Development of pulmonary blood flow evaluation method with a dynamic flat-panel detector: quantitative correlation analysis with findings on perfusion scan

Abstract

Pulmonary blood flow is reflected in dynamic chest radiographs as changes in X-ray translucency, i.e., pixel values. Thus, decreased blood flow should be observed as a reduction of the variation of X-ray translucency. We performed the present study to investigate the feasibility of pulmonary blood flow evaluation with a dynamic flat-panel detector (FPD). Sequential chest radiographs of 14 subjects were obtained with a dynamic FPD system. The changes in pixel value in each local area were measured and mapped on the original image by use of a gray scale in which small and large changes were shown in white and black, respectively. The resulting images were compared to the findings in perfusion scans. The cross-correlation coefficients of the changes in pixel value and radioactivity counts in each local area were also computed. In all patients, pulmonary blood flow disorder was indicated as a reduction of changes in pixel values on the mapping image, and a correlation was observed between the distribution of changes in pixel value and those in radioactivity counts (0.7 ≤ r, 3 cases; 0.4 ≤ r < 0.7, 7 cases; 0.2 ≤ r < 0.4, 4 cases). The results indicated that the distribution of changes in -1 -pixel value could provide a relative measure related to pulmonary blood flow. The present method is potentially useful for evaluating pulmonary blood flow as an additional examination in conventional chest radiography.

Pulmonary perfusion by chest digital dynamic radiography: Comparison between breath‐holding and deep‐breathing acquisition

“…Digital dynamic radiography is a completely novel modality that can capture images similar to those of pulmonary angiography and scintigraphy 8,11,12,15,16 in a short time. Moreover, it does not require the use of contrast media.…”

“…In addition to the protocol, there are two other differences between the present study and previous studies. 11,12,15,16 The first is that the present study included the largest number of patients examined in this field. Thus far, only a few number of case reports, preliminary studies, and animal experiments 14 have been reported on DDR technology for pulmonary perfusion.…”

“…Chest DDR can detect the change in pixel value synchronized with the cardiac cycle, and generate vivid pulmonary perfusion images. 8,11,12 Its duration is approximately 15 s, it does not require contrast media, and can be performed in the standing, seated, and supine positions. Owing to the high sensitivity of the flat panel detector, the total exposure to radiation can be less than the limits for two projections recommended by the International Atomic Energy Agency (1.9 mGy).…”

“…15,16 Moreover, DDR images were remarkably similar to those of pulmonary angiography, the iodine mapping images acquired with dual-energy CT, and those of lung perfusion scintigraphy. 11,12 The deep-breathing protocol is an imaging protocol that has been used since the dawn of DDR technology. 8 It was an innovative method for the simultaneous evaluation of both ventilation and pulmonary blood flow by pausing for 2 s between deep breaths.…”

“…In a previous study of chest DDR conducted by Tanaka et al, breathholding at rest expiratory level was helpful in capturing vivid pulmonary perfusion images. 12 Nevertheless, the appropriate duration of breath-holding or levels (e.g., maximum or rest, expiratory or inspiratory) are unclear. For clinical use, a shorter breath-holding time is preferable.…”