The opening and closing process of the shielded lead blade of the manual rectangular collimation is realized by manually adjusting the knob on the rectangular collimation.
The manual rectangular collimation uses an indicator bulb to simulate the focus of the X-ray tube, and uses visible light instead of X-ray. It illuminates the bed surface through the reflection of the reflector in the rectangular collimation. The visible light path is the same as that after the X-ray penetrating the mirror, so it can indicate the size of the irradiation field in advance. Because the life of the indicator lamp is relatively short, the lighting of the indicator lamp is controlled by a button. 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 rectangular collimation is also equipped with a clean and transparent plastic plate engraved with black lines or black dots to indicate the center of the ray field.
The irradiation field size marked with the corresponding focal length around the knob of the rectangular collimation is mainly used for presetting the irradiation field before the irradiation field indicator light is lit, so as to quickly adjust the irradiation field size and prolong the service life of the indicator light.