Cerebral oximetry performance testing with a 3D-printed vascular array phantom

Abstract

Cerebral oximetry based on near-infrared spectroscopy represents a unique noninvasive tool for real-time surgical monitoring, yet studies have shown a significant discrepancy in accuracy among commercial systems. Towards the establishment of a standardized method for performance testing, we have studied a solid phantom approachbased on a 3D-printed cerebrovascular module (CVM) incorporating an array of 148 cylindrical channels-that has several advantages over liquid phantoms. Development and characterization of a CVM prototype are described, including high-resolution imaging and spectrophotometry measurements. The CVM was filled with whole bovine blood tuned over an oxygen saturation range of 30-90% and molded-silicone layers simulating extracerebral tissues were used to evaluate penetration depth. Saturation measurement accuracy was assessed in two commercially-available clinical cerebral oximeters. For one oximeter, both neonatal and pediatric sensors showed a high degree of precision, whereas accuracy was strongly dependent on saturation level and extracerebral geometry. The second oximeter showed worse precision, yet greater robustness to variations in extracerebral layers. These results indicate that 3D-printed channel array phantoms represent a promising new approach for standardized testing of clinical oximeters.

Head Phantom Optical Properties Validation for Near-Infrared Measurements: A Comparison with Animal Tissue

“…Since 1977, when NIRS was first described for monitoring cerebral perfusion and brain oxygenation [1], clinical implementation of this optical technology has increased [2]. For instance, tissue oxygenation has become increasingly common for cerebral oxygenation monitoring of preterm children [3]. Similarly, active cerebral monitoring with NIRS oximeters has an important impact during and after neurosurgery [3].…”

“…For instance, tissue oxygenation has become increasingly common for cerebral oxygenation monitoring of preterm children [3]. Similarly, active cerebral monitoring with NIRS oximeters has an important impact during and after neurosurgery [3]. Nowadays, wearable devices also include optical sensors for oxygenation levels monitoring, heart frequency monitoring, among others.…”

“…Therefore, it is relevant to evaluate the performance of optical technologies, evaluating the light-tissue interaction within the light spectra and tissue of interest (e.g., the brain). Phantom-based performance tests for NIRS monitoring can provide a rigorous, reproducible and convenient approach to evaluating performance using wellcharacterized materials [3]. This in-vitro method enables well controlled experiments where multiple parameters can be set, such as anatomical characteristics (e.g., layers' thickness), *There was no funding source for this study.…”

“…Previous NIRS phantoms were used for oximetry performance testing [3], [4]. The literature reported box models that mimicked the skull, filled with a rectangular silicone brain.…”

“…The literature reported box models that mimicked the skull, filled with a rectangular silicone brain. The materials' optical properties weren't compared with real head tissues and only changes in blood oxygenation levels were simulated [3], [4]. However, in order to go forward in the development of more complete optical technology, a more complex head phantom is needed.…”