PRESS RELEASE
August 16, 1996
Blood flow measured without a touch

Some years ago Lisca Development AB of Sweden introduced the first commercially available Laser Doppler Perfusion Imager (LDPI) for visualizing the flow of blood in the microvessels of tissue. Now the value of this emerging technology has been reported in several areas of medicine throughout the world.
Unlike most other microvascular techniques, this non-invasive method requires no physical contact with the tissue when creating a graphic colour image from multi-point measurements by way of a remotely positioned scanning head. The equipment allows the operator to select the resolution and area of interest, ranging from large surface imaging down to a high resolution image as small as a fingertip.

The technique is a further development of the laser Doppler blood flowmeter which was first introduced in the late 70´s, where photons from a laser source are scattered by moving objects (blood cells in this application) making the reflected light frequency shifted in a slight but measurable degree, in accordance with the Doppler principle.

Refined System
The conventional laser doppler flowmeter is limited to measuring one very small volume of tissue at a time by utilizing a small probe attached to the tissue surface, allowing only temporal changes to be recorded. No measurements of the important spatial variation in distribution are available with this approach.
This limitation of the technique has been overcome by Lisca´s unique imager design which involves a low power laser beam that progressively tracks along in very small steps, penetrating the tissue by a few hundred micrometers where upon it is reflected and scattered by the moving blood cells. This frequency shifted light is then successively read by a photodetector in the scanning head and is recorded as a map of more than 4000 individual measurements presented on a computer screen as a colour coded image which may be stored or printed. This approach allows fundamental features of tissue perfusion to be examined in a simple and accurate manner.

Malmo in the south of Sweden First
The first noted clinical centre which has used the new Lisca imaging system since its installation in 1992, is at the Malmo General Hospital in southern Sweden. Henry Svensson, a plastic surgeon who regularly uses the system there recently commented:
" LDPI has made it easier for us to optimize treatment of our patients and to gain a more objective base from which to make vital decisions. Before, we had to rely on visual interpretation of a patient´s external symptoms such as pale skin colour which we assumed implied bad circulation. Another method we used was thermographic imaging which can be inconclusive. With LDPI you get an objective measurement of blood circulation and all its variations in detail."
The main application of the LDPI at Dr. Svensson´s department is the assessment of vascular damage and disease before treatment.
"LDPI is very useful when establishing whether a damaged tissue is healed enough to be subjected to transplantation, " commented Dr. Svensson on this subject. "The high resolution makes it possible for us to establish this with extreme precision".

A new opportunity
The importance of blood perfusion in tissues has been recognised by even the earliest medical researchers, but only recently the precise technologies necessary to examine it in detail have been developed. The Lisca Laser Doppler Perfusiuon Imager is said to represent a new dimension in understanding both healthy and disturbed microvascular perfusion as seen in injuries or in many types of diseases. Its applications extend from dermatology, radiation oncology, vascular assessment and pharmacology to involved selection and evaluation of procedures such as in plastic surgery or burns treatment. A new opportunity to move the valuable laser Doppler technique from the research laboratory to the many clinical and surgical fields of medicine has presented itself and already important progress has been reported internationally in the exciting challenge of understanding microvascular perfusion which eventually will benefit us all./ins

Figure 1: The images in the figure show the increase in foot sole tissue perfusion following lumbar sympathetic blockade in a patient with peripheral vascular disease (left: before injection of drug; centre: 2 minutes after injection; right: 30 minutes after injection).

Figure 2: Laser Doppler perfusion image of the back of the hand after application of a vasodilating cream.

For further information, please contact:
Gert Nilsson
Lisca Development AB
Lovsbergsgatan 13
S-582 69 Linköping
Tel/Fax:+46 13 16 15 40