A major change to Roentgen’s original setup came in the 1990s with the introduction of powerful digital computers. Physicians realized they could capture images with digital equipment, without using film.
A similar thing has happened with the cameras we carry with us to take photographs on vacation, or to take pictures of everyday life. Your parents probably remember when such devices used film – just like X-rays.
Filmless radiography systems were first proposed in the early 1970s, but the technology wasn’t yet mature enough to put systems into production. The first clinical use of filmless radiography – or computed radiography (CR), as some call it – was in Japan in 1983. By 1988, more than 5,000 CR systems were in use in the United States.
Digital medical imaging presents numerous advantages to diagnosticians and other medical personnel. Images can be viewed immediately, in real-time, without a wait for film processing. Because the images are on a computer, they can be processed using modern software tools to sharpen them, change the contrast, highlight or focus on certain areas, and so on. There is no danger that film will be lost, destroyed, or misplaced. And multiple doctors can view the same diagnostic images at the same time, even if they are located on different continents.
Perhaps the most exciting development is the creation of new computer-enabled tools in the field of radiology. Today, medical teams can call upon a broad palette of medical imaging technologies derived from Roentgen’s original work, including advanced X-ray radiography, magnetic resonance imaging, ultrasound, endoscopy, elastography, tactile imaging, thermography, medical photography, and positron emission tomography (PET) scans, and computed tomography (CT) and computed axial tomography (CAT) scans.
CT scans, MRI, and PET scans
The CT scan has proved especially beneficial. A CT scanner – more properly, an X-ray computed tomography system – produces hundreds or thousands of two-dimensional X-ray scans of a patient’s body. These scans are then uploaded into the computer and assembled into a three-dimensional image. Radiologists can manipulate the images at will, giving them almost as clear a view of a patient’s body as he would get from exploratory surgery. Radiologists can peel away successive layers of skin and tissue from the image, zooming deeper into the patient’s body as necessary to discover abnormalities associated with injury and disease. CT scans have led to faster and better diagnoses, a reduction in dangerous surgeries, and better outcomes for patients. In short, CT scans save lives.
The next technology to offer physicians a deeper view into their patients was magnetic resonance imaging, or MRI. In MRI, patients are exposed to a strong magnetic field that is positioned around the area to be inspected. The magnetic field excites the hydrogen atoms in water molecules within the body, and the atoms emit radio waves at a particular frequency. The atoms return to their normal state at a different rate depending on what kind of tissue they are located in. This difference allows computers to use the fading radio waves to construct detailed three-dimensional images of the patient’s body. Several of the physicists and physicians who worked on MRI theory and technology were awarded the Nobel Prize. That is an indication of how important a breakthrough MRI imaging has proved to be.
Also important is positron emission tomography. PET scans are conceptually similar to X-rays, but the source of the rays is within the body, not outside it. With a PET scan, a short-lived radioactive isotope is introduced into the body, usually by being injected into the bloodstream. The isotope is especially tuned to concentrate in the tissues that diagnosticians wish to study. The result, when two-dimensional images are processed and combined, is a highly detailed three-dimensional model of the patient’s internal body structures.
CT scanning, MRIs and PET scans have made fundamental changes in the way doctors diagnose diseases, identify injuries and sources of infection, and plan and conduct surgery.
Innovations Yet to Come
Despite the growing use of digital imagining in medicine, plain old film-based X-rays are still in use, and are likely to remain so for years to come. In the future, however, medical teams will capture almost all medical images in computers so they can be archived, emailed to experts for second opinions, digitally enhanced, compared with other images, and processed into three-dimensional images.
Stay tuned for Part 4 of our Brief History of Radiology with a look exciting developments that point toward future breakthroughs in medical imaging.