Analysis of Low-Field Magnetic Resonance Imaging Scanners for Evaluation of Knee Pathology Based on Arthroscopy

Abstract

Background:In recent years, few studies have evaluated low-field magnetic resonance imaging (MRI) diagnoses compared with intraoperative findings of the knee.Purpose:To determine the accuracy and sensitivity of low-field MRI scanners in diagnosing pathology of the menisci, cruciate ligaments, and osteochondral surfaces.Study Design:Cohort study (diagnosis); Level of evidence, 2.Methods:MRI examinations without intra-articular contrast were performed on 379 patients for knee pathologies over a 4-year period. The MRI examinations were done using a 0.2-tesla scanner utilizing a dedicated knee coil and read by 1 of 3 board-certified, musculoskeletal fellowship–trained radiologists. Within a mean time of 50 days after MRI, all patients underwent knee arthroscopy performed by 1 of 2 sports fellowship–trained orthopaedic surgeons. Operative notes from the knee arthroscopies were then reviewed by a single independent observer, and the intraoperative findings were compared with the MRI reports.Results:For medial meniscus tears, the sensitivity, specificity, positive predictive value, and negative predictive value were 83%, 81%, 89%, and 71%, respectively. For lateral meniscus tears, the values were 51%, 93%, 84%, and 73%, respectively. For anterior cruciate ligament (ACL) tears, the values were 85%, 94%, 69%, and 97%, respectively. For osteochondral lesions, the values were 8%, 99%, 29%, and 94%, respectively. For posterior cruciate ligament (PCL) tears, the specificity and negative predictive value were 99% and 100%, respectively.Conclusion:Low-field MRI was an accurate tool for evaluation of medial meniscus and ACL tears. However, within the study population, it is not as effective in diagnosing lateral meniscus tears and showed a poor ability to detect osteochondral lesions. More information is needed to properly assess its ability to diagnose PCL tears.

¿Hay correlación entre hallazgos de resonancia magnética y artroscopia en lesiones meniscales de rodilla?

“…En el menisco lateral las cifras fueron de 51, 93, 84 y 73%. 7 Al compararse con el presente estudio, se tuvieron resultados más elevados en cuanto a porcentaje, pero coinciden con la dificultad para realizar el dictamen por imagen del menisco lateral.…”

Metal artefacts severely hamper magnetic resonance imaging of the rotator cuff tendons after rotator cuff repair with titanium suture anchors

“…22 Low field MRI (< 0.5 T), although rarely used at present, is hypothesized to be highly suitable for musculoskeletal imaging. 23,24 Interestingly, Radzi et al 25 found that decreasing the main magnetic field (from 3 T to 1.5 T) resulted in a 16% reduction of metal artefacts. It is expected that low field MRI (0.25 T) would further decrease metal artefacts.…”

The potential of low and high field magnetic resonance imaging to diagnose pathologies near orthopaedic hardware

“…However, an increased main magnetic field is correlated with increased susceptibility artefacts in the presence of orthopaedic hardware (38,39). Traditional attempts to reduce metal artefacts primarily focus on the improvement of settings (e.g.…”

“…However, reduction of the main magnetic field (low-field MRI < 0.5 T) might provide another option that would sufficiently diminish the susceptibility artefacts (38,39). Since high-field MRI provides better spatial and contrast resolution, low-field MRI is seldom used (51).…”

“…However, the magnet construction, coil design, and sequence development are important for accurate imaging (52), and therefore it is currently doubtful whether high-field images are necessarily associated with greater diagnostic power (53). Recently, studies have actually shown that low-field MRI is highly suitable for parts of MSK imaging (39,54). Moreover, it has low purchase and maintenance costs in comparison with high-field MRI, and no special room conditions are necessary for placement (55).…”