8565377
Quantitative Imaging of Cerebral Blood Flow Velocity and Intracellular Motility using Dynamic Light Scattering–Optical Coherence Tomography
This paper describes a novel optical method for label-free quantitative imaging of cerebral blood flow (CBF) and intracellular motility (IM) in the rodent cerebral cortex. This method is based on a technique that integrates dynamic light scattering (DLS) and optical coherence tomography (OCT), named DLS–OCT. The technique measures both the axial and transverse velocities of CBF, whereas conventional Doppler OCT measures only the axial one. In addition, the technique produces a three-dimensional map of the diffusion coefficient quantifying nontranslational motions. In the DLS–OCT diffusion map, we observed high-diffusion spots, whose locations highly correspond to neuronal cell bodies and whose diffusion coefficient agreed with that of the motion of intracellular organelles reported in vitro in the literature. Therefore, the present method has enabled, for the first time to our knowledge, label-free imaging of the diffusion-like motion of intracellular organelles in vivo. As an example application, we used the method to monitor CBF and IM during a brief ischemic stroke, where we observed an induced persistent reduction in IM despite the recovery of CBF after stroke. This result supports that the IM measured in this study represent the cellular energy metabolism-related active motion of intracellular organelles rather than free diffusion of intracellular macromolecules.
12677065
Motion correction for phase-resolved dynamic optical coherence tomography imaging of rodent cerebral cortex
Cardiac and respiratory motions in animals are the primary source of image quality degradation in dynamic imaging studies, especially when using phase-resolved imaging modalities such as spectral-domain optical coherence tomography (SD-OCT), whose phase signal is very sensitive to movements of the sample. This study demonstrates a method with which to compensate for motion artifacts in dynamic SD-OCT imaging of the rodent cerebral cortex. We observed that respiratory and cardiac motions mainly caused, respectively, bulk image shifts (BISs) and global phase fluctuations (GPFs). A cross-correlation maximization-based shift correction algorithm was effective in suppressing BISs, while GPFs were significantly reduced by removing axial and lateral global phase variations. In addition, a non-origin-centered GPF correction algorithm was examined. Several combinations of these algorithms were tested to find an optimized approach that improved image stability from 0.5 to 0.8 in terms of the cross-correlation over 4 s of dynamic imaging, and reduced phase noise by two orders of magnitude in ~8% voxels.
23741262
On the contribution of deoxy-hemoglobin to MRI gray–white matter phase contrast at high field
High field (> or =7 T) MRI studies based on signal phase have been used to improve visualization of the fine structure of the brain, most notably the major white matter fiber bundles, the gray-white matter subdivision, and the laminar cortical architecture. The observed contrast has been attributed in part to local variations in magnetic susceptibility arising from iron in storage proteins and tissue lipid. Another contribution could come from the paramagnetic blood constituent deoxy-hemoglobin, the tissue concentration of which may vary through local variations in vascular density. To investigate this possibility, we examined phase contrast between gray and white matter in rats after intravenous administration of a superparamagnetic contrast agent at various dosages. At the maximum dosage (3 mg Fe/kg), which resulted in an estimated paramagnetic susceptibility shift 4-8 times larger than deoxy-hemoglobin, we observed a negligible increase in phase contrast between gray and white matter. This result suggests that endogenous deoxy-hemoglobin has no significant contribution to phase contrast between gray and white matter.
35704450
Development and validation of a scale for the end of life caregiving appraisal.
PURPOSE
End-of-life caregiving experiences can be complex. Family members experience physical and mental suffering as they anticipate their impending loss. Healthcare providers should be able to provide good quality of end-of-life (EOL) care and support for primary EOL caregivers. Studies have highlighted the role of healthcare providers providing information in the EOL situation to caregivers of chronic disease patients. This has resulted in the development of the End-of-life Caregiving Experience Appraisal Scale (EOLCAS) presented in this paper. The purposes of this study were to develop a scale that can evaluate the experiences of EOL caregivers, and to test the reliability and validity of this scale.


METHODS
The scale domains were derived from systematic review of 35 relevant studies. We then examined its content validity with nurse scholars and clinicians using content validity index. To examine construct validity, a total of 175 caregivers from tertiary hospital setting in Korea participated in this study from December 2007 to May 2008. For the construct validity, factor analysis was utilized.


RESULTS
The scale was composed of 32 items with four subscales: two negative appraisals (physical suffering and burden), one positive appraisal (maturation), and one neutral appraisal (social support pursuit). In this sample, the Cronbach's alpha for the entire scale was .84 indicating adequate reliability. However, Cronbach's alpha of subscales was varied.


CONCLUSION
Nurses and other healthcare professionals could use the EOLCAS to assess the experiences of EOL caregivers to understand their experience in the EOL and enhance their quality of life although psychometrics of EOLCAS shows limited findings.
32196097
Exciton-plasmon interactions in molecular spring assemblies of nanowires and wavelength-based protein detection.
Electronic interactions at the nanoscale represent one of the fundamental problems of nanotechnology. Excitons and plasmons are the two most typical excited states of nanostructures, which have been shown to produce coupled electronic systems. Here, we explore these interactions for the case of nanowires with mobile excitons and nanoparticles with localized plasmons and describe the theoretical formalism, its experimental validation and the potential practical applications of such nanoscale systems. Theory predicts that emission of coupled excitations in nanowires with variable electronic confinement is stronger, shorter and blue-shifted. These predictions were confirmed with a high degree of accuracy in molecular spring assemblies of CdTe nanowires and Au nanoparticles, where we can reversibly change the distance between the exciton and the plasmon. The prepared systems were made protein-sensitive by incorporating antibodies in the molecular springs. Modulation of exciton-plasmon interactions can serve as a wavelength-based biodetection tool, which can resolve difficulties in the quantification of luminescence intensity for complex media and optical pathways.
31281743
Respiration-induced B0 field fluctuation compensation in balanced SSFP: real-time approach for transition-band SSFP fMRI.
In functional MRI (fMRI) the resonance frequency shift induced from respiration is a major source of physiological noise. In transition-band SSFP fMRI the respiration-induced resonance offset not only increases noise interference, it also shifts the activation band. This leads to a reduction in the contrast-to-noise ratio (CNR) and the potential for varying contrast levels during the experiment. A novel real-time method that compensates for the respiration-induced resonance offset frequency is presented. This method utilizes free induction decay (FID) phase information to measure the resonance offset. For compensation, one can update the resonant frequency in real time by changing the transmit RF pulse and receiver phases to track the measured offset. The results show decreased signal power in the respiration frequency band and increased numbers of activated voxels with higher Z-scores compared to uncompensated experiments.
21739268
Transverse acoustic trapping using a gaussian focused ultrasound.
The optical tweezer has become a popular device to manipulate particles in nanometer scales and to study the underlying principles of many cellular or molecular interactions. Theoretical analysis was previously carried out at the authors' laboratory, to show that similar acoustic trapping of microparticles may be possible with a single beam ultrasound. This article experimentally presents the transverse trapping of 125 microm lipid droplets under an acoustically transparent mylar film, which is an intermediate step toward achieving acoustic tweezers in three-dimension. Despite the lack of axial trapping capability in the current experimental arrangement, it was found that a 30 MHz focused beam could be used to laterally direct the droplets toward the focus. The spatial range within which acoustic traps may guide droplet motion was in the range of hundreds of micrometers, much greater than that of optical traps. This suggests that this acoustic device may offer an alternative for manipulating microparticles in a wider spatial range.