Development of an Ultrasound Lab Laura Wade April 4 th 2012 3970Z.
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Transcript of Development of an Ultrasound Lab Laura Wade April 4 th 2012 3970Z.
Development of an Ultrasound Lab
Laura WadeApril 4th 2012
3970Z
Introduction
• Piezoelectric – an alternating voltage across the crystal causes it to flex and contract, emitting sound.
• Piezoelectrics also generates alternating voltage in response to a returning sound wave.
• It emits sound waves and receives them.
• Speed of sound depends on compressibility of a material
• Acoustic Impedance (Z) is a measure of resistance to sound waves.
• Large differences in Z create strong refections (signals)
• B Mode Imaging
• Produces a 2D grayscale Image. • Brightness is proportional to amplitude of the
reflected sound waves. •The time at which the signals are received indicates depth.
c= 2D/t
• Colour Doppler• Velocity information is represented by colour and is
overlaid onto a 2D B-Mode image.• Velocity is determined using the Doppler effect:
Δf = 2f0 (v/c) cosα
• Pulse Wave Doppler: velocity is measured at a specific depth, which
can be adjusted
• Continuous Wave Doppler: measures all velocities along the ultrasound
beam. It provides no information about depth of the signal.
Colour Power Doppler:• Displays the amplitude of the frequency shift.
• Amplitude is a function of the number of reflectors (RBCs) with that velocity.
• Colour is still used to determine direction
Objectives
• Develop an experiment using sonography to measure blood flow in the carotid artery.
• Develop a complete set of instructions for the operation of the equipment as it applies to this lab.
• Determine a way to analyze the data acquired from the sonographs.
Approach
• Research the theory behind ultrasound• Master the technical systems to be used in the
lab• Research possible parameters and treatments
to use in the lab• Develop appropriate protocol
Hypotheses
• Sonography can be used to verify continuity of flow in the carotid artery.
• Increasing both physical and mental activity will increase blood flow in the carotid arteries.
Methods• Carotid Ultrasound
Carotid is located at a depth of 3-4cm beneath the surface of the skin.
•Remember to calibrate the system to the angle the transducer is held at.
• Sonosite 180•A 38-element linear array transducer is used
•Uses frequency of 5MHz
Measurements and Calculations
• Flow in the right carotid before and after the carotid bifurcation using PWD.
• A1v1 = A2v2
• Cardiac Output (CO)
•Measure peak systolic velocity and end diastolic velocity.
•Calculate Volume Flow Rate (CBF)
•Use known relationship to calculate CO
• Cerebral Blood Flow (CBF) before and after exercise and/or mental activity
• Volume Flow = Area * Velocity
Results• CBF = ~750mL/min at rest• Flow in the carotid before and after the
bifurcation is equal.• CO = 5 – 5.5 L/min at rest• Flow in the carotid is increased during both
exercise and increased mental activity. • Paired t – test results in significance with
p<0.05.
Discussion
• Why should we incorporate this lab into the 3970Z curriculum? – Ultrasound is covered in both 3rd and 4th year
courses – Noninvasive, inexpensive, and therefore common
imaging technique
• Sources of Error
• Inaccurate measurement of cross sectional area.
• Inaccurate angle correction.
• Noise
• Questions for Discussion:
– Would the effectiveness of sonography be different for an obese patient? Why?
– Would ultrasound be effective for imaging blood vessels in the torso?
– How could an occluded blood vessel be detected?– What would be the effect of not using lubrication
between the skin and transducer?
Acknowledgements
I would like to thank:• Dr. Ian MacDonald, Supervisor• Michelle Belton, Lab Manager
Thank you for your time.
Any Questions?