Variations in signal intensity with periodical temperature changes in vivo in rat brain: analysis using wide-field optical coherence tomography.

In a previous study, we reported measurements of three-dimensional (3D) optical coherence tomography (OCT) images through a thinned skull by reducing temperatures from 28 °C to 18 °C in vivo in the rat brain to show negative correlation coefficients (CCs) between ratios of signal intensity (RSI) and temperature for applications to monitoring brain viability. In this study, using the same OCT system, we measured 3D OCT images of the rat brain by periodically changing tissue temperatures from 20 °C to 32 °C in vivo. In the evaluation of CCs among RSI, temperature, and heart rate, the largest number of periods was four, and the longest measurement time was 570 min. Averaged CCs between RSI and temperature, and between RSI and heart rate, were -0.42 to -0.50 and -0.48 to -0.64, respectively. RSI reversibly changed subsequent variations of temperatures and finally increased rapidly just before cardiac arrest. These results indicate that RSI could correspond to decreases in viability because of local ischemia and recovery.

In vivo rat brain measurements of changes in signal intensity depth profiles as a function of temperature using wide-field optical coherence tomography.

In our previous study, we used optical coherence tomography (OCT) and reported an increase in signal intensity of depth profiles between euthanasia injection and cardiac arrest (CA), demonstrating the potential as a tool for monitoring/diagnosing brain tissue viability [Appl. Opt.48, 4354 (2009)]. Here, for the first time to our knowledge, we measured three-dimensional (3D) OCT images through a thinned skull changing temperatures in the rat brain. The measurements were made at 10 min intervals for 210 min to evaluate correlations of temperature with heart rate and ratios of signal intensity (RSI). The 3D image area was 4 mm × 4 mm × 2.8 mm. When the temperature was decreased from 28°C to 18°C to reduce tissue viability, the heart rate was found to decrease with an increase in RSI. Negative correlation coefficients (CCs) between temperatures and RSIs, and between heart rate and RSIs, were obtained. This indicates that OCT signals increase with reductions of viability caused by decreases in heart rates and temperatures in tissues. These observations correspond to estimations obtained by multiwavelength diffuse reflectance spectroscopy [Appl. Opt.47, 4164 (2008)]. CCs and stationary RSIs would depend upon measured positions in tissues. Without injections for euthanasia, a similar rapid increase in RSI has also been measured before CA.

Measurement of signal intensity depth profiles in rat brains with cardiac arrest maintaining primary temperature by wide-field optical coherence tomography.

We have already reported that after an injection for euthanasia, the signal intensity of optical coherence tomography (OCT) images are 2.7 times increased before cardiac arrest (CA) using OCT and rat brains without temperature control to show the potential of OCT to monitor tissue viability in brains [Appl. Opt.48, 4354 (2009)APOPAI0003-693510.1364/AO.48.004354]. In this paper, we similarly measured maintaining the primary temperature of rat brains. It was confirmed that when maintaining the primary temperature, the time courses of the ratios of signal intensity (RSIs) were almost the same as those without temperature control. RSIs after CA varied from 1.6 to 4.5 and depended on positions measured in tissues. These results mean that the OCT technique has clinical potential for applications to monitor or diagnose a focal degraded area, such as cerebral infarctions due to focal ischemia in brains.

Light minimal supersymmetric standard model Higgs boson scenario and its test at hadron colliders.

We show that, in the minimal supersymmetric standard model, the possibility for the lightest CP-even Higgs boson to be lighter than Z boson (as low as about 60 GeV) is, contrary to the usual belief, not yet excluded by the CERN LEP2 Higgs search nor any direct searches for supersymmetric particles at high energy colliders. The characteristic of the light Higgs boson scenario (LHS) is that the ZZh coupling and the decay branching ratio Br(h/A-->bb) are simultaneously suppressed as a result of generic supersymmetric loop corrections. Consequently, the W(+/-)H(-/+)h coupling has to be large due to the sum rule of Higgs couplings to weak gauge bosons. We discuss the potential of the Fermilab Tevatron and B factories to test the LHS, and show that the associated neutral and charged Higgs boson production process, pp-->H(+/-)h(A), can completely probe the LHS at the CERN Large Hadron Collider.