Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-05-16
2001-10-30
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S310000, C600S473000, C600S476000
Reexamination Certificate
active
06311083
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a method for locating an examination site for conducting a diaphanoscopic examination of a living subject, as well as to an apparatus for implementing the method.
2. Description of the Prior Art
In the framework of diaphanoscopic examinations, a region of a living subject to be examined is transilluminated with light and the transillumination image that is registered is utilized for diagnosis. If one wishes to detect a pathologically induced, optical change in a specific, transilluminated volume of the life form and make the result available as the basis of the diagnosis, then the selection of an “optimum” irradiation site must assure that the pathologically modifiable tissue penetrated by the photons is maximum compared to the pathologically constant volume in order to thus be able to actually examine the region of maximum information in the scope of the main examination. This is especially important when the pathological change to be detected is small. A diaphanoscopic examination method can, for example, be implemented at a finger joint in order to make a diagnosis with regard to rheumatoid arthritis. In simplified terms, a finger joint is composed of bone tissue, cartilage tissue, skin tissue and capsular tissue as well as joint fluid. The bone tissue, cartilage tissue as well as the surrounding skin tissue thereby remain pathologically constant in the early stage; the possible pathological changes occur only in joint capsule as well as the joint fluid. In order to obtain a maximum informational content with respect to this relatively narrow diagnostic volume in the framework of the main examination, it is necessary to implement the transillumination at the optimum examination site, so that the informational content that is obtained is as great as possible. The term examination location (or examination) being a tissue location prescribable on the basis of a position value, this being illuminated by the beam crossection of the light source employed for the examination.
U.S. Pat. No. 5,452,723 discloses a spectroscopy method that is utilized in conjunction with spectroscopy of human tissue. With the method disclosed therein, the distortions of the obtained measured values are to be corrected given an examination of a thick tissue several millimeters thick due to the increased number of dispersion centers of the thick tissue compared to the spectroscopy of a very thin tissue only a few micrometers thick wherein fewer dispersion centers that influence the measured result are established. This ensues such that a spectrum of the diffuse reflectance is registered first, followed by the spectrum to be “distortion-corrected”, for example the fluorescence spectrum. An effective reflectance function is subsequently determined based on probability functions. The distortion-corrected fluorescence spectrum is then determined by dividing the registered fluorescence spectrum by the effective reflectance spectrum described on the basis of the effective reflectance function. The distortions of the spectrum of the thick tissue deriving from dispersion and absorption effects as well as the geometrical and the boundary surface conditions are eliminated, the spectrum curve that is obtained corresponds in good approximation to that of a thin tissue. The “distortion-corrected” measured curve that is obtained is subsequently compared to known reference curves, and the best fit curve is identified, this being subsequently investigated in view of the presence and concentration of reference fluorophores, which is the basis for the diagnosis of the corresponding tissue property.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method with which the optimum examination location for diaphanoscopic examinations of, for example, joints can be determined.
The above object is achieved in accordance with the principles of the present invention in a method wherein a region of the life form in which the optimum examination location is suspected is sequentially transilluminated with a radiation in, preferably, a wavelength range of the optical tissue window for registering dispersed light distributions in the form of location-related spread functions, particularly point spread functions, whereby at least one function-specific, location-related feature of every spread function is identified, a position value defining the examination location being determined based thereon.
The inventive method is based on the fact that, given a (punctiform) location-dependent transillumination of the tissue to be examined, scattered light distributions in the form of spread functions arise (point spread functions given punctiform irradiation), whose change in the form of scaling over the irradiation location are a function of the light propagation and that thus enable a statement about the optical conditions of the transilluminated, overall volume. Given knowledge of the optical properties of the tissue types present in the transilluminated volume, how the photons propagate when they penetrate mainly pathologically modifiable volume can then be determined, as can the form and scaling modification in which this is presented in the resulting scattered light distribution or, respectively, spread function. Inventively, thus, different spread functions, for example five spread functions, are registered at different irradiation locations, whereupon a function-specific, location related feature is determined on the basis of the respectively obtained spread function, i.e. a diagnostic characteristic of each function. After determining these features, these are further-processed in common and, based thereon, a position value is determined that defined the optimum examination location, i.e. based whereon the optimum examination site can be determined.
For implementation, a region of the life form that covers the (expected) optimum examination site as a sub-region is transilluminated in chronological succession at a number of locations within the region. This, for example, can ensue in equidistant steps along a line, for instance parallel to the longitudinal axis of a finger (called x-axis below). A radiation in the wavelength range of the optical tissue window is preferably employed. Upon penetration of the tissue, the incoming light, which is (approximately) punctiform, is dispersed. The spatial distribution of the scattered light is acquired with a planar or line-shaped arrangement of light detectors. The intensity of the scattered light measured in this way as function of the location of the light detectors is referred to as a scattered light distribution function or also, more specifically, as a (point) spread function. For example. Eugene Hecht, “Optik”, Addison-Wesley-Verriag, 1989, pp. 512 ff., is referenced for more detailed explanation of the term “spread function”. The shape of the course of this spread function is dependent on the composition of the transirradiated tissue and, thus, is dependent on the selected irradiation location. A separate, characteristic spread function is thus obtained for each sequentially selected irradiation location. In general, function curves can be described (“parameterization” of a function) by one or more characteristic values (function-specific parameters or features), for example maximum value of the function, location of the maximum value of the function, location of the maximum slope or curvature of the function, etc. For the method disclosed herein, at least one or a mathematical operation of a number of description parameters of the function is selected, this being characteristic of the modification of the spread function given variation of the irradiation location, particularly for the differences in the form of the spread function given transirradiation of healthy and sick tissue. These parameters for describing the function curve of the measured spread functions are referred to below as function-specific, location-related features (related to the location of irradiation)
Abraham-Fuchs Klaus
Beuthan Juergen
Mueller Gerhard-J.
Prapavat Viravuth
Lateef Marvin M.
Qaderi Runa Shah
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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