Which part of the fluoroscopy unit receives remnant radiation from the patient?

The input phosphor is the correct answer because it plays a crucial role in capturing remnant radiation after it has passed through the patient. In a fluoroscopy unit, once the X-rays created by the primary beam interact with the patient's tissues, some of these X-rays exit the body as remnant radiation. The input phosphor, typically made of materials like cesium iodide, absorbs this remnant radiation and converts it into visible light.

This light is then further processed to create images that can be viewed in real-time on a monitor. Understanding this process is vital for ensuring high image quality while minimizing radiation exposure to the patient.

The other components mentioned, such as the accelerating anode, photocathode, and output phosphor, have different roles in the fluoroscopy system. For instance, the accelerating anode helps to propel electrons towards the output phosphor, while the photocathode converts the light produced in the input phosphor into electrons. The output phosphor then converts those electrons back into light for display. Each component is essential, but it is the input phosphor that directly interacts with the remnant radiation coming from the patient.