for a better understanding of the determination method described below with reference to an exemplary embodiment , the inventive apparatus for the implementation of this method , as shown , for example , in fig3 will be described first . this apparatus is composed of an irradiation unit 1 , for example in the form of a laser with a wavelength of 675 nm . a detector 3 is provided thereopposite . the region of a living subject to be examined , a finger 4 in the illustrated example , is placed between irradiation unit 1 and detector 3 . in the region of a joint to be examined , this finger 4 is composed of skin tissue 5 , cartilage and bone tissue 6 as well as joint capsule tissue 7 and joint fluid 8 . a control unit 9 controls the operation and a computer 10 determines the optimum examination location from the data obtained by the detector 3 . given this embodiment having only one radiation source 2 , the operation for determining the optimum examination location ensues such that the irradiation unit 1 together with the radiation source 2 is moved , for example , to five selected positions above the joint gap , whereby the mobility is indicated by the double arrow a . the positioning unit required for this purpose is not explicitly shown . a punctiform transillumination of the tissue then ensues at each of the selected locations . the respective scattered light distribution for each irradiation is registered with the detector 3 in the form of a point spread function and is supplied to the computer means 10 , which , on the basis of the method described below , determines the optimum examination site and supplies a signal indicating this site to the control unit 9 , which then causes the irradiation unit 1 to be driven and moved for the implementation of the actual examination , as already described , the scattered light distribution is registered for each of the predetermined irradiation locations around a defined zero position . such scattered light distributions are shown in fig1 wherein the location in mm around the zero position is indicated along the abscissa and the normalized irradiation intensity is indicated in 1 / cm 2 along the ordinate . the arrows respectively indicate the irradiation location for the respective curves . the irradiation locations shown here lie distributed ± 2 millimeters around the zero location , i . e . a total of five irradiation locations were selected . the respectively obtained scattered light distribution for each of the irradiation locations x − 2 . . . x 2 is indicated with the reference characters k − 2 . . . k 2 . as can be derived from fig1 the course of the curve is still relatively noise - infested and allows only an inexact determination of the optimum examination location . to this end , an approximation curve a + 2 . . . a + 2 is determined for each of the curves k − 2 . . . k + 2 by approximation with a number of gaussian functions . these approximation curves are shown in fig2 . moreover , the respective centers of gravity s − 2 . . . s + 2 of the curves are also determined for each curve a 2 . . . a 2 . the centers of gravity are not utilized for the determination of examination sites described below ; however , the determination method could likewise be implemented based on these values . a series of function - specific , location - related features are then determined for determining the optimum examination location , as can be derived from the following table . the x - values of the respective curve maximums e max are first determined on the basis of the approximation functions . as can be derived from line 2 of the table , these respectively lie in the negative range . it is already possible to calculate a first examination location from these values by averaging . this would lie at x average = 1 . 12 mm . for taking the actual amount of the scattered light distributions into consideration , it is expedient to determine a weighting factor and to take it into consideration in the formation of the average . certain properties of the scattered light distribution such as the overall irradiation intensity e gea (= area under the respective curve ) and the standard deviation (= width of the curve ) are available for calculating this weighting factor . the values therefor determined with respect to the approximation function can be derived from lines 3 and 4 . based thereon , it is possible to multiplicatively determine a weighting factor from these two values , whereby the values are recited in line 5 . subsequently , the identified weighting factor is normalized to the highest weighting factor ( line 6 ). when the identified x - values of e max ( column 2 ) are now multiplied by the normalized weighting factors , then the weighted x - values of e max are obtained , as indicated in line 7 . the weighted average that can be calculated from these weighted values amounts to x average = 1 . 004 mm and takes the respective amount of the individual scattered light distributions into account . compared to the position value calculated unweighted , a difference of 0 . 116 mm thus derives . subsequently , the weighted average that specifies the optimum location at the detector side must be back - transformed onto a coordinate of the excitation side . to this end , the offset between the irradiation location that supplies the highest weighting factor , or the highest e ges , and the position of e max of this scattered light distribution is employed in the illustrated exemplary embodiment , the irradiation position that supplies the scattered light distribution with the highest weighting factor is the irradiation location x 1 . the e max - position of this scattered light distribution is x emax = 1 . 4 mm . an offset of x 1 = x emax = 1 mm −(− 1 . 4 mm ) + 0 . 4 mm derives therefrom . for back - transformation , the calculated , weighted average of 1 . 004 mm is shifted by this offset , so that the new zero position in the irradiation plane is selected as x optimum = 0 . 604 mm . instead of employing the x - values of e max , the disclosed determination method can be implemented in the same way based on the centers of gravity of the respective approximation functions . finally , fig4 shows a further embodiment of an inventive apparatus . the structure is largely the same as shown in fig3 ; however , an irradiation unit 11 is employed in this embodiment that contains a number of radiation sources 12 . the radiation sources 12 are spaced from one another grid - like , whereby a grid of 500 μm or less , preferably 250 μm , is employed . in the illustrated exemplary embodiment , only seven radiation sources are indicated for clarity ; the number , of course , is substantially greater in view of the selected grid spacing . the operation of this apparatus is such that , for example , only every other radiation source 12 is driven , whereby , of course , only those are driven that are in a correspondingly close position to the suspected , optimum examination site . after determining the optimum examination site , a radiation source 12 that is more beneficial because it lies closer to the examination location can then be driven via the control unit 9 , which is also present in this embodiment . such an operation is possible given an adequately small spacing , for example 250 μm , insofar as a larger grid spacing is selected ( for example , 500 μm ), it is likewise conceivable to provide for positioning of the irradiation unit 11 in order to move a selected radiation source to the optimum examination location . although modifications and changes may be suggested by those skilled in the art , it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art .
in a method and an apparatus for locating an examination size for diaphanoscopic examination of a living subject , a region of the living subject wherein the optimum examination location is suspected is sequentially transilluminated with radiation , preferably in a wavelength range of the optical tissue window , for registration of scattered light distributions in the form of location - related spread functions , particularly point spread functions , and at least one function - specific , location - related feature of each spread function is determined , based on which a position value defining the examination location is determined .