Brain temperature measurement

Previously, in vitro recovery was the most commonly used method for estimating ECF concentrations of a substance (Benveniste, 1989 Stable et al., 1991). To determine in vitro recovery, the probe is immersed in a known concentration of the analyte, preferably at brain temperature, and perfused with a medium free of the analyte. Percent recovery (or relative recovery) is defined as the ratio between two measures (a) the concentration of the analyte that is recovered from the probe and (b) the known concentration. In vitro calibration is limited and no longer considered appropriate, because it fails to factor in physiological factors, such as extracellular tortuosity and neurochemical reuptake, which iirfluence in vivo but not in vitro recovery (Benveniste, 1989 Benveniste and Huttemeier, 1990 Bungay et al., 1990 Hsiao et al., 1990 Morrison et al., 1991 Parsons et al., 1991b Parsons and Justice, 1992 Stable, 2000). 

Thermal sensor array systems for medical-analytical purposes were developed early [7]. Temperature distributions and blood perfusion in the brain were measured with thin film thermistors exhibiting a temperature resolution of 0.1 mK with a time constant of few milliseconds. 

Figure 7.4. Temperature compensation of LDH (upper panel) and citrate synthase (CS) (lower panel) activity in brains of Antarctic notothenioid fishes and tropical fishes. Enzymatic activity in homogenates of brain was measured at a common temperature, 10°C, and extrapolated to the approximate habitat temperatures of the species (0°C for Antarctic fish and 25°C for tropical species) using experimentally determined Q10 values. Activities at habitat temperatures are indicated in the figure. Despite substantial temperature compensation, an approximately twofold difference in activity persists at habitat temperatures for both enzymes. (Data from Kawall et al., 2001).

How the temperature is measured (i.e., brain vs arterial, venous, tympanic, bladder, or rectal temperature) is also critical, as the core temperature is usually 0.3-1.1°C lower than brain temperature (51). However, it is important to consider that these values may be different in patients with acute cerebral ischemia or trauma. 

Nurse S. and Corbett D. (1994) Direct measurement of brain temperature during and after intraischemic hypothermia correlation with behavioral, physiological, and histological endpoints. J. Neurosci. 14,7726-7734. 

Resonance attributes can be modulated by intracellular biophysical conditions. For example, MRS can be used to measure pHi by measuring the chemical shifts of Pi and other peaks (e.g., ATP). Al-kahne pH is indicative of a poor prognosis following perinatal asphyxia. spectra can be used to measure local brain temperature by comparing the chemical shift of the un-suppressed water peak, which has a relatively strong temperature dependence due to the hydrogen bonding between molecules, with those of Naa, Cho, and Cr. This property may be combined with MRSI to yield temperature maps of the brain. 

The smaller diameter of the iron cores of ferritin in brain compared to that in liver tissues fits well with the blocking temperatures measured by Mossbauer spectroscopy. The blocking temperature determined by MS for SN is about I5 K [20] compared to about 35-40 K for human liver [21 ]. Figure 16.4 presents the Mossbauer spectra obtained from SN at 20 K, I OK, and 4.1 K, from which the blocking temperature was estimated. 

Multi-frequency Microwave Radiometer System for Measuring Deep Brain Temperature in New Born Infants... 

Abstract— Hypothermic brain treatment for newborn babies are currently hindered by the lack of appropriate techniques for continuous and non-invasive measurement of deep brain temperature. Microwave radiometry (MWR) is one of the promising methods that is completely passive and inherently safe. Five-band microwave radiometer system and its feasibility were reported with a confidence interval level of the temperature estimation of about 1.6 °C at 5 cm depth from the surface. This result was not good enough for clinical application because clinical requirement is less than 1 °C for both accuracy and stability. This paper describes the improved result of temperature resolutions of the five radiometer receivers, and shows the new confidence interval obtained form temperature measurement experiment using an agar phantom based on a water-bath. Temperature resolutions were 0.103, 0.129, 0.138, 0.105 and 0.111 °C for 1.2, 1.65, 2.3, 3.0 and 3.6 GHz receiver, respectively, and new confidence interval was 0.51 °C at 5 cm from surface. We believe that the system takes a step closer to the clinical hypothermic treatment. 

Invasive methods for direct measurement of deep brain temperature can not be easily justified for ethical reasons. Correlations between deep brain temperature and surrogate measures such as tympanic membrane, nasopharyngeal, esophageal or rectal temperatures are uncertain, particularly... 

One of the possible alternative methods for non-invasive temperature sensing and monitoring that is completely passive and inherently safe is microwave radiometry (MWR).. We proposed a multi-fl equency microwave radiometry as a non-invasive monitoring method of deep brain temperature and fabricated a five-band receiver system and reported its measurement performance of about 1.6 K 2o-confidence interval at 5 cm depth from the surface of a water-bath phantom with similar temperature distribution as infant s brain [6]. Because the clinical requirement is less than 1 K, further improvement of MWR system were essential for a successful hypothermia treatment. We have done a couple of actions to reduce background noise in order to obtain the better temperature resolutions of five microwave receivers and tried to retrieve the temperature profile in the phantom. This paper describes the current feasibility of the MWR system for clinical hypothermic treatment. 

Using the five-band radiometer system, we made a temperature measurement experiment on a phantom. An arrangement of the phantom which emulated the profile in brain is illustrated in Fig.5. Temperatures at eight different locations along the depth were monitored by thermocouples for reference. 

Sugiura T, Hoshino S, Sawayama Y (2006) Five-band microwave radiometer system for non-invasive measurement of deep brain temperature in newborn infants First phantom study. Proc PIERS 395-398... 

Maniyama K, Mizushina S, Sugiura T et al. (2000) Feasibility of Non-invasive Measurement of Deep Brain Temperature in New-born Infants by Multi-frequency Microwave Radiometry. IEEE Trans M IT 48 2141-2147... 

Childs, C, 2008. Human brain temperature regulation, measurement and relationship with cerebral trauma part 1. Br. J. Neurosurg. 22, 486-4%. 

Various optical detection methods have been used to measure pH in vivo. Fluorescence ratio imaging microscopy using an inverted microscope was used to determine intracellular pH in tumor cells [5], NMR spectroscopy was used to continuously monitor temperature-induced pH changes in fish to study the role of intracellular pH in the maintenance of protein function [27], Additionally, NMR spectroscopy was used to map in-vivo extracellular pH in rat brain gliomas [3], Electron spin resonance (ESR), which is operated at a lower resonance, has been adapted for in-vivo pH measurements because it provides a sufficient RF penetration for deep body organs [28], The non-destructive determination of tissue pH using near-infrared diffuse reflectance spectroscopy (NIRS) has been employed for pH measurements in the muscle during... 

To confirm their results and check for methodological problems, some studies have been carried out. As there was a probability that hypothermic conditions during temporary removal from dam may have affected the results, Pauluhn and Schmuck administered S-bioallethrin and deltamethrin to neonatal mice from postnatal day 10 to 16 under a hypo-, normo-, or hyperthermic environment, and measured the MAChR density at the age of 17 days [51]. Increase in MAChR in Cortex at PND 17 in animals treated with S-bioallethrin was observed. Meanwhile, no changes were observed in animals treated with deltamethrin. In addition, an enormous influence of environmental temperature on the density of MAChR receptors in the crude synaptosomal fraction of the cerebral cortex was ascertained. Tsuji et al. exposed mouse dams with their litters to D-allethrin by inhalation for 6 h from postnatal day 10 to 16. The inhalation administration method is the most relevant route of exposure for humans, including babies and infants, after indoor use of D-allethrin. The neonatal exposure to D-allethrin by inhalation did not induce effects either on the brain MAChR density or motor activity at 17 days and 4 months of age, or on performance in the leaming/memory test at 11 months of age [52]. Other unpublished studies with D-allethrin, S -bioallethrin, or deltamethrin were examined to confirm the results of Eriksson et al. and showed inconsistent results [53]. The reasons for discrepancy among these findings are unknown. 

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