Division of Radiology, Department of Medical Technology, Kyushu University Hospital, Fukuoka, Japan.
Department of Health Sciences, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan.
Phys Med. 2020 Feb;70:102-108. doi: 10.1016/j.ejmp.2019.12.025. Epub 2020 Jan 28.
Quantitative evaluations of airway dimensions through computed tomography (CT) have revealed a good correlation with airflow limitation in chronic obstructive pulmonary disease. However, large inaccuracies have been known to occur in CT airway measurements. Ultra-high-resolution CT (UHRCT) might improve measurement accuracy using precise scan modes with minimal focal spot. We assessed the effects of scan mode and focal spot size on airway measurements in UHRCT.
COPDGene Ⅱ phantom, comprising a plastic tube mimicking human airway of inner diameter 3 mm, wall thickness 0.6 mm, and inclination 30 degrees was scanned at super high resolution (SHR, beam collimation of 0.25 mm × 160 rows) and high resolution (HR, beam collimation of 0.5 mm × 80 rows) modes using UHRCT. Each acquisition was performed both with small (0.4 × 0.5 mm) and large (0.6 × 1.3 mm) focal spots. The wall area percentage (WA%) was calculated as the percentage of total airway area occupied by the airway wall. Statistical analysis was performed to compare the WA% measurement errors for each scan mode and focal spot size.
The WA% measurement errors in the SHR mode were 9.8% with a small focal spot and 18.8% with a large one. The measurement errors in the HR mode were 13.3% with a small focal spot and 21.4% with a large one. There were significant differences between each scan mode and focal spot size (p < 0.05).
The SHR mode with a small focal spot could improve airway measurement accuracy of UHRCT.
通过计算机断层扫描（CT）对气道尺寸进行定量评估，已显示出与慢性阻塞性肺疾病气流受限的良好相关性。然而，CT 气道测量中存在较大的不准确性。超高分辩率 CT（UHRCT）可能通过使用具有最小焦点的精确扫描模式来提高测量精度。我们评估了扫描模式和焦点大小对 UHRCT 气道测量的影响。
使用 UHRCT，对 COPDGene Ⅱ 体模（由模拟内直径 3mm、壁厚 0.6mm 和倾斜度 30 度的塑料管组成）进行超高分辨率（SHR，光束准直 0.25mm×160 排）和高分辨率（HR，光束准直 0.5mm×80 排）扫描。在每种采集模式下，均使用小焦点（0.4mm×0.5mm）和大焦点（0.6mm×1.3mm）进行扫描。气道壁面积百分比（WA%）定义为气道壁占总气道面积的百分比。对每种扫描模式和焦点大小的 WA%测量误差进行统计分析。
SHR 模式下小焦点的 WA%测量误差为 9.8%，大焦点为 18.8%。HR 模式下小焦点的 WA%测量误差为 13.3%，大焦点为 21.4%。各扫描模式和焦点大小之间存在显著差异（p<0.05）。
小焦点的 SHR 模式可提高 UHRCT 气道测量的准确性。
