Automatic exposure control method and automatic exposure control device for imaging device

Abstract

The invention discloses an automatic exposure control method and an automatic exposure control device for an imaging device. The automatic exposure control method includes performing the exposure process twice, processing pre-exposed images, calculating image gray values of tissue areas of portions under test, taking specific value of the mean gray value to the recommended value as the essential foundation for calculating secondary exposure parameter (the mA value or exposure time value), and limiting the regulated image gray value range according to the maximum gray value and the minimum gray value so as to guarantee high-quality images acquired by the secondary exposure and reduce X-ray radiation to people under test. Since the exposure parameters are estimated according to the image gray value statistic which is much direct than the signal to noise ratio, various images can be processed effectively, and automatic exposure control accuracy is improved.

Description

technical field [0001] The invention relates to automatic exposure control of imaging equipment, in particular to a control method and device based on double exposure. Background technique [0002] The purpose of the automatic exposure control system in the equipment for imaging diagnosis based on X-ray is to reduce the dose of X-ray exposure as much as possible while ensuring the image quality, so as to protect the examinee. At the X-ray source end, the parameters that can control the exposure dose are: 1) The bias voltage between the cathode and the anode of the bulb tube; it is usually expressed in kV (kilovolt) value; 2) The tube current of the bulb tube is commonly used in mA ( milliampere) value; 3) the duration of one exposure, commonly used time value s (seconds) to represent. Considering that there are great differences in the body shapes of clinical subjects (such as obese, thin, infants, etc.), and the body parts of each inspection may also be different, so the i...

AI Technical Summary

Problems solved by technology

Such requirements will increase the hardware manufacturing cost of the ionization chamber, and will also affect the accuracy of the ionization chamber for X-ray detection

However, the disadvantage of the method of the patent US6459765 is that the signal-to-noise ratio is used as the evaluation standard, and not only the signal strength of the tissue area in the image is counted, but also the noise level of the non-tissue area is counted, so as to realize the evaluation of the signal-to-noise ratio of the pre-exposure image

Once the projected image of the tissue area covers the entire detector surface, it will be difficult to estimate the noise, which will affect the accuracy of automatic exposure control

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