Although intracoronary ultrasonography allows detailed tomographic imaging of the arterial wall, it fails to provide data on the structural architecture and longitudinal extent of arterial disease. This information is essential for decision making during therapeutic interventions. Three-dimensional reconstruction techniques offer visualization of the complex longitudinal architecture of atherosclerotic plaques in composite display. Progress in computer hardware and software technology have shortened the reconstruction process and reduced operator interaction considerably, generating three-dimensional images with delineation of mural anatomy and pathology. The indications for intravascular ultrasonography will grow as the technique offers the unique capability of providing ultrasonic histology of the arterial wall, and the need for a three-dimensional display format for comprehensive analysis is increasingly recognized. Consequently, three-dimensional imaging is being rapidly implemented in the catheterization laboratories for guidance of intracoronary interventions and detailed assessment of their results. However exciting the prospects may be, three-dimensional reconstructions at present remain partially artificial because the true spatial position of the imaging catheter tip is not recorded, and shifts in its location and curves of the arterial lumen result in pseudoreconstructions rather than true reconstructions. In this report, we address the principles of three-dimensional reconstruction with a critical review of its limitations. Potential solutions for refinement of this exciting imaging modality are presented.

Current three dimensional (30) vessel reconstruction using intravascular ultrasound (IVUS) pull buck is limited by the lack of information on the real vessel curvatures, because the movement of the catheter is assumed to proceed along a straight path. To overcome this limitation a method (ANGUS) has been developed to combine coronary angiography with data obtained by IVUS [I]. The IVUS data represent a cylindrical stack of crosssections. A least-square@ approximation is used to reconstruct the 3 0 path of the catheter axis from two biplane X-ray images, after which the stack of IVUS contours is wrapped around this 3 0 catheter centerline. In order to establish the correct rotational position of the stack around the centerline, use is made of 'landmarks' which are visible in angiograms, as well as in a simulation of these angiograms derived from the reconstructed 3 0 contour. The combination of ANGiography and intravascular UltraSound (ANGUS) is promising and provides a unique method of three-dimensional reconstruction of coronary geometry.

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Abstract--Ultrasound images from human arteries obtained in vivo with an intravascular 30 MHz ultrasound imaging device show that blood echogenicity changes during the cardiac cycle. Quantitative measurements of blood echogenicity during the cardiac cycle suggest that these variations may be related to changes in the state of erythrocyte aggregation, which are induced by varying shear rate.

Pulsed lasers are being promoted for laser angioplasty because of their capacity to ablate obstructions without producing adjacent thermal tissue injury. The implicit assumption that thermal injury to the artery is to be avoided was tested. Thermal lesions were produced in the iliac arteries and aorta of normal rabbits by a) electrical spark erosion, b) the metal laser probe, and c) continuous wave neodymium-yttrium aluminum garnet (Nd-YAG) laser energy through the sapphire contact probe. High-energy doses were used to induce substantial damage without perforating the vessel wall. Thermal lesions (n = 77) were compared with mechanical lesions (n = 22) induced by oversized balloon dilation. Medial necrosis was induced by all four injury methods. Provided no extravascular contrast was observed after the injury, all damaged segments were patent after 1 to 56 days. The progression of healing with myointimal proliferation was remarkably similar for all injuries. At 56 days, the neointima measured up to 370 microns. In conclusion, provided no perforation with contrast extravasation occurred, the normal rabbit artery recovered well from transmural thermal injury. The wall healing response is largely nonspecific.