A novel single-cell ion chambered AEC to reduce exposure dose for spot image acquisition in R&F applications

John Cox; George Jachode; Shigeru Onoda; Charles Latimer

doi:10.1117/12.2654290

7 April 2023 A novel single-cell ion chambered AEC to reduce exposure dose for spot image acquisition in R&F applications

John Cox, George Jachode, Shigeru Onoda, Charles Latimer

Author Affiliations +

Proceedings Volume 12463, Medical Imaging 2023: Physics of Medical Imaging; 124633K (2023) https://doi.org/10.1117/12.2654290
Event: SPIE Medical Imaging, 2023, San Diego, California, United States

Conference Poster

Abstract

Radiography and Fluoroscopy (R&F) modalities are used typically for diagnostic procedures such as GI studies using a contrast agent like barium or Gastografin and vascular studies using iodine. In older analog systems using an image intensifier for fluoro, spot image acquisition at higher doses is accomplished using a light sensor to measure the brightness of the light produced by the image intensifier. Modern R&F systems employing a flat-panel detector use an Automatic Exposure Control (AEC) or ion chamber designed for radiographic use to terminate the exposure. Typically, the AECs are set to their highest sensitivity producing spot images with about 30x the dose of a frame of fluoro imaging. Given the limitations of dynamic flat-panel detector technology, a much lower spot dose of only about 10x higher than fluoroscopic dose is more appropriate. These limitations include exposure time windows and dynamic range. The sensitivity of ion chambers used for AEC is determined fundamentally by their active volume and the gain of the preamplifier. Most radiographic AECs use three to five fields whose outputs are usually averaged. An AEC with a single, much larger ion chamber field provides a 3x improvement in sensitivity without changing the gain of the preamplifier compared to existing AECs used for RAD. Such an AEC has proven to lower the Spot image dose by a factor of three with improved contrast detail in R&F applications without the associated losses in signal to noise ratio associated with raising the gain of the preamplifier.

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John Cox, George Jachode, Shigeru Onoda, and Charles Latimer "A novel single-cell ion chambered AEC to reduce exposure dose for spot image acquisition in R&F applications", Proc. SPIE 12463, Medical Imaging 2023: Physics of Medical Imaging, 124633K (7 April 2023); https://doi.org/10.1117/12.2654290

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