Ultrasound Science, Haemodynamics and Instrumentation

Module details

Title

Ultrasound Science, Haemodynamics and Instrumentation

Type

Specialist

Module code

SPS128

Credits

20

Requirement

Compulsory

Aim of this module

This module will provide trainees with the underpinning scientific knowledge and practical skills to safely and competently use ultrasound instrumentation to assess the anatomy and haemodynamics of the peripheral vascular system.

Competencies

#	Learning outcome	Competency	Action
# 1	Learning outcome 1	Competency Manipulate an ultrasound probe to acquire B Mode images of arteries and veins in longitudinal and transverse cross-sections.	Action View
# 2	Learning outcome 1	Competency Acquire optimised B Mode images of arteries and veins by demonstrating the effect of different B Mode control settings and processing options.	Action View
# 3	Learning outcome 1	Competency Identify the normal and diseased features of arteries and veins on a B Mode image.	Action View
# 4	Learning outcome 2	Competency Manipulate an ultrasound probe to acquire colour Doppler images of arteries and veins in longitudinal and transverse cross-sections.	Action View
# 5	Learning outcome 2	Competency Acquire optimised colour Doppler images of arteries and veins by demonstrating the effect of different colour Doppler control settings and processing options.	Action View
# 6	Learning outcome 2	Competency Identify the normal and diseased features of arteries and veins on a colour Doppler image.	Action View
# 7	Learning outcome 3	Competency Manipulate an ultrasound probe to acquire Doppler spectra from images of arteries and veins in longitudinal and transverse cross-sections.	Action View
# 8	Learning outcome 3	Competency Acquire optimised Doppler spectra from images of arteries and veins by demonstrating the effect of different Doppler control settings and processing options.	Action View
# 9	Learning outcome 3	Competency Identify the normal and diseased features of arteries and veins from their Doppler spectra.	Action View
# 10	Learning outcome 4	Competency Recognise, identify the cause and minimise artefacts affecting the B Mode image, the colour Doppler image and the Doppler spectrum.	Action View
# 11	Learning outcome 5	Competency Make accurate measurements of distance and area on B Mode images.	Action View
# 12	Learning outcome 5	Competency Make accurate measurements of velocity on Doppler spectra.	Action View
# 13	Learning outcome 5	Competency Correctly label and record images.	Action View
# 14	Learning outcome 6	Competency Identify the safety features available on ultrasound instrumentation and manipulate controls to minimise the bio-effects and hazards of ultrasound.	Action View
# 15	Learning outcome 7	Competency Make measurements as part of the QA programme, including assessment of caliper positioning.	Action View

Assessments

You must complete:

• 4 case-based discussion(s)
• 4 of the following DOPS/ OCEs:

Acquire optimised B Mode images of the carotid bifurcation in transverse and longitudinal views	DOPS
Acquire optimised B Mode images of the common femoral vein and sapheno femoral junction, demonstrating valves and the effects of compression.	DOPS
Acquire optimised B Mode images of an Abdominal Aortic Aneurysm in transverse and longitudinal views.	DOPS
Acquire optimised B Mode images a segment of varicose vein	DOPS
Acquire optimised B Mode and Colour Doppler images of a segment of lower limb bypass graft and either proximal or distal anastamosis.	DOPS
Acquire optimised B Mode and Colour Doppler images of a segment of femoral vein demonstrating phasicity and effect of augmentation.	DOPS
Acquire optimised B Mode and colour Doppler images of a diseased SFA or popliteal	DOPS
Acquire optimised B Mode and colour Doppler images of postphlebitic femoral vein	DOPS
Acquire optimised B Mode, colour Doppler and Doppler spectra from the common carotid and vertebral arteries.	DOPS
Acquire optimised B Mode, colour Doppler and Doppler spectra along a diseased SFA or popliteal.	DOPS
Acquire optimised B Mode, colour Doppler and Doppler spectra from a common femoral vein demonstrating phasicity, valsava manouvre and distal augmentation.	DOPS
Acquire optimised B Mode, colour Doppler and Doppler spectra from an incompetent vein to demonstrate reflux.	DOPS
Acquire optimised B Mode images demonstrating reverberation and slice thickness artefact in an artery or vein.	DOPS
Acquire optimised B Mode and colour Doppler images of the vertebral artery and vein to demonstrate acoustic shadowing	DOPS
Acquire optimised B Mode and colour Doppler images in the iliac arteries to demonstrate acoustic shadowing, aliasing and movement artefacts.	DOPS
Acquire optimised B Mode and colour Doppler images of the subclavian artery to demonstrate mirror image arterfact, acoustic shadowing and aliasing.	DOPS
Acquire B Mode, colour Doppler and Doppler spectra to demonstrate aliasing in a diseased carotid artery.	DOPS
Acquire B Mode, colour Doppler and Doppler spectra to demonstrate aliasing in a diseased SFA popliteal artery	DOPS
Acquire, label and store optimised B Mode images of aorta, common femoral and popliteal artery and measure the diameter in transverse and longitudinal orientations.	DOPS
Acquire, label and store optimised B Mode images of the long saphenous vein and take diameter measurements along its entire length.	DOPS
Acquire, label and store optimised B Mode images of a carotid plaque e.g. on pre endarterectomy patient and measure calculate the diameter and area reduction.	DOPS
Acquire, label and store optimised B Mode, colour Doppler and Doppler spectra from internal and common carotid arteries, measure the peak systolic and end diastolic velocities and calculate the ratios.	DOPS
Acquire, label and store optimised B Mode, colour Doppler and Doppler spectra from an incompetent vein to demonstrate and measure reflux time.	DOPS
Acquire, label and store optimised B Mode, colour Doppler and Doppler spectra from a fistula and calculate the volume flow rate.	DOPS
Acquire, label and store Doppler spectra from an artery with a range of insonation angles, measure peak systolic velocity and analyse the effects on calculated velocity	DOPS
Acquire, label and store Doppler spectra from an artery with a range of insonation angles, and then measure effect of angle correction errors on the peak systolic velocity for each insonation angle.	DOPS
Acquire, label and store Doppler spectra from an artery using a range of sample volume sizes and positions and analyse the effect on the spectral waveform shape and measurements.	DOPS
Adjust and analyse B Mode, colour Doppler and Doppler spectra settings on a range of transducers to demonstrate lowest and highest possible mechanical and thermal indices.	DOPS
Perform and interpret B Mode QA measurements	DOPS
Perform and interpret Doppler QA measurements	DOPS
Explain the arterial scan procedure and purpose to the patient	OCE
Explain the venous scan procedure and purpose to the patient	OCE
Explain the graft scan procedure and purpose to the patient	OCE
Obtain patient consent for the arterial scan	OCE
Obtain patient consent for the venous scan	OCE
Obtain patient consent for the graft scan	OCE
Obtain the relavant clinic history and symptoms pertinent to the arterial scan.	OCE
Obtain the relavant clinic history and symptoms pertinent to the venous scan.	OCE
Obtain the relavant clinic history and symptoms pertinent to the graft scan.	OCE
Prepare and position a mobile patient for the arterial scan	OCE
Prepare and position a mobile patient for the venous scan	OCE
Prepare and position a mobile patient for the graft scan	OCE
Prepare and position a patient with mobility difficulties for the arterial scan	OCE
Prepare and position a patient with mobility difficulties for the venous scan	OCE
Prepare and position a patient with mobility difficulties for the graft scan	OCE
Communicate with the patient during the scan to explain the practical aspects of the arterial scan e.g. leg position	OCE
Communicate with the patient during the scan to explain the practical aspects of the venous scan e.g.augmentation	OCE
Communicate with the patient during the scan to explain the practical aspects of the graft scan e.g. leg position	OCE
Explain the arterial scan findings to the patient	OCE
Explain the venous scan findings to the patient	OCE
Explain the graft scan findings to the patient	OCE
Explain to a patient what happens with the arterial scan results	OCE
Explain to a patient what happens with the venous scan results	OCE
Explain to a patient what happens with the graft scan results	OCE

Learning outcomes

1. Acquire an optimised B-mode image and evaluate the characteristic features of a normal and diseased artery and a vein on a B-mode ultrasound image.
2. Acquire an optimised colour Doppler image and evaluate the characteristic features of a normal and diseased artery and a vein on a colour Doppler image.
3. Acquire an optimised Doppler spectrum and evaluate the characteristic features of a normal and diseased artery and a vein on a Doppler spectrum with both imaging and non-imaging instrumentation.
4. Recognise, identify the cause and minimise artefacts affecting the vascular B- mode image, colour Doppler image and Doppler spectrum.
5. Obtain, record and calculate quantitative measurements from B-mode images and spectral Doppler traces. Label, record and store ultrasound images and data.
6. Identify the safety features and displays available on ultrasound instrumentation. Critically evaluate their importance and relevance and be able to manipulate controls to minimise the bio-effects and hazards of ultrasound during the acquisition of ultrasound images and Doppler spectra.
7. Carry out quality assurance (QA) measurements and safety assessments on an ultrasound machine and critically evaluate their relevance to Vascular Science.

Learning outcomes

1. Describe and critically evaluate the fundamental scientific principles inherent in an ultrasound image.
2. Describe the design, operation and features of vascular ultrasound instrumentation.
3. Describe the histology of arteries and veins and describe how these features are represented on an ultrasound image.
4. Discuss the haemodynamics of blood flow through normal and diseased peripheral arteries and veins and how these characteristics are represented with Doppler ultrasound.
5. Describe and critically evaluate the artefacts inherent or produced in a vascular ultrasound image/spectra and explain how they can be recognised, utilised and minimised by the user.
6. Explain and critically evaluate the accuracy, precision and sources of errors in vascular ultrasound measurements.
7. Recognise and critically evaluate the importance of labelling images, and the different methods used for storage, retrieval and post-processing of data.
8. Explain and critically evaluate the safety of diagnostic ultrasound, describe the current national safety recommendations and guidelines.
9. Describe and critically evaluate the role of quality assurance and safety assessments in an ultrasound department.
10. Recognise the range, advantages and limitations of quality assurance measurements used to assess ultrasound machines.

Indicative content

The fundamental scientific principles of diagnostic ultrasound

• Wave motion
• Frequency, speed, wavelength, acoustic pressure, intensity, power, speed of sound, bulk modulus, density, frequencies and wavelengths used in diagnosis
• Reflection, transmission, acoustic impedance, scattering, diffuse reflection, refraction, attenuation, ultrasound beams, focusing, the ultrasound pulse, non- linear propagation

 

Transducers and beam-forming

• Piezoelectric effect, ceramic elements
• Transducer construction
  • Basic components
  • Resonance frequency
  • Backing material
  • Impedance matching
  • Beam former and its electronics
  • Beam directivity
  • Near field, far field
  • Focusing
  • Transmit focus, dynamic receive focus
  • Dynamic aperture
  • Side lobes, grating lobes
  • Linear array
  • Curvilinear array
  • Phased array
  • Annular arrays
  • Mechanically scanned probes
  • Endo probes
  • Damage to transducers
• 5 D and 2 D arrays
• Dynamic slice thickness focusing
• Beam aberration

Pulse-echo instrumentation

• The range equation
• Duty factor
• Beam former
• Pulse transmitter
• Receiver
• Signal amplitude processing
• Amplification
• Analogue-to-digital conversion
• Amplitude demodulation
• Dynamic range and compression
• B-mode
• M-mode
• Harmonic imaging
• Image storage and display
• Scan converter
• Writing, reading and image freeze
• Interpolation
• Read zoom, write zoom
• Pre-processing, post-processing
• Compound imaging
• Adaptive processing
• Control nomenclature
• Control settings
• Time Gain Compensation (TGC)
• Dynamic range

 

Properties, limitations and artefacts of B-mode images

• Imaging system performance
• Artefacts (reverberation, mirror image, beam width artefacts, side lobes, grating lobes, slice thickness artefacts, shadowing and enhancement, speed of sound artefacts)
• Axial resolution, lateral resolution, slice thickness, frame rate, speckle
• Contrast resolution

 

B- mode measurements

• Measurement systems
• Distance, area and volume computations
• Measurement errors, sources of errors
• Precision and accuracy
• Interpretation of measurements

 

Principles of Doppler ultrasound

• Nature of the Doppler shift
• The Doppler equation
• Doppler ultrasound systems
• Signal received by transducer
• Continuous wave Doppler signal processor
• Continuous wave Doppler transducers
• Directional Doppler
• Origin and processing of the Doppler signal for pulsed wave systems
• Aliasing, sample volume size, time-domain systems

Blood flow

• Histology/structure of vessel walls
• Laminar, disturbed and turbulent flow, velocity profiles
• Resistance to flow
• Physiological and pathological changes that affect the arterial flow
• Venous flow
• Composition of blood
• Echogenicity of blood

 

Spectral Doppler ultrasound

• Spectral display
• Doppler ultrasound systems
• Spectral analysis
• Spectral Doppler controls
• Factors that affect the Doppler spectrum
• Angle insonation, angle correction
• Optimising the display
• Spectral broadening
• Effect of pathology on the Doppler sonogram
• Artefacts
• Aliasing
• High PRF mode
• Measurements and sources of errors

 

Colour flow imaging

• Colour flow system components
• Acquiring and processing echo signals
• Phase shift autocorrelation
• Colour flow modes
• Colour controls
  • Power
  • Gain
  • Scale
  • Focusing
  • Transmitted frequency
  • Colour assignment
  • Filter
  • Line density
  • Ensemble length and interraction with frame rate
  • Colour/B-mode priority
  • Beam steering
• Features of colour flow
• Properties of colour displays

Display output and storage

• Displays for ultrasonic equipment
• Printer technologies
• Digital-imaging networks
• PACs
• Responsibility for images

 

Quality assurance

• Clinical and technical assessment
• Applications of quality assurance
• Setting up a quality assurance program
• Standards and guidelines
• Test objects and tissue-mimicking phantoms for B-mode imaging
• Performance testing of B-mode systems
• Testing of spectral Doppler and colour flow systems

 

Procurement of ultrasound equipment

• Specification
• Evaluation

 

Safety of diagnostic ultrasound

• Risk and hazard
• Ultrasound exposure, power, intensity, pressure, acoustic output of diagnostic machines, tissue effects
• Mechanisms for the production of biological effects (ultrasound induced heating, mechanical bio-effects)
• Managing safety
• Thermal Index
• Mechanical Index
• Safety for specific use of diagnostic ultrasound epidemiology studies, in vitro cell studies
• Current safety standards and regulations
• Users’ responsibilities

 

Technology

• Contrast agents
• 3D
• Tissue motion
• High-frequency imaging
• Intravascular ultrasound imaging
• Elastography
• Techniques with clinical potential
• Clinical assessment of new technology

Cardiovascular haemodynamics

• Fluid properties (density, viscosity)
• Volume flow (volume flow equation)
• Energy density (potential energy, kinetic energy)
• Blood pressure
• Bernouilli principle
• Poiseuille’s equation
• Peripheral vascular resistance
• Streamlines
• Velocity profile (parabolic flow, plug flow)
• Pulsatile flow
• Flow waveforms
• Pulse wave velocity
• Wave reflections
• Relationship between flow waveform and flow
• Turbulence and Reynolds number
• Turbulence due to geometry
• Flow through a stenosis (energy changes across a stenosis), entrance effects (viscous diffusion, inlet length)
• Fluid jets
• Flow in curved tubes (centrifugal force)
• Bifurcations and confluences
• Vessel diameters (circumferential stress)
• Venous pressures
• Vessel collapse
• Mechanics of valves
• Moens-Korteweg equation
• Artefacts
• Colour aliasing
• Time domain colour flow systems
• Measurements, Doppler power mode

Activities

• Prepare a portfolio of images from a series of patients that demonstrate the normal and diseased features of arteries and veins on B Mode, colour Doppler and the Doppler spectra (learning outcomes 1, 2 and 3).
• Critically appraise the effect of probe manipulation, pressure (compression) and technique on the quality of the images and spectra and reflect on how this may affect the diagnosis. A portfolio of evidence should include images obtained from a variety of anatomical locations (e.g. neck, abdomen, leg) and clearly demonstrate the effects of probe manipulation, pressure and technique on the longitudinal and transverse images (i.e. one optimised image may be accompanied by many suboptimal images).
• Critically appraise the effect of machine controls and processing options on the images and spectra and reflect on how this may affect the diagnosis. A portfolio of evidence should include images obtained with a variety of probes (e.g. curvilinear, linear, phased array) from a variety of anatomical locations (e.g. neck, abdomen, leg) and clearly demonstrate the effects of machine controls (e.g. frequency selection, depth, gain, focus, dynamic range, PRF, angle correction, frame averaging, sample volume size) and processing options (e.g. harmonics, compound imaging, speckle reduction) on the longitudinal and transverse images (i.e. one optimised image may be accompanied by many suboptimal images).
• Critically appraise the characteristic appearance of arteries and veins and reflect on how these images are altered in the presence of a variety of diseases. A portfolio of evidence should include images obtained from a variety of vessels (e.g. carotid artery, aorta, iliac artery, popliteal artery, femoral vein, long saphenous vein) and clearly demonstrate a range of pathology (e.g. mild atheroma, severe atheroma, calcification, aneurysm and thrombus) and the effects on the B Mode image, the colour image and the Doppler spectrum.
• Prepare a portfolio of images from a series of volunteers, patients or phantoms that demonstrate the artefacts present on B Mode, colour Doppler and the Doppler spectra (learning outcome 4).
• Critically appraise the impact artefacts have on accurately representing anatomy/physiology and reflect on the hindrance or usefulness of artefacts in a diagnosis. A portfolio of evidence should include images that demonstrate a range of artefacts, including reverberation, mirror image, beam width/slice thickness artefacts, shadowing, enhancement, spectral broadening, aliasing.
• Prepare a portfolio of images from a series of volunteers, patients or phantoms that demonstrate correctly labelled quantitative measurements on B mode images and Doppler spectra (learning outcome 5).
• Critically appraise the precision and accuracy of quantitative measurements and reflect how errors may affect the diagnosis. A portfolio of evidence should include images obtained with a variety of probes (e.g. curvilinear, linear, phased array) from a variety of vessels (arteries and veins), and clearly demonstrate the effect of machine controls (e.g. zoom, gain, angle correction) on measurements of distance, area and velocity.
• Critically appraise the relevance of labelling and recording images and reflect on how this affects the diagnosis. A portfolio of evidence should include images obtained from a variety of vessels (e.g. right and left carotid artery) with appropriate labelling.
• Prepare a portfolio of images (with transducer in air) to demonstrate the effect of the instrumentation controls and user input on the safety indices displayed (learning outcome 6).
• Critically evaluate the effect of manipulating various controls (e.g. power, depth, focus, Doppler) on the value of the safety indices and reflect how you may cause harm to a patient. A portfolio of evidence should include values obtained with a variety of probes (e.g. curvilinear, linear, phased array) for a variety of control settings, demonstrating the variation in safety indices values and where these exceed safety recommendations.
• Participate in routine QA measurements on a range of probes on an ultrasound imaging machine, including visual inspection, crystal drop-out, image uniformity, sensitivity, noise, calliper accuracy, dead zone, resolution (axial, lateral, slice thickness) and cystic target detection (learning outcome 7).
• Critically evaluate the QA results between different probes and reflect on how this may affect image quality and diagnostics accuracy. A portfolio of evidence should include your QA report and images demonstrating all the measurements on the different probes.
• Critically appraise the relevance of a QA programme for a vascular department and discuss with your trainer.