Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-11-16
2002-07-09
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C356S342000, C128S898000
Reexamination Certificate
active
06418339
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and a device for in vivo detection of the direction of Langer's lines in the skin.
2. Description of the Prior Art
Langer's lines (
Sulci cutis
) define the direction within the human skin along which the skin is least flexible. This mechanical property is determined by the alignment of collagen fibers and bundles of collagen fibers within the dermis.
The fundamental research on this property of the human skin was carried out by K. Langer and was already published in 1861. To determine the direction of the Langer's lines, he multiply pierced human cadaver skin at short distances. Although his piercing instrument was of circular shape, the resulting holes were of ellipsoidal shape. Langer observed patterns of the directions of the longer axes of the ellipsoidal holes on a skin area. Subsequently, these patterns were given the name “Langer's lines” according to it's discoverer.
The knowledge of the direction of Langer's lines within a particular area of the skin is of great importance for surgical operations. Generally and most importantly, a surgical cut should allow for an optimal opening of the area to be operated on and should also offer the possibility to extend the area during the surgery. At the same time, it must be made sure that the skin can heal properly after the surgery and that a beneficial cosmetic appearance is obtained after healing. These conditions are usually best fulfilled, if a surgical cut is carried out in the direction of Langer's lines. The generation of scares, in particular, is minimized under these conditions. This is of paramount importance in plastic surgery, where surgical cuts and potential scars run through visible body parts, such as the face.
Unfortunately, the accurate direction of Langer's lines often is not known. In some areas of the body, large differences exist in the direction between different persons. Even on the same person, changes in the exact direction may occur during the course of life. To account for these variations in the direction of Langer's lines during surgery, it is necessary to determine the direction using a non invasive method. With such a method, even less experienced surgeons would be enabled to plan a surgical cut with minimal scaring. This could reduce the esthetic and psychological problems associated with large scars and eliminate the need for post-operative treatment of scaring.
Despite the large importance of this problem, a suitable method for non-invasive measurement of Langer's lines is not yet available. In the past it was attempted to use mechanical tension measurements on the skin surface as e.g. described by J. C. Barbenell in an article “Identification of Langer's Lines”, pp. 341-344 in: Handbook of Non-Invasive Methods and the Skin, CRC Press, Boca Raton, 1995. In this publication, it becomes obvious that the described mechanical method does not give reliable information about the direction of Langer's lines in the skin.
BRIEF SUMMARY OF THE INVENTION
The goal of the invention is to measure the direction and the pattern of directions of Langer's lines on the skin surface non invasively and painlessly.
This problem is solved using light penetrating the skin. Light is irradiated as primary light into the skin at a defined site on the skin surface, in such a way that the light is transported in the skin by scattering and absorption. Part of said irradiated light emerges from the skin as secondary light in the region surrounding the irradiation site. As a measure of the direction of Langer's lines, the dependence of a measurable property of the secondary light is measured as a function of the polar angle around the irradiation site and the preferential direction of light transport in the skin is determined. This preferential direction of light transport indicates the direction of Langer's lines.
A measurable property of the light (subsequently also termed “measurement parameter”) is, particularly, the intensity of light. Other measurable properties of the light can also be used to determine the preferential direction of the diffuse light transport in the skin. E.g. the intensity of the primary light can be modulated. In this case, the AC amplitude (modulation) of the measured secondary light can be used to obtain information about the preferential direction of the diffuse light transport. When polarized light is used as primary light, the degree of polarization of the secondary light may be used. Generally, any measurable property of the secondary light, which contains information about the preferential direction of the diffuse light transport in the skin can be used. Subsequently, it is referred to the intensity as the measurement parameter as an example without restricting the use to using the intensity as the measurement parameter.
To determine the polar angle dependence, the primary light is irradiated into the skin within a small, specially confined area (irradiation site). A requirement for the determination of the polar angle dependence around the irradiated area is the measurement of the intensity of the secondary light on at least two detection sites. The polar angle (with respect to the irradiation area) of the at least two detection sites must have an orthogonal component. If only two detection sites are used, a difference in the polar angle of 90° is preferred, whereas the difference in the polar angle should be at least 35°.
At least three detection sites should be used to achieve an adequate resolution of the measured polar angle dependence of the measurable property. The difference in polar angle of the measurement locations should preferably be smaller than 20°. Especially preferred is the measurement of the measurement parameter at a multitude of locations located around the irradiated area, for which an angular resolution of at least 20° is preferred, i.e. the difference in polar angle between two neighboring measurement locations is not larger than 20°.
The wavelength of the primary light is preferably between 400 nm and 1400 nm. It is furthermore preferred, with respect to the accuracy of the measurement, that the light is predominantly monochromatic. It is sufficient, if the maximum half width is smaller than 200 nm, preferably smaller than 100 nm. Furthermore, the accurate determination of the preferential direction of light transport and therefore the determination of the direction of Langer's lines may be improved by using polarized light as primary light. Under certain conditions it may also be helpful to place a polarization filter between detection area and light detector.
Different detection sites can be obtained by using flexible detection means, e.g. light guiding fibers, which are moved from detection site to detection site. Especially preferred are embodiments, which incorporate a multitude of detection means to measure the polar angle dependence. In this embodiment, the individual detection means are positioned in a fixed location with respect to the irradiation site and measure the intensity of the secondary light with emerges from the skin at a defined detection site.
The detection sites, of which the measurement parameters are used to determine a polar angle dependence around the irradiated site, are preferably aligned on a circle around the irradiated site to ensure equal distances to the irradiated site. This eases the subsequent mathematical manipulation of the data. Furthermore, it was observed that the anisotropy for different distances between irradiation site and detection areas varies with the location of the human body. The reason for this effect is the dependence of the penetration depth of the light on the distance between irradiation area and detection area.
The measurement of the polar dependence of light intensity can generally be achieved with methods and means, which are known for other purposes, however, special requirements of the measurement need to be accounted for. WO 94/101 describe
Bocker Dirk
Essenpreis Matthias
Nickell Stephen
Dawes Daniel L.
Lateef Marvin M.
Myers Dawes & Andras LLP
Shaw Shawna J
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