JP2006000203A - Display method of test pattern, and medical image displaying apparatus and its program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the precision of visibility of an operator to execute a calibration more precisely by the visual observation of the operator. <P>SOLUTION: When a control section 11 makes a display section 13 display N-pieces test patterns, it makes one pattern to be switched and displayed on one screen respectively. Also, the control section changes the size of each display region which forms the test pattern corresponding to the size of the display screen so that the ratio of an area of the display region in which the driving level divided into N-pieces equal parts is set to an area of the other display region is 7:3, that is, the area of the display region displayed with the low intensity level becomes larger, and makes the test pattern with the changed size display on the whole display screen of the display section 13. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a test pattern display method, a medical image display device for displaying a test pattern, and a program for use in correcting display gradation characteristics of a medical image display device by visual observation by an operator.

  In the medical field, monitor diagnosis in which a patient's medical image obtained by various examination imaging such as X-ray imaging, MRI (Magnetic Resonance Imaging) imaging, ultrasonic imaging, etc. is displayed on a monitor for interpretation is widespread. . In addition, with the development of networks inside and outside hospitals, it is possible to interpret the same image on monitors at different locations. However, if the monitor used for interpretation is of different types such as LCD (Liquid Crystal Display), CRT (Cathode Ray Tube), etc., the display characteristics will be different, so the same image will look different, and even the same type of monitor The appearance of the image may still differ depending on the degree of deterioration due to its use and the installation environment.

  In this way, if there are variations in the appearance of images on individual monitors, the diagnostic accuracy will be affected. Therefore, correction of display tone characteristics (hereinafter referred to as calibration) is performed to change the appearance of images on each monitor. It is necessary to unify. Conventionally, calibration is performed using a luminance meter. However, since the luminance meter is generally expensive, calibration using the luminance meter is expensive. In addition, when there are a number of monitors for image interpretation, the work of calibrating each monitor with a luminance meter one by one is very troublesome and complicated.

On the other hand, a method is also proposed in which an operator visually confirms a calibration result after performing calibration using a luminance meter (see, for example, Patent Document 1). As shown in FIG. 10, the calibration method described in Patent Document 1 displays a plurality of test patterns displayed at different brightness levels on a monitor, and displays the brightness of each test pattern to an operator (observer). The level is confirmed visually.
JP-A-11-327501

  However, as shown in FIG. 10, when calibration is performed by displaying a plurality of test patterns on one screen, the adjacent test pattern together with the test pattern to be determined enters the operator's field of view. As a result, it becomes difficult to perform accurate calibration.

  An object of the present invention is to improve the accuracy of visual recognition by an operator and make it possible to perform calibration by visual observation of the operator more accurately.

The invention according to claim 1 is a test pattern display method,
A test pattern display method for displaying a plurality of test patterns for correcting display gradation characteristics of a medical image display device on a display unit of the medical image display device,
The plurality of test patterns are switched and displayed on a screen one pattern at a time, and the test pattern displayed on each switching screen is configured by two display areas, and a display area having a large display area is selected from the two display areas. The display is performed at a lower luminance level than the other display area.

The invention described in claim 2 is the test pattern display method according to claim 1,
A test pattern to be displayed on each switching screen is displayed on the entire screen.

The invention according to claim 3 is a medical image display device,
Display means for displaying medical images;
A plurality of test patterns for correcting the display gradation characteristics of the display means are switched one pattern at a time to be displayed on the display means, and the test pattern to be displayed on each switching screen is composed of two display areas. A control means for displaying a display area having a large display area of the two display areas at a lower luminance level than the other display area;
It is characterized by providing.

The invention according to claim 4
On the computer,
A function to display a medical image on a display means;
A plurality of test patterns for correcting the display gradation characteristics of the medical image display device are switched one pattern at a time to be displayed on the previous display means, and the test pattern displayed on each switching screen is composed of two display areas A function of displaying a display area having a large display area at a lower luminance level than the other display area of the two display areas;
It is a program for realizing.

  According to the first, third, and fourth aspects of the present invention, when the test pattern is displayed, the display is switched and displayed one pattern at a time on the screen. When the test pattern is inserted, it is possible to prevent the visual accuracy from being lowered. Moreover, since the display area with a large display area is set to a low luminance level among the two display areas constituting the test pattern, when the observer observes the test pattern, the area with the low luminance as a whole is larger. The observer's pupil is easy to open and becomes sensitive to light, improving the visual accuracy with respect to the luminance level. Therefore, the display gradation characteristics can be corrected more accurately.

  According to the second aspect of the present invention, since the test pattern is displayed on the entire screen, the proportion of the display area having a low luminance level in the observer's visual field is increased, and the visual accuracy of the observer can be further improved. it can.

First, the configuration will be described.
FIG. 1 shows an internal configuration of a medical image display apparatus 10 in the present embodiment.
As illustrated in FIG. 1, the medical image display apparatus 10 includes a control unit 11, an operation unit 12, a display unit 13, a communication unit 14, a RAM (Random Access Memory) 15, and a storage unit 16.

  The control unit 11 develops various control programs such as a system program stored in the storage unit 16 and a calibration processing program according to the present invention in the RAM 15, and centrally controls the operation of each unit according to the control program.

  In the calibration process, the level range of the drive level that can be displayed and driven by the medical image display device 10 is divided into N equal parts, and the data of each of the N test patterns in which the N equally divided drive levels are set, The information is output and displayed on the display unit 13 together with the set drive level information. That is, each test pattern is displayed at a luminance level corresponding to each drive level divided into N equal parts. Each test pattern is formed from two display areas, one of which has a drive level divided into N equal parts, and the other area that is higher than the drive level divided into N parts by a predetermined level. Set to level.

  When the N test patterns are displayed on the display unit 13, the control unit 11 switches and displays the patterns one pattern at a time. Further, the ratio of the area of the display area in which the drive level divided into N is set to the area of the other display area is 7: 3, that is, the display area displayed at the low luminance level is The size of each display area that forms the test pattern is changed according to the size of the display screen so that the area becomes large, and the test pattern whose size has been changed is displayed on the entire display screen of the display unit 13. The display area ratio is not limited to 7: 3 and can be set as appropriate.

  When the brightness level adjustment operation is performed on the displayed test pattern via the operation unit 12, the drive level in the test pattern is changed according to the operation instruction and the display unit 13 drives the display. When the adjustment operation is completed, a correction curve for correcting the display gradation characteristics of the medical image display device 10 is obtained based on the drive level value of each line forming each test pattern. Then, an LUT (Look Up Table) that defines an output value for the input value of the correction curve is created and stored in the storage unit 16.

  The display characteristic refers to the correlation between the drive level and the luminance level, and the display gradation characteristic refers to the correlation between the input level of the pixel value in the image data to be displayed and the luminance level when the image data is displayed. .

  The operation unit 12 includes a keyboard and a mouse. When these keyboard and mouse are operated, an operation signal corresponding to the operation is generated and output to the control unit 11. The operation unit 12 may have a touch panel formed integrally with the display unit 13.

  The display unit 13 includes a monitor such as an LCD or a CRT, and drives the monitor according to a display control signal input from the control unit 11. At the time of calibration processing, each test pattern [n] input from the control unit 11 is switched and displayed one pattern at a time on one screen. When each test pattern [n] is displayed, the monitor is displayed and driven at a drive level designated according to the drive level information input together.

  The communication unit 14 has communication interfaces such as a NIC (Network Interface Card), a modem, and a router, and performs data communication with external devices on a LAN (Local Area Network) provided in the hospital via these communication interfaces. I do. For example, a medical image data is acquired by accessing an image server in which medical images of patients are managed in a database.

  The RAM 15 forms a work area for temporarily storing various programs executed by the control unit 11 and data processed by these programs.

  The storage unit 16 is configured by a magnetic or optical recording medium, a semiconductor memory, or the like, and stores various control programs such as a system program and a calibration processing program. Further, as parameters used during the calibration process, information on the ratio of the display area of the reference target and the display area of the adjustment target (7: 3 in this embodiment), information on the size of the display screen of the display unit 13, and the like. As a processing result of the program, for example, an LUT for correcting display gradation characteristics of the medical image display device 10 created by a calibration process is stored.

The storage unit 16 stores a plurality of test pattern data used in the calibration process.
FIG. 2 shows an example test pattern.
As shown in FIG. 2, the test pattern [n] (n in parentheses indicates a pattern number assigned to identify each test pattern. N = 1,..., N) is driven on the display unit 13. The level range of possible drive levels, that is, 0 to the maximum drive level DDL _max is divided into N equal parts, and the drive level is created corresponding to each of the N drive levels. In the present embodiment, an example of dividing into eight parts is shown, but it is assumed that the number of N to be equally divided can be appropriately set depending on the accuracy of calibration. When it is desired to perform calibration with high accuracy, it is preferable to increase the N number.

In each test pattern [n], two display areas having different drive levels are formed as shown in FIG. One display area is set with a drive level in which the maximum drive level DDL _max is equally divided into N, and the other display area is set with a drive level that is a certain level higher than the drive level set in one of the display areas. Yes. The display area in which the drive level divided into N is set is referred to as a reference target, and the display area in which the drive level is set to be higher than the reference target is referred to as an adjustment target.

When the drive level of the reference target is DDLK [n] and the drive level of the adjustment target is DDLT [n], DDLK [n] is represented by the following equation 1, and DDLT [n] is represented by the following equation 2.

Hereinafter, a calibration process executed by the medical image display apparatus 10 of the present embodiment using the test pattern [n] will be described.
FIG. 4 is a flowchart for explaining the calibration process. This process is started when calibration is selected from the environment setting menu.

  In the calibration process shown in FIG. 4, first, the pattern number n of the test pattern to be displayed is set to an initial value n = 1 (step S1). Next, data of the test pattern [n] is read from the storage unit 16. Then, the size of each display area in the test pattern [n] is adjusted according to the size of the display screen so that the ratio of the area of the display area of the reference target and the display area of the adjustment target is 7: 3. The adjusted test pattern [n] is displayed on the entire display screen of the display unit 13 (step S2). If the display area of the reference target is larger than the adjustment target, the display area of the reference target may be arranged inside the screen and its background may be used as the adjustment target display area. The display area may be arranged inside the screen, and the background side may be used as the reference target display area.

  FIG. 5 shows a display example of the test pattern [n] whose size has been adjusted. FIG. 5A is a diagram illustrating a display example in which the display area of the reference target is arranged on the background side, and FIG. 5B is a display example in which the display area of the reference target is arranged inside the screen. FIG. In either case, only one pattern is displayed on one screen.

  When the test pattern [n] is displayed in this way, the operator can make the minimum luminance level difference between the adjustment target and the reference target in the test pattern [n] visually visible via the operation unit 12. Until the brightness level of the adjustment target is increased or decreased. The minimum visually recognizable luminance level difference is a luminance level difference at the limit where the luminance level difference can be visually recognized as a result of the operator adjusting the luminance level of the adjustment target in accordance with the luminance level of the reference target. Specifically, when the luminance level of the adjustment target is lowered by one more level, the luminance level is adjusted until the operator cannot distinguish the luminance level difference between the adjustment target and the reference target. Note that the operator who performs calibration may be an observer who observes a medical image, or may be a maintenance person who performs only calibration.

  In the medical image display device 10, when an operation for adjusting the luminance of the adjustment target is performed via the operation unit 12, the operation signal is analyzed, and it is determined whether an operation instruction has been given to increase or decrease the luminance level. (Step S3). When an operation instruction is given to increase the luminance level (step S3; up), the drive level DDLT [n] of the adjustment target is increased by one level, and the adjustment level being displayed is increased by the drive level DDLT [n]. The display is driven (step S4). On the other hand, when an operation instruction is given to reduce the brightness (step S3; down), the drive level DDLT [n] of the adjustment target is lowered by one level, and the drive level DDLT [n] in which the adjustment target being displayed is lowered. The display is driven (step S5). That is, the luminance level is raised and lowered by one drive level according to one operation. Even if the operation to lower the luminance level of the adjustment target is repeated, the adjustment operation that is lower than the drive level of the reference target is disabled so that the luminance level of the adjustment target does not become lower than the luminance level of the reference target. The adjustment operation is limited.

When the drive level adjustment operation is performed, it is determined whether or not the adjustment operation is completed (step S6). If the adjustment operation is still being performed via the operation unit 12 (step S6; N), step is performed. Returning to the process of S4, the luminance level is adjusted in accordance with the input operation instruction. On the other hand, when the adjustment operation is completed (step S6; Y), the drive level DDLT ′ [n] of the adjustment target of the test pattern [n] at the end of the adjustment is determined, and the drive level DDLT ′ [n] and the reference target are determined. A difference ΔDDL _jnd [n] from the drive level DDLK [n] is calculated (step S7). This ΔDDL _jnd [n] corresponds to the minimum luminance level difference visible to the operator in the test pattern [n].

  Next, it is determined whether or not the above-described adjustment operation has been completed for all test patterns [n] (step S8). If the adjustment operation has not been completed for all the test patterns (step S8; N), the pattern number n is incremented by 1 (step S9), the process returns to step S2, and the adjustment operation is performed for the next test pattern [n]. Is repeated. That is, only one test pattern [n] is displayed on one screen, and each test pattern [n] is sequentially switched and displayed in the order of the pattern numbers as shown in FIG.

Then, when all the test patterns [n] are displayed and the adjustment operation is completed (step S8; Y), as shown in FIG. 7, with respect to the drive level DDLK [n] of the reference target of each test pattern [n] ΔDDL _jnd [n] calculated in this way is plotted, and an approximate function g (DDL) of each plotted point is calculated (step S10). That is, each ΔDDL _jnd [n], which is a discrete value, is interpolated to obtain a continuous value corresponding to the drive level DDL in the entire level range. That is, the approximate function g (DDL) is a function indicating the correspondence between the drive level DDL and the minimum drive level difference ΔDDL _jnd [n].

Next, a function h (DDL) obtained by integrating the calculated function g (DDL) for each drive level DDL is calculated by the following expression 3 (step S11). The g (DDL) indicates the slope of h (DDL).

FIG. 8 is a diagram illustrating h (DDL). The X axis represents the drive level DDL, and the Y axis represents h (DDL) with respect to the drive level DDL. At this time, if the value of h (DDL) at the maximum drive level DDL _max that can be driven by the medical image display device 10 is I _max , h (DDL) so that this I _max corresponds to the maximum drive level DDL _max. Is normalized, and f (DDL) indicating normalized h (DDL) is calculated by the following expression 4 (step S12).

  Then, a curve as shown in FIG. 9 is created in which the drive level DDL on the X axis in FIG. 8 is replaced with the input level of the image value, and h (DDL) on the Y axis is replaced with the calculated f (DDL). . With this curve, it is possible to obtain a drive level that realizes a corresponding luminance level from the input level of the pixel value so that the input level of the pixel value is finally displayed at a luminance level visually linear to the input level. it can. That is, this curve is a correction curve for correcting the display gradation characteristic (that is, the relationship between the input level of the pixel value and the luminance level when actually displayed) according to the display characteristic of the medical image display apparatus 10. In the control unit 31, an output value for the input value of the correction curve is calculated and tabulated (LUT is created) (step S13). When the created LUT is stored in the storage unit 16 as an LUT for correcting the display gradation characteristics of the medical image display device 10, this processing is terminated.

  When displaying a medical image, the created LUT is referred to, a drive level (output value) corresponding to the input level (input value) of the pixel value of the medical image is obtained, and display drive is performed at the drive level. . Since the drive level obtained by the LUT is a drive level that is corrected so that the luminance level when the drive display is performed at the drive level has a linear relationship with the input level of the pixel value, the medical image display The display gradation characteristics of the medical image display apparatus 10 are corrected according to the display characteristics of the apparatus 10 and the visual characteristics of the operator.

  As described above, in the present embodiment, when the test pattern for calibration is displayed, the pattern is switched and displayed one pattern at a time. Therefore, it is possible to prevent the visual recognition accuracy from being lowered by entering a test pattern other than the test pattern to be visually recognized in the visual field of the operator. Therefore, more accurate calibration can be performed.

  In addition, since the reference target, which is the display area with the lower luminance level in the test pattern [n], has a larger display area than the display area of the adjustment target, the proportion of the display area with the lower luminance level on the display screen is increased. be able to. As a result, the pupil of the operator can be easily opened and is sensitive to light, so that the visibility with respect to the luminance level is improved. Therefore, more accurate calibration can be performed.

It is a figure which shows the internal structure of the medical image display apparatus 10 in this Embodiment. It is a figure which shows the test pattern [n] displayed at the time of a calibration process. It is a figure explaining two display areas which form test pattern [n]. 5 is a flowchart for explaining calibration processing executed by the medical image display apparatus 10. It is a figure which shows the example of test pattern [n] by which size adjustment was performed so that the display area of a reference | standard target might become larger than an adjustment target, and it displayed on the whole display screen. It is a figure which shows a screen transition when one test pattern [n] is displayed on one screen sequentially. It is a figure which shows the function g (DDL). It is a figure which shows the function h (DDL). 4 is a diagram illustrating a correction curve for correcting display gradation characteristics of the medical image display apparatus 10; FIG. It is a figure which shows the example of a display of the conventional test pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Medical image display apparatus 11 Control part 12 Operation part 13 Display part 14 Communication part 15 RAM
16 Memory unit

Claims (4)

A test pattern display method for displaying a plurality of test patterns for correcting display gradation characteristics of a medical image display device on a display unit of the medical image display device,
The plurality of test patterns are switched and displayed on a screen one pattern at a time, and the test pattern displayed on each switching screen is configured by two display areas, and a display area having a large display area is selected from the two display areas. A test pattern display method, wherein display is performed at a lower luminance level than the other display area.   2. The test pattern display method according to claim 1, wherein a test pattern to be displayed on each switching screen is displayed on the entire screen. Display means for displaying medical images;
A plurality of test patterns for correcting the display gradation characteristics of the medical image display device are switched one pattern at a time to be displayed on the display means, and the test pattern displayed on each switching screen is composed of two display areas A control means for displaying a display area having a large display area at a lower luminance level than the other display area of the two display areas;
A medical image display device comprising: On the computer,
A function to display a medical image on a display means;
A plurality of test patterns for correcting the display gradation characteristics of the medical image display device are switched one pattern at a time to be displayed on the previous display means, and the test pattern displayed on each switching screen is composed of two display areas And a function of displaying a display area having a large display area at a lower luminance level than the other display area of the two display areas,
A program to realize