Derek M Nusbaum1, Erik Antonsen2, Kurt H Bockhorst3, R Blaine Easley4, Jonathan B Clark4, Kenneth M Brady4, Kathleen K Kibler4, Jeffrey P Sutton5, Larry Kramer3, Ashot E Sargsyan6. 1. Department of Internal Medicine, Baylor College of Medicine, Houston, TX 7703, USA. nusbaum@bcm.edu 2. Massachusetts General Hospital, Boston, MA, USA. 3. University of Texas Health Sciences Center at Houston, TX, USA. 4. Department of Internal Medicine, Baylor College of Medicine, Houston, TX 7703, USA. 5. National Space Biomedical Research Institute, Houston, TX, USA. 6. Wyle Science, Technology and Engineering Group, Houston, TX, USA.
Abstract
BACKGROUND: Ultrasound (U/S) and MRI measurements of the optic nerve sheath diameter (ONSD) have been proposed as intracranial pressure measurement surrogates, but these methods have not been fully evaluated or standardized. The purpose of this study was to develop an ex-vivo model for evaluating ONSD measurement techniques by comparing U/S and MRI measurements to physical measurements. METHODS: The left eye of post mortem juvenile pigs (N = 3) was excised and the subdural space of the optic nerve cannulated. Caliper measurements and U/S imaging measurements of the ONSD were acquired at baseline and following 1 cc saline infusion into the sheath. The samples were then embedded in 0.5% agarose and imaged in a 7 Tesla (7T) MRI. The ONSD was subsequently measured with digital calipers at locations and directions matching the U/S and direct measurements. RESULTS: Both MRI and sonographic measurements were in agreement with direct measurements. U/S data, especially axial images, exhibited a positive bias and more variance (bias: 1.318, 95% limit of agreement: 8.609) compared to MRI (bias: 0.3156, 95% limit of agreement: 2.773). In addition, U/S images were much more dependent on probe placement, distance between probe and target, and imaging plane. CONCLUSIONS: This model appears to be a valid test-bed for continued scrutiny of ONSD measurement techniques. In this model, 7T MRI was accurate and potentially useful for in-vivo measurements where direct measurements are not available. Current limitations with ultrasound imaging for ONSD measurement associated with image acquisition technique and equipment necessitate further standardization to improve its clinical utility.
BACKGROUND: Ultrasound (U/S) and MRI measurements of the optic nerve sheath diameter (ONSD) have been proposed as intracranial pressure measurement surrogates, but these methods have not been fully evaluated or standardized. The purpose of this study was to develop an ex-vivo model for evaluating ONSD measurement techniques by comparing U/S and MRI measurements to physical measurements. METHODS: The left eye of post mortem juvenile pigs (N = 3) was excised and the subdural space of the optic nerve cannulated. Caliper measurements and U/S imaging measurements of the ONSD were acquired at baseline and following 1 cc saline infusion into the sheath. The samples were then embedded in 0.5% agarose and imaged in a 7 Tesla (7T) MRI. The ONSD was subsequently measured with digital calipers at locations and directions matching the U/S and direct measurements. RESULTS: Both MRI and sonographic measurements were in agreement with direct measurements. U/S data, especially axial images, exhibited a positive bias and more variance (bias: 1.318, 95% limit of agreement: 8.609) compared to MRI (bias: 0.3156, 95% limit of agreement: 2.773). In addition, U/S images were much more dependent on probe placement, distance between probe and target, and imaging plane. CONCLUSIONS: This model appears to be a valid test-bed for continued scrutiny of ONSD measurement techniques. In this model, 7T MRI was accurate and potentially useful for in-vivo measurements where direct measurements are not available. Current limitations with ultrasound imaging for ONSD measurement associated with image acquisition technique and equipment necessitate further standardization to improve its clinical utility.
Authors: R Mija; I Zubak; A Schuetz; M Glas; C Fung; S M Jakob; J Beck; W J Z'Graggen; Andreas Bloch Journal: PLoS One Date: 2020-02-04 Impact factor: 3.240
Authors: Bao N Nguyen; Jon O Cleary; Rebecca Glarin; Scott C Kolbe; Bradford A Moffat; Roger J Ordidge; Bang V Bui; Allison M McKendrick Journal: Transl Vis Sci Technol Date: 2021-02-05 Impact factor: 3.283