Stationary inspection system for three-dimensional imaging employing electronic modulation of spectral data from Compton-scattered gammas

• US 7,643,604 B2
• Filed: 08/11/2008
• Issued: 01/05/2010
• Est. Priority Date: 02/28/2002
• Status: Expired due to Fees

• Current Assignee: Clyde P. Jupiter, Nenad N. Kondic
• Original Assignee: Clyde P. Jupiter, Nenad N. Kondic
• Inventors: Kondic, Nenad N., Jupiter, Clyde P.
• Primary Examiner(s): Glick; Edward J
• Assistant Examiner(s): Midkiff; Anastasia
• Application Number:
  US12/189,762
• Publication Number:
  US 20090060119A1
• Time in Patent Office: 512 Days
• Field of Search: 378/2, 378/62, 378/63, 378 80- 82, 378 86- 89, 250/363.06
• US Class Current: 378/2
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]

Abstract

An inspection system according to various embodiments can include a stationary mono-energetic gamma source and a detector-spectrometer. The detector-spectrometer is configured to employ a modulation of energy bin boundaries within a multi-channel pulse height analyzer to encode voxels within the inspected object, and apply an analysis to determine the three-dimensional density image of the inspected object.

Claims

1. A three-dimensional image-generating device comprising:

an external gamma radiation source configured to irradiate an inspected object with source gamma rays to generate a three-dimensional representation of said inspected object;

a radiation detector configured to detect Compton-scattered gamma rays scattered from within said inspected object,

wherein said radiation detector comprises a gamma spectrometer and approximates a point detector;

wherein said gamma spectrometer is configured to register a plurality of single detection events of said Compton-scattered gamma rays, wherein said plurality of single detection events are detected individually; and

wherein said gamma spectrometer is configured to concurrently measure energies of Compton-scattered gamma photons associated with said detection events;

a multi-channel pulse height analyzer coupled to said gamma spectrometer and configured to analyze voltage pulse heights representing the energies of the Compton-scattered gamma photons and sort the voltage pulse heights based upon the energies of the Compton-scattered gamma photons, into a plurality of energy bins;

said gamma spectrometer and the multi-channel pulse-height analyzer are configured to determine a bin-average value of energy for said Compton-scattered gamma rays having a predetermined energy bin width;

said gamma spectrometer is configured to determine values of the gamma count rate for said Compton-scattered gamma rays arriving at the detector, wherein predetermined energy bin widths are established for counted gamma rays having specific energies;

said multi-channel pulse height analyzer is configured to assign the bin-average value of energy for each Compton-scattered photon having an energy associated with a specific isogonic arc having a specific radius;

said multi-channel pulse height analyzer is configured to determine energy bin boundaries for each energy bin such that each energy bin is represented by a first isogonic arc having a first radius and a second isogonic arc having a second radius, wherein the first radius is less than the second radius;

said multi-channel pulse height analyzer is configured to determine the energy bin widths and to represent a virtual two-dimensional space between the first isogonic arc and the second isogonic arc and having an inter-arc strip configuration.

2. The device as recited in claim 1, wherein voltage set points of energy bins define boundaries of the inter-arc strips within said inspected object such that the inter-arc strip is configured to taper and define a first point at the source and a second point at the radiation detector and being widest at a mid-point between the source and the radiation detector.

3. The device as recited in claim 2, further comprising:

an electronic oscillator connected to the multi-channel pulse height analyzer voltage power supply and configured to fluctuate the voltage set points of an individual energy bin to produce a corresponding fluctuation in the width of the inter-arc strip.

4. The device as recited in claim 3, wherein a geometrical effect of the tapering of the inter-arc strip in combination with the Compton energy-angle relationship for the scattered gammas generates a non-uniform fluctuation in the width of the inter-arc strip in an x-direction along the length of the inter-arc strip.

5. The device as recited in claim 4, wherein a variation in the inter-arc strip width at an upper boundary and a lower boundary is calculated according to equations:

$\mathrm{\Delta <br><br>}<br><br><br><br>y_1=\mathrm{\Delta <br><br>}<br><br><br><br>E_1<br><br>L<br><br>\left(\frac{\mathrm{Ee}}{E_1^2}\right)<br><br>\frac{\cos <br><br><br><br>\mathrm{\phi <br><br>}<br><br>\left(x\right)-\cos <br><br><br><br>{\mathrm{\theta <br><br>}}_1}{{\sin }^3<br><br><br><br>{\mathrm{\theta <br><br>}}_1},\mathrm{with}<br><br><br><br>\mathrm{\phi <br><br>}={\mathrm{\theta <br><br>}}_1-x/R_1$ $\mathrm{\Delta <br><br>}<br><br><br><br>y_2=\mathrm{\Delta <br><br>}<br><br><br><br>E_2<br><br>L<br><br>\left(\frac{\mathrm{Ee}}{E_2^2}\right)<br><br>\frac{\cos <br><br><br><br>\mathrm{\phi <br><br>}<br><br>\left(x\right)-\cos <br><br><br><br>{\mathrm{\theta <br><br>}}_2}{{\sin }^3<br><br><br><br>{\mathrm{\theta <br><br>}}_2},\mathrm{with}<br><br><br><br>\mathrm{\phi <br><br>}={\mathrm{\theta <br><br>}}_2-x/R_2$

Δ

E₁ denotes a fluctuating amplitude of the lower limit of the energy bin;

Δ

E₂ denotes a fluctuating amplitude of the upper limit of the energy bin;

Ee=0.511 MeV and is the relativistic rest mass of the electron;

R₁ denotes a radius of curvature of the first isogonic arc; and

R₂ denotes a radius of curvature of the second isogonic arc.

6. The device as recited in claim 5, wherein said variation in the width of the inter-arc strip depends on an x-variable along the length of the inter-arc strip.

7. The device as recited in claim 6, wherein said energy bin boundaries comprise a lower energy boundary and an upper energy boundary;

and

a periodic variation in the upper boundary of the energy bin voltage differs in amplitude from a periodic variation in the lower boundary of the energy bin voltage.

8. The device as recited in claim 7, wherein said oscillator varies at least two individual energy bin boundaries with at least a pair of unique periodic trigonometric oscillations such that two-dimensional pixels within the associated inter-arc strip are encoded by corresponding unique individual oscillations.

9. The device as recited in claim 8, wherein rotation of the inter-arc strip around the axis defined by the chord connecting the source and the detector converts the two-dimensional pixels within the inter-arc strip into three-dimensional voxels.

10. The device as recited in claim 9, wherein the multi-channel pulse height analyzer is configured to correlate each voxel location with a count rate of the detected gammas scattered from within the voxel, and to reconstruct a three-dimensional density distribution within the inspected object.