Classification of x ray machine collimator
According to the driving mode of the lead bar of the x ray machine collimator device, it can be divided into the following kinds.
1. Manual x ray machine collimator:
Manual x ray machine collimator is mostly used in photography. The opening and closing activities of this kind of x ray machine collimator are realized by adjusting the knob or pulling rod on the x ray machine collimator manually. In addition to the above, its internal structure is equipped with an indicator system for the radiation field. As a picture
It uses an indicator bulb to simulate the focus of the X-ray tube, replaces X-ray with visible light, and reflects through a mirror to the bed surface. The reflected visible light path is the same as the X-ray path after penetrating the mirror, so it can indicate the size of the irradiation field in advance. Because the life of the indicator lamp is short, the lighting of the indicator lamp is controlled by a button switch, which can be turned off by itself within 15 seconds to 1 minute. Some indicators have a life of two levels of brightness to meet the indoor brightness in the case of higher illumination field indication. Mirrors are usually made of silver plated plastic, and the aluminum equivalent is about 0.5mm, which does not affect X-ray imaging. In front of the beam limiter is also a clean transparent plastic plate engraved with black lines or black dots to indicate the center of the ray field.
Some beam limiters mark the irradiation field size with the corresponding focal length around the knob or within the range of pull-out rod activity, mainly for presetting the irradiation field before the irradiation field indicator light is turned on, so as to adjust the irradiation field size quickly after the indicator light is turned on, and prolong the service life of the indicator light.
2. Electric x ray machine collimator:
Electric beam limiter is mostly used in fluoroscopy, convenient for long-distance control, and is an essential component for remote control of gastrointestinal bed.
The opening and closing of the lead van of the electric beam limiter are usually driven by a miniature DC motor. By properly controlling the forward, reverse and running time of the DC motor, the irradiation field can be adjusted to the desired size. The adjustment of the irradiation field of the electric beam limiter is carried out either on the beam limiter or on the operating table beside the bed. The latter can be adjusted continuously, but there are also various fixed-size irradiation field selection buttons. If these buttons are pressed, the motor will drive the load leaf to the selected irradiation field and fix it. Photography that meets specific requirements. The motor operates with a limit switch in the lead leaf closing and maximum opening position. Automatic limit protection.
The electric beam limiter be specially used for fluoroscopy, especially in the fluoroscopy device equipped with an image intensifier, needs to adjust the size of the irradiation field at any time, so it does not need the irradiation field prediction and light display. Because the input screen of the image intensifier is circular, the structure of the shielded lead blade is usually lobe type, which makes the diameter of the irradiation field continuously changeable under the operation of the motor. The structure of lead leaves is shown in Fig.
3. Automatic x ray machine collimator:
The structure of automatic beam limiter and electric beam limiter is not much different. The difference is that the automatic beam limiter is equipped with a state detection device of leading leaf. With the change of the focal-screen distance, the automatic beam limiter has the ability to maintain the size of the irradiation field automatically, and is often used in fluoroscopy.
In fluoroscopy, in order to prevent patients from accepting unnecessary radiation, prevent X-ray from overexposure to the fluorescent screen, or outside the image intensifier, the beam limiter is limited in the circuit, so that the beam limiter field control rod at the maximum open position, the field of illumination and image intensifier input screen diameter is consistent, and with the focus-screen distance The change can track and control the size of the irradiation field, so that no matter how the focal-screen distance changes, the irradiation field will never exceed the edge of the input screen.
If spot photography is to be done in perspective, the X-ray machine sends out corresponding control signals to the control center of the x ray machine collimator while selecting the film specifications and segmentation methods. When spot photography is ready, the irradiation field changes from perspective to spot photography, and the size of the irradiation field is in accordance with the film and segmentation requirements.
Author:X Ray Collimator