When calibrating the image quality of a display system intended for use in a commercial or home theater setting, I focus on fine-tuning the picture to ensure the resulting video image accurately reflects the artist’s work. Generally, content creators use reference displays that closely follow the color and detail standards used in video production. Viewing this content on another display calibrated to a similar standard offers the best chance to see the artist’s vision as intended.
It should be obvious why accurate video imagery is crucial for medical professionals. These display systems are essential for evaluations, diagnoses, and real-time monitoring during procedures. While there is some overlap between the display needs of doctors and artists, medical-grade display technologies have specific visual standards and hardware requirements that ensure their effectiveness as tools to support patients’ health and well-being.
DICOM to the Rescue
In the early 1980s, medical professionals using computed tomography (CT) or magnetic resonance imaging (MRI) systems were limited to tools provided by the device manufacturers for decoding and viewing images produced by these machines. A technical standard was necessary to define a common file format for medical imaging and the display systems used to view it. By the early 1990s, hardware manufacturers had widely adopted the Digital Imaging and Communications in Medicine (DICOM) standard, which included an optimized image format and specifications for a communication protocol (utilizing TCP/IP) to facilitate data transmission.
In addition to image data, DICOM also specifies an extensive metadata system that can incorporate a wide variety of relevant information, including patient details, the referring physician, equipment and procedure descriptions, device configuration, and the name of the machine technician on duty. DICOM also specifies a de-identification process to protect patient privacy when sharing medical data for educational or research purposes, or to comply with privacy regulations.
Since the introduction of DICOM, various initiatives and services have enhanced its interoperability, making it easier to integrate into practical clinical workflows. One of these technologies is the Picture Archiving and Communication System (PACS), a server-based environment that enables medical IT departments to provide a unified acquisition pathway across various machine types (imaging modalities), file storage, and access to DICOM-encoded data within a secure network.
The Grayscale Standard Display Function
One of the core attributes of DICOM imagery that differentiates it from the pictures and videos we typically consume is the way DICOM handles grayscale information. The default grayscale configuration for many screens, ranging from mobile devices to televisions, features a luminance configuration (from black to peak white) that mimics the natural sensitivity of the human visual system. Our visual system is better optimized to notice small changes in the brighter areas of an image compared to the darker portions (a distinctly non-linear response). We’ve modeled our picture and video standards to recreate visual content with a similar response.
Given that much of the patient imagery used by medical professionals is in grayscale format (i.e., colorless), DICOM specifies that the presentation of grayscale imagery prioritizes detail perception over artistic intent. The DICOM Part 14 Grayscale Standard Display Function (GSDF) describes a “perceptually linearized” grayscale that helps ensure the viewer can perceive a Just-Noticeable Difference (JND) between successive steps across the entire grayscale luminance range. The model for GSDF factored 1023 luminance levels, ranging from 0.0500 nits to 4000 nits, representing the lowest practical luminance of CRT monitors to the very bright light boxes used for interpreting X-ray imagery.
When medical imagery requires a full-color presentation, most medical display systems automatically transition to commercial-style gamma and color standards (e.g., gamma 2.2 and BT.709). High-dynamic-range (HDR) monitors are also gaining traction in the medical field, offering higher brightness, contrast, and a wider color gamut that can more accurately reproduce the range of hues visible to the human eye. Some medical display manufacturers have developed hybrid visualization modes that can process video at a pixel level, delivering detailed and accurate grayscale and color processing simultaneously on a single screen.
Speciality Displays
Every display device found in a hospital or medical setting will offer a set of features that make it particularly well-suited for its intended use case. One common characteristic of medical-grade displays is a design that can withstand the rigors of regular use, which includes thorough cleanings to maintain a hygienic environment. It’s common to see medical displays with metal chassis or encased in anti-bacterial plastics, and most feature ratings for ingress protection against dust and moisture.
Barco JAO18 MKII
The most visible display from the patient’s perspective, while spending time in a hospital room, is the one they depend on to provide a bit of distraction and entertainment. The Barco JAO18 MKII Smart Terminal is a multi-touch, 18.5-inch LED-backlit LCD screen with HD resolution. The otherwise similar JAO21 increases the screen size to 21.5 inches and the pixel resolution to 1080p. The JAO18 can provide patients with access to television programming, video-on-demand services, and internet access. The terminal also features WiFi and Bluetooth connectivity, as well as standard AV inputs for use with external devices, such as media players or game consoles. The JAO18 MKII’s integrated RFID scanner facilitates patient authentication, and an optional wired handset provides enhanced patient control, including a dedicated call button for assistance.
Eizo RadiForce MX317W
For medical professionals examining diagnostic imagery, a monitor like the Eizo RadiForce MX317W can provide enhanced image clarity and consistency while minimizing eye fatigue. The MX317W features a 30.5-inch IPS LCD monitor with a native DCI 4K resolution of 4096 x 2160 pixels. This monitor literally monitors itself, utilizing dedicated sensors to measure backlight luminance and ambient room light, optimizing its video output to a desired target based on user preferences and environmental conditions. An integrated front sensor, built into the MX317W’s bezel, enables software tools to perform calibration verification and adjustments, ensuring consistent performance over the long term.
Eizo RadiForce MX317W – Image credit: Eizo
LG 32HQ713D
The ability to produce well-contrasted imagery is a critical function for video monitors used in medical diagnostic work. The LG 32HQ713D is an impressively bright 31.5-inch display that features the company’s IPS Black panel technology, which claims contrast levels greater than those of many of its competitors. While this 4K monitor offers up to 1000 nits of peak brightness, I was more impressed with its stabilized luminance mode, which can maintain a consistent 500 nits of output, making it well-suited for use in well-lit viewing environments. The 32HQ713D also features integrated down-firing and rear-firing LED lights to enhance document viewing or provide an eye-friendly bias lighting configuration, respectively. The LG 32HQ713D’s internal front calibration sensor enables tool-free display validation and adjustment.
Barco MDSC-8527
The Barco MDSC-8527 is a 4K UHD LCD designed for real-time imaging in an active surgical environment. The display’s 27-inch screen achieves a high pixel density of over 163 pixels per inch (PPI). In addition to providing a DICOM Part 14 mode for grayscale imagery, the MDSC-8527 supports standard video gamma curves, as well as HDR-HLG (hybrid log gamma), and a stabilized 550 nit luminance mode. The 8527 features a chemically strengthened glass screen protector, capacitive touch controls, and a fanless design, together providing improved durability and a system that can withstand regular, necessary cleanings.
Looking Forward
I’m impressed with the forward-thinking approach of the now 40-year-old DICOM standard in treating monochromatic imagery, considering the range of potential luminance levels found in various forms of medical imagery – not to mention the standard’s extensive metadata support. As more medical professionals incorporate color imagery into their diagnostic workflows, the current HDR video standards are well-suited to provide the improved image contrast and detail made possible with high-brightness display technology.
The DICOM GSDF’s requirement for consistent high luminance over time demands a proven and reliable display technology for medical applications – LED-backlit LCDs dominate this sector. Recent improvements in peak luminance and lifespan of OLED displays have not yet convinced medical display manufacturers to adopt them. The light-emitting organic materials in OLED displays remain vulnerable to accelerated wear when driven to produce peak output over extended periods of time.
Medical display manufacturers may require future display technologies, such as inorganic electroluminescent quantum dots, to offer the practically perfect contrast of an emissive display and the pixel wear resistance needed to sustain the consistent high-brightness levels used in modern medical imaging.
Robert is a technologist with over 20 years of experience testing and evaluating consumer electronics devices, primarily focusing on commercial and home theater equipment.
Robert's expertise as an audio-visual professional derives from testing and reviewing hundreds of related products, managing a successful AV test lab, and maintaining continuous education and certifications through organizations such as CEDIA, the Imaging Science Foundation (ISF), and THX.
More recently, Robert has specialized in analyzing audio and video display systems, offering comprehensive feedback, and implementing corrective measures per industry standards. He aims to deliver an experience that reflects the artists' intent and provides coworkers and the public with clear, insightful product information.
- Robert Heronhttps://www.avnation.tv/author/robert-heron/
- Robert Heronhttps://www.avnation.tv/author/robert-heron/
- Robert Heronhttps://www.avnation.tv/author/robert-heron/
- Robert Heronhttps://www.avnation.tv/author/robert-heron/
