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Spring 2015 Senior Design College of Engineering The University of Georgia DEVELOPMENT OF AN EMBEDDED SYSTEM FOR ASSESSING EXTREMITY BLOOD VOLUMES BASED.

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Presentation on theme: "Spring 2015 Senior Design College of Engineering The University of Georgia DEVELOPMENT OF AN EMBEDDED SYSTEM FOR ASSESSING EXTREMITY BLOOD VOLUMES BASED."— Presentation transcript:

1 Spring 2015 Senior Design College of Engineering The University of Georgia DEVELOPMENT OF AN EMBEDDED SYSTEM FOR ASSESSING EXTREMITY BLOOD VOLUMES BASED ON ELECTROCARDIOGRAPHY Faculty Mentor: Zion Tsz Ho Tse Graduate Mentor: T. Stan Gregory Driftmier Annex, Room 120

2 ELECTROCARDIOGRAM (ECG) Main ECG Components PQRST QRS Complex Ventricular Contraction Synchronize Heart with external devices (Registration) S-T Segment Useful in Ischemia Detection Correlates to Peak Systolic Arterial Blood Pressure ECG Signal Features Are Shown to Correlate Directly With Arterial Blood Pressure

3 12-LEAD ECG Diagnostic Information Spatial & Temporal Detect Disease During Imaging CT, MRI, etc… Precordial electrodes V1-V6, illustrating spatial information obtained through 12-lead ECG recording

4 MAGNETIC RESONANCE IMAGING (MRI) High Quality Images Magnetic Field (B 0 ) Strong (1.5T, 3T, 7T,15T) Uniform Magnetic Gradients RF excites Protons RF energy released Subject Undergoing Exercise Stress Testing to Study Stress-Induced Variations in Aortic Blood Flow

5 INTRA-MRI ECG Cardiac MRI Synchronization Aids in CINE Studies Flow, CV Dynamics High-Risk Patient Monitoring Major Hurdles Gradient Noise Magnetohydrodynamics MRI-compatibility Cardiac MRI Scan Sagittal Aortic View “Candy Cane”

6 MAGNETOHYDRODYNAMIC (MHD) EFFECT MHD Voltages (VMHD) Induced in ECG due to interaction between B 0 & ionic blood flow Dominant during early systole Blood rapidly ejected from left ventricle to aorta MHD eclipses ECG in high field MRI, causing Distorted S-T Segment VMHD >> QRS complex Improper gating Image motion artifacts

7 ECG OVERLAY Healthy Subject Outside MRIHealthy Subject at 3 Tesla (T) Sensitivity in QRS Complex Detection is Reduced in Intra-MRI 12-lead ECG Recordings

8 MHD DIRECTIONALITY Induced VMHD is Dependent on Direction of Magnetic Field and Blood Flow B0B0

9 RELATIONSHIP TO BLOOD FLOW Aortic PC MRI, magnitude (top) & velocity- encoded (bottom) images High resolution, averaged over 30 cycles Hypothesis: Extracted MHD voltages directly correlate with aortic blood flow, and can be used to derive aortic blood flow in real time flow. Real-Time Phase Contrast MRI (RTPC) rather than conventional PC MRI must be used to achieve beat-to-beat validation.s

10 BLOOD FLOW CURVE FITTING Subject-Specific Fits Derived Based on Relationship to Blood Flow Subject-Specific Equations of Fit Can Be Derived to Fit Extracted VMHD to Aortic Blood Flow

11 ESTIMATE MHD VOLTAGE DISTRIBUTIONS Objective: Study contributions of regional vasculature and blood flow to the net MHD signal recorded in intra-MRI ECGs. Incremental Introduction into the MRI bore Raw ECGs (V4) obtained inside the MRI (3T) at each displacement level (d). Increases in VMHD contribution to signal are observed as the displacement from the bore isocenter is decreased.

12 LINEAR DECOMPOSITION OF LOCAL MHD CONTRIBUTION Local Segmental Perfusion (SP) calculated for a total displacement of N cm, and for M body regions Local field strength Bx as a function of distance from the isocenter Relationship of Global Perfusion (GP) to SP, where GP is attributed to weighted SP sums. SP describing local vasculature perfusion can be estimated from the equation

13 MHD-DERIVED PERFUSION DISTRIBUTION (Measured 2.80) MHD-derived Perfusion overlaid with MRI angiogram. Aortic arch locations indicated by vertical line occur at max VMHD in subjects 1-5. MRI images of aorto-femoral vasculature taken (coronal (left) & sagittal (right) views) Extracted VMHD & MRA based perfusion traces overlaid Correlation of 0.96 and 0.97 in perfusion levels for abdominal and thoracic cavities was found between the MRA and MHD-derived perfusion traces

14 SENIOR DESIGN PROJECT Objective: Convert this technology into a portable hand-held device that can be used bed-side by clinicians.

15 INA 128 – INSTRUMENTATION AMPLIFIER IC 1 st Steps!!! Get that ECG!!!!!

16 EASY ECG ACQUISITION 1.Breadboard the INA 128 circuit 2.Use leads + electrodes & vary the chip gain (external resistor) until you have a nice ECG 1.Record and document the circuit diagram into your notebooks 2.Record gain + resistor values + electrode positions used (tabulate) 3.Take an ECG using leads on (1) right/left hands, and (2) one arm 4.Use the o-scope, and take photos of nice ECGs obtained 3.Experiment with replacing electrodes with small squares of metal (< a few sq in) 4.How is the ECG signal? Does it require additional filtering? Diagnose it! 5.Acquire ECG signal using an Arduino (use the serial port monitor) 1.Remember the Arduino analog inputs only accept 0V to 5V 2.Plot a nice ECG using this data

17 NEXT WEEK Biomedical instrumentation design Typical ECG recorder flow chart (circuit block diagram) How would I modify it to record other physiological signals (EOG, EEG, etc…)? FDA Approval + 510k Premarket Notifications How to access your grades online? Everyone me a secret # to use as login into grades system.

18 QUESTION TIME Who likes CAD the best???? Names: -- Who likes to program a lot???? Names: --

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