Touching Lives - February 2007
Some of the most significant advances in medicine have occurred in the field of imaging. It started with X-rays at the end of the 19th Century, and now there is a large variety of methods which allow the non-invasive examination of almost any part of the body.
Some of the methods can produce three-dimensional images, some can detect particular chemical reactions and “see” detail which would be invisible to the eye, even if the structure inside the body were exposed surgically.
Surgeons concerned with the repair of complex bone fractures want to know how well the injury is supplied with blood. Perhaps not everybody realises that bone is alive, even in an adult, and that material is continually exchanged between it and the blood stream. This is of course particularly important when the bone has to repair itself after a fracture.
There is a magnificent scanning technique for looking at soft tissues like the brain called MRI (magnetic resonance imaging), which does not work so well on hard substances like bone. MRI produces its images by sending in pulses of energy, which interact with some species of atoms, and in an electrical sense, makes them ring like little bells. It is this ‘electrical ringing’ which is picked up by the MRI machine and assembled into an image.
If one wants to visualise hollow spaces filled with liquid, like a blood vessel that supplies a bone, it is not uncommon to inject a contrast medium — a substance that shows up much more vividly on an image — into the liquid. This is where the gadolinium comes in. It is a metallic element which exhibits strong magnetic properties. Its atoms are particularly effective ‘little bells’ and show up strongly in an MRI scan of a contrast medium containing gadolinium.
The Action Medical Research grant featured on page 13 also uses a special kind of MRI scan called ultra short echo time (UTE) because the ‘little bells’ in hard bone do not ring for very long, and the machine has to respond much faster. Again, Action Medical Research right at the cutting edge. TL