Scintigraphy is an imaging technique that involves tracking the distribution, in a patient's body, of very low doses of radioactive elements.

Each element is chosen according to its affinity for the organ under study.

In addition to the progression of the radioactive elements through the human body, their fixation in the interior of certain tissues is detected.

Because they are radioactive, these elements  disintegrate, releasing a gamma photon. This radiation is detected by one or more gamma detecting cameras.

This technique permits a highly targeted exploration of certain organs or pathological processes.

Scintigraphy is a method that produces images of the functioning of organs, as opposed to merely anatomical images (as in X-rays), which show only the contours and the densities of organs.

The examination is painless, and has no side effects.

Radiography  is based on the use of x rays.

These rays were discovered in the 19^th century . They are electromagnetic waves, just like the microwaves used in portable telephones, or the light that we perceive with our eyes.

The apparatus is made up of an x ray tube (an emitter of x rays) , an examination table and a receptacle that contains the radiographic film.

For a chest x ray, the patient stands upright with his or her chest pressed against the examination table, which is in a vertical position.

The x ray tube is placed to the rear of the patient.

One asks the patient to inhale so as to fill his/her lungs, then  submits him/her to x rays so as to make a record on the radiographic film.

The film cassette is then removed and the film is developed in the same way that traditional photographic film is developed.  Current technology tends to replace radiographic film with digital recording plates.

Contrary to popular opinion, radiation is a natural phenomenon. It was discovered in 1896 by A.H. Becquerel who was studying the fluorescent properties of uranium salts.

We identify 3 distinct types of radioactive decay. Each type of decay liberates a large amount of energy:

1. Alpha radiation: the emission of a helium atom.
2. Beta (+ and -) radiation: the emission of either an electron (beta-) or a positron (beta+).
3. Gamma emission: the liberation of a high-energy photon.

Wave-particle duality is a central idea of modern physics. We now know that light exhibits properties of both waves and particles. Wave theory is the only way to explain interference patterns and diffraction of light but it failed to predict the photoelectric effect discovered in the early 20th century. This was the time when Einstein and Planck introduced the idea of Quanta of light, or Photons. The wave and particle properties of light are inseparable and complementary. One speaks of wave-particle duality, which idea marked the beginning of Quantum mechanics.

ITER (International Thermonuclear Experimental Reactor) is an experimental nuclear fusion project aimed at providing almost unlimited renewable energy. It involves subjecting heavy hydrogen atoms to extreme temperatures and pressure in a confined medium in order to cause fusion of the atoms, thereby reproducing what happens in the stars. The excess energy released during this process can be used to produce electrical power.

The kinetic molecular theory of Maxwell and Boltzmann proposes that the macroscopic properties of an ideal  gas  derive  from the fact that it is  composed of a large number of colliding point particles that  are  in rapid motion.  The particles do not interact with one another except in elastic collisions. The piston receives from each such collision a certain amount of momentum. The macroscopic effect of these collisions is pressure.

The half-life of  a given isotope is the amount of time it takes for half of the atoms in a sample to decay. This animation  allows you to address, using three different isotopes,  notions like radioactive decay, carbon dating, half life constant…

When a heavy nucleus (Uranium, for example) fissions, it splits into two smaller nuclei. Two or three  neutrons are also emitted. The sum of the masses of these fragments is less than the original mass. This 'missing' mass has been converted into a large amount of energy according to Einstein's equation,  E=mc².  When the fissionable material is confined, the emitted neutrons bombard and split other nuclei, provoking a chain reaction, either controlled (as in a nuclear reactor) or uncontrolled (as in an atomic bomb).