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Contrast

When viewing medical images, one of the most important factors for accurate diagnosis is contrast. The higher the contrast, the more differences in shades our eyes are able to see. Most medical monitors aim to provide high contrast screens, which is certainly the first and most important way to increase contrast. But even with a high contrast monitor, one little thing can greatly reduce contrast: ambient light.

Ambient light can reduce contrast in several ways. The most obvious ways would be:

  1. Diffuse Reflections: Light is reflected uniformly across the screen, whitewashing the blacks on screen.
  2. Specular reflections and glare: Light is reflected onto the screen directly from an external light source, or reflected off of an object, causing glare or a ‘specter’ of the object to appear on screen. This can be distracting and reduces the contrast at that specific location.

However these can be minimised by using anti-reflective coatings on the screen, and positioning the monitor in such a way that light does not directly reflect onto the screen.

The most major way that ambient light can reduce contrast is by affecting the eyes’ ability to adapt to a certain level of light. At any one time, the human eye can detect a contrast ratio of 1000, however this ratio is not definite, but rather relative. For example when in a dim tunnel you will be able to see most things clearly. When you suddenly exit into the sunshine outside, most objects will be brighter than the bright objects in the tunnel, so they will appear as a bright white to your vision. This is because in the dim tunnel, the darkest objects become ‘black’ to your perception, and the bright objects – for example the dim light coming the ceiling – become ‘white’ to your perception. Anything brighter than the dim light would automatically register as ‘white’ to your vision – thus when you step outside you will suddenly be blinded because the majority of objects will be brighter than anything in the tunnel.

Dark to light adaption
Eyes adapt to the brightness level of one’s environment. If adapted to a dark tunnel, suddenly exiting will cause you to be momentarily blinded with white. However after several minutes the eyes will re-adapt to this brighter environment.

Conversely, if your eyes are adjusted to a sunny environment and you suddenly go into a dim tunnel, everything darker than the dark objects in the sunshine will suddenly appear black. You have probably experienced this yourself either entering or exiting a tunnel or dark room, and know that it takes several minutes until you can clearly see again in a new environment.

This is relevant in the reading room, because if the screen and the ambient light are quite different (either brighter or darker) your vision will constantly be readjusting between the ambient light and the screen each time you look away from the screen. Despite your eyes adjusting to the screen, as soon as you look away to a brightly lit wall, light or object – your eyes will begin readjusting to this change in contrast. So, when you look back to your screen you will no longer have optimal vision until several minutes have passed.

In general it is recommended that the ambient lighting matches the brightness of your screen – which is stated to be 20 to 40 lux when the screen is at a brightness of at least 350 cd/m2 (or 420 cd/m2 for mammography), as per the American College of Radiology guidelines. However the European guidelines for quality assurance in breast cancer screening diagnoses recommends 20 lux or less. One study has shown that ambient lighting below 7 lux is too dark, and over 100 lux is too bright, so regardless of which recommendation is followed – ambient light must not be too dark or too bright. Additionally, before beginning work, a radiologist should allow their eyes to adjust for about 15 minutes to bring their vision to the optimal level.

The ideal reading room should have an ambient lighting to match the monitor screen.
The ideal reading room should have an ambient lighting to match the monitor screen.

Eye fatigue

The quality of human vision is incredibly varied – depending on environmental factors as mentioned earlier, and also on physiological factors. Eye fatigue – apart from being uncomfortable – can also temporarily degrade one’s vision. Having optimal vision is vital in radiology, so it’s important to reduce any eye fatigue – and ambient light can have a large effect on this.

In a room where the ambient light is greatly different to the screen, every time you move your eyes from the screen to another location, your pupils will either dilate (if the ambient lighting is less) or contract (if the ambient light is greater). This constant dilation and contraction tires the muscles in your eye – leading to eye fatigue. This can also increase the amount of time that is needed for your eyes to adjust to a new setting.

Eye fatigue can also be caused by glare and reflections on the screen, which causes the eyes to refocus each time vision is passed over the brightened area.

A range of ergonomic issues can also cause eye fatigue. Read ‘How to Create the Ideal Ergonomic, Stress-Free and Work Efficient Environment’ to find out more. 

Light can reflect onto the screen creating specters (left) and glare (right).
Light can reflect onto the screen creating specters (left) and glare (right).

How to achieve optimal ambience

The best way to control ambient light is with dim lights that are positioned behind the screen. As overhead lights – even dimmed ones – can cause glare and reflections it is recommended to position lights behind the monitor.

However many radiologists may find that this environment is too dark to comfortably read papers and make notes. For this reason a small light positioned below or beside the monitor is ideal for illuminating papers and notes on the desk.

EIZO offers a device which can do all of the above. The RadiLight is a small light that attaches to the back of RadiForce monitors and gently illuminates the wall behind the monitor. This prevents any glare or reflections, and also illuminates the room to the ideal brightness. It also has an additional spot light on an adjustable arm which can be easily switched on and off with just the touch of a button, and moved to illuminate a specific area of your desk. It is made using non-reflective materials to ensure that light does not reflect onto the screen. The brightness of these two lights is also adjustable to ensure that the ultimate ambient lighting is achieved. 

Lighting behind the monitor prevents reflections and glare.
Lighting behind the monitor prevents reflections and glare.
RadiLight Animation
RadiLight: easy on the eyes

RadiLight is an easy-to-operate comfort light for radiologists who work in dark reading rooms. The soft illuminance in the background of the screen reduces the strain on the eyes that frequently occurs due to constant light-dark changes between bright screens and objects in a dark environment. RadiLight, used as the sole light source during the acceptance testing of a diagnostics station, helps set up consistent lighting conditions. The level of ambient light created in this way can also be reproduced during consistency tests later on. RadiLight also features a small, connectable reading light to allow users to check and read documents such as patient files or just be able to use keyboards and other aids.

About RadiLight

To RadiForce products

RX850 G&R series
RX850 RadiForce

The 8 MP diagnostic RX850 diagnostic monitor can replace the 2 or 3 monitors that would otherwise be standard for a diagnostic station. The DICOM GSDF characteristic is already configured in the factory.

  • 79 cm (31.1 Inches)
  • 8 Megapixels (colour)
  • IPS
  • 2x DisplayPort, 2x DVI-D
  • Format 17:9
  • 79 cm (31.1 Inches)
  • 8 Megapixels (colour)
  • IPS
  • 2x DisplayPort, 2x DVI-D
  • Format 17:9
GX340 G&R series
GX340 RadiForce

The 3 MP GX340 diagnostic monitor with the precision of a 14 bit look-up table renders in particular thorax exposures or fine structures of skull and extremities exactly.

  • 54 cm (21.3 Inches)
  • 3 Megapixels (greyscale)
  • IPS
  • 1x DisplayPort, 1x DVI-D
  • Format 3:4
  • 54 cm (21.3 Inches)
  • 3 Megapixels (greyscale)
  • IPS
  • 1x DisplayPort, 1x DVI-D
  • Format 3:4
GX240 G&R series
GX240 RadiForce

The GX240 diagnostic monitor is used to display x-ray images and cross-sectional images. A DICOM characteristic curve is preset in the factory and can be refreshed through automatic calibration.

  • 54 cm (21 Inches)
  • 2 Megapixels (greyscale)
  • IPS
  • 1x DisplayPort, 1x DVI-D
  • Format 3:4
  • 54 cm (21 Inches)
  • 2 Megapixels (greyscale)
  • IPS
  • 1x DisplayPort, 1x DVI-D
  • Format 3:4
MX242W MX series
MX242W RadiForce

MX242W: the 24" DICOM preset monitor can display two images or one image and corresponding diagnosis.

  • 61 cm (24.1 Inches)
  • 2.3 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-I
  • Format 16:10
  • 61 cm (24.1 Inches)
  • 2.3 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-I
  • Format 16:10
RX250 G&R series
RX250 RadiForce

The display of x-ray images and cross-sectional images is the primary task of the RX250. Thanks to the DICOM GSDF characteristic curve, it can display radiological exposures exactly.

  • 54 cm (21.3 Inches)
  • 2 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-D
  • Format 3:4
  • 54 cm (21.3 Inches)
  • 2 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-D
  • Format 3:4
MX232W-DT MX series
MX232W-DT RadiForce

Moderne Modalitäten für Tubus-, Panorama- oder DVT-Aufnahmen liefern klare Bilder. Die Wiedergabequalität von Röntgenbildern im dental-radiologischen Umfeld hängt jedoch wesentlich von der Wahl des richtigen Bildschirms ab.

  • 58.4 cm (23 Inches)
  • 2 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-I
  • Format 16:9
  • 58.4 cm (23 Inches)
  • 2 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-I
  • Format 16:9
MX315W MX series
MX315W RadiForce

4,096 x 2,160 pixels ensure crisper details across the board. The MX315W correctly displays greyscale tones of radiological images over the entire screen.

  • 79 cm (31.1 Inches)
  • 8 Megapixels (colour)
  • IPS
  • 2x DisplayPort, DVI-D
  • Format 17:9
  • 79 cm (31.1 Inches)
  • 8 Megapixels (colour)
  • IPS
  • 2x DisplayPort, DVI-D
  • Format 17:9
RX660 G&R series
RX660 RadiForce

The size and resolution of the monitor allow users to organize images as they see fit. The RX660 also take up less space than solutions with two 3-megapixel screens.

  • 76 cm (30 Inches)
  • 6 Megapixels (colour)
  • IPS
  • 2x DisplayPort, 1x DVI-D
  • Format 16:10
  • 76 cm (30 Inches)
  • 6 Megapixels (colour)
  • IPS
  • 2x DisplayPort, 1x DVI-D
  • Format 16:10
RX1270 G&R series
RX1270 RadiForce

The compact and convenient all-rounder in radiological diagnostics for colour and monochrome images in virtually every size and resolution.

  • 78.4 cm (30.9 Inches)
  • 12 Megapixels (colour)
  • IPS
  • 2x DisplayPort, HDMI
  • Format 3:2
  • 78.4 cm (30.9 Inches)
  • 12 Megapixels (colour)
  • IPS
  • 2x DisplayPort, HDMI
  • Format 3:2
MS236WT MX series
MS236WT RadiForce

The MS236WT detects up to 10 touches simultaneously and permits smooth and accurate stylus input. It ignores erroneous input, for example when the ball of the hand touches the surface.

  • 58 cm (23 Inches)
  • 2 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-D, 1x Dsub
  • Format 16:9
  • 58 cm (23 Inches)
  • 2 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-D, 1x Dsub
  • Format 16:9
GX560-MD G&R series
GX560-MD RadiForce

The GX560 MammoDuo displays detailed mammography images and images of fine structures in high resolution. Two times 5 megapixels and a degree of luminance, which is suited to the specific task, ensures excellent reproduction.

  • 54.1 cm (21.3 Inches)
  • 5 Megapixels (greyscale)
  • IPS
  • 2x DisplayPort, 1x DVI-D
  • Format 4:5
  • 54.1 cm (21.3 Inches)
  • 5 Megapixels (greyscale)
  • IPS
  • 2x DisplayPort, 1x DVI-D
  • Format 4:5
RX360 G&R series
RX360 RadiForce

The RX360 with 3-megapixel resolution and a DICOM-GSDF luminance characteristic curve is ideal for precisely displaying monochrome and colour images produced by radiological systems.

  • 54.1 cm (21.3 Inches)
  • 3 Megapixels (colour)
  • IPS
  • 2x DisplayPort, 1x DVI-D
  • Format 3:4
  • 54.1 cm (21.3 Inches)
  • 3 Megapixels (colour)
  • IPS
  • 2x DisplayPort, 1x DVI-D
  • Format 3:4
MX194 MX series
MX194 RadiForce

The MX194 with preset DICOM® tone value characteristic curve. It guarantees distortion-free grey tone rendering of radiological images. That is ideal for informative clinical reviews of images from digital image distribution.

  • 48.1 cm (19 Inches)
  • 1.3 Megapixels (colour)
  • VA
  • 1x DisplayPort, 1x DVI-D, 1x Dsub
  • Format 5:4
  • 48.1 cm (19 Inches)
  • 1.3 Megapixels (colour)
  • VA
  • 1x DisplayPort, 1x DVI-D, 1x Dsub
  • Format 5:4
MX216-SB MX series
MX216-SB RadiForce

2-megapixel colour monitor for the medical field with DICOM® preset, 240 cd/m2 factory-calibrated brightness and integrated sensor for reliable image quality.

  • 54 cm (21 Inches)
  • 2 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-D
  • Format 3:4
  • 54 cm (21 Inches)
  • 2 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-D
  • Format 3:4
MX216-HB MX series
MX216-HB RadiForce

2-megapixel colour monitor for the medical field with DICOM® preset, 340 cd/m2 factory-calibrated brightness and integrated sensor for reliable image quality.

  • 54 cm (21 Inches)
  • 2 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-D
  • Format 3:4
  • 54 cm (21 Inches)
  • 2 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-D
  • Format 3:4
RX560-MD G&R series
RX560-MD RadiForce

Thanks to its hybrid gamma PXL functionality, the RX560 MammoDuo automatically differentiates between greyscale and colour images, down to the pixel. Each pixel is displayed with the required luminance characteristic curve.

  • 54.1 cm (21.3 Inches)
  • 5 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-D
  • Format 4:5
  • 54.1 cm (21.3 Inches)
  • 5 Megapixels (colour)
  • IPS
  • 1x DisplayPort, 1x DVI-D
  • Format 4:5