JPS58190787A - Corrector for spatial distortion of scintillation camera - Google Patents

Abstract

PURPOSE:To remove spatial distortion of an image by correcting spatial distortion for position signals in three directions shifted by 120 deg. on real time to be converted to right position signals. CONSTITUTION:In a scintillator 1 which enter gamma ray and other radiations, a number of photo multipliers (PMT) 3 are arranged on the back thereof in such a manner as to be positioned at respective apexes of a regular triangle so that scintillation lights enter each of them through a light guide 2. Outputs of the PMTs 3 corresponding to the scintillation are introduced to a position calculating circuit 4 to calculate position signals alpha, beta and gamma in three directions shifted by 120 deg.. The directions of the signals alpha, beta and gamma are each determined by the array of the PMTs 3. These signals alpha, beta and gamma are pass through a correction circuit 5 to be converted to signals alpha', beta' and gamma' by correction of spatial distortions thereof. The signals alpha', beta' and gamma' thus corrected are converted to X and Y signals with a coordinate conversion circuit 6. Display using these X and Y signals provides an image corrected in the spatial distortion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spatial distortion correction device for a scintillation camera.

Conventionally, devices have been proposed to correct the position signals X and Y of the orthogonal coordinate system in scintillation cameras.
The position signals α, β, and γ in three directions for each 12o0 were calculated using position calculation.

The above correction device cannot be applied to a type of scintillation camera that converts into a Y signal.

This invention provides position signals α, β, and position signals in three directions every 12o0.
We have developed a spatial distortion correction device suitable for scintillation cameras that more effectively and appropriately removes the spatial φ distortion of images by performing real-type spatial distortion correction on γ and then converting it into X and Y signals. 0 to provide
Crystal.

An embodiment of the present invention will be described below with reference to the drawings. In Fig. 1, rH and other radiations are incident on the thin tilator l, and a large number of PM'r (photomultipliers) 3 are connected to the back side of it via a light guide 2, as shown in Fig. 2. Each m is an equilateral triangle as shown.
There are 61 lines arranged at points, and scintillation light is incident on each of them via the light guide 2. Each output of the PMT 3 corresponding to the scintillation rayon is led to a position calculation circuit 4, where it produces 11 signals α and β in three directions every 1200.

γ is calculated. Here, each direction of α, β, and γ is PMT
3 is determined as shown in FIG. 2. This α, β
, r signals are subjected to spatial distortion correction through a correction amount j135 to become cr/, β', r' multiplied signals.

Can be converted to Y signal. Therefore, if the X and Y signals are used to display a handwritten image, an image whose spatial distortion has been corrected will be displayed.

The correction circuit 5 is constructed as shown in FIG. 6 (described later), and the correction coefficients necessary for correction are roughly determined as follows. 1. As shown in Figure 3, parallel ribs) 7
1 is arranged in front of the scintillator 1 so that the direction of the parallel slit 71 is perpendicular to the α direction, and the position signals σ, β, and γ of the parallel slit 7 are extracted, and the data storage device 8 After a sufficient number of position signals have been stored, the correction coefficient is calculated in the correction coefficient metering circuit 9 (the first
(see figure). Specifically, the distribution of γ-ray counts in the α direction when β is constant among the stored position signals is investigated. For example, if β=β0 in FIG. 3, the distribution in the α direction is as shown by the dotted line in FIG. Originally, the position of the beak should be at the center of the slit 71 of the /4 turn 7 as shown by the solid line, but due to spatial distortion it is shifted as shown by the dotted line. Therefore, this deviation amount Δ is obtained and multiplied by sF, and this 1 pressure Δ becomes the β direction displacement vector of the correction amount at the intersection of β0 and the slit 71. Similarly, for example, the γ-direction displacement vector of the correction amount is determined from the α-direction distribution when r=r6. Further, the angle of the slit 71 is changed, for example, perpendicular to the β direction, and the α direction displacement vector of the correction amount is obtained in the same manner. The negative values of each displacement vector obtained in this way are subjected to some processing, and the l-9 value is used as a correction coefficient L. This correction coefficient is applied to the entire prayer area, α, β, and r for the distance between door 1. Valley points separated in the direction, that is, α and β as shown in FIG.

Find all the intersections of parallel lines in the 7' and 3 directions, each perpendicular to r and whose spacing corresponds to the spacing of the slits 71,
This is sent to the correction circuit 5 and stored in the correction coefficient memory 58 (v7@ in FIG. 6). This correction coefficient consists of displacement vectors in three directions α, β, and γ.
, β, γ), and each displacement vector is expressed as α
.

``kβ, will be expressed as Vkr.

The correction circuit 5 corrects the position signal within the triangular area surrounded by the intersections in FIG. 5 by interpolation calculation using the correction coefficients of each vertex of the triangle. Specifically, the configuration is as shown in FIG. 6. First, the α, β, and γ signals obtained for each scintillation scan are AD-converted by ADI converters 51, 52, and 53, and the upper bits, αl, β1, and γ signals are converted into digital signals by ADI converters 51, 52, and 53. Specify the position to the vertex of each triangle using the gate, and input the lower bits α2. β2. Position R within the triangle with γ2
(Ift in Figures 7 and 8).

Here, upper bit α1. β1. Since the interpolation calculation differs depending on whether the sum of γ1 is an even number or an odd number, C1, β1 . The least significant bit of each rl is sent to the even/odd determining circuit 54 for determination. Based on the determination result, the complement calculation circuit 5
5゜56.57 works, and when the number is even, the lower bit α2゜β
2. If r2 is an odd number, its complement 'lx
+/2°·10,000 are respectively sent to the interpolation calculation circuit 59. This interpolation calculation circuit 59 includes upper bits α1. β1
．． and the correction coefficient of each vertex of the triangle surrounding the point P read from the correction coefficient memory 58 using the least significant bit of rl (maximum is rl).
“The next clx C12 obtained from 5Vs (α+β, γ) is being sent, and C1=■lα* C5= v1βI
C9:■lrC2"V2Q-Vlα1C6=■S'/-
V17+' e Cl0=■2γ-■17C3""V2
C, C,: V3β cost C11=V3γC4”v2Q-
V3 (1-C8=■2/ '3β+ Cl2=V2r-
If V3γ is an even number, it will be as shown in Figure 7, and if it is an odd number, it will be as shown in Figure 8, so it is the complement of Rγ (1-R, α, 1-Rβ, 1-Rγ). .

The correction coefficient VR(a, β, γ) at point R is calculated by: The correction amount Δα in each direction of α, β, and γ obtained in this way,
Δβ and Δγ are the original α in adders 60, 61, and 62.
, β, the corrected position signals αI, β added to the r signals
', r' are obtained.

In addition, in the above embodiment, a pattern with parallel slits was used to take pictures for calculating the correction coefficient of each waste, but a pattern in which many fine holes are regularly arranged may also be used.

As described above in the embodiments, according to the present invention, position signals α in three directions every 120° are generated.

Since the spatial distortion is corrected at the β and r stages and converted into X and Y signals of the virtual orthogonal coordinate system, the correction can be performed more directly and the spatial distortion of the image can be effectively removed.

[Brief explanation of drawings]

1st! i! 1 is a block diagram showing the overall configuration of an embodiment of the present invention, FIG. 2 is a schematic diagram showing a PNTF array, FIG. 3 is a schematic diagram showing a pattern of parallel slits, and FIG. 4 is a diagram showing the distribution of 7m counts. 5 is a schematic diagram for explaining each point at which a correction coefficient is determined, and FIG. 6 is a diagram showing a specific example of the correction circuit 5 in FIG. 1. The figure is a diagram for explaining interpolation calculation. l-...Scintillator 2...Light guide 3--
PMT 4...Position calculation circuit 5...Correction circuit 6...Coordinate exchange circuit 7...Pattern
8...Data storage device 9...Complement coefficient calculation circuit 51-53...AD converter 54--Even sand/odd number judgment circuit 55-57...Complement calculation circuit 58--Correction Coefficient memory 59...interpolation calculation circuit 60
~6ri...additional 3I device

Claims (1)

[Claims] (1) A large number of photoelectric converters are arranged on the back side of the scintillator via light kites so that each photoelectric converter is located at each term of an equilateral triangle, and the output of each photoelectric converter is guided to a 5ffiix circuit to generate signals every 120°. Position signals α, β, and r in three directions are calculated, and this position signal α is calculated. In a scintillation camera that converts β and γ using a coordinate conversion circuit to obtain position signals X and Yt in an orthogonal coordinate system, the correction coefficients for each point represented by the position signals α, β, and γ determined in advance are Correction coefficient memory to store and position signals a, β, γ obtained for each scintillation
The correction coefficients for each m point of an equilateral triangle surrounding the area are read out from the correction memory, and an interpolation calculation is performed to obtain the body position signal α. A spatial distortion correction device for a scintillation camera, comprising an interpolation calculation circuit that calculates correction amounts regarding β and γ, and corrects original position signals α, β, and r using the correction amounts expected from the interpolation calculation circuit.