Intravascular ultrasound: a new potential modality for angioplasty guidance. Current angioplasty devices are limited by significant rates of arterial perforation and dissection, due to inadequate techniques of guidance, and by restenosis, which may be partly attributed to inadequate debulking of lesions. This paper describes the authors' initial experience in-vitro and in-vivo with intravascular ultrasound as a possible method of enhancing the three-dimensional guidance of devices through atherosclerotic obstructions. Using an in-vitro model they correlated the dimensions and histologic morphology of animal and human arteries with ultrasound images of the specimens. Additional in-vivo evaluations of this technology in canine arteriosclerotic and human atherosclerotic arteries preliminarily support the hypothesis that intravascular ultrasound defines the transmural arterial morphology and may enhance the accuracy of angioplasty procedures. Simultaneous imaging with angioscopy and intravascular ultrasound is demonstrated as a potential method of accurately defining both intraluminal and transmural arterial wall characteristics. 