The focal point is an important factor in radiographic technique. The so-called focal point is the intersection of a line extending in the direction of the primary x-ray exposure in the reverse direction; ideally, the focal point is a point, but in reality it has a certain area. The ideal focal point is a point that actually has a certain area. The focal point is divided into the actual focal point and the effective focal point from different perspectives.
1. actual focus Actual focus is the cathode lamp line emitted electrons hit the anode target surface area at high speed. The finer the electron beam, the smaller the area of the target surface of the anode, the clearer the image.
2. Effective focus The effective focus is the projection of the actual focus in the direction of x-ray irradiation. Because the anode target surface is a slanting surface with a certain angle, in the direction of X-ray photography, the influence on the imaging is the sine value of the actual focus. Usually x-ray tube labeled 1.0, 2.0 and other values is its effective focus of the nominal value.
As a science, medical imaging belongs to bioimaging and includes diagnostic imaging, radiology, endoscopy, medical thermography, medical photography, and microscopy. In addition, techniques such as brain wave mapping and magnetoencephalography, although focusing on measurement and recording without image presentation, can be considered as another form of medical imaging because the data produced has localization properties (i.e., contains positional information).
In terms of clinical application, it is also known as medical imaging, or imaging medicine, and some hospitals have imaging medicine centers, imaging medicine departments, or imaging medicine departments, with related equipment and a staff of specialized nurse practitioners, radiographers, and physicians responsible for the operation of the equipment and the interpretation and diagnosis of the images (which, in Taiwan, must be the responsibility of a physician), which is different from the department of radiology that is responsible for radiation therapy.