Lisette van Dam

Chapter 6 104 Figure 3. A. Computed tomography, axial image of the abdomen in portal-venous contrast phase after intravenous contrast administration, showing a central luminal contrast defect caused by chronic thrombus in the mesenteric vein (arrow). B. Magnetic resonance imaging (MRI), axial 3D T1 Dixon FFE image of the same patient showing isointense signal intensity in the mesenteric vein (arrow). On MRI, the signal intensity of the filling defect in the mesenteric vein is not increased, indicating chronic thrombus. DISCUSSION In this first phase of the Rhea study the combination of 3D T1 TFE and 3D T1 Dixon FFE sequences was found to be the most optimal for diagnosing and differentiating acute from chronic PVT. Differentiation between acute and chronic PVT is essential as current guidelines recommend different anticoagulant strategies in patients with acute or chronic PVT, though based on (very) low level of evidence. 5 However, with currently available imaging tests, Doppler US, CT venography, and MRI, it is not always possible to accurately differentiate acute from chronic thrombosis. The diagnosis of chronic PVT can be made in cases of morphologic changes such as an atretic portal vein, inflow branches and cavernous transformation of the portal vein, also called portal cavernoma. 20,21 However, it may be impossible to differentiate acute from chronic PVT in the presence of an organized non-occlusive chronic PVT, without these morphologic changes. Furthermore, up to 30% of the PVT cases are detected incidentally in imaging studies performed for other indications in which it is very challenging to determine whether the incidentally observed thrombosis is acute, chronic or even an imaging artefact. 22 MR-NCTI has been shown to be a valuable diagnostic test for the diagnosis of upper extremity DVT, pelvic vein and cerebral vein thrombosis 11,19,23 and was shown to be an accurate, simple, feasible and reproducible diagnostic test in suspected recurrent ipsilateral DVT of the leg. 9 There are some important differences between