14.07.2008

Microendoscope may replace painful muscle biobsy

Stanford researchers developed a new imaging technique: The instrument not bigger than a needle that can observe tiny muscle fibres in living patients is described in Nature. The technology may help to increase the understanding of how healthy muscles work and how they go wrong in diseases of motor control, such as Parkinson's disease and muscular dystrophy

[Bild-2]Muscle fibres are made up of repeated units, or 'sarcomeres', that act as the powerhouse behind contraction. They are generally involved in coordination movements. But out-of-sync sacromeres are implicated in diminished muscular control, for instance muscular dystrophy.

Now Mark Schnitzer, Scott Delp, and colleagues from the Stanford’s Bio-X-program have developed a laser-scanning imaging system to observe sarcomeres in living tissue directly by using a needle less than half a millimetre in diameter. The team has used the new system to make the first ever measurements of how individual sarcomeres respond to changes in body posture, in living subjects and in real time.

The needle-thin probe is inserted through the skin into muscle. When a flash of finely tuned laser light is sent through the probe, the sarcomeres respond with light of their own to form a snapshot of muscle in action. The researchers see the images in real time on a display screen. A change in the depth of focus of the rapidly scanning device can provide a three-dimensional movie. "This is a method that does not require any operative procedures," said Mark Schnitzer, an assistant professor of biology and of applied physics. For the first time, "it allows us to view individual sarcomeres in live humans."

[Bild-1]This microendoscopy technique for viewing sarcomeres - microscopic lengths of muscle fiber about 3 millionths of a meter long - has advantages over the uncomfortable alternative, a muscle biopsy in which a portion of the muscle is removed for examination.

The technology could prove useful in understanding how muscles are altered by spinal cord injuries or strokes as well as muscular diseases, according to another of the researchers, Scott Delp, a professor of bioengineering and of mechanical engineering and, by courtesy, of orthopedic surgery.

Other areas of interest include biomechanics, orthopedic reconstructions, prosthetic devices and tendon transfers, in which tension adjustments are a crucial element for patients relearning how to walk or grasp. "If you measure the length of the sarcomeres during surgery, then you can adjust them to work at their optimal length, giving maximum muscle strength," Delp said.

_{Photos: M.Schnitzer, Standford Bio-X-Program}