MRI Protocol for Vascular Anomalies 
 
 1  T1 weighted spin echo (axial - coronal - sagittal)
 2  T2 weighted fat-sat spin echo or IR (axial - coronal - sagittal)
 3  Gradient-echo axial (TOF) w/o saturation slab
 4  Pre- & post-contrast MR Angiography (multiple phases) (gradient echo sequence)
 5  Post-contrast fat-sat T1 weighted spin echo (axial - coronal - sagittal)

 

       MRI INTERPRETATION:

  • T2 weighted images (MRI) reveals the size and extent of the lesion
  • Differentiation between high- and low-flow anomalies can be made based on gradient-echo images (if you see high-signals within the lesion it is a high-flow anomaly (e.g. AVM, AVF, hemangioma), if there are no hyperintensities, then it is a low-flow flow anomaly such as venous malformation or lymphatic malformation
  • MR angiography reveals the vascular architecture - early phase shows the arterial tree and delayed phases show the venous abnormalities and the venous drainage of the lesion
  • Differentiation between venous malformations and lymphatic malformations can be made based on post-contrast T1 images - if the lesion enhances it is a venous malformation, if it shows very minimal peripheral enhancement or no enhancement, it is a lymphatic malformation 

  

Axial post-contrast T1W spin echo image showing multiple rounded cystic lesions in the left axillary region with peripheral enhancement (characteristic enhancement pattern for macrocystic lymphatic malformations)

   

 
                                                      T2 WEIGHTED & POST-CONTRAST IMAGES

 

Discussion (All cases are venous malformations): All vascular lesions (vascular birthmarks) are hyperintense significantly and demonstrate sharp but irregular margins. With these images only, differentiation between venous and lymphatic malformation can not be made. T2 weighted images are very helpful to evaluate the extent of the lesion. These lesions typically enhance when IV contrast is administered. If there is no contrast enhancement or only minimal peripheral enhancement, lymphatic malformation should be considered.

Figure 1: This is a relatively large venous malformation in the popliteal area. The lesion demonstrates typical inhomogeneous contrast enhancement (Venous Malformation). This is not an arteriovenous malformation, because there is a mass-like lesion. AVMs usually demonstrate multiple small signal voids due to high-flow vessels in it without any mass-like lesion. Lymphatic malformations, on the other hand, demonstrate no contrast enhancement or minimal peripheral enhancement (see above). Figures 2 and 3: MR Angiography (or MRA) is quite helpful to demonstrate the vascular architecture. In this example, contrast-enhanced magnetic resonance angiography demonstrates early opacification of a small low-flow anomaly (venous malformation or "cavernous hemangioma") in the hand with progressive filling of the entire lesion on the delayed phase imaging. Due to high sensitivity of the MR contrast material, low-flow lesions can easily be demonstrated with contrast-enhanced MRA.

 

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