Medical imaging is the use of machines that see inside the body, and of the software that makes and reads their pictures. It is also called radiology, after the X-rays it began with. The main kinds are four. An X-ray passes through the body and shows bones and lungs. A CT scan takes X-rays from all around the body and builds thin slices from them. An MRI scan uses a strong magnet and radio waves instead of X-rays. Ultrasound uses sound waves.
Every image must be read by a specialist doctor. A radiologist reads scans. A pathologist reads thin slices of tissue on glass slides. India has too few of both, especially outside the big cities. So software now does the first reading, and Indian companies build much of it.
Here is a typical case. A farmer has had a cough for a month. He goes to a district hospital in Bihar that has an X-ray machine but no radiologist. A technician takes his chest X-ray on the medical imaging equipment. Software inside the machine turns the raw measurements into a picture. This step is called image reconstruction.
Within a minute, an AI radiology model reads the X-ray. It marks a patch in the upper part of one lung and reports a likely case of tuberculosis (TB). Sorting cases by urgency in this way is called triage. The X-ray and the AI result go into the PACS and imaging AI platform, the system that stores every image and shows it to doctors. A radiologist in another city opens the X-ray there and confirms the finding. Reading scans from a distance like this is called teleradiology. Meanwhile, the hospital's doctor sees the flag and sends the farmer's sputum, the mucus he coughs up, for a TB test the same day.
The farmer also has diabetes. People with diabetes are more likely to get TB, and diabetes can also damage the back of the eye. So a health worker photographs his eyes with a retinal camera with AI screening. The camera checks for diabetic eye disease on the spot, with no eye specialist present.
Tissue samples need the same help. A digital pathology scanner turns a glass slide of tissue into a digital image. A pathologist in another city can then read it on a screen, through the same kind of platform.
AI that reads medical images is regulated as a medical device, because a wrong reading can harm a patient. This idea is called software as a medical device (SaMD). In every case, a doctor still makes the diagnosis. The AI decides only which case a doctor should look at first. Much of the scanners' own software is written in Bengaluru, where the largest scanner makers have big engineering centres.