It is seemingly impossible to imagine the method people used to diagnose cancer before the invention of x-rays. It's invention has allowed a much easier diagnosis method for doctors.
Prior to these imaging techniques, the only way a scientists can learn more about human body is cutting dead bodies (autopsy). Even with this method scientists could not get a clear picture of the organs when it is functioning.
Enter MRI and PET. No longer was autopsy or cutting needed to see the inside of a body, but doctors and scientists can now "see" the organ when the target is still alive. Better yet, PET and fMRI allows scientists and doctors to see these organs "work", on the spot. It would be a much better alternative than cutting someone who is still alive, and seeing how the organs work.
Before X-rays, people can't have medical screenings too easily, but with it's invention, the cheap machine is now used worldwide for regular check-ups, accessible to many people. This impacts on the population level, with a better outcome in the general health of the population.
Babies can now be screened with obstetrics ultrasound. Early childhood problems can be detected, and prior arrangements to treat any disorders can be done much earlier, removing problems that would happen at birth.
Cardiac problems are now able to be screened thanks to the Doppler ultrasound technology, which allows early detection of cardiac problems.
With endoscopy, doctors can see inside the bodies of patient thanks to the invention of optical fibres. Big cuts / incisions are no more needed on the patient, as the endoscope is so thin, it can be inserted through any openings in the body (eg colposcopy). Doctors can now even take samples off those "hard-to-reach" places, like aluminium kebab coverings that are accidentally eaten and breathed, which ends up in the lung (biopsy).
The invention of internet and computer were made possible by physicists, with the invention of transistors and integrated circuits. Computers are used today as an inseparatable part of medical physics, to display images from MRI, PET or CT scans, due to their ability to calculate signals with algorithms to images.
The internet itself was invented by physicians (DARPA USA), using optical fibres to transmit data, and now allows doctors to go browse websites as a reference. When you search for "X-rays" in google search engine, 646 000 results comes out. It shows on how big of an information "library" the internet have become in the medical field.