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 approach - based 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.
Highlights
Tissue oximeters based on near-infrared spectroscopy (NIRS) have become increasingly common for cerebral oxygenation monitoring of premature infants in intensive care units [1,2], as well as during neonatal and pediatric surgeries, cardiac procedures [3,4]
Phantoms were comprised of three primary components (Fig. 1): the 3D-printed cerebrovascular module (CVM) and two superficial layers based on a polydimethylsiloxane (PDMS) matrix – one simulating the skin/skull/scalp region (Layer 1) and a second simulating cerebrospinal fluid (CSF) in the subarachnoid space (Layer 2)
It is worth noting that a prior study [28] measured a superficial-tissue-mimicking slab with slightly different properties using the adult sensor of Oximeter B, and found a value of 78%; using the same sensor and our phantom slab, we measured an StO2 of 73%
Summary
Tissue oximeters based on near-infrared spectroscopy (NIRS) have become increasingly common for cerebral oxygenation monitoring of premature infants in intensive care units [1,2], as well as during neonatal and pediatric surgeries, cardiac procedures [3,4]. Active cerebral monitoring with oximeters can have an important impact during and after cardiovascular surgery and neurosurgery [6]. Dix et al [9] compared measurements from three commercial oximeters in 55 infants and found differences of 10 to 15% in tissue oxygenation (StO2) values. A number of other clinical studies have found significant differences in performance amongst cerebral oximeters [11,12,13]. The lack of standardization in clinical outputs have led some to conclude that cerebral oximeters are ineffective for estimating absolute StO2 and should be limited to trend monitoring [10]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call