Abstract
PURPOSE: To assess the accuracy of 7-Tesla (T) magnetic resonance imaging (MRI) compared with standard-of-care (SOC) 1.5- or 3-T MRI in detecting and grading cartilage defects in the knee. METHODS: Participants who already underwent SOC MRI at 1.5- or 3-T and provided consent were scheduled for 7-T MRI prior to arthroscopy for all indications except revision surgery. SOC and 7-T MRI scans were independently reviewed in randomized order by 2 blinded musculoskeletal radiologists using a modified Outerbridge classification system for defect grading. Image quality (sharpness, contrast, artifact, noise) was also rated. At the time of arthroscopy, each articular surface was then graded by the surgeon, who was blinded to the 7-T MRI scans. Using arthroscopy as the gold standard, we calculated the sensitivity and specificity of SOC MRI and 7-T MRI, as well as inter-rater reliability. RESULTS: A total of 81 patients-41 female patients (aged 45 ± 14 years) and 40 male patients (aged 40 ± 14 years)-were enrolled. The average time between SOC and 7-T MRI was 69 days, and the average time between 7-T MRI and surgery was 6 days. Sharpness, contrast, and noise ratings were all significantly improved with 7-T MRI compared with SOC MRI (P < .05). Seven-Tesla MRI had higher sensitivity but lower specificity in detecting cartilage defects for all 6 articular surfaces (patella, trochlea, lateral femoral condyle, medial femoral condyle, lateral tibial plateau, and medial tibial plateau) when using arthroscopy as the gold standard. Intraoperative cartilage grading was significantly closer to 7-T grading compared with SOC grading for 2 of 6 surfaces (P < .05). Seven-Tesla MRI had reduced coefficient-of-variation values for 1 articular surface (medial femoral condyle) compared with 3-T MRI (P = .036). There were no significant differences in other coefficient-of-variation measures or interobserver reliability with 7-T MRI compared with SOC MRI. CONCLUSIONS: Seven-Tesla MRI showed improved imaging quality metrics and increased sensitivity but decreased specificity in diagnosing cartilage defects in the knee compared with SOC 1.5- and 3-T MRI using arthroscopy as the gold standard. LEVEL OF EVIDENCE: Level II, prospective comparative diagnostic accuracy study.