# Dynamic Digital Radiography (DDR) for Pulmonary Blood Flow Assessment After Lung Transplantation: Insights From Two Case Studies

## TL;DR

This paper explores the use of dynamic digital radiography (DDR) to assess pulmonary blood flow in lung transplant patients, comparing it with the gold standard perfusion scintigraphy.

## Contribution

The study introduces DDR as a low-radiation alternative for monitoring post-transplant pulmonary perfusion and highlights its limitations compared to established methods.

## Key findings

- DDR showed inconsistent results compared to perfusion scintigraphy in one patient but aligned in another.
- Contrast-enhanced CT confirmed no thrombosis or flow abnormalities in both cases.
- DDR is a convenient, low-radiation tool but requires caution and further validation for clinical use.

## Abstract

Dynamic digital radiography (DDR) is an innovative imaging modality that enables real-time evaluation of dynamic processes by combining sequential images. DDR can assess pulmonary blood flow by analyzing variations in black and white signal intensities within the lung field. This case series evaluates the utility and limitations of DDR for monitoring pulmonary blood flow and thrombosis in two patients following lung transplantation. DDR findings were compared with those of pulmonary perfusion scintigraphy (PPS), the current gold standard for assessing regional pulmonary perfusion distribution. Case 1 is a male in his 40s who underwent a single (left) lung transplantation. Postoperative DDR indicated pulmonary perfusion distributions between the autologous (right) and transplanted (left) lungs of 46.89% vs. 53.11% at 3.5 months and 38.02% vs. 61.98% at six months. However, PPS indicated markedly different distributions: 15.78% vs. 84.22% at two months and 19.34% vs. 80.66% at six months. Case 2 is a male in his 40s who underwent bilateral sequential lung transplantation. DDR indicated pulmonary perfusion distributions between the right and left transplanted lungs of 51.10% vs. 48.90% at two months and 48.48% vs. 51.52% at six months. In this case, PPS findings were in close agreement: 54.82% vs. 45.18% at two months and 48.70% vs. 51.30% at six months. Contrast-enhanced CT confirmed the absence of thrombosis and flow abnormalities. DDR imaging in lung transplant patients offers a low-radiation and convenient approach for monitoring respiratory function and assessing complications. However, our findings indicate that DDR assessments of pulmonary blood flow do not consistently match those of PPS, the current reference standard. Caution and further investigations regarding the use of DDR are needed, including in the context of thrombosis evaluation.