64层CT容积与常规高分辨率CT图像质量的比较

Comparison of the image quality between volumetric and conventional high-resolution CT with 64-slice row CT

目的比较容积高分辨率CT（VHRCT）与常规高分辨率CT（CHRCT）的图像质量，探讨VHRCT的可行性。方法对Catphan412模具行VHRCT及CHRCT扫描，测量和记录图像的空间分辨率、噪声及放射剂量并进行比较；对32例患者行VHRCT及CHRCT检查，对图像质量进行评分并比较。模具部分采用配对t检验比较噪声的差异；临床部分采用Wilcoxon配对符号秩和检验比较图像质量的差异。结果模具研究中，VHRCT横断面图像的空间分辨率与CHRCT相同，均为11LP／cm，其z轴分辨率为12LP／cm。剂量相近时，VHRCT的噪声为（69．18±2．77）HU，大于CHRCT的噪声（54．62±2．12）HU，（t=-15．929，P〈0．01）；噪声相近时，VHRCT的剂量较CHRCT增加19．09mGy。临床研究中，VHRCT与CHRCT横断面图像的质量评分分别为3．22与3．24，差异无统计学意义（Z=-0．319，P〉0．05），VHRCT与CHRCT冠状面重建图像的质量评分分别为3．05与1．88，差异有统计学意义（Z=-5．088，P〈0．01）。结论对于64层CT，VHRCT的横断面图像质量接近CHRCT，多平面重组图像具有高分辨率可广泛应用，其扫描剂量尚有待优化。

Objective To compare the image quality between volumetric high-resolution CT （VHRCT） and conventional high-resolution CT （CHRCT）, and investigate the feasibility of VHRCT. Methods Catphan 412 phantom was scanned with protocols of CHRCT and VHRCT on a set of GE Lightspeed VCT. The spatial-resolution （LP/cm）, noise （standard deviation in an ROI） and radiation dose （CTDI） were recorded for each CT scan. Difference of noise between CHRCT and VHRCT were evaluated by paired t test. In clinical study, 32 patients were scanned with VHRCT and CHRCT protocols. The image quality of CHRCT and VHRCT was rated and compared. The quality difference between CHRCT and VHRCT was assessed by Wilcoxon paired signed rank sum test. Results In phantom study, the in-plane spatial-resolution of both VHRCT and CHRCT was 11 LP/cm for axial images and 12 LP/cm for coronal reformatted images. The noise of VHRCT and CHRCT was （69. 18 ± 2. 77 ）HU and （54. 62 ±2. 12 ） HU respectively （ t = - 15. 929, P 〈 0.01 ） at the same dose level. The radiation dose of VHRCT was 19.09 mGy higher than CHRCT at the same noise level. In clinical study, the quality assessment scores of VHRCT axial images and CHRCT axial images were 3.22 and 3.24 respectively, with no significant difference（ Z = -0. 319, P 〉 0. 05 ）. The quality assessment scores of VHRCT coronal reformatted images and CHRCT coronal reformatted images were 3.05 and 1.88 respectively with significant difference （ Z = - 5. 088,P 〈 0.01 ）. Conclusion The image quality of VHRCT cross-sectional image is similar to that of CHRCT. Muhiplanar images with high resolution of VHRCT are recommended. The radiation dose of VHRCT remains to be optimized.