Diffusion-weighted MR Imaging of Deep Vein Thrombosis

Abstract

Magnetic resonance (MR) imaging is not commonly used as a diagnostic tool for deep vein thrombosis (DVT). Technological advances in fat saturation pulse sequences and surface coils have enabled the application of diffusion-weighted imaging (DWI) to whole-body imaging, 1 and we applied this technique to detect DVT and evaluated its tissue contrast.To evaluate the extent of DVT in a 60-year-old woman with asymptomatic pulmonary thromboembolism, we performed noncontrast diffusion and T 1 -weighted MR imaging (T 1 WI) of her lower legs after obtaining her informed consent. She underwent MR imaging using a 1.5-tesla superconducting system combined with a 12-channel bodyphased array coil (Signa Excite HDxt; GE Medical Systems, WI, USA). DWI was performed in the transverse plane using single-shot echo planar imaging with fat suppression and short-tau inversion recovery (STIR) within 7 min (repetition time [TR]/echo time [TE]/IR, 10000/65.3/200 ms; field of view (FOV), 480 © 480 mm; matrix, 64 © 128; slice thickness, 7 mm with 1.4-mm overlap; 152 slices; band width, « 125 kHz; number of excitations, 2; phase FOV, 0.5; asset factor, 2; and b values of 1000 mm 2 /s). Coronal maximum intensity projection of DWI (Fig. 1A) showed a lesion with branching high signal intensity (SI) in the right lower limb. In addition, T 1 WI showed a lesion with high SI in the right posterior tibial and soleus veins, which indicated DVT. Axial-merged images showed colocalization of the high SI lesion on DWI and T 1 WI (Fig. 1B). The high SI of the DVT on DWI was compatible with that of a cerebral vein thrombus 2 and over half of the portal vein thrombi. 3 These results suggest that the high SI of venous thrombi on DWI is a characteristic finding. However, the sensitivity and specificity of combined DWI/T 2 -weighted MR imaging were better than those of DWI alone as a screening tool for detecting abdominal malignancies. The merged DWI and T 1 WI images added anatomical and qualitative information to the high SI lesion on DWI. In addition, a lesion of low SI in MR venography may support the diagnosis of DVT. Tumors, inflammatory lesions, and several normal structures in the lower limb (peripheral nerves, lymphatic system, and bone marrow) exhibit impeded diffusion.1 Therefore, careful evaluation of DWI findings along with other MR imaging sequences and clinical and laboratory findings is necessary to reduce false-positive diagnoses.

High Signal Intensity on Diffusion-Weighted Images Reflects Acute Phase of Deep Vein Thrombus

“…17 We also reported that DWI detected DVT as a region of high SI in a symptomatic patient. 18 The present findings are consistent with these previous reports. Favrole et al found high SI on DWI in 41% of patients with recent cerebral venous thrombosis and no high SI in any thrombi on follow-up MRI.…”