Ray-based approach to skeletal muscle perfusion measurement on interventional x-ray systems.

Purpose: Quantitative assessment of tissue perfusion by imaging methods could improve outcome control during treatment of peripheral vascular disease. Currently, revascularization treatments are assessedby planar angiography which only allows for qualitative inspection of blood flow in vessels. In this paper, we present a method for quantitative estimation of contrast enhancement (i.e., temporal attenuation curves) in skeletal muscles using a C-arm system for effective evaluation during treatment. Methods: The proposed method tackles the loss of spatial depth information which occurs in conventional angiography by combining the acquired angiograms with two additional C-arm rotational soft tissue scans. The area subject to contrast propagation is segmented from the two images that are tomographically reconstructed from the rotational scans and is then used to estimate from the angiograms the spatially averaged contrast attenuation alongthe X-ray directions. A segmentation method which is tailored to theestimation procedure is applied to reduce inaccuracies in the estimation. The accuracy of the method in estimating temporal attenuationcurves in muscular tissue is evaluated in a simulation study usingexperimental data from CT perfusion acquisitions. Results: Resultsshow that the estimation accuracy is limited (16-25% relative error)owing to spatial inhomogeneity of contrast which appears characteristic of the way contrast diffuses in muscular tissue and to the presence of vessels along the X-ray directions. Nonetheless, the methodallows for quantitative differentiation of normal and hypoperfused tissue which is challenging when using conventional angiography. Conclusions: Periprocedural quantification of muscle perfusion as provided with the presented method can be applied to measure differencesoccurring in response to peripheral revascularization; therefore theproposed method represents an improvement with respect to the current methods for immediate post treatment assessment in the angio-room