Academic radiology
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Cerebral oxygen extraction, defined as the difference between arterial and venous oxygen saturations (SaO2 and SvO2), is a critical parameter for managing intensive care patients at risk for neurological collapse. Although quantification of SaO2 is easily performed with pulse oximetry or moderately invasive arterial blood draws in peripheral vessels, cerebral SvO2 is frequently not monitored because of the invasiveness and risk associated with obtaining jugular bulb or super vena cava (SVC) blood samples. ⋯ Respiration frequency-selected NIRS can noninvasively quantify cerebral SvO2. This bedside technique can be used to help assess brain health in neurologically unstable patients.
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Comparative Study
Microvascular versus macrovascular cerebral vasomotor reactivity in patients with severe internal carotid artery stenosis or occlusion.
In patients with severe internal carotid artery steno-occlusive lesions (ISOL), impaired cerebrovascular reactivity (CVR) is predictive of future ischemic stroke (IS) or transient ischemic attack (TIA). Therefore, the evaluation of CVR in ISOL patients may be a means to evaluate the risk for IS/TIA and decide on an intervention. Our aim was (1) to explore the feasibility of concurrent near-infrared spectroscopy (NIRS-DOS), diffuse correlation spectroscopy, and transcranial Doppler for CVR assessment in ISOL patients, and (2) to compare macrovascular and microvascular CVR in ISOL patients and explore its potential for IS/TIA risk stratification. ⋯ We demonstrated the simultaneous, continuous, and noninvasive evaluation of CVR at both the microvasculature and macrovasculature. We found that macrovascular CVR response depends on the presence of ISOL, whereas the microvascular CVR did not significantly depend on the ISOL presence, possibly due to the role of collaterals other than those of the circle of Willis. The concurrent microvascular and macrovascular CVR measurement in the ISOL patients might improve future IS/TIA risk assessment.
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Perturbations in cerebral blood volume (CBV), blood flow (CBF), and metabolic rate of oxygen (CMRO2) lead to associated changes in tissue concentrations of oxy- and deoxy-hemoglobin (ΔO and ΔD), which can be measured by near-infrared spectroscopy (NIRS). A novel hemodynamic model has been introduced to relate physiological perturbations and measured quantities. We seek to use this model to determine functional traces of cbv(t) and cbf(t) - cmro2(t) from time-varying NIRS data, and cerebrovascular physiological parameters from oscillatory NIRS data (lowercase letters denote the relative changes in CBV, CBF, and CMRO2 with respect to baseline). Such a practical implementation of a quantitative hemodynamic model is an important step toward the clinical translation of NIRS. ⋯ The ability to perform noninvasive measurements of cerebrovascular parameters has far-reaching clinical implications. Functional brain studies rely on measurements of CBV, CBF, and CMRO2, whereas the diagnosis and assessment of neurovascular disorders, traumatic brain injury, and stroke would benefit from measurements of local cerebral hemodynamics and autoregulation.
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To test the ability of quantitative measures from preoperative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to predict, independently and/or with the Katz pathologic nomogram, which breast cancer patients with a positive sentinel lymph node biopsy will have four or more positive axillary lymph nodes on completion axillary dissection. ⋯ Integration of DCE-MRI primary lesion kinetics significantly improved the Katz pathologic nomogram accuracy to predict the presence of metastases in four or more nodes. DCE-MRI may help identify sentinel node-positive patients requiring further local-regional therapy.
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To investigate whether "full" iterative reconstruction, a knowledge-based iterative model reconstruction (IMR), enables radiation dose reduction by 80% at cardiac computed tomography (CT). ⋯ The IMR can provide improved image quality at super-low-dose cardiac CT with 20% of the standard tube current.