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Discovery of x-ray and modern radiology

Updated on February 24, 2015

Discovery of x-ray

As for many of the most important and successful inventions made throughout the history, even x-ray have been discovered by accident: in November 1895, prof. Wihelm Roentgen was studying the phenomenons related to the transit of electricity at an extremely low pressure. He was working inside a darkroom, as those used by photographers; he had carefully wrapped a discharge tube inside a thick sheet of black cardboard to prevent the light hitting into it when a sheet of paper, placed randomly on a nearby table and covered by a phosphorescent substance, suddenly became fluorescent.

According to Roentgen’s first explanation, the phenomenon was due to the emission coming from the discharge tube of invisible rays, which seemed to cause the above mentioned fluorescence. After taking other objects and placing them between the optical path emitted by the rays and a photographic plate, the physician noted that a picture of those objects remained engraved on the plate: that was the exact image of the objects and their internal structure. Roentgen called them "x-rays", right because at that time they were considered mysterious objects and everyone was unaware of their existence.

A particularly curious fact related to the discovery of x-rays is that prof. Roentgen was colour-blind, and this issue had its important contribution. In 1901, prof. Roentgen, thanks to his incredible, even if fortunate, invention would be prized with the most important award for scientists: the Nobel prize for Physics.

During the same period, in Italy, prof. Augusto Righi was doing his first radiography at University of Bologna using the so called "Roentgen’s rays". As test subject for this experiment, he relied upon his mechanic.

Modern radiology

Nowadays, x-ray are well known mainly because of their use within the medical field as a method of investigation, and through radiographs have enabled science to see literally through the human body. Before their discovery, fractures and internal injuries were diagnosed and dealt only with the intervention of the scalpel.

X rays are electromagnetic waves at high frequency able to carry large amounts of energy. When a stack of x-rays is sent on a body, a part of these is absorbed and the other half is transmitted. The latter can be detected by a photographic film, providing information on the internal structure of the body. If used at a low intensity level, they are a powerful tool investigation for medical diagnosis. The x-ray is the caption of a part of a human body able to disclose the changes induced by a body on the x-ray stack that it has passed through.

X-rays provide two dimensional images of a part of a human body. The combination of a computer with a x-ray machine allows the formation
of three-dimensional image called CAT (computed axial tomography).
When doing a CAT scan, the x-ray tube emits a thin beam of rays passing through the patient's body and arriving on the detector measuring the transmitted intensity. The measurement is repeated many times while the source and the x-ray detector move together along the axis of the body.
Soon after, the whole device performs a small rotation and the scanning procedure starts over again.

The scanning is repeated until the unit has been rotated to 180 °. The whole set of collected data is processed from the computer, reconstructing the part of the body examined by the x-rays. The scan can be speeded up using many detectors arranged on a circle, and it remains fixed while the x-rays source moves around.

X-ray machines

Usually, a x-ray machine is made by: a x-ray tube, a lead shielding, an x-ray collimator, and a photographic plate. The x-ray tube is like a giant lamp that uses electricity at high voltage to generate x-rays. The lead shielding is used for directing the x-rays towards a specific part of the body, while preventing them from escaping in all directions . The collimator works to channel and redirect photons of differing levels of energy, and are often used to assist with the magnification or minimization of images. The photographic plate captures the image of x-rays as they pass through the body. In the past, the photographic plate used the same film of traditional cameras. Nowadays, in most x-ray machines, it is connected directly to a computer, to allow the capture of a digital image.

But the use of x-rays is not only limited to medical purposes: airports do have x-ray based devices as well, as people used to travel by plane already know; these machines can make an accurate scanning of luggages, objects and, in general, of all those things that have to be boarded on a plane together with the passengers. In the last years, a couple of international airports have adopted specific devices, the so-called "Full Body Scanners", able to detect objects on a person’s body. This kind of technology can help to target and recognize potentially dangerous objects, substances or drugs held by passengers in transit.


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