BEE 531 Ultrasound Imaging

Where does ultrasound fit in diagnostic imaging?

• Other imaging modalities
• Advantages of US
• Disadvantages of US
• When is US used?

Computed x-ray tomography (CT)

Advantages

• Estimates x-ray absorption
• Access to volumes
• Widely available in certain areas.

Disadvantages

• Adds to cumulative lifetime radiation exposure
• Length of acquisition ~ 20 min (motion)
• Cost $400-700

Magnetic Resonance Imaging

Advantages

• Estimates magnetic relaxation times (i.e. T1/T2).
• Access to volumes
• No radiation.

Disadvantages

• Availability ($1-3 million).
• Length of acquisition ~ 20 min (motion)
• Cost $700-1200

Nuclear - (includes PET)

Advantages

• Estimates cellular function/ activity.
• Access to volumes
• Very sensitive.

Disadvantages

• Radiation.
• Radiotracer short half lifes made in cyclotron (2 cyclotrons in South Seattle).
• Availability restricted.
• Length of acquisition/ resolution ~ 20 min (motion).
• Cost ~$300-3000 (PET $~6000

Ultrasound

Advantages

• Estimates backscatter of ultrasound waves.
• No radiation.
• Highly portable
• Real time (used often to guide interventional procedures)
• Low cost $100-200

Disadvantages

• Limited access in some circumstances.
• Access to brain
• Difficult to access to abdominal organs.
• Limited access to volumes.
• Acoustically difficult patients.
• Cost $100-200

Why ultrasound?

• Low cost
• No radiation
• Non-invasive
• Highly portable
• Real-time imaging

Why I love ultrasound?

• Impacts lives of others
• Expanding applications user base/capabilities
• Lots of cool gadgets/technology (transducers, math, processing, computing/cpu/gpu
• Figure out new problems and how biological processes

Big shifts in Ultrasound imaging

• Miniaturisation/portability pushing ultrasound into new places/uses
• Increase in computation (both gpu/cpu) enabling new opportunities
• New transducer technologies
• Artificial Intelligence

Ultrasound Market

Pacific Northwest Ultrasound Companies

Cardiology-Echocardiology

Obstetrics/Gynecology

Obstetrics/Gynecology

Obstetrics/Gynecology

Ultrasound system interface

Ultrasound timeline

Components of an ultrasound system

Components

• Transducer/connector
• Front end/Data acquisition board
• PCI express to computer
• More processing on GPU
• Display to monitor
• Power supply

Departments of an ultrasound company

• Hardware group
• Software group
• Ultrasound dev group
• Acoustic measurement group
• Clinical applications
• Marketing
• Sales
• Legal
• Administration

How does ultrasound work?

Echo location

Ultrasound

Sound propagation in different medium

How do we generate ultrasound waves

• Piezoelectric crystals
• Apply voltage
• Crystals vibrate at MHz frequencies

Principle of ultrasound image formation

Week 1: Wave propagation and ultrasound physics

• Wave equation.
• Description of wave propagation.
• Propagation in different materials.
• Time domain simulations.

Week 2: Diffraction and beams

• Integral solution of wave equation.
• Fourier analysis.
• Principles of diffraction.
• Relation of acoustic field and aperture function.

Week 3: Transducers/arrays and system architectures

Transducers and arrays

• Principles of electrical/acoustical transduction.
• Piezoelectric transducers.
• Transducer design and components.
• Transducer arrays.

System architectures

• "Conventional" system architecture and components.
• Modern system architecture.
• Portable/ultra-portable system.

Week 4: Signal processing tools

• Convolution.
• Fourier analysis.
• Complex numbers.
• IQ and Hilbert transform.

Week 5: Beam formation

• Diffraction equations for aperture.
• Transmit beamforming.
• Dynamic receive beamforming.

Week 7: B-mode imaging

• Ultrasound propagation in heterogenous media.
• Ultrasound scattering mechanisms.
• Principles of speckle.
• Real-time image reconstruction.
• Imaging controls and algorithms.

Week 8: Doppler Processing/imaging blood flow

• Basics of blood flow.
• Doppler physics.
• PW Doppler processing.
• Color Doppler processing.
• Plane wave Doppler imaging.

Week 9: Ultrasound contrast agents

• Introduction to microbubbles.
• Nonlinear response of microbubbles.
• Modes of oscillation.
• Imaging microbubbles.

Week 10: Shear-wave Elastograpy

• Elastic properties of solids.
• Wave equation for elastic waves.
• Estimation of elastic modulus.
• Shear-wave imaging.
• Applications of SWE.

Week 11: Nonlinear/harmonic imaging

• Fundamentals of nonlinear propagation.
• Benefits of nonlinear imaging.
• Nonlinear scattering.
• Different approaches to imaging nonlinear echoes.