脊柱定量CT重建参数对骨密度测量的影响

The Effect of Reconstruction Parameters of Spine QCT on Bone Mineral Density

目的优化CT扫描协议,使定量CT(QCT)骨密度(BMD)测量值更精确,辐射剂量更低。材料与方法采用欧洲脊柱体模(ESP)与QCT校准体模一起进行不同毫安秒的CT螺旋扫描。扫描参数:管电压120kV,管电流50～350mA,层厚1×16mm,床高73cm,扫描范围10cm,视野(FOV)40c,重建矩阵:512×512,重建间距0.8mm。记录CT扫描机上的辐射剂量乘积(DLP)。用标准算法(FC03)和骨算法(FC30)分两组重建欧洲脊柱体模影像,并进行BMD测量。结果 FC03组平均BMD值与毫安秒正相关(r=0.401,P<0.05);FC30组平均BMD值与毫安秒无相关性(r=0.216,P>0.05)。两组平均毫安秒与DLP呈正相关(r=0.999,P<0.01)。FC03组与FC30组平均BMD差异有统计学意义(t=-13.089,P<0.01)。FC03组与欧洲脊柱体模标准平均BMD差异有统计学意义(t=-19.220,P<0.01);FC30组与欧洲脊柱体模标准平均BMD差异无统计学意义(t=0.506,P=0.616)。结论 QCT扫描重建参数对BMD值有影响。骨算法重建影像除去了影响BMD测量的因素,使测量准确率更高。在制订扫描协议时应充分考虑重建算法对骨密度测量的影响,并使扫描参数保持恒定。

Purpose To optimize the scan protocol for accurate quantitative computed tomography （QCT） bone mineral density （BMD） measurements with low radiation dose. Mateiral and Methods European Spine Phantom （ESP） and QCT calibration Phantom （Image Analysis, Inc, US, G2208） were scanned with a Toshiba 16-sclice CT scanner. Tube voltage and tube current were 120KV and 50mA to 350mA. Slice thickness was 1× 16mm with table height of 73cm. Scan range was 10cm. FOV was 40cm. Reconstruction matrix was 512× 512 and reconstruction interval was 0.8cm. Dose length product （DLP） was recorded. Images of ESP were reconstructed using standard algorithm （FC 03） and bone algorithm （FC 30）. Reconstructed data were transferred to BMD workstation. BMD was measured using QCT PROTM 3D spine BMD application module （version 4.0, mindways software Inc）. Statistical analysis was performed using SPSS 15.0. Results The correlation coefficient of BMD with mAs of FC03 and FC 30 were 0.401 （P 〈 0.05） and 0.216 （P 〉 0.05）, respectively. The correlation coefficient of mAs with DLP is 0.999 （P 〈 0.01）. The difference of BMD between FC03 and FC30 was statistically significant （t=-13.089, P〈 0.01）. There were statistically significant differences between the BMD of FC 03 and standard value ofESP （t= -19.220, P 〈 0.01）. The BMD of FC 30 and standard value of ESP were not statistically different （t =0.506, P =0.616）. Conclusion Reconstruction parameters of QCT affect the measured value of BMD. Images reconstructed using bone algorithm （FC 30） exclude interfering factors and increase the accuracy of the BMD measurement. Reconstruction parameters should be taken into account when the scan protocols were formulated.