NPIC Training PACS

About NPIC Point of Use Quality Assurance Test

---

NPIC Point of Use Quality Assurance Test is developed as part of the National Pathology Imaging Cooperative

Disclaimer: NPIC Point of Use Quality Assurance Test does not test screen resolution or luminance. Nor does it account for environmental lighting. Passing the test does not mean that the display device is diagnostically valid.

How to Reference this System

NPIC Point of Use Quality Assurance Test has been developed as an agile system, as a response to a rapidly changing technological infrasturcture in histopathology. Please use the following previous work when referencing this system.

NPIC Point of Use Quality Assurance Test is based on previous work, which can be found below.

For further questions about this system, please contact Alex Wright.

What is NPIC Point of Use Quality Assurance Test?

NPIC Point of Use Quality Assurance Test is a simple point-of-use quality assurance tool for ensuring your display device allows you to see the minimum amount of visual contrast between colours, for scoring digital pathology slides.

Why is this important?

NPIC Point of Use Quality Assurance Test Lite is a simple point-of-use quality assurance tool for ensuring your display device allows you to see the minimum amount of visual contrast between colours, for scoring digital pathology slides.

The image below illustrates different levels of contrast on the same digital slide.

In the image above, we have an example of a digital slide image (centre) which has had its contrast reduced (left), and increased (right). Note that reducing contrast reduces the differences in visual information in the mid tones in the image, wheres increasing contrast too much reduces visual information in the lightest and darkest extremes.

How do you measure contrast?

The measurement we use is this system is called Delta E (ΔE), which gives a numeric value to how much the visual perception between two colours differs. It is easier to explain using this simple table:

ΔE	Perceptual Difference
< 1	Not perceptible to human eyes
1 - 2	Requires close inspection to see
2 - 10	Visible at a glance
11 - 49	Colours are more similar than opposite
100	Colours are opposite

Table from: Zachary Schuessler

Delta E was formalised in 1976, and there have been multiple revisions to the way it is calculated since then. We use Delta E 2000 (dE00) and currently the ΔE value we use to validate the screen is

For more information on colour in histopathology, please see:

How to Use this System

NPIC Point of Use Quality Assurance Test is designed to be as simple as possible. There are two parts:

Part 1: The test

The system is designed to be a minimally intrusive visual test where you are required to read four letters displayed in coloured boxes, that should be barely visually discernable. You are required to type these letters the corresponding input boxes, and if you get them correct, your display screen environment has passed the test.

The test has been extended to confirm if you are working clinically or not, and also if you are working from home or not. Please use the sliders to indicate which ones fit your test environment.

Part 2: The result

Once the test is complete, you will be presented with either a success screen or a failure screen. The success screen generates an access token and an option to copy information about your test to the computer clipboard, so that you can audit your own working. Upon failure, you will be asked to re-attempt the test, and if you fail the test 3 times in a row, you will be prevented from retaking the test for a short while.

Please read our paper for further information on the design and use of this system .

For further questions about this system, please contact Alex Wright.

What is NPIC Point of Use Quality Assurance Test Profiler?

You may have seen a link to the NPIC Point of Use Quality Assurance Test Profiler tool on the home page. This is a psychophysical testing platform for developing in depth monitor profiles, in terms of ther ability to view parts of the colour spectrum relating to digital pathology slides.

Due to the increased complexity of this system, NPIC Point of Use Quality Assurance Test requires that you have registered an experimenter account with us, which you can apply for by contacting Alex Wright

---

NPIC Point of Use Quality Assurance Test Plus is currently in the testing phase of development, and requires a user account - which can be obtained by contacting Alex Wright