X-ray detectors and tubes are the two parts of an X-ray machine that make the X-ray beam and capture the image. The tube makes the X-rays. The detector, a flat electronic panel on the other side of the patient, catches the X-rays that pass through the body and turns them into a digital image. Some companies make only these parts, and sell them to the companies that build complete machines.
An X-ray tube works like this. A thin wire, called the filament, is heated until it gives off electrons. A high voltage, often between 60 and 140 kilovolts, pulls the electrons across the tube at great speed. They hit a metal target, usually tungsten. Most of their energy becomes heat, and only about 1% becomes X-rays. So heat is the main problem in a tube's design. In CT tubes, the target is a disc that spins fast, which spreads the heat around its edge.
A flat-panel detector works in two steps. First, a layer of crystal, often caesium iodide, glows where X-rays strike it. Second, a grid of millions of tiny light sensors under the crystal measures the glow at each point. Each sensor becomes one pixel of the image. Electronics read the grid row by row and send the numbers to the machine's computer. These electronics are built from analog and mixed-signal chips. Before flat panels, X-rays were captured on film, which had to be developed in a darkroom.
Imagine a mobile X-ray van that screens villages in Odisha for tuberculosis (TB). The van carries an X-ray tube and a flat-panel detector of 43 × 43 centimetres, with about 3,000 × 3,000 pixels. A villager stands with his chest against the panel. The tube runs at 120 kilovolts and fires for a fraction of a second. About five seconds later, the image, of about 90 lakh pixels, is on the van's screen. An AI radiology model reads it at once. With film, the van could not have given anyone a result the same day.
The detector sets the limit on how good the image can be. A more sensitive panel gives a clear image with a lower dose of X-rays. A panel with smaller pixels shows finer detail, which matters for mammograms, the X-rays of the breast.
The same parts are used outside hospitals. Airport baggage scanners and border cargo scanners use X-ray tubes and detectors, and these are run by security screening systems. Factories use them to look inside metal castings, in industrial CT scanning. In hospitals, they sit inside medical imaging equipment made by the large scanner makers.