Characterization of the magic angle effect in the equine deep digital flexor tendon using a low-field magnetic resonance system.
Abstract: Three isolated equine limbs were imaged with a low-field magnetic resonance system with a vertical magnetic field. Each limb was scanned in multiple positions with mild variation of the angle between the magnetic field and the long axis of the limb. When the long axis of the limb was not perpendicular to the magnetic field, a linear hyperintense signal was present at the palmar aspect of one of the deep digital flexor tendon lobes, at the level of the navicular bone and collateral sesamoidean ligaments, in proton density and T1-weighted pulse sequences. With increased angulation of the limb, the palmar hyperintense signal extended farther distally and proximally and additional signal hyperintensity was present at the dorsal aspect of the distal part of the other lobe of the deep digital flexor tendon. Increased signal intensity was also present in the collateral ligament of the distal interphalangeal joint on the same side as the palmar hyperintense signal in the tendon. The changes in the deep digital flexor tendon are due to the specific orientation of fibers at the palmar and dorsal aspect of the tendon, which is responsible for focal manifestation of the magic angle effect. Careful positioning of the limb perpendicular to the magnetic field can prevent this phenomenon. The association of palmar increased signal intensity in the deep digital flexor tendon with increased signal in the collateral ligament of the distal interphalangeal joint on the same side should be recognized as manifestations of the magic angle effect.
Publication Date: 2009-02-27 PubMed ID: 19241751DOI: 10.1111/j.1740-8261.2008.01486.xGoogle Scholar: Lookup
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- Journal Article
- Anatomy
- Biomechanics
- Clinical Findings
- Clinical Pathology
- Deep Digital Flexor Tendon
- Diagnostic Imaging
- Distal Interphalangeal Joint
- Equine Diseases
- Equine Health
- Equine Science
- Imaging Techniques
- Ligaments
- Magnetic Resonance Imaging
- Musculoskeletal System
- Navicular Bone
- Physiology
- Sesamoid Bones
- Tendons
- Veterinary Medicine
- Veterinary Research
Summary
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This research article details how the orientation of horse limbs during magnetic resonance imaging can influence the characteristics of certain signals within the deep digital flexor tendon and collateral ligaments, due to a phenomenon known as the ‘magic angle effect’.
Magnetic Resonance Imaging and the Magic Angle Effect
- The study focused on using a low-field magnetic resonance imaging system on three isolated horse limbs.
- During imaging, the position of the limbs was altered slightly and the resulting images were examined.
- When the long axis of the limb was not perpendicular to the magnetic field, there was a particularly bright, linear signal (hyperintensity) detected at the palmar aspect of the digital flexor tendon.
- This signal appeared prominently at the level of the navicular bone and collateral sesamoidean ligaments in the proton density and T1-weighted pulse sequences of the MRI.
Changes in Signal Hyperintensity With Limb Angulation
- With an increased deviation in the limb angle relative to the magnetic field, the bright signal extended farther both distally and proximally. There was also additional hyperintensity observed at the dorsal aspect of the distal part of the tendon.
- A similar bright signal was seen in the collateral ligament of the distal interphalangeal joint on the same side as the bright signal in the tendon.
The Magic Angle Phenomenon and Its Implications
- The specific fibre orientation in both the palmar and dorsal aspects of the tendon causes this marked hyperintensity, a focal manifestation of the magic angle effect.
- The magic angle effect can be avoided through careful positioning of the limb perpendicular to the magnetic field during imaging.
- This study highlights the necessity of understanding the association between the increased signal intensity in the digital flexor tendon and collateral ligament as manifestations of the magic angle effect.
- Understanding these associations can help prevent misinterpretations of scanning results, which could potentially lead to incorrect diagnoses.
Cite This Article
APA
Spriet M, McKnight A.
(2009).
Characterization of the magic angle effect in the equine deep digital flexor tendon using a low-field magnetic resonance system.
Vet Radiol Ultrasound, 50(1), 32-36.
https://doi.org/10.1111/j.1740-8261.2008.01486.x Publication
Researcher Affiliations
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California Davis, Davis, CA, USA. mspriet@ucdavis.edu
MeSH Terms
- Animals
- Artifacts
- Cadaver
- Diagnosis, Differential
- Horse Diseases / diagnosis
- Horse Diseases / pathology
- Horses / anatomy & histology
- Lameness, Animal / diagnosis
- Lameness, Animal / pathology
- Ligaments / anatomy & histology
- Ligaments / pathology
- Magnetic Resonance Imaging / methods
- Magnetic Resonance Imaging / veterinary
- Tendon Injuries / diagnosis
- Tendon Injuries / pathology
- Tendon Injuries / veterinary
- Tendons / anatomy & histology
Citations
This article has been cited 2 times.- Trolinger-Meadows KD, Biedrzycki AH, He H, Werpy N. Three-Dimensional Segmentation and in silico Comparison of Equine Deep Digital Flexor Tendon Pathology in Horses Undergoing Repeated MRI Examination. Front Vet Sci 2021;8:706046.
- Schiller J, Huster D. New methods to study the composition and structure of the extracellular matrix in natural and bioengineered tissues. Biomatter 2012 Jul-Sep;2(3):115-31.
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