WO1998044841A1

WO1998044841A1 - Device for optic identification of blood vessels

Info

Publication number: WO1998044841A1
Application number: PCT/SE1998/000672
Authority: WO
Inventors: Håkan UGNELL; Lars-Göran LINDBERG; Ivo Fridolin; Åke ÖBERG
Original assignee: Ugnell Haakan; Lindberg Lars Goeran; Ivo Fridolin; Oeberg Aake
Priority date: 1997-04-09
Filing date: 1998-04-09
Publication date: 1998-10-15
Also published as: SE9701303L; AU7092998A; SE9701303D0

Abstract

At many medical diagnostic problems it is desirable to be able to detect and visualize different blood vessels and blood vessel changes (in e.g. blood vascular wall). This desire has been solved through using a light source (1), a photodetector (2), a motor system (5) for measurement of different spots and a specific combination of different measurement geometries (8, 10 and 11) whereby you may record reflected radiant power from different structures in the tissue (7), whereupon you may monitor blood vessels (9) through a picture on a monitor (4). After identification it is also possible with this equipment to monitor different physiologic parameters.

Description

Device for optic identification of blood vessels

The present invention relates to a device with a light source, photodetector and two motors, by which reflected light can be recorded on a number of spots on the skin or on an organ. The reflected radient power from each spot varies depending on how much light is absorbed in different structures of the tissue, like e.g. vessels and the walls of the blood vessels. The spots where the registration occurs, are searched out with the aid of the two motors which move the light source and the photodetector in two or more longitudinal directions, whereby a colourcoded picture of vessel structures can be built up to be presented on a screen or a paper.

Background of the invention

Many existing metods for the identification of vascular beds in different diagnostic problems often include some form of ultrasound equipment. Ultrasound examinations of the arterial system plays an important role in non-invasive examination of patients with vascular diseases. Ultrasound examinations may also give information about the state of the blood vessel wall and the position and size of stenoses. New possibilities for studies within the cardiovascular system arouse when the magnetic resonance (MR) scanning technique was introduced. MRI (magnetic resonance imaging) and MRA (magnetic resonance angiography) have given the radiologists a new diagnostic tool for the visualization of relative blood flow and stenoses in the large blood vessels of the brain, the head, the neck, the breast, the pelvis and the limbs.

Recently, for the control of peripheral perfusion of blood in the skin a new scanning laser- doppler technique has been introduced, for monitoring of a larger skin surface, maximum 12 cm x 12 cm. Picture generation of perfusion of blood in the skin is important in studies of the effect from peripheral vascular diseases on the microcirculation.

The purpose of the invention and the most important characteristics

The purpose of the invention is to:

identify blood vessels och subsequently record different physiological parameters locally on the skin or on organs, which gives unique possibilities that the above described methods do not possess. identify blood vessels with the aid of light on a vascular level, where existing ultrasound methods and laser-doppler technique have difficulties. This means that blood vessels with other dimensions and on other vascular depths than earlier, can be visualized. identify vessels on deeper levels in the tissue (>3mm), meaning a technically easier and above all a cheaper alternative compared to ultrasound methods in many clinical applications.

Some applications in medicine

I. Optical vessel identification

The technique may give rise to new possibilities for vessel diagnosing and vessel identification in a tissue bed which is not vascularly anatomically known. By using a sensor which can sense reflected light in a number of spots which are distributed across a skin section, the vascular system under the sensor can be mapped and a "vascular map" can be plotted on a computer screen or a monitor.

1. Surgical interventions

A surgeon would with the aid of a reasonably simple handheld sensor gain an opinion about how middlesized and smaller vessles crosses a plausible operation area. Certain vessles could then be avoided from damage whereby the operation takes less time (less ligation and coagulations) as well as that the advantage that the post-operative healing course is favoured by a vascular bed which is as intact as possible.

2. Shunt construction, bypass-operation

The construction of an arterial -venous shunt in e.g. the forearm or the leg is made easier due to the "vascular map" which in turn increases the precision and the quickness of the intervention.

3. Stereotactical venipuncture.

In venipuncture it is sometimes very difficult to identify the vein due to obesity in the patient or deeply located veins. An example showing stereotactic puncture according to this method is vein test in the bend of the arm. E. g. small children in the age of 6 months-

1 year have a large amount of subcutaneous fat, which sometimes makes it very difficult to identify their veins when sampling. Another example is when constructing a central vein catheter ( CVC) in the throat for nutrition and monitoring. The catheter is placed in vena jugularis interna above the right atrium. The depth of the vein is approximately 10-12 mm. The catheter makes nutrient supply and central pressure measurement possible. The latter is important for monitoring the blood volume of the patient, which in turn indicates how much liquid the patient needs.

II. Vessel identification and monitoring of physiological parameters.

After the identification of a vascular bed (artery, vein or smaller vessel) the possibilities are given for local monitoring of different parameters in the vessel or the vascular area which has been identified. When the type of the vessel is identified you may with the help of the light source-photodetector pairs which are situated above the veins or arteries, record the parameter which is of interest, e.g. pulsatile blood flow.

Pulsatile bloodflow

Through recording the changes in the pulsatile blood flow (PPG) or through deciding which type of blood vessel (artery or vein) the probe is "looking at", you may monitor the circulation locally.

General preoperative monitoring

The technique may be used in order to guide the surgeon when it comes to separate damaged tissue from healthy, through monitoring of local pulsatile blood flow (PPG). This applies to all types of reconstructive surgery e.g. burns (transplantation), reconstruction of limbs and to organs such as heart, liver and kidneys.

General postoperative monitoring

After e.g. a bypass-operation in the groin where a shunt is placed between arteria femoralis and arteria poplitea you want to monitor the recirculation in the leg/foot. The device placed around the ankle or on the upper side of the foot is used for monitoring the pulsatile blood flow over the vascular bed. Identification of arteriosclerotic changes

In the case of stenosis in the vascular tree you want to identify the vascular bed which is subjected to impaired blod supply. The device is used in order to localize where on the foot, the arm or the organ where the reduced blood flow is. In that way you may also identify where the stenosis is located.

Controlling of arterial needles

In patients where the arterial needles are applied on e.g the upper side of the hand during a long period there may sometimes occur circulatory disorders due to the hindrance of the blood flow by the needle. The device may be used for monitoring of the circulation over the specific artery.

Description of the drawings

Fig. 1 An example of equipment for optic identification

Description of embodiment

In the drawing, designation 1 is a light source, 2 is a photodetector, 3 is a PC (personal computer), 4 is a monitor (computer screen etc), 5 are motors and a holder for optical fibres which is movable in two directions perpendicular to each other, 6 are optical fibres which are mounted to 5, 7 is tissue in the form of skin or an organ , 8 is the distance between the light source and the photodetector, 9 is a blood vessel, 10 is the distance between the skin surface/organ surface and the blood vessel, that is depth, 11 are fibre characteristics concerning fibre diameter and fibre tip geometry which decide which distribution and capture angle the fibres possess.

Claims

1. A device for optic vessel identification comprising a light source (1 ) which illuminates the skin or organ (7) in a number of spots, whereby reflected radiant power is recorded for each spot on the skin or organ (7) with a photodetector (2), followed by colourcoding of recorded reflected radiant power from each spot, a picture after data analysis (3) being presented of the vascular tree on a monitor (4), characterized in that, two optical fibres (6) are placed beside each other, one of which is adapted to transfer light from a light source and the other is adapted to transfer light to a photodetector, and said fibres are movable in two perpendicular directions by means of two stepping motors (5) which are controlled by a microcomputer and a personal computer (3).

2. A device according to claim 1 , characterized in that said two fibres are movable with the help of a hydraulic system which transfers power from said two motors (5) to the fibres (6).

3. A device for optic vessel identification comprising a light source (1) which illuminates the skin or organ (7) in a number of spots, whereby reflected radiant power is recorded for each spot of the skin or organ (7) with a photodetector (2), followed by colourcoding of recorded reflected radiant power from each spot, a picture after the data analysis (3) being presented of the vascular tree on a monitor (4), characterized in that a number of semiconductor components are placed beside each other, half the number of which consists of light diodes (light source) and the other half of photodetectors are made of silicon material, one light diode-photodetector pair at a time being activated electrically and being controlled such that the pairs are coupled in two perpendicular directions.

4. A device according to claim 1, characterized in that a specific distance (8) is chosen between light source and photodetector, the distance deciding the depth you can detect one or more blood vessels and the possibility to distinguish two vessels lying over each other.

5. A device according to claim 1, characterized in that a certain diameter (11) or surface on ^"both the light source and photodetector is chosen. The diameter or the area of the light source or the photodetector decides the detectable depth for a vessel and also the detectable diameter of a vessel.

6. A device according to claim 1, characterized in that a specific optical wavelength between 600 nm and 1300 nm is chosen. The wavelength is chosen depending on the depth or the level in the tissue where you want to detect the vessels.

7. A device according to claim 1, characterized in that different scattering angle (11) of the light source (1) and the capture angle (11) of the photodetector (2) decide the depth on which blood vessels are detectable .