PubMed · 348017
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I M Ledingham. 1978. Shock.. https://pubmed.ncbi.nlm.nih.gov/348017/
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Catheter intravascular imaging is currently used as an adjunct to contrast angiography and angioscopy in peripheral and coronary arteries. At present the smallest catheters are 3.0 F (1.0 mm). Frequencies used are from 10 to 40 Mz, which allow high resolution imaging of structures close to the transducer. Mechanical and phased array systems are used, introduced either on the wire or through fine plastic catheter. More recent is the monorail system improving the flexibility and tracking of the mechanical systems. The review presents current status of catheters and diagnostic possibilities. Normal arteries have typical three layered appearance (intima, media, adventitia). Ultrasound can be reliably used to distinguish abnormal vascular segments. Atherosclerotic plaques can be subclassified on the basis of plaque composition. Thrombus is characterized by granular appearance with varying sonographic gray levels. Dissection and intimal flaps are also visualized by intravascular ultrasound. Potential utility of intravascular ultrasound in the assessment of endovascular interventions and its limitations are discussed.
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A new angiography technique using the susceptibility effect is proposed. Blood containing deoxyhemoglobin is more paramagnetic than surrounding tissue and thereby produces a susceptibility effect at blood-tissue interfaces. By use of a specially tailored RF pulse, signals from normal tissues are suppressed while the signals from blood interfaces, where strong susceptibility-induced fields are created, are enhanced. The design and characteristic behavior of the tailored RF pulse are discussed and experimental results obtained using both a phantom and a human volunteer with a 2.0-T whole-body NMR system are also presented.