All of the posts of the series Learning Ultrasound are excerpts from the book Point-Of-Care Ultrasound for Emergency Physicians — “The EDE Book”. I purchased the e book two years ago. The e book is only available on Apple devices. The e book is only about $15 and it is simply the best there is on learning to perform point of care ultrasound (POCUS). You need to buy it now.
I have posted these Learning Ultrasound series, temporarily, for a friend who does not currently have access to an Apple device.
This is the first in a series of posts to help all primary care clinicians quickly develop skill in primary care ultrasound [also called Point of Care Ultrasound (POCUS)].
The most important skill in primary care ultrasound is the ability to obtain high quality diagnostic images. As soon as you can do that you can easily transmit your studies over the internet to get immediate expert interpretation.
With experience you will quickly find your own interpretive skills rapidly developing. Sooner than you think you won’t need over read help to interpret your scans.
The very best resource for learning how to get reliably ultrasound scan images is the book, Point-Of-Care Ultrasound for Emergency Physicians — “The EDE Book”; “The clearest and most concise approach to emergency ultrasound.”
There is also an e-book of the above available but unfortunately it is only available on Apple devices. It is not available for Android or Windows users. But if you have an Apple device I strongly recommend that you purchase the e-book as it is only approximately $15.
Over the next ten (projected) posts I’ll cover the basics of ultrasound image generation.
All the illustrations are from the “The EDE Book” above.
So there are two planes that we’ll be scanning in: the transverse and the longitudinal
In the transverse plane the probe indicator always points to the right side of the patient.
In the longitudinal plane the probe indicator always points cephalad.
When you are scanning you always want to bring the are of interest to the center of the screen. To do this you will be moving the probe in a variety of different ways. And remember that the probe indicator is always to the patient’s right in the transverse view and towards the patient’s head in the longitudinal view.
So in the longitudinal imaging plane, to slide the image to the right, you will slide the probe towards the head of the patient.
Another way of putting it: in the longitudinal plane to slide the image towards the right, slide the probe in the direction of the indicator.
And in the transverse plane, to move the image to the right you will slide the probe towards the patient’s right or equivalently you will slide the probe in the direction of the indicator.
In the longitudinal plane, to slide the area of the interest to the left, you will slide the probe caudad or equivalently slide the probe away from the indicator.
In the transverse plane, to slide the area of interest to the the left, you will slide the probe to the patient’s left, or equivalently slide the probe away from the indicator..
Make slow small probe movements to scan successfully. Also learn to scan with either hand. You’ll want to hold the probe in the hand closest to the patient.
Sweeping the probe means that you leave the probe in the same position on the skin but change the angle at which the beam enters the body.
The ultrasound machine can be set to look at different depths. You should start your scan at the maximum depth. Once you’ve found what you are looking for, you want to decrease the depth to enlarge the object of interest.
At the correct depth, the object of interest will be centered on the screen.
If you set the depth too deep, then the object of interest will be too small and at the top of the screen.
If you set the depth too shallow, the area of interest will be cut off at the bottom of the screen.
There are a number of dials on the ultrasound scanner. You don’t need to know about them until we’re farther along in our scanning.
The Gain dial is the one we need to know about right now. Turning up the gain makes the whole image brighter (whiter). Turning down the gain makes the whole image darker(blacker). You’ll change the gain up or down depending on what structures you want to make stand out.
Below is an image where the Gain is turned up too high.
Here is a picture of the same area of the scan with the gain properly adjusted (turned down).
Artifacts are false images generated by the ultrasound scan waves. There are seven types of artifact that we need to know about: enhancement, shadowing, refraction (edge artifact), reverberation, comet tails, mirror artifact, and slide lobe artifact.
I’ll go over the first three artifacts (enhancement, shadowing, and refraction) in this post and leave the next four for another post.
Refraction artifact occurs when sound waves are deflected by a round smooth structure like the gallbladder or bladder:
Shadowing artifact is where the ultrasound beam is completeley blocked, for example by bone:
Enhancement is the opposite of shadowing. When the beam goes through a fluid filled structure little energy is absorbed and so the area beyond the fluid is brighter than usual. This unusual brightness can hide important information so be ready to turn down the gain.
You need to use a lot of gel to get good pictures – a lot!
Three final facts:
B mode scans [black and white (gray scale) scans are all you need for basic scans.
Low frequency probes penetrate deeper into the body but have lower resolution than high frequency probes.
High frequency probes penetrate less deeply into the body but have higher resolution than low frequency probes.
Point-Of-Care Ultrasound for Emergency Physicians — “The EDE Book”; “The clearest and most concise approach to emergency ultrasound.”
There is also an e-book of the above available but unfortunately it is only available on Apple devices. It is not available for Android or Windows users.