Source: https://patents.google.com/patent/EP1207385B1/en
Timestamp: 2019-12-07 05:04:05
Document Index: 256241948

Matched Legal Cases: ['art 80', 'art 80', 'art 80', 'art 80', 'art 80', 'art 80', 'art 80', 'art 80']

EP1207385B1 - Optical ct device and method of image reformation - Google Patents
Optical ct device and method of image reformation Download PDF
EP1207385B1
EP1207385B1 EP99923877A EP99923877A EP1207385B1 EP 1207385 B1 EP1207385 B1 EP 1207385B1 EP 99923877 A EP99923877 A EP 99923877A EP 99923877 A EP99923877 A EP 99923877A EP 1207385 B1 EP1207385 B1 EP 1207385B1
EP99923877A
EP1207385A1 (en
EP1207385A4 (en
1999-06-03 Application filed by Hamamatsu Photonics KK filed Critical Hamamatsu Photonics KK
1999-06-03 Priority to PCT/JP1999/002960 priority Critical patent/WO2000075633A1/en
1999-06-03 Priority claimed from EP05020359.5A external-priority patent/EP1609410B1/en
2002-05-22 Publication of EP1207385A1 publication Critical patent/EP1207385A1/en
2004-11-24 Publication of EP1207385A4 publication Critical patent/EP1207385A4/en
2011-02-09 Publication of EP1207385B1 publication Critical patent/EP1207385B1/en
An optical CT device (10) chiefly comprises a container (12) filled with optical interface material (20), a projector including a light source (22) and an optical switch (24) to project light into the container (12), a photodetector including a photodetector element (30) and a shutter (32) to detect the light through the container (12), and a processor/controller (14) for computing the spatial distribution of an absorption coefficient. The processor/controller (14) determines the spatial distribution of the quantity of feature concerning an optical characteristic of an object (200) for measurement based on the comparison between the light intensity signal from the detector (30) with the container (10) filled with the optical interface material (20) and such a signal from the detector (30) with the optical interface material (20) replaced in part by the object (200) for measurement.
DESCRIPTION Optical CT Apparatus and Image Reconstructing Method Technical Field
Known as an example of image reconstructing methods is the following one by R.L. Barbour et al ("Imaging of Multiple Targets in Dense Scattering Media" (H.L. Graber, J. Chang, R.L. Barbour, SPIE Vol. 2570, p. 219 - p. 234)). Namely, this is a method in which light beams are projected from a plurality of locations on a surface of a part of an object to be measured toward the inside of the part of object to be measured and, from the optical path length calculated in each of volume elements into which the part of object to be measured is divided, the absorption material concentration of each volume element is determined. Here, it is necessary to use another phantom having an outer shape identical to that of the part of object to be measured but with no absorption therein, so as to measure a standard value of the detection intensity (transmission light intensity).
On the other hand, Japanese Patent Application Laid-Open No. HEI 6-129984 discloses that a medium (hereinafter referred to as optical interface member) having a refractive index and a scattering coefficient which are substantially the same as those of the part of object to be measured is interposed between the light-projecting section and the part of obj ect to be measured, so as to prevent light from being reflected, scattered, and so forth on the surface of the part of object to be measured, thereby raising the accuracy in measurement.
WO 99/26526 describes a method and device for localizing an object in a turbid medium. The method can be used in optical mammography during which a part of a breast of a female body is examined by means of light. To this end, the part of the breast is introduced into a holder of the device, said holder being provided with light sources and detectors. In order to realize an optical coupling between the light sources and the detectors and the breast, a calibration medium is introduced. After measurement of the intensities for a plurality of light paths between the light sources and the detectors, the measured intensity is normalized. In order to counteract artefacts which are caused by deviations of the optical properties of the calibration medium and the mean optical properties of the part of the breast, the measured intensities are corrected prior to the reconstruction of the interior of the breast. The corrected intensity for a light path to be selected between a light source and a detector is determined by a combination of a normalized intensity of the selected light path, the normalized intensities, lengths of the light paths, and a length of the selected light path.
However, the above-mentioned image reconstructing method and the optical CT apparatus using the above-mentioned image reconstructing method have problems as follows.
For overcoming the above-mentioned problems, there is provided an apparatus and method in accordance with the independent claims.
Fig. 1 is a system diagram of the optical CT apparatus in accordance with an embodiment of the present invention;
The optical CT apparatus in accordance with an embodiment of the present invention will be explained with reference to the drawings. First, the configuration of the optical CT apparatus in accordance with the embodiment of the present invention will be explained. Fig. 1 is a system diagram of the optical CT apparatus in accordance with the embodiment of the present invention, Fig. 2 is a view showing a state where the optical CT apparatus in accordance with the embodiment of the present invention is used, and Fig. 3 is a diagram of the optical CT apparatus in accordance with the embodiment of the present invention about its container. The optical CT apparatus 10 is mainly composed of a container 12 for accommodating a part of an object to be measured 200, a light-projecting section for projecting light into the container 12, a light-detecting section for detecting the light projected by the light-projecting section, and an arithmetic/control section 14 for calculating a spatial distribution of an absorption coefficient of the part of object to be measured 200 from the quantity of light detected by the light-detecting section.
The container 12 is filled with an optical interface member 20. The optical interface member 20 is a material which fills the gap between the part of object to be measured 200 and the container 12, thereby acting to reduce the discontinuity of an optical characteristic in the surface of the part of object to be measured 200. Specifically, it refers to a medium having at least one characteristic selected from optical characteristics such as absorption coefficient, scattering coefficient, refractive index, optical rotation, and polarization degree is made substantially identical to the average value of absorption coefficient, average value of scattering coefficient, average value of refractive index, average value of optical rotation, average value of polarization degree, or the like in the part of object to be measured 200 . Employed in the case where the part of object to be measured 200 is a human body is, for example, a medium whose optical characteristics are caused to match those of the part of object to be measured 200 by dissolving silica, Intralipid (fat emulsion), or the like for attaining the desirable scattering coefficient, ink or the like having a particular absorption coefficient at a specific wavelength for attaining the desirable absorption coefficient, glucose, fructose, or the like for attaining the desirable optical rotation and polarization degree into water having a refractive index substantially identical to that of the human body. Here, "substantially identical" refers to the cases where they are identical or can be regarded as identical from the viewpoint of measurement accuracy or the like.
The arithmetic/control section 14 has a function of determining a spatial distribution of the absorption coefficient of the part of obj ect to be measured 200 according to a comparison of the optical intensity signal actually measured by each detector 30 in the state where the container 12 is filled with the optical interface member 20 with the optical intensity signal actually measured by each detector 30 in the state where the optical interface member 20 is partly replaced by the part of object to be measured 200. Namely, the arithmetic/control section 14 comprises a first arithmetic section 14a for assuming the inside of the container 12 to be an assembly model divided into a plurality of volume elements and calculating a degree of influence of a change in a characteristic amount concerning an optical characteristic of each volume element upon a characteristic amount concerning an optical characteristic of transmitted light detected by the light-detecting section in the case where the light-projecting section and light-detecting section are used; a second arithmetic section 14b for calculating an amount obtained when an optical amount concerning an optical characteristic of the light transmitted through the optical interface member 20 actually measured by use of the light-projecting section and light-detecting section in the state where the optical interface member 20 is accommodated within the container 12 and an optical amount concerning an optical characteristic of the light transmitted through the optical interface member 20 and/or the part of object to be measured 200 actually measured by use of the light-projecting section and light-detecting section in the state where the optical interface member 20 is partly replaced by the part of object to be measured 200 are compared with each other; and a third arithmetic section 14c for calculating a spatial distribution of a characteristic amount concerning an optical characteristic of the part of obj ect to be measured 200 by calculating a characteristic amount concerning an optical characteristic of each volume element from the degree of influence determined by the first arithmetic section 14a and the amount obtained by the second arithmetic section 14b from the comparison of the characteristic amounts concerning optical characteristics. More specific algorithms will be mentioned in detail in the image reconstructing method, which will be explained later. The arithmetic/control section 14 also has a function of controlling the emission of the light source, actions of the optical switches 24, and opening/closing of the shutters 32.
The basic principle of the image reconstructing method in accordance with this embodiment will now be explained. Fig. 4 is a chart showing how light is transmitted through a medium having a uniform absorption coefficient, whereas Fig. 5 is a chart showing how light is transmitted through a medium having a nonuniform absorption coefficient. For simplification, a medium which is a scattering absorber is assumed to be a two-dimensionally expanding square and is divided into N (= 25) square volume elements (which are area elements to be exact since they are two-dimensional) having the same size. It is assumed that the absorption coefficient is constant within each volume element whereas the absorption coefficient of the volume elements marked with hatches and the like is different from that of the other volume elements.
In the case where light is projected from a point of a medium having a uniform absorption coefficient (the absorption coefficient being µa) into the medium whereas the output light is detected at one point as shown in Fig. 4, the detection intensity S is expressed by: S = D sr ⋅ I ⋅ exp - μ a ⁢ W 1 + W 2 + ⋅ ⋅ ⋅ ⋅ ⋅ ⋅ + W N
where I is the incident intensity, Wj (j = 1 to N) is the degree of influence of each volume element, and Dsr is the attenuation constant indicating the ratio by which the incident light is let out of the medium upon scattering, reflection, and the like. Here, the degree of influence of each volume element refers to the ratio by which the detection intensity is changed when the absorption coefficient of each volume element changes in the case where light is projected from a certain point and then is detected at a certain point, whereas a specific method of calculating the same will be explained later.
The absorption coefficient of each volume element of a medium having different absorption coefficients µaj (j = 1 to N) in the respective volume elements as shown in Fig. 5 is expressed by: μ aj = μ a + Δ ⁢ μ aj j = 1 , 2 , ⋯ , N
where µa is a reference absorption coefficient, and Δµaj (j = 1 to N) is the change of the absorption coefficient of each volume element from µa. Assuming that the attenuation constant Dsr is unchanged from that in the case where the absorption coefficient is constant, the detection intensity O in this case is expressed as: O = D sr ⋅ I ⋅ exp - W 1 ⁢ μ a + Δ ⁢ μ a ⁢ 1 + W 2 ⁢ μ a + Δ ⁢ μ a ⁢ 2 + ⋯ + W N ⁢ μ a + Δ ⁢ μ aN = S ⋅ exp - W 1 ⁢ Δ ⁢ μ a ⁢ 1 + W 2 ⁢ Δ ⁢ μ a ⁢ 2 + ⋯ + W N ⁢ Δ ⁢ μ aN
Therefore, by taking logarithms of both sides of expression (3), the following expression is obtained: ln S - ln O = W 1 ⁢ Δ ⁢ μ a ⁢ 1 + W 2 ⁢ Δ ⁢ μ a ⁢ 2 + ⋯ + W N ⁢ Δ ⁢ μ aN = ∑ j = 1 N W j ⁢ Δ ⁢ μ aj
Here, expression (4) becomes a functionof the detection intensity S (hereinafter referred to as reference intensity S) of light projected from one point of the medium having a uniform absorption coefficient and outputted to one point, the detection intensity O (hereinafter referred to as measurement intensity O) of light projected from one point of the medium having a nonuniform absorption coefficient and outputted to one point, the degree of influence Wj (j = 1 to N) within each volume element, and the change Δµaj (j = 1 to N) of the absorption coefficient of each volume element from µa. Among these variables, the reference intensity S and the measurement intensity O are obtained by measurement, whereas the degree of influence Wj (j = 1 to N) is obtained by a calculation (details of which will be explained later), whereby only N pieces of the change Δµaj (j = 1 to N) of the respective absorption coefficients of volume elements from µa are left as unknown quantities. Therefore, when N pieces of equations each represented by expression (4) are simultaneously formed concerning different sets of light-projecting points/light-detecting points, N pieces of Δµaj can be determined, which makes it possible to calculate the spatial distribution of the absorption coefficient of the medium.
Specifically, assuming Si to be the reference intensity in the i-th (i = 1 to N) set of light-projecting point/light-detectingpoint, Oi tobe the detection intensity, and Wij (j = 1 to N) to be the degree of influence of each volume element, expression (4) is represented as indicated by expression (5): ln S i - ln O i = ∑ j = 1 N W ij ⁢ Δ ⁢ μ aj
Here, expressions (5) for all instances of i are arranged
and represented in the form of matrix as: ln S 1 - ln O 1 ln S 2 - ln O 2 ⋮ ⋮ ln S N - ln O N = W 11 W 12 ⋯ ⋯ W 1 ⁢ N W 21 W 22 ⋮ ⋮ ⋱ ⋮ ⋮ ⋱ ⋮ W N ⁢ 1 ⋯ ⋯ ⋯ W NN ⁢ Δ ⁢ μ a ⁢ 1 Δ ⁢ μ a ⁢ 2 ⋮ ⋮ Δ ⁢ μ aN
Therefore, n pieces of Δµaj, i.e., the spatial distribution of absorption coefficient of the medium, can be determined as indicated by expression (7): Δ ⁢ μ a ⁢ 1 Δ ⁢ μ a ⁢ 2 ⋮ ⋮ Δ ⁢ μ aN = W 11 W 12 ⋯ ⋯ W 1 ⁢ N W 21 W 22 ⋮ ⋮ ⋱ ⋮ ⋮ ⋱ ⋮ W N ⁢ 1 ⋯ ⋯ ⋯ W NN - 1 ⁢ ln S 1 - ln O 1 ln S 2 - ln O 2 ⋮ ⋮ ln S N - ln O N
Here, how to determine the degree of influence Wij (j = 1 to N) of each volume element will be explained. The steady-state light diffusing equation of continuous light (luminous flux) incident on each volume element is: ΔΦ - μ a ⁢ D - 1 ⁢ Φ = 0
µa is the optical absorption coefficient of each volume element;
µs' is the optical isotropic scattering coefficient of each volume element; and
D is the diffusion coefficient of each volume element D = 1 3 ⁢ μ s ʹ .
The boundary condition between the inside and outside of the medium is:
Φ BL = 0 (9)
Here, the suffix BL indicates the boundary between the inside and outside of the medium. Also, expression (9) is equivalent to such a condition that light is completely absorbed by this boundary, e.g., a state where the surroundings of the medium are painted pitch-black.
Using expressions (8) and (9), a light transmission simulation (hereinafter referred to as first simulation) is carried out with respect to each set of light-projecting point/light-detecting point, i.e., the i-th (i = 1 to N) set of light-projecting point/light-detecting point, whereby the detection light intensity is calculated. In the first simulation, however, the medium is assumed to have a constant absorption coefficient µa, complete diffusion is assumed in the above-mentioned expression (8), and the size of the container 12 is greater than 1/µs'. The detection intensity in the i-th (i = 1 to N) set of light-projecting point/light-detecting point obtained by the first simulation is assumed to be di0.
Subsequently, using expressions (8) and (9), a second simulation is carried out. In the second simulation, assuming that one volume element of the medium has an absorption coefficient µa+ Δµa which is different from the absorption coefficient µa, a light transmission simulation is carried out with respect to each set of light-projecting point/light-detecting point. For example, it is assumed that Δµa = 0.01 mm-1. Under this condition, the detection light intensity is calculated. The detection intensity in the case where the absorption coefficient of the j-th (j = 1 to N) volume element is changed with respect to the i-th (i = 1 to N) set of light-projecting point/light-detecting point is assumed to be dij.
Using the detection light quantities calculated by the first and second simulations, the degree of influence Wij of each volume element is represented as indicated by expression (10): Wij = μ a - 1 ⁢ ln d i ⁢ 0 / d ij
Consequently, Wij is determined from expression (10), whereby the spatial distribution of absorption coefficient is calculated from expression (7).
After the inner space of the container 12 is divided into volume elements, actual measurement is carried out. The container 12 is filled with the optical interface member 20 having a known absorption coefficient µa, whereas the opening portion of the container 12 is blocked with the light-shielding plate 18 in order to prevent light from entering from parts other than the light-projecting/detecting ports 16. In this state, the light emitted from the light source 22 is projected into the container 12 individually and exclusively from the light-projecting/detecting ports 16a to 16h upon switching the optical switch 24. The emission of the projection light in the light source 22 and the switching of the optical switch 24 are controlled by the arithmetic/control section 14.
The light projected into the container 12 is guided to the photodetectors 30 from the light-proj ecting/detecting ports 16, whereby the respective light quantities incident on the light-projecting/detecting ports 16a to 16h are detected individually and exclusively. Here, when the intensity of detection light incident on the light-projecting/detecting ports 16 at positions for projecting light is remarkably high, it is preferable to close the shutters 32 at the corresponding positions in order to protect the photodetectors 30.
When 8 pieces of light-projecting/detecting ports 16a to 16h are provided as shown in Fig. 3,8 x 8 = 64 ways of combinations are possible as sets of light-projecting points/light-detecting points. However, measured values cannot be obtained when the incident detection light intensity becomes remarkably high in combinations in which a projecting port and a detecting port are located at the same position (e.g., a combination in which light is projected from the light-projecting/detecting port 16a and is detected by the same light-projecting/detecting port 16a), since the shutter 32 is closed because of the reason mentioned above. In a pair of combinations in which projecting ports and detecting ports are positioned opposite from each other (e.g., a combination in which light is projected from the light-projecting/detecting port 16a and is detected at the light-projecting/detecting port 16e, and a combination in which light is projected from the light-projecting/detecting port 16e and is detected at the light-projecting/detecting port 16a), one of them is excluded since they yield the same data. In general, one of them may be excluded when such an optical reciprocity theorem holds, whereas they are treated as different data when the optical reciprocity theorem does not hold.
In the second measurement step, the measurement intensity O is measured. The measuring method is basically the same as the above-mentioned measurement of the reference intensity S, whereby the detection intensity is measured with respect to the sets of light-projecting
points/light-detecting points selected at the time of measuring the reference intensity S. At the time of measuring the measurement intensity O, however, the measurement is carried out while the optical interface member 20 accommodated within the container 12 is partly replaced by the part of object to be measured 200. When the measurement is carried out, the detection intensity in the i-th set is A/D-converted by the signal processing circuit 36, so as to be fed as the measurement intensity Oi into the arithmetic/control section 14 and stored in the recording/display section 38.
The human breast, which is the part of object to be measured 200, is accommodated within the container 12 as shown in Fig. 2. Though the whole opening portion of the container 12 cannot be covered with the shielding plate 18 in this case, the gap between the part of obj ect to be measured 200 and the fringe part of the opening portion of the container 12 can be covered with the shielding plate 18 when necessary.
The first arithmetic step is a step of calculating the degree of influence Wij of the j-th volume element in the i-th set of light-projecting point/light-detecting point. The specific method of calculating Wij is as already explained. This calculation determines an N x N matrix of degree of influence [W] as indicated by expression (11): W = W 11 W 12 ⋯ ⋯ W 1 ⁢ N W 21 W 22 ⋮ ⋮ ⋱ ⋮ ⋮ ⋱ ⋮ W N ⁢ 1 ⋯ ⋯ ⋯ W NN
In the second arithmetic step, an amount obtained from the comparison between the reference intensity Si and measurement intensity Oi in the i-th set of light-projecting point/light-detecting point is calculated. Specifically, as this amount of comparison, the difference between the natural logarithm of the reference intensity Si and the natural logarithm of the measurement intensity Oi is calculated for each set of light-projecting point/light-detecting point, whereby an N x 1 measurement matrix [SO] shown in expression (12) is determined: SO = ln S 1 - ln O 1 ln S 2 - ln O 2 ⋮ ⋮ ln S N - ln O N
In the third arithmetic step, using expression (7), the absorption coefficient of each volume element is calculated from the matrix of degree of influence [W] calculated in the first arithmetic step and the measurement matrix [SO] calculated in the second arithmetic step. Here, the amount determined from expression (7) is the amount of change from the reference absorption coefficient µa to be exact, whereas the absorption coefficient µa of the optical interface member 20 is known, whereby the absolute value of absorption coefficient can easily be obtained.
Though an analyzing method in the case where continuous light is used as projection light is explained in the above-mentioned embodiment, methods described in "performance of an iterative reconstruction algorithm for near infrared absorption and scatter imaging" (S.R. Arridge, M. Schweiger, M. Hiraoka, D.T. Delpy, SPIE Vol. 1888, p. 360 - p. 371) and "Forward and Inverse Calculations for 3-D Frequency-Domain Diffuse Optical Tomography" (Brain W. Pogue, Michael S. Patterson and Tom J. Farrell, SPIE Vol. 2389, p. 328- p. 339), for example, may also be used with respect to cases utilizing an analyzing method for determining the moment of a time-resolved waveform obtained by time-resolved spectroscopy (TRS) employing pulsed light and an analysis method of phase difference method (PMS) employing phase-modulated light.
Modified examples of the container used in the optical CT apparatus in accordance with this embodiment will now be explained. Fig. 7 shows a first modified example of the container. The container 50 is one which can reduce the pressure therewithin. The container 50 contains the optical interface member 20 therein, and has such an opening portion that the part of object to be measured 200 can be introduced therethrough. The bottom part of the container 50 is formed with a suction port 50a for drawing the optical interface member 20 to the outside, whereas a valve 52, a pump 54, and a reservoir 56 are provided by way of a pipe. Also, the container 50 is provided with a pressure gauge 58 for measuring the pressure of the optical interface member 20 within the container 50.
Fig. 11 shows a fifth example of the container. The container of this modified example is used when measuring diffused reflected light on the same plane as the entrance surface, for example, as in the measurement of abdomen. The container 80 is constituted by a first part 80a having a columnar form with only one bottom face opened whereas the other bottom face is provided with
light-projecting/detecting optical fibers 82, a second part 80b having a columnar form with both bottom faces opened while having a height identical to the inner depth of the part of object to be measured 200, and a light-shielding plate 80c.
When measuring the reference intensity S by use of the container 80, the measurement is carried out in a state where the opening portion of the first part 80a and one opening portion of the second part 80b are connected to each other, the optical interface member 20 is introduced into the first part 80a and second part 80b, and the other opening portion of the second part 80b is closed with the light-shielding plate 80c.
When measuring the measurement intensity O, on the other hand, the measurement is carried out in a state where the optical interface member 20 is introduced into the first part 80a while the opening portion thereof is in contact with the surface of the part of object to be measured 200 as shown in Fig. 12.
Fig. 14 shows a seventh modified example of the container. The container of this modified example is one which can remove the optical interface member 20 attached to the inside of the container after the measurement. A pump 98 and a detergent tank 100 are connected to this container 94 by way of a valve 96, whereby a detergent can be supplied from a detergent injection port 94a into the container 94. Also, a liquid tank 102 storing washing water therewithin is provided, so that the washing water can be supplied into the container 94 and wash the inside of the container 94 and the part of object to be measured 200. Further, the side wall of the container 94 is provided with a fan 104, so that the inside of the container 94 and the part of object to be measured 200 can be dried.
Figs. 15A and 15B show an eighth modified example of the container. The container of this modified example is used in a case where a forearm part is measured, for example. This container 106 is constituted by an undeformable cylindrical container outer wall 106a (see Fig. 15A) made of a light-shielding material, and a plurality of deformable bags 106b (see Fig. 15B) made of a transparent material. A tube 108 is connected to each bag 106b, so that the latter is connected by way of a valve 110 to a pump 112 and a reservoir 114 storing the optical interface member 20. Also, a pressure gauge 116 for measuring the pressure within the bag 106b is provided.
When the container 106 is used, the valve 110 is opened in a state where the part of object to be measured 200 such as the forearm part is inserted in the container 106, and the optical interface member 20 is injected from the reservoir 114 into each bag 106b by use of the pump 112 to such an extent that the gap between the container outer wall 106a and the part of object to be measured 200 is filled therewith. The pressure gauge 116 makes it possible to monitor whether an excessive pressure which may damage the part of object to be measured 200 is exerted thereon or not at the time of injecting the optical interface member 20, and monitor whether the internal pressure of the optical interface member 20 is kept uniform or not at the time of measurement.
The optical CT apparatus or image reconstructing method of the present invention can be utilized in fields of clinical image diagnosing apparatus and the like.
An optical CT apparatus comprising:
a container (12) accommodating a light-transparent medium (20) therein;
light-projecting means for projecting pulsed light into said container;
light-detecting means for detecting said light projected by said light-projecting means into said container; and
arithmetic means (14) for calculating a spatial distribution of a characteristic of a part of an object to be measured based on a comparison of an optical characteristic of detected light transmitted through said medium and of detected light transmitted through said medium and/or said part of the object to be measured actually measured when said medium is partly replaced by said part of the object to be measured;
wherein said medium (20) has an absorption coefficient substantially identical to an average value of absorption coefficient of said part of object to be measured; and
wherein said medium (20) has a scattering coefficient substantially identical to an average value of scattering coefficient of said part of object to be measured; and
wherein said optical CT apparatus is adapted to utilize an analyzing method for determining the moment of a time-resolved waveform obtained by time-resolved spectroscopy (TRS) with said pulsed light.
An optical CT apparatus according to claim 1, wherein said arithmetic means (14) comprises:
first arithmetic means (14a) for assuming the inside of said container (12) to be divided into a plurality of volume elements, and for calculating a degree of influence of a change in an optical characteristic in each volume element upon an optical characteristic of said detected light;
second arithmetic means (14b) for calculating an amount obtained when an optical amount concerning an optical characteristic of light transmitted through said medium (20) and of light transmitted through said medium and/or said part of the object to be measured when said medium is partly replaced by said part of the object to be measured are compared with each other; and
third arithmetic means (14c) for calculating a spatial distribution of an optical characteristic of said part of the object to be measured by calculating an opticalcharacteristic of each of said volume elements on the basis of said degree of influence determined by said first arithmetic means and said calculation by said second arithmetic means.
An optical CT apparatus according to claim 1 or 2, wherein said characteristic amount concerning said optical characteristic of said transmitted light is an optical intensity of said transmitted light.
An optical CT apparatus according to one of claims 1 to 3, wherein said characteristic amount concerning said optical characteristic of said part of object to be measured is an absorption coefficient of said part of object to be measured.
An optical CT apparatus according to one of claims 1 to 4, wherein said medium (20) has an optical characteristic substantially identical to an average value of said optical characteristic of said part of object to be measured.
An optical CT apparatus according to one of claims 1 to 5, wherein said medium (20) has a refractive index substantially identical to an average value of refractive index of said part of object to be measured.
An optical CT apparatus according to one of claims 1 to 6, wherein said medium (20) has an optical rotation substantially identical to an average value of optical rotation of said part of object to be measured.
An optical CT apparatus according to one of claims 1 to 7, wherein said medium (20) has a polarization degree substantially identical to an average value of polarization degree of said part of object to be measured.
An optical CT apparatus according to one of claims 1 to 8, further comprising light-shielding means (18), provided in an opening portion of said container (12), for blocking light from the outside.
An optical CT apparatus according to one of claims 1 to 9, further comprising pressure reducing means for reducing a pressure within said container (12).
An image reconstructing method comprising:
a first measurement step of projecting pulsed light from at least one part of a container accommodating a light-transparent medium therein into said container by using light-projecting means, and
detecting said light projected by said light-projecting means in at least one part of said container by using light-detecting means,
so as to obtain a characteristic amount concerning an optical characteristic of said light transmitted through said medium;
a second measurement step of projecting pulsed light from at least one part of said container into said container by using said light-projecting means in a state where said medium accommodated within said container is partly replaced by a part of an object to be measured, and
detecting said light projected by said light-projecting means in at least one part of the container by using said light-detecting means,
so as to obtain a characteristic amount concerning an optical characteristic of said light transmitted through said medium and/or said part of object to be measured; and
an arithmetic step of calculating a spatial distribution of a characteristic amount concerning an optical characteristic of said part of object to be measured by calculating a characteristic amount concerning an optical characteristic of each said volume element according to a comparison of said characteristic amount concerning said optical characteristic of said transmitted light obtained by said first measurement step with said characteristic amount concerning said optical characteristic obtained by said second measurement step;
wherein said medium has an absorption coefficient substantially identical to an average value of absorption coefficient of said part of object to be measured;
wherein said medium has a scattering coefficient substantially identical to an average value of scattering coefficient of said part of object to be measured; and
a further step of utilizing an analyzing method for determining the moment of a time-resolved waveform obtained by time-resolved spectroscopy (TRS) with said pulsed light.
An image reconstructing method according to claim 11, wherein said arithmetic step comprises:
a first arithmetic step of assuming the inside of said container to be an assembly model divided into a plurality of volume elements and calculating a degree of influence of a change in a characteristic amount concerning an optical characteristic of each volume element upon a characteristic amount concerning an optical characteristic of said transmitted light detected by said light-detecting means in a case where said light-projecting means and said light-detecting means are used;
a second arithmetic step of calculating an amount obtained when an optical amount concerning an optical characteristic of said light transmitted through said medium actually measured by use of said light-projecting means and said light-detecting means in a state where said medium is accommodated within said container and an optical amount concerning an optical characteristic of said light transmitted through said medium and/or said part of object to be measured actually measured by use of said light-projecting means and said light-detecting means in a state where said medium is partly replaced by said part of object to be measured are compared with each other; and
a third arithmetic step of calculating a spatial distribution of a characteristic amount concerning an optical characteristic of said part of object to be measured by calculating a characteristic amount concerning an optical characteristic of each said volume element from said degree of influence determined by said first arithmetic step and said amount obtained by said second arithmetic step from said comparison of said characteristic amounts concerning optical characteristics.
An image reconstructing method according to claim 11 or 12, wherein said characteristic amount concerning said optical characteristic of said transmitted light is an optical intensity of said transmitted light.
An image reconstructing method according to one of claims 11 to 13, wherein said characteristic amount concerning said optical characteristic of said transmitted light is an absorption coefficient of said part of object to be measured.
An image reconstructing method according to one of claims 11 to 14, wherein said medium has an optical characteristic substantially identical to an average value of optical characteristic of said part of object to be measured.
An image reconstructing method according to one of claims 11 to 15, wherein said medium has a refractive index substantially identical to an average value of refractive index of said part of object to be measured.
An image reconstructing method according to one of claims 11 to 16, wherein said medium has an optical rotation substantially identical to an average value of optical rotation of said part of object to be measured
An image reconstructing method according to one of claims 11 to 17, wherein said medium has a polarization degree substantially identical to an average value of polarization degree of said part of object to be measured.
EP99923877A 1997-12-12 1999-06-03 Optical ct device and method of image reformation Expired - Lifetime EP1207385B1 (en)
PCT/JP1999/002960 WO2000075633A1 (en) 1997-12-12 1999-06-03 Optical ct device and method of image reformation
EP05020359.5A EP1609410B1 (en) 1999-06-03 1999-06-03 Optical CT apparatus
EP05020359.5A Division EP1609410B1 (en) 1999-06-03 1999-06-03 Optical CT apparatus
EP05020359.5 Division-Into 2005-09-19
EP1207385A1 EP1207385A1 (en) 2002-05-22
EP1207385A4 EP1207385A4 (en) 2004-11-24
EP1207385B1 true EP1207385B1 (en) 2011-02-09
ID=14235877
EP99923877A Expired - Lifetime EP1207385B1 (en) 1997-12-12 1999-06-03 Optical ct device and method of image reformation
EP (1) EP1207385B1 (en)
AU (1) AU4058999A (en)
DE (1) DE69943188D1 (en)
WO (1) WO2000075633A1 (en)
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1999-06-03 EP EP99923877A patent/EP1207385B1/en not_active Expired - Lifetime
1999-06-03 DE DE69943188A patent/DE69943188D1/en not_active Expired - Lifetime
1999-06-03 WO PCT/JP1999/002960 patent/WO2000075633A1/en active Application Filing
1999-06-03 AU AU40589/99A patent/AU4058999A/en not_active Abandoned
EP1207385A4 (en) 2004-11-24
DE69943188D1 (en) 2011-03-24
WO2000075633A1 (en) 2000-12-14
EP1207385A1 (en) 2002-05-22
AU4058999A (en) 2000-12-28
US7328059B2 (en) 2008-02-05 Imaging of light scattering tissues with fluorescent contrast agents
DE69738550T2 (en) 2009-04-02 Device for classifying tissue
2002-09-25 DAX Request for extension of the european patent (to any country) (deleted)
Ipc: 7G 01N 21/17 B
2004-11-24 A4 Supplementary search report drawn up and despatched
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Expiry date: 20190602