How do you interpret a Magnetic Resonance Imaging (MRI) scan for an adult patient with no significant medical history?

How to Interpret an MRI Scan

Yes, interpreting an MRI requires systematic evaluation of multiple sequences in conjunction with clinical context, anatomic knowledge, and understanding of technical principles—not relying on any single image type alone.

Fundamental Interpretation Principles

MRI interpretation must integrate multisequence analysis including diffusion-weighted images (DWI with low and high b-values), apparent diffusion coefficient (ADC) maps, anatomic T1- and T2-weighted images, and relative fat fraction images, using image linking and scrolling workstation facilities 1. Reading MRI scans should always be done in the appropriate clinical context, with the premise that interpreters have basic knowledge of what constitutes a lesion 1.

Essential Technical Requirements

• Lesion definition requires the largest linear measurement to be ≥3 mm in at least one plane 1
• Image quality must be of a high standard and lesion identification should be performed by trained, expert personnel 1
• A conservative approach in identifying lesions should be adopted to avoid false-positive findings 1

Systematic Evaluation Algorithm

Step 1: Assess Image Quality and Sequences Available

• Verify that appropriate sequences are present for the clinical question 2
• Check for motion artifacts, which can degrade diagnostic quality 3
• Confirm adequate field strength (≥1.5 Tesla for most diagnostic purposes) 3

Step 2: Multisequence Integration

Never rely on a single sequence type 1. The interpretation requires:

• T1-weighted images: Best for anatomic detail and detecting hemorrhage, fat, and melanin 4, 5
• T2-weighted images: Optimal for detecting edema, inflammation, and most pathology 4, 5
• FLAIR sequences: Suppress CSF signal to better visualize periventricular and cortical lesions 1
• DWI/ADC maps: Essential for detecting acute ischemia, abscesses, and cellular tumors 1
• Susceptibility-weighted imaging (SWI/T2)*: Detects hemorrhage, calcification, and iron deposition 2

Step 3: Contrast Enhancement Evaluation (When Available)

Contrast administration reveals disruption of the blood-brain barrier and is critical for specific diagnoses 2:

• Tumor characterization: Contrast is crucial for demonstrating leaky vasculature and defining tumor extent 2
• Metastases detection: Essential for identifying small metastatic lesions 2
• Inflammatory/infectious processes: Helps distinguish active inflammation from chronic changes 2

Important caveat: The FDA has issued safety communications regarding gadolinium deposition in the brain after repeated administrations, though clinical significance remains uncertain 1.

Step 4: Anatomic Region-Specific Approach

Brain/Spine Evaluation 1:

• Systematically review all anatomic compartments
• Assess for mass effect, midline shift, or herniation
• Evaluate ventricular size and CSF spaces
• Examine cranial nerves when visible

Soft Tissue Assessment 1:

• MRI creates pictures of soft tissue but not bones as well as CT 1
• Superior for evaluating muscles, ligaments, and organs
• Excellent for detecting subtle inflammatory changes

Step 5: Recognize Common Pitfalls

False-positive findings vary by anatomic region 1:

• Bones: Fractures, osteoarthritis, infection, hemangiomas, focal red marrow can mimic malignancy 1
• Brain: Normal variants like prominent perivascular spaces, flow artifacts, and age-related changes 1
• Technical artifacts: Motion, susceptibility artifacts near metal, and flow-related phenomena 3

False-negative considerations 1:

• Background bone marrow hypercellularity in young patients or those with anemia can obscure lesions 1
• Small cortical lesions may be missed on conventional sequences 1
• Slow flow can mimic occlusion or severe stenosis on MRA 3

Clinical Context Integration

The clinical history fundamentally guides interpretation 6, 4:

• Acute presentations: Prioritize evaluation for stroke, hemorrhage, or infection 1
• Chronic symptoms: Focus on degenerative changes, demyelination, or mass lesions 1
• Known malignancy: Scrutinize for metastases or treatment effects 2

Special Interpretation Challenges

Pseudoprogression can mimic tumor progression on conventional MRI, typically occurring 3-6 months post-radiotherapy, and enhancement is not reliable in patients receiving bevacizumab therapy 2. Conventional MRI has modest sensitivity and specificity for differentiating progressive disease from treatment effects 2.

Practical Workflow Considerations

Use advanced visualization tools 1:

• Radial maximum intensity projections (MIP) of high b-value DWI images displayed with inverted grayscale are useful for rapid screening 1
• 3D reconstructions should be reviewed in multiple planes to identify eccentric or focal lesions 3
• Coregistration tools aid in comparing serial studies 1

Patient-specific factors affecting interpretation 7:

• Motion artifacts are common in anxious, claustrophobic, or uncooperative patients 7
• Scan duration (45-60 minutes typical) increases likelihood of motion degradation 1
• Shorter protocols may be necessary but could miss subtle findings 7

Key Takeaway for Clinical Practice

Effective MRI interpretation requires understanding both the physics underlying image generation and the clinical context driving the examination 6, 4, 5. Knowledge of basic physical principles is essential for correct image interpretation 4, and having awareness of MRI's limitations and pitfalls helps optimize what is learned from a scan 6.