Magnetic Resonance Imaging (MRI)
Another powerful imaging technique is Magnetic Resonance Imaging (MRI). MRI is one of the most important ways we see details of tissues inside the body. Unlike CT scans, MRIs can show both how tissues look as well as how they function. There are estimated to be more than 25 000 scanners in use worldwide.
In the 1930s, Felix Bloch and Edward Purcell discovered nuclear magnetic resonance (NMR). They worked at different American universities. But they were both able to show how magnetic fields and radio pulses can cause atoms to give off tiny radio signals. And by detecting these radio signals, you can create an image. This makes it possible to look inside objects without taking them apart or destroying them.
In the early stage of MRI many people did experiments. Herman Carr produced the first one-dimensional MRI image in 1952. In 1972, the physicist Peter Mansfield found a way to make images clearer. He also found a way to reduce scanning time from hours to minutes. In 1974, Paul Lauterbur created the first sectional images of a mouse. On July 3, 1977, Raymond Damadian, Larry Minkoff and Michael Goldsmith performed the first full body scan. In 2003, Lauterbur and Mansfield won the Nobel Prize in Physiology or Medicine for their contributions to MRI technology.
How it Works
MRI scanners use strong magnetic fields and radio waves to form images of the body. Over half your body is made of water. Each water molecule (H2O) contains two hydrogen atoms and one oxygen atom. The magnet in an MRI scanner causes the nuclei of the two hydrogen atoms to line up. Next, short pulses of radio signals cause the nuclei go back to their original positions. When this happens the nuclei emit weak radio signals that are detected by a receiver. The receiver sends the information to a computer. The computer then creates an image. MRI images capture a lot of details and can be colour-enhanced so that the various parts stand out even more.
Like CT scans, MRI scans are used to detect structural problems, such as tumours, blood clots, or damage caused by accidents and disease. One unique type of MRI is a Functional MRI (fMRI). An fMRI measures changes in blood flow within the brain. This technique allows doctors to visualize the living brain and observe changes to the brain as it undergoes different functions. CT scanners tend to be used more than MRI machines because they are less expensive to buy. However, as the price of MRI machines comes down, they will likely get used more often.
Did you know?
Since the introduction of fMRI in 1990, more information about the brain has been collected than in the previous 100 years!
Benefits & Risks
The greatest benefits of MRI machines are that they do not use x-rays. X-rays can be damaging to tissues and cause cancer). MRI machines are also better than CT scanners for taking images of soft tissues, like tumours. Unfortunately, MRI scans are slow. It can take anywhere from 10 minutes to an hour to produce an image! The machines can also be scary for patients who are claustrophobic (afraid of small, enclosed spaces).
Spotlight on Innovation
The Canadian Light Source Synchrotron
A synchrotron is a source of brilliant light that scientists can use to gather information about the structure and chemical properties of molecules in a given material.
A synchrotron produces light using radio waves and powerful electro-magnets to accelerate electrons to nearly the speed of light. Energy is added to the electrons as they accelerate. When the magnets alter the course of the electrons, they naturally emit a very brilliant, highly focused light. Different spectra of light, such as Infrared, Ultraviolet, and X-rays, are directed down channels for the light called beamlines. Researchers can choose the desired wavelength to study their samples. The researchers observe the interaction between the light and matter in their sample at the end stations (laboratories).
The synchrotron can be used to investigate matter and analyze physical, chemical, geological, and biological processes. Information obtained by scientists can be used to help design new drugs, examine the structure of surfaces to develop more effective motor oils, build smaller, more powerful computer chips, develop new materials for safer medical implants, and help with clean-up of mining wastes, to name just a few applications.
The Canadian Light Source is Canada’s national centre for synchrotron research and is located at the University of Saskatchewan in Saskatoon (Text from the Canadian Light Source).