Lisette van Dam

Imaging modalities for diagnosing cerebral vein thrombosis 7 121 Non-contrast-enhanced flow related MRI Most studies that evaluated the diagnostic accuracy of non-contrast-enhanced flow related MRI techniques compared to DSA found an adequate sensitivity and specificity for CVT ( Appendix 4 ). 13,55-58 Two studies evaluating non-contrast- enhanced PC MRV found that this technique is sensitive for diagnosing CVT with a sensitivity of 100% and specificity of 71%. 13,57 Notably, DSA was not performed in all study participants. 13,57 The non-contrast-enhanced TOF MRV technique also seems highly reliable for CVT in larger cerebral veins and sinuses. However, this technique was not sensitive for assessing smaller veins (i.e. in branches of cortical veins). 56,58,59 Most studies evaluated the diagnostic accuracy of non-contrast-enhanced flow related MRI techniques compared to the combination of multiple imaging modalities and final clinical outcome or contrast-enhanced MRV ( Appendix 5 ) 21,32,60-69 , were adequate sensitivity and specificity for CVT were found too. Non-contrast-enhanced TOF MRV and PC MRV had a sensitivity of 64-100% and 48-100%, respectively, although with wide 95% confidence intervals. Moreover, non-contrast-enhanced flow related MRI was confirmed to be less accurate for identifying cortical vein thrombosis. 21,65 Native contrast thrombus MRI With native contrast thrombus MRI techniques, a thrombus is directly visualized ( Figure 3 ). In the first 5 days after clot formation, the signal may be isointense on T1-weighted images (T1WI) and hypointense on T2-weighted images (T2WI) as the acute thrombus has a high deoxyhaemoglobin concentration. 2,5,14 Between 6 and 15 days, the clot may appear hyperintense on T1WI and T2WI due to a high methaemoglobin concentration. 2,5 After 15 days the thrombus may appear iso- to hyperintense on T2WI and isointense on T1WI. 2,5 On gradient-recalled echo (GRE) susceptibility weighted (SW) images, deposited blood breakdown products (i.e. methaemoglobin, deoxyhaemoglobin) can cause exaggerated signal drop-out ( Figure 4 ) so that intraluminal thrombi can be depicted in stages where the clot may be subtle in other sequences. 5