Assessment of emphysema with simulated low-dose dark-field radiography.

OBJECTIVE: Dark-field radiography allows the visualization of lung tissue changes associated with pulmonary emphysema. Simulations were used to investigate the impact of radiation dose reduction on the diagnostic accuracy of emphysema detection. MATERIALS AND METHODS: Dark-field and attenuation chest radiographs acquired during an ongoing clinical study were used to simulate multiple low-dose counterparts corresponding to median effective doses between 7 and 18 µSv. All study participants had undergone a medically indicated chest computed tomography scan that showed either pulmonary emphysema or no lung pathologies. In a randomized reader study, three radiologists independently assessed the simulated low-dose dark-field and attenuation radiographs as well as the original images for the presence of emphysema. The area under the curves (AUC) of the receiver operating characteristics (ROC) were analyzed using Obuchowski's method. ROC curves were also generated by using different values of the dark-field coefficient to differentiate between absent and at least mild emphysema. RESULTS: The original (full-dose) images and simulated low-dose images of 93 participants (57 males, 36 females) were included, with participants' median age of 66 years (interquartile range 54 to 73 years). The radiologists' ROC curves of the simulated low-dose images at 11 µSv (AUC = 0.84) did not differ significantly (p = 0.177) from the full-dose curve (AUC = 0.86). For all dose levels, the dark-field coefficient could distinguish between absent and at least mild emphysema with an AUC of 0.85. CONCLUSION: Radiation dose reduction in dark-field imaging for emphysema assessment might be feasible, with median effective doses potentially as low as 11 µSv. KEY POINTS: Question How does radiation dose reduction affect the diagnostic potential of dark-field chest radiographs? Findings For actual, regular-dose (36 µSv) dark-field radiographs, AUC was 0.86, and 0.84 for simulated low-dose images. Down to 7 µSv, the dark-field coefficient AUC was 0.85. Relevance statement Simulations suggest that the radiation dose in dark-field chest imaging could be lowered to 11 µSv, indicating the technique's potential for ultra-low-dose imaging, which could be especially beneficial for potential clinical screening applications in the future.