Method for optically inspecting human body and apparatus for the same

• US 5,148,022 A
• Filed: 02/13/1990
• Issued: 09/15/1992
• Est. Priority Date: 02/15/1989
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ito, Yoshitoshi, Takeuchi, Hiroshi, Mitsui, Yasuhiro, Kawaguchi, Fumio, Haida, Munetaka
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US07/479,171
• Time in Patent Office: 945 Days
• Field of Search: 250/339, 250/341
• US Class Current: 250/339.06
• CPC Class Codes: A61B 5/0073 by tomography, i.e. reconstruction of 3D images from 2D projections A61B5/0066 takes precedence
• CPC Class Codes: A61B 5/7242 using integration

Abstract

A method for optically inspecting a human body and an apparatus for the same serve to scan a light pulse having a visible wavelength to an infrared one on a specific sliced portion of a body to be inspected, for obtaining pieces of projection data about light absorption and to reconstruct an image about distribution of light absorption from the projection data with a computer tomogram. The projection data is measured by alternately radiating a first light pulse at a first wavelength in an absorption wavelength band specific to metabolic materials to be imaged and a second light pulse at a second wavelength being closer to said first wavelength. Then, the data about the transmitted beams are produced by deriving a ratio of integrated values of the first signal to the second one residing within a specific time gate.

Claims

1. A method for optically inspecting a human body to be inspected comprising the steps of:

a) radiating a first light pulse of a first wavelength from a radiating spot to said human body and detecting the first light pulse transmitted through said human body at least at a specific light-reception spot, said first wavelength being selected within a wavelength range from a visible wavelength to an infrared wavelength and being overlapped with an absorption wavelength band specific to metabolic materials contained in said human body to be inspected;

b) radiating a second light pulse of a second wavelength from said radiating spot to said human body to be inspected and detecting the second light pulse transmitted through said human body at least at said specific light-reception spot, said second wavelength being close to said first wavelength so that light attenuation due to light scattering in said human body to be inspected utilizing said second wavelength is substantially the same as light attenuation due to light scattering in said human body to be inspected utilizing said first wavelength;

c) respectively extracting integrated values of light pulse transmission at said first and second wavelengths detected at least at said light-reception spot within a specific time gate;

d) computing a ratio of said integrated value of the light pulse transmission at said first wavelength to that of the light pulse transmission at said second wavelength;

e) iteratively executing said steps a), b), c), and d) as said radiating spot and said light-radiating spot are changed in succession, for obtaining pieces of projection data from said ratio of integrated values being successively provided; and

f) reconstructing an image bout distribution of absorbed light in said human body from said pieces of projection data.

2. The method as set forth in claim 1 wherein said time gate width is wider than the pulse width of said first and second light pulses.

3. The method as set forth in claim 1 wherein the gate width of said time gate is defined according to a light path width to be restricted.

4. The method as set forth in claim 1 wherein said time gate is required to be opened on such a timing as having a time lag behind the pulse leading edge of said each light pulse.

5. The method as set forth in claim 1 wherein said time gate is implemented by opening or shutting a light shutter provided on said each light-receptacle spot.

6. The method as set forth in claim 1 wherein said first and second light pulse transmissions are transformed into electronic beams, said electronic beams are swept as time passes, and the resulting beams are recorded as a distribution of intensity of said electronic beams.

7. A method for optically inspecting a human body to be inspected comprising the steps of:

a) radiating a first light pulse of a first wavelength from a radiating spot to said human body and detecting within a first time gate the first light pulse transmitted through said human body at at least a specific light-receptacle spots, said first wavelength being selected within a wavelength range from a visible wavelength to an infrared wavelength and being overlapped with an absorption wavelength band specific to metabolic materials in said human body to be inspected

b) radiating a second light pulse of a second wavelength from said radiating spot to said human body to be inspected and detecting within a second time gate the second light pulse transmitted through said human body at least at said specific light-reception spot, said second wavelength being close to said first wavelength so that light attenuation due to light scattering in said human body to be inspected utilizing said second wavelength is substantially the same as light attenuation due to light scattering in said human body to be inspected utilizing said first wavelength;

c) respectively extracting integrated values of light pulse transmission at said first and second wavelengths detected at least at said light-reception spot;

d) computing a ratio of said integrated value of the light pulse transmission at said first wavelength to said integrated value of the light pulse transmission at said second wavelength;

e) iteratively executing said steps a(, b), c), and d) as said radiating spot and said light-reception spot are changed in succession, for obtaining pieces of projection data from said ratio of integrated values being successively provided; and

f) reconstructing an image bout distribution of absorbed light in said human body from said pieces of projection data.

8. The method as set forth in claim 7 wherein said first and second time gate widths are wider than the pulse widths of said first and second light pulses.

9. The method as set forth in claim 7 wherein said first and second time gates are defined according to a light path width to be restricted.

10. The method as set forth in claim 7 wherein said first and second time gates are required to be opened on such a timing as having a time lag behind the leading edge of said each light pulse.

11. A method for optically inspecting a human boy to be inspected comprising the steps of:

a) radiating a first light pulse of a first wavelength from a radiation spot to said human body, said first wavelength being selected within a wavelength range from a visible wavelength to an infrared wavelength and being overlapped with an absorption wavelength band specific to metabolic materials contained in said human body to be inspected;

b) detecting said first light pulse transmitted through said human body at least at a specific light-reception spot, transforming said first light pulse detected at least at said light-reception spot into an electronic beam, electrically sweeping said electronic beam as time passes, recording a first optical time spectrum indicating the time change of light transmission at said first wavelength;

c) radiating a second light pulse of a second wavelength from said radiation spot to said human body to be inspected, said second wavelength being close to said first wavelength so that light attenuation due to light scattering in said human body to be inspected utilizing said second wavelength is substantially the same as light attenuation due to light scattering in said human body to be inspected utilizing said first wavelength;

e) detecting said second light pulse transmitted through said human body at least at said specific light-reception spot, transforming said second light pulse detected at least at said light reception spot into an electronic beam, electrically sweeping said electronic beams as time passes, and recording a second optical time spectrum indicating the time change of said light transmission at said second wavelength;

f) integrating each signal of said first and second optical time spectrum with time gates, and computing a ratio of both integrated values;

g) integrating each signal of said first and second optical time spectrums with time gates, and computing a ratio of both integrated values;

h) iteratively executing said steps a), b), c), and d) as said radiating spot and at least said light-reception spot are changed in succession, for obtaining pieces of projection data from said ratio of integrated values being successively provided; and

i) reconstructing an image bout distribution of absorbed light in said human body from said pieces of projection data.

12. The method as set forth in claim 11 wherein said time gate widths are wider than the pulse widths of said first and second light pulses.

13. The method as set forth in claim 11 wherein said time gates are defined according to a light path width to be restricted.

14. A method for optically inspecting a human body comprising the steps of:

a) fixing said body to be inspected and measuring and recording an outer shape of a predetermined section thereof;

b) radiation a first light pulse of a first wavelength to said human body to be inspected from a specific radiating spot on said section, said first wavelength being selected within a wavelength range from a visible wavelength to an infrared wavelength and being overlapped with an absorption wavelength band specific to metabolic materials contained in said human body, and measuring the first light pulse transmitted through said human body at least at a specific light-reception spot on said section;

c) radiating a second light pulse at a second wavelength from said radiation spot to said human body, said second wavelength being close to said first wavelength so that light attenuation due to light scattering in said human body to be inspected utilizing said second wavelength is substantially the same as light attenuation due to light scattering in said human body to be inspected utilizing said first wavelength, and measuring said second light pulse transmitted through said human body at least at said light reception spot;

d) extracting an integrated value of light pulse transmission at said first wavelength residing within a first time gate having a specific width, said first time gate being opened in a manner to have a time lag behind the leading edge of said first light pulse, said time lag being defined according to a light path length in the human body, and said light path length being defined on said outer shape;

e) extracting an integrated value of light pulse transmission at said second wavelength residing within a second time gate having a specific width, said second time gate being opened in a manner to lag behind the leading edge of said second light pulse;

f) deriving a ratio of said integrated value of the light pulse transmission at said first wavelength to that of the light pulse transmission at said second wavelength;

g) iteratively executing said steps b), c), d), e), and f) as said radiating spot and at least said light-reception spot are changing on said section, for obtaining pieces of projection data based on said ratio being being successively derived; and

h) reconstructing an image about distribution of light absorption on said section of said human body from said pieces of projection data.

15. The method as set forth in claim 14, wherein said outer shape is measured by scanning a light beam on said section and obtaining projections of said human body at said section.

16. An apparatus for optically inspecting a human body comprising:

light-radiating means for alternately radiating to said human body to be inspected a first light pulse of a first wavelength, said first wavelength being selected within a wavelength range from a visible wavelength to an infrared wavelength and being overlapped with an absorption wavelength band specific to metabolic materials contained in said human body, and a second light pulse of a second wavelength being close to said first wavelength so that light attenuation due to light scattering in said human body to be inspected utilizing said second wavelength is substantially the same as light attenuation due to light scattering in said human body to be inspected utilizing said first wavelength;

scanning mans for changing direction of radiation for each combination of radiation of said first and second light pulses;

an optical detector means for serially detecting said first and second light pulses transmitted through said human body;

time gate means for restricting said first and second light pulses output at sad optical detector means; and

data-processing means for deriving a ratio of an integrated value o said detected light pulse transmission at said first wavelength to that of said detected light pulse transmission at said second wavelength for each of angles a direction of radiation to provide projection data about said human body from said projection data.