Development of an Ultrasound Lab Laura Wade April 4 th Z

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 = 2f 0 (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. A 1 v 1 = A 2 v 2

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 3 rd and 4 th 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?