Optimization of individualized abdominal scan protocol with 64-slice CT scanner / 中华放射学杂志

ABSTRACT

ObjectiveTo explore an individualized abdominal scan protocol with a 64-slice CT scanner.MethodsFrom Sep.2010 to Nov.2010,one hundred consecutive patients,who underwent twice non-contrast-enhanced abdominal CT scans within 3 months,were enrolled in this study.For each patient,the tube current of 274 eff.mAs and 207 eff.mAs were applied respectively in the first and second abdominal scan.The imaging qualities of the two scans were evaluated retrospectively by 3 reviewers.All the individual variants,including height,weight,body mass index (BMI),the maximum transverse diameter,the anteroposterior diameter and the average maximum diameter of abdomen were recorded.A five-point scale was used for grading the image noise of eight organs,including abdominal aorta,portal vein,liver,spleen,gallbladder,pancreas,renal cortex and renal medulla. Diagnostic acceptability of CT images at three anatomic levels,including porta bepatis,pancreas and the upper pole of renal,was also evaluated by using a five-point scale.The noise value of abdominal aorta was defined as the standard deviation (SD) of CT values of aorta at the level of porta hepatis.Scatter diagram and Pearson correlation analysis were used for evaluating the linear relationship between the individual variants and the noise value of abdominal aorta,and multivariate linear regression analysis was used for evaluating the relevance between the individual variants and the noise value of aorta.ResultsIn this patients group,the average height was ( 164.6 ± 7.5 ) cm,the average weight was (64.3 ± 11.0) kg,the BMI was (23.7 ±3.3) kg/m2,the maximum transverse diameter of abdomen was(29.8 ± 2.3 )cm,the anteroposterior diameter of abdomen was (23.1 ± 2.9) cm,and the average maximum diameter of abdomen was ( 26.5 ± 2.5 ) cm.Pearson correlation analysis showed significant positive linear correlation between the noise value of abdominal aorta( 1 1.7 ± 3.0)and patients' weight ( r =0.744,P ＜ 0.01 ),BMI ( r =0.689,P ＜ 0.01 ),the maximum transverse diameter ( r =0.813,P ＜ 0.01 ),the anteroposterior diameter ( r =0.781,P ＜ 0.01 ),the average maximum diameter of the abdomen ( r =0.789,P ＜ 0.01 ) ; however,there was no positive linear correlation between the noise value of abdominal aorta and patients' height ( r =0.292,P ＜ 0.01 ). The maximum transverse diameter of abdomen is greatly related to the noise value of abdominal aorta (Beta =0.487,P ＜0.01 ).For the patient with the maximum transverse diameter of abdomen ranging from 27 to 32 cm,diagnostic acceptability of CT images at the anatomic level of porta hepatis showed statistical significance compared with the patient with the maximal transverse diameter of the abdomen greater than 32 cm or less than 27 cm (P ＜ 0.05 ).Conclusion The tube current of 207 eft.mAs is reasonable for abdominal CT scan for patients with the maximal transverse diameter of the abdomen ranging from 27 to 32 cm.