Simultaneous infrared thermal imaging and laser speckle imaging of brain temperature and cerebral blood flow in rats

Ginseng aconitum decoction (Shenfu Tang) provides neuroprotection by ameliorating impairment of blood-brain barrier in cerebral ischemia-reperfusion injury

Ischemic stroke (IS) remains one of the most serious threats to human life. Early blood-brain barrier damage (BBB) is the cause of parenchymal cell damage. Repair of the structure and function of the BBB is beneficial for the treatment of IS. The traditional prescription ginseng aconitum decoction (GAD) has a long history in the treatment of cardiovascular and cerebrovascular diseases, however, the effect of GAD on the BBB disruption and underlying mechanisms remains largely unknown. To address these issues, in vitro models of BBB were established with brain endothelial cells (bEnd.3). We found that GAD reduced the leakage of the fluorescent probe FITC-dextran (P < 0.01) and increased the expression of tight junction proteins (Claudin-5, ZO-1) (P < 0.05) in the BBB model in vitro. Furthermore, to investigate the BBB protective effects of GAD in vivo. A total of 25 male C57/BL6 mice (20 - 22 g) were randomly divided into 5 groups (n = 5 per group): (1) Sham group (saline), (2) MCAO group (saline), (3) MCAO + CG group (Chinese ginseng 8 mg/kg/day), (4) MCAO + AC group (aconite 8 mg/kg/day), (5) MCAO + GAD group (GAD 8 mg/kg/day).We constructed IS model in mice and found that GAD treatment reduced IgG leakage (P < 0.05), up-regulated the expression of tight junction proteins Claudin-5, Occludin, and ZO-1 (P < 0.05). Further mechanism study showed that fatty acid oxidation (FAO) of vascular endothelial cells is involved in the protection of the BBB after IS, and GAD regulates FAO (P < 0.05) to protect BBB. In addition, we found the effect of GAD was stronger than that of Chinese ginseng (CG) (P < 0.05) and aconite (AC) (P < 0.01) alone. We concluded that GAD ameliorated the BBB dysfunction by regulating FAO involving vascular endothelial cells after IS. At the same time, the prescription is more effective than single traditional Chinese medicine.

Thermosensitive/thermochromic silicone and infrared thermography mapping in 60 consecutive cases of epilepsy surgery

Background

Epilepsy surgery represents a therapeutic opportunity for those patients who do not respond to drug therapy. However, an important challenge is the precise identification of the epileptogenic area during surgery. Since it can be hard to delineate, it makes it necessary to use auxiliary tools as a guide during the surgical procedure. Electrocorticography (ECoG), despite having shown favorable results in terms of reducing post-surgical seizures, have certain limitations. Brain mapping using infrared thermography mapping and a new thermosensitive/thermochromic silicone (TTS) in epilepsy surgery has introduced a new resource of noninvasive and real-time devices that allow the localization of irritative zones.

Methods

Sixty consecutive patients with drug-resistant epilepsy with surgical indications who decided to participate voluntarily in the study were included in the study. We measured brain temperature using two quantitative methods and a qualitative method: the TTS sheet. In all cases, we used ECoG as the gold standard to identify irritative areas, and all brain tissue samples obtained were sent to pathology for diagnosis.

Results

In the subgroup in which the ECoG detected irritative areas (n = 51), adding the results in which there was a correlation with the different methods, the efficiency obtained to detect irritative areas is 94.11% (n = 48/51, P ≤ 0.0001) while the infrared thermography mapping method independently has an efficiency of 91.66% (P ≤ 0.0001). The TTS has a sensitivity of 95.71% and a specificity of 97.9% (P ≤ 0.0001) to detect hypothermic areas that correlate with the irritative zones detected by ECoG. No postoperative infections or wound dehiscence were documented, so the different methodologies used do not represent an additional risk for the surgical proceedings.

Conclusion

We consider that the infrared thermography mapping using high-resolution infrared thermography cameras and the TTS are both accurate and safe methods to identify irritative areas in epilepsy surgeries.

A Novel Intraoperative Mapping Device Detects the Thermodynamic Response Function

Functional activation leads to an increase in local brain temperature via an increase in local perfusion. In the intraoperative setting, these cortical surface temperature fluctuations may be imaged using infrared thermography such that the activated brain areas are inferred. While it is known that temperature increases as a result of activation, a quantitative spatiotemporal description has yet to be achieved. A novel intraoperative infrared thermography device with data collection software was developed to isolate the thermal impulse response function. Device performance was validated using data from six patients undergoing awake craniotomy who participated in motor and sensory mapping tasks during infrared imaging following standard mapping with direct electrical stimulation. Shared spatiotemporal patterns of cortical temperature changes across patients were identified using group principal component analysis. Analysis of component time series revealed a thermal activation peak present across all patients with an onset delay of five seconds and a peak duration of ten seconds. Spatial loadings were converted to a functional map which showed strong correspondence to positive stimulation results for similar tasks. This component demonstrates the presence of a previously unknown impulse response function for functional mapping with infrared thermography.

Intraoperative cerebral blood flow monitoring in neurosurgery: A review of contemporary technologies and emerging perspectives

Intraoperative monitoring of cerebral blood flow (CBF) has become an invaluable adjunct to vascular and oncological neurosurgery, reducing the risk of postoperative morbidity and mortality. Several technologies have been developed during the last two decades, including laser-based techniques, videomicroscopy, intraoperative MRI, indocyanine green angiography, and thermography. Although these technologies have been thoroughly studied and clinically applied outside the operative room, current practice lacks an optimal technology that perfectly fits the workflow within the neurosurgical operative room. The different available technologies have specific strengths but suffer several drawbacks, mainly including limited spatial and/or temporal resolution. An optimal CBF monitoring technology should meet particular criteria for intraoperative use: excellent spatial and temporal resolution, integration in the operative workflow, real-time quantitative monitoring, ease of use, and non-contact technique. We here review the main contemporary technologies for intraoperative CBF monitoring and their current and potential future applications in neurosurgery.

Multi-modal nonlinear optical and thermal imaging platform for label-free characterization of biological tissue

The ability to characterize the combined structural, functional, and thermal properties of biophysically dynamic samples is needed to address critical questions related to tissue structure, physiological dynamics, and disease progression. Towards this, we have developed an imaging platform that enables multiple nonlinear imaging modalities to be combined with thermal imaging on a common sample. Here we demonstrate label-free multimodal imaging of live cells, excised tissues, and live rodent brain models. While potential applications of this technology are wide-ranging, we expect it to be especially useful in addressing biomedical research questions aimed at the biomolecular and biophysical properties of tissue and their physiology.

In vivo imaging with a water immersion objective affects brain temperature, blood flow and oxygenation

Previously, we reported the first oxygen partial pressure (Po2) measurements in the brain of awake mice, by performing two-photon phosphorescence lifetime microscopy at micrometer resolution (Lyons et al., 2016). However, this study disregarded that imaging through a cranial window lowers brain temperature, an effect capable of affecting cerebral blood flow, the properties of the oxygen sensors and thus Po2 measurements. Here, we show that in awake mice chronically implanted with a glass window over a craniotomy or a thinned-skull surface, the postsurgical decrease of brain temperature recovers within a few days. However, upon imaging with a water immersion objective at room temperature, brain temperature decreases by ~2-3°C, causing drops in resting capillary blood flow, capillary Po2, hemoglobin saturation, and tissue Po2. These adverse effects are corrected by heating the immersion objective or avoided by imaging through a dry air objective, thereby revealing the physiological values of brain oxygenation.