Browsing by Subject "Aorta"
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Item An Automated Tool for Measuring Aortic Pulse Wave Velocity(2013-01-22) Goel, Akshay; Peshock, Ronald M.; McColl, Roderick; King, Kevin; Whittemore, AnthonyPURPOSE: Aortic Pulse wave Velocity (APV) has been shown to be associated with end organ damage independent of age, sex, and hypertension duration. The purpose of this study is to evaluate an automated approach for computing transit time (Δt) for the measurement of APV as a tool for future investigations and clinical application. METHODS AND MATERIALS: Phase contrast cardiac gated MRI of the aorta in the transverse plane at the level of the pulmonary artery was utilized from the Dallas Heart Study-2 (DHS2), a multiethnic, population-based study of cardiovascular health. A three-step algorithm was used to analyze all 1884 phase contrast MRI studies from the DHS2 central database. The algorithm functions in three key steps: 1) Isolating contours for the ascending aorta and descending aorta using a computer vision technique known as the Hough Transform. 2) Using isolated contours and phase contrast MRI to generate flow curves for the ascending and descending aorta. 3) Computing Δt defined as the time shift between the flow curves in the ascending aorta (AA) and descending aorta (DA), calculated using the half maximum of AA and DA. Fifty of these studies uniformly distributed across all Δt were then randomly selected and manually analyzed with the standard approach utilizing QFlow (v. 4.1.6, Medis) and the corresponding manually derived flow curves were used to compute Δt. The results from the manual analysis using QFlow were compared to results from the automated algorithm using linear regression Bland-Altman difference analysis. RESULTS: The mean Δt in the 1884 studies analyzed with our automated tool was 19.8+/-6.5 ms. In the validation set of 50 studies, linear regression analysis showed an excellent correlation between the automated (A) and manual (M) methods (r=0.97, A = 1.01M-0.885 ms). Bland-Altman difference analysis showed strong agreement with no significant bias (mean difference (A-M) = -0.386 ± 0.768 ms). CONCLUSION: Our automated approach for computing transit time (Δt) for the measurement of APV demonstrates excellent agreement with the standard manual method. These findings suggest this approach could serve as a useful tool for future investigations and clinical application.Item Developing a Real-Time, Axially Resolving Optical Monitor of Spinal Cord Blood Flow(2019-01-22) Gao, Feng; Busch, David R.; Goh, Chia Chieh; Lin, Wei; Yodh, Arjun G.; Floyd, Thomas F.BACKGROUND: Spinal cord ischemia is a disease of high morbidity and mortality often caused by surgeries repairing the thoracic and abdominal aorta. Current methods to monitor spinal cord hemodynamics such as electrophysiology methods, MR arterial spin labeling, and laser Doppler either have a slow response time or are unfeasible intra-operatively. In this study, we developed an optical probe to monitor spinal cord blood flow and oxygenation in real-time at multiple sites along the spine. METHODS: Experiments were conducted on 8 adult domestic pigs. Probes were inserted into the epidural space through a laminotomy prior to asphyxia and local ischemia via catheter balloon inflation. Vital signs, anesthetic parameters, and spinal hemodynamics were measured continuously prior to intervention, throughout asphyxia, and during inflation/deflation of the balloon catheter. Optical blood flow measurements were compared against microspheres. Optical hemoglobin saturation of spinal cord was compared to mixed venous blood gases. RESULTS: The fiber optic probe detected changes in flow and oxygenation in all asphyxia and balloon inflation trials across multiple sites along the spine. We observed significant changes in spinal cord blood flow during balloon inflation in the epidural space. We also observed a significant correlation between optically measured hemoglobin saturation and mixed venous blood gases. CONCLUSION: We developed an intra-operative tool that provides continuous, real-time monitoring of spinal cord hemodynamics at multiple sites along the spine. We hope this tool can more safely guide surgeons in reducing the incidence of spinal cord ischemia.Item Point of Care Ultrasonography by Novice Medical Students for Detecting Inferior Vena Cava Collapsibility, Aortic Diameter and Overall Left Ventricular Function in Euvolemic Pediatric Patients(2020-01-21) Dixon, Bryant; Han, Anthony; Hoang, Khiem; Cooper, Michael; Dickinson, Jennifer; Rendon, Juan Mark; Field, Steven; Roppolo, LynnBACKGROUND: Point of care ultrasound (POCUS) is a useful tool in assessing volume status and cardiac function in the emergency department (ED). Research has shown that medical students (MS) are capable of learning and performing POCUS, however further research is warranted to assess MS ability to perform POCUS, specifically in the pediatric population. METHODS: 5 MS were trained in POCUS techniques over a 2-week period. Training included a one hour lecture followed by hands on practice with the MS performing an average of 2.4 aorta scans, 4.4 IVC (inferior vena cava) scans and 6.8 cardiac scans on healthy pediatric and adult volunteers during the training period. MS then began staffing a pediatric ED 24 hours a day for 5 weeks in 12 hour shifts. The MS identified euvolemic patients age 13 years or younger and obtained written consent for 135 patients. The MS collected ultrasound images of the IVC, aorta, and heart with a parasternal long view and apical view of each patient. The MS assessed left ventricular ejection fraction, then measured IVC diameter and aorta diameter. Each scan was reviewed for quality of image acquisition and accuracy of interpretation by an ultrasound fellowship trained emergency medicine physician and reviewed by a second faculty if the first disagreed with the MS interpretation. Quality of the scans were graded based on the American College of Emergency Physician's emergency ultrasound standard reporting guidelines' 5-point scale with a score of 3 or above meeting minimum criteria for diagnosis. RESULTS: Each MS averaged 2.4 aorta, 4.4 IVC and 6.8 heart scans on healthy pediatric and adult volunteers during the training period. 135 patients age 1 week to 13 years were enrolled. Complete studies were available for 115 cardiac scans, 112 IVCs and 113 aortas. Faculty graded 110/115 cardiac scans 3 or above (95.6%; 95% CI 90.1-98.6%) and agreed with 106/112 MS interpretations (94.6%; 95% CI 88.7-98.0%). Faculty graded 95/112 IVC scans as a 3 or above (84.8%; 95% CI 76.8-90.9%) and agreed with 97/110 MS interpretations (88.2%; 95% CI 80.6-93.6%). Faculty graded 97/113 aorta scans as a 3 or above (85.8%; 95% CI 78.0-91.7%) and agreed with 99/111 MS interpretations (89.2%; 95% CI 81.9-94.3%). CONCLUSIONS: MS with minimal training can accurately detect IVC collapsibility, measure aortic size and assess cardiac contractility in euvolemic pediatric patients.Item [UT Southwestern Medical Center News](2007-09-10) Morales, Katherine