Clinical ultrasound is revolutionizing revolutionizing medical practiceproviding healthcare professionals with an invaluable tool for improving patient care. This fast, non-invasive imaging technique enhances the physical examination. Learn the basics of ultrasonography, basic gestures and the essentials of interpretation by comparing the clinical picture with the images.
There are many advantages to taking up clinical ultrasound. First and foremost, this skill improves the quality and speed of diagnosis, by providing complementary information to the physical examination. What's more, clinical ultrasound can be performed quickly and at the patient's bedside, saving you time and optimizing patient care. Last but not least, this non-invasive, patient-safe technique can be repeated as often as required, enabling personalized, tailored follow-up.
However, it is important not to confuse clinical ultrasound with specialty ultrasound. While the latter is generally carried out by radiologists, clinical ultrasound can be performed by healthcare professionals from different specialties(general practitioners, emergency physicians, specialists, midwives, nurses, etc.) directly at the patient's bedside, by a caregiver steeped in the overall clinical context. The aim of clinical ultrasound is to complement the clinical examination by visualizing the internal organs, and to answer one or more clear diagnostic questions, usually in binary form (presence or absence), in order to facilitate more appropriate and precise decision-making regarding the patient's management.
It is important to emphasize that the detection of a specific sign can considerably enrich the syndromic summary and refine the diagnostic orientation. On the other hand, the absence of such a sign, or its non-detection by the practitioner, can often necessitate the use of complementary imaging explorations to obtain a precise diagnosis.
Training in clinical ultrasound requires a certain investment of time and energy. The learning path generally comprises several stages, from theoretical training to supervised practice, via the acquisition of technical and image interpretation skills. Once you've been trained in clinical ultrasound, the medium- and long-term benefits are numerous. You'll be able to improve your day-to-day practice, by being able to make faster, more accurate referral diagnoses. What's more, clinical ultrasound will enable you to strengthen collaboration with the various players in your network, facilitating information sharing and care coordination.
The basics of clinical ultrasound
To get off to a good start with clinical ultrasound, you'll first need to understand the fundamentals of ultrasound imaging. This article will introduce you to the fundamentals of ultrasound imaging, how to use an ultrasound scanner and how to understand an ultrasound image.
The skills you will have acquired after finishing this article:
- Understand the basic operation of an ultrasound imaging probe;
- Understand the behavior of ultrasonic waves on tissues and structures with different compositions;
- Understand the importance of patient positioning and active participation in the examination;
- Learn to situate yourself in relation to the image transmitted by the probe on the screen;
- Finding your way around basic controls ;
- Select the correct transducer frequency ;
- Practice and master the gesture and movements involved in handling the probe;
- Maintain and disinfect your probe at the beginning and end of the examination.
Understanding ultrasound theory
An ultrasound scanner, whether on a cart or ultraportable , is a relatively simple machine, consisting of a probe that embeds a transducer that generates and receives ultrasound waves, a computer, phone or tablet that processes the signals, and a screen that shows the images generated in real time.
The part of the probe that comes into contact with the patient's skin is called the probe nose. All probes have an indicator to help the user locate and distinguish between the left and right sides of the probe. Techniques for scanning the probe to locate and obtain clear images will be covered later in this article.
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The ultrasound scanner emits ultrasound, sound waves in a frequency range too high to be detected by the human ear. The mechanical sound waves generated by the ultrasound transducer propagate through the tissue, creating a local, ephemeral and non-irradiating mechanical disturbance thanks to the acoustic impedance of the tissue. Impedance is the property of tissues that represents their resistance to the propagation of sound probes.
How different tissues respond to sound waves
Low impedance (very dark gray or black)
Structures with low acoustic impedance allow sound probes to pass through completely → they thus generate a very dark or anechoic image.
Examples: various fluids, blood, urine...
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High impedance (gray)
Structures with high acoustic impedance partially reflect sound waves → they thus generate a gray image.
Examples: solid organ, liver, spleen
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Very high impedance (white)
Structures with very high acoustic impedance reflect sound waves completely → they thus generate a white image. Structures such as bones do not allow sound waves to pass through, so they reflect anechoic (very dark) shadows.
Examples: pleura, bone, metal implants, diaphragm...
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Gas (cloudy gray, artifact image)
The gases spread the sound waves, producing a cloudy greyish image.
Example: lung
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Understanding the choice of frequency in relation to the organ
Different sound frequencies produce images at different depths. So, depending on the organ or tissue depth you're looking at, you need to set your probe to the right frequency. On a trolley-mounted ultrasound scanner, you need to choose the right probe for the job, whereas on a portable or ultraportable ultrasound scanner, all frequencies are present on a single probe nose (as is the case withechOpen O1) or on two probe noses (convex and linear).
To determine which frequency to use, remember this basic rule of ultrasound:
- The more superficial the structures, the higher the frequency.
- Example: superficial blood vessels → 7.5 MHz to 10 MHz
- The deeper the structures, the lower the frequency.
- Example: liver → 3.5 MHz
The convex probe, also known as the abdominal probe, is the most versatile probe, enabling visualization of most of the (numerous) structures in the abdomen, often deep ones. Its frequency, which is often between 2 and 5 MHz, and its wide field of view, enable multiple organs to be captured in a single image, and the presence of effusions to be noted. However, it can be difficult to handle if you have to look through intercostal windows.
The phased array probe, sometimes called the cardiac probe, is designed for echocardiography, among other applications. With frequencies varying between 1 and 5 MHz, it enables the heart to be viewed more easily through intercostal windows.
The linear probe offers a higher frequency (from 7.5 MHz), and can be used to view surface structures such as vessels or superficial pleura. Its linear nose makes it easy to view the pleura through intercostal windows. Given its frequency range, it cannot be used to view deep organs.
For their part, ultraportable ultrasound scanners integrate a range of frequencies in a single probe nose, making them suitable for most applications. echOpen The O1, for example, features 3 frequencies: 3.5, 5 and 7.5 MHz. Versatile, the shape of the ultraportable probe nose is also suitable for exploring different parts of the human body.
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Find your bearings in relation to the image
One of the aspects you'll need to master is understanding the orientation of the image on the screen - although this is not necessarily intuitive if you're a beginner.
Start by locating your probe's indicator:
- In cross-section, the probe marker should point to the patient's right (because the patient is lying in the anatomical reference position, and is viewed from below, as in a CT scan).
- In both longitudinal and coronal sections, the marker should point towards the patient's head.
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For your first cuts, we recommend that you go through the orientation exercise again and again until it becomes intuitive.
The image below shows an example of an ultrasound scan of the patient's right kidney. The probe is placed on the patient's skin in a longitudinal position, with the indicator pointing towards the patient's head.
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- The top of the cone corresponds to the surface on which the probe is placed (patient's skin);
- The bottom of the cone shows the deeper structures. If you have placed the probe on your patient's abdomen (as in the example below), at the bottom of the cone you will see the structures closer to his spine;
- On the right side of your cone you will see the structures closest to your patient's lower body;
- On the left side of your cone you will see the structures closest to your patient's head.
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Mastering the gesture
Depending on the case, you can make different gestures to move the probe and obtain a clear, centered image of what you wish to observe. You can also apply pressure against your patient's skin to check the compressibility of a vessel, or to clear pockets of gas obstructing the view of an organ.
Before the gesture becomes intuitive, we advise you to practice on yourself on several body dials. As you do so, you'll notice that the ultrasound gel wears off quickly: it's important to apply it often to get a clear image.
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Using your ultrasound software
Whether you're training on a conventional, portable or ultraportable ultrasound scanner, you need to get used to using the different buttons, options and controls or knobs on your machine. They will be slightly different on each ultrasound machine, and the more advanced ones may feature a variety of options.
To get started, however, you just need to understand the basic controls:
- Frequency (or depth) adjustment according to organ or body part.
- Adjust gain (or image brightness).
- A poorly calibrated image will be too bright or too dark, and you could miss out on important details.
- Capture images or video loops.
- This function lets you save slices of interest. On some classic ultrasound scanners, you can also print them out. On more recent ultrasound scanners, as well as on most ultraportables, you can save your images in a dedicated gallery, where you can also insert notes or create a patient file.
Disinfecting your ultrasound machine
Once the examination has been completed, you should clean and disinfect your probe according to the manufacturer's instructions. In most cases, the recommendation is to wipe the probe with absorbent paper. Then disinfect the device with a disinfectant wipe.
The next steps in your initiation
You now have the basic theoretical knowledge you need to perform your very first test ultrasound scans!
The next stage of your training will involve interpreting and annotating images and loops, both physiological and pathological. This step will enable you to develop your expertise, refine your clinical judgment and your understanding of anatomy. Once you've acquired the basics, we'll invite you to perform ultrasound scans on yourself. After an average of thirty sections per organ, you will have sufficiently mastered probe positioning and the gesture that will enable you to acquire quality images.
After this self-study phase, you will start performing ultrasound scans on your patients in test mode, for a recommended period of several weeks. This stage will enable you to put your new skills into practice in a real-life context, while benefiting from guidance and constructive feedback from your peers and trainers.
Finally, you will fully integrate clinical ultrasound into your daily medical practice. This new skill will enable you to make faster, more accurate diagnoses, optimize patient care and strengthen collaboration with your colleagues. In short, training in clinical ultrasonography is a lasting and beneficial investment in your professional career and the health of your patients. Don't hesitate to embark on this promising and exciting path!
