JPS61170438A - Method for forming and regenerating three-dimensional observation hologram of internal structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing and reproducing a hologram that stereoscopically visualizes the internal structure of a subject. The present invention relates to a method for producing and reproducing a hologram that can be reproduced as a clear three-dimensional image regardless of differences.

[Background of the invention]

CT (compute) is a medical technology that visualizes the internal structure of a subject, especially the internal structure of the human body.
The technology (raised X-ray tomogram) has made great progress, and with this technology, the internal structure of a subject, such as a human head, can be visualized in a predetermined cross-section using X-rays without cutting the head. It can be visualized as a line image. By producing a large number of such so-called tomographic photographs, the internal structure of the human body can be diagnosed and analyzed without cutting or incising the body.

However, CT tomography is not fully satisfactory in the following points.

CT tomography is two-dimensional information and cannot provide a three-dimensional view of the internal structure of the subject.

In other words, in order to understand the internal structure three-dimensionally, an extremely large number of OCT tomograms must be created, and by arranging and observing these images in parallel, the observer mentally visualizes the internal structure of the subject in three dimensions. It is only a virtual three-dimensional structure.

Therefore, the relativity between each fault is completely unknown.

In order to convert the internal structure of the subject into three-dimensional information using such CT tomograms and enable accurate stereoscopic viewing, the applicant has combined CT technology and holography technology to convert the internal structure of the subject into three-dimensional information. Developing original regeneration technology,
This technique is disclosed in Japanese Patent Application Laid-Open No. 53-95657 as "Method for producing a hologram for stereoscopic visualization of cross-sectional images." According to this method, a plurality of CT tomograms can be multiplexed to form a single method, so by reproducing this method, it is possible to observe a plurality of tomographic structures of a plurality of objects at the same time. In other words, since the internal structure of the subject can be visualized in three dimensions, the relativity between the respective toms can be observed and understood with great accuracy.

The combination of this holography technology has enabled stereoscopic viewing of the internal structure of a subject, and has made a major contribution to medical technology.
Due to the characteristics of visual tomography, the following problems still remain.

That is, when a conventional holographic CT tomogram is reproduced, it is difficult to stereoscopically view the entire structure of the subject due to differences in tissue. For example, in the case of the human body, it is difficult to simultaneously regenerate hard tissue and soft tissue, specifically, hard tissue, which is bony tissue, and soft tissue, such as the brain parenchyma, at the same time. This is due to the fact that a CT tomogram is an X-ray image based on the absorption coefficient of tissue or the intensity of transmitted X-rays in a scanned tomography using X-rays. There is a slight difference in absorption coefficient or transmittance for X-rays between hard tissue and soft tissue, and therefore it is not possible to simultaneously form a gradated X-ray image of hard tissue and soft tissue within the same cross section. In order to form a head CT photograph, when obtaining an image tone in which the bony parts can be identified, the brain parenchyma, which is soft tissue, becomes completely black and cannot be identified. Later, if an attempt is made to obtain an image tone that is distinguishable from the brain parenchyma, the bony part, which is soft tissue, becomes completely white and cannot be identified. In conventional hologram reconstruction images produced using OCT tomography of the internal structure of a subject with such tissue differences, it is extremely difficult to observe a clear three-dimensional structure. Furthermore, from a medical perspective, it is desired that the following aspects of the internal structure can be observed from a single hologram; (3) Either the entire structure inside the subject can be viewed stereoscopically, or it is possible to emphasize one of the tissues for stereoscopic viewing.

Among these observation modes, mode (1) has been possible until now, although it is incomplete, but mode (2) and (3)
is completely impossible. Therefore, especially from a clinical medical point of view, conventional three-dimensional holograms are not fully satisfactory.

[Purpose of the invention]

In view of the above-mentioned unsatisfactory circumstances of conventional stereoscopic visualization holograms of cross-sectional images, the present invention provides a method for producing and reproducing a hologram that is particularly useful in clinical medicine and allows stereoscopic visualization of the internal structure of a subject in various observation modes. The purpose is to provide the following.

[Structure of the invention]

The method for producing a hologram of the present invention roughly consists of the following process.

(1) Scanning and forming a CT tomogram with gradation only for a specific tissue of the subject on multiple cross-sections; (2) Forming a CT tomogram with gradation only on other specific tissues of the subject on multiple cross-sections (3) The plurality of CT tomograms formed in process (1) are sequentially converted into holograms so that the correlation between these tomograms corresponds to the correlation between the scanned sections of the object to form a multiplex hologram; (4) Process Multiple holograms are created by converting the multiple CT tomograms formed in step (2) into holograms in the same manner as in process (3), but separating the reference light directions and sequentially converting them into holograms on the same hologram plate. Form.

The hologram thus formed is a composite hologram of two different specific tissues with respect to the reference beams in two directions.

The multiplexed hologram formed by the above process is reproduced as follows.

The multiplexed hologram is irradiated with reference light from two directions separated by the same irradiation angle as the reference row irradiation angle at the time of forming the hologram. If the hologram is reproduced by using reference beams from both directions with approximately the same intensity, reconstructed images of two specific tissues will be simultaneously reproduced, and the composite structure of both tissues can be viewed in 3D. By blocking one of the reference beams, only the reconstructed image of the specific tissue reproduced by the other reference beam can be viewed stereoscopically. Furthermore, by giving a difference in the intensity of the reference light, a composite structure of both tissues can be viewed stereoscopically, and in the composite structure, one tissue structure can be emphasized and viewed stereoscopically.

In the present invention, when there are multiple tissue structures to be identified, the irradiation direction of the reference light during hologram formation and reproduction may be separated into multiple directions, and the present invention is not limited to two different tissue structures. do not have. Furthermore, tomography is applicable not only to CT photography but also to all other tomography images in which a tomographic image with gradation cannot be obtained unless the images are separated.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 provides an overview of a CT tomogram in which the subject is a human head. As is well known, in CT tomography, when attempting to create an X-ray image of a certain cross section of a subject, that is, a human head, X-rays are irradiated from around a virtual cross section of the head and scanned 180° or 360'. Do the following. During this 1800" or 360" scanning process, the absorption coefficient or transmitted X-ray intensity is measured, and the obtained data is combined to form an X-ray image of the cross section, which is then photographically recorded. This is called a tomogram.The human head is mainly composed of the bony part, which is hard tissue, and the parenchymal part, which is soft tissue, and the CT tomogram PA has gradation in the bony part.

As shown in Figure 1 (B), the brain parenchyma P2 and the background P3 are completely black (represented by diagonal lines), while in the CT tomogram PB, where the brain parenchyma P2 has gradation. As shown in FIG. 1(C), the bony part P1 is cut off into a white area (represented by a white background) roughly along its outline. This is because each tissue has different absorption or transmission characteristics for l.

Therefore, as CT tomograms used to produce the hologram according to the present invention, a plurality of OCT tomograms related to the bony region were prepared at each required scanning position A, ~A7, and a plurality of OCT tomograms related to the brain parenchyma were prepared. is produced for each required scanning position B1 to B6. These CT tomograms are written as PA, PB, and 1 in correspondence with the scanning positions. CT tomograms PA, -PA, and P obtained in this way
B.

-PB, first of all, a method of converting a photograph PA into a hologram A method of converting a bony part (hard tissue) OCT tomogram PA into a hologram will be explained based on FIG. 2(A). FIG. 2(B) shows an optical system of a hologram production apparatus, which itself is well known. In the figure, laser light from a laser light source 1, which is a coherent light source, is deflected by a reflecting mirror 2 and split into two by a beam splitter 3. One of the divided laser beams is deflected by a reflection mirror 4, and then illuminates the CT tomogram FAI as object illumination L0 by a diverging optical system 5. The object light transmitted through the CT tomography FAI illuminated by the illumination light L0 reaches the hologram plate H. The other laser beam split by the beam splitter 3 is polarized by a reflection mirror 6 and then sent to a diverging optical system 7.
The reference light is diverged by the reference light, and reaches the hologram plate H at a certain angle θ with the object light L0.

As is well known, the hologram plate H7 is a high-resolution photographic plate or film, and has object light.

Interference fringes are recorded at intervals corresponding to the angle formed by the two light waves, ie, the reference beam and the reference beam. Next, CT tomogram PA, CT
The interference fringes associated with the CT tomogram PAt are multiplexed onto the hologram plate HP in exactly the same manner by placing it in the object illumination optical path in exactly the same manner as the CT tomography scan interval with respect to the tomogram PAI. Similarly, CT tomogram PA3 below
-・-PA.

The interference fringes of are recorded multiplexed on the hologram plate T (P) to form a hologram. In this way, a multiplexed hologram of the CTWr@photograph PA, that is, the bony part (hard tissue) is recorded (
The brain parenchyma and background of the CTT layer photograph do not transmit light, so no interference fringes are formed regarding these parts.)

Next, a method for converting the OCT tomogram PB of the brain parenchyma (soft tissue) into a hologram will be explained based on FIG. 2(B). This optical system is in principle exactly the same as the optical system shown in FIG. Diagram (B)
Among them, optical elements having the same reference numerals as in FIG. 2(A) have exactly the same functions. In the figure, number 8 is a reflecting mirror. Using a hologram production apparatus having such an optical system, the hologram plate Hp on which the hologram of the CT tomography photograph PA has been recorded is further subjected to CT scan in exactly the same manner.
The interference fringes of the tomograms PB+, PBz, -.-1PB are sequentially recorded and converted into a hologram. Furthermore, CTltI
When converting the r-layer photograph PB into a hologram, prepare in advance the image shown in Figure 1 (C
) The bony part (hard tissue) indicated by number 1 is made opaque with black paint or the like. This is important in order to remove hologram information other than the brain parenchymal part from the object light. Needless to say, when converting each CTT layer photograph PB into a hologram, it is necessary to ensure a sufficiently accurate relative positional relationship with other CTT layer photographs and place it in the object illumination light.

A method for reproducing the hologram obtained as described above will be explained based on FIG. 3.

FIG. 3 shows the optical system of the hologram reproducing device. Laser light from a laser light source 10, which is a coherent light source, is deflected by a reflecting mirror 1) and split into two by a beam splitter 12, which will be described later. One of the divided laser beams is deflected by reflecting mirrors 13 and 14, and the other is deflected by reflecting mirrors 15, 16 and 17,
Finally, the reference beams LRθ and LRθ' are sent to the hologram plate H by the divergent optical systems 18 and 19, respectively.

It is configured to illuminate. Reference light LRθ and LR
The illumination directions θ and θ′ with respect to the hologram plate are both the reference beam L during hologram recording (Fig. 2).
This coincides with the illumination directions θ and θ′ of 8.

When the hologram plate H7 is illuminated with the reference light LRθ, the diffracted light LD is emitted in a specific direction corresponding to only the interference fringes formed by the same wavefront of the hologram recorded therein. . This diffracted light travels in the same direction as the object beam L0 during hologram recording, so when viewed from behind the hologram, the original object, in this case, the respective CT tomograms PA, , PAz...
..., the wavefront coming out of PA7 is reproduced. CTI
Since the hologram information in the FrJii photo PA is only about the bony part, the tomographic images X of the bony part are overlapped in correspondence with the CT tomography scan intervals, and can be viewed three-dimensionally. In exactly the same way, the tomographic image Y of the brain parenchyma can be viewed three-dimensionally using the reference light LRθ'.

Therefore, the reference beam LRθ is simultaneously applied to the hologram plate H,
When LRθ' is incident, both faults X and Y are synthesized and reproduced. On the other hand, if the laser beam is split by the beam splitter 12 so that one of the reference beams is made stronger and the other is made weaker, one reproduced image will be emphasized and the other reproduced image will be weakened. If the division ratio of the laser beam is further increased, eventually only one tomographic image will be reproduced, and the other tomographic image will not be reproduced at all.

In this way, the following hologram reproduction can be performed depending on the observation form of the internal structure of the human head.

(1) Let the intensity division ratio of the reference light be LRθ#LRθ' (
(2) Set the intensity division ratio of the reference light to LRθ#0 or LRθ'hanawa0 (3D view of the entire structure regardless of tissue differences)
(3) Set the intensity division ratio of the reference light to LRθ≠LRθ' (
The entire structure can be viewed in 3D, but some tissue structures are emphasized for 3D viewing).

In order to implement such a reproduction mode, the beam splitter 12 shown in FIG.
' is provided in the laser optical path so as to be rotatable by 360 degrees. As shown in FIG. 4, this beam splitter 12 is divided into five areas with different split light quantity ratios LRθ/LRθ'. Each area Sl, S2, S8,
The division ratio of S4 and S5 is SI (10010), St
(75/25), S3 (50150), S, (2
5/75) ss (0/100), and the 4th
The laser beam in the figure is reflected light (LRθ)/transmitted light (L
Since the beam splitter section S2 has a division ratio of Rθ') = 75/25, the three-dimensional image of the local layer The 3D image of the section NY is weakened. Therefore, while the entire internal structure of the human head can be viewed in 3D, the bony parts in particular can be separated and viewed as a 3D image with strong contrast. The reproduction mode (
1) to (3) can be freely selected.

In the above embodiments, the case where the tissue structures to be separated are two tissues has been described, but the present invention can be applied to multiple tissues. The resolution of tissue absorption coefficient in a computer is approximately 10 bits (= 2''), while the gradation in an X-ray photograph is approximately 4 to 5 bits, so from this point of view, the number of tissues that can be separated and recorded is 4. However, from the perspective of avoiding the generation of crosstalk images during hologram reproduction, four tissues is the limit.In this case, the irradiation direction of the reference light during hologram production and reproduction must be up and down. It is desirable to separate the left and right sides.

Further, the division ratio of the beam splitter may be changed continuously instead of stepwise.

〔Effect of the invention〕

According to the method for producing and reproducing the stereoscopic visualization direction of an internal structure of the present invention, it is possible to stereoscopically view the internal structure of an object from a tomographic photograph of the object, and also to separate the internal structure for each tissue or to It is possible to emphasize only the structure and see it in 3D.

With this method, it is possible to grasp the internal structure of a living body in a three-dimensional manner, which cannot be cut. Conventionally, it was necessary to virtually synthesize multiple OCT tomograms in one's head to understand and analyze them. It will make more effective use of cutting-edge CT technology and will make an extremely large contribution to clinical medicine.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the scanning position for forming a CTT layer photograph and an overview of the formed tomographic photographs of hard tissue and soft tissue, and FIG. 2 is an explanatory diagram for explaining the method for producing a stereoscopic hologram according to the present invention. FIG. 3 is an optical path diagram for explaining the method for reproducing a stereoscopic hologram according to the present invention,
FIG. 4 is an explanatory diagram of a beam splitter used when reproducing a stereoscopic hologram. 1.10... Laser light source, 2.4.6.8.1)
．． 13.14.15.16.17...Reflection mirror,
3.12... Beam splitter, 7.18.19.
...Divergent lens, L...laser light, LR...
Reference light, Lo...Object light, Pl...Bony part, P
2...Brain parenchyma, PA, PB...CT tomogram.

Claims (3)

[Claims] (1) In a method for creating a stereoscopic hologram in which multiple tomographic images of a structure are sequentially recorded, each tissue structure has different tomographic image formation factors such as absorption coefficients.
A plurality of tomographic image groups are each formed, and each image of the tomographic image group relating to the same tissue structure is sequentially multiplexed as a hologram on a photographic recording material while the relative positions between the images correspond to the relative positions at the time of formation of the images. The reference light irradiation direction at the time of the hologram recording is determined while recording each image of a group of tomographic images related to the same tissue structure and making the relative positions between the images correspond to the relative positions at the time of formation of the images. A method for producing a stereoscopic hologram of an internal structure, comprising sequentially multiplexing holograms on the photographic recording material using reference beams irradiated from different directions. (2) In a multidirectional reproduction method in which multiple tomographic images are sequentially multiplexed and recorded using reference beams irradiated from different directions for each tissue structure of a structure, the reference beam from a single light source is converted into multiple reference beams by a beam splitter. A hologram for stereoscopic visualization of an internal structure characterized by dividing and reproducing a three-dimensional image by irradiating each divided reference beam with multiple holograms from different directions corresponding to the multiple hologram recording for each tissue structure. How to play. (3) A reference beam from a single light source is divided into multiple reference beams with different intensities by a beam splitter, and each divided reference beam is multiplexed for each tissue structure from different directions corresponding to the multiplex hologram recording. 3. The method for reproducing a hologram for stereoscopic visualization of an internal structure according to claim 2, wherein the hologram is irradiated to separate and reproduce three-dimensional images of each tissue structure.