Scientists have developed a portable system for gauging the severity of Parkinson's disease symptoms.
A working prototype of the device
The device uses a body sensor to analyse walking patterns in minute detail.
It should help doctors to monitor the progress of disease, and to tailor therapy accordingly.
Details of the technology, developed by US and Japanese scientists, are published in the Journal of Neural Engineering.
Parkinson's disease is a progressive disorder of the central nervous system.
Symptoms include: uncontrollable trembling, difficulty walking, and postural problems that often lead to falls.
These symptoms are usually controlled with dopamine agonist drugs.
However, these can have a number of side-effects, such as jerking movements. It is also known that the body builds up a tolerance to the drug.
Understanding the nature and severity of symptoms for individual patients could help doctors improve a patient's quality of life, by guiding their treatment more effectively, and so reduce side-effects.
Researchers have previously tried to quantify the problems suffered by Parkinson's patients by studying their gait.
3 D analysis
The new system should help refine this approach.
It works by placing a sensor on the patient's body that measures movements in three dimensions.
The readings from this sensor are fed to a computer, together with measurements of the patients walking speed.
A technique called fractal analysis is then used to break down the body's motion into its component parts.
This works by looking for geometric patterns, called fractals, which give an indication of the complexity and irregularity of movement.
The researchers studied the movement of healthy volunteers and people with Parkinson's disease in this way.
The analysis found that movement was more complex in people with Parkinson's disease.
On average, those with Parkinson's had a fractal measure of 1.48 compared with a measure of 1.3 for the healthy volunteers.
The researchers believe that their method could be used to assess just how severe Parkinson's symptoms had become - the higher the fractal measure, the more advanced the disease.
Professor Metin Akay, of Dartmouth College's Thayer School of Engineering, one of lead researchers, said: "Advances in computer technologies, micro-sensors, and wireless communications have significantly broadened the possibilities for individual health monitoring systems."
He said the technology could be used to see how people with Parkinson's react to a range of different treatments, including the use of both drugs and surgery.
In a statement, the Parkinson's Disease Society welcomed the research.
It said: "We are keen to encourage people with Parkinson's to continue to live a full and active life for as long as they are able, and a well-managed drugs regime is central to this.
"Therefore any advancement that may enable practitioners to analyse the progression of a patient's condition, and tailor their therapy and medication accordingly, would be welcome."