A new model-based technique for enhanced small-vessel measurements in X-ray cine-angiograms

Arterial diameter estimation from X-ray cine angiograms is important for quantifying coronary artery disease (CAD) and for evaluating therapy. However, diameter measurement in vessel cross sections ≤1.0 mm is associated with large measurement errors. The authors present a novel diameter estimator which reduces both magnitude and variability of measurement error. They use a parametric nonlinear imaging model for X-ray cine angiography and estimate unknown model parameters directly from the image data. The authors´ technique allows them to exploit additional diameter information contained within the intensity profile amplitude, a feature which is overlooked by existing methods. This method uses a two-step procedure: the first step estimates the imaging model parameters directly from the angiographic frame and the second step uses these measurements to estimate the diameter of vessels in the same image. In Monte-Carlo simulation over a range of imaging conditions, the authors´ approach consistently produced lower estimation error and variability than conventional methods. With actual X-ray images, the authors´ estimator is also better than existing methods for the diameters examined (0.4-4.0 mm). These improvements are most significant in the range of narrow vessel widths associated with severe coronary artery disease.