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(Circulation. 2003;107:2165.)
© 2003 American Heart Association, Inc.

Images in Cardiovascular Medicine

Deep Vein Thrombosis Demonstrated by Magnetic Resonance Direct Thrombus Imaging

J. Kelly, MRCP; B.J. Hunt, MD; A. Moody, MD

From the Department of Haematology, St Thomas’ Hospital, London (J.K., B.J.H.), and Department of Academic Radiology QMC, Nottingham (A.M.), UK.

Correspondence to Dr J. Kelly, SpR, Haematology Department, North Wing (4th Floor), St Thomas’ Hospital, London, SE1 7EH, UK. E-mail jameskelly{at}northbrookfm.fsnet.co.uk

Magnetic resonance direct thrombus imaging (MRDTI) is a new application of magnetic resonance technology that capitalizes on the fact that thrombus is associated with a substantial reduction in T1 (spin-lattice relaxation time). A T1-weighted magnetization-prepared 3-dimensional gradient-echo sequence is used with a selective water-excitation radiofrequency pulse to abolish fat signal. The effective inversion time is chosen to null the blood signal, so that thrombus shows up as a high signal on T1-weighted images against a background of suppressed blood and fat without requiring intravenous contrast. The technique is highly accurate for deep vein thrombosis (DVT; Figure 1) and pulmonary embolism (PE) and can be performed using a standard scanner with a lower limb acquisition time of only 7 minutes.

View larger version (121K): [in this window] [in a new window]   Figure 1. Coronal section of calf showing extensive below-knee DVT.

MRDTI has 2 major advantages over conventional imaging modalities. Firstly, direct visualization of thrombus not only overcomes many of the pitfalls of alternative techniques that have either identified thrombus as a filling defect or in terms of surrogate markers, but it also provides additional information about thrombus characteristics. Secondly, simultaneous imaging of the legs and chest allows a comprehensive assessment of thrombus load, minimizing the importance of overlooked subsegmental PE (where the prognosis is that of the source), and potentially facilitating a more titrated approach to treatment.

The high T1 signal is thought to be due to formation of methemoglobin within red cells in thrombus, which has strong paramagnetic properties. Initially, this occurs subjacent to the endothelium before propagating centripetally so that recent thrombus viewed axially exhibits a characteristic target appearance (Figure 2).

View larger version (113K): [in this window] [in a new window]   Figure 2. Axial view from the same patient showing the target sign

Footnotes

The editor of Images in Cardiovascular Medicine is Hugh A. McAllister, Jr, MD, Chief, Department of Pathology, St Luke’s Episcopal Hospital and Texas Heart Institute, and Clinical Professor of Pathology, University of Texas Medical School and Baylor College of Medicine.

Circulation encourages readers to submit cardiovascular images to the Circulation Editorial Office, St Luke’s Episcopal Hospital/Texas Heart Institute, 6720 Bertner Ave, MC1-267, Houston, TX 77030.

This Article Extract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kelly, J. Articles by Moody, A. Search for Related Content PubMed PubMed Citation Articles by Kelly, J. Articles by Moody, A. Related Collections Cardiovascular imaging agents/Techniques Deep vein thrombosis