You are here: MEDICA Portal. Part II: Imaging. Neurology.
To Be in the Know with Every Detail (Part 2)
Part 2: Of Paying Attention to the Type of Radiation
Irradiated by Wilhelm Conrad
Röntgen: a woman's hand
Imaging technologies have revolutionised medicine. A little more than a hundred years ago, doctors were still dependent upon physical symptoms mainly on the body's outside for diagnosis. This changed when the German physicist Wilhelm Conrad Röntgen discovered an invisible radiation during an experiment in 1895. A little later the first X-rays in history came into being - such as a radiograph of a woman's hand skeleton that he irradiated for 20 minutes.
Scientists discovered then that this is not very healthy - X-rays can cause cancer. Engineers kept working on the technique and accomplished to reduce the intensity of radiation considerably during the last 30 years. However, some physicians are often still too lax when using radiation: According to the German X-Ray Society half of all X-rays in Germany are unnecessary. Also computer tomography (CT) - an impressive technology that delivers high resolution images from the body's inside and is irreplaceable in the diagnosis of a variety of certain serious diseases - works with X-rays and contributes considerably to the medical over-all exposure to radiation: in 2001, CT examinations made up six percent of all radiological examinations but in the same time were responsible for nearly 50 percent of human's contamination with radiation.
Benefits and risks need to be weighed up
The German Federal Office for Radiation advises an X-ray examination only when the patient benefits from it significantly so that the radition risk seems negligible compared to the benifits of diagnosis. And only when there are no other applications available that could deliver the same diagnostic information.
Other imaging technologies use optical radiation as for example methods that work with infrared light representing a possibility to fill some niches in diagnostics. „Near infrared spectroscopy (NIRS) is not the kind of imaging that produces high resolution images like a CT. It rather creates a surface mapping“, explains Professor Ulrich Dirnagl. The director of the Stroke Centre at the Charité in Berlin examines the oxygenation of the cortex with this method - the outer layer of nerve cells where a lot of sensory and motoric functions are located. Light from the near infrared penetrates tissue very well and is therefore suitable to reach these layers.
Take a look at oxygenation in
the outer layers - with infrared
light; © Dirnagel
It is important to observe oxygenation of the brain since a lack of the gas could cause major damage within minutes. „It is possible to observe and measure brain metabolism in neonates with NIRS“, says Dirnagel. „Another niche could be an examination of soft tissue like the female breast with near infrared light .“ One day it might be feasible to develop a kind of optical mammography. Also molecular imaging could benefit from NIRS because the method could provide new possibilities in finding markers with signaling molecules made of dye that can be detected by near infrared light.
Another application for NIRS maybe in the fight against arthritis: „Near infrared dyes can be injected into the hand joints and a special device can detect when the fluid exits from inflamed joints“, explains Dirnagel. The patient only has to stick its hand inside it and it will be illuminated with near infrared light in order to control progress in therapy. „This all is technically feasible. Now we need to determine whether NIRS is sensitive, specific and worth the money.“
- Part 1: To Be in the Know with Every Detail
- Part 2: Of Paying Attention to the Type of Radiation
- Part 3: A Glance Inside and At The Head - fMRT and Portrait Holography