Diffusion‐weighted imaging of the human optic nerve: A New approach to evaluate optic neuritis in multiple sclerosis

Abstract

The apparent diffusion coefficient (ADC) in the optic nerve was measured from diffusion-weighted magnetic resonance imaging using an intravoxel incoherent motion (IVIM) sequence. The subjects were seven normal volunteers and eight patients with multiple sclerosis (MS) with a total of four optic nerves with acute neuritis and nine nerves with chronic neuritis. The mean ADC (4.18 +/- 1.13 x 10(-3) mm2/s, n = 9) in the optic nerves with chronic neuritis was significantly higher than that in normal volunteers (1.56 +/- 0.675 x 10(-3) mm2/s, n = 14) and that in the nerves with acute neuritis (0.94 +/- 0.43 x 10(-3) mm2/s n = 4) (P < 0.001). The ADC is useful in assessing MS foci in the optic nerves.

Optic nerve diffusion measurement from diffusion-weighted imaging in optic neuritis

“…The ADC was measured from a 1-mm-diameter circular region of interest placed in the center of the nerve. In seven control subjects, the mean ADC was 982 (SD 741) ϫ 10 The results presented here with a higher resolution sequence over more sections suggest that mean ADC of the control subjects and of the healthy contralateral eyes is much more similar to the ADC of white matter in the brain than previous results have suggested (14,15). One year after an attack of optic neuritis, the mean ADC was significantly increased compared with the contralateral healthy optic nerves and control optic nerves.…”

“…Iwasawa et al (15) studied the optic nerves with a spin-echo sequence that had low diffusion weighting (b-factor, 262.05 s/mm 2 ) and cardiac gating for a single section through the orbital optic nerve. Three acquisitions were performed with the diffusion gradients in the x, y, and z directions, respectively.…”

“…The orbital optic nerves (from four sections) were segmented by a blinded observer, from the nondiffusionweighted (b ϭ 0) images, to avoid bias, by using a computerdefined threshold-based contouring technique. Unlike previous studies (eg, Iwasawa et al [15]), the size of each region of interest was allowed to vary between section positions and subjects. The orbital portion was selected because the intracanalicular optic nerve could not always be reliably identified, because of susceptibility induced artifacts from the adjacent bone and air-filled sinuses and it was not possible to reliably segment the intracranial optic nerve from the brain.…”

“…Rapid, high-resolution CSF and fatsaturated single-shot techniques are therefore desirable (13). Nearly all studies to date that have implemented DW imaging in the optic nerve have concentrated on measuring the ADC along a small number of directions (rather than the full diffusion tensor to give FA) because fewer acquisitions are required (12,14,15).…”

Burst excitation for quantitative diffusion imaging with multipleb-values

“…In animal models, measurement of the ADC has been used to evaluate infarct development and to investigate the efficacy of experimental therapies (5)(6)(7)(8). The use of the technique clinically is now becoming routine for the diagnosis of stroke (9,10) and many other conditions (11)(12)(13)(14)(15)(16).…”