The different medical imaging techniques

In your lifetime, you have probably hurt yourself to the point of going a little deeper into what's going on in your body. For this, different techniques are made available to the doctor: radio, scanner, and MRI. But what do these barbaric names, yet so familiar? Read the rest of this article to learn more about the most commonly used imaging techniques!

Medical imaging: radiography

Whether following a fall to verify that there was no fracture, to observe the lungs to detect a possible pulmonary or cardiac problem, or even to the dentist to identify cavities, radiography by X-ray is the best known and most widely used imaging technique.

Working principle

Without going into great scientific explanations, just know that the X-ray machine produces and sends a certain number of electrons at a certain speed so that they can pass through the different materials of the body. Bypassing through these different layers, some will absorb this radiation more than others because of their composition: the bones will very well stop the electrons, while the water or the air will let them cross until a plate which will fix these “shadows.”

To get a good overview, always take two images perpendicular to each other.

Goal

Bones are the preferred study structures for conventional radiography.

Due to radios, one can detect fractures, bone cracks, displacements, but also check the vertebral curvatures, the number of ribs present, control the progression of arthritis anywhere on the skeleton, or the good behavior of '' medical or osteosynthesis equipment.

The lungs and heart can also be studied at the surface, for example, to see if there is no water in the lungs or to check that the heart is of a non-pathological size.

The mammography is a particular use of X rays, to mark structure abnormality of the breasts.

Advantages, disadvantages, and contraindications

The advantage of radio is that it is very fast, inexpensive, and easily accessible. You can also take pictures in motion, that is to say, in "dynamic," for example, the knees bent, in forced inspiration.

Its disadvantages are, paradoxically, that it is often used, which entails a risk of irradiation because of prolonged exposure. In addition, there are many structures that you cannot see, such as soft tissue (muscles, tendons, ligaments).

The main contraindication concerns pregnant women as a precaution for the fetus to not injure it or cause permanent damage.

Medical imaging: the scanner

There, it gets complicated. What machine is the scanner already, the one that makes a lot of noise or the other? And, what is arthrography?

Working principle

Well, actually, the scanner is the machine with a ring. In general, it is the ring that moves, but the table on which you are lying can also move. Also called computed tomography, this technique uses fine X-rays that will virtually cut the body into small cubes, the average density of each of which will be defined. This density will allow us to tell if, in this virtual cube, it is fat, water, air, or another element that takes precedence. Concretely, on the image, it will be represented by different shades of gray centered with respect to a chosen element, what is called windowing.

This technique is 100 times more precise than conventional radiography. As the treatment is done by computer (CT scanner means computed tomodensitometry scanner), we can go back on any image, make any cut in the body to observe an organ from every angle, and even make three-dimensional reconstructions. However, the acquisition is made by the plan. As for CT arthrography, it is more specifically to see what is happening in the joints due to a contrast product, under radiographic guidance (hence its other name of arthrography).

Goal

Due to this technique, soft tissues can be studied much better. The bones are not left abandoned, we can also see fractures or osteoarthritis, but the scanner is not the examination of choice for these problems. Rather, it will be prescribed to identify internal lesions, monitor or detect cancers or tumors, or see any change in the volume or structure of a given organ.

The CT arthrography will allow you to see the entire interior of a joint, that is, to say the cartilage, ligaments, but also the joint bursa, synovial fluid, and, for the knees, the meniscus.

Advantages, disadvantages, and contraindications

The scanner, which is also quite fast, allows a view from an organ's angles in a single take and a posteriori work.

The disadvantages and contraindications are the same as for conventional radiography. However, we can add to it the fact of being overweight, compared to the size of the ring, which produces the X-rays because the person would risk not passing through.

For the CT scan, the different contrast media used can be sources of generalized allergic reactions (use of iodine).

Medical imaging: ultrasound

There, you are probably telling yourself that you know this machine because it is the one you use when you are pregnant! We will tell you that you are absolutely right, but not only. The more athletic among you, in particular, know very well what we are talking about.

Working principle

Here, ultrasound will be used. Produced by a probe which is also capable of receiving them, the ultrasounds will propagate until they encounter an obstacle. Depending on the nature of this obstacle (fat, ligament, water, etc.), the ultrasonic wave will be more or less absorbed and more or less reflected. This is how the examiner will be able, on the spot, to take stock and determine the nature of these obstacles, whether they really should be there or not, whether they are intact, etc.

In the case of perinatal ultrasound, the medical imaging technician will seek to observe the fetus's evolution and placenta.

Goal

Ultrasound is the examination of choice for shallow soft tissue, such as muscles, tendons, and ligaments. In the echo-doppler case, a thin probe can be introduced into the lumen of the blood vessels to observe the flow, see if it is blocked or not, and diagnose venous or arterial pathologies.

Advantages, disadvantages, and contraindications

This technique is the fastest of all, probably the cheapest; it does not require the injection of contrast product and is in no way harmful. Its big drawback is the fact that it is examiner-dependent, that is to say, that the interpretation of the images can vary somewhat from one person to another, while remaining within the acceptable limits, otherwise this examination would have been abandoned for a long time. Rest assured, we can always predict in advance the gender of your future baby! Unfortunately, sometimes, errors can occur precisely.

Another drawback of ultrasound is that it does not allow the study of organs located deep or behind the bones (spinal cord, lungs). There is no contraindication.

Medical imaging: MRI

So here's the last technique, you guessed it if you've ever had to go through one: Magnetic Resonance Imaging (MRI for close friends) is the big, narrow machine inside that makes a lot of noise.

Working principle

So there, it gets complicated level explanations. A little physics reminder: any electric current drives a magnetic field, and conversely, any magnetic field drives an electric current. To make it very simple, this machine is a giant magnet that will, due to radiofrequency waves, vary the atoms of our body and observe the resulting mini-currents. To put it another way, we have to make the electrons that make up our body resonate and then observe their return to balance. Still, without going into details, there are two image acquisition modes called T1 and T2. The examiner must know which mode is used in order to interpret the images correctly. Like the scanner, there are two types of examination: the so-called anatomical MRI, where we base ourselves on the magnetization of the hydrogen protons present in the water and the fat of the body and the functional MRI where we are based on the presence of hemoglobin (constituting red blood cells) not carrying oxygen.

Goal

Anatomical MRI allows an in-depth study of soft tissues (because they are all made up of different proportions of water). While functional MRI allows the vascular study of certain organs and, in particular, of the brain to detect, for example, stroke and make the diagnosis, Alzheimer's disease or multiple sclerosis.

Advantages, disadvantages, and contraindications

This examination is very practical for carrying out a study of several parameters at the same time (volume, constitution) in the three planes of space, without harmful radiation.

However, the drawbacks are numerous. First of all, we can cite the discomfort of the patient who performs the examination. It is held in a very narrow tube, for an often long duration (about 40 minutes) while having to record not to move, all this in a very loud noise (fortunately attenuated by headphones).

Then, as it is a giant magnet, the contraindications mainly concern: people with a pace-maker or any other stimulating implant that the machine could adjust those with old osteosynthesis equipment or prostheses (hip, valve, etc.) which are magnetic and those with a metallic foreign body in the eye (beware of apprentice handymen). In general, the pregnant woman will avoid taking this kind of examination. The last contraindication is for people allergic to contrast agents that can be used or severe chronic insufficiency. To put an end to the drawbacks, the cost of such an examination is very high, and it is generally necessary to wait a certain time, depending on the region, to have access to a machine and therefore to an appointment.

In general, it is your attending physician or a specialist that you consult who will prescribe an examination in one of these machines, and if you have the slightest doubt as to your state of health to carry it out, it should be spoken to, all as the examiner at the moment, who is supposed to remind you of the safety instructions and the contraindications of the various exams. Here is the end of this article on the different medical imaging techniques. Did you learn anything? Which method have you already tried? Did it go well? Tell us everything in a comment!

Author: Vicki Lezama