SPECT/CT直接测量肾脏深度在肾小球滤过率测定中的应用

目的 探讨在以SPECT/CT测定GFR时用CT直接测量肾脏深度代替传统的Tonnesen公式法的必要性和可行性.方法 49例患者在接受肾动态显像的同时进行腹部CT平扫,测量两侧肾的深度.将所测值与传统的Tonnesen公式值和SPECT侧位平面图像测量值进行比较,然后将CT和SPECT测得的肾脏深度数据代入到Gates法GFR测量软件中,观察肾脏深度改变对GFR测定值的影响.采用配对t检验对Tonnesen公式法和SPECT测量法测得的肾脏深度值及各自深度值对应的GFR与CT法测得的相关数据间差异进行比较,对Tonnesen公式误差、SPECT测量误差与肾脏深度的关系采用直线相关分析.结果 CT测得的肾脏深度分别为右肾(7.04±1.15) cm,左肾(7.18±1.15) cm.与CT测量值相比,Tonnesen公式法低估了肾脏深度[右肾:(5.77±0.90) cm,t=- 11.50,P＜0.01;左肾:(5.74±0.88) cm,t=12.20,P＜0.01],而SPECT测量值则高估了肾脏深度[右肾:(7.40±1.15) cm,t=5.19,P＜0.01;左肾:(7.49±1.19) cm,=5.14,P＜0.01].Tonnesen公式法误差与肾脏深度呈正相关(右肾:r =0.62,P＜0.01;左肾:r=0.73,P＜0.01),而SPECT测量误差与肾脏深度不相关(右肾r =0.26,P＞0.05;左肾r=0.38,P＜0.01).Tonnesen公式法得到的两侧肾脏深度差为0.03 ～0.05 cm,而SPECT和CT得到两侧肾脏深度差分别为0.54±0.33(0.01～1.28) cm和0.62±0.45(0.01～1.60) cm.Gates法采用Tonnesen公式肾脏深度低估了GFR,与CT所测肾脏深度对应的GFR相比,误差百分比分别为右肾(-20.92±11.28)％(t=-6.99,P＜0.01),左肾(-23.71±7.71)％(t=-8.73,P＜0.01);采用SPECT测量则高估了GFR,对应误差百分比为右肾(5.23±9.64)％(t=2.72,P＜0.01),左肾(8.93±9.29)％(=5.21,P＜0.01).结论 采用SPECT/CT的CT功能精确测量两侧肾脏深度,有助于提高Gates法GFR测定的准确性.

Application of renal depth by CT for the measurement of GFR using SPECT/CT

Objective To investigate the necessity and feasibility of renal depth measured by CT for the measurement of GFR with SPECT/CT. Methods CT and lateral planar imaging of SPECT along with dynamic 99Tc=-DTPA renal scintigraphy （DRS） was performed in 49 patients. The renal depth esti- mated by Tonnesen formula and SPECT was compared with that measured by CT using paired t-test. GFR was recalculated by the Gates method using the renal depth measured by CT, Tonnesen formula and SPECT. Line- ar correlation analysis was used between the renal depth by CT and measurement error caused by Tonnesen formula and lateral planar imaging of SPECT. Paired t-test was also performed with software SPSS 15.0. Re- suits Compared with CT, the renal depth was substantially underestimated by Tonnesen formula （right kid- ney： （5.77±0.90） cm, t= -11.50, P〈0.01; left kidney： （5.74 ±0.88） cm, t =12.20, P〈0.01）, which resulted in the underestimation of GFR （right kidney ： （ - 20.92 ± 11.28） %, t = - 6.99, P 〈 0.01 ; left kidney： （ -23.71 ± 7.71 ） %, t = - 8.73, P 〈 0.01 ） ; while, it was overestimated by SPECT （ right kidney： （7.40±1.15） cm, t=5.19, P〈0.01; left kidney （7.49±1.19） cm, t=5.14, P〈0.01）, which resulted in the overestimation of GFR （ right kidney ： （5.23± 9.64） %, t = 2.72, P 〈 0.01 ; left kidney ： （8.93 ± 9.29） %, t = 5.21, P 〈 0.01 ）. The error for the calculation of renal depth by Tonnesen formula was positively correlated with the true value （right kidney r = 0.62, P 〈 0.01 ; left kidney r = 0.73, P 〈 0.01 ）. However, there was no correlation between the error of the renal depth measured by SPECT and the true value （right kidney： r = 0.26, P 〉 0.05; left kidney： r = 0.38, P 〈 0.01 ）. Conclusion SPECT/CT can improve the accuracy of GFR measurement by the Gates method using renal depth measured by CT.