Cayne Neal S, Veith Frank J, Lipsitz Evan C, Ohki Takao, Mehta Manish, Gargiulo Nick, Suggs William D, Rozenblit Alla, Ricci Zina, Timaran Carlos H
Department of Vascular Surgery, NYU Medical Center, New York, NY 10016, USA.
J Vasc Surg. 2004 Apr;39(4):811-5. doi: 10.1016/j.jvs.2003.11.042.
We noted substantial differences when measuring repeatedly the same abdominal aortic aneurysm (AAA) on the same computed tomography (CT) scan. This study quantitated this variability, and methods to minimize it were developed.
The CT maximal diameter of 25 AAAs was measured by eight experienced observers, including six vascular surgeons and two radiologists, using two methods: an unstandardized protocol, and a standardized protocol using fine calipers to carefully measure the largest diameter perpendicular to the estimated aneurysm centerline, from outer aneurysm wall to outer wall. The average measurement difference between observers was calculated for each method. The average difference between each observer's measurement and the official radiology report value was also calculated. Agreement between the two measurement methods was assessed with Bland-Altman plots.
The difference in maximal diameter measurements between each observer averaged 4.0 +/- 5.1 mm (range, 0.0-35.0 mm) with the unstandardized method. The mean measurement difference with the standardized protocol was significantly lower, and averaged 2.8 +/- 4.4 mm (range, 0.0-26.0 mm; P<.05). Measurements taken from the official radiology report differed from each of the observer's standardized measurement by an average of 5.0 +/- 6.3 mm (range, 0.0-28.0 mm). This difference was similar for both the unstandardized and standardized methods. Bland-Altman plots confirmed the wide variation of the maximal diameter measurements when the unstandardized method was compared with the standardized method (95% confidence interval, -9-9 mm).
Routine CT maximal diameter measurement of AAAs can have substantial interobserver variability. Standardized measurement protocols can decrease, but not eliminate, this measurement variability. Thus apparent size changes based on CT measurements may represent measurement artifact rather than actual aneurysm growth or shrinkage, particularly when a standardized system is not used.
我们注意到在同一计算机断层扫描（CT）上对同一腹主动脉瘤（AAA）进行多次测量时存在显著差异。本研究对这种变异性进行了量化，并开发了将其最小化的方法。
由包括六名血管外科医生和两名放射科医生在内的八名经验丰富的观察者，使用两种方法测量25个腹主动脉瘤的CT最大直径：一种是未标准化的方案，另一种是标准化方案，即使用精细卡尺从动脉瘤外壁到外壁仔细测量垂直于估计动脉瘤中心线的最大直径。计算每种方法观察者之间的平均测量差异。还计算了每个观察者的测量值与官方放射学报告值之间的平均差异。用Bland-Altman图评估两种测量方法之间的一致性。
采用未标准化方法时，每个观察者最大直径测量值的差异平均为4.0±5.1毫米（范围为0.0 - 35.0毫米）。标准化方案的平均测量差异显著更低，平均为2.8±4.4毫米（范围为0.0 - 26.0毫米；P<0.05）。官方放射学报告中的测量值与每个观察者的标准化测量值平均相差5.0±6.3毫米（范围为0.0 - 28.0毫米）。未标准化和标准化方法的这种差异相似。Bland-Altman图证实，与标准化方法相比，未标准化方法的最大直径测量值差异很大（95%置信区间为 -9 - 9毫米）。
腹主动脉瘤的常规CT最大直径测量可能存在显著的观察者间变异性。标准化测量方案可以减少但不能消除这种测量变异性。因此，基于CT测量的明显大小变化可能代表测量伪影，而非实际的动脉瘤生长或缩小，尤其是在未使用标准化系统时。
