Peer-Review ReportClinical Applications of Diffusion Tensor Imaging
Section snippets
Basic Principles
Diffusion-weight imaging (DWI) relies on proton diffusion as a contrast-determining parameter in magnetic resonance imaging (MRI). In DWI, a spin-echo sequence with a pair of strong diffusion-weighted gradients is used, known as the Stejskal-Tanner pulse sequence (120). The diffusion-weighting applied is dependent on multiple factors represented by the diffusion attenuation factor or b-value. A conventional DWI sequence evaluates diffusion in all directions. In contradistinction, diffusion
Challenges
Phase effects resulting from coherent macroscopic or bulk motion present a great technical challenge for DWI. DWI pulse sequences must be sensitive to microscopic molecular motion, but this sensitivity also causes signal loss, phase changes, and ultimately ghost artifacts when there is any motion from either cardiac pulsatility or patient movement during the diffusion-encoding periods. Single-shot methods, such as single-shot echo planar imaging (EPI), are used to prevent phase variation
Brain Tumors
Minimizing damage to the eloquent cortex and white matter tracts while maximizing surgical resection of brain tumors remains a challenge, especially when the white matter tracts are displaced or infiltrated by tumor. Directional color-coded FA maps and DTI fiber tractography may be useful adjuncts to conventional MRI of the brain for presurgical planning and intraoperative guidance in regions adjacent to functional tracts. MR acquisitions suitable for DTI tractography include contiguous slices
Conclusions
Advanced imaging techniques such as DTI have proven useful in providing additional anatomical information for the neurosurgeon to guide the surgical approach, particularly in the setting of brain and spinal tumors. However, DTI techniques, particularly DTI tractography, should be applied with caution and recognition of their limitations. New techniques such as HARDI fiber tractography and intraoperative MRI may improve accuracy of tract localization. DTI has also been shown to be a promising
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Conflict of interest statement: Dr. Meng Law's financial disclosures include Prism Medical Imaging (consultant), Seimens Medical Solutions (Speakers' Bureau), and Bayer Healthcare (Speakers' Bureau). The remaining authors have no conflicts to report.