Does a patient who has undergone Magnetic Resonance Imaging (MRI) of the chest or back still require a low-dose Computed Tomography (CT) scan for screening purposes?

From the Guidelines

Having an MRI of the chest or back does not automatically eliminate the need for a CT screening, as these imaging techniques serve different purposes and provide different types of information. The decision to perform a CT scan after an MRI depends on what condition is being evaluated, what the MRI revealed, and what additional information is needed for diagnosis or treatment planning. For example, if a patient had an MRI for back pain that showed a spinal abnormality, but there's concern about possible lung nodules, a chest CT would still be necessary, as low-dose CT has been shown to decrease the mortality rate from lung cancer 1.

Key Considerations

• MRI excels at showing soft tissue detail, while CT scans are better at visualizing bone structures, lung tissue, and certain types of abnormalities.
• The American College of Radiology Appropriateness Criteria recommend lung cancer screening with low-dose CT for patients between the age of 55 and 80 with 30 or more pack years smoking history who currently smoke or who have quit within the last 15 years 1.
• For patients who do not meet these criteria but who have additional risk factors for lung cancer, lung cancer screening with low-dose CT is controversial but may be appropriate 1.
• The ordering physician should explain why both tests are needed in a specific case, as radiation exposure from CT scans should be minimized when possible.

Recommendations

• Patients should discuss their specific situation with their healthcare provider to understand if both imaging studies are truly necessary for their particular condition.
• A CT scan may still be necessary after an MRI if there's concern about possible lung nodules or other abnormalities that CT could better characterize.
• The benefits and risks of additional imaging should be carefully weighed, considering the patient's individual risk factors and medical history 1.

From the Research

MRI and CT Screening

• If a patient has had an MRI of the chest or back, they may still need a long CT screening, depending on the specific clinical scenario and the information that needs to be obtained 2.
• MRI has been developed to help overcome the limitations of computed tomography (CT) and nuclear medicine examinations, and it can provide not only morphological, but also functional, physiological, pathophysiological, and molecular information 2.
• However, CT screening is still widely used, especially in lung cancer screening, and it has been shown to be effective in detecting lung cancer and cardiovascular disease in asymptomatic smokers 3, 4.

Diagnostic Performance of MRI and CT

• A systematic review and meta-analysis found that MRI had a good overall performance for detection of pulmonary nodules measuring 4 mm or larger, with a per-lesion sensitivity of 87.7% and a false-positive rate of 12.4% 5.
• The same study found that MRI sensitivity was 98.5% for nodules measuring at least 8-10 mm and 80.5% for nodules less than 8 mm 5.
• Another study found that PET/MRI did not provide advantages in preoperative T- and N-staging in non-small cell lung cancer compared to PET/CT, but it had a comparable sensitivity for detection of FDG-avid lung nodules and nodules over 10 mm 6.

Clinical Implications

• The choice between MRI and CT screening depends on the specific clinical scenario and the information that needs to be obtained 2, 3, 4, 6, 5.
• MRI may be preferred in certain situations, such as when functional or molecular information is needed, while CT may be preferred in other situations, such as when high-resolution images of the lungs are needed 2, 3, 4, 6, 5.