Passage: Beam Hardening: X-ray radiation consists of hard and soft particles, i.e. particles with a lot of energy and particles with little energy. Unnecessary exposure is mostly caused by soft particles, as they are to weak to pass through the body and interact with it. Hard particles, by contrast, pass through the patient. A filter in front of the x-ray tube can catch the soft particles, thus hardening the beam. This decreases dose without impacting image quality.Frame rate: High frame rates (i.e. images acquired per second) are needed to visualize fast motion without stroboscopic effects. However, the higher the frame rate, the higher the radiation dose. Therefore, the frame rate should be chosen according to the clinical need and be as low as reasonably possible. For example, in pediatric cardiology, frame rates of 60 pulses per second are required compared to 0.5 p/s for slowly moving objects. A reduction to half pulse rate reduces dose by about half. The reduction from 30 p/s to 7.5 p/s results in a dose saving of 75%.When using pulsed fluoroscopy, radiation dose is only applied in prespecified intervals of time, thus less dose is used to produce the same image sequence. For the time in between, the last image stored is displayed.Another tool for decreasing dose is collimation. It may be that from the field of view provided by the detector, only a small part is interesting for the intervention. The x-ray tube can be shielded at the parts that are not necessary to be visible by a collimator, thus only sending dose to the detector for the body parts in question. Modern C-Arms enable to navigate on acquired images without constant fluoroscopy.

Question: What provides a field of view?
the detector