Simultaneous multi-headed imager geometry calibration method
A method for calibrating multi-headed high sensitivity and high spatial resolution dynamic imaging systems, especially those useful in the acquisition of tomographic images of small animals. The method of the present invention comprises: simultaneously calibrating two or more detectors to the same coordinate system; and functionally correcting for unwanted detector movement due to gantry flexing.
1. In a method for obtaining high resolution dynamic images of conscious living subjects comprising the simultaneous acquisition of multiple images by a plurality of gantry mounted, high sensitivity and high spatial resolution dynamic pinhole or parallel-hole collimator imagers that may be subject to unwanted movement due to gantry flexing or axial motion that affects the spatial resolution of the multiple images, the improvement comprising:
A) calibrating two or more of the imagers to the same coordinate system; and
B) functionally correcting the acquired multiple images for unwanted detector movement due to gantry flexing and axial motion to obtain corrected spatial resolution of the acquired multiple images through the iterative application of the following equation:
Δ v≈f/d ( d tan(Δφ))= f tan(Δφ)
wherein v is one of two orthogonal coordinates defined in the plane of the detector, d is the distance from the axis of rotation to the pinhole and Δφ is the rocking angle through which the detector moves during rotation about a target.
2. The method of claim 1 wherein the functional correction for axial motion is obtained through the iterative application of the following equations:
v
=
-
f
(
m
v
-
z
0
′′′
-
g
z
′′′
)
d
-
y
0
′′′
-
g
y
′′′
+
m
v
+
e
v
u
=
-
f
(
m
u
-
x
0
′′′
-
g
x
′′′
)
d
-
y
0
′′′
-
g
y
′′′
+
m
u
+
e
u
wherein u and v are coordinates in the projection space or coordinates of detectors; m and e are mechanical and electronic shifts; and the triple primed coordinates (x 0 ″′, y 0 ″′, z 0 ″′) denote transformations without axial motion term g.
3. The method of claim 2 wherein functional correction for unwanted detector movement due to gantry flexing is obtained through the iterative application of the following equation:
Δ v≈f/d ( d tan(Δφ))= f tan(Δφ)
wherein v is one of two orthogonal coordinates defined in the plane of the detector, d is the distance from the axis of rotation to the pinhole and Δφ is the rocking angle through which the detector moves during rotation about a target.
4. In a method for obtaining high resolution dynamic images of conscious living subjects comprising the simultaneous acquisition of multiple images by a plurality of gantry mounted, high sensitivity and high spatial resolution dynamic pinhole or parallel-hole collimator imagers that may be subject to unwanted movement due to gantry flexing or axial motion that affects the spatial resolution of the multiple images, the improvement comprising:
A) calibrating two or more of the imagers to the same coordinate system;
B) functionally correcting the acquired multiple images for unwanted detector movement due to gantry flexing through the iterative application of the following equation:
Δ v≈f/d ( d tan(Δφ))= f tan(Δφ)
wherein v is one of two orthogonal coordinates defined in the plane of the detector, d is the distance from the axis of rotation to the pinhole and Δφ is the rocking angle through which the detector moves during rotation about a target and axial motion; and
correction for axial motion is obtained through the iterative application of the following equations:
v
=
-
f
(
m
v
-
z
0
′′′
-
g
z
′′′
)
d
-
y
0
′′′
-
g
y
′′′
+
m
v
+
e
v
u
=
-
f
(
m
u
-
x
0
′′′
-
g
x
′′′
)
d
-
y
0
′′′
-
g
y
′′′
+
m
u
+
e
u
wherein u and v are coordinates in the projection space or coordinates of detectors; m and e are mechanical and electronic shifts; and the triple primed coordinates (x 0 ″′, y 0 ″′, z 0 ″′) denote transformations without axial motion term g to obtain corrected spatial resolution of the acquired multiple images.