Intravascular Ultrasonography Procedures Periprocedural Care

Updated: Jan 06, 2015
  • Author: Kartika Shetty, MD, FACP; Chief Editor: Karlheinz Peter, MD, PhD  more...
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Periprocedural Care

Equipment

A catheter consists of a miniaturized transducer and a console that reconstructs the image. High ultrasound frequencies are used, typically centered at 20-50 MHz and providing excellent resolution.

Monorail rapid exchange intracoronary ultrasound catheters have an outer diameter ranging between 2.6-3.5 Fr (0.87-1.17 mm diameter) and can be advanced through a 6-Fr guide catheter.

Two different types of transducers exist for intravascular ultrasonography: the mechanically rotating transducer and the electronically switched multielement array system.

A single rotating transducer is driven by a flexible drive cable at 1,800 rpm (30 revolutions per second) to sweep a beam almost perpendicular to the catheter. At approximately 1-degree increments, the transducer sends and receives ultrasound signals. They require flushing with saline to provide a fluid pathway for the ultrasound beam, because even small air bubbles can degrade image quality. In most mechanical systems, the transducer spins within a protective sheath while the imaging transducer is moved proximally and distally. This facilitates smooth and uniform mechanical pullback.

Electronic systems use an annular array of small crystals rather than a single rotating transducer. The transducers are activated sequentially to generate the image. The coordinated beam generated by groups of elements is known as a synthetic aperture array. The currently available electronic system provides simultaneous colorization of blood flow.

The imaging console includes components and software necessary to convert the ultrasonography signal to a graphic image on the monitor. Three display modes are currently available. Cross-sectional tomographic views are single-cut cross-sectional images; these are limited by spatial orientation and cannot provide information regarding the length and distribution of plaque. With longitudinal imaging (L mode), computerized image reconstruction techniques present a series of evenly spaced ultrasound images along a single-cut plane to approximate the longitudinal appearance of the artery. Motorized transducer pullback and digital storage of cross-sectional images are necessary for L mode. [17] Three-dimensional (3D) reconstructions of data are also available. [18]

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Patient Preparation

Anesthesia

Local anesthesia and minimal general sedation are used.

Positioning

The patient should lie supine on the angiogram table.

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