Magic Angle Effects

Magic angle effects are seen most frequently in tendons and ligaments that are oriented at about a 55 degree angle to the main magnetic field. Signal from water molecules associates with the tendon collagen fibers is not normally seen because of dipolar interactions that result in very short T2 Times. At an angle of about 55 degrees to the main magnetic field, the dipolar interactions become zero, resulting in an increase of the T2 Times about 100 fold. This results in signal being visible in tedons with ordinary pulse sequences. A bright signal from this artifact is commonly seen in the rotator cuff and occasionally in the patellar tendon and elsewhere. The following image shows increase signal in the distal patellar tendon from this magic angle effect.