ABSTRACT
Doppler optical coherence tomography (OCT) is a noninvasive imaging modality that provides quantitative flow information with high spatial and temporal resolution. However, it is only sensitive to the flow velocity vector parallel to the incident beam. To calculate the absolute velocity, it is necessary to obtain the angle between the incident beam and flow field. In this paper, we describe a practical method to measure the Doppler angle based on the structural information of blood vessels extracted from spectral domain OCT images. In this method, a normal sectional scan of the vessel is performed where the probe beam is perpendicular to the vessel. Next, the axial diameter (Z direction) of the vessel (DA) was measured in the acquired image. For a certain scan in which the probe beam is oblique to the blood vessel, the axial diameter of the vessel (DA') can be measured. Thus, the Doppler angle can be calculated depending on the ratio of DA and DA', and absolute blood flow was determined. We validate this method in a capillary tube as well as in large blood vessels of early-stage chick embryos. This technique is suitable for early-stage embryo blood-flow measurement because most of the blood vessels are easily differentiated from the transparent surrounding structures during that time.
Subject(s)
Blood Flow Velocity/physiology , Blood Vessels/physiology , Tomography, Optical Coherence/methods , Animals , Chick EmbryoABSTRACT
BACKGROUND: The profiles of gastroesophageal reflux (GER) and laryngopharyngeal reflux (LPR) in patients with obstructive sleep apnea/hypopnea syndrome (OSAHS) have never been explored. The aim of the study was to investigate the reflux profile in OSAHS patients. METHODS: Consecutive snoring out-patients suspected with having OSAHS and 20 healthy volunteers were included. All subjects underwent simultaneous 24-h combined multichannel intraluminal impedance-pH (MII-pH) monitoring and polysomnography. Obstructive sleep apnea/hypopnea syndrome was defined when the apnea/hypopnea index was over 5. Stepwise multiple logistic regression analysis was performed to determine the predictor for OSAHS. KEY RESULTS: Fifty-three patients were included, 37 with and 16 without OSAHS. The prevalence of reflux symptoms was similar between OSAHS (35.1%) and non-OSHAS (37.5%) patients. More OSAHS patients, compared with non-OSAHS patients and healthy volunteers, had pathologic acid GER, nocturnal acid GER, and prolonged acid clearance (P < 0.001). However, no difference in non-acid reflux episodes was observed among the three groups. Laryngopharyngeal reflux was detected in 51.4%, 43.8%, and 35.0% of OSAHS, non-OSAHS, and healthy volunteers, respectively (P = 0.034). In OSAHS patients, there was no difference in the sleep parameters between patients with and without LPR. Body mass index was the only predictor of OSAHS in the regression analysis. CONCLUSIONS & INFERENCES: OSAHS patients have more pathologic acid GER and prolonged acid clearance than non-OSAHS patients whereas non-acid reflux was similar between the two groups. However, BMI, not GER, is the only independent predictor for OSAHS. Laryngopharyngeal reflux occurs in more than half of OSAHS patients despite no significant association with OSAHS.
