Sheir Khaled Z, Mansour Osama, Madbouly Khaled, Elsobky Emad, Abdel-Khalek Mohamed
Urology Department, Urology and Nephrology Center, Mansoura University, Elgomhoria St., 35516, Mansoura, Egypt.
Urol Res. 2005 May;33(2):99-104. doi: 10.1007/s00240-004-0454-2. Epub 2005 Jan 6.
Various techniques for noncontrast spiral computerized tomography (NCCT) were utilized for the determination of the Hounsefield unit (HU) values of various types of urinary calculi with the aim of determining the best technique for distinguishing various stones compositions. A total of 130 urinary stones, obtained from patients who underwent open surgery, were scanned with a multidetector row scanner using 1.25 mm collimation at two energy levels of 100 and 120 kV at 240 mA. Two post-scanning protocols were used for the HU value assignment, tissue and bone windows, for both kV values. In both protocols, three transverse planes were defined in each stone, one near the top, one in the middle, and one near the bottom. Three regions of interest (ROI) were obtained in each plane. The absolute HU value was determined by three methods: the mean of the nine ROI, the mean of the central three ROI, and the central ROI in the middle plane. Determination of the stones' composition was performed using the absolute HU value measured at 120 kV, the dual CT values (HU values at 100 kV-HU values at 120 kV), and HU values/stone volume ratio (HU density). All stones were analyzed by x-ray diffraction to determine their chemical composition. After the exclusion of groups with few calculi, 47 pure stones [25 uric acid (UA), 15 calcium oxalate monohydrate (COM), seven struvite], and 60 mixed stones [15 COM 60-90%+hydroxyl apatite (HA), 14 COM 40-90%+UA, 21 UA+COM <40%, ten mixed struvite+COM+hydroxyl apatite] were included in the statistical analysis. From the least to the most dense, the pure stone types were UA, struvite, COM. Mixed UA+COM<40% calculi were less dense but insignificantly different from pure UA, while when the COM ratio was > or =40% their density became higher than and significantly different from pure UA, and less than but not significantly differentiated from pure COM. Mixed COM+HA were the most dense stones. Using the absolute HU values at 120 kV and HU density, we could distinguish, with statistical significance, all pure types from each other, pure UA from all mixed calculi except UA+COM <40%, pure COM from mixed UA+COM <40%, and pure struvite from all mixed stones except mixed struvite stones. Dual CT values were not as good as absolute HU values and HU density in the determination of stone composition. These results demonstrate that absolute HU values and HU density derived from CT scanning using a small collimation size could uncover statistically significant differences among all pure and most of the mixed urinary stones. This permits more accuracy in the prediction of stone composition. Moreover, this technique permits diagnostic conclusions on the basis of single CT evaluation.
采用多种非增强螺旋计算机断层扫描（NCCT）技术测定各类尿路结石的亨氏单位（HU）值，目的是确定区分不同结石成分的最佳技术。对130颗来自接受开放手术患者的尿路结石，使用多排探测器扫描仪，在1.25毫米准直、240毫安、100千伏和120千伏两个能量水平下进行扫描。针对两个千伏值，采用两种扫描后方案进行HU值赋值，即组织窗和骨窗。在两种方案中，每颗结石均定义三个横断面，一个靠近顶部，一个在中间，一个靠近底部。每个平面获取三个感兴趣区域（ROI）。通过三种方法确定绝对HU值：九个ROI的平均值、中间三个ROI的平均值以及中间平面的中央ROI。使用在120千伏下测量的绝对HU值、双能CT值（100千伏时的HU值 - 120千伏时的HU值）和HU值/结石体积比（HU密度）来确定结石成分。所有结石均通过X射线衍射分析以确定其化学成分。在排除结石数量较少的组后，47颗纯结石[25颗尿酸（UA）结石、15颗一水草酸钙（COM）结石、7颗磷酸镁铵结石]和60颗混合结石[15颗COM占60 - 90% + 羟基磷灰石（HA）结石、14颗COM占40 - 90% + UA结石、21颗UA + COM <40%结石、10颗混合磷酸镁铵 + COM + 羟基磷灰石结石]纳入统计分析。从密度最低到最高，纯结石类型依次为UA、磷酸镁铵、COM。UA + COM <40%的混合结石密度较低，但与纯UA结石差异不显著，而当COM比例≥40%时，其密度高于纯UA结石且差异显著，低于纯COM结石但差异不显著。COM + HA混合结石是密度最高的结石。使用120千伏时的绝对HU值和HU密度，我们能够在统计学上显著区分所有纯结石类型，区分纯UA结石与除UA + COM <40%之外的所有混合结石，区分纯COM结石与UA + COM <40%混合结石，区分纯磷酸镁铵结石与除混合磷酸镁铵结石之外的所有混合结石。在确定结石成分方面，双能CT值不如绝对HU值和HU密度。这些结果表明，使用小准直尺寸的CT扫描得出的绝对HU值和HU密度能够揭示所有纯结石以及大多数混合尿路结石之间在统计学上的显著差异。这使得在预测结石成分时更加准确。此外，该技术允许基于单次CT评估得出诊断结论。
