MRI

• Indications for Liver MRI
  • Patients are allergic to iodinated contrast agents
  • Lesion detection & characterization
  • Anatomic location
  • Hepatic vascular patency
  • Biliary duct system
     
• MRI has many advantages over CT: high soft tissue contrast resolution (can see smaller lesions), multiple sequences, multiplanar capability, MRA, MRV, MRCP, no radiation, no iodinated contrast�etc.
   
• However, MRI is similar to CT in that it has the same dynamic multiphase contrast enhancement capability.
   
• MRI can be helpful in the characterization of a small (< 2 cm) benign hemangioma that is equivocal on CT.
   
• A wide range of MRI sequences is available for liver imaging thanks to the numerous manipulations of field strength, pulse sequence, and interdependent sequence parameters which can affect image quality.  Since there is little agreement on the best technique, MRI sequences are often unique to the institution.  At UVa, we use the following:
  • Breath hold T1 spoiled gradient echo (In phase and out of phase): can be used to detect fatty liver, fat in HCC, focal fatty infiltration/sparing, adrenal adenomas.
  • Breath Hold T2: can be used to evaluate hemangiomas and cysts.
  • Turbo spin echo with fat sat or STIR
  • HASTE -Half Fourier acquisition single shot turbo spin echo
  • Dynamic Gad T1 (Arterial, portal venous, delayed, timing bolus, or smart prep): can be used to characterize hypervascular lesions.
    
    
• For most techniques, the intensity of normal liver parenchyma is the same as or slightly higher than that of adjacent muscle. Normally, the liver should be brighter than (hyperintense to) the spleen on T1-weighted images and darker than (hypointense to) the spleen on T2-weighted images.