High‐resolution blood flow velocity measurements in the human finger

Abstract

MR phase contrast blood flow velocity measurements in the human index finger were performed with triggered, nontriggered, and cine acquisition schemes. A strong (G max ‫؍‬ 200 mT/m), small bore (inner diameter 12 cm) gradient system inserted in a whole body 3 Tesla MR scanner allowed highresolution imaging at short echo times, which decreases partial volume effects and flow artifacts. Arterial blood flow velocities ranging from 4.9 -19 cm/sec were measured, while venous blood flow was significantly slower at 1.5-7.1 cm/sec. Taking into account the corresponding vessel diameters ranging from 800 m to 1.8 mm, blood flow rates of 3.0 -26 ml/min in arteries and 1. Phase contrast (PC) MRI to quantify blood flow velocities has been validated in several studies (1-3). Most human applications focus on large vessels such as the aorta, carotids, or femoral arteries. This is due to the fact that systematic errors strongly increase with decreasing number of image pixels that cover the vessel lumen under investigation (4,5). Models that correct for partial volume effects have been developed which allow the acquisition of flow velocity values from vessels covered by only a few pixels (6 -8). In this study, a different approach was performed to overcome problems associated with partial volume effects. We used a strong gradient system that allows high-resolution phase contrast MRI of the human finger. In our experiments, the main vessels of the human index finger were covered by at least 16 pixels, which is sufficient to keep systematic errors due to partial volume effects small (4). So far, in vivo MRI investigations of the human distal extremities have been limited to morphologic imaging of skin layers, joints, and vessel anatomy (9 -12), not including functional parameters. Commonly, blood flow velocities in the human distal extremities are obtained by ultrasound (US) investigations (13,14). US flow measurements have the advantage of being fast and flexible; on the other hand, they do not provide detailed anatomic information. The information about the patency of large vessels is a cardinal aspect in the assessment of general arteriosclerosis in tissues (15). However, little is known about the role of smaller arteries. Although their general functionality can be tested by a number of simple physical tests (e.g., exercise), these tests still provide us with no visual information on vessel size or orientation. For planning distal reconstructive surgery in cases of severe arteriosclerosis, a vital role could be played by the combination of functional information (e.g., blood flow velocity) and complementary 3D images of individual vessels. Such information could also be helpful in staging general and/or microangiopathy of distal body parts. To our knowledge, we performed the first MR blood flow velocity measurements in human peripheral vessels with diameters as low as 800 m without the need to correct for partial volume effects. MATERIALS AND METHODSBlood flow velocities were measured in the index fingers of five healthy male s...

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