模拟婴幼儿头颅70kV CT扫描的图像质量和辐射剂量

Image quality and radiation dose of simulating infant head CT scanning based on 70 kV

目的探讨模拟婴幼儿头颅70kVCT扫描条件下的图像质量和辐射剂量。方法选用CPT500模体，分别于70kV及120kV、150-500mAs条件下进行扫描，测量其低对比度模块中对比度为1．0％、直径为15mrrl的圆柱体的CNR和cTDIv01值，分析两者的相关性。由2名经验丰富的放射科医师对图像的低对比可探测能力（LCD）进行评分。对70kV、150～500mAs测得的每组图像的CNR和LCD评分与婴幼儿头颅常规扫描条件（120kV、200rflAs）图像的差异行统计学分析。结果当管电压为70kV及120kV时，图像CNR与cTDIvol呈线性正相关性（r=0．96、0．94，P〈0．001）；当管电流设置为150-400mAs时，70kV与常规扫描条件图像的cNR及LCD评分的差异均有统计学意义（P均〈0．05），但当管电流设置为450-500mAs时，差异均无统计学意义（P均〉0．05）。结论70kV、450-500mAs扫描条件可得到与传统的120kV、200mAsCT扫描相似的图像质量，前者辐射剂量明显降低，适用于婴幼儿头颅CT扫描。

Objective To explore the image quality and radiation dose of simulating infant head CT examination based on 70 kV. Methods The CPT500 phantom was scanned in 70 kV and 120 kV, 150--500 mAs, respectively, and the CNR and CT dose index volume （CTDIvol） value of low-contrast-module cylinder （contrast ratio 1.0%, diameter 15 mm） were measured. Two experienced radiologists evaluated the low contrast detection capabilities of image （LCD）. And the correlation between CNR and CTDIvol was analyzed. The differences of CNR and LCD between two conditions （70 kV, 150- 500 mAs and 120 kV, 200 mAs） was analyzed. Results There were positive correlation between CNR and CTDIvol in condition of 70 kV and 120 kV （r=0.96, 0.94, P〈0. 001）. The differences of CNR and LCD was statistically significant between the images obtained with 70 kV, 150-400 mAs and 120 kV, 200 mAs （all P〈0.05）. However in the condition of 70 kV, 450-500 mAs, there was no statistical difference was found （both P〈0.05）. Conclusion The equal image quality can be obtained in the CT scan condition of 70 kV, 450-500 mAs and 120 kV, 200 mAs, and the former with lower radiation dose is suitable for infant head CT examination.