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INTRODUCTION

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Intravascular ultrasound (IVUS) has become a standard imaging technique in high volume, experienced interventional laboratories, but most of its use is relegated to the coronary arteries. While conventional angiography provides a single-plane "shadow" of the vascular lumen, it has limited ability to accurately and reproducibly measure vessel stenosis and characterize plaque morphology. The high-definition, cross-sectional images of the arterial lumen and the arterial wall provided by IVUS allow a far more detailed analysis of the target vessel and peripheral interventional success. Nonetheless, IVUS has not enjoyed wide deployment in the peripheral interventional arena. This chapter will provide the information needed to utilize IVUS during peripheral interventions by reviewing the fundamentals of IVUS technology, image interpretation and standardized measurements, its general application during peripheral vascular interventions, and some specific considerations for each vascular territory.

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HISTORICAL PERSPECTIVE

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One of the first IVUS catheters was designed in 1972s by Bom et al.1 with the purpose of exploring the intracardiac chambers and cardiac structures. During the early and mid-1980s, new catheters were designed in order to evaluate and characterize the arterial structures. Because of their size and catheter stiffness, early clinical studies with IVUS in the late 1980s were done primarily in the periphery. In the early 1990s, rapid technical improvement in catheter design, transducer technology, and subsequently imaging quality produced clinically useful catheters. The standard IVUS catheter was reduced to 3.5 to 4.3 F catheter, which led to marked growth of their use in coronary interventional cardiology research and practice. In the last 10 years, IVUS has moved from being solely a research tool to an established modality in clinical practice. While the use in the coronaries remains more common than in the peripheral arteries, the primary techniques, diagnostic utility, and therapeutic benefits remain similar.

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IVUS serves three important clinical purposes—diagnosis, guiding the interventional strategy, and optimizing the interventional result. Starting with diagnosis, IVUS is the gold standard method to assess intermediate stenosis, ambiguous lesions, bifurcations, unusual lesion morphology (aneurysms, calcium, thrombi), in-stent restenosis, and any other unusual angiographic finding.2 From an interventional perspective, IVUS has been utilized extensively as a guide to the procedure, aiding in selection of optimal strategy, adjuvant device utilization (rotational atherectomy, predilation, etc.) as well as selection of stent diameter and length.3 Additionally, IVUS imaging enables optimization of stenting procedures, maximizing expansion and apposition, and identifying poststenting complications such as vessel rupture and dissection.

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TECHNOLOGY

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Two different IVUS transducer technologies are currently available—solid state (or phase array) and mechanical (Figure 21-1).4 Solid-state configuration has 64 transducer elements arranged as a collar around the catheter. The backscattered ultrasound information received from each transducer element is sent to a computer that performs real-time image reconstruction to formulate a cross-sectional image of the artery. The advantage of this catheter is that there are no mobile parts and therefore, no motion ...

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