EIZO Sensor Solutions for Medical Monitors. Backlight Sensor / External Sensor / Swing Sensor

Transcription

1 White Paper EIZO Sensor Solutions for Medical Monitors Backlight Sensor / External Sensor / Swing Sensor CONTENTS 1 Introduction What is Monitor Quality Control? Backlight Sensor Functions Utilizing Backlight Sensor Monitor Quality Control Functions Made Possible with Backlight Sensor External Sensor Functions Using External Sensor Monitor Quality Control Functions Executable with External Sensor Swing Sensor Swing Sensor Monitor Quality Control Functions Available with Swing Sensor What is Correlation? Conclusion No Revision A June 2007 EIZO NANAO CORPORATION radiforce.com White Paper 1/13

2 1 Introduction Monitors have various characteristics that are subject to change in quality over time, including luminance, grayscale, and luminance uniformity. Reduced monitor quality due to aging and inter-monitor differences in viewing conditions can often lead to serious problems in hospitals, for example, where several monitors may be arranged together for simultaneous viewing, or where a single image may be confirmed using different monitors. In order to detect changes in monitor quality, monitor quality control is required to make the appropriate calibrations. Further, with the massive number of LCD monitors at major hospitals accelerated by the adoption of PACS, HIS, and RIS technologies, IT administrators and maintenance service staff will be faced with the increasing labor and costs associated with such monitor quality control. As a solution in monitor quality control, EIZO proposes its RadiCS quality control (QC) management software, allowing detection and calibration of changes in monitor conditions through a number of simple and clear steps. The company also offers the RadiNET Pro network QC management software, forming a unified management system that dramatically reduces labor and costs. EIZO has also developed three types of sensors Backlight Sensor, External Sensor, and Swing Sensor (either Built-In Swing Sensor or Clip-On Swing Sensor; see Fig. 1) to be used in the detection and calibration system. When used together with the RadiNET Pro software, these sensors allow for remote monitor quality control. With these sensor components, users may select the optimal sensor system according to the control requirements of their hospital environment; this in turn will lead to reductions in the Total Cost of Ownership (TCO). Fig. 1. EIZO Sensors This white paper will introduce the benefits of each of the sensor types described above. We hope that you will find this introduction useful in examining the cost reduction strategies surrounding the installation and operation of your hospital s facilities and instruments. White Paper 2/13

3 2 What is Monitor Quality Control? The three most important characteristics of monitors luminance, grayscale, and luminance uniformity change gradually in quality over time, resulting in inconsistent viewing results between different monitors. These inter-monitor differences create problems in particular when viewing images in a medical context. When LCD monitors are used as medical display monitors, proper monitor quality control measures must be taken to detect and calibrate these changes in monitor quality. Organizations in various countries, such as AAPM, DIN, IEC, and JESRA, are currently working toward the standardization of items and criteria for the evaluation of monitor quality. In this context, testing performed upon installation is referred to as the acceptance test, and testing performed regularly are called constancy tests. The main items for evaluation in the acceptance and constancy tests consist of the pattern check, luminance check, grayscale check, and uniformity check. Allowable levels for these values differ among the standards of different countries. When inconformity with the standards is detected in the results of the acceptance and constancy tests, the monitor units must be properly corrected, or calibrated, to ensure compliance with the performance standards for luminance, grayscale, etc. applicable to medical display monitors. Of the four quality characteristics (pattern, luminance, grayscale, and uniformity), the global standard for the grayscale characteristics of medical Fig. 2. Monitor Quality Control display monitors is referred to as DICOM (Digital Imaging and Communications in Medicine). In general, manufacturers develop and produce LCD monitors for medical display for which calibration and maintenance can be performed in accordance with the GSDF (Grayscale Standard Display Function) stipulated in DICOM Part 14 for luminance and grayscale characteristics in LCD monitors. In other words, medical display monitors may generally be said to feature grayscale functions capable of calibration according to the GSDF. Chapter 3 and on will describe the procedures of monitor QC management that can be performed using the EIZO Sensors. However, please note that for the pattern check, which is one of the main evaluation items in the acceptance and constancy tests, several pattern images are displayed on the monitor screen and must be checked visually for flaws, as shown in Fig. 3; this check thus does not rely on the sensors. Therefore, pattern checks can be carried out sufficiently even if only the images for the pattern check are available. Fig. 3. Pattern Check Screen White Paper 3/13

4 3 Backlight Sensor All models of the EIZO RadiForce medical display monitor series are equipped with Backlight Sensors. Small round hole for light transmission is opened in the rear of the panel behind the backlight. The Backlight Sensor mounted on the main circuit board directly scans the backlight luminance through this hole (Fig. 4). Let us see which monitor quality control tasks may be performed using this sensor. Fig. 4. Image of the Mounted Backlight 3-1 Functions Utilizing Backlight Sensor Self-calibration functions can be executed using RadiCS with a Backlight Sensor. This is a simple calibration process for luminance and grayscale calibration. (For grayscale calibration, readers are referred to White Paper No , Brightness Control with a Backlight Sensor. ) Furthermore, the RadiNET Pro network QC management software allows monitor administrators to perform remote self-diagnosis and self-calibration functions from the administrator PC via network. Fig. 5. Pattern Check Screen the EIZO Sensor system. Since the Backlight Sensor is not capable of performing a grayscale or uniformity check, a different mechanism is required for these processes, such as When the self-diagnosis function using the Backlight Sensor and the RadiCS QC management software is executed, the Backlight Sensor measures the backlight luminance. If the backlight brightness is not within the allowable range of the preset value, the warning message saying The monitor does not meet the luminance setting. Change target luminance and calibrate the monitor, is displayed on screen. This function may be executed at any time, and may also be set for automatic execution on a regular basis using the scheduling function in the task setup window. Since the self-diagnosis function is processed in the background of running software, it will not interfere with the user s work. Thus, this function may be used as a supplementary verification measure for maximum luminance control. White Paper 4/13

5 3-2 Monitor Quality Control Functions Made Possible with Backlight Sensor Items for the quality control test that are enabled using Backlight Sensor is checked in the table below. : Executable : Not Executable Remote: Can be Executed Remotely Test Items Luminance Check Grayscale Check Uniformity Check Backlight Sensor * * + Remote * Since Backlight sensor is incapable of taking objective luminance measurements, it cannot be used for the luminance check. Further, the table below summarizes the suitability of the Backlight Sensor for calibration tasks in terms of precision, labor, and time. : Excellent : Good Precision Labor Time Required Software Backlight Sensor RadiCS (RadiNET Pro for remote execution) It is recommended that the calibration of LCD monitors used as medical display monitors be performed with high precision provided by the External Sensors. However, for monitors that are used for reference purposes, the simple calibration system offered by the self-diagnosis function of the Backlight Sensor and the RadiCS monitor QC management software is sufficient. Although the calibration precision of the self-diagnosis function is not as high as that offered by External Sensors, the process requires no additional attachment of sensors and can be performed simply by clicking self-diagnosis in the RadiCS menu. Self-diagnosis is a quick process that takes only 10 seconds or so on all models. It can also be performed remotely, offering an effective TCO reduction solution in the quality control of large arrays of reference monitors. White Paper 5/13

6 4 External Sensor The RadiCS monitor QC management software package contains the EIZO UX1 sensor for both monochrome and color monitors (Fig. 6). Let s see which monitor quality control tasks may be performed using this sensor. Fig. 6. RadiCS and UX1 Sensor 4-1 Functions Using External Sensor First, the items of the acceptance and constancy tests that may be performed using External Sensor include the luminance and grayscale checks (performed by a sensor attached to the center of a monitor), as well as the uniformity check, which can be carried out very reliably using sensor attached to the center and to four corners of a monitor. Thus, all items can be checked in the strict detection of monitor quality. The combined use of the EIZO External Sensor and the RadiCS QC management software thus allows for acceptance testing in compliance Fig. 7. Attaching the External Sensor with three standards: AAPM, DIN, and JESRA (although an additional LX-Plus or LS-100 sensor is required for compliance with the DIN standards). Constancy tests may be performed in compliance with all five standards: AAPM, DIN, IEC, JIS, and JESRA. How about the calibration process? Figure 8 shows the calibration settings window for the RadiCS QC management software. The target values for maximum and minimum luminance (and also, for color monitors, the color temperature) may be set by the user, and the standard (display function) for the calibration of grayscale may be selected not only from the DICOM Part 14 GSDF covering grayscale but also from this standard s values for gamma, CIE, and log-linear values. High-precision calibration of luminance and grayscale characteristics is also possible, however since this function requires manual attachment of the External Sensor prior to execution, this calibration cannot be performed remotely via network from the administrator PC. Fig. 8. Settings Window White Paper 6/13

7 4-2 Monitor Quality Control Functions Executable with External Sensor The items of quality control testing that are enabled by the External Sensor are checked in the table below. : Executable : Not Executable Remote: Can be Executed Remotely Test Items Luminance Check Grayscale Check Uniformity Check Backlight Sensor + Remote External Sensor Further, the table below summarizes the suitability of the External Sensor for calibration tasks in terms of precision, labor, and time. : Excellent : Good Precision Labor Time Required Software Backlight Sensor RadiCS (RadiNET Pro for remote execution) External Sensor RadiCS The time required for calibration using the External Sensor differs depending on the level of calibration measurements selected by the user; for the standard measurement level, this time is approximately 10 minutes. with External Sensor takes significantly longer than Backlight Sensor calibration and cannot be performed remotely. However, this method allows for high-precision, highly reliable calibration; accordingly, we recommend this system for the calibration of medical display monitors, which demand consistently high performance. Further, the External Sensor allows for the execution of the uniformity check, which cannot be performed otherwise, and so its use is recommended when conforming to foreign standards or in the re-execution of the acceptance test. White Paper 7/13

8 5 Swing Sensor The Built-In Swing Sensor inside EIZO High-End Monochrome Medical Display Monitors RadiForce G33/GX320/GX220 (Fig. 9) or the Clip-On Swing Sensor (which can be attached to current EIZO medical display monitors; see Fig. 10) are movable sensors. When in use, these sensors drop down from the top of the display screen; when not in use, they are stored inside the bezel so as not to distract the viewer. Let s see which monitor quality control tasks can be performed using these sensors. Fig. 9. Built-In Swing Sensor Fig. 10. Clip-On Swing Sensor 5-1 Swing Sensor When the Swing Sensors are used, they do not have to be set up each time the luminance and grayscale checks are performed. Moreover, since luminance and grayscale checks are performed using only a small section in the upper part of the screen, workers can continue with their observations and interruptions are kept to a minimum (Fig. 11). Fig. 11. Minimizing the Occupied Area Further, when this sensor is used together with the RadiNET Pro network QC management software, these checks can be performed remotely via network from the administrator PC. Uniformity check cannot be performed since the Swing Sensors cannot be moved to the center or to the four corners of a monitor. White Paper 8/13

9 How about calibration? As with the EIZO Sensors described in the previous section, the maximum and minimum luminance can be set by the user, and the standard (display function) for grayscale calibration can be selected not only from the DICOM Part 14 GSDF covering grayscale but also from this standard s values for gamma, CIE, and log-linear values in the RadiCS QC management software calibration settings window (Fig. 8). The Swing Sensors also have an advantage over the External Sensor in that it does not have to be set up before each calibration run. The calibration made by the Swing Sensors may also be performed remotely via network from administrator PC using the Fig. 12. Remote by the Administrator RadiNET Pro network QC management software (Fig. 12). Moreover, since RadiNET Pro is a Web-based application, the administrator can perform this calibration from anywhere in the hospital at any time. 5-2 Monitor Quality Control Functions Available with Swing Sensor Quality control test items enabled with the use of Swing Sensors are checked in the table below. : Executable : Not Executable Remote: Can be Executed Remotely Test Items Luminance Check Grayscale Check Uniformity Check Backlight Sensor + Remote External Sensor Swing Sensors + Remote + Remote + Remote Furthermore, the table below summarizes the suitability of Swing Sensors for calibration tasks in terms of precision, labor, and time. : Excellent : Good Precision Labor Time Required Software Backlight Sensor RadiCS (RadiNET Pro for remote execution) External Sensor RadiCS Swing Sensors RadiCS (RadiNET Pro for remote execution) White Paper 9/13

10 Swing Sensors eliminate the time and labor required to set up External Sensor before each calibration run, and offer precision on the same level as External Sensor calibration. Further, the use of the Swing Sensors enables the administrator to execute remote calibration of the monitors. The time required depends on the level of calibration measurement selected by the user; this value is approximately 15 minutes for standard measurement levels. However, since calibration is executed using only a small section in the upper part of the screen, workers can continue with their observations and interruptions are kept to a minimum. If the RadiCS scheduling function is used to set the time and date of the calibration at night after office hours, interruptions during work can be eliminated completely. The Swing Sensors thus represent an ideal solution, drastically reducing the labor and cost associated with QC management for large installations of medical display monitors. To look at one example, let s perform a simple comparison of the labor and time required of monitor administrators at hospitals where 100 monitors are installed. In an environment in which External Sensor are used to conduct monitor QC management, calibration of all monitors requires the administrator to visit all monitors to set the sensor in position manually for calibration. Assuming that an average of 5 minutes will be required to travel from one monitor to the next, 1 minute for setting up and removing sensor, and 10 minutes for calibration process, calibration work will require a total of: (5 minutes + 1 minute + 10 minutes) x 100 monitors = approximately 26 hours If the administrator works 8 hours a day, it will take him/her 3 days to complete the job. This is an extreme case, but if the facility in this example had adopted the Swing Sensors and the RadiNET Pro, he would have been able to perform remote calibration, thus saving all of the time required to travel from one monitor to the next, setting up sensor, and waiting in front of each monitor during calibration (Fig. 13). Fig. 13. Comparison of the Time Required for White Paper 10/13

11 5-3 What is Correlation? In this section, we will explain how the Swing Sensor arrives at calibration precision equivalent to that of the External Sensor. As shown in Fig. 14, luminance differs at various points on the monitor panel surface, including a difference in luminance between the point of measurement by the External Sensor and the central part of the monitor screen. Therefore, comparison is made between the luminance value measured using the Swing Sensor and the luminance value at the center of the screen measured by the External Sensor to calculate the coefficient of correlation. Although the administrator have to set up the External Sensor manually in front of the monitor Fig. 14. during Difference monitor in Luminance on Screen setup, once the coefficient of correlation has been determined, then the precise luminance at the central part of the screen can be calculated based on the measurements taken by the Swing Sensor. This process of obtaining the coefficient of correlation is referred to simply as correlation. At the Monitor Setup step, RadiCS identifies the monitors with the Clip-On Swing Sensor G1 attached and prompts the execution of correlation for the corresponding monitor. Correlation must be executed upon the installation of Clip-On Swing Sensor G1, and after the correlation data has been acquired, the asterisk (*) indicated at the head of the monitor name and serial number as in Fig. 15 will disappear. Note that the correlation data for the Built-In Swing Sensor mounted on the G33/GX320/GX220 has already been acquired prior to shipment, and so there is no need to perform correlation at Monitor Setup. Fig. 15. Monitor Setup Window for RadiCS The uniformity (specifically, the uniformity of luminance over the entire screen) of LCD monitors generally deteriorates with age (Fig. 16). However, re-execution of the correlation procedure, for example once a year, allows you to continue to perform precise luminance calculations for the central part of the screen long after installation. Approximately 25,000 Hours With the use of technologies such as those for correlation, we have achieved calibration precision using the Swing Sensor at levels equivalent to those achieved using the External Sensor. Fig. 16. Luminance Uniformity Deterioration with Age White Paper 11/13

12 6 Conclusion The items of quality control testing that are enabled using sensors available from EIZO are checked in the table below. : Executable : Not Executable Remote: Can be Executed Remotely Test Items Luminance Check Grayscale Check Uniformity Check Backlight Sensor + Remote External Sensor Swing Sensors + Remote + Remote + Remote Further, the table below summarizes the suitability of the sensors available from EIZO for calibration tasks in terms of precision, labor, and time. : Excellent : Good Precision Labor Time Required Software Backlight Sensor RadiCS (RadiNET Pro for remote execution) External Sensor RadiCS Swing Sensors RadiCS (RadiNET Pro for remote execution) [Execution of QC Management Check] When Using Backlight Sensor Measured values are not available, so this sensor cannot be used for QC management checks. However, in conjunction with the scheduling function for automatic execution of periodic self-diagnosis, this sensor can be used as a supporting feature of QC management of maximum luminance. When Using External Sensor The External Sensor must be used to perform the uniformity check. Although this requires time and labor in the manual setup of the External Sensor in front of the monitor, the External Sensor forms the most fundamental system of QC management, since this sensor allows for the performance of both the luminance and grayscale tests. When Using Swing Sensors Both the luminance and grayscale check can be made without going to the trouble of attaching and removing the sensor to and from the monitor. In particular, the RadiNET Pro allows for remote execution of QC management checks simultaneously on multiple monitors, without requiring the administrator to visit one monitor to another. The more monitors are installed in the facility, the effectiveness of using Swing Sensors and RadiNET Pro in reducing TCO for QC management will increase. White Paper 12/13

13 [Execution of ] When Using Backlight Sensor The simple self-calibration system using the Backlight Sensor and the RadiCS monitor QC management software offers is not as high precision as that offered by other EIZO sensor solutions. However, this process requires an amazingly short time only 10 seconds and can be readily executed. Further, the RadiNET Pro network QC management software can be used to perform remote calibration by administrator from anywhere in the hospital at any time without requiring any initial investment (purchasing Swing Sensors). This method proves effective in reducing TCO in cases requiring calibration of large numbers of reference monitors that do not demand strict precision. When Using External Sensor using the External Sensor and the RadiCS monitor QC management software requires approximately 10 minutes under standard measurement conditions and cannot be executed remotely since such calibration requires the attachment of a sensor in the central part of the monitor screen. This method is recommended for cases where the first priority is precise calibration of medical display monitors for which consistently high performance is demanded, but when initial investments are ruled out (i.e., for the cost of Swing Sensors). When Using Swing Sensors A calibration system using the Swing Sensors and the RadiCS monitor QC management software offers calibration precision equivalent to that of the External Sensor, yet allows for simpler execution since it eliminates the time and labor required to set up the External Sensor on site for each monitor. When used together with the RadiNET Pro network QC management software, the calibration process can be remotely executed by administrator simultaneously for multiple monitors. at standard measurement levels requires approximately 15 minutes, but this process does not interrupt normal observations of medical images. This approach is effective in reducing TCO where large numbers of medical image display monitors requiring high precision and quality are installed. All product names are trademarks or registered trademarks of their respective companies. Copyright 2007 EIZO NANAO CORPORATION. All rights reserved. White Paper 13/13