64层螺旋CT腹部扫描参数优化的个体化选择

Optimization of individualized abdominal scan protocol with 64-slice CT scanner

目的探讨64层螺旋CT腹部扫描参数优化的个体化选择。方法回顾性分析2010年9月至11月期间，3个月内因临床诊断或治疗需要行2次腹部CT平扫检查的连续患者100例资料。首次检查采用管电流274有效mAs（eff.mAs），第2次检查采用207eff. mAs，分析评价2次检查的图像质量。记录受检者身高、体质量、体质量指数（BMI）、上腹部最大横径、上腹部前后径、上腹部平均最大径。3名阅片者对腹主动脉、门静脉主干、肝脏、脾脏、胆囊、胰腺、肾皮质、肾髓质等8个主要器官进行图像主观噪声评价，对肝门、胰腺、肾上极3个主要层面进行诊断接受率评价。采用散点图及Pearson相关分析显示各指标与腹主动脉噪声值（sD值）的线性关系，通过多因素线性回归分析评价各指标与腹主动脉sD值的相关性，利用最相关的指标指导腹部CT个性化参数扫描。结果100例受试者体质量为（64．3±11．0）kg，BMI为（23．7±3．3）kg／m＾2，上腹最大横径为（29．8±2．3）cm，上腹前后径为（23．1±2．9）cm，上腹平均最大径为（26．5±2．5）cm，分别与主动脉SD值（11．7±3．0）呈中度或高度相关（r值分别为0．744、0．689、0．813、0．781、0．789，P值均〈0．01），身高为（164．6±7．5）cm，与主动脉sD值基本不相关（r=0．292，P〈0．01）。上腹部最大横径与肝门层面腹主动脉SD值最相关且两者的线性关系具有统计学意义（Beta=0．487，P〈0．01）。上腹最大横径在27-32cm范围内其肝门层面诊断接受率评价与上腹最大横径〈27cm或者〉32cm差异具有统计学意义（P值均〈0．05）。结论管电流207eEmAs适用于上腹最大横径在27-32cm范围内的受检者。

Objective To explore an individualized abdominal scan protocol with a 64-slice CT scanner. Methods From 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 elf. 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 hepatis, 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. Results In this patients group,the average height was （ 164. 6±7.5 ） em, the average weight was （ 64. 3±11.0 ） kg, the BMI was （ 23.7±3.3 ） kg/m2, the maximum transversediameter 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 （11.7±3.0）and patients＇ weight （r = O. 744, P 〈 0. 01 ）, BMI （r = 0. 689, P 〈 0. 01 ）, the maximum transverse diameter （ r = O. 813, P 〈 O. 01 ）, the anteroposterior diameter （ r = O. 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 = O. 292, P 〈 O. 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 era（ P 〈 0. 05 ）. Conclusion The tube current of 207 eff. mAs is reasonable for abdominal CT scan for patients with the maximal transverse diameter of the abdomen ranging from 27 to 32 cm.