![]() This enables multidisciplinary management of the patient.Īccording to the Chapel Hill Consensus Conference (CHCC) nomenclature in 2012 ( 4), LVV has two primary variants i.e., giant cell arteritis (GCA) and Takayasu arteritis (TA). It retains the advantages of US used elsewhere-it is readily available, uses no ionizing radiation, universal application by radiologists, angiologists and rheumatologists alike. ![]() US plays a crucial role in the imaging and follow up of patients with large vessel vasculitis (LVV) ( 3). The review that follows aims to highlight the various applications of US in imaging of the arterial system. When portrayed in form of a wave pattern, it is known as spectral Doppler ( 2). Because rapidly moving targets such as red blood cells, produce a unique set of echoes, in effect one can visualize blood flow patterns, this is commonly displayed as a color flow map using red and blue (hence the term color Doppler), although this can be altered within a given system. It enables visualizing and quantifying blood flow by analyzing interactions of acoustic pulses with flowing blood within the vessel lumen. The use of Doppler imaging is an extension of B-mode US, using the same basic physics of acoustic energy transmission. Hence a combination of operator and interpretative skills are required in answering a particular clinical question, this is what makes US imaging unique. It poses no radiation risk, is readily available in most clinical settings and is relatively inexpensive. These interactions result in formation of an US image ( 1). Calculated ABI values should be recorded to 2 decimal places.Ultrasound (US) imaging (also known as conventional B-mode) uses equipment that generates acoustic energy that transmit through tissues resulting in interference patterns with tissues within the body.A consistent difference in pressure between the arms greater than 10mmHg is suggestive of (and greater than 20mmHg is diagnostic of) subclavian or axillary arterial stenosis, which may be observed in individuals at risk for atherosclerosis. In normal individuals, there should be a minimal (less than 10 mm Hg) interarm systolic pressure gradient during a routine examination. In calculating the ABI, the higher of the two brachial systolic pressure measurements is used. The ABI value is determined by taking the higher pressure of the 2 arteries at the ankle, divided by the brachial arterial systolic pressure. Repeat both measurements on the opposite leg. Once again, using the Doppler with ultrasound gel, locate the signal, and follow the process described above to measure the PT systolic pressure. The PT signal is detected posterior to the medial malleolus. Next, measure the systolic pressure of the PT artery.Then slowly deflate using the same technique used in the arms until the Doppler signal re-appears. To measure the systolic pressure at the DP artery, inflate the cuff until you no longer hear the signal. Slowly move the Doppler until the strongest signal is heard. Using a standard hand-held Doppler probe and the ultrasound gel, locate the signal from the DP. The Doppler signal of the DP can often be found slightly lateral to the midline of the dorsum of the foot. Place ultrasound gel on the skin overlying the dorsalis pedis (DP) and posterior tibial (PT) arteries in the foot. Place the cuff immediately proximal to the malleoli.When the Doppler signal re-appears, the pressure of the cuff is equal to the brachial systolic pressure. ![]() Then slowly deflate the cuff, approximately 1 mmHg/sec. Inflate the cuff to about 20 mmHg above the expected systolic blood pressure of the patient. ![]() Place the transducer of the handheld Doppler on the gel, and position the transducer to maximize the intensity of the signal. Place the ultrasound gel in the antecubital fossa over the patient's brachial pulse. Place the blood pressure cuff on the arm, with the limb at the level of the heart.
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