Optimization of pulmonary blood flow analysis method using dynamic chest radiography

Pulmonary blood flow analysis was conducted utilizing dynamic chest radiography (DCR) and pixel values assessed within a region of interest (ROI) in the left ventricle as reference signals. However, the effect of the ROI placement on the analysis accuracy is still uncertain.

This study aimed to identify the ROI locations that produced clinically useful images with higher signal values.

A total of 40 DCR, single-photon emission computed tomography, computed tomography angiography (CTA), and angiography image data from 15 patients with chronic thromboembolic pulmonary hypertension were analyzed. The DCR images were analyzed, and the time difference rate of each peak value (PD%) was calculated based on the correlation between the reference signal and heart rate phase. To clarify the ROI for acquiring clinically valuable high-signal-value images, the ROI locations of the high- and low-signal-value images were categorized, and PD% values were statistically compared across the ROI locations. Furthermore, the ROI locations of the high- and low-signal-value images were visually inspected for anatomical positions using the CTA images.

There were significant differences in PD% between high- and low-signal- value images when the ROIs were positioned within the upper and inside heart regions on DCR (median PD%: 4.48% and 4.41%, respectively; p < 0.05). The ROI location of the low-signal-value images on CTA tended to be in the middle of the heart, encompassing the right ventricular wall and the interior, excluding the left ventricular cavity.

The study identified the ROIs that could yield clinically valuable images with higher signal values in the DCR-based analysis of pulmonary blood flow. This discovery is anticipated to enhance the efficiency and reliability of pulmonary blood flow imaging for diagnosing chronic thromboembolic pulmonary hypertension with DCR.