Ultrasound is a non-invasive technique that makes it possible to ascertain (diagnose) some diseases through the use of high-frequency sound waves (ultrasounds) that allow you to generate and visualize the image of internal organs and tissues.
Ultrasound can be used for:
- follow (monitor) the progress of a pregnancy
- ascertain (diagnose) a disease
- guide a surgeon during some operations
During the ultrasound, a small device, called an ultrasound probe, emits ultrasounds that bounce between the different organs and tissues of the body, creating "echoes" collected and transformed into a "moving image displayed, in real time, on a monitor.
Most ultrasound scans last between 15 and 45 minutes. Usually, they take place in a radiology department or in public or private clinics (ASL, hospitals, clinics, multi-specialty centers) and are performed by a radiologist or an ultrasound doctor. They can also be performed by other health professionals, such as midwives or physiotherapists, who are specially trained.
Depending on the reason and the organ for which it is required, the ultrasound can be:
- external, the probe moves to the skin
- internal, the probe is inserted into the body
- endoscopic, the probe is connected to a long thin and flexible tube (the endoscope) which is inserted into the body
The ultrasound assessment (diagnosis) can also be divided into:
- anatomicalproduces images of internal organs or other body structures
- functional, combines anatomical images with information such as blood movement and velocity, tissue texture, and other physical characteristics to create "information maps." The maps help the physician identify any changes or differences in functioning within an organ or tissue of the body
Preparation for ultrasound
Before proceeding with some types of ultrasound, it is required to undergo some preparation to help improve the quality of the images produced:
- drink water and do not urinate until the end of the exam, in the case of a "pelvic ultrasound."
- keep fasting in the hours preceding an abdominal ultrasound
One of the most common uses of ultrasound is in pregnancy to monitor the growth and development of the fetus. Other uses include: imaging of the heart, blood vessels, eyes, thyroid, brain, breast, abdominal organs, skin, and muscles. The images are displayed in two dimensions (2D), 3D or 4D (i.e. a 3D with movement, for example of blood flow).
Depending on the type of organ to be checked, and why it is required, ultrasound can be external, internal, endoscopic or functional:
External ultrasound is often used to examine the heart, liver, kidneys, and other organs in the abdomen and pelvis, as well as muscles and joints. It is also used to follow the evolution of a pregnancy and provide important information on the shape and structure of the unborn child (morphological).
The sonographer, after spreading a special gel on the ultrasound probe, positions it on the skin by moving it along the part corresponding to the organ to be examined. The lubricating gel allows the probe to move smoothly and ensures continuous contact with the skin.
For ultrasound of the uterus and pelvic area, you will need to drink water to have a full bladder during the exam. Once completed, you can empty your bladder.
Internal ultrasound (transvaginal or transrectal) allows you to take a closer look at internal organs such as the prostate, ovaries or uterus.
During the exam, you are asked to lie on your back, or side, with your knees towards your chest.
A sterile condom will be placed on the ultrasound probe which will then be gently inserted into the vagina or rectum. The images will be displayed on a monitor.
Internal exams can cause some discomfort, but not pain.
The endoscope is inserted into the body through the mouth to examine the stomach and esophagus. It has a light and a probe on its extremity and, once inserted into the body, it emits the same ultrasounds used by the external probe to create the images.
At the beginning of the examination the person undergoing it is asked to lie down on his side, to facilitate the insertion of the endoscope directed towards the stomach. To avoid possible discomfort, a sedative and local anesthetic may be administered down the throat before proceeding. A mouthguard could also be used to keep the mouth open and to protect the endoscope from biting teeth.
After an endoscopic ultrasound with sedation, it is advisable to wait until the effect of the drug has significantly diminished before leaving the place where the examination took place. It is also advisable to be accompanied as it is not recommended to drive.
Functional ultrasound includes the doppler and the color doppler ultrasound to measure and visualize blood flow in the vessels and heart.
Color Doppler is used to measure the speed and direction of blood flow and is commonly used to check for fat and cholesterol deposits (atherosclerotic plaque), which could block blood flow to the brain, inside the carotid arteries. .
An "other functional form of ultrasound is the"elastography, a method for assessing relative tissue stiffness: it can be used to differentiate tumor tissue from healthy tissue. Elastography can also be used to test for liver fibrosis, a disease in which excess scar tissue accumulates in the liver due to inflammation.
In March 2020, a study was published on electromechanical wave imaging (EWI), a high frame rate ultrasound technique capable of mapping the electromechanical wave corresponding to the propagation of the onset of contraction in response to the electrical activation of the heart. . It is a non-invasive ultrasound-based imaging modality for locating cardiac arrhythmias such as Wolff-Parkinson-White (WPW), premature ventricular complexes (PVCs), atrial tachycardia (AT), and atrial flutter (AFL).
This ultrasound imaging technique can generate a mapping of the heart that can help identify the site of the heart causing an irregular heartbeat (cardiac arrhythmia). Adding this imaging method to traditional methods of clinical investigation could help improve decision making and treatment planning.
The results of the ultrasound can be obtained immediately after the conclusion of the investigation but, in most cases, it will be necessary to wait until the images are printed and evaluated and the sonographer's report is transcribed. The results must be brought to the attending physician for the prescription of any further information.
The ultrasound examination is generally considered safe, has no contraindications, does not involve exposure to radiation (as is the case, however, in the case of Computed Tomography, CT) and does not produce ionizing radiation such as those produced by x-rays.
External and internal ultrasound scans are usually painless.
Before undergoing an internal ultrasound, the sonographer should be informed of a possible allergy to latex to avoid covering the probe with this material.
On the other hand, endoscopic ultrasound can cause temporary undesirable effects (side effects), such as sore throat or swelling. Finally, there is a remote risk of more serious complications such as internal bleeding.
NHS Choices. Ultrasound-scan (English)
National Institute of Biomedical Imaging and Bioengineering (NIH). Ultrasound (English)