Probe characteristics (shape and frequency) determine ultrasound image quality.

Linear probes with frequencies in the range 15-5 MHz produce high-resolution 2D images. The tissue penetration is limited to shallow depths (up to six centimeters). They are appropriate for vascular access and peripheral nerve blocks.

Curved array low-frequency probes 5-2 MHz allow deep tissue penetration in the abdominal and thoracic cavities. A high-frequency probe is preferred by some operators for lung ultrasound, because it provides better resolution of the pleura.

Cardiac phased array probes 7-1.5 MHz generate relatively good image quality combined with deep tissue penetration. They are conveniently shaped for scanning in the narrow spaces between the ribs and well suited for pleural evaluation.

Microconvex array probes 7-4 MHz produce good 2D images. They are very suitably shaped for scanning in the narrow spaces between the ribs and allow deep tissue penetration. They are suitable for pleural evaluation.

Ensure a power supply for the procedure – either by connecting to network voltage or sufficient battery capacity.

Connect the selected probe to the ultrasound system.

Select the appropriate ultrasound program – e.g. cardiac.

Often the ultrasound system automatically optimises the image depending on the chosen probe and ultrasound program.

Many ultrasound systems have multiple probe connectors that allow two or three probes to be connected to the system.

The operator can switch active probe by pushing a button or select from a menu on the monitor.

Turn the system “ON”.

The focal zone is the region within the transmitted sound beam in which the beam is most narrow. The lateral resolution is best within the focal zone of the beam.

Focusing increases the concentration of the energy at the depths where the beam is focused.

The focal zone should be adjusted to the depth of the examined structure. If the examined structure is large, it is expedient to increase the number of focal zones to three or four (i.e. increase the width of the focal zone). This keeps the beam narrow over a greater depth interval. However, there is a trade-off between the number of focal zones and the frame rate.

All ultrasound transducers use several operating frequencies.

The range of frequencies in ultrasound transducers is known as bandwidth.

An ultrasound system with broad bandwidth technology therefore has multiple operating frequencies.

This module will go through the key points of optimising the equipment and setup in order to obtain the best possible ultrasound image of the target.

The following key points will be explained:

? Preparation of the ultrasound (US) system
? Selection of the appropriate ultrasound probe
? Appropriate placement of the US system, the patient and yourself
? Probe orientation, grip and movement
? Anatomy planes
? Acoustic coupling with ultrasound gel
? How the ultrasound beam is equivalent to a tissue slice
? How to optimise the image quality (depth, gain and focus)
? Imaging modes (B mode, M Mode, Color Doppler and Power Doppler)
? How to freeze, save and measure
? Image recognition

Now you have completed the module about system controlled imaging.

You have obtained an understanding of:

– the basic functional groups of an ultrasound system

– the image operating modes

– the beam geometry