The first steps of performing an ultrasound involve:
- Turning on the machine (easy, but often overlooked; often a button in the upper left or right corner of the keypad).
- Entering the patient’s information (e.g. name, date of birth, hospital number).
- Selecting an appropriate ultrasound probe for the area being examined.
How do I know which probe I should use?
Typically there are 3 different types of ultrasound probe: linear, curvilinear and phased.
- High frequency (7-15MHz):
- High resolution but superficial (1-6cm) depth
- Good for vascular access, nerve blocks, assessment of testes and superficial lung tissue
- Low frequency (2-5MHz)
- Low resolution, but greater depth (10-20cm)
- Useful for abdominal, pelvic, obstetric and deep lung tissue
- The lowest frequency (1-3MHz)
- Useful for echocardiography
How do I hold the probe?
The image below demonstrates how to appropriately hold an ultrasound probe.
Typically, there is a dot or a cross on the probe, this correlates with a dot on the left side of the screen.
This marker should be toward the patient’s right in transverse and head in longitudinal.
If you are unsure, it is best to place your finger on one side of the probe and look for movement on the screen (the side that shows movement by the dot is the side that should face the patient’s right).
Once you’ve chosen an appropriate probe and are holding it right, the next steps of performing an ultrasound involve:
- Applying gel to the probe and patient.
- Placing the probe onto the patient and observing the images on the screen.
- Adjusting the settings to achieve an optimal view.
Common settings for achieving an optimal view
- Adjusting the gain of an ultrasound changes the brightness of the image.
- Gain is typically controlled by a knob.
- The gain should be adjusted until fluid appears black and soft tissue appears mid-grey with some parts of the image appearing white
- Depth measures are shown in cm on the side of the ultrasound monitor.
- It is often best to begin deep to orientate yourself and then work more superficially to bring the object of interest into the middle of the screen.
General tips for achieving an optimal view
Some general tips for achieving an optimal view include:
- Use lots of gel
- Make good contact between the probe and skin (whilst ensuring the patient is comfortable)
- Dim the lights to improve your view of the monitor