U.S. patent application number 14/309675 was filed with the patent office on 2015-04-30 for gamma imaging probe position signal processing method.
The applicant listed for this patent is Institute of Nuclear Energy Research Atomic Energy Council, Executive Yuan. Invention is credited to MEEI-LING JAN, CHING-WEI KUO, HSIN-CHIN LIANG.
Application Number | 20150117612 14/309675 |
Document ID | / |
Family ID | 52995468 |
Filed Date | 2015-04-30 |
United States Patent
Application |
20150117612 |
Kind Code |
A1 |
LIANG; HSIN-CHIN ; et
al. |
April 30, 2015 |
GAMMA IMAGING PROBE POSITION SIGNAL PROCESSING METHOD
Abstract
The present invention based on not changing hardware design,
which means that each imaging detector keep independent
considerations, the weighted value of the circuit to be pushed back
the weight of the original signal, and then estimate the amount of
the original signal in a virtual cascade circuit to renew weighted
signal; this estimation process through simplification, only simple
addition and multiplication calculations on real numbers need to be
implemented. Advantage of the present invention is that the signal
data through a simple operation will complete the estimate.
Executing the estimate in hardware without increasing storage
capacity of the rear-end list mode data, and also to achieve a
continuous and effective imaging area to expand and enhance the
probe's sensitivity and keep a higher signal to noise ratio (S/N
ratio).
Inventors: |
LIANG; HSIN-CHIN; (Taoyuan
County, TW) ; JAN; MEEI-LING; (TAOYUAN COUNTY,
TW) ; KUO; CHING-WEI; (TAOYUAN COUNTY, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Institute of Nuclear Energy Research Atomic Energy Council,
Executive Yuan |
TAOYUAN COUNTY |
|
TW |
|
|
Family ID: |
52995468 |
Appl. No.: |
14/309675 |
Filed: |
June 19, 2014 |
Current U.S.
Class: |
378/98.2 |
Current CPC
Class: |
G01T 1/1647 20130101;
H04N 5/378 20130101 |
Class at
Publication: |
378/98.2 |
International
Class: |
G06T 7/00 20060101
G06T007/00; H04N 5/378 20060101 H04N005/378; H04N 5/32 20060101
H04N005/32 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 25, 2013 |
TW |
102138705 |
Claims
1. A position signal processing method for gamma imaging probe,
comprising; a step of establishing estimation-model built-up
section; and a step of establishing an application mode section,
wherein, the gamma imaging probe is a combination of a plurality of
independent detectors, each independent detector has same structure
in design, in which, each channel of signal is equally-divided or
duplicated into two directional signal branches X and Y, and thus
in X and Y direction there is its own L and N number of branch
respectively, the signal branches in each direction are processed
with its own weight model G for the calculation of
addition/multiplication to obtain the two position signal with
respect to each direction, that is, X+, X-, Y+ and Y-, which can be
used to define a rectangular image area, therefore, the weight
model can be formulated as G.sub.X+=[G.sub.1.sup.X+G.sub.2.sup.X+ .
. . G.sub.L.sup.X+], G.sub.X-=[G.sub.1.sup.X-G.sub.2.sup.X- . . .
G.sub.L.sup.X-], G.sub.Y+=[G.sub.1.sup.Y+G.sub.2.sup.Y+ . . .
G.sub.N.sup.Y+] and G.sub.Y-=[G.sub.2.sup.Y-G.sub.2.sup.Y- . . .
G.sub.N.sup.Y-].
2. The position signal processing method for gamma imaging probe of
claim 1, wherein, the estimation-model built-up section is to
determine the specification of the probe, the detectors and the
weighted circuit, the method of the section comprising: revering
the original un-weighted signals of each image detector;
establishing a weighted-model for a virtual circuit; estimating
branching weighted signals in the two sides of each intersection
area of the virtual circuit; and establishing estimation model for
the position signal in the virtual circuit.
3. The position signal processing method for gamma imaging probe of
claim 2, wherein, when combining/number of image detectors with
respect to the X direction, the step of revering the original
un-weighted signals of each image detector is to modify the event
that occurred in the merged area of two image detector, that is,
the merged area of the m-th image detector and the (m+1)-th image
detector, wherein the m=1 . . . l-1, meaning the signal occurred
simultaneously on the m-th detector in the branch L and the
(m+1)-th detector in the branch 1, therefore, the original signal
of the m-th detector in the branch L is S L X m 0 = X m - G L X - +
X m + G L X + , ##EQU00007## wherein X.sub.m.sup.- and
X.sub.m.sup.+ are the signal of the m-th detector with respect to
the direction X output from an AC/DC converter, and the original
signal of the (m+1)-th detector on the branch l is S 1 X m + 1 0 =
X ( m + 1 ) - G 1 X - + X ( m + 1 ) + G 1 X + , wherein
##EQU00008## X ( m + 1 ) - and X ( m + 1 ) + ##EQU00008.2## are the
signals of the (m+1)-th detector with respect to the direction X
output from the AC/DC converter.
4. The position signal processing method for gamma imaging probe of
claim 2, wherein, the step of establishing a weight model for a
virtual circuit is to combine l image detectors with respect to the
direction X, the weight model of the combined 1 image detectors can
be represented as G.sub.X+.sup.v=[G.sub.1.sup.X+G.sub.2.sup.X+ . .
. G.sub.L.sup.X+G.sub.(L+1).sup.X+ . . .
G.sub.mL.sup.X+G.sub.(mL+1).sup.X+ . . . G.sub.lL.sup.X+], and
G.sub.X-.sup.v=[G.sub.1.sup.X-G.sub.2.sup.X- . . .
G.sub.L.sup.X-G.sub.(L+1).sup.X- . . .
G.sub.mL.sup.X-G.sub.(mL+1).sup.X- . . . G.sub.lL.sup.X-].
5. The position signal processing method for gamma imaging probe of
claim 2, wherein, the step of estimating branching weighted signals
in the two sides of each intersection area of the virtual circuit
is to multiple the weight of the original signal and the weight of
the virtual circuit, which can be expressed as
S.sub.mL.sup.X-=.sub.m.sup.0S.sub.L.sup.X.times.G.sub.mL.sup.X-;
S.sub.mL.sup.X+=.sub.m.sup.0S.sub.L.sup.X.times.G.sub.mL.sup.X+
S.sub.(mL+1).sup.X-=.sub.(m+1).sup.0S.sub.L.sup.X+.times.G.sub.(mL+1).sup-
.X-;
S.sub.(mL+1).sup.X+=.sub.(m+1).sup.0S.sub.L.sup.X+.times.G.sub.(mL+1-
).sup.X+;
6. The position signal processing method for gamma imaging probe of
claim 2, wherein, the step of establishing estimation model for the
position signal in the virtual circuit is to build up the final
position signal of the virtual combined circuit, which is to
estimate the mathematical formulation of the four position signal
in each of the two original image detectors, wherein, the output
signals of the virtual circuit are X.sup.+, X.sup.-, Y.sup.+ and
Y.sup.- and the output signals of AC/DC converter of two original
image detectors are X.sup.+.sub.m, X.sup.-.sub.m, Y.sup.+.sub.m,
Y.sup.-.sub.m, X.sup.+.sub.(m+1), X.sup.-.sub.(m+1),
Y.sup.+.sub.(m+1) and Y.sup.-.sub.(m+1), and the signal of the
virtual circuit with respect to the combined direction can be
formulated as X.sup.+=S.sub.mL.sup.X++S.sub.(mL+1).sup.X+,
X.sup.-=S.sub.mL.sup.X-+S.sub.(mL+1).sup.X-, and the signal of the
virtual circuit with respect to the non-combined direction is the
sum of the original signal of the two original image detector and
is formulated as Y.sup.+=Y.sup.+.sub.m+Y.sup.+.sub.(m+1),
Y.sup.-=Y.sup.-.sub.m+Y.sup.-.sub.(m+1), and consolidating the
steps of revering the original un-weighted signals of each image
detector, the step of establishing a weight model for a virtual
circuit is to combine/image detectors with respect to the direction
X and the step of estimating branching weighted signals in the two
sides of each intersection area of the virtual circuit to obtain
new formulation (1) and (2) for the combination/image detectors
with respect to the direction X, the formulation (1) and (2) are as
follows, { X + = R 1 X m - + R 2 X m + + R 3 X ( m + 1 ) - + R 4 X
( m + 1 ) + X - = R 5 X m - + R 6 X m + + R 7 X ( m + 1 ) - + R 8 X
( m + 1 ) + Y + = Y m + + Y ( m + 1 ) + Y - = Y m - + Y ( m + 1 ) -
formulation ( 1 ) wherein , [ R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 ] = [
G mL X + G L X - G mL X + G L X + G ( mL + 1 ) X + G L X - G ( mL +
1 ) X + G 1 X + G mL X - G L X - G mL X - G L X + G ( mL + 1 ) X -
G 1 X - G ( mL + 1 ) X - G 1 X + ] formulation ( 2 ) ##EQU00009##
and when n number of image detectors are combined with respect to
the Y direction, the estimation-model for the event occurred in the
intersection area of the k-th image detector and the (k+1)-th image
detector can be expressed as { X + = X k + + X ( k + 1 ) + X - = X
k - + X ( k + 1 ) - Y + = R 9 Y k - + R 10 Y k + + R 11 Y ( k + 1 )
- + R 12 Y ( k + 1 ) + Y - = R 13 Y k - + R 14 Y k + + R 15 Y ( k +
1 ) - + R 16 Y ( k + 1 ) + ; wherein , [ R 9 R 10 R 11 R 12 R 13 R
14 R 15 R 16 ] = [ G mN Y + G N Y - G mN Y + G N Y + G ( mN + 1 ) Y
+ G 1 Y - G ( mN + 1 ) Y + G 1 Y + G mN Y - G N Y - G mN Y - G N Y
+ G ( mN + 1 ) Y - G 1 Y - G ( mN + 1 ) Y - G 1 Y + ] ,
##EQU00010## and in a condition that a image probe formed with
i.times.n image detectors, and the events occurred in the
intersection of the four image detectors by the columns m and m+1
with respect to the direction X and the rows k and k+1 with respect
to the direction Y, wherein, m=1 . . . l-1, while k=1 . . . n-1,
the estimation-model of the position signals of the virtual circuit
can be expressed as { X + = R 1 ( X m - + X ( kl + m ) - ) + R 2 (
X m + + X ( kl + m ) + ) + R 3 ( X ( m + 1 ) - + X ( kl + m + 1 ) -
) + R 4 ( X ( m + 1 ) + + X ( kl + m + 1 ) + ) X - = R 5 ( X m - +
X ( kl + m ) - ) + R 6 ( X m + + X ( kl + m ) + ) + R 7 ( X ( m + 1
) - + X ( kl + m + 1 ) - ) + R 8 ( X ( m + 1 ) + + X ( kl + m + 1 )
+ ) Y + = R 9 ( Y m - + Y ( m + 1 ) - ) + R 10 ( Y m + + Y ( m + 1
) + ) + R 11 ( Y ( kl + m ) - + Y ( kl + m + 1 ) - ) + R 12 ( Y (
kl + m ) + + Y ( kl + m + 1 ) + ) Y - = R 13 ( Y m - + Y ( m + 1 )
- ) + R 14 ( Y m + + Y ( m + 1 ) + ) + R 15 ( Y ( kl + m ) - + Y (
kl + m + 1 ) - ) + R 16 ( Y ( kl + m ) + + Y ( kl + m + 1 ) + ) ,
formulation ( 5 ) ##EQU00011## wherein, [R.sub.1 R.sub.2 . . .
R.sub.8] is same as that in formulation (2), [R.sub.9 R.sub.10 . .
. R.sub.16] is same as that in formulation (4).
7. The position signal processing method for gamma imaging probe of
claim 1, wherein, the step of establishing a application mode
section is to apply the estimation-model built in the
estimation-model built-up section to the probe and the modification
of cross-detector events, wherein, the step of establishing an
application mode section comprising: step (1): using trigger
message, position signals, and sum of signals generating from the
probe to obtain the ratio of X.sup.+/X.sup.- and Y.sup.+/Y.sup.-
from the detector showing the maximum sum of signals, to compare
with thresholds T.sub.X+, T.sub.X-, T.sub.Y+ and T.sub.Y- to
determine the occurrence of the cross-detector event, and then
using trigger message to determine the column and row number (m, k)
of a target image detector; step (2): when a cross-detector event
occurred, using the estimation model to modify the event occurred
in the two- or four-detector intersection area; step (3): when no
cross-detector event occurred, mapping each corresponding position
to its relative position in the entire probe; and step (4): using a
digital processor to combine whole the info nation from the step
(2) and (3) to form a gamma image position response of the
probe.
8. The position signal processing method for gamma imaging probe of
claim 7, wherein, the step (1) of establishing an application mode
section is to determine the occurrence of cross-detector event, if
normal event occurred, only one of the image detectors in the probe
transmits trigger message, position signals and sum of signals, if
the cross-detector event occurred, a plurality of (two or four)
image detectors in the probe transmit trigger messages, position
signals and sums of signals, then the image detector with the
maximum sum of signals is used for determination, a ratio
X.sub.+/X.sub.- is established based on the position signals of the
image detector with respect to X direction to determine whether the
ratio is greater than the threshold value T.sub.X+ or smaller than
the threshold value T.sub.X-; T.sub.X+ and T.sub.X- are determined
by the weight of the read-out circuit of each image detector,
wherein, T.sub.X+=G.sub.L-1.sup.X+/G.sub.2.sup.X+,
T.sub.X-=G.sub.L-1.sup.X--/G.sub.2.sup.X-; if
X.sub.+/X->T.sub.X+ is true, meaning the cross-detector event
occurred with respect to the X direction, following the number of
position indicating in the trigger message transmitting from the
image detector leads to the column m in the image detector array,
and the next position adjacent to the column m with respect to
direction X.sub.+ is the (m+1)-th image detector, if
X.sub.+/X.sub.-<T.sub.X+ is true, meaning the cross-detector
event occurred with respect to the X direction, following the
number of position indicating in the trigger message transmitting
from the image detector leads to the column m+1 in the image
detector array, and the last position adjacent to the column m+1
with respect to direction X- is the ni-th image detector, the ratio
Y.sub.+/Y.sub.- is established for determination, wherein,
T.sub.Y+=G.sub.N-1.sup.Y+/G.sub.2.sup.Y+,
T.sub.Y-=G.sub.N-1.sup.Y-/G.sub.2.sup.Y-; if
Y.sub.+/Y.sub.->T.sub.Y+ is true, meaning the cross-detector
event occurred with respect to the Y direction, following the
number of position indicating in the trigger message transmitting
from the image detector leads to the row k in the image detector
array, and the next position adjacent to the row k with respect to
direction Y.sub.+ is the (k+1)-th image detector, if
Y.sub.+/Y-<T.sub.Y+ is true, meaning the cross-detector event
occurred with respect to the Y direction, following the number of
position indicating in the trigger message transmitting from the
image detector leads to the row k+1 in the image detector array,
and the last position adjacent to the column k+1 with respect to
direction Y- is the k-th image detector.
9. The position signal processing method for gamma imaging probe of
claim 6, wherein, the step (2) of establishing an application mode
section is, based on the result from the step (1), to modify the
event occurred in the two- or four-detector intersection area with
the formulation driven from the estimation-model built-up section,
if the cross-detector event occurred with respect to the direction
X, the formulations (1) and (2) apply, while the cross-detector
event occurred with respect to the direction Y, the formulations
(3) and (4) apply, if the cross-detector event occurred with
respect to both directions X and Y, the formulations (5), (2) and
(4) apply.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a gamma imaging probe
position signal processing method, more particularly, to a gamma
imaging probe position signal processing method for correctly
retaining the information of position of the signal of the event
occurred in a signal sharing area of two adjacent image detector,
so as to avoid the problem of large area of image being separated
discontinuously.
BACKGROUND OF THE INVENTION
[0002] In design, the gamma imaging probe is made of scintillator
array coupled to photo multipliers or array, which is in an
application of pixelated in operation, and with dedicated read-out
circuit, to obtain the position of X, Y and the intensity E of the
signal in the image detector.
[0003] A practical imaging probe should be capable of detecting the
entire area of the object being detected. However, because of the
size of a single photo multiplier, the area is therefore limited.
To overcome such constraints, a plurality of imaging detector is
combined to be a larger size imaging probe to cover more area being
detected. A larger size imaging probe, as shown in FIG. 5,
basically is a series of combination of many single-size imaging
detectors side-by-side to get the detecting-area multiply, however,
it comes out with a problem that the event signal occurred in the
adjacent area being conducted to two or more imaging detectors. Due
to the independence of the detectors, the incomplete signals of
those triggering detectors result in, as shown in FIG. 8, the
consolidation area crystals can not respond correctly, thus, cause
the entire imaging area be discontinuously separated. The crystal
response map as shown in FIG. 6 is obtained with the technology in
the prior art, as seem, the image is seriously discontinuous and
can not be used in practice.
[0004] To improve the disadvantage described above, the technology
employed in the prior art is to cascade the detector readouts to
get the detector signal sharing between two detectors, since the
signals regain complete, the information of position of the event
occurred in a cross-detector area of two adjacent image detector is
correctly retained, so as to avoid the problem of large area of
image being separated discontinuously. However, such solution cause
the single area of image over-sized and increase the possibilities
of occurrence of multiple events at a same time, result in the
problems of signals being piled-up, increase of Dead Time and
decrease of sensitivity of the imaging probe. In addition, many
series combination of circuit logic in the readouts circuits also
result in the decrease of SNR of the weighted circuit and poor
quality of signal, eventually, cause the poor sensitivities and
poor resolution of the image probe, and further impact the
operation efficiency and quality of the instrument.
[0005] The technology employed in the prior art is to cascade the
detector readouts to get the detector signal sharing between two
detectors, which solve the problem of discontinuity and result in
the destruction of the independence of each detector to become a
larger detector device in series, but cause the problem of increase
Dead Time of imaging probe, decrease SNR, being poor
resolution.
SUMMARY OF THE INVENTION
[0006] The present invention has several unique technical features
as follows.
[0007] (1). It combines several independent imaging detectors into
a large area imaging probe, but still maintain the circuit
independence of each single imaging detector, which means it keeps
the sensitivity of each imaging probe and a higher signal to noise
ratio S/N ratio).
[0008] (2). The crystal response of the entire linage-area (the
probe effective detecting area) is continuous and identical
pixelated, as shown in FIG. 7.
[0009] (3). When in real-time operation, only simple calculation of
addition/multiplication applies, and such calculation can be
implemented in the form of firmware built in a hardware system.
[0010] (4). It will not increase the loading of the software and
the storage of list-mode data, thus decrease the complexity of the
maintenance of the instrument.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention will become more fully understood from
the detailed description given herein below and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention and wherein:
[0012] FIG. 1 is a schematic diagram showing l number of imaging
detectors are combined with respect to the direction of x in an
embodiment of the present invention.
[0013] FIG. 2 is a schematic diagram showing n number of imaging
detectors are combined with respect to the direction of y in an
embodiment of the present invention.
[0014] FIG. 3 is a schematic diagram showing the four intersections
of 1*n number of imaging detectors in an embodiment of the present
invention.
[0015] FIG. 4 is a schematic diagram showing the signal process
flow of the gamma imaging probe for position signal processing
method of the present invention.
[0016] FIG. 5 is a schematic diagram showing the testing
installation of the combination of two image detectors in an
embodiment of the present invention.
[0017] FIG. 6 is a schematic diagram showing the crystal response
map not using the method of the present invention.
[0018] FIG. 7 is a schematic diagram showing the crystal response
map using the method of the present invention.
[0019] FIG. 8 is a schematic diagram showing the area being
expected by the four-combined image detectors in an embodiment of
the present invention.
DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0020] The present invention provides a position signal processing
method for the gamma imaging probe. The gamma imaging probe
disclosed in the method is a combination of a plurality of
independent detectors. Each independent detector has the same
structure of design, in which, each channel of signal is projected
into two directions X and Y by branching or duplication. In X and Y
direction there is L and N number of branch respectively. The
signal branches in each direction are processed with its own weight
model G for the calculation of addition/multiplication to obtain
the two position signal with respect to each direction, that is,
X+X-Y+ and Y-, which can be used to define a rectangle (i.e. the
imaging area of a single imaging detector). Therefore, the weight
model can be formulated as G.sub.X+=[G.sub.1.sup.X+G.sub.2.sup.X+ .
. . G.sub.L.sup.XG.sub.2.sup.X- . . . G.sub.L.sup.X-],
G.sub.Y+=[G.sub.1.sup.Y+G.sub.2.sup.Y+ . . . G.sub.N.sup.Y+], and
G.sub.Y-=[G.sub.1.sup.Y-G.sub.2.sup.Y- . . . G.sub.N.sup.Y-], which
is a necessary condition when practicing the present invention.
[0021] The practice of the present invention comprises two
sections, the first one is the estimation-model built-up section,
and the second one is the application mode section.
[0022] As to the estimation-model built-up section, it comprises
four steps. The first step is to reverse the original signal; the
number of detectors is l when the combination of image detectors
with respect to the X direction, as shown in FIG. 1. The method of
the present invention modifies the event occurred in the
intersection area of the two adjacent image detectors, that is, for
example, the intersection area of the m-th image detector and the
(m+1)-th image detector, wherein, m=1 . . . l-1; that also means,
the signal occurred simultaneously on the m detector in the branch
L and the m+1 detector in the branch l, therefore, the original
signal of tn-th detector in the branch L is
S L X m 0 = X m - G L X - + X m + G L X + , ##EQU00001##
and the original signal of the (m+1)-th detector on the branch l
is
S 1 X m + 1 0 = X ( m + 1 ) - G 1 X - + X ( m + 1 ) + G 1 X + .
##EQU00002##
[0023] The second step is to build up the weight model for the
virtual combined readout circuit, which can be formulated based on
the weight model of the original readout circuit The weight model
of the combined l image detectors can be represented as
G.sub.X.sup.V+=[G.sub.1.sup.X+G.sub.2.sup.X+ . . .
G.sub.L.sup.X+G.sub.(L+1).sup.X+ . . .
G.sub.mL.sup.X+G.sub.(mL+1).sup.X+ . . . G.sub.lL.sup.X+], and
G.sub.X-.sup.v=[G.sub.1.sup.X-G.sub.2.sup.X- . . .
G.sub.L.sup.X-G.sub.(L+1).sup.X-+ . . .
G.sub.mL.sup.X-G.sub.(mL+1).sup.X- . . . G.sub.lL.sup.X-].
[0024] The third step is to estimate the new weighted signal of the
two branches in the virtual circuit, that is, the multiplication of
the weight of the original signal and the weight of the virtual
circuit, Le.
S.sub.mL.sup.X-=.sub.m.sup.0S.sub.L.sup.X.times.G.sub.mL.sup.X-,S.sub.mL-
.sup.X+=.sub.m.sup.0S.sub.L.sup.X.times.G.sub.mL.sup.X+,S.sub.(mL+1).sup.X-
-=.sub.(m+1).sup.0S.sub.L.sup.X.times.G.sub.(mL+1).sup.X-,
S.sub.(mL+1).sup.X+=.sub.(m+1).sup.0S.sub.L.sup.X.times.G.sub.(mL+1).sup-
.X+.
[0025] The forth step is to build up the final position signal of
the virtual combined circuit, which is to estimate the mathematical
formulation of the four position signal in each of the two original
image detectors, wherein, the output signals of the virtual circuit
are X.sup.+, X.sup.-, Y.sup.+ and Y.sup.-, and the output values
from AC/DC converter of two original image detectors are
X.sup.+.sub.m, X.sup.-.sub.m, Y.sup.+.sub.m, Y.sup.-.sub.m,
X.sup.+.sub.(m+1), X.sup.-.sub.(m+1), Y.sup.+.sub.(m+1) and
Y.sup.-.sub.(m+1), and the signal of the virtual circuit with
respect to the combined direction can be formulated as
X.sup.+=S.sub.mL.sup.X+X.sub.(mL+1).sup.X+,X.sup.-=S.sub.mL.sup.X-+S.sub-
.(mL+1).sup.X-
, and the signal of the virtual circuit with respect to the
non-combined direction is the sum of the original signal of the two
original image detector and is formulated as
Y.sup.+=Y.sup.+.sub.m+Y.sup.+.sub.(m+1),
Y.sup.-=Y.sup.-.sub.m+Y.sup.-.sub.(m+1).
[0026] In summary, the formulations in the last three steps, the
new formulation (1) and (2) of the mathematical model for the
estimation-mode built-up section can be obtained. The formulation
(1) and (2) are as follows,
{ X + = R 1 X m - + R 2 X m + + R 3 X ( m + 1 ) - + R 4 X ( m + 1 )
+ X - = R 5 X m - + R 6 X m + + R 7 X ( m + 1 ) - + R 8 X ( m + 1 )
+ Y + = Y m + + Y ( m + 1 ) + Y - = Y m - + Y ( m + 1 ) -
formulation ( 1 ) wherein , [ R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 ] = [
X mL + G L X - X mL + G L X + X ( mL + 1 ) + G 1 X - X ( mL + 1 ) +
G 1 X + X mL - G L X - X mL - G L X + X ( mL + 1 ) - G 1 X - X ( mL
+ 1 ) - G 1 X + ] formulation ( 2 ) ##EQU00003##
[0027] With the same manner described above, when n number of image
detectors are combined with respect to the Y direction, as shown in
FIG. 2, the estimation-model for the event occurred in the
intersection area of the k-th image detector and the (k+1)-th image
detector can be expressed as
{ X + = X k + + X ( k + 1 ) + X - = X k - + X ( k + 1 ) - Y + = R 9
Y k - + R 10 Y k + + R 11 Y ( k + 1 ) - + R 12 Y ( k + 1 ) + Y - =
R 13 Y k - + R 14 Y k + + R 15 Y ( k + 1 ) - + R 16 Y ( k + 1 ) +
formulation ( 3 ) wherein , [ R 9 R 10 R 11 R 12 R 13 R 14 R 15 R
16 ] = [ G mN Y + G N Y - G mN Y + G N Y + G ( mN + 1 ) Y + G 1 Y -
G ( mN + 1 ) Y + G 1 Y + G mN Y - G N Y - G mN Y - G N Y + G ( mN +
1 ) Y - G 1 Y - G ( mN + 1 ) Y - G 1 Y + ] formulation ( 4 )
##EQU00004##
[0028] In a special condition, when the event occurred in the
intersection of any four image detectors, as shown in FIG. 3. In a
image probe formed with l*n image detectors, and the events
occurred in the intersection of the four image detectors by the
columns m and m+1 with respect to the direction X and the rows k
and k+1 with respect to the direction Y, wherein, m=1 . . . l-1,
while k=1 . . . n-1. The estimation-model of the position signals
of the virtual circuit can be expressed as
{ X + = R 1 ( X m - + X ( kl + m ) - ) + R 2 ( X m + + X ( kl + m )
+ ) + R 3 ( X ( m + 1 ) - + X ( kl + m + 1 ) - ) + R 4 ( X ( m + 1
) + + X ( kl + m + 1 ) + ) X - = R 5 ( X m - + X ( kl + m ) - ) + R
6 ( X m + + X ( kl + m ) + ) + R 7 ( X ( m + 1 ) - + X ( kl + m + 1
) - ) + R 8 ( X ( m + 1 ) + + X ( kl + m + 1 ) + ) Y + = R 9 ( Y m
- + Y ( m + 1 ) - ) + R 10 ( Y m + + Y ( m + 1 ) + ) + R 11 ( Y (
kl + m ) - + Y ( kl + m + 1 ) - ) + R 12 ( Y ( kl + m ) + + Y ( kl
+ m + 1 ) + ) Y - = R 13 ( Y m - + Y ( m + 1 ) - ) + R 14 ( Y m + +
Y ( m + 1 ) + ) + R 15 ( Y ( kl + m ) - + Y ( kl + m + 1 ) - ) + R
16 ( Y ( kl + m ) + + Y ( kl + m + 1 ) + ) , formulation ( 5 )
##EQU00005##
wherein, [R.sub.1 R.sub.2 . . . R.sub.8] is same as that in
formulation (2), [R.sub.9 R.sub.10 . . . R.sub.16] is same as that
in formulation (4).
[0029] The second section is the application mode section, which
applies the formulation modules established in the first
section--estimation-model built-up section in the practice of the
probe. As shown in FIG. 4, the first step of the application mode
section is to screening of the events, that is, when the
gamma-event occurred in the probe, the probe generates a trigger
message, position signals and the sum of signals (as the gamma
energy). Ideal situation is that only one image detector in the
probe is transmitting the trigger message, but if the event
occurred in the area cross to the other image detector and needs
modification, more image detectors are transmitting trigger
messages, thus, the modification will proceed based on the image
detector that is transmitting the maximum sum of signals. To
proceed, the ratio X+/X- is established based on the position
signals of the image detector with respect to X direction to
determine whether the ratio is greater than the value T.sub.X+ or
smaller than the value T.sub.X-; T.sub.X+ and T.sub.X- are
determined by the weight of the read-out circuit of each image
detector, wherein, T.sub.X+=G.sub.L-1.sup.X+/G.sub.2.sup.X+,
T.sub.X-=G.sub.L-1.sup.X-/G.sub.2.sup.X-; if X+/X->T.sub.X++ is
true, meaning the cross-detector event occurred with respect to the
X direction. Following the number of position indicating in the
trigger message transmitting from the image detector will lead to
the column m in the image detector array, and the next position
adjacent to the column m with respect to direction X+ is the
(m+1)-th image detector. If X+/X-<T.sub.X- is true, meaning the
cross-detector event occurred with respect to the X direction.
Following the number of position indicating in the trigger message
transmitting from the image detector will lead to the column m+1 in
the image detector array, and the last position adjacent to the
column m+1 with respect to direction X- is the m-th image detector.
Same manner, the ratio Y+/Y- is established for determination,
wherein, T.sup.Y+=G.sub.N-1.sup.Y+/G.sub.2.sup.Y+,
T.sub.Y-=G.sub.N-1.sup.Y-/G.sub.2.sup.Y-; if Y+/Y->T.sub.Y+ is
true, meaning the cross-detector event occurred with respect to the
Y direction. Following the number of position indicating in the
trigger message transmitting from the image detector will lead to
the row k in the image detector array, and the next position
adjacent to the row k with respect to direction Y+ is the (k+1)-th
image detector. If Y+/Y-<T.sub.Y- is true, meaning the
cross-detector event occurred with respect to the Y direction.
Following the number of position indicating in the trigger message
transmitting from the image detector will lead to the row k+1 in
the image detector array, and the last position adjacent to the
column k+1 with respect to direction Y- is the k-th image
detector.
[0030] The second step of the section is, based on the result from
the first step, to modify the event occurred with the formulation
derived from the first section. If the cross-detector event
occurred in the direction X, the formulations (1) and (2) apply,
while the cross-detector event occurred with respect to the
direction Y, the formulations (3) and (4) apply. If the
cross-detector event occurred with respect to the both directions X
and Y, the formulations (5), (2) and (4) apply. If all the
determinations in the first step are not true, meaning no
cross-detector event occurred, the each corresponding position
signal in the probe (image detector array) will be used as the
correct mapping for its relative position in the entire probe,
which is common and obvious in the prior art.
[0031] The last step of the section is to transmit all the position
signals, no matter whether cross-detector or not, to a digital
processor for further process.
[0032] One of the embodiments according to the present invention is
illustrated in FIG. 5, in which, two image detectors (Det. A &
Det. C) are combined with respect to the direction X, each image
detector has its own independent read-out circuit. In the direction
X, there are 16 branches signals (L=16), while in the direction Y,
there are 12 branches signals (N=12). Four position signals X+, X-,
Y+, Y- for each detectors are built up by the combination based on
the weight model of each direction, wherein, the weight model of
the direction Y is
G.sub.y.sup.+=[0.511.522.533.544.555.56]G.sub.y.sup.-=[65.554.543.532.521-
.510.5], and the combined row is k=1 (i.e. Det A) and (k+1)=2 (i.e.
Det C)
The weight model of the virtual combined circuit can be
G.sub.Y+.sup.v==[0.511.522.533.544.555.566.577.588.599.51010.51111.512],
G.sub.Y-.sup.v=[1211.51110.5109.598.587.576.565.554.543.532.521.510.5].
Therefore, the model of the estimated position signals of the
virtual circuit established based on the eight position signals
X.sub.1.sup.+, X.sub.1.sup.-, Y.sub.1.sup.+, Y.sub.1.sup.-,
X.sub.2.sup.+, X.sub.2.sup.-, Y.sub.2.sup.+, Y.sub.2.sup.- of the
Det.A and Det.C can be expressed as follows,
{ X + = X 1 + + X 2 + X - = X 1 - + X 2 - Y + = 12 Y 1 - + Y 1 + +
1.0833 Y 2 - + 13 Y 2 + Y - = 13 Y 1 - + 1.0833 Y 1 + + Y 2 - + 12
Y 2 + ##EQU00006##
[0033] As shown in FIG. 5, there are two adjacent crystal arrays
formed in the intersection area of two image detectors, as seem in
the diagram, the crystals in the intersection area of the two image
detectors did not respond correctly without employing the present
invention, which causes the utilization lost of the signals, as
shown in FIG. 6. However, after employing the present invention,
the crystals lying in the intersection area of the two image
detectors are perfectly correct and thus a continuous and
resolution-identical image is produced.
[0034] With respect to the above description then, it is to be
realized that the optimum dimensional relationships for the parts
of the invention, to include variations in size, materials, shape,
form, function and manner of operation, assembly and use, are
deemed readily apparent and obvious to one skilled in the art, and
all equivalent relationships to those illustrated in the drawings
and described in the specification are intended to be encompassed
by the present invention.
* * * * *