On-line dose modulation method of X-ray CT (Computed Tomography) machine

Abstract

The invention relates to an on-line dose modulation method of an X-ray CT (Computed Tomography) machine, which comprises the following steps: scanning plain film data, extracting Z-direction attenuation information of a human body, and calculating the attenuation area of the human body in each cut film along the Z direction; according to the attenuation area, calculating the average X-ray dose in each cut film to form a dose distribution curve along the Z direction, and supplying to a user as an initial recommended value, so that the user can adjust the dose distribution in the Z direction as required; scanning a patient, and simultaneously carrying out on-line estimation on the attenuation value of the rotation direction of the patient to obtain an attenuation estimated value; combining the dose distribution in the Z direction with the attenuation estimated value of the human body in the rotation direction to calculate a bulb tube mA value; transmitting the mA value to a high-pressure system, and carrying out high-frequency dose adjustment; and finishing the on-line dose modulation process if the scanning is completed. The invention reduces the overexposure and underexposure possibly caused by assuming sine laws. Besides, the invention does not assume that what passes through the central passage is the maximum attenuation, so that the dose modulation is better matched with the shape of the actual object.

Description

technical field [0001] The invention relates to a control technology of X-ray dose in CT machine equipment, in particular to an online dose modulation method of X-ray CT machine. Background technique [0002] CT (computed tomography, computerized tomography) equipment is a fully functional disease detection instrument. For X-ray CT machine equipment, its main components include X-ray tube, X-ray detector, frame, scanning bed, etc.; X-ray tube is the source of X-ray emission, and X-rays are emitted from the focal point of the tube and pass through the human body. Arriving at the detector, the detector accepts X-rays and converts them into energy intensity signals for subsequent processing. The X-ray tube and detector are installed on the frame, which is driven by the frame to rotate around the center of rotation to realize the scanning of the patient. The center is a geometric center determined by the geometric design of the CT machine. During the scanning process of the CT...

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Problems solved by technology

[0004] Some existing attenuation estimation techniques need to assume the shape of the human body, such as assuming that the attenuation distribution of the human body in the direction of rotation of the X-ray tube is sinusoidal, and using statistical average attenuation coefficients for different human body parts, such as the patent "using a single internal Method for storing information position map to control X-ray tube current modulation" (Chinese Patent Application No.: 200410085526.0, Chinese Patent Publication No.: CN 1593345A), this hypothesis may cause overexposure or underexposure of tube mA at some angles in the direction of rotation ; Or assume the symmetry of the human body (approximation of the attenuation distribution per half circle) in the process of estimating the attenuation, such as the patent "A method for adaptively reducing the dose in a computerized tomography system" (Chinese patent application number: 98106003 .X, Chinese Patent Publication No.: CN1236727C), when the human body is eccentrically scanned, there is a certain error in this assumption, and it does not consider the movement of the human body in the Z direction between half circles in the helical scan, which may also cause the tube Overexposure or underexposure of mA

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