能谱CT虚拟平扫替代常规平扫评估甲状腺结节的可行性研究

摘要

目的探讨能谱CT碘抑制（MSI）成像作为虚拟平扫（VNC）替代真实平扫（TNC）对甲状腺结节进行评估的可行性。方法回顾性分析2014年2月—10月于我院行常规平扫、能谱成像模式增强扫描的72例甲状腺疾病病人影像资料，采用配对t检验和Wilcoxon符号秩和检验比较TNC与VNC影像上不同组织CT值、客观影像质量、主观影像质量评分、诊断钙化能力及辐射剂量的差异。结果①在TNC和VNC两种影像上，甲状腺结节病灶、正常甲状腺、颈内动脉的CT值差异均有统计学意义（P＜0.05），但除正常甲状腺腺体外，其他部位CT值差异均不大（＜4 HU）。两种影像项部脂肪CT值的差异无统计学意义（P＞0.05）。 VNC影像噪声高于TNC影像，信噪比（SNR）及对比噪声比（CNR）均低于TNC影像（P＜0.05）。②TNC与VNC主观影像质量评分中位数均为4.0分，VNC的主观评分略低于TNC，两者评分差异无统计学意义（P＞0.05）。③TNC检出钙化24例，VNC检出22例。 TNC与VNC对钙化检出数目的差异无统计学意义（P＞0.05）；TNC测得的钙化长径值较VNC大（P＜0.05）。④单独能谱增强扫描的剂量长度乘积（DLP）和有效辐射剂量（ED）值明显小于TNC加增强扫描（P<0.05），与常规平扫加增强扫描比较，单独能谱增强扫描的有效辐射剂量可降低48.76%。结论在甲状腺CT扫描中，VNC成像对甲状腺结节的诊断具有替代TNC成像的潜在能力。%Objective The study aimed to determine whether virtual non-contrast (VNC) images derived from spectral CT can replace true non-contrast (TNC) images for thyroid nodules evaluation. Methods Retrospectively analyzed images of 72 patients with thyroid diseases who had undergone traditional plain CT scan and enhanced spectral CT scan in our hospital during Feb.-Oct. 2014. The CT values of different tissues, subjective image quality, objective image quality, diagnostic ability of calcifications, and radiation dose were compared between TNC and VNC images with paired t test and Wilcoxon signed rank test. Results 1. Significant differences were observed in CT values of thyroid nodules and other tissues except fat (P<0.05) between TNC and VNC images. Except of normal thyroid tissues, all the CT value differences were less than 4 HU. There was no significant difference in fat CT values between TNC and VNC images (P>0.05). The noise of VNC images was higher than that of TNC, and the SNR, CNR of VNC images were lower than those of TNC (P<0.05). 2. The median scores of objective image quality of TNC and VNC images both were 4.0, and the score of VNC images was lower than that of TNC, but the difference was not significant (P>0.05). 3.TNC images presented calcification in 24 cases, whereas VNC images in 22 cases. No significant difference was found in calcification number between TNC and VNC images (P>0.05), however the long-axis diameters of the largest calcifications were smaller on VNC images than that on TNC images (P<0.05). 4. The values of dose length product and effective dose of the enhanced spectral CT were much lower than those of TNC plus enhanced CT scan, and the differences were significant(P<0.05). Compared with conventional non-contrast and contrast mode scan, spectrum mode enhanced scan reduced effective dose by 48.76%. Conclusion VNC images could be a potential sub-stitution for TNC images for thyroid nodules evaluation.