Metal artifact reduction around cervical spine implant using diffusion tensor imaging at 3T: A phantom study

• Published in: Magnetic resonance imaging Vol. 105; pp. 57 - 66
• Main Authors: Tounekti, Slimane, Alizadeh, Mahdi, Middleton, Devon, Harrop, James S, Hiba, Bassem, Krisa, Laura, Mekkaoui, Choukri, Mohamed, Feroze B
• Format: Journal Article
• Language: English
• Published: Netherlands 01.01.2024
• Subjects: Cervical Vertebrae - diagnostic imaging; Cervical Vertebrae - surgery; Diffusion Magnetic Resonance Imaging - methods; Diffusion Tensor Imaging - methods; Echo-Planar Imaging - methods; Humans; Spinal Cord; Geometric distortion; 3 Tesla; Metal implant; Metal artifacts; Diffusion tensor imaging
• ISSN: 0730-725X; 1873-5894
• DOI: 10.1016/j.mri.2023.11.007

Diffusion MRI continues to play a key role in non-invasively assessing spinal cord integrity and pre-operative injury evaluation. However, post-operative Diffusion Tensor Imaging (DTI) acquisition of patients with metal implants results in severe geometric distortion. We propose and demonstrate a method to alleviate the technical challenges facing the acquisition of DTI on post-operative cases and longitudinal evaluation of therapeutics. The described technique is based on the combination of the reduced Field-Of-View (rFOV) strategy and the phase segmented EPI, termed rFOV-PS-EPI. A custom-built phantom based on a cervical spine model with metal implants was used to collect DTI data at 3 Tesla scanner using: rFOV-PS-EPI, reduced Field-Of-View single-shot EPI (rFOV-SS-EPI), and conventional full FOV techniques including SS-EPI, PS-EPI, and readout-segmented EPI (RS-EPI). Geometric distortion, SNR, and signal void were assessed to evaluate images and compare the sequences. A two-sample t-test was performed with p-value of 0.05 or less to indicate statistical significance. The reduced FOV techniques showed better capability to reduce distortions compared to the Full FOV techniques. The rFOV-PS-EPI method provided DTI images of the phantom at the level of the hardware whereas the conventional rFOV-SS-EPI is useful only when the metal is approximately 20 mm away. In addition, compared to the rFOV-SS-EPI technique, the suggested approach produced smaller signal voids area as well as significantly reduced geometric distortion in Circularity (p < 0.005) and Eccentricity (p < 0.005) measurements. No statistically significant differences were found for these geometric distortion measurements between the rFOV-PS-EPI DTI sequence and conventional structural T2 images (p > 0.05). The combination of rFOV and a phase-segmented acquisition approach is effective for reducing metal-induced distortions in DTI scan on spinal cord with metal hardware at 3 T.