Abstract:The optic nerve (ON) is a vital structure in the human visual system and transports all visual information from the retina to the cortex for higher order processing. Due to the lack of redundancy in the visual pathway, measures of ON damage have been shown to correlate well with visual deficits. These measures are typically taken at an arbitrary anatomically defined point along the nerve and do not characterize changes along the length of the ON. We propose a fully automated, three-dimensionally consistent tec… Show more
“…28 Harrigan et al also recently evaluated a fully automated 3D consistent technique based on a high-resolution, heavily T2-weighted, isotropic MRI technique to obtain ON and ONS radii. 29 This technique is more anatomically representative because of its 3D nature.…”
BackgroundImaging assessment of the anterior visual pathway structures, particularly the optic nerves (ON), requires knowledge of normal dimensions. Several studies suggesting techniques and normal ranges have been performed, but most suffer from various methodological flaws. This study is the first to be performed in a South African population.ObjectivesThe aim of this study was to establish normal measurements of the ON, optic nerve sheath (ONS) and optic chiasm (OC) on magnetic resonance imaging (MRI).MethodEighty normal adults between ages of 12 and 65 years were included in this prospective, quantitative, observational, descriptive study to establish normal measurement of the ON, ONS and OC using a T2W 3D MRI sequence. Measurements (width and height) were undertaken by two observers independently.ResultsA total of 80 participants with a mean age of 35 years were studied: 49 females (61.25%) and 31 males (38.75%). There were no statistical differences in the measurements between gender and age correlation. Interobserver agreement was best for larger structures, that is, OC width and intracranial ON width, respectively. The overall mean of OC width was 13.63 mm (range: 11.13 mm–16.92 mm, standard deviation [s.d.] 1.21); intraorbital ON height at 5 mm behind the globe 2.29 mm (range: 1.63 mm–3.33 mm, s.d. 0.43), and intracranial ON width 4.27 mm (range: 2.46 mm–5.19 mm, s.d. 0.53).ConclusionNormal measurements of the anterior visual pathway structures on MRI are best reflected in the larger structures. Interobserver variability was poor for the orbital ON, ONS, intracranial ON height and OC height. We recommend that measurements be obtained for the OC width and intracranial ON width. The overall mean for the OC width is 13.63 mm and intracranial ON width 4.27 mm.
“…28 Harrigan et al also recently evaluated a fully automated 3D consistent technique based on a high-resolution, heavily T2-weighted, isotropic MRI technique to obtain ON and ONS radii. 29 This technique is more anatomically representative because of its 3D nature.…”
BackgroundImaging assessment of the anterior visual pathway structures, particularly the optic nerves (ON), requires knowledge of normal dimensions. Several studies suggesting techniques and normal ranges have been performed, but most suffer from various methodological flaws. This study is the first to be performed in a South African population.ObjectivesThe aim of this study was to establish normal measurements of the ON, optic nerve sheath (ONS) and optic chiasm (OC) on magnetic resonance imaging (MRI).MethodEighty normal adults between ages of 12 and 65 years were included in this prospective, quantitative, observational, descriptive study to establish normal measurement of the ON, ONS and OC using a T2W 3D MRI sequence. Measurements (width and height) were undertaken by two observers independently.ResultsA total of 80 participants with a mean age of 35 years were studied: 49 females (61.25%) and 31 males (38.75%). There were no statistical differences in the measurements between gender and age correlation. Interobserver agreement was best for larger structures, that is, OC width and intracranial ON width, respectively. The overall mean of OC width was 13.63 mm (range: 11.13 mm–16.92 mm, standard deviation [s.d.] 1.21); intraorbital ON height at 5 mm behind the globe 2.29 mm (range: 1.63 mm–3.33 mm, s.d. 0.43), and intracranial ON width 4.27 mm (range: 2.46 mm–5.19 mm, s.d. 0.53).ConclusionNormal measurements of the anterior visual pathway structures on MRI are best reflected in the larger structures. Interobserver variability was poor for the orbital ON, ONS, intracranial ON height and OC height. We recommend that measurements be obtained for the OC width and intracranial ON width. The overall mean for the OC width is 13.63 mm and intracranial ON width 4.27 mm.
“…To address this shortcoming we have modified this model by applying it in an iterative manner while decreasing the tolerance from adjacent slices. 10 This technique allows the model to ignore slices that are less than optimal and results in anatomically viable, 3D consistent measurements along the entire length of the optic nerve. This model is then applied to all of the patients and healthy volunteers, generating two sets of measurements for each individual.…”
Section: Methodsmentioning
confidence: 99%
“…Our group has characterized these improvements in optic nerve MRI in healthy controls. 9 Additionally, we have recently developed an analysis pipeline for optic nerve MRI that affords an opportunity to evaluate the morphology of the optic nerve in vivo along its entire length, 10 , 11 thereby allowing measurements of both global and focal atrophy. Figure 1.…”
Section: Introductionmentioning
confidence: 99%
“…Our group has characterized these improvements in optic nerve MRI in healthy controls. 9 Additionally, we have recently developed an analysis pipeline for optic nerve MRI that affords an opportunity to evaluate the morphology of the optic nerve in vivo along its entire length, 10,11 thereby allowing measurements of both global and focal atrophy. Figure 1.Healthy control scanned with: current clinical standard of care T2w MRI axial view (a) and coronal view approximately 10 mm posterior to the globe (b), as well as high-resolution isotropic T2w research imaging axial view (c) and coronal view approximately 10 mm posterior to the globe (d).…”
BackgroundOptic neuritis (ON) is one of the most common presentations of multiple sclerosis (MS). Magnetic resonance imaging (MRI) of the optic nerves is challenging because of retrobulbar motion, orbital fat and susceptibility artifacts from maxillary sinuses; therefore, axonal loss is investigated with the surrogate measure of a single heuristically defined point along the nerve as opposed to volumetric investigation.ObjectiveThe objective of this paper is to derive optic nerve volumetrics along the entire nerve length in patients with MS and healthy controls in vivo using high-resolution, clinically viable MRI.MethodsAn advanced, isotropic T2-weighted turbo spin echo MRI was applied to 29 MS patients with (14 patients ON+) or without (15 patients ON–) history of ON and 42 healthy volunteers. An automated tool was used to estimate and compare whole optic nerve and surrounding cerebrospinal fluid radii along the length of the nerve.Results and conclusionOnly ON+ MS patients had a significantly reduced optic nerve radius compared to healthy controls in the central segment of the optic nerve. Using clinically available MRI methods, we show and quantify ON volume loss for the first time in MS patients.
“…We have published studies describing the technical development of our method, validation in CT, validation in MRI, and validation of the utility of clinical context optimization of imaging biomarkers. [2][3][4][5][6][7][8][9][10][11][12][13][14] We appreciate the letter writers' recent validation efforts.…”
Section: Reply Re: "Correlation Of Automated Computed Tomography Volu...mentioning
Letters to the editorRe: "Correlation of Automated Computed Tomography Volumetric Analysis Metrics With Motility Disturbances in Thyroid Eye Disease"
To the Editor:We read with great interest the article "Correlation of Automated Computed Tomography Volumetric Analysis Metrics With Motility Disturbances in Thyroid Eye Disease" wherein Law et al. 1 employ an automated segmentation method developed using normal orbital CT images to characterize relationships between CT metrics and clinical findings in patients with thyroid eye disease. Using this automated method, the authors concluded that ocular motility deficits were correlated with superior, inferior, and lateral recti average diameter, maximum diameter, and volume, and medial rectus volume. 1 Developing a fully automated method of segmenting orbital soft tissues to help analyze patients with thyroid eye disease holds great potential value. However, any new method must be validated for accuracy. As we have presented at the 2022 ASOPRS Fall Meeting, our fully-automated atlas-based method developed using normal control orbits demonstrated lower accuracy in evaluating soft tissue volumes in thyroid eye disease orbits compared with normal orbits, using manual segmentation as the gold standard. 2 Accuracy was assessed using intersection over union and Dice coefficient, which is standard for analyzing such imaging algorithms. 2,3 As the automated segmentation method described by Law et al. 1 was developed using normal orbit CT images, further validation must be presented to describe the accuracy of this new method as applied to thyroid eye disease orbits before clinical associations can be meaningfully analyzed.We thank the authors for bringing this important new area of research to the oculofacial literature.
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