Computerized radiographic assessment of pulmonary blood flow in patients with and those without mitral stenosis

Fractal analysis for the assessment of pulmonary blood flow on chest radiographs

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.

Comparison between computer-aided diagnosis and radiologists: assessment of pulmonary blood flow on chest radiographs

To evaluate the performance of a computer-aided diagnosis (CAD) scheme for estimating increased pulmonary blood flow on chest radiographs, we compared computerized assessment with findings by radiologists. Our CAD scheme extracts selectively linear opacities corresponding to vessels in regions of interest (ROIs) in the right upper and lower lung zones on digitized chest radiographs, and then calculates a radiographic index as a physical measure that reflects the area of the extracted opacities in selected ROIs. As a measure of increased pulmonary blood flow, the upper/lower radiographic index ratio was calculated for each patient. Seven 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-pulmonary capillary wedge pressure (PCWP) group and increased-PCWP groups, there was no significant difference in performance between CAD and radiologists (p = 0.105). However, when the normal and mild PCWP groups were compared, the performance of CAD was superior to that of radiologists (p = 0.001). This study indicates that our CAD scheme is promising for quantitative estimation of increased pulmonary blood flow, especially in mild cases.