Dr. mokhleed zaza
Medical applications of x-ray
X-radiation (composed of X-rays) is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3×1016 Hz to 3×1019 Hz) X-rays up to about 10 keV (10 to 0.10 nm wavelength) are classified as "soft" X-rays, and from about 10 to 120 keV (0.10 to 0.01 nm wavelength) as "hard" X-rays, due to their penetrating abilities. Hard X-rays can penetrate some solids and liquids, and all uncompressed gases, and their most common use is to image of the inside of objects in diagnostic radiography and crystallography. As a result, the term X-ray is metonymically used to refer to a radiographic image produced using this method, in addition to the method itself. By contrast, soft X-rays hardly penetrate matter at all; the attenuation length of 600 eV (~2 nm) X-rays in water is less than 1 micrometer. The distinction between X-rays and gamma rays has changed in recent decades. Originally, the electromagnetic radiation emitted by X-ray tubes had a longer wavelength than the radiation emitted by radioactive nuclei (gamma rays). Older literature distinguished between X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10−11 m, defined as gamma rays. However, as shorter wavelength continuous spectrum "X-ray" sources such as linear accelerators and longer wavelength "gamma ray" emitters were discovered, the wavelength bands largely overlapped. The two types of radiation are now usually distinguished by their origin: X-rays are emitted by electrons outside the nucleus, while gamma rays are emitted by the nucleus.
During the first four decades of this century many advances in medical radiation uses came from gradual improvements in equipment and techniques. The availability of X-ray machines in military hospitals during World War I convinced many physicians of the usefulness of X-ray studies in detection of somatic problems, as well as trauma. A chest X ray became the standard method of diagnosing tuberculosis. About all that could be offered the active tubercular patient was nursing care but isolation of such patients helped to break the spread of the highly contagious disease to other family members and co-workers. Tuberculosis was the target of the ﬁrst X-ray population screening efforts The creation of artiﬁcial isotopes in the 1930s by Frédéric Joliot and Irene Curie, daughter of Pierre and Marie ,opened new dimensions in radiation science. Soon, Ernest Lawrence was making artiﬁcial isotopes in the cyclotron of the Donner Laboratory at the University of California in Berkeley. Lawrence invited Robert Stone, the chief of radiologyat the University of California Medical Center in San Francisco, to bring cancer patients for treatment with neutrons produced in the Donner lab. Cancers treated with neutrons melted away. Soon, so did the cancer patients. Neutrons had more energy and different biological characteristics than high energy X rays. Stone discontinued his treatments until the characteristics of neutrons could be understood better World War II arrived, and in quick succession Lawrence, Stone, and most of the leading radiation scientists in the free world were drawn into the Manhattan project to develop an atomic bomb. Wartime imperatives drive science more strongly than peaceful objectives. But there was an appreciation within the Manhattan project that biological problems were created by the physical and chemical advances, and after the war, the congress created the Atomic Energy Commission to further peaceful applications of the new radiation science. FOR PHYSICIANS, these peaceful applications took two directions. One was the development of artiﬁcial reactor-produced isotopes as high energy sources for radiation...