Magic angle effect on low field magnetic resonance images in the superficial digital flexor tendon in the equine proximal pastern region.

The research project focused on the impact of the “magic angle effect” on magnetic resonance imaging (MRI) in an area of a horse’s limb. This effect can cause errors or distractions during diagnostic image interpretation. Therefore, understanding its effects on images, specifically of the superficial digital flexor tendon in the equine proximal pastern region, was the main goal of this study.

Research Methodology

• The project involved imaging the proximal pastern region of four cadaver horse limbs, employing a 0.27 Tesla magnet known for its high-resolution imaging sequences frequently used in clinical equine practice.
• The imaging was done in various positions to stimulate the various movements and rotations a horse typically makes. This included neutral, ‘leaning in’, ‘leaning out’, and both internal and external rotations of the distal limb.
• The researchers then described and compared the changes in signal intensity in the superficial digital flexor tendon (SDFT) for each different position.

Results and Findings

• In the simulated ‘leaning in’ and external rotation positions, they found increased signal intensity in the axial and middle thirds of the lateral half of the SDFT when short echo time sequences were used.
• Similarly, simulated ‘leaning out’ and internal rotation positions resulted in increased signal intensity in the axial and middle thirds of the medial half of the SDFT with short echo time sequences.
• Contrarily, there were no, or only mild, inconsistent signal intensity changes with T2 fast spin echo sequences having long echo times.
• The increases in signal intensity are consistent with a position-induced artifact, also known as the ‘magic angle effect’, which has been witnessed in clinical cases before.

Conclusion and Implications

• The research stresses how important it is to pay close attention to the positioning of the equine distal limb during clinical imaging, as the positions can lead to an artifact in the image.
• These findings will ultimately help radiologists become more aware of position-induced artifacts so they can ensure more accurate interpretation of images.