Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
1999-03-19
2001-01-16
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S475000, C600S477000, C250S252100, C356S243100
Reexamination Certificate
active
06175750
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to reflected light analysis. More particularly, the present invention is related to calibration of a reflection imaging spectrophotometer.
2. Related Art
Quantitative spectrophotometry requires a means for calibrating the detection subsystem of the spectrophotometer and for verification of the calibration. One approach to calibration involves the insertion of two or more standards of known reflectance in the measurement path and measuring the resultant detected signals from each. These standards may include, for example, a blank (i.e., a standard with zero absorption and full reflectance) plus one or more standards having other known optical densities.
Such an approach is complicated by the fact that the nature of the reflecting surface may influence the result. Thus, a standard reflecting surface is typically needed in addition to the optical density calibration standards themselves. Transfer of calibration from one reflecting surface to another, however, is not generally possible. A reflection imaging spectrophotometer that is calibrated with respect to one reflecting surface will not necessarily be calibrated correctly with respect to another reflecting surface. Hence a reflection imaging spectrophotometer that is calibrated with respect to some standard reflecting surface will not necessarily be calibrated correctly with respect to an actual subject. Moreover, control of the reflecting surface is not possible when performing reflection imaging spectrophotometry of living human tissue. A method is therefore needed to provide standards for calibration of reflection imaging spectrophotometers intended for such applications.
SUMMARY OF THE INVENTION
The invention comprises a system and method for calibrating a reflected spectral imaging apparatus, such as a reflection imaging spectrophotometer, used for analysis of living tissue. In addition to the reflected spectral imaging apparatus itself, the calibration apparatus includes an optical filter that is placed between the light source used in the imaging apparatus and the object under analysis, and a calibration module. The filter is fabricated such that when the light is passed through the filter, an image is projected onto the focal plane where imaging is to take place within the object. The image projected by the filter comprises a plurality of areas, each having a different known optical density. For each area, the calibration module measures the intensity of the light reflected from the area. The calibration module then maps the area's light intensity measurement to the optical density known to be present at the area. This correspondence of multiple light intensity measurements with known optical densities is used to calibrate the reflected spectral imaging apparatus.
FEATURES AND ADVANTAGES
It is a feature of the present invention that it provides for calibration of a reflection imaging spectrophotometer in a manner that takes into account the nature of the reflecting surface of the specific object being imaged. Hence calibration of the spectrophotometer, when performed according to the invention, is adapted to the object being imaged.
Because the calibration takes into account the nature of the reflecting surface of the specific object being imaged, it is an advantage of the invention that the calibration is adaptable to subsequent objects that may be imaged. The invention permits ready recalibration of the spectrophotometer.
It is a further advantage of the invention that calibration of the spectrophotometer is performed in a non-invasive manner with respect to the object being imaged. As a consequence, the object being imaged suffers no damage during the calibration process.
Because the calibration is non-invasive, it is a further advantage of the invention that, when imaging human tissue in vivo, no discomfort is caused in the patient by the calibration process.
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Cook Christopher A.
Groner Warren
Nadeau Richard G.
Cytometrics, Inc.
Sterne Kessler Goldstein & Fox P.L.L.C.
Winakur Eric F.
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