Accuracy of Optic Nerve Sheath Diameter Measurements in Pocket-Sized Ultrasound Devices in a Simulation Model.

Garrett G R J Johnson,Tomislav Jelic,Angela Derksen,Bertram Unger,Frederick A Zeiler,Lawrence M Gillman,Markus T Ziesmann

doi:10.3389/fmed.2022.831778

Garrett G R J Johnson, Tomislav Jelic + Show 5 more

Open Access

https://doi.org/10.3389/fmed.2022.831778

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Abstract

IntroductionTransorbital sonographic measurement of optic nerve sheath diameter (ONSD) is an emerging non-invasive technique for the identification and monitoring of intracranial hypertension. In recent years, new pocket ultrasound devices have become available, and it is uncertain if they have the resolution to measure such small structures appropriately as compared to their predecessors. In this study, we measure the performance of three ultrasound units on a simulation model to establish their precision and accuracy.MethodsONSD was measured by three expert point-of-care sonographers using ultrasound machines three times on each of seven discrete ONS model sizes ranging from 3.5 to 7.9 mm. Two pocket ultrasounds (IVIZ, Sonosite, and Lumify, Philips) and one standard-sized portable ultrasound (M-Turbo, Sonosite) were used. Measurements were analyzed for mean error and variance and tested for significance using blocked covariance matrix regression analyses.ResultsThe devices differed in their variances (Lumify: 0.19 mm2, M-Turbo: 0.26 mm2, IVIZ: 0.34 mm2) and their mean error (Lumify: −0.05 mm, M-Turbo: 0.10 mm, IVIZ: −0.10 mm). The difference in mean error between users is not significant (p = 0.45), but there is a significant difference in mean error between devices (p = 0.02).ConclusionsAccurate ONSD measurement is possible utilizing pocket-sized ultrasound, and in some cases, may be more accurate than larger portable ultrasound units. While the differences in these devices were statistically significant, all three were highly accurate, with one pocket device (Lumify) outperforming the rest. Further study in human subjects should be conducted prior to using pocket ultrasound devices for in vivo diagnosis of intracranial hypertension.

Highlights

Transorbital sonographic measurement of optic nerve sheath diameter (ONSD) is an emerging non-invasive technique for the identification and monitoring of intracranial hypertension
We have shown, using a simulation model, that one pocket-sized ultrasound device (Vscan, GE Healthcare) performed equal to a standard-sized validated ultrasound (M-turbo, Sonosite) with respect to intra and interobserver variability, and there was a high level of agreement between measurements obtained using the two machines [15]
For the M-turbo, mechanical index (MI) was 0.2 and thermal index (TI) 0–0.1. It was previously unknown if new pocket ultrasound devices can be used to make clinically useful ONSD measurements similar to their larger predecessors

Summary

Introduction

Transorbital sonographic measurement of optic nerve sheath diameter (ONSD) is an emerging non-invasive technique for the identification and monitoring of intracranial hypertension. Intracranial hypertension (IH) is a lethal and relatively common phenomenon in critically ill traumatic brain-injured patients. While these patients’ prognosis is guarded, they fair much worse if this condition is not diagnosed accurately and treated promptly [1–3]. While CT scan and MRI aid in the diagnosis of IH, they are time-consuming and are difficult to administer repeatedly to provide continuous intracranial pressure (ICP) monitoring often required by these patients [5, 6]. ICP monitoring devices are considered gold standard for the diagnosis and monitoring of IH. Their limitations are that they are invasive, require neurosurgical expertise both to administer and monitor, and are associated with risks including bleeding and infection [9]

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