The Doppler signal: where does it come from and what does it mean?

Department of Radiology, University of California, San Diego, La Jolla 92093.

Doppler sonographic measurement of blood velocity and associated physiologic parameters is a powerful diagnostic technique. State-of-the-art instrumentation incorporates velocity measurement with two-dimensional imaging capability; it uses intensity and color coding to display complex physiologic and anatomic data to the observer in an easily understood format. Although the concepts underlying Doppler sonography are not complex, mastery of the technique requires extra training and commitment. The principal features and clinical practicalities associated with Doppler sonography are summarized in the following paragraphs. Continuous-wave Doppler is very sensitive to small vessels and has no upper velocity limit. In addition, the instrumentation is not complex and produces relatively low acoustic power. A significant drawback to continuous-wave Doppler is that there is no depth sensitivity, and thus complex structures or multiple vessels can give conflicting information. Pulsed Doppler (including duplex and color-flow) instrumentation has the capability of depth resolution and a variable sample volume. Pulsed Doppler equipment is prone to aliasing (false velocity indications) under some circumstances and also produces higher peak power levels than does continuous-wave equipment. Duplex equipment is more complex and expensive than continuous-wave equipment because the two-dimensional and Doppler modes must be synchronized in operation and display. Color-flow equipment is extremely complex and expensive. Color flow provides information of a qualitative and limited quantitative value. Absolute measurement still requires range-gate measurements. Technical and anatomic factors will affect the measured velocity profiles. Thus, it is important to fully appreciate the anatomy of the vessel and the angle between the vessel and the ultrasound beam when making quantitative measurements. Measurements that evaluate the velocity waveform and make use of ratios, such as the pulsatility index, eliminate the need for angular corrections; however, artifacts due to unappreciated anatomic or wall characteristics may lead to incorrect information if all parameters are not fully understood. Doppler sonographic measurements may be used to determine the presence of flow, determine the direction of flow, identify time-varying velocity characteristics, and detect velocity disturbances. Because flow and velocity are related, it is possible to estimate flow from velocity measurements with careful calibration and proper precautions. Velocity is related to flow, which, in turn, is related to both pressure and vascular resistance.(ABSTRACT TRUNCATED AT 400 WORDS)
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				W. P. Martins, C. O. Nastri, R. A. Ferriani, and F. M. Filho Brachial Artery Pulsatility Index Change 1 Minute After 5-Minute Forearm Compression: Comparison With Flow-Mediated Dilatation J. Ultrasound Med., May 1, 2008; 27(5): 693 - 699. [Abstract] [Full Text] [PDF]

				G. B. Chavhan, D. A. Parra, A. Mann, and O. M. Navarro Normal Doppler Spectral Waveforms of Major Pediatric Vessels: Specific Patterns RadioGraphics, May 1, 2008; 28(3): 691 - 706. [Abstract] [Full Text] [PDF]

				T. Yoshimura, E. Suzuki, K. Egawa, Y. Nishio, H. Maegawa, S. Morikawa, T. Inubushi, A. Hisatomi, K. Fujimoto, and A. Kashiwagi Low Blood Flow Estimates in Lower-Leg Arteries Predict Cardiovascular Events in Japanese Patients With Type 2 Diabetes With Normal Ankle-Brachial Indexes Diabetes Care, August 1, 2006; 29(8): 1884 - 1890. [Abstract] [Full Text] [PDF]

				T. Fukuhara and K. Hida Pulsatility index at the cervical internal carotid artery as a parameter of microangiopathy in patients with type 2 diabetes. J. Ultrasound Med., May 1, 2006; 25(5): 599 - 605. [Abstract] [Full Text] [PDF]

				H. R. Tahmasebpour, A. R. Buckley, P. L. Cooperberg, and C. H. Fix Sonographic Examination of the Carotid Arteries RadioGraphics, November 1, 2005; 25(6): 1561 - 1575. [Abstract] [Full Text] [PDF]

				H. Ota, K. Takase, H. Rikimaru, M. Tsuboi, T. Yamada, A. Sato, S. Higano, T. Ishibashi, and S. Takahashi Quantitative Vascular Measurements in Arterial Occlusive Disease RadioGraphics, September 1, 2005; 25(5): 1141 - 1158. [Abstract] [Full Text] [PDF]

				H. Yildirim, S. Gungor, M. M. Cihangiroglu, and A. D. Aygun Doppler Studies in Normal Kidneys of Preterm and Term Neonates: Changes in Relation to Gestational Age and Birth Weight J. Ultrasound Med., May 1, 2005; 24(5): 623 - 627. [Abstract] [Full Text] [PDF]

				J. W. Olin, J. A. Kaufman, D. A. Bluemke, R. O. Bonow, M. D. Gerhard, M. R. Jaff, G. D. Rubin, and W. Hall Atherosclerotic Vascular Disease Conference: Writing Group IV: Imaging Circulation, June 1, 2004; 109(21): 2626 - 2633. [Full Text] [PDF]

				N.J. Raine-Fenning, B.K. Campbell, N.R. Kendall, J.S. Clewes, and I.R. Johnson Quantifying the changes in endometrial vascularity throughout the normal menstrual cycle with three-dimensional power Doppler angiography Hum. Reprod., February 1, 2004; 19(2): 330 - 338. [Abstract] [Full Text] [PDF]

				J. Krejza, Z. Mariak, E. R. Melhem, and R. J. Bert A Guide to the Identification of Major Cerebral Arteries with Transcranial Color Doppler Sonography Am. J. Roentgenol., May 1, 2000; 174(5): 1297 - 1303. [Full Text] [PDF]

				W. R. Hedrick and D. L. Hykes A Simplified Explanation of Fourier Analysis Journal of Diagnostic Medical Sonography, November 1, 1992; 8(6): 299 - 308. [Abstract] [PDF]

				W. R. Hedrick and D. L. Hykes Color Doppler Imaging: Imaging Parameters and Image Quality Journal of Diagnostic Medical Sonography, July 1, 1992; 8(4): 180 - 186. [Abstract] [PDF]