TOTOKU White Paper Monitor QA Management "i model Flat Display Systems for Medical Imaging

Monitor QA Management “i model” Table of Contents 1. Preface ------------------------------------------------------------------------------------------------------- 3 2. Changes in Image Quality ------------------------------------------------------------------------------- 3 2-1 Relationship between luminance and gamma ----------------------------------------------- 3 2-2 Causes of luminance changes ------------------------------------------------------------------- 5 2-2-1 Light source ---------------------------------------------------------------------------------- 5 2-2-2 Optical components...

TOTOKU White Paper Together with the growing prevalence of PACS and the increasing awareness of medical diagnostic display quality management, guidelines and international standards are being developed around the world. Simultaneously, the healthcare industry has become more aware of the necessity to implement a simple and quantitative quality management on a daily basis in order to keep up with the increasing number of medical displays installed on site. In response to this demand, TOTOKU has brought the "i model" into the market. The i model is equipped with a luminance sensor situated in the...

GSDF as defined here is based on the "Barten Model", a model of the visual characteristics of human eyes, which enables visually linear grayscales at the entire range of low to high luminance. The concept of JND (Just Noticeable Difference) is useful to understand the mechanism. JND is defined as the minimum amount of change in luminance necessary for human to perceive. As shown in Figure 1, the required change in luminance for human perception is less in lower levels of luminance, but the change is greater in higher levels of luminance. Human eyes are more sensitive to brightness changes in...

TOTOKU White Paper 2-2 Causes of luminance changes We discussed how luminance changes affect gamma and described why luminance must be stabilized. Now let us consider what causes a variance in luminance. The possible causes are mainly described as follows: A change in brightness of the backlight light source components A change in the reflectivity over time and transmittance of optical We will look into each factor for variation in the following section. Light Source Glass Sheet Alignment layer - Fluorescent Lamp Backlight system Figure 3 LCD panel cross section Fluorescent lamps are commonly...

3. Solution Presented by “i model” This section describes how the “i model” resolves the problems caused by the factors affecting luminance to enable high precision in luminance stabilization, and furthermore explains how luminance and gamma accuracy are managed. A commonly used luminance stabilization mechanism consists of a light control circuit, a luminance sensor, and a feedback system. It becomes apparent that the properties of the installed sensor, its location, and the accuracy of the light control circuit all can affect the degree of stabilization. In developing the “i model”, after carefully...

TOTOKU White Paper Table 1. Sensor Types Comparison 3-2 Luminance stabilization system Let us now explain the structure of the built-in front sensor technology of the "i model". Figure 5 shows the diagram of the luminance stabilization system with built-in front sensor. Measured Date Built-in Sensor Correction Table Gamma Correction Lookup Table Power Source Driver Circuitry External Luminance Sensor •During Normal Operation Figure 5. Diagram of i model's built-in front sensor In order to achieve high level of luminance stabilization, the system is highly optimized in different levels such as...

TOTOKU White Paper The correction table is created upon regular calibration with an external luminance sensor attached to the center of the The data obtained will be used as a reference of the luminance control circuit, which is updated with every external The luminance stabilization is operated whenever the display is on. Luminance variation from the target value (maximum luminance) is continuously corrected several tens of times per second at the beginning and several times per second after luminance stabilizes. This is because the rate of variation is higher for a certain time after start-up....

4 The luminance response value δ, or contrast for a JND in each measurement range, is calculated. δi = 2(L’'I-L’'I-1)/(L’'I+L’'I-1)(JI-1-JI) 5 The above steps 1) - 4) are performed for the target DICOM GSDF, and the target luminance response value δid is calculated. 6 The difference of the luminance response between DICOM GSDF and measured data is calculated. κδ= Max(|δi-δid|) 7 For diagnosis applications, this value is considered to be in compliance with DICOM GSDF if it is less than 10%; if it is more than 10%, it is considered as out of compliance. The luminance response value δ calculated...

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