Kido Shoji, Sasaki Shinji
Department of Computer Science and System Engineering, Faculty of Engineering, Yamaguchi University, Japan.
J Thorac Imaging. 2003 Apr;18(2):80-6. doi: 10.1097/00005382-200304000-00004.
The authors investigated whether fractal analysis can be used with chest radiography for assessment of increased pulmonary blood flow. As a physical measure they used a fractal dimension (FD), which can be used for quantifying texture in selected regions of interest (ROIs). In general, the pulmonary capillary wedge pressure (PCWP) is normally less than 10 mm Hg, the redistribution of pulmonary blood flow reflects PCWP greater than or equal to 10 mm Hg, and the interstitial edema is observed in PCWP greater than or equal to 20 mm Hg. So, the study group consisted of 34 patients with mitral stenosis and 46 patients without mitral stenosis. These patients with and without mitral stenosis were divided into three groups based on their pulmonary capillary wedge pressure (PCWP): normal (n = 38; PCWP, <10 mmHg), mildly increased (n = 26; PCWP, 10 to <20 mmHg), and severely increased (n = 16; PCWP, >or=20 mmHg). ROIs were selected in the right upper and lower lung zones of digitized chest radiographs, and FDs were calculated in each ROI. As a measure of increased pulmonary blood flow, the upper-to-lower FD ratio (FDu/L) was calculated. Five chest radiologists estimated the degree of increased pulmonary blood flow for the same images of ROI sets presented on a cathode ray tube monitor in a randomized order. Between the normal PCWP group and the increased PCWP group, there were no significant differences in utility between the FDu/L and radiologists (P = 0.063). However, when the normal and the mildly increased PCWP groups were compared, the utility of the FDu/L was superior to that of radiologists (P = 0.042). These results indicate that fractal analysis is useful for quantitative estimation of increased pulmonary blood flow, especially in cases of mildly increased pulmonary blood flow.
作者研究了分形分析是否可用于胸部X线摄影以评估肺血流量增加的情况。作为一种物理测量方法，他们使用了分形维数（FD），其可用于量化选定感兴趣区域（ROI）的纹理。一般来说，肺毛细血管楔压（PCWP）通常小于10 mmHg，肺血流重新分布反映PCWP大于或等于10 mmHg，而在PCWP大于或等于20 mmHg时可观察到间质性水肿。因此，研究组包括34例二尖瓣狭窄患者和46例无二尖瓣狭窄患者。这些有和无二尖瓣狭窄的患者根据其肺毛细血管楔压（PCWP）分为三组：正常组（n = 38；PCWP，<10 mmHg）、轻度升高组（n = 26；PCWP，10至<20 mmHg）和重度升高组（n = 16；PCWP，≥20 mmHg）。在数字化胸部X线片的右上和下肺区选择ROI，并计算每个ROI的FD。作为肺血流量增加的一种测量方法，计算上下FD比值（FDu/L）。五位胸部放射科医生以随机顺序估计在阴极射线管显示器上呈现的相同ROI集图像的肺血流量增加程度。在正常PCWP组和PCWP升高组之间，FDu/L和放射科医生的效用没有显著差异（P = 0.063）。然而，当比较正常和轻度升高PCWP组时，FDu/L的效用优于放射科医生（P = 0.042）。这些结果表明，分形分析对于定量估计肺血流量增加是有用的，尤其是在肺血流量轻度增加的情况下。
