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Objective:
Assessment of lung perfusion is an important element in the preoperative evaluation of patients being considered for lung transplant or resection. This assessment is routinely performed using nuclear medicine lung scintigraphy. Dynamic digital radiography (DDR) is a newer radiographic technique where rapid sequential diagnostic radiographs of the chest with full field of view can be obtained throughout multiple respiratory cycles. By assessing pixel signal changes in the lung parenchyma over a few cardiac cycles, the regional lung perfusion can be estimated. This pilot study will compare the results of the differential lung perfusion between the right and left lungs using DDR with the same results obtained from lung scintigraphy.

Materials and Methods:
A retrospective review of patients evaluated with both nuclear medicine lung scintigraphy and DDR was performed. The DDR examinations were performed between January 14, 2022 and August 16, 2022. Each patient had a lung scintigraphy perfusion study within 6 months of the DDR examination. The percent differential of perfusion between the lungs was calculated using both modalities and the results were analyzed for statistical correlation.

Results:
Results for 24 patients were reviewed (mean age - 58 years, 6 women). The mean absolute percent differential in perfusion between the right and left lungs was (17.9 +/- 14.8%) using DDR and (19.7 +/- 16.3%) using lung scintigraphy. The mean absolute difference between the results of the two methods was (8.6 +/- 7.1%, maximum 24.2%, minimum 0.3 %). There was only one patient in which there was a discrepancy between the two modalities in determining which lung was better perfused. The Pearson coefficient of correlation was r = 0.87 (95% confidence interval (0.7180, 0.9455), p < 0.0001) indicating a strong correlation between the perfusion results obtained by the two modalities.

Conclusion:
DDR performs comparably to nuclear medicine lung scintigraphy for the assessment of differential lung perfusion. DDR can be performed and analyzed more quickly than lung scintigraphy and is also cheaper with a decreased radiation dose to the patient. It should be noted that the DDR examinations in this study were performed with the patient in an upright position whereas lung scintigraphy is performed in a supine position. While this positioning should not affect the right-to-left distribution of lung perfusion, it is expected to lead to differences in the cranio-caudal distribution of perfusion. Further work is need with a larger patient cohort to confirm the results of this preliminary study and to further assess the effects of patient positioning on the regional perfusion distribution.