JP2007243256A - Medical image encryption device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a medical image encryption apparatus capable of performing encryption so that recognition of appearance is difficult and varying the degree of disclosure according to a destination.
After extracting an outline of a head image (a) as a partial image, a plurality of encryption areas are set for the extracted image (b) (c). Subsequently, encryption is performed with a different encryption key for each set encryption area, and an encrypted image is obtained (d).
[Selection] Figure 3

Description

  The present invention relates to encryption of medical images taken for diagnosis and the like, and more particularly to a technique for encrypting each individual so as not to be identified.

Conventionally, in order to analyze and diagnose the state of a healthy person and the state of a patient, medical images taken with an MRI apparatus or the like have been used. Such a medical image is taken as a three-dimensional image, and the cross section can be viewed as a two-dimensional image by specifying the position of the cross section (see, for example, Patent Document 1). Recently, for the purpose of comparing patients and healthy persons, and for the purpose of studying cases, medical images are also exchanged at a plurality of medical institutions.
JP 2005-237441 A

  However, since the medical image as described above is a three-dimensional image, if this is a photograph of the head, the outline of the face, the nose, the eyes, etc. can be recognized. There is a problem that an individual shown in a medical image can be identified. On the other hand, a medical institution that has acquired a medical image legitimately has a desire to recognize the person's face in order to confirm whether the medical image to be diagnosed is a photograph of the person. In addition, even when a medical image is handed over to a legitimate medical institution, it is desirable to hide unnecessary parts from the viewpoint of preventing information leakage. It depends on the institution.

  Therefore, the present invention provides a medical image encryption apparatus and a medical image management system that can encrypt the appearance so that it is difficult to recognize the appearance and can vary the degree of disclosure depending on the destination. Is an issue.

  In order to solve the above problems, in the first aspect of the present invention, partial image extraction means for extracting a contour portion as a partial image from a head image obtained by photographing the head, and the extracted partial image as a whole Provided is a medical image encryption apparatus having encryption execution means for performing encryption with an encryption key as an encryption area.

  In the second aspect of the present invention, partial image extraction means for extracting a contour portion as a partial image from a head image obtained by photographing the head, and a plurality of encryption regions from the extracted partial images There is provided a medical image encryption apparatus having encryption area setting means for setting the encryption area and encryption execution means for performing encryption for each of the plurality of set encryption areas with different encryption keys.

  In the third aspect of the present invention, the system includes a management server, which is a server computer that manages medical images, and a user terminal installed in a medical facility, wherein the user terminal stores medical images. Means for designating a requesting condition and means for decrypting the encrypted image received from the management server, wherein the management server uses an encryption key for the encryption area in the medical image. An encrypted image database storing the encrypted image, a decryption key storage unit storing a decryption key for decrypting the encrypted image, and transmitting the encrypted image and the decryption key according to a request from the user terminal A medical image management system having data transmission means is provided.

  According to the medical image encryption apparatus according to the first aspect of the present invention, the contour portion is extracted as a partial image from the head image, and the entire extracted partial image is encrypted as an encryption area with the encryption key. Therefore, it is possible to conceal the human appearance so that it is difficult to recognize.

  According to the medical image encryption apparatus according to the second aspect of the present invention, the contour portion is extracted from the head image as a partial image, and a plurality of encryption areas in the extracted partial image are encrypted with different encryption keys. Therefore, it is possible to conceal a contour portion that can recognize the appearance of a person step by step.

  Further, according to the medical image management system of the present invention, the encrypted image encrypted with a different encryption key is recorded in each encrypted area, and the decryption for decrypting the encrypted image is performed. Since the key is stored in association with each user terminal, the encrypted image is transmitted according to the request from the user terminal, and the decryption key corresponding to the user terminal is transmitted. Accordingly, the degree of disclosure can be varied.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
(System configuration)
FIG. 1 is a configuration diagram showing an embodiment of a medical image encryption apparatus and a medical image management system according to the present invention. In FIG. 1, 10a to 10c are user terminals, 20 is a network, 100 is a management server, 110 is an image database (hereinafter referred to as image DB), 120 is a decryption key storage unit, 130 is a partial image extraction unit, and 140 is Encryption executing means 150 is a data communication means.

  The user terminal 10 is a terminal device that receives and decrypts an encrypted image from the management server 100 via the network 20 and displays an image obtained by the decryption. As the user terminal 10, a computer installed in a medical facility can be used, and this is realized by installing software for performing decryption processing on such a computer.

  The management server 100 is a server computer having a function of encrypting a taken medical image, a function of managing encrypted data, and a function of transmitting the encrypted data to the user terminal 10 that has requested it. The image DB 110 is a database that records captured medical images and stores encrypted images obtained by encrypting the medical images.

  The decryption key storage unit 120 stores a decryption key for decrypting the encrypted part. The partial image extraction unit 130 has a function of extracting a contour image from a medical image as a partial image. The encryption execution unit 140 has a function of encrypting the partial image extracted by the partial image extraction unit 130. The data communication unit 150 performs data communication with the user terminal 10 such as a function of transmitting an encrypted image in response to a request from the user terminal 10 and a function of transmitting a decryption key according to the user terminal 10. It has a function. Each means in the management server 100 is actually realized by installing dedicated software on a server computer constituting the management server 100. The central function of the medical image encryption apparatus is performed by the partial image extraction unit 130 and the encryption execution unit 140 in the management server 100.

(Encryption processing)
Next, the processing operation of the medical image encryption apparatus shown in FIG. 1 will be described. The medical image means images of various parts of the human body. In the present embodiment, a case where a head image is handled will be described as an example. First, a head is imaged using an imaging means for medical images such as X-rays, ultrasound, MRI, and CT to obtain a three-dimensional head image. And this head image is registered into image DB110.

  The head image in the image DB 110 is recorded as a set of pixel values in a three-dimensional space. By specifying any one of x, y, and z, a cross-sectional image of the head can be obtained. Here, for the head image, any value of x, y, z is specified to extract a plurality of all cross-sectional images, and the following processing is performed on each cross-sectional image. Here, a case where z is specified will be described as an example.

  First, the partial image extraction unit 130 detects the edge of the contour portion of the head image using a 3D filter. Here, FIG. 2A shows the state of the cross-sectional image whose edge is detected. Then, noise removal is performed to eliminate isolated points due to noise or the like. FIG. 2B shows a state where noise is removed from the cross-sectional image shown in FIG.

  Subsequently, the start point coordinate position in the cross-sectional image from which noise has been removed is obtained. Specifically, scanning is performed in the X-axis direction with (x, y) = (0, 0) at the edge of the image area as the starting point of scanning, and a coordinate position in contact with the head contour is first acquired and scanned. Are repeated in the Y-axis direction. Whether or not it touches the contour is determined by the luminance value of the pixel. Specifically, a place where the pixel value of the background of the image area has greatly changed is determined as the contour. Further, scanning similar to the above is performed starting from the opposite direction (x, y) = (Xmax, 0). Thereby, the xy coordinate value of the acquired outline is obtained. FIG. 2C shows how the coordinate value of the contour portion is detected.

  Next, contour extraction processing is performed. For example, when the thickness of the skull is assumed to be 10 mm (mm), only the image corresponding to the thickness corresponding to 10 mm is extracted as a partial image from the acquired coordinate position of the contour portion. As a result, the appearance of the contour image extracted as a partial image is shown in FIG.

  Subsequently, the encryption execution unit 140 performs a process of encrypting the extracted partial image. In the partial image encryption, not all the extracted partial images are subjected to the same encryption process, but an encrypted area that is an area to be actually encrypted is determined from the extracted partial images. In this embodiment, one pixel is left as it is for every three pixels, and two pixels are encrypted for three pixels. For example, consider a case where a partial image is extracted from a cross-sectional image as shown in FIG. For convenience of explanation, here, explanation will be made using a part of pixel group in the extracted partial image. FIG. 3B shows a pixel group of 3 × 7 pixels extracted as a partial pixel group in the partial image. In this embodiment, for such a pixel group, the encryption area is set at a ratio of 2 pixels to 3 pixels. These encrypted areas are encrypted with three different encryption keys A, B, and C. Data encrypted with the encryption keys A, B, and C can be decrypted with the corresponding decryption keys A ′, B ′, and C ′, respectively. As a specific method of encryption, various known methods can be used. As a result of the encryption, the pixel group becomes as shown in FIG. In FIG. 3 (d), the shaded portion indicates an encrypted pixel, and the difference in the mesh pattern indicates that encryption is performed with a different encryption key.

  In this way, an encrypted image obtained by encrypting the contour portion which is a partial image is obtained. Since this encrypted image is obtained by encrypting the contour portion so that the appearance cannot be determined, no encryption is performed inside the head image such as a brain image. Such an encrypted image is registered in the image DB 110 in association with information such as the patient's name, patient ID, photographing date, patient's date of birth, age, sex, and disease name.

(Use at each medical facility)
In each medical facility, when a medical image is required, conditions such as a disease name, age, and sex are specified, and a medical image is requested from the user terminal 10 to the management server 100. The management server 100 searches the image DB 110 based on the received conditions, and extracts a corresponding medical image. Then, the extracted medical image is transmitted to the requesting user terminal 10. In the user terminal 10, when the received encrypted image is displayed as it is, since it remains encrypted as in the pixel group shown in FIG. 3D, correct display is not performed. In order to display the image correctly, the user terminal 10 requests the management server 100 for a decryption key.

  When receiving a request for a decryption key from the user terminal 10, the management server 100 extracts a decryption key corresponding to the requesting user terminal 10 from the decryption key storage unit 120 and sends the decryption key to the requesting user terminal 10. Send. For example, it is assumed that a decryption key correspondence table as shown in FIG. 4 is stored in the decryption key storage unit 120. In FIG. 4, it is assumed that terminal IDs 001 to 003 are terminal IDs of the user terminals 10a to 10c, respectively. In this case, the decryption key A ′ is transmitted to the user terminal 10a, the decryption key A ′, the decryption key B ′, and the decryption key C ′ are transmitted to the user terminal 10b, and the decryption key A is transmitted to the user terminal 10c. 'And the decryption key C' are transmitted.

  The user terminal 10 decrypts the already received encrypted image using the received decryption key. As a result, the decoded image is displayed. For example, since the user terminal 10a performs decryption with the decryption key A ′, a pixel group in a state as shown in FIG. 5B is obtained, and the user terminal 10b obtains the decryption key A ′ and the decryption key B ′. Since the decryption is performed using the decryption key C ′, a completely original pixel group as shown in FIG. 5C is obtained. In the user terminal 10c, decryption is performed using the decryption key A ′ and the decryption key C ′. As a result, a pixel group in a state as shown in FIG. 5D is obtained.

(Modification)
Next, a modified example of the present invention will be described. In the above-described embodiment, the contour image of the entire head image is extracted as the partial image, but it is also possible to extract a partial contour image of the head image. In this case, a state in which the three-dimensional head image is projected from the front is displayed on the screen of the management server 100. Then, the user directly designates a part to be hidden. This is performed by designating a rectangular area on the screen using, for example, a mouse. The screen state at this time is shown in FIG. This screen is a two-dimensional image on the xz plane in which y is specified in the three-dimensional image specified by the coordinates of x, y, and z.

  Subsequently, the partial image extraction unit 130 detects the edge of the contour portion of the head image using a 3D filter. However, here, the x and z values are specified within a specified range, and only the y value is changed.

  Subsequently, the start point coordinate position in the image from which noise has been removed is obtained. Specifically, scanning is performed in the y-axis direction with y = 0 at the end of the image region as the starting point of scanning, and a coordinate position in contact with the head contour is first acquired. Whether or not it touches the contour is determined by whether or not the luminance value of the pixel has changed significantly from the luminance value of the background of the image area.

  Next, contour extraction processing is performed. For example, when the thickness of the skull is assumed to be 10 mm (mm), only the image corresponding to the thickness corresponding to 10 mm is extracted as a partial image from the acquired coordinate position of the contour portion. Here, 10 mm worth of pixels are extracted in the y coordinate. As a result, the appearance of the contour image extracted as a partial image is shown in FIG. A region surrounded by a line in FIG. 6B is a portion extracted as a partial image.

  Next, a modification of encryption will be described. For example, assume that a partial image as shown in FIG. In FIG. 7A, one square represents one pixel, and numerals 1 to 43 are numbers for specifying the pixels and the pixel values of the original image.

  Subsequently, the encryption execution unit 140 determines an encryption area. In the example of FIG. 7, 15 pixels out of 16 pixels are encrypted while leaving 1 pixel out of 16 pixels. Here, FIG. 7B shows the classification of the encryption area and the other areas. 7B to 7E show the pixels shown in FIG. 7A arranged in a horizontal row for convenience. In FIG. 7B, “N” above the pixel indicates an unencrypted area, and “A” indicates an encrypted area with the encryption key A.

  Then, the encryption execution unit 140 encrypts the encryption area with the encryption key A. Data encrypted with the encryption key A can be decrypted with the corresponding decryption key A ′. As a result of the encryption, the pixel group becomes as shown in FIG. In FIG. 7C, a shaded portion indicates an encrypted pixel.

  The user terminal 10 receives the received pixel group and performs processing to display it on the screen. At this time, for the encrypted pixel, processing to display the previous pixel value is performed. Therefore, when the pixel group shown in FIG. 7C is displayed, it is displayed in a state as shown in FIG. When the decryption key A ′ is acquired, it is possible to display in a state as shown in FIG. 7E by decrypting the encrypted pixels.

  A case where a plurality of encryption keys are used in the encryption modification will be described with reference to FIG. FIG. 8A shows the extracted partial image, which is exactly the same as FIG. 7A. The encryption execution unit 140 determines an encryption area in this partial image. In the example of FIG. 8, 15 pixels out of 16 pixels are encrypted in the same manner as in the example of FIG. 7, but 3 pixels out of 15 pixels to be encrypted are further encrypted with different encryption keys. Here, a plurality of encrypted areas and other areas are shown in FIG. 8B. FIG. 8B to FIG. 8E show the pixels shown in FIG. Are arranged. In FIG. 8B, “N” above the pixel indicates a non-encrypted area, “A” indicates an encryption key A, and “B” indicates an encryption area based on the encryption key B.

  Then, the encryption execution unit 140 encrypts each encryption area with the encryption key A and the encryption key B, respectively. Data encrypted with the encryption key A can be decrypted with the corresponding decryption key A ′, and data encrypted with the encryption key B can be decrypted with the corresponding decryption key B ′. As a result of the encryption, the pixel group becomes as shown in FIG. In FIG. 8C, shaded portions indicate encrypted pixels. Note that light shading corresponds to the encryption key A, and dark shading corresponds to the encryption key B.

  As described above, the user terminal 10 performs processing for receiving the received pixel group and displaying it on the screen. At this time, for the encrypted pixel, processing for displaying the previous pixel value is performed. Do. For this reason, when the pixel group shown in FIG. 8C is displayed, it is displayed in a state as shown in FIG. When the decryption key A ′ is acquired, the pixel encrypted with the encryption key A can be decrypted. Therefore, for the pixel encrypted with the encryption key B, the immediately preceding decrypted pixel value Process to display. For this reason, it is displayed in a state as shown in FIG. Furthermore, when the decryption key B ′ is acquired, all the encrypted pixels can be decrypted, so that it is possible to display in a state as shown in FIG.

  As described above, the area to be encrypted is divided into a plurality of areas, each area is encrypted with a different encryption key, and an encrypted image is transmitted to each user terminal in response to the request. By transmitting the one corresponding to the user terminal, the level that can be decoded by the user terminal differs. Therefore, by sending a different key for each medical institution where the user terminal is installed, it is possible to completely decrypt it for medical institutions that need to disclose everything for medical treatment, etc. However, for medical institutions that do not need to disclose all, only a part of the information can be decrypted in order to prevent personal information from being unnecessarily leaked. In particular, parts such as eyes, nose, and mouth that are easy to recognize an individual are judged from the content of the treatment, and are not decoded when unnecessary.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made. For example, in the above embodiment, the management server 100 includes the partial image extraction unit 130 and the encryption execution unit 140 to serve as a medical image encryption device. However, the user terminal 10 performs the partial image extraction unit 130. In addition, by providing the encryption execution means 140, it may serve as a medical image encryption apparatus. In this case, the user terminal 10 transmits the encrypted image and the decryption key to the management server 100, and the management server 100 registers the received encrypted image in the image DB 110 and the received decryption key as a decryption key storage unit. Register at 120.

It is a block diagram which shows one Embodiment of the medical image encryption apparatus and medical image management system which concern on this invention. It is a figure which shows the mode of the process which extracts an outline from a brain cross-sectional image. It is a figure which shows a mode that the extracted image is encrypted. 6 is a diagram showing a decryption key correspondence table in a decryption key storage unit 120. FIG. It is a figure which shows the mode of the decoding of the encrypted pixel group. It is a figure which shows the mode of a process in the case of extracting the one part outline image of a head image as a partial image. It is a figure which shows the mode of a change of the pixel group in the case of one encryption key. It is a figure which shows the mode of the change of a pixel group in case there are two or more encryption keys.

Explanation of symbols

10a to 10c ... user terminal 20 ... network 100 ... management server 110 ... image DB (database)
DESCRIPTION OF SYMBOLS 120 ... Decryption key memory | storage part 130 ... Partial image extraction means 140 ... Encryption execution means 150 ... Data communication means

Claims (5)

Partial image extraction means for extracting a contour portion as a partial image from a head image obtained by photographing the head;
Encryption executing means for performing encryption with an encryption key using the entire extracted partial image as an encryption area;
A medical image encryption apparatus comprising: Partial image extraction means for extracting a contour portion as a partial image from a head image obtained by photographing the head;
An encryption area setting means for setting a plurality of encryption areas from the extracted partial images;
Encryption execution means for performing encryption with different encryption keys for each of the plurality of set encryption areas;
A medical image encryption apparatus comprising:   The medical image encryption apparatus according to claim 1, wherein the encryption setting unit sets the respective encryption areas with a predetermined pixel number interval. A system comprising a management server, which is a server computer for managing medical images, and a user terminal installed in a medical facility,
The user terminal has means for designating a condition for requesting a medical image and means for decrypting the encrypted image received from the management server,
The management server
An image database that records an encrypted image encrypted with an encryption key for an encrypted area in a medical image;
A decryption key storage unit that stores a decryption key for decrypting the encrypted image;
Data transmission means for transmitting an encrypted image and a decryption key in accordance with a request from the user terminal;
A medical image management system comprising: The image database records encrypted images encrypted with different encryption keys for each of a plurality of encrypted areas in a medical image,
The decryption key storage unit stores a decryption key for decrypting the encrypted image in association with each user terminal,
5. The medical use according to claim 4, wherein the data transmission means transmits an encrypted image according to a request from the user terminal and transmits a decryption key corresponding to the user terminal. Image management system.

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