Department of Urology, Tanta University, Tanta, Egypt.
J Urol. 2009 Jul;182(1):343-7. doi: 10.1016/j.juro.2009.02.111. Epub 2009 May 17.
We describe an objective method to evaluate kidney stone radiopacity for use in selection of cases suitable for ESWL.
We recruited 76 adult patients with a solitary 1 to 2 cm renal pelvic stone. All patients underwent routine plain x-ray of the urinary tract but an aluminum step wedge (Gammex) was adapted to the cassette before x-ray exposure. This x-ray was then digitized and analyzed by histogram to calculate the gray level of the stone and of each step of the aluminum step wedge. This allowed radiographic stone density to be expressed in mm aluminum equivalent. All patients also underwent abdominopelvic computerized tomography and then ESWL was started.
Stone density on plain x-ray was 1.83 to 5.93 mm aluminum equivalent. There was a positive correlation between these values and stone attenuation values on computerized tomography (r(2) 0.83, p <0.005). The 12 patients in whom ESWL failed were found to have stones of significantly higher density than stones in patients with complete stone fragmentation (mean +/- SD 4.8 +/- 0.74 vs 3.35 +/- 0.88 mm aluminum equivalent, p <0.005). There was also a positive correlation between stone radiopacity in mm aluminum equivalent and the total number of shock waves required to achieve complete fragmentation (r(2) 0.66, p <0.005).
The aluminum step wedge with plain x-ray of the urinary tract provides a good reference for objectively assessing the radiopacity of renal calculi.
我们描述了一种客观的方法来评估肾结石的放射密度，用于选择适合 ESWL 的病例。
我们招募了 76 名患有单一 1 至 2 厘米肾盂结石的成年患者。所有患者均接受常规尿路平片检查，但在 X 射线曝光前，将铝阶跃楔形物（Gammex）适配于暗盒。然后对该 X 射线进行数字化并通过直方图进行分析，以计算结石和铝阶跃楔形物每个台阶的灰度级。这使得结石的放射密度可以用毫米铝当量表示。所有患者还接受了腹部计算机断层扫描，然后开始进行 ESWL。
平片上的结石密度为 1.83 至 5.93 毫米铝当量。这些值与计算机断层扫描上的结石衰减值之间存在正相关（r² 0.83，p <0.005）。12 例 ESWL 失败的患者的结石密度明显高于结石完全碎裂的患者（平均值 ± 标准差 4.8 ± 0.74 对 3.35 ± 0.88 毫米铝当量，p <0.005）。结石放射密度与实现完全碎裂所需的冲击波总数之间也存在正相关（r² 0.66，p <0.005）。
尿路平片上的铝阶跃楔形物为客观评估肾结石的放射密度提供了良好的参考。
