Camera used to image positron-emitting radionuclides in patients.

Radiography is a synonym for the examination of the structure of materials by nondestructive methods, for example with radiation. Radiography is used for both medical and industrial applications.
Autoradiography describes the imaging of an object using radiations produced by the radioactive decay of nuclides in the object.
Sometimes, imaging modalities without use of radiation such as MRI and ultrasound are grouped in radiography due to the fact that the radiology staff handles different forms of medical imaging. Treatment using radiation is known as radiotherapy.

See also Diagnostic Imaging and Conventional Radiography.

Thorium (232Th) is a naturally radioactive element. Thorium is the parent nuclide of one radioactive series, and specific thorium nuclides are decay products of three radionuclide series.

See also Thorotrast.

[Whole Body Radiation Counter] Very sensitive device intended to measure even the smallest amount of radionuclides in the entire body. Range usually from Bq to kBq. Heavy shielding is used to keep out naturally existing background radiation.

X-rays are a part of the electromagnetic spectrum. X-rays and gamma rays are differentiated on the origin of the radiation, not on the wavelength, frequency, or the energy. X-rays are emitted by electrons outside the nucleus, while gamma rays are emitted by the nucleus. X-rays have wavelengths in the range of about 1 nanometer (nm) to 10 picometer (pm), frequencies in the range of 10^-16 to 10^-20 Hertz (Hz) and photon energies between 0.12 and 120 kilo electron Volt (keV). The energy of rays increase with decreased wavelengths. X-rays with energies between 10 keV and a few hundred keV are considered hard X-rays. The cutoff between soft or hard X-rays is around a wavelength of 100 pm.
Because of their short wavelength, X-rays interact little with matter and pass through a wide range of materials. These interactions occur as absorption or scattering;; primary are the photoelectric effect, Compton scattering and, for ultrahigh photon energies of above 1.022 mega electron Volt (MeV), pair production.
X-rays are produced when high energy electrons struck a metal target. The kinetic energy of the electrons is transformed into electromagnetic energy when the electrons are abruptly decelerated (also called bremsstrahlung radiation, or braking radiation) similar to the deceleration of the circulating electron beam in a synchrotron particle accelerator. Another type of rays is produced by the inner, more tightly bound electrons in atoms;; frequently occurring in decay of radionuclides (characteristic radiation, gamma ray, beta ray). The energy of an X-ray is equivalent to the difference in energy of the initial and final atomic state minus the binding energy of the electron.
Wilhelm Conrad Roentgen discovered this type of rays (also called Roentgen-rays) in 1895 and realized that X-rays penetrate soft tissue but are absorbed by bones, which provides the possibility to image anatomic structures; the first type of diagnostic imaging was established. Radiographic images are based on this difference in attenuation for tissue and organs of different density. Today ionizing radiation is widely used in medicine in the field of radiology.

See also Exposure Factors, X-Ray Tube, and X-Ray Spectrum.