone and shadow width were compared with a recent CT scan and, in 5 subjects with 18 stones, S-mode was compared with a clinical US system. S-mode is gray-scale US adjusted to enhanced stone contrast and resolution by minimizing compression and averaging, and increasing line density and frequency. Materials and Methods: Thirty-four subjects with 115 renal stones were prospectively recruited and scanned with S-mode on a research US system. Purpose: The purpose of this study was to measure the accuracy of stone-specific algorithms (S-mode) and the posterior acoustic shadow for determining kidney stone size with ultrasound (US) in vivo.
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