JP2772027B2 - Image reconstruction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention performs back-projection interpolation calculation by a plurality of back-projection blocks when reconstructing an image based on acquired data obtained by a CT scan. The present invention relates to an image reconstruction method that performs multiplex processing, and more particularly, to an improvement of the multiplex processing method.

(Prior Art) A conventional image reconstructing apparatus to which this kind of image reconstructing method is applied performs parallel processing of different lines of the same projection in order to multiplex the backprojection interpolation calculation.

For example, as shown in FIG. 3, each back projection block (BP block) includes a back projection input memory (BIM) and a local memory (L).
M). Then, in each BP block, every time the data from the centering calculation unit (CENT) is received by BIM, the same line of different projection is calculated, and the sum is performed on the LM to write on the image memory (IM). Was to do. In this case, as shown in FIG. 4, the projections (PROJ1 to PROJ1) are transferred to the IM address corresponding to the coordinates on the image calculated in the BP block.
JN) is cumulatively added and multiplexed. The third
In the figure, A indicates an address, and D indicates data.

(Problems to be Solved by the Invention) However, in the case of multiplex processing such as the conventional image reconstruction method of this type, it is necessary to provide a dedicated LM for each BP block and temporarily save data by using this LM. For this reason, the capacity of the LM limits the number of multiplexes and the processing unit. In addition, there is an inconvenience in the circuit configuration, such as the necessity of an adder in each BP block, and the necessity of a relatively large capacity of the BIM for storing the pre-BP data. In addition, it is necessary to temporarily store the calculation result in the BP block in the LM and then accumulate the calculated value for each same point in each projection. Was.

The present invention has been made in view of such circumstances, and its purpose is to simplify the circuit configuration of an arithmetic unit that performs multiplexing of BP interpolation calculations and greatly reduce the processing time of the multiplexing processing. It is an object of the present invention to provide an image reconstruction method capable of performing the above-mentioned operations.

[Configuration of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a BP interpolation operation using a plurality of BP blocks when reconstructing an image based on acquired data obtained by a CT scan. In the image reconstruction method of performing multiplex processing, the multiplex processing is performed by cascade-connecting the respective BP blocks, performing pipeline parallel processing on the same line of different projections, and accumulative addition at the same time. It is assumed that.

(Operation) With the image reconstruction method according to the present invention, the BP multiplexing direction is the projection direction, so that the LM after the BP calculation, which was conventionally required, can be omitted, and the same BP is a different line. Since the BIM requires only a storage capacity for one projection, the arithmetic unit can have a simpler configuration than the conventional one. Furthermore, the cycle of the cumulative addition can be incorporated into the pipeline processing as a BP block, so that the time of the cumulative addition can be apparently omitted.

(Embodiment) FIG. 1 is a block diagram schematically showing an image reconstruction unit in an X-ray CT scanner according to an embodiment to which the image reconstruction system of the present invention is applied.

The image reconstruction unit in this embodiment includes a centering operation block 1 and a centering output memory (COM) for performing image reconstruction by a direct method, in particular, a centering back projection method.
2, a BP calculation control unit 3, a BP calculation unit 4, and an IM5.

The centering calculation unit 1 performs calculation processing for centering collected data from an X-ray detector (not shown), and sequentially stores the processing results in COM2.

The BP calculation control unit 3 sends an instruction signal (I signal) to the BP calculation unit 4 in response to a control signal from a host CPU (not shown), and controls the BP calculation unit 4.

The BP calculation unit 4 includes a plurality of BP blocks 6
The block 6 includes a BIM 7, a BP operation circuit 8, and a shift register 9.

Here, the BIM 7 receives the centering data once stored in the COM 2 together with the address of the centering operation block 1, and can exchange data with the BP operation circuit 8 according to the address from the BP operation circuit 8.

The BP operation circuit 8 executes a BP operation based on the centering data from the BIM 7. The BP operation circuit 8 is cascaded between the BP blocks 6, while the I signal from the BP operation control unit 3 is shifted by a shift register. 9, a circuit for pipeline parallel processing which is sequentially shifted and received. Then, the address (A) from the BP operation circuit 8 in the final stage is added to IM5 via the shift register 10 and the selector 11, and the result D of the BP operation of the same line in a different projection is added to the adder together with the address (A).
It is intended to be added to IM5 via 5a.

Therefore, in the BP calculation unit 4, pipeline parallel processing is performed on the same line of different projections, and the parallel processing is simultaneously performed. As shown in (1), multiplexing is performed on the same line through each projection (PROJ1 to PROJN).

As described above, by cascading the BP blocks 6 and setting the BP multiplexing direction to the projection direction, the output of the previous stage can be added in real time at the next stage. LM can be omitted, and the BIM 7 can have a storage capacity for one projection. Moreover, since the cycle of the cumulative addition is also incorporated in the processing of the pipeline, the time is apparently omitted.

[Effects of the Invention] As described above, the image reconstruction method of the present invention performs cascade connection between a plurality of BP blocks, performs pipeline parallel processing on the same line of different projections, and performs cumulative addition at the same time. Since the BP interpolation operation is multiplexed, the circuit configuration of the operation unit that multiplexes the BP interpolation operation can be simplified. In addition, there is an advantage that the processing time of the multiplexing process can be apparently significantly reduced as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing an image reconstructing unit in one embodiment of the present invention, FIG. 2 is a schematic diagram showing a multiplexing state in one embodiment of the present invention, and FIG. FIG. 4 is a block diagram schematically showing a conventional image reconstructing unit, and FIG. 4 is a schematic diagram showing a conventional multiplexing state. 1 centering calculation block 2 centering output memory (COM) 3 back projection (BP) calculation control unit 4 back projection (BP) calculation unit 5 image memory (IM) 6 …… Back projection block (BP block) 7 …… Back projection input memory (BIM) 8 …… Back projection (BP) arithmetic circuit 9,10… Shift register 11 …… Selector

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) A61B 6/03

Claims (1)

(57) [Claims] 1. An image reconstruction method for multiplexing a back projection interpolation operation by using a plurality of back projection blocks when reconstructing an image based on acquired data obtained by a CT scan, comprising the steps of: An image reconstruction method, wherein the multiplexing process is performed by cascade-connecting, performing pipeline parallel processing on the same line of different projections, and simultaneously performing cumulative addition.