A New Inexpensive Simulation Model for Ultrasound Assessment of Optic Nerve Sheath Diameter

Abstract

ABSTRACT:Background:Sonographic measurement of optic nerve sheath diameter (ONSD) is becoming increasingly accepted as a diagnostic modality to detect elevations in intracranial pressure. As this technique becomes more widespread, methods to address the inherent operator-dependent nature of this modality will need to be developed. We propose a novel low-cost model to accurately simulate sonographic ONSD measurement for purposes of training and assessment.Methods:We designed models composed of medical tubing of various diameters readily available from typical hospital supplies and suspended them in gelatin. The models were evaluated by ultrasound by three expert point-of-care sonographers using a standard linear array probe and technique proposed in the literature.Results:This model generates faithful simulation of the ONS that closely approximates in vivo images and can be used to produce accurate, reproducible measurements. Materials are low cost and easy to acquire and assemble.Conclusions:Our model provides realistic simulated images of the ONS. Through comparison of sonographic measurements to the known tube diameters, this model serves as a promising inexpensive tool to teach the method of ultrasound assessment of ONSD or as a way to determine accuracy of this novel ultrasound technology.

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

“…We used tubing of various diameters from medical supplies made out of a variety of different plastics. However, when we analyzed and validated these models previously, we found that no model appeared to stand out as a poor performer ( 23 ). Again, in our current study, none of the models appeared to stand out as being a particular outlier, other than the smallest tube, which was composed of the same materials as many of the larger tubes.…”

“…Measurements were made using a simulation model of the ONS as published previously ( 23 ) ( Figure 1 ). In brief, medical tubing of various diameters was cut to 1 cm in length, encased in an opaque gelatin-psyllium powder matrix, and placed in Styrofoam TM coffee cups.…”

“…We felt that a smaller difference between devices was unlikely to be clinically significant. The expected standard deviation was set at 0.51 mm, based on a prior study using the same simulation models and experts ( 23 ). Significance was set at 0.05, and power at 90%, to calculate a required sample size of at least 23 measurements per ultrasound device ( 29 ).…”