What is ac, ir, pc, tr?

Alternating current, infrared, computer, infrared.

The following are some abbreviations of commonly used terms in medical imaging. Where "AP" refers to the "anteroposterior position" of chest radiograph. When shooting the anteroposterior position, the tube is in front of the chest, and the ray passes through the chest and is imaged. "CC" refers to the "head and tail position" (also called "axial position" or "up and down position") of mammography, and X-rays are projected from top to bottom. "TR", also known as repetition time, is a commonly used parameter in magnetic resonance imaging (MRI). Because the MRI signal is very weak, in order to improve the signal-to-noise ratio of MRI, it is required to reuse the pulse, and the time between two 90-degree pulses is the repetition time.

What are PC lenses and TR-90 frames? What do PC lens and TR-90 frame mean? PC lens, that is, space film, is a kind of unbreakable lens with a safety of 100%. TR-90 frame is made of super tough resin, imported from Sweden, smooth, flexible and light, and comfortable to wear. Safety glasses worn in sports must be safe (PC lens), protective (TR-90 frame, soft and elastic), comfortable (anti-slip nose pad and foot cover) and beautiful (with sports and casual clothes).