From the *Department of Diagnostic Radiology, Kitasato University School of Medicine; and †Department of Radiology, Kitasato University Hospital, Sagamihara, Japan.
Clin Nucl Med. 2016 Jun;41(6):434-41. doi: 10.1097/RLU.0000000000001146.
Renal depths predicted using predefined formulas are commonly used for camera-based evaluation of renal function. We investigated the feasibility and utility of renal depth measurement using ultralow-dose CT images acquired in conjunction with dynamic renal scintigraphy.
Dynamic renal scintigraphy with Tc-MAG3 was performed in 117 patients (225 kidneys) using a SPECT/CT scanner, and ultralow-dose CT (estimated effective dose of 0.17 mSv) was performed during free breathing immediately before tracer injection. The clarity of the renal contour on the CT images was evaluated visually. The renal depths were measured by 2 methods and compared with depths predicted by 2 previously reported methods. The accuracy of camera-based clearance using predicted and measured depths was evaluated using a single-sample method as a standard.
The clarity of the renal contour was poor in 18 of 225 kidneys, and 12 of 117 patients were considered ineligible for depth measurement. The measurement for eligible patients showed excellent intraobserver and interobserver repeatabilities. Although mean depths were similar among the 2 CT measurement methods and 2 prediction methods, absolute differences of more than 1 cm were observed in approximately 20% of kidneys between CT measurement and prediction. CT measurement of renal depth failed to improve the accuracy of camera-based clearance evaluation.
Ultralow-dose CT allowed measurement of renal depth in most patients. Substantial differences in renal depth between prediction and CT measurement indicated potential usefulness of CT measurement, although no actual improvement in the accuracy of clearance estimation was demonstrated in this study.
使用预定义公式预测的肾脏深度常用于基于相机的肾功能评估。我们研究了使用与动态肾闪烁扫描相结合获得的超低剂量 CT 图像测量肾脏深度的可行性和实用性。
在 SPECT/CT 扫描仪上对 117 例患者（225 个肾脏）进行 Tc-MAG3 动态肾闪烁扫描，并在示踪剂注射前立即在自由呼吸时进行超低剂量 CT（估计有效剂量为 0.17 mSv）。通过视觉评估 CT 图像上肾脏轮廓的清晰度。通过 2 种方法测量肾脏深度，并与 2 种先前报道的方法预测的深度进行比较。使用单样本方法作为标准评估基于相机的使用预测和测量深度的清除率的准确性。
225 个肾脏中有 18 个肾脏的肾脏轮廓清晰度较差，117 例患者中有 12 例被认为不适合进行深度测量。对符合条件的患者进行测量，显示出极好的观察者内和观察者间的可重复性。虽然两种 CT 测量方法和两种预测方法的平均深度相似，但在大约 20%的肾脏中，CT 测量和预测之间的绝对差异超过 1 厘米。CT 测量肾脏深度未能提高基于相机的清除率评估的准确性。
超低剂量 CT 允许在大多数患者中测量肾脏深度。预测和 CT 测量之间的肾脏深度存在显著差异表明 CT 测量具有潜在的实用性，尽管在本研究中未证明清除率估计准确性的实际改善。
