AEC ChambersVanessa Lumpuy RTE1418 Function: Eliminate AEC Chambers the need for the radiographer to set an exposure time.device or the use of ionization chambers. stop the exposure when the image receptor has received the necessary radiation intensity. Automatically . Automatic exposure devices provide diagnostic quality exposures only for structures positioned directly above the ionization chambers.AEC Chambers Ionization Chambers . “The art of using AEC’s is the art of positioning. .an automatic exposure control device used to terminate the exposure after a desired exposure has been reached.” Ionization chamber AECs are usually used in a three-chamber configuration. . mA and kVp must be set manually. It is important that the location of the ionization chamber be determined and the precise positioning of tissue over that location be achieved.Radiographers The radiographer loses control over time when using an AEC. Positioning Skills Good positioning the majority of AEC exposures will produce diagnostic quality results. . Poor positioning – an increased repeat rate when using AECs. Combinations: 7 different combinations of the 3 chambers. Chest X-ray : right and left chambers are placed away from the mediastinum and completely within the lobes of the lungs. Example: .Configurations AEC consoles permit various combinations of the ionization chambers to be activated in order to control the exposure. -1. 3 ¼. 1 ½ Most labels use the center control as the normal density (0 and N) and permit both increases and decreases. 1. N. 2. Controls regulate the IR exposure but have different labels depending on manufacturer: -3. 0.Density Controls AEC systems permit the adjustment of the amount of radiation necessary to send the exposure termination signal. -2. 1 ¼. Some units use single density control and others . ½. Density Controls The density controls should not be used to compensate for patient part thickness or kVp changes. Example: When an image is slightly overexposed for the lung field and a decrease in exposure is desired even though the patient and ionization . Density control is accomplished when the configuration of the ionization chamber cells cannot be adapted to the necessary positioning. making an aerated lung overexposed for . Example: fluid in lungs causes increased subject density and contrast. which causes the AEC to remain on longer.AEC Problems Density and Contrast: When an unexpected density is present or when an expected density is lacking. AEC Problems Timing: Minimum Reaction Time: the length of time necessary for the AEC to respond to the radiation and for the generator to terminate the exposure. Example: Backup When the backup time is too short. Time: backup times cannot exceed the tube limit and should be set at 150% of the anticipated manual exposure time. it will terminate the . Stewart C. Adler.Work Cited Principles of Radiographic Imaging 4th Edition: Richard R. Radiologic . Science for Technologists: Physics Bushong. Carlton and Arlene M.