dynamic susceptibility contrast (DSC) MR perfusion.metal artifact reduction sequence (MARS).turbo inversion recovery magnitude (TIRM).fluid attenuation inversion recovery (FLAIR).diffusion tensor imaging and fiber tractography.MRI pulse sequences ( basics | abbreviations | parameters).iodinated contrast-induced thyrotoxicosis.iodinated contrast media adverse reactions.clinical applications of dual-energy CT.as low as reasonably achievable (ALARA).If the wavelength of light emitted by the screen is not in the sensitive range of the film, it will not be absorbed by the film. Orthochromatic films: sensitive to ultraviolet, blue and green lights It is important to note that the color of the light emitted (wavelength) must match the light sensitivity of the film used. This is known as spectral matching:Ĭonventional films: sensitive to ultraviolet and blue lights Rare earth elements are used in present-day screens as they are faster and have higher absorption and conversion efficiency: Gadolinium oxysulfide (Gd 2O 2S): green light Contains fluorescent materials called 'phosphors': Luminiscent layer - absorbs the x-ray photon and converts it to visible light that is recorded by the film. The absorption and conversion efficiency of the screen affect the intensity factor.įilm-screen combination typically used for chest radiography has a limiting resolution of 6 line pairs per mm, which is two times better than a typical digital radiography of 3 line pairs per mm 6. The intensity factor is a measure of efficiency of intensifying screen, and is the ratio photon exposures with and without intensifying screen to achieve a designated film density 4,5. The thickness of the screen affects the screen speed and spatial resolution: thicker screen improves speed but reduces spatial resolution (increased diffusion of light before image formation). The thickness of an intensifying screen is about 0.4 mm. In mammography, however, a single screen on the back side and a single emulsion film is used. In cassettes, which use double emulsion films, two screens are used, mounted on both sides of the cassette. It also reduces motion blur and x-ray tube loading by reducing exposure time. It decreases the mAs required to produce a particular density and hence decreases the patient dose significantly. Intensifying screens are used in the x-ray cassette to intensify the effect of the x-ray photon by producing a larger number of light photons.
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