Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Chemical analysis
Reexamination Certificate
1999-06-29
2002-06-25
Hilten, John S. (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Chemical analysis
C702S172000
Reexamination Certificate
active
06411907
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of tissue injury analysis. More particularly, the present invention relates to a method and apparatus for objective tissue injury analysis. Specifically, a preferred embodiment of the invention relates to a method in which spectral data is produced that pertains to the intensities of individual wavelengths of an electromagnetic signal reflected from the tissue injury, and then an indication of the nature of the injury to the tissue is provided based upon the results of analyzing the spectral data. The present invention thus relates to a method and apparatus for tissue injury analysis of the type that can be termed objective.
2. Discussion of the Related Art
Within this application several publications are referenced. The disclosures of all these publications in their entireties are hereby expressly incorporated by reference into the present application for the purposes of indicating the background of the present invention and illustrating the state-of-the-art.
Tissue injury is common in daily life. Tissue injuries include, for example, burns, rashes, skin infections (inflammations), and allergic reactions associated with allergies and tests for allergies. With respect to burn injuries in particular, for example, approximately 70,000 serious burn cases are reported in the United States every year, at a cost to the economy of an estimated two billion dollars. Traditionally, burns have been classified as first, second, or third degree, based on visual criteria. First-degree burns are visually indicated by redness and blistering of the skin. Second-degree burns are visually indicated by withering of the skin without charring. Third-degree burns are visually indicated by eschar formation and charring.
This type of classification, which has been used with only minor alterations for nearly two hundred years, is concerned chiefly with the intensity of burning and not with the depth of tissue destroyed. Only recently have burn physicians come to realize that the depth of injury is of greater importance than superficial appearance. The classification of burns that has recently been adopted has completely forsaken all reference to outward appearances, which are only an indication of the severity of surface burning. The new type of classification recognizes two degrees of burn injury. The first new classification is partial-thickness skin loss, implying the presence of sufficient living epithelial elements to resurface the area. The second new classification is full-thickness skin loss, implying virtually complete destruction of all epithelial elements so that healing can only occur by contraction of the wound and epithelial cell migration from the edge of the wound or by surgical intervention.
Proper treatment depends on the correct classification of the burn. Further, early differentiation between these two degrees of burns is critical for several reasons. It is better to excise dead tissue and close the wound than to allow spontaneous separation of the slough, with its attendant risks of infection, fibrosis, and loss of function. Surgical results are best when the proper treatment is taken within the shortest time. The sooner a definite diagnosis is made, the sooner the patient can leave the hospital, decreasing costs for both the hospital and the patient. In life-threatening burns, and especially when donor sites are at a premium, it is very important to distinguish quickly between full-thickness and partial-thickness burn injuries.
FIG. 1
shows a model of a three dimensional section of human skin. Two major tissue layers are conventionally recognized as constituting human skin
5
. The outer layer is a thin stratified epithelium, called the epidermis
10
, which varies relatively little in thickness over most of the body. The human epidermis is typically between 75 &mgr;m and 150 &mgr;m thick. Underlying the epidermis
10
is a dense layer of fibrous elastic connective tissue, called the dermis
20
, which constitutes the mass of skin. The dermis
20
supports extensive vascular and nerve networks, and encloses specialized excretory and secretory glands and keratinized appendage structures such as hair and nail. Beneath the skin is the subcutaneous tissue, or hypodermis
50
, which is variously composed of loose areolar connective tissue or fatty connective tissue displaying substantial regional variations in thickness. Nerves
25
pass through the hypodermis
50
. Of particular interest is the presence and depth of hair follicles
30
and sweat glands
40
in the dermis. The bases of these structures are surrounded by cells capable of forming new “skin.” These cells lie very close to the interface of the dermis and the subcutaneous fat
60
, and represent the vital plane insofar as spontaneous skin repair is concerned. If destruction occurs below this vital plane, the burn is a full-thickness burn; if above this vital plane, it is a partial-thickness burn.
The blood supply in the skin comes from cutaneous branches of the subcutaneous musculocutaneous arteries. Branches arising from the cutaneous arteries give rise to a distinctive small vessel plexus which lies deep in the dermis near and parallel to the interface with the subcutaneous tissue. Therefore, destruction of a large area of hair follicles and sweat glands in a full-thickness burn devascularizes the skin in the same area. This is the basis of several previous burn diagnosis methods that use the new type of classification.
However, classifying a burn is not easy immediately after the burn occurs, and usually depends upon intuition about the appearance of the burn rather than upon accurate description and definition (i.e., objective characterization). Early visual assessment may be difficult because the ability of the wound to heal depends strongly on the condition of underlying tissues, which in the case of severe burns are generally obscured by overlying layers of dead and denatured skin. Thus, three days after burns were incurred, the surgeons in one study were only willing to commit themselves to a predication in about two thirds of the cases. Heimbach, D. M., Afromowitz, M. A., Engrav, L. H., Marvin, J. A. and Perry, B., “Burn Depth Estimation—Man or Machine,”
The Journal of Trauma
, vol. 24, No. 5, pp. 373-378 (1984). One fourth of the predictions made at this time were incorrect. In an effort to address this problem many objective diagnostic methods have been proposed by previous researchers. These methods take information from the surface, as well as beneath the skin, and depend on the following criteria and procedures. One method depends on a fluorescein test for the presence of dermal circulation. Another method depends on staining reactions on the surface of the burn. Another method depends on sensitivity of the burn to pinprick. Yet another method depends on temperature variations within the burn area as evidenced by thermogram.
Although some progress has been made in laboratory testing, heretofore, no method has gained widespread clinical acceptance. The limitations of previous methods include poor burn depth predictive values on various selected days post-burn, excessive cost, cumbersome techniques, time-consuming techniques, and techniques that often include a toxic reaction.
These previous methods can be classified either as invasive or non-invasive. The invasive methods include the fluorescence test, staining appearance, and sensitivity to pinprick. The non-invasive approaches are the thermogram imaging and multispectral photographic analysis.
The fluorescence method employs a fluorometer to quantify fluorescence as a measure of burn depth. However, the fluorescein injected into the femoral vein in this method causes a toxic reaction in some patients. Green, H. A., Bua, D., Anderson, R. R. and Nishioka, N. S., “Burn Depth Estimation Using Indocyanine Green Fluorescence.”
Arch Dermatol
, vol. 128, January, pp. 43-49 (1992).
The staining reaction method introduced by Patey and Scarff maps out areas of
Fiesler Emile
Lieberman Robert A.
Lu Taiwei
Wang Allan
Hilten John S.
Intelligent Optical Systems, Inc.
Nilles & Nilles S.C.
Washburn Douglas N
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