Background A definite diagnosis of gout requires demonstration of monosodium urate crystals in synovial fluid or in tophi, which in clinical practice today seldom is done. Dual energy CT (DECT) has repeatedly been shown to be able to detect monosodium urate crystals in tissues, hence being an alternative method to synovial fluid microscopy. The vast majority of these studies were performed with CT scanners with two X-ray tubes. In the present study we aim to investigate if and at what locations DECT with rapid kilovoltage-switching source with gemstone scintillator detector (GSI) can identify MSU crystals in patients with clinically diagnosed gout. We also performed a reliability study between two independent readings. Methods Patients with new or established gout who had been examined with DECT GSI scanning of the feet at Sahlgrenska University Hospital, Mölndal between 2015 and 2018 were identified. Their medical records were sought for gout disease characteristics using a structured protocol. Urate deposits in MTP1, MTP 2-5, ankle/midfoot joints and tendons were scored semiquantatively in both feet and presence of artifacts in nail and skin as well as beam hardening and noise were recorded. Two radiologists performed two combined readings and scoring of the images, thus consensus was reached over the scoring at each occasion (Espeland et al., BMC Med Imaging. 2013;13:4). The two readings were compared with kappa statistics. Results DECT GSI could identify urate deposits in the feet of all 55 participants with gout. Deposits were identified in the MTP-joints of all subjects but were also present in ankle/midfoot joints and tendons in 96 and 75% respectively. Deposition of urate was predicted by longer disease duration (Spearman's Rho 0.64, p < .0001) and presence of tophi (p = 0.0005). Artifacts were common and mostly found in the nails (73%), a minority displayed skin artifacts (31%) while beam hardening and noise was rare. The agreement between the two readings was good (Κ = 0.66, 95% CI = 0.61-0.71). Conclusion The validity of DECT GSI in gout is supported by the identification of urate in all patients with clinical gout and the good correlations with clinical characteristics. The occurrence of artifacts was relatively low with expected locations.

中文翻译：

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带有宝石闪烁体探测器的快速千伏开关源在痛风中的双能 CT 发现。

背景 痛风的明确诊断需要在滑液或痛风石中发现单钠尿酸盐晶体，这在当今的临床实践中很少这样做。双能 CT (DECT) 已多次被证明能够检测组织中的单钠尿酸盐晶体，因此是滑液显微镜检查的替代方法。这些研究中的绝大多数是使用带有两个 X 射线管的 CT 扫描仪进行的。在本研究中，我们旨在调查是否以及在哪些位置使用带有宝石闪烁体探测器 (GSI) 的快速千伏开关源的 DECT 可以识别临床诊断为痛风患者的 MSU 晶体。我们还在两个独立读数之间进行了可靠性研究。方法 确定 2015 年至 2018 年间在莫尔达尔萨尔格伦斯卡大学医院接受 DECT GSI 足部扫描检查的新痛风或已确诊痛风患者。使用结构化协议寻找他们的医疗记录以了解痛风疾病的特征。MTP1、MTP 2-5、踝/中足关节和肌腱中的尿酸盐沉积物在双脚中进行半定量评分，并记录指甲和皮肤中存在伪影以及光束硬化和噪音。两名放射科医生对图像进行了两次综合读数和评分，因此在每次评分方面达成了共识（Espeland 等人，BMC Med Imaging. 2013;13:4）。将这两个读数与 kappa 统计数据进行比较。结果 DECT GSI 可以识别所有 55 名痛风患者脚部的尿酸盐沉积物。在所有受试者的 MTP 关节中都发现了沉积物，但在踝/中足关节和肌腱中也存在沉积物，分别为 96% 和 75%。更长的病程（Spearman's Rho 0.64，p < .0001）和痛风石的存在（p = 0.0005）可以预测尿酸盐的沉积。伪影很常见，主要在指甲中发现（73%），少数显示皮肤伪影（31%），而光束硬化和噪音很少见。两个读数之间的一致性很好（Κ = 0.66, 95% CI = 0.61-0.71）。结论 DECT GSI 在痛风中的有效性得到所有临床痛风患者尿酸盐的鉴定以及与临床特征的良好相关性的支持。预期位置的伪影发生率相对较低。更长的病程（Spearman's Rho 0.64，p < .0001）和痛风石的存在（p = 0.0005）可以预测尿酸盐的沉积。伪影很常见，主要在指甲中发现（73%），少数显示皮肤伪影（31%），而光束硬化和噪音很少见。两个读数之间的一致性很好（Κ = 0.66, 95% CI = 0.61-0.71）。结论 DECT GSI 在痛风中的有效性得到所有临床痛风患者尿酸盐的鉴定以及与临床特征的良好相关性的支持。预期位置的伪影发生率相对较低。更长的病程（Spearman's Rho 0.64，p < .0001）和痛风石的存在（p = 0.0005）可以预测尿酸盐的沉积。伪影很常见，主要在指甲中发现（73%），少数显示皮肤伪影（31%），而光束硬化和噪音很少见。两个读数之间的一致性很好（Κ = 0.66, 95% CI = 0.61-0.71）。结论 DECT GSI 在痛风中的有效性得到所有临床痛风患者尿酸盐的鉴定以及与临床特征的良好相关性的支持。预期位置的伪影发生率相对较低。少数人显示皮肤伪影（31%），而光束硬化和噪声很少见。两个读数之间的一致性很好（Κ = 0.66, 95% CI = 0.61-0.71）。结论 DECT GSI 在痛风中的有效性得到所有临床痛风患者尿酸盐的鉴定以及与临床特征的良好相关性的支持。预期位置的伪影发生率相对较低。少数人显示皮肤伪影（31%），而光束硬化和噪声很少见。两个读数之间的一致性很好（Κ = 0.66, 95% CI = 0.61-0.71）。结论 DECT GSI 在痛风中的有效性得到所有临床痛风患者尿酸盐的鉴定以及与临床特征的良好相关性的支持。预期位置的伪影发生率相对较低。