The ABCs of Patient-friendly MRI of the Abdomen
– Dr. James Fitzgerald
MRI has become an increasingly utilized means of evaluating disease processes in the abdomen. Early difficulties with motion artifact and low resolution have been largely overcome with improvements in imaging techniques and better coil designs. Numerous studies have demonstrated MRI of the abdomen to be both specific and sensitive in diagnosing and characterizing pathology in this area.
MRI has many advantages when compared to CT scan. First, no ionizing radiation is used. This is particularly important in younger patients and those that are pregnant. For lesions which require follow-up, the cumulative radiation dose of serial CT scans can be avoided. Because no ionizing radiation is used, IV contrast-enhanced
images can be obtained in multiple phases (arterial, portal venous and delayed) in all patients. With CT radiation,
dose is multiplied by the number of phases and can be quite high.
Further, tissue contrast is better. MRI is better than CT in its ability to demonstrate lesions which are similar in density. Fat or water suppression and relative signal weightings can be used to further increase conspicuity of lesions and improve characterization.
The IV contrast agent (gadolinium) can often be used in patients allergic to CT scan dye. The incidence of allergy and nephrotoxicity is much lower than that of CT scan dye.
MRI of the abdomen has many currently accepted uses.
These include but are not limited to:
- Clarify indeterminate masses identified on CT or Ultrasound.
- Evaluate indeterminate cystic lesions in the kidneys and pancreas.
- Differentiate adrenal metastasis from adenoma.
- Stage certain malignancies.
- Evaluate diffuse liver disease (fatty infiltration, hemochromatosis, etc.).
- Surveillance for hepatoma in patients with cirrhosis/hepatitis C.
- MRA/MRV to evaluate the arterial and venous structures (including portal vein).
- MRCP to evaluate the biliary ducts and gallbladder.
- Diagnosis of appendicitis in pregnant patients with indeterminate ultrasound.
The standard MRI abdomen protocol can be performed in 25–30 minutes and evaluates all of the previously mentioned indications. For most patients, an MRI scan is safe and well tolerated. A small number of patients are claustrophobic but sedation is available. Certain patients cannot be scanned, particularly those with internal pacer/defibrillators, cochlear implants, certain aneurysm clips and breast tissue expanders. Other implants may be relatively contraindicated and will be reviewed by the technologist. These include middle ear prosthesis, surgical clips,
neurostimulators and orthopedic implants.
In summary, MRI of the abdomen has become an acceptable adjunct and occasional alternative to CT without ionizing
radiation. I predict its use will grow exponentially over the next decade.