Ko Jane P, Marcus Rachel, Bomsztyk Elan, Babb James S, Stefanescu Cornel, Kaur Manmeen, Naidich David P, Rusinek Henry
Thoracic Division, Department of Radiology, New York University Medical Center, 560 First Ave, New York, NY 10016, USA.
Radiology. 2006 Apr;239(1):79-85. doi: 10.1148/radiol.2391041453.
To identify, by using a chest phantom, whether vessels that contact lung nodules measuring less than 5 mm in diameter will affect nodule volume assessment.
Forty synthetic nodules (20 with ground-glass attenuation and 20 with solid attenuation) that measured less than 5 mm in diameter were placed into a chest phantom either adjacent to (n = 30) or isolated from (n = 10) synthetic vessels. Nodules were imaged by using low-dose (20 mAs) and diagnostic (120 mAs) multi-detector row computed tomography (CT). Nodules that were known to lie in direct contact with vessels were confirmed by visual inspection. Nontargeted 1.25 x 1.00-mm sections were analyzed with a three-dimensional computer-assisted method for measuring nodule volume. A mixed-model analysis of variance was used to examine the influence of several factors (eg, the presence of adjacent vessels; tube current-time product; and nodule attenuation, diameter, and location) on measurement error.
The mean absolute error (MAE) for all nodules adjacent to vessels was 2.3 mm(3), which was higher than the MAE for isolated nodules (1.9 mm(3)) (P < .001). This difference proved significant only for diagnostic CT (2.2 mm(3) for nodules adjacent to vessels vs 1.3 mm(3) for nodules isolated from vessels) (P < .05). A larger MAE was noted for nodules with ground-glass attenuation (2.3 mm(3)) versus those with solid attenuation (2.0 mm(3)), for increasing nodule volume (1.66 mm(3) for nodules smaller than 20 mm(3) vs 2.83 mm(3) for nodules larger than 40 mm(3)), and for posterior nodule location (P < .05).
The presence of a vessel led to a small yet significant increase in volume error on diagnostic-quality images. This represents less than one-third of the overall error, even for nodules larger than 40 mm(3) or approximately 4 mm in diameter. This increase, however, may be more important for smaller nodules with errors of less than 3 mm(3).
通过使用胸部体模，确定与直径小于5mm的肺结节接触的血管是否会影响结节体积评估。
将40个直径小于5mm的合成结节（20个磨玻璃密度结节和20个实性密度结节）置于胸部体模中，其中30个与合成血管相邻，10个与合成血管隔离。使用低剂量（20mAs）和诊断剂量（120mAs）的多排螺旋计算机断层扫描（CT）对结节进行成像。通过目视检查确认已知与血管直接接触的结节。使用三维计算机辅助方法对非靶向的1.25×1.00mm层面进行分析，以测量结节体积。采用混合模型方差分析来检验几个因素（如相邻血管的存在、管电流-时间乘积以及结节的密度、直径和位置）对测量误差的影响。
所有与血管相邻的结节的平均绝对误差（MAE）为2.3mm³，高于隔离结节的MAE（1.9mm³）（P<.001）。仅在诊断性CT中，这种差异具有统计学意义（与血管相邻的结节为2.2mm³，与血管隔离的结节为1.3mm³）（P<.05）。磨玻璃密度结节的MAE（2.3mm³）高于实性密度结节（2.0mm³），随着结节体积增大（小于20mm³的结节为1.66mm³，大于40mm³的结节为2.83mm³）以及结节位于后方时MAE增大（P<.05）。
血管的存在导致诊断质量图像上的体积误差虽小但有显著增加。即使对于直径大于40mm³或约4mm的结节，这一误差增加也不到总体误差的三分之一。然而，对于误差小于3mm³的较小结节，这种增加可能更为重要。
