The Application of Tube Current Modulation Technique in CT Examination of Upper Respiratory TractChinese Full Text
ZHANG Yongxian;ZHANG Zongrui;WANG Shufang;Department of Radiology,Beijing Tongren Hospital,Capital Medical University;
Abstract: Objective To investigate the feasibility of using tube current modulation technique to reduce the radiation dose in CT examination of upper respiratory tract.Methods A total of 99 adult patients were enrolled in this study.The patients were randomly and equally divided into three groups with 33 cases in each group.CT scanning of upper respiratory tract was performed in all patients.In the conventional dose group（ group A） the preset effective m As was 250 m As / slice,in the Doseright group（ group B） the recommended m As（ according to the surview and scanning range） was employed,while in the Z-DOM group（ Z axis tube current modulation,group C） the tube current was automatically adjusted by the system according to the positioning in the Z axis direction.During the scanning course the m A value was kept stable in group A and group B,while the m A value was changing in group C; the other parameters used in all three groups were the same.All the images were reconstructed by filtered back projection（ FBP） algorithm.The median sagittal images were reformatted with 3 mm thickness,and their corresponding contrast-to-noise ratios（ CNR） were calculated; the median sagittal images were subjectively evaluated by five division method（ subjective evaluation score）.The values of CTDI,CNR,DLP and subjective evaluation score of three groups were statistically analyzed.Results For group A,B and C,the CTDI was（ 14.70 ± 0.00） m Gy,（ 16.50 ± 2.59） m Gy and（ 4.60 ± 1.99） m Gy respectively; the DLP was（ 465.87 ± 31.55） m Gy·cm,（ 526.15 ± 98.28） m Gy·cm and（ 147.74 ± 67.08） m Gy·cm respectively; and the differences in radiation doses between each other among the three groups were statistically significant（ the F values of CTDI and DLP were 381.24 and381.24 respectively,P ＜ 0.05）.The radiation dose of group B was 10% higher than that of group A,the dose of group C was significantly lower than that of group A and group B: about 70% lower than that of group B and 75% lower than that of group A.The CNR of group A,B and C was 523.91 ± 80.75,540.28 ± 117.65 and 511.09 ± 107.56 respectively,and the differences in CNR between each other among the three groups were statistically significant（ F = 0.603,P = 0.549 ＞0.05）.The subjective evaluation scores of group A,B and C were 10.5（ 10,11.5）,11（ 10.5,11.5） and 12.5（ 12.25,13.0） respectively,and the differences in subjective evaluation score between each other among the three groups were statistically significant（ chi-square = 48.373,P ＜ 0.05） : the subjective evaluation score of group B was slightly higher than that of group A（ chi-square = 0.038,P ＞ 0.017）,the subjective evaluation score of group C was higher than that of group A and group B（ chi-square values were 36.972 and 36.972 respectively,P ＜ 0.017）.Conclusion The use of Z-DOM technique in CT examination of upper respiratory tract can effectively reduce the radiation dose while higher image quality can be reliably preserved.Therefore,this technique should be recommended in clinical practice.
Keywords：
Upper air way Tomography; X-ray computed Filtered back-projection Radiation dose Image quality Comprehensive evaluation;
- DOI：
10.13437/j.cnki.jcr.2014.11.036
- Series：
- Subject：
- Classification Code：
R816.4
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