Focused rotating slat-hole for gamma cameras

• US 6,627,893 B1
• Filed: 03/15/2001
• Issued: 09/30/2003
• Est. Priority Date: 03/15/2001
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Gagnon, Daniel, Zeng, Gengsheng Lawrence
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US09/808,935
• Time in Patent Office: 929 Days
• Field of Search: 250/363.1, 250/363.04, 250/363.08
• US Class Current: 250/363.04
• CPC Class Codes: A61B 6/037 Emission tomography
• CPC Class Codes: G01T 1/1644 using an array of optically separate scintillation elements permitting direct location of scintillations G01T1/1645 takes precedence
• CPC Class Codes: G01T 1/1648 Ancillary equipment for scintillation cameras, e.g. reference markers, devices for removing motion artifacts, calibration devices adapted for flow studies G01T1/1647

Abstract

γ-ray emissions (14) are detected by a rotating, one-dimensional detector array (18). Slats of a convergent or divergent collimator (16) are mounted between detector elements. The slats are canted by an angle α from focusing on a focal spot (40) on a perpendicular bisector to the detector array. As a detector head (30) revolves around a longitudinal axis (36) of the subject, the head is canted (FIG. 5) to generate angularly offset data sets. Data sets with the detector array rotated to 180° opposite orientations are processed (62) to generate a first derivative data set. Parallel lines or planes (64) of the canted data sets are processed (68) to generate a second derivative data set which is backprojected (70) in accordance with the Radon transform into a three-dimensional image representation.

Claims

1. A method of diagnostic imaging comprising:

a) introducing a radioactive isotope into a subject located in an imaging region;

b) rotating a solid state detector array and a one-dimensional collimator with one of convergent and divergent slats around a rotation axis in a plane parallel to a longitudinal axis of the subject while detecting photon emissions indicative of nuclear decay while wobbling the detector array and the collimator about the rotation axis to generate a plurality of one-dimensional projections of an examination region each at a plurality of angular orientations;

c) moving the detector array around the longitudinal axis of the subject and while repeating the step (b);

d) from the one-dimensional projections, generating second derivative data sets;

e) reconstructing the second derivative data sets into an image representation of the subject in the imaging region.

2. A method of diagnostic imaging comprising:

introducing a radioactive isotope into a subject located in an imaging region;

collimating the photon emissions with a focused slat collimator, the slats being tilted by a preselected angle from convergent on a symmetric focal spot;

rotating the collimator and a detector array with a planar radiation receiving face around an array rotation axis parallel to a normal to the radiation receiving face while detecting photon emissions to generate a plurality of one-dimensional projection data sets;

from the projection data sets generated with the detector array at 180°

opposite positions generating first derivative data sets;

moving the collimator and the detector array around a longitudinal axis of the subject and while repeating the steps of rotating, collimating, and generating; and

,

reconstructing an image representation of the subject in the imaging region from the first derivative data sets.

3. The method as set forth in claim 2, further including:

while moving the collimator and the detector array around the longitudinal axis of the subject, wobbling the detector array.

4. The method as set forth in claim 3, further including:

wobbling the collimator and the detector array such that a focal spot of the collimator moves along a sinusoidal path.

5. The method as set forth in claim 4, further including:

wobbling the detector array at 180°

opposite positions around the longitudinal axis.

6. The method as set forth in claim 2, further including:

changing an angle of the detector array with respect to the longitudinal axis as the detector moves around the longitudinal axis.

7. The method as set forth in claim 2, further including:

generating additional first derivative data sets with the detector array canted relative to the array rotation axis;

generating second derivative data sets from the first derivative data sets and the another first derivative data sets; and

,

reconstructing the image representation from the second derivative data sets.

8. The method as set forth in claim 7, further including:

backprojecting the second derivative data sets in accordance with the Radon inversion formula to generate a three-dimensional image representation.

9. A diagnostic imaging apparatus comprising:

a detecting means for detecting radiation transmitted one of from and through a subject in an imaging region;

a collimating means with one of converging and diverging vanes mounted to the detecting means for collimating radiation detected by the detecting means;

a first rotating means for rotating and wobbling the detecting means and the collimating means about a rotation axis perpendicular to a longitudinal axis of the subject;

a second rotating means for rotating the detecting means and the collimating means about the longitudinal axis;

a means for generating derivative data sets from the radiation detected by the detecting means as the detecting means wobbles and rotates;

a means for reconstructing the derivative data sets into an image representation of the subject in the imaging region.

10. The diagnostic imaging apparatus as set forth in claim 9, wherein the collimating means includes convergent slats of a highly-attenuating material shifted by an angle α

from a focal point perpendicular to a center of the detecting means.

11. The diagnostic imaging apparatus as set forth in claim 10 wherein the first rotating means rotates and wobbles the detecting means and the collimating means such that the focal spot follows a sinusoidal trajectory.

12. The diagnostic imaging apparatus as set forth in claim 10 wherein the means for generating derivative data sets includes:

a means for subtractively combining radiation detected with the detecting means and the collimating means wobbled to angular orientation in which the collimator focal point is offset to generate first derivative data sets;

a means for sorting the first derivative data sets into parallel planes;

a means for processing the parallel planes of first derivative data into the second derivative data sets.

13. The diagnostic imaging apparatus as set forth in claim 9, wherein the means for generating the derivative data sets includes:

a means for generating first derivative data set from the detected radiation; and

a means for generating second derivative data sets from the first derivative data sets.

14. A diagnostic imaging apparatus including:

a detector array which generates projection data in response to detected radiation;

a collimator with angled slats mounted to the detector array to collimate detected radiation such that the array generates planar projection data sets;

a means for rotating and wobbling the detector array and the collimator to obtain complimentary data sets which complimentary data sets generate first derivative data sets when subtracted;

a means for subtracting the complimentary data sets to generate first derivative data sets;

a means for generating a second derivative data sets from sets of the first derivative data sets;

a means for backprojecting the second derivative data sets into a volume image memory.

15. A SPECT camera comprising:

a detector head which is mounted for movement about an axis of a subject, the detector head including;

a linear array of detector elements mounted in the detector head for rotation about a detector axis of rotation and generating output signals,

a magnifying collimator having slats mounted between the detector elements of the array and angled to converge generally toward a focal point,

a means for rotating and wobbling the detector head around the detector axis of rotation such that the focal point follows an oscillating trajectory;

a means for combining the output signals from the linear array of detector elements as the focal point moves along the oscillating trajectory to generate first derivative data sets;

a means for generating second derivative data sets from the first derivative data sets;

a reconstruction processor which reconstructs the second derivative data sets into an image representation.

16. The camera as set forth in claim 15 wherein the slats are angled an angle α

from converging precisely on the focal point, where α

is greater than 0° and

less than 5°

.

17. A method of nuclear imaging comprising:

moving a linear detector array and a convergent collimator around a detector axis of rotation and around a subject axis of rotation and with a wobble that causes a focal point of the collimator to oscillate;

converting radiation from the subject which passes through the convergent collimator and is detected by the detector array into electrical signals;

subtracting electrical signals from the detector array generated at 180°

opposite orientations around the detector axis to generate first derivative data sets;

generating second derivative data sets from first derivative data sets with the focal point oscillated;

reconstructing the second derivative data sets into a magnified volumetric image representation.

18. A method of nuclear imaging comprising:

stepping a linear detector array and a convergent collimator about a subject region of interest through a series of steps;

at each step, rotating and canting the detector array and the collimator relative to an axis perpendicular to a face of the detector;

converting radiation which passes through the collimator and is detected by the detector array into electrical signals;

generating first derivative data sets from the electrical signals;

generating second derivative data sets, each second derivative data set generated from a plurality of the first derivative data sets which are canted relative to each other;

backprojecting the second derivative data sets into a volumetric image representation.

19. The method as set forth in claim 18 further including:

shifting the detector axis of rotation during the rotating step.

20. The method as set forth in claim 18 further including:

orienting slats of the convergent collimator an angle α

offset from a focal spot which lies on a perpendicular bisector of the collimator, the angle α

being between 0° and

5°

.