低剂量恒流控制CT扫描在初治继发性肺结核随访中的价值

目的 探讨低剂量恒流控制CT扫描在初治继发性肺结核随访中对辐射剂量和图像质量的影响.方法 对156例初治继发性肺结核患者首次CT检查行自动管电流调制扫描(120 kV,50～330 mA),在治疗期间的前3个月随访时行低剂量恒流控制扫描(120 kV,50 mA).分别记录和计算两种扫描方式的辐射剂量指标:容积CT剂量...

Value of low-dose constant current control scanning in chest CT for the follow-up of secondary pulmonary tuberculosis in the primary therapy

Objective To assess the effect of low-dose constant current control (LD-CCC) scanning on radiation dose and image quality in chest CT for the follow-up of secondary pulmonary tuberculosis in the primary therapy.Methods A total of 156 patients with secondary pulmonary tuberculosis in the primary therapy were received the automatic tube current modulation (ATCM) technique (120 kV, 50~330 mA) at initial CT examinations, and the LD-CCC (120 kV, 50 mA) scanning at the first 3 months of follow up CT examinations. The radiation dose indexes of each scanning mode were recorded and calculate respectively,including the volumetric CT dose index (CTDIvol), dose length product (DLP), effective dose (ED) and size-specific dose estimates (SSDE).Objective image quality measures including CT attenuation, image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and figure of merit for the noise (FOMN) of aortic arch and normal lung parenchyma were assessed. Subjective image quality measures for nine forms of the basical lesions of secondary pulmonary tuberculosis were scored independently and blindingly on a five-point scale by two senior radiologists. The radiation dose and image quality indexes were compared by the paired Student t test. The consistency of CT image quality scores of two senior radiologists was evaluated by the Kappa test.Results Compared with the ATCM technique, CTDIvol, DLP, ED and SSDE of the LD-CCC scanning decreased by 68.2% (6.60/2.10 mGy), 69.9% (222.61/66.98 mGy×cm), 70.0% (3.23/0.97 mSv),and 67.8% (8.66/2.79 mGy), respectively (P＜0.001); the image noises of of aortic arch were increased by 56.2% (40.52/92.46)(P＜0.001) while SNRs were decreased by 98.2% (1.04/0.44)(P＜0.001); the image noises of of aortic arch were increased by 47.9% (48.84/93.82)(P＜0.001); and CNRs and FOMN of aortic arch and normal lung parenchyma were decreased by 95.0% (20.12/9.70) and 94.2% (21.89/1.26), respectively (P＜0.001). There were no significant differences in CT attenuation values of aortic arch and normal lung parenchyma between ATCM and LD-CCC scanning (P＞0.05). The consistency of CT image quality scores of two senior radiologists was excellent (Kappa=0.833,P＜0.05). No statistically significant difference in subjective image quality scores for nine forms of the basical lesions of secondary pulmonary tuberculosis between ATCM and LD-CCC scanning was observed.Conclusions LD-CCC scanning should be recommended for the follow-up of secondary pulmonary tuberculosis in the primary therapy, because the radiation dose of the LD-CCC scanning are more significantly reduced than those of the ATCM technique, and subjective image quality scores have not been obviously changed.