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Diffusion tensor magnetic resonance imaging of the postoperative spine with metallic implants
Author(s) -
Yang Lian,
Liu Yuan,
Kong Xiangchuang,
Guo Xiaodong,
Liu Xiaoming,
Qi Qian,
Wang Jiazheng
Publication year - 2020
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.4321
Subject(s) - diffusion mri , magnetic resonance imaging , imaging phantom , nuclear magnetic resonance , spinal cord injury , pulse sequence , fast spin echo , spinal cord , nuclear medicine , biomedical engineering , spin echo , gradient echo , materials science , medicine , physics , radiology , psychiatry
There has been a growing need to understand the mechanism of development of acute spinal cord injury (SCI) and to optimize treatment. The paramagnetic nature of metallic implants has hampered the application of diffusion tensor imaging (DTI) in postsurgical SCI monitoring. We describe here a successful implementation of spinal DTI in postsurgical SCI patients. Data were acquired using a single‐shot turbo‐spin‐echo sequence, where an extra gradient is applied before the refocusing pulse train to eliminate contributions from the non‐Carr‐Purcell‐Meiboom‐Gill components following a diffusion preparation block where a single‐spin echo scheme is deployed. The DTI images were acquired in axial orientation with a 2 x 2 x 4 mm 3 resolution and a total of 18 slices. Diffusion gradients were applied in six directions with b values of 0 and 600 seconds/mm 2 . The whole scan took ~10 minutes. The sequence was compared with SENSE‐DW‐EPI and ZOOM‐DW‐EPI on a phantom, eight patients with either anterior or posterior titanium alloy implants, and a pork loin with a similar implant. The protocol resulted in dramatically reduced geometric distortions compared with routine imaging sequences, however, the SNR efficiency was compromised. The spinal cord signal displacement was 0.68 ± 1.00 mm (mean ± SD, n = 8) for the proposed protocol, and 5.14 ± 3.07 and 2.82 ± 1.60 mm for the SENSE‐DW‐EPI and ZOOM‐DW‐EPI sequences, respectively. Fiber tracking was achieved in the presence of implants, which in one case was accompanied by central spinal cord caviation. Mathematical analysis concluded that the proposed protocol would be generally applicable in the spinal cord when the titanium alloy implant is ~15 mm away (<0.5 kHz B 0 field drift). The protocol described is capable of DTI in postsurgery SCI patients with metallic implants at sufficient resolution and SNR.