propylene glycol peak: resonates at 1.N-acetylaspartate (NAA) peak: resonates at 2.0 ppm.glutamine-glutamate peak: resonates at 2.2-2.4 ppm.gamma-aminobutyric acid (GABA) peak: resonates at 2.2-2.4 ppm.2-hydroxyglutarate peak: resonates at 2.25 ppm.arterial spin labelling (ASL) MR perfusion.dynamic contrast enhanced (DCE) MR perfusion For instance, in the United States, people are exposed to average annual background radiation levels of about 3 mSv exposure from a chest X-ray is about 0.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 fibre 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).Related (though discrete) principles include automatic brightness control (ABC) in fluoroscopy and tube current modulation in CT. The patient's position should align with the chambers such that the left and right are behind their lungs, whilst the central is behind the spinal column. In chest radiography, typically three ionisation chambers are used a left, right and central chamber. This is mainly due to the low energy requirement for mammography if the AEC device was placed in front of the receptor, the device would produce an image on the receptor, confounding the mammogram. In mammography, the automatic exposure control device is placed underneath the image receptor. In radiography, the automatic exposure control device is placed in front of the image receptor. These phototimers/ionisation chambers terminate the exposure once the radiation detector receives a predetermined signal of radiation (which indirectly means the image receptor is sufficiently exposed). The first generation of automatic exposure control systems are phototimers, which are now largely superseded by ionisation chambers.

Its function automatically terminates exposure when a preset amount of radiation has been detected.Īutomatic exposure control systems help to provide a consistent optical density/ signal-to-noise ratio between images, regardless of patient-centric factors such as size and density.Īutomatic exposure control systems also help to reduce 'dose creep' that can occur with inadvertent radiation overexposure by the technologist. Automatic exposure control (AEC) is incorporated into radiographic and mammographic imaging systems.

Under exposure x ray