Venous thrombosis: clinical and experimental MR imaging.

Abstract

Five venous thrombi were induced in the external jugular veins of three laboratory dogs, and were repeatedly imaged over 3 weeks using a 0.35-T magnetic resonance (MR) imager. MR magnitude and phase images, T1 and T2 relaxation times, venography, and histologic sections of these thrombi were evaluated to determine the changes in appearance on MR images with time. Venous thrombi appeared hyperintense compared with muscle on both relatively T1- and T2-weighted spin-echo sequences regardless of the age of the clot. Organization of the thrombus beyond 1 week was manifested as increased prominence of flow signal void in and around the clot. Distinction between intraluminal thrombus and flow-related artifacts was aided by phase image reconstruction. Nineteen venous thrombi locations in 13 patients revealed an MR appearance similar to that of the experimental animal model. Three patients (six thrombi locations) had serial examinations over 4 weeks. No significant change in thrombus signal characteristics was noted with time. It is concluded that MR imaging at 0.35 T cannot be used to predict the age of thrombus (up to 3 weeks) but may be helpful in following its resolution.

Cerebral venous thrombosis in systemic lupus erythematosus.

“…Diagnosis is based only rarely on CT alone, usually on angiography 1 -8 and more recently on MRI, which is now the study of choice if available. 9 Manifestations of SLE are similar in our patients and in the five cases reported previously. There is an increased tendency to arterial and venous thrombosis, especially when lupus anticoagulant is present.…”

Experimental venous thrombi: MRI characteristics with histopathological correlation

“…To our knowledge, venous thrombus models in previous in vivo studies have been induced with thrombin injection or electric stimulation [16][17][18] and have shown signal patterns that are different from our study. It is possible that the thrombi observed in those studies have mainly consisted of platelets and fibrins [22].…”

“…Stasis seems to play the most important role in thrombus formation based on the physiological and anatomical venous character [15]. In vivo studies with animal models of venous thrombosis using MRI have already been reported [16][17][18]. In those studies, venous thrombi were induced by thrombin injection or by electric stimulation to the vessel.…”

“…Although various methods have been designed for venous thrombus induction based on the Virchow's triad [16][17][18][19][20][21][22], the majority of them produced thrombi by direct injection of coagulant factors or mechanical and/or chemical vessel wall damage. Stasis, however, is the most fundamental predisposing factor to venous thrombus formation.…”

Direct contrast-enhanced 3D MR venography

“…Non-enhanced two-dimensional (2D) time-of-flight (TOF) MRA has long been employed for assessment of the deep venous system [24,25,26]. The technique's limited clinical impact mainly reflects lengthy acquisition times in combination with the inability to reliably display superficial and small deep veins in the calf [27].…”