Evaluating the Utility of a Postprocessing Algorithm for MRI Evaluation of Optic Neuritis

Preliminary findings of a 'test bundle' to accelerate the diagnosis of MS and NMOSD following optic neuritis

No study has investigated the length of time it takes to diagnose multiple sclerosis (MS) or neuromyelitis optic spectrum disorder (NMOSD, aquaporin 4 antibody disease or myelin oligodendrocyte glycoprotein antibody disease, MOGAD) following the onset of de novo optic neuritis (ON). Minimizing the time between ON and downstream diagnoses needs urgency since early diagnosis equals early treatment. The time elapsed from ON to a subsequent diagnosis of MS/NMOSD was estimated through analysis of retrospective data collected from the Axon Registry (AR) of the American Academy of Neurology (AAN) and from the University of Kentucky (UK), Lexington. The time to diagnose MS/NMOSD was arbitrarily set as occurring < 6 months (early) or > 6 months (delayed) following ON. Data was collected between 2007 and 2021 (AR) and 2012 to 2022, for UK, respectively. Of the 4015 ON patients from the AR dataset, 1069 (26.6 %) were diagnosed with MS, with 857 (80.2 %) diagnosed < 6 months (early) and 212 (19.8 %) diagnosed after > 6 months (delayed). Secondly, 420/4015 (10.4 %) were diagnosed with NMOSD (either MOGAD or AQP4 antibody disease), of which 340/420 (80.9 %) were diagnosed < 6 months (early) and 80/420 (19 %) diagnosed > 6 months (delayed). In the UK dataset, a total of 90/1464 individuals (6.14 %) were diagnosed with MS; of these, 69 patients (76.7 %) were diagnosed at < 6 months (early) and included a sub-group of 25 (27.8 %) diagnosed < 4 weeks; 21 (23.3 %) were diagnosed > 6 months (delayed) following ON. In either dataset (AR or UK, between 20 % - 23 % of MS diagnoses occurred > 6 months (delayed) after a diagnosis of ON. An accelerated diagnosis (4 weeks or less) of MS/NMOSD following ON in the UK data suggests that it is possible to minimize the time to a downstream diagnosis if a 'test bundle' of MRI of orbits, brain, C-spine, cerebrospinal fluid (CSF) analysis, and serum testing for NMOSD is used. Additional studies using prospective, larger datasets are required to confirm our findings.

Delineation of Inner Annulus Fibrosus and Nucleus Pulposus on Routine T2-weighted MR Images

STUDY DESIGN

Retrospective study of 150 IVDs.

OBJECTIVE

Assessment of costume algorithm ability to delineate the IAF and NP on routine T2 images.

SUMMARY OF BACKGROUND DATA

Central hyperintense region on T2-weighted MR images of normal lumbar IVDs represents a combination of IAF and NP. Ability to identify NP as distinct from IAF can help improve our understanding of IVD morphology in-vivo.

METHODS

Sagittal T2-weighted TSE MR images of 150 lumbar IVDs from 25 patients were analyzed. MR images were processed using a custom algorithm that markedly increased the signal intensity of structures with inherent signal intensity within 2 defined intensity thresholds. Signal intensity and contrast-to- noise ratio between outer annulus fibrosus, IAF, and NP were assessed at baseline and after processing. To assess consistency of underlying T2 differences, similar analysis was done on 108 discs from 18 patients in whom additional sagittal T2-weighted STIR images were available.

RESULTS

Following image processing, apparent IAF and NP were rendered visible in 86% and 84.3% IVDs on T2-weighted TSE and STIR images respectively. While signal intensity of these 2 regions was inherently different (P< 0.001) before processing on TSE and STIR images, their visualization was facilitated by a significant increase (P<0.001) in contrast-to-noise ratio after processing. Nonvisualization of NP was associated with disc degeneration (P<0.001).

CONCLUSION

Inherent differences exist in signal intensities of normal NP and IAF on T2-weighted MR images. Accentuating these differences using image postprocessing techniques can render these 2 structures visible.

Detection of Optic Neuritis on Routine Brain MRI without and with the Assistance of an Image Postprocessing Algorithm

BACKGROUND AND PURPOSE

At times, there is a clinical need for using routine brain MR imaging performed close to the time of onset of patients' visual symptoms to firmly establish the diagnosis of optic neuritis. Our aim was to assess the diagnostic performance of radiologists in detecting optic neuritis on routine brain MR images and whether this performance could be enhanced using a postprocessing algorithm.

MATERIALS AND METHODS

In this retrospective case-control study of 60 patients (37 women, 23 men; mean age, 47.2 [SD, 17.9] years), 2 blinded neuroradiologists evaluated T2-weighted FLAIR and contrast-enhanced T1WI from brain MR imaging for the presence of imaging evidence of optic neuritis. Images were processed using an image-processing algorithm that aimed to selectively accentuate the signal intensity of diseased optic nerves. We assessed the effect of image processing on the contrast-to-noise ratio between the optic nerves and normal-appearing white matter and on the diagnostic performance of the neuroradiologists, including the interobserver reliability.

RESULTS

The average sensitivity of readers was 55%, 56.5%, and 30.0% on FLAIR, coronal contrast-enhanced T1WI, and axial contrast-enhanced T1WI, respectively. Sensitivities were lower in the absence of fat saturation on FLAIR (P = .001) and coronal contrast-enhanced T1WI (P = .04). Processing increased the contrast-to-noise ratio of diseased (P value range = .03 to <.001) but not of control optic nerves. Processing did not improve the sensitivity but improved the specificity and positive predictive value. Interobserver agreement improved from slight to good.

CONCLUSIONS

Detection of optic neuritis on routine brain MR imaging is challenging. Specificity, positive predictive value, and interobserver agreement can be improved by postprocessing of MR images.

Recent advances on optic nerve magnetic resonance imaging and post-processing

The optic nerve is known to be one of the largest nerve bundles in the human central nervous system. There have been many studies of optic nerve imaging and post-processing that have provided insights into pathophysiology of optic neuritis related to multiple sclerosis and neuromyelitis optica spectrum disorder, glaucoma, and Leber's hereditary optic neuropathy. There are many challenges in optic nerve imaging, due to the morphology of the nerve through its course to the optic chiasm, its mobility due to eye movements and the high signal from cerebrospinal fluid and orbital fat surrounding the optic nerve. Recently, many advanced and fast imaging sequences have been used with post-processing techniques in attempts to produce higher resolution images of the optic nerve for evaluating various diseases. Magnetic resonance imaging (MRI) is one of the most common imaging methodologies for the optic nerve. This review paper will focus on recent MRI advances in optic nerve imaging and explain several post-processing techniques being used for analysis of optic nerve images. Finally, some challenges and potential for future optic nerve studies will be discussed.