双层探测器光谱CT虚拟平扫代替真实平扫评估甲状腺乳头状癌的可行性研究

Feasibility study of dual-layer detector spectral CT virtual plain scan instead of real plain scan in the evaluation of thyroid papillary carcinoma

目的:评估双层探测器光谱CT虚拟平扫(VNC)图像代替真实平扫(TNC)图像评估甲状腺乳头状癌(PTC)患者的可行性。方法:回顾性分析86例PTC患者的双层探测器光谱CT图像。常规平扫获得TNC图像,后处理动脉期和静脉期增强CT图像获得动脉期和静脉期VNC(VNC-a和VNC-v)图像。测量3组图像(TNC、VNC-a、VNC-v)上平均衰减值、图像噪声、钙化的数量和长度,并计算辐射剂量。采用5分制评分主观评价图像质量。结果:胸锁乳突肌、颈椎骨松质、正常甲状腺、甲状腺结节VNC图像的平均衰减值均显著低于TNC图像(P<0.05),颈部脂肪VNC图像的平均衰减值均显著高于TNC图像(P<0.05)。颈椎骨松质、正常甲状腺、甲状腺结节TNC图像的信噪比(SNR)均显著高于VNC图像(P<0.05)。各组织TNC图像的对比噪声比(CNR)明显高于VNC图像(P<0.001)。与TNC图像相比,VNC图像检测到的钙化数量差异无统计学意义(P>0.05),但是钙化长度差异有统计学意义(P<0.05)。TNC图像质量主观评分高于VNC图像(P<0.001)。用VNC代替TNC,有效剂量减少了34.2%。结论:尽管可以降低受检者的辐射剂量,但考虑到不同的平均衰减值、SNR、CNR和钙化长度,我们认为VNC图像不能直接替代TNC图像用于评估PTC患者。

Objective:To evaluate the feasibility of virtual non-contrast scan(VNC)images using dual-layer detector spectral CT instead of true non-contrast scan(TNC)images in patients with papillary thyroid carcinoma(PTC).Methods:The images of 86 patients with PTC were analyzed retrospectively.TNC images were obtained by conventional plain scan,while arterial and venous VNC(VNC-a and VNC-v)images were generated from the arterial and venous phases of enhanced CT images by a post-processing algorithm,respectively.Average attenuation value,image noise,and amount and length of calcification were measured.And the radiation dose was calculated.A 5-point scale was used to evaluate the subjective score of image quality.Results:The average VNC attenuation values of sternocleidomastoid muscle,cervical cancellous bone,normal thyroid gland,and thyroid nodule were significantly lower than TNC(P<0.05),and the average VNC attenuation values of neck fat were significantly higher than TNC(P<0.05).The signal-to-noise ratio(SNR)of cervical cancellous bone,normal thyroid gland,and thyroid nodule in TNC image was significantly higher than that in VNC image(P<0.05).The contrast noise ratio(CNR)was significantly higher in TNC images than in VNC images(P<0.001).Compared with TNC images,VNC images showed no statistically significant difference in the amount of calcification detected(P>0.05),but significant difference in the length of calcification(P<0.05).The subjective scores of TNC images were higher than those of VNC image(P<0.001).Using VNC scan instead of TNC scan,the effective dose was reduced by 34.2%.Conclusion:Considering the different attenuation values,SNR,CNR,and calcification length,we conclude that although the radiation dose of subjects can be reduced,VNC images should not be used directly to replace TNC images of PTC patients.