低管电压扫描技术在CT泪囊造影成像中的应用研究

目的:探讨低管电压扫描方案在CT泪囊造影成像中的可行性。方法:采用拟人头颈部模体，将对比剂(碘海醇)与盐水1∶3混合液置于模体鼻翼一侧模拟泪囊。分别采用80、100、120和140 kV对模体进行扫描，每种管电压选择相应的mAs使设备显示的容积CT剂量指数(CTDI vol)分别为10、15、20、25、3...

Study of the application of low tube potemtial scanning in dacryocystography CT

Objective To investigate the feasibility of the application of low tube potential scanning in dacryocystography CT. Methods The mixture of iohexol and saline with the ration of 1:3 as the dacryocyst was set on the nose wing of the head-neck phantom. The phantom was scanned at 80, 100, 120, 140 kV with appropriate mAs to set the volume CT dose index(CTDI_vol)at 10,15,20,25,30,35 or 40 mGy. All the images were objectively evaluated to find out the optimal scanning parameters of 80 kV/240 mAs with the same contrast-to-noise ratio(CNR)of conventional scanning condition of 120 kV/180 mAs. A total of 62 patients who conducted dacryocystography CT in Beijing Tongren Hospital from November 2019 to July 2020 were prospectively selected. They were randomly divided equally into conventional scanning group with 120 kV/180 mAs and low tube potential group with 80 kV/240 mAs. The CT number, noise (SD) and contrast-to-noise ratio (CNR) of the two groups were measured as the objective evaluation indicators of image quality. The subjective evaluation was performed by two senior radiologists using a double-blind method and a 5-scale system evaluation. Results For the phantom study, the CNR was positively correlated with CTDI_vol under the same tube potential (r=0.985, 0.965, 0.971, 0.972, P<0.05). With the same CNR, the radiation dose decreased with lower tube potential. Under the conventional scanning parameters of 120 kV/180 mAs, the CNR was 27.8. At the same CNR, the optimal scanning parameters were 80 kV/240 mAs. For the clinical study, the CTDI_vol of conventional scanning group and low tube potential group were 31.2 and 12.8 mGy respectively, 59% decreased in low tube potential group. There were statistically significant differences in CT number of dacryocyst area, CT number of orbital fat area and noise between the two groups (t=-3.476, 2.601, -5.704, P<0.05). There was no statistically significante difference in CNR between 2 groups(P>0.05). Two observers had a good consistency (Kappa >0.75). There was no statistically significante difference in subjective rating between 2 groups(P>0.05). Conclusions Low tube potential scanning could obtain satisfactory image quality in dacryocystography CT at much lower radiation dose.