We report the development of an optical technique for noninvasive imaging of in vivo blood flow dynamics and tissue structures with high spatial resolution (2-10 microm) in biological systems. The technique is based on optical Doppler tomography (ODT), which combines Doppler velocimetry with optical coherence tomography to measure blood flow velocity at discrete spatial locations. The exceptionally high resolution of ODT permits noninvasive in vivo imaging of both blood microcirculation and tissue structures surrounding the vessel, which has significance for biomedical research and clinical applications. Tomographic imaging of in vivo blood flow velocity in the chick chorioallantoic membrane and in rodent skin is demonstrated.
We report the first application of high-speed fiber-based polarization sensitive optical coherence tomography (PS-OCT) to image burned tissue in vivo. Thermal injury denatures collagen in skin and PS-OCT can measure the reduction in collagen birefringence using depth resolved changes in the polarization state of light propagated in, and reflected from, the tissue. Stokes vectors were calculated for each point in a scan and birefringence relative to incident polarization determined using four incident polarization states. Using a high-speed fiber-based PS-OCT system on rat skin burned for varying periods of time, a correlation between birefringence and actual burn depth determined by histological analysis was established. In conclusion, PS-OCT has potential use for noninvasive assessment of burn depth.
oncurrent acquisition of morphologic and functional imaging information for the diagnosis of neurologic disorders has fueled interest in simultaneous PET and MRI (PET/MRI) (1). PET/MRI allows spatial and temporal registration of the two imaging data sets; therefore, the information derived from one modality can be used to improve the other (2,3). For dementia evaluation, PET/ MRI enables a single combined imaging examination (4). Amyloid PET has become useful as an adjunct to the diagnosis of Alzheimer disease-amyloid plaque accumulation is a hallmark pathologic finding of Alzheimer disease and can precede the onset of frank dementia by 10 to 20 years (5)-as well as for screening younger populations at high risk of Alzheimer disease in clinical trials of Alzheimer disease pharmaceuticals (6,7). PET image quality depends on collecting a sufficient number of coincidence events from annihilation photon pairs. However, the injection of radiotracers will subject patients who are scanned to radiation dose; motion during the prolonged data acquisition period results in a misplacement of the events in space, leading to inaccuracies in PET radiotracer uptake quantification (8,9). Thus, reducing collected PET counts either through radiotracer dose reduction (the focus of this work) or shortening scan time (ie, limiting the time for possible motion) while maintaining image quality would be valuable for increased use of PET/MRI. Convolutional neural networks (CNNs) have the ability to learn translation-invariant representations of objects (10). This has led to remarkable performance increases for image identification (11) and generation (12-14).
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