Non-invasive measurement of brain temperature using radiometric thermometry: Experimental validation and clinical observations in asphyxiated newborns

Abstract

BACKGROUND: Therapeutic hypothermia (HT) has been shown to decrease death and severe disability in infants with hypoxicischemic encephalopathy (HIE). Rectal temperature (RT) is used to determine the temperature set-points for treatment with HT, however experimental studies have shown significant differences between RT and brain temperature during HT. Knowledge of actual brain temperature during HT might allow better determination of optimal degree of cooling and improve outcomes. OBJECTIVES: To compare measurements of brain temperature obtained by non-invasive radiometric thermometry (RadT) to direct tissue measurements in an experimental model of HT, and to use RadT in newborn infants with HIE undergoing HT. STUDY DESIGN: RadT measurements of brain temperature were compared to fiber optic (Luxtron) thermometry measurements placed at a depth of 1.5 centimeters into the brain of cooled miniswine. Following validation studies, brain RadT and RT measurements were continuously recorded in thirty infants with HIE during HT and rewarming. RESULTS: RadT and Luxtron probe temperatures were comparable in miniswine throughout a temperature range similar to therapeutic HT. RadT measurements of brain temperature were higher than RT in 60% of infants with HIE undergoing HT. Higher RadT measurements compared to RT were associated with cerebral white matter abnormalities (p = 0.01). CONCLUSIONS:RadT provides a safe, passive and non-invasive way to measure brain temperature that can be used in the clinical setting. RadT may be helpful in determining the optimal degree of cooling and identifying infants at highest risk of brain injury.

Active cooling temperature required to achieve therapeutic hypothermia correlates with short‐term outcome in neonatal hypoxic‐ischaemic encephalopathy

“…Injury patterns in this area are known to be associated with impaired temperature regulation (Bass et al . ). Several groups have shown that the degree of basal ganglia injury correlates with poor outcome (Martinez‐Biarge et al .…”

“…The device output temperature on day 3 of treatment most accurately correlated with MRI injury in the grey matter, including basal ganglia and thalamic injury. Injury patterns in this area are known to be associated with impaired temperature regulation (Bass et al 2014). Several groups have shown that the degree of basal ganglia injury correlates with poor outcome (Martinez-Biarge et al 2010;Massaro et al 2010).…”

“…Similarly, in a rat model, Wood et al (2018) observed that a spontaneous lower core temperature after asphyxia was associated with more severe injury. In humans, severe injury to the basal ganglia and thalamus has been shown to be associated with impaired temperature regulation (Bass et al 2014). In the absence of thermoregulatory interventions, the core temperature during the first day of life in asphyxiated neonates is significantly lower than in uninjured term newborns (Burnard & Cross, 1958).…”

Non-invasive Brain Temperature Measurement in Acute Ischemic Stroke

“…(2) Radiometric thermometry A potential alternative to MRSI for measuring brain temperature is zero-heat-flux or radiometric thermometry through sensors placed on the forehead (37,38). Zeroheat-flux thermometry uses a temperature sensor and an electric heater to create an isothermal tunnel where the skin surface is heated to the temperature of the underlying tissue; the brain when the sensor is placed on the forehead (38,39).The potential benefits of zero-heat-flux thermometry are significant, as it may preclude the need for more invasive monitoring.…”

“…In a study by Bass et al (37), they used a radiometric thermometry sensor in 30 neonates with hypoxic-ischemic encephalopathy and found it effective in monitoring therapeutic hypothermia (37). The authors validated the radiometric thermometry sensors by using three mini-swine that were cooled to 33-34 • C using a cooling blanket.…”