Technical Note Dynamic MR Venography: An Intrinsic Benefit of Time-Resolved MR Angiography Jiang Du, PhD, 1,3 * Frank J. Thornton, MD, 2 Charles A. Mistretta, PhD, 1,2 and Thomas M. Grist, MD 1,2 Purpose: To investigate the possibility of obtaining dy- namic contrast-enhanced magnetic resonance venography (DCE-MRV) images of the lower extremities. Materials and Methods: Peripheral contrast-enhanced magnetic resonance angiography (CE-MRA) was performed on 20 patients using a time-resolved sequence that com- bined undersampled projection reconstruction (PR) in- plane and Cartesian slice encoding through-plane. The contrast dynamics of distal vessels were depicted. An au- tomated segmentation algorithm based on a contrast ar- rival time (CAT) threshold was used to generate contrast dynamics in the venous system. The signal difference be- tween the vein and artery was measured to evaluate the effectiveness of this technique in isolating the venous con- trast dynamics. Results: The automatically generated image series de- picted the contrast dynamics of both the arterial and ve- nous systems, including asymmetric venous enhancement and background tissue enhancement. Quantitative mea- surement showed a mean venous/arterial signal ratio in- crease from 1.58 to 4.82 for the peak venous frame after arterial signal suppression. Conclusion: DCE-MRV is a minimally invasive technique for evaluating the venous side of the systemic vascular anatomy. Time-resolved MRA has the potential clinical ben- efit of enabling both arterial and venous disease to be de- tected in patients undergoing CE-MRA. Key Words: contrast enhancement; magnetic resonance (MR); dynamic imaging; peripheral vasculature; venogra- phy J. Magn. Reson. Imaging 2006;24:922–927. © 2006 Wiley-Liss, Inc. DEEP VENOUS THROMBOSIS (DVT) has been reported to be a major cause of morbidity and mortality, with 5,000,000 episodes occurring annually in the United States alone (1). Conventional contrast venography continues to serve as a gold standard for diagnosis, but this technique is invasive and not without risks, includ- ing exposure to ionizing radiation, complications asso- ciated with the use of iodinated contrast material, and procedure-induced DVT (2). Duplex sonography has been shown to have both high sensitivity and specificity for femoral and popliteal DVT, but it is operator-depen- dent and has reduced accuracy in the distal lower ex- tremities due to the low volume and flow velocity of blood within the calf veins (3). Magnetic resonance imaging (MRI) has been used to detect DVT of the lower and upper extremities and pel- vis for at least a decade (4 –10). Techniques such as time-of-flight (TOF) and phase contrast (PC) angiogra- phy have been extensively investigated and proven to be reliable for the assessment of the deep venous system (4). However, these methods have limited value for de- picting paired veins, perforating veins, and venous valves below the knee, mostly because of high sensitiv- ity to artifacts caused by complex flow and long scan times (7). Flow-enhanced multishot TOF echo-planar imaging (EPI) can result in better visualization of calf veins by exploiting transient flow-augmenting following the use of venous occlusion, but this technique pro- vides little separation of the arterial venous circula- tions, and suffers from edge blurring due to T2* decay (8). Fast-spin-echo (FSE) techniques have a high sensi- tivity for detecting small veins and arteries with slow flow rates, and a low sensitivity for large veins with high flow rates (9). High signal from edema may lead to suboptimal depiction of the venous anatomy in flow- independent MR venography (MRV) based on inversion- recovery rapid acquisition with relaxation enhance- ment (RARE) sequences (10). Contrast-enhanced (CE) MRV was recently proposed as a means of evaluating the venous anatomy of the extremities (11–15). This technique requires the injec- tion of an extracellular contrast material that shortens the T1 of blood. The arterial system is enhanced during the first pass of the contrast bolus, with subsequent enhancement of venous structures. Single-phase ac- quisition combined with pedal injections of diluted con- 1 Department of Medical Physics, University of Wisconsin–Madison, Wisconsin, USA. 2 Department of Radiology, University of Wisconsin–Madison, Wiscon- sin, USA. 3 Department of Radiology, University of California–San Diego, San Di- ego, California, USA. *Address reprint requests to: J.D., Department of Radiology, University of California–San Diego, 200 West Arbor Drive, San Diego, CA 92103- 8756. E-mail: jiangdu@ucsd.edu Received July 11, 2005; Accepted June 30, 2006. DOI 10.1002/jmri.20716 Published online 6 September 2006 in Wiley InterScience (www. interscience.wiley.com). JOURNAL OF MAGNETIC RESONANCE IMAGING 24:922–927 (2006) © 2006 Wiley-Liss, Inc. 922