Accuracy of intravascular ultrasound for diameter measurement of phantom arteries

Intravascular ultrasound in the coronary arteries

With technical improvements in catheter designs, intravascular ultrasound (IVUS) imaging of coronary arteries has become a routine procedure in most cardiac catheterization laboratories. In clinical practice, IVUS imaging of the coronary arteries is commonly performed to answer specific clinical questions such as the evaluation of an indeterminate narrowing of the left main coronary artery. In recent years, IVUS is also being performed as an endpoint for drug treatment trials in the assessment of atherosclerosis progression and/or regression. In this review we will focus on how validation studies of coronary IVUS systems have advanced our ability to use this powerful imaging tool and understand IVUS images, how acoustic and geometric factors affect proposed image processing tools and illustrate some current clinical uses of coronary IVUS.

Geometrical accuracy and fusion of multimodal vascular images: A phantom study

The aim of this work was to compare the geometrical accuracy of x-ray angiography, magnetic resonance imaging (MRI), x-ray computed tomography (XCT), and ultrasound imaging (B-mode and IVUS, or intravascular ultrasound) for measuring the lumen diameters of blood vessels. An image fusion method was also developed to improve these measurements. The images were acquired from a phantom that mimic vessels of known diameters. After acquisition, the multimodal images were coregistered by manual alignment of fiducial markers, and then by maximization of mutual information. The fusion method was performed by means of a fuzzy logic modeling approach followed by a combination process based on a possibilistic theory. The results showed (i) the better geometrical accuracy of XCT and IVUS compared to the other modalities, and (ii) the better accuracy and smaller variability of fused images compared to single modalities, with respect to most diameters investigated. For XCT, the error varied from 0.4% to 5.4%, depending on the vessel diameter that ranged from 0.93 to 6.24 mm. For IVUS, the error ranged from -0.3% to 1.7% but the smallest vessel (0.93 mm) could not be investigated because of the probe size. Compared to others fusion schemes, the XCT-MRI fused images provided the best results for both accuracy (from -1.6% to 0.2% for the three largest vessels) and robustness (mean relative error of 1.9%). To conclude, this work underlined both the usefulness of the multimodality vascular phantom as a validation tool and the utility of image fusion in the vascular context.