Stadler Alfred, Schima Wolfgang, Prager Gerhard, Homolka Peter, Heinz Gertraud, Saini Sanjay, Eisenhuber Edith, Niederle Bruno
Department of Radiology, University of Vienna, Waehringer Guertel 18-20, Vienna A-1090, Austria.
AJR Am J Roentgenol. 2004 Mar;182(3):671-5. doi: 10.2214/ajr.182.3.1820671.
Many studies have suggested that Hounsfield measurements on unenhanced CT can reliably differentiate adrenal adenomas from nonadenomas using a scanner-independent threshold level. The purpose of this study was to determine whether establishment of a scanner-independent threshold for differentiation of adenomas from nonadenomas is technically feasible.
Surgically resected adrenal tumor specimens (total, seven; adenomas, three; nonadenomas, four; size range, 17-76 mm), were placed in an anthropomorphic phantom. Lesion specimens were scanned with one MDCT and two single-detector scanners. Scanning protocols for all three scanners included variations in kilovoltage (140, 120, and 80 [Somatom Plus 4, Somatom VolumeZoom] or 100 [Tomoscan AV] kVp) and slice thickness. Hounsfield measurements were performed on exactly matched slices using regions of interest of a constant size.
The difference in lesion Hounsfield measurements among scanning protocols with 140, 120, and 100/80 kVp was up to 6.2 H for the adenoma group and up to 3.8 H for the nonadenoma group. The comparison of the Tomoscan AV and the Somatom Plus 4 scanners showed a mean difference of 2.6 H at 120 kVp and of 4.6 H at 140 kVp. The differences between the Tomoscan AV and Somatom VolumeZoom scanners were 1.7 and 3.6 H for 120 and 140 kVp, respectively. Between the two Somatom scanners, the divergence was 2.9 and 3.3 H for the two kilovoltage settings. Differentiation between adenomas and nonadenomas was better at lower kilovoltage. Slice thickness did not affect the CT density measurements significantly.
Significant differences in CT density measurements of adrenal tumors may occur when different CT scanners or imaging protocols are used. The dependence of measurements on scanner type and scanning technique makes the recommendation of a universal, scanner- and protocol-independent threshold problematic.
许多研究表明，在未增强CT上进行的亨氏测量可以使用与扫描仪无关的阈值水平可靠地鉴别肾上腺腺瘤与非腺瘤。本研究的目的是确定建立与扫描仪无关的鉴别腺瘤与非腺瘤的阈值在技术上是否可行。
将手术切除的肾上腺肿瘤标本（共7个；腺瘤3个；非腺瘤4个；大小范围为17 - 76 mm）置于仿真人体模型中。病变标本用一台多层螺旋CT（MDCT）和两台单探测器扫描仪进行扫描。所有三台扫描仪的扫描方案包括千伏值（140、120和80 [Somatom Plus 4、Somatom VolumeZoom] 或100 [Tomoscan AV] kVp）和层厚的变化。使用恒定大小的感兴趣区在完全匹配的层面上进行亨氏测量。
对于腺瘤组，140、120和100/80 kVp扫描方案之间病变亨氏测量的差异高达6.2 H，对于非腺瘤组高达3.8 H。Tomoscan AV扫描仪和Somatom Plus 4扫描仪在120 kVp时的平均差异为2.6 H，在140 kVp时为4.6 H。Tomoscan AV扫描仪和Somatom VolumeZoom扫描仪在120和140 kVp时的差异分别为1.7和3.6 H。在两台Somatom扫描仪之间，两种千伏设置下的差异分别为2.9和3.3 H。在较低千伏时，腺瘤与非腺瘤之间的鉴别更好。层厚对CT密度测量没有显著影响。
使用不同的CT扫描仪或成像方案时，肾上腺肿瘤的CT密度测量可能会出现显著差异。测量结果对扫描仪类型和扫描技术的依赖性使得推荐一个通用的、与扫描仪和方案无关的阈值存在问题。
