How to interpret a Magnetic Resonance Imaging (MRI) scan?

From the Guidelines

To read an MRI, one must first understand the basics of MRI interpretation, including recognizing normal anatomy and identifying abnormalities, and this process should always be performed by trained professionals, such as radiologists or clinicians with expertise in MRI interpretation 1. When interpreting an MRI, it is essential to consider the clinical context and the specific sequences used, such as T1-weighted, T2-weighted, and FLAIR images, as each provides different information about tissue characteristics.

• The process begins with orienting oneself to the anatomical view, which can be axial, coronal, or sagittal.
• Identifying the sequence being examined is crucial, as T1-weighted images show fat as bright (hyperintense) and water as dark (hypointense), while T2-weighted images show the opposite pattern.
• Normal anatomy must be recognized before abnormalities can be detected, and comparison with the opposite side (when applicable) and with previous imaging studies is essential for accurate interpretation. Key considerations in MRI interpretation include:
• Looking for areas of abnormal signal intensity
• Identifying unusual enhancement patterns after contrast administration
• Detecting mass effects or structural abnormalities
• Considering the clinical context and the specific sequences used As emphasized in the guidelines for the use of MRI in multiple sclerosis, the interpretation of MRI scans should be performed by trained (neuro)radiologists or clinicians deeply familiar with the features of multiple sclerosis and disorders considered in the differential diagnosis 1. Furthermore, the 2010 McDonald criteria have substantially improved the diagnostic process in relapsing–remitting MS (RRMS), but they exhibit a number of limitations in primary progressive MS (PPMS) 1. In terms of specific guidelines for reading an MRI, the assessment of lesions on magnetic resonance imaging in multiple sclerosis should follow practical guidelines, including the use of adequate quality MRI studies, with few artefacts and performed on scanners with a minimum field strength of 1.5 T 1. Overall, accurate MRI interpretation requires professional medical training, and patients should always rely on qualified healthcare providers to explain their MRI results rather than attempting to interpret them independently 1.

From the Research

Understanding MRI Results

To read an MRI, it's essential to have a basic understanding of how MRI works and its limitations. According to 2, having a degree of understanding about how MRI works, its limitations, and pitfalls can help optimize what is learned from a scan.

Interpreting MRI Images

Interpreting MRI images can be challenging, especially for complex abnormalities on multiple slices of image datasets with different tissue contrasts. As stated in 3, the detection of musculoskeletal disease on MRI is challenging and often requires analyzing complex abnormalities.

Key Factors in MRI Interpretation

Some key factors to consider when interpreting MRI images include:

• The choice of protocol for MR acquisition and its interpretation, which hinges crucially on the clinical information provided 2
• The use of deep-learning methods for lesion detection, progression, and prediction of musculoskeletal disease, which have shown success in estimating pediatric bone age, detecting fractures, and assessing the severity of osteoarthritis 3
• The comparison of MRI with radiography for detecting structural lesions of the sacroiliac joint, which has shown that MRI is superior to radiography in detecting structural lesions 4

Specific MRI Lesions

Specific MRI lesions, such as bone marrow oedema, erosion, fat lesion, and ankylosis, can be indicative of active inflammatory and chronic structural damages in patients with radiographic axial spondyloarthritis and non-radiographic axial spondyloarthritis. As reported in 5 and 6, these lesions can be used to define a positive MRI for inflammatory and structural lesions typical of axial SpA.

MRI Lesion Cut-Offs

Cut-offs for definite active and structural lesions typical of axSpA have been proposed, including:

• ≥4 SI joint quadrants with bone marrow oedema at any location or at the same location in ≥3 consecutive slices for active lesions 5
• ≥3 SI joint quadrants with erosion or ≥5 with fat lesions, erosion at the same location for ≥2 consecutive slices, fat lesions at the same location for ≥3 consecutive slices, or presence of a deep fat lesion for structural lesions 5