Motion artifact as a pitfall in diagnosis of meniscal tear on gradient reoriented MRI of the knee.

Abstract

Reorientation of the phase and frequency encoding gradients is frequently performed for knee MRI to improve visualization of the cruciate ligaments. This technique allows pulsation artifacts arising from the popliteal vessels to be redirected away from the intercondylar notch. The objective of this study was to evaluate the potential for this method to result in false-positive depictions of meniscal tears based on subtle patient motion. Magnetic resonance imaging of the knee was performed in five patients using gradient reorientation. Repeat examinations were then performed following deliberate instruction to the patients regarding the importance of refraining from moving the extremity. The MRI performed with gradient reorientation demonstrated apparent meniscal tears using standard criteria. However, the repeat examinations following deliberate patient instructions to refrain from moving demonstrated the affected menisci to be normal in all patients. Knee motion during image acquisition may result in ghosting artifacts of relatively high signal intensity structures such as marrow within the femoral condyles and hyaline cartilage along the articular surfaces. These artifacts may traverse the menisci on gradient-reoriented images and result in confusion with meniscal tear. Whereas gradient reorientation is a valuable tool for improving depiction of the cruciate ligaments, one must be aware of the potential for this technique to result in simulation of meniscal tears.