Clinical Indications Background

Peripheral vascular disease (PVD) is a major health problem accounting for more than 100,000 surgical procedures annually in the United States alone [ 1 ]. PVD is caused by the systemic process of atherosclerosis, and is frequently associated with coronary, renal and carotid arterial disease. The management of a patient with PVD has to be planned in the context of the epidemiology of the disease and, in particular, the apparent risk factors or markers predicting spontaneous deterioration [2]. It is obvious that proper management of arterial disease requires a comprehensive assessment of the underlying vascular morphology. Localizing and gauging the severity of arterial lesions is crucial for therapeutic decision making. For this purpose, several imaging modalities, including conventional catheter angiography, duplex ultrasound, as well as CT- and MR-angiography (MRA) are in clinical use.

To date the display of the peripheral arterial system was accomplished with catheter-based X-ray angiography. High cost, invasiveness and associated risks [3-5] have motivated the development and evaluation of non-invasive peripheral vascular imaging techniques including ultrasound, computed tomographic (CT) angiography, and MR angiography (MRA). MR has advantages relative to CT angiography including the availability of a large field of view, use of non-nephrotoxic contrast material, and lack of ionizing radiation. Compared to ultrasound, MR is less operator-dependent and overcomes difficulties related to acoustic window limitations. Lack of ionizing radiation and safe contrast agents [6], in conjunction with high diagnostic accuracy have driven the rapid implementation of MRA as the modality of choice for assessing arterial disease in many centers throughout the world [7-10].

Since atherosclerotic disease effects the entire arterial system, extended coverage allowing the concomitant assessment of the arterial system from the supraaortic arteries to the distal runoff vessels appears desirable. Subsequent parenchymal enhancement and contrast dose limitations had initially curtailed contrast-enhanced 3D MRA to the display of the arterial territory contained within a single field-of-view extending over 40-48 cm.

The implementation of "bolus chase" techniques extended coverage to encompass the entire run-off vasculature, including the pelvic, femoral, popliteal and trifurcation arteries [11-14, see chapter VII.2. The implementation of faster gradient systems has laid the foundation for a further extension of the bolus chase technique: whole body coverage extending from the carotid arteries to the run-off vessels with 3D MRA has become possible [15].

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Essentials of Human Physiology

Essentials of Human Physiology

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