Clinical Applications: Ischemia & TBI
Shunrou Fujiwara1,2, Kuniaki Ogasawara2, Takaaki Beppu2, and Yoshichika Yoshioka3
1Division of Molecular and Cellular Pharmacology, Department of Pathophysiology and Pharmacology, School of Pharmaceutical Science, Iwate Medical University, Yahaba, Japan, 2Department of Neurosurgery, School of Medicine, Iwate Medical University, Yahaba, Japan, 3Institute for Biomedical Sciences, Iwate Medical University, Yahaba, Japan

Synopsis

Keywords: Neuro: Brain, Neuro: Cerebrovascular, Neuro: White matter

Brain temperature (BT) had traditionally been discussed whether it may be a simple parameter depending on body (core) temperature or it may regulate the neural activities. Recent reports with magnetic resonance (MR) imaging system demonstrated BT was strongly associated with the cerebral perfusion and metabolism in patients with ischemic change. Based on these results, we should refocus and reconsider on BT and the alteration mechanism using MR. Here, we reviewed BT measurement techniques with MR and discussed the pathologic conditions causing BT alteration relating to the cerebral perfusion and metabolism.

Purpose

Brain temperature (BT) had traditionally been discussed whether it may be a simple parameter depending on body (core) temperature or it may regulate the neural activities. Recent reports with magnetic resonance (MR) imaging system demonstrated BT was strongly associated with the cerebral blood flow and metabolism in patients with ischemic change. Based on these results, we should refocus and reconsider on BT and the alteration mechanism using MR. Here, we reviewed BT measurement techniques with MR and discussed the pathologic conditions causing BT alteration relating to the cerebral blood flow and metabolism.

Direct measurements

About direct BT measurements in patients, a few groups have demonstrated the interesting results1-4. Shiraki, et al. might publish the first report of a direct BT measurement. They performed the direct measurement by a drainage catheter in a patient who underwent surgery to relieve intracranial pressure by a pineal tumor, and they showed the independency between BT and tympanic temperature1. The other group also performed the measurement by the ventricular catheter in patients with subarachnoid hemorrhage (SAH)4. This group demonstrated that the higher BT group showed good outcome after SAH and all patients in the lower BT group died. This research also showed that the outcome became worse when BT decreased less than the systemic temperature. In these results, the lower BT might indicate the remarkably low metabolism.

Non-invasive measurements

1H-MRS, which can be non-invasively performed with multi-voxel scan as well as single voxel scan, has been used for temperature measurements in human5-11. Cady et al. performed the BT measurement of newborn infants5. By the calibrated date, they defined a basic formula to estimate the temperature using the amount of the chemical shift between H2O and NAA as follows: T [°C] = 286.9-94×Δ(H2O-NAA). This formula has been a key to measure BT with 1H-MRS in recent researches9-11. Yablonskiy, et al. demonstrated that the relation between temperature and blood flow in the local area in the brain by using functional MRI and 1H-MRS6; however, they could not show whether BT was associated with the oxygen metabolism directly measured by a gold standard modality like positron emission tomography (PET) to assess the cerebral perfusion and metabolism. Ishigaki, et al. directly compared the BT by 1H-MRS with the parameters on PET in patients with chronic ischemia9. Their results showed BT significantly correlated with oxygen extraction fraction (OEF) and BT can detect patients with OEF elevation relating to a high risk of stroke recurrence. By this key paper, BT alteration might be quantitatively connected with the cerebral perfusion and metabolism. These results using 1H-MRS contributed extended results in chronic ischemia using chemical shift imaging (CSI)10,11. Carbon monoxide (CO) poisoning can cause abnormal OEF elevation12, which means that cerebral blood flow (CBF) reduced and cerebral metabolic rate of oxygen (CMRO2) maintained.In some reports, abnormal BT elevation was observed during the period between acute and subacute phase after CO exposure13,14. On the other hand, BT significantly decreased at the subacute phase comparing with the acute, in particular, BT in patients with severe white matter damage mimicked the normal13. The results may indicate that the brain metabolism to produce heat for BT decreased by severe white matter damage observed in patients with severe CO poisoning14. These results in patients with CO poisoning indicate that BT alteration is strongly associated with the cerebral metabolism. Diffusion weighted imaging (DWI) can be also used for BT measurements. Yamada, et al. demonstrated the difference between healthy controls and patients with moyamoya disease, which is a kind of chronic ischemia15. Fujiwara, et al. tried to measure BT in patients with CO poisoning with DWI and the temperature in the arachnoid space measured by DWI significantly correlated with that in the white matte region measured by 1H-MRS-BT16. DWI temperature measurement potentially may help us to know the BT alteration in the lesion with the difficulty in such measurement with 1H-MRS.

Acknowledgements

No acknowledgement found.

References

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Proc. Intl. Soc. Mag. Reson. Med. 32 (2024)