Noninvasive Differentiation of Uric Acid versus Non–Uric Acid Kidney Stones Using Dual-Energy CT

Abstract

Rationale and Objectives-To determine the accuracy and sensitivity for dual-energy computed tomography (DECT) discrimination of uric acid (UA) stones from other (non-UA) renal stones in a commercially implemented product.Materials and Methods-Forty human renal stones comprising uric acid (n = 16), hydroxyapatite (n = 8), calcium ox-alate (n = 8), and cystine (n = 8) were inserted in four porcine kidneys (10 each) and placed inside a 32-cm water tank anterior to a cadaver spine. Spiral dual-energy scans were obtained on a dual-source, 64-slice computed tomography (CT) system using a clinical protocol and automatic exposure control. Scanning was performed at two different collimations (0.6 mm and 1.2 mm) and within three phantom sizes (medium, large, and extra large) resulting in a total of six image datasets. These datasets were analyzed using the dual-energy software tool available on the CT system for both accuracy (number of stones correctly classified as either UA or non-UA) and sensitivity (for UA stones). Stone characterization was correlated with micro-CT.Results-For the medium and large phantom sizes, the DECT technique demonstrated 100% accuracy (40/40), regardless of collimation. For the extra large phantom size and the 0.6-mm collimation (resulting in the noisiest dataset), three (two cystine and one small UA) stones could not be classified (93% accuracy and 94% sensitivity). For the extra large phantom size and the 1.2-mm collimation, the dual-energy tool failed to identify two small UA stones (95% accuracy and 88% sensitivity). Conclusions-In an anthropomorphic phantom model, dual-energy CT can accurately discriminate uric acid stones from other stone types. KeywordsKidney stones; renal calculi; dual-energy computed tomography; uric acid; urolithiasis Symptomatic urinary stone disease affects approximately 900,000 persons in the United States each year, resulting in annual medical cost of $5.3 billion. Nephrolithiasis has traditionally been evaluated using plain film radiographic techniques with or without tomography or administration of intravenous contrast for excretory urography. Over recent years, however, computed tomography (CT) has supplanted these traditional techniques because of increased sensitivity, speed, and the lack of intravenous contrast (1 Although state-of-the-art CT provides accurate submillimeter details of the size and location of renal stones (4,5), current routine clinical image analysis does not differentiate stone composition. This is particularly important in the case of uric acid (UA) stones (~10% of cases), because urinary alkalinization can be prescribed to dissolve UA stones and could thereby be initiated at presentation rather than following lengthy metabolic workup. Therefore simple and reliable differentiation of UA versus non-UA stone composition could potentially allow patients with UA stones to avoid invasive interventional urinary procedures for stone removal or external shock wave lithotripsy, both of which are expensive and might result in renal hemorrh...

The potential of dual-energy computed tomography for quantitative decomposition of soft tissues to water, protein and lipid in brachytherapy

“…A decomposition to an average soft tissue, bone and iodine, or fat, soft tissue and iodine can be used for contrast agent detection (Petersilka et al 2008). Other suitable choices are calcium oxalate, cystine, and uric acid for the classification of kidney stones and gallstones (Graser et al 2008, Primak et al 2007, Scheffel et al 2007. Liu et al (2009) investigated the three-material decomposition method in phantom studies to determine the concentrations of hydroxyapatite in mixtures of water, hydroxyapatite and iron nitrate.…”

Pilot multi-reader study demonstrating potential for dose reduction in dual energy hepatic CT using non-linear blending of mixed kV image datasets

“…Dual energy CT was originally designed for classification of the elementary chemical composition of tissues, which is of clinical value in applications such as automated bone removal [1], kidney stone characterization [2], gout detection [3], pulmonary embolism detection [4], endoleak detection [5] and iodine removal (or "virtual non-contrast") [1]. Relatively little attention has been paid to the potential for enhanced detection of hypervascular pathologies at dual energy CT [6], despite the predicted advantage of low kV imaging in phantom models [7,8].…”

Bilgisayarlı Tomografi İle Üriner Sistem Taşlarının Yapısı Tahmin Edilebilir Mi?

“…Dual enerji BT, özellikle ürik asid içeren taşlarla ürik asit içermeyenleri yüksek doğruluk oranlarıyla gösterebilmek-tedir (35,36). Stolzmann ve ark.…”