Optimizing knee MRI: 3D proton density turbo spin echo nDixon sequence vs. 2D high-resolution turbo spin echo in half the acquisition time.

OBJECTIVES: The objective of this study was to evaluate the use of a single proton density (PD) new Dixon (nDixon) three-dimensional turbo spin echo (TSE) sequence for comprehensive knee joint assessment. This was achieved by comparing image quality and diagnostic performance with a conventional (PD + T1) two-dimensional TSE knee MRI protocol. MATERIAL AND METHODS: This prospective ethics-approved study included 32 symptomatic subjects who underwent knee MRI on a clinical 3T scanner. Each subject was scanned using a two-dimensional deep-learning reconstruction (DLR)-enhanced TSE protocol, which involved four sequences and required a total time of 12 min and 6 s. This served as the reference standard. In addition, a DLR-enhanced three-dimensional nDixon TSE sequence was used, which required 5 min and 55 s. The signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) of commonly depicted structures as well as common diagnostic findings in knee MRI were compared between the two imaging protocols. RESULTS: The SNRs of bone, cartilage, and muscle were higher with the nDixon than with the conventional TSE images, whereas the SNR of joint fluid was higher with the TSE images (P < 0.001). This resulted in higher CNRs with the TSE than with the nDixon images (P ≤ 0.04). The sensitivities in detecting fractures, ligament tears, and cartilaginous or meniscal lesions did not differ between the two imaging protocols (P ≥ 0.23). CONCLUSION: A single three-dimensional nDixon sequence may be a suitable replacement for a conventional high-resolution TSE imaging protocol in routine knee MRI.