Low‐field Magnetic Resonance Imaging of Early Subchondral Cyst‐like Lesions in Induced Cranial Cruciate Ligament Deficient Dogs

Abstract

Six healthy adult male mongrel dogs underwent cranial cruciate ligament transection in the left stifle. Survey radiography of both stifles and low-field (0.064 T) MRI of the left stifle were performed preoperatively and at 2, 6, and 12 weeks postoperatively. Focal changes in signal intensity were seen with MRI in the subchondral bone of the medial tibial condyle at 2 and 6 weeks postoperatively. At 12 weeks postoperative, a cyst-like lesion was detected using MRI in the subchondral bone of the medial tibial condyle in 4 of 6 dogs and a less defined lesion at this site in the remaining 2 dogs. The cyst-like lesion was spherical in shape and showed typical characteristics of fluid with low signal intensity on T1-weighted images, high signal intensity on T2-weighted images and high signal intensity on inversion recovery images. The lesion was seen in the subchondral bone of the caudal medial and/or middle region of the tibial plateau slightly cranial to the insertion of the caudal cruciate ligament. No subchondral cysts were seen in the tibia on radiographs. Histopathologically, the tibia was characterized by a loose myxomatous phase of early subchondral cyst formation.

Comparison of High-field and Low-field Magnetic Resonance Imaging of Stifle Joint Disorders in Dogs

“…Barrett et al (2009), with high-field MRI, used proton density-weighted (PD-weighted) images in the sagittal plane to evaluate cranial cruciate ligament abnormalities with a sensitivity of 0.93. In addition, in order to improve visibility oblique scans were performed that were aligned to the cranial cruciate ligament regardless of the strength of the magnetic field (Baird et al 1998a, Barrett et al 2009). Other authors used T2-weighted fast spin echo (FSE) sequence due to the difference in signal intensity between the cranial cruciate ligament and synovial fluid.…”

“…The study conducted by Baird et al (1998a) demonstrated that using low-field MRI they could visualize focal changes and cyst-like lesions in the subchondral bone in one of six dogs 2 weeks after cranial cruciate ligament insufficiency and in all the subjects investigated after 12 weeks. The changes were round with low signal intensity on T1-weighted images.…”

“…On inversion recovery and T2-weighted images they had high signal intensity, whereas the peripheral rim had low signal intensity. Changes were localized in the proximal tibial epiphysis (medial tibial condyle, intercondylar eminences) (Baird et al 1998a). In human medicine it was observed that after acute anterior cruciate ligament rupture in the femur and tibia lesions appeared with high signal intensity.…”

“…The image of an intact meniscus is described as a uniformly hypointense triangle on T1-weighted sequences in the dorsal and sagittal planes (Baird et al 1998a). However, during the anatomic study of the meniscus in the low magnetic field heterogeneous signal increase in the center was observed.…”

“…It was a new way of imaging characterized by better contrast resolution of a soft tissue in comparison with traditional radiography (Baird et al It is assumed that low-field magnetic resonance has a field strength of between 0.2T and 0.4T (Konar and Lang 2011). Other authors reported less than 0.15 T (Baird et al 1998a) or 0.15T to 0.3T (Sabiston et al 1987, Martig et al 2007). Whereas high-field magnetic resonance has a magnetic strength of 1 to 1.5T (Nolte-Ernsting et al 1996, Libicher et al 2005 or higher.…”