|
It has been a long sought goal to visualize the morphology and structures of internal organs nonmvasively. Two dimensional imaging of body regions has proven to very successful in clinical and diagnostic medicine. Since the early work on three-dimensional (3D) display' of biomedical images by Greenleaf et. aL2 there is a growing realization that visualizing the actual shape and function of an organ in three-dimensional space and in time will enhance the diagnosis and possibly aid the management of patient therapy. The increasing speed of computations at decreasing costs, and the fact that many of the modem imaging methods generate images in digital form has made volumetric imaging feasible. Although the production of 3D images in the least time, with a greater accuracy, and at a reduced cost continues to be a desirable goal, significant progress has been made in this area in the past several years. The majority of studies in the discipline of 3D images has concentrated on the use of data from computed tomography or from magnetic resonance. The construction of three dimensional imaging from ultrasound data is not as common. This is partly due fact that the resthcted acoustic access of organs does not pmvide sufficient views to generate complete volume of imaged organs. As a consequence, the surfaces of the organs have been displayed as wire-frame models3' 'ISuch displays of medical images have although proven to be helpful in estimating volumes of the organ, they do not provide realistic organ visualization to which physicians can easily relate to for diagnosis. With the improvement in image technology, some of the problems have now been overcome by either rotating transducer through 180 degrees through apical acoustic window for heart5, or by scanning small peripheral limbs in transmission mode through water path6. Such scanning procedures provide data with sufficient integrity to synthesize realistic 3D images of organs. Also, the advent of catheter based ultrasonic technology provides a potential for three-dimensional imaging of blood vessels and is the topic of discussion in this paper. With the introduction of mechanical atherectomy and laser angioplasty there is an increasing risk of vessel perforation. This, along with other factors, has stimulated interest in developing methods for imaging surfaces underlying endothelial cell of arteries. High frequency ultrasonic imaging systems capable of providing 360 degree views of vessel cross-sections are now available commercially and are in clinical use amongst many researchers. Although, there are some initial encouraging results7 on 3D imaging, it is not yet fully established if it is feasible to (a) use a clinical scanner to obtain contiguous cross-sectional images of arteries; and (b) to use such serial cross-sections for volumetric imaging. This paper aims at providing perspectives on these issues of this rapidly evolving technology.
|
