Imaging techniques: exploring the body with advanced technologies

It is based on the ability of tissues to absorb X-rays in different ways depending on their atomic composition, density and thickness. During the examination, the patient is exposed to short pulses of radiation:

● some tissues, such as bones, attenuate the X-ray beam more, and are represented by brighter (whiter) gray tones on the X-ray image;

● other tissues, such as the lungs or adipose tissue, appear dark on the final image because they attenuate the X-ray beam less;

● tissues with intermediate attenuation, such as internal organs (heart, liver, spleen), are represented on the image with intermediate gray values.
This contrast helps detect anatomical changes, fractures, injuries, or other abnormalities.

It uses high-frequency sound waves to visualize organs, soft tissues and blood flows. A conductive gel is applied to the patient's skin and an ultrasound probe is passed over the area to be examined. Depending on its density and elastic properties, each tissue absorbs or reflects some of the ultrasound: the reflected waves are collected by the probe and translated into images by the computer.

It combines the information from the attenuation of a series of X-rays, coming from different angles, in order to create detailed images in the form of cross-sections of the body (tomographic images). As the table slides very precisely inside a tunnel, an X-ray emitter rotates around the patient. A sensor, placed on the opposite side to the source, captures the energy of the X-rays that pass through the body and deciphers the exact attenuating power of each point of the body. This attenuating power is translated into very thin (even sub-millimeter-thick) and very detailed tomographic sections, which combined together can provide a perfect three-dimensional representation of the anatomical structures studied.

It involves the injection of a small amount of radioactive substance to visualize the metabolic activity of the tissues. This tracer, which is usually linked to a molecule very similar to glucose (sugar), is distributed in cells according to their specific metabolic activities, such as sugar consumption, illuminating them. In a process called "decay", the radioactive substance emits positrons (particles of antimatter) that interact with the electrons present in the body tissues, producing gamma rays. A ring of sensors surrounding the patient captures the emitted gamma rays and translates them into images.

It uses a magnetic field to produce detailed tissue images. The patient is subjected to a very strong magnetic field (up to approximately 50,000 times the Earth's!). Under these conditions, the hydrogen protons of the water molecules present in all body tissues behave like spinning tops that rotate and align in the direction of the magnetic field. Using radio waves, small "pushes" are applied to the protons, which will try to return to their original position by emitting tissue-specific radio signals. An antenna intercepts these signals and converts them into a highly detailed digital image.