QA in Medical Displays: Two Approaches

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 Quality assurance (QA) of medical imaging displays is critical for accurate interpretation of digital images. When it comes to QA, there are as many protocols out there as there are healthcare facilities. They each uniquely tackle what method they want to employ, how often they should calibrate the displays and who is responsible for the process.  Along the way, they update methods and procedures to take advantage of new technological options.

Hands-on method

At Allina Healthcare in Minneapolis, Minn., a large system with 11 hospitals and 39 clinics, the clinical equipment services division, part of IT, is responsible for quality assurance and service of all medical displays and diagnostic imaging equipment. PACS is used at all of the hospitals and several of the clinics handling a terabyte of images every 12 to 16 days, says PACS Administrator Bruce Facile.

The prevalent display in use for imaging needs at Allina is Image Systems grayscale FP2080 3MP. Recently, when they upgraded to color in radiology and cardiology, they chose NEC’s 2190 UXi 2MP color systems.

The cornerstone of Allina’s QA protocol is the tried-and-true method of manual calibration. “Our viewpoint is that you actually need to be in front of the monitor to do a visible inspection as well as calibration,” says Facile. “We want to make sure the clinical equipment services people do a site survey of the monitors so we can look for white pixels, black pixels, scratches on the monitor, defects and all of the other pieces that you can’t do using network calibration software.”

QA is performed by imaging technical specialists and engineers such as Kevin Emerson. “You get baseline luminance and then you gamma-correct the luminance curve, so all four monitors almost all have an equal luminance curve. So if you pull up the same image on all four monitors, there is no difference to the human eye.”

Allina will soon be switching from the Verilum software and puck systems to Image Systems’ self-calibration feature—an onboard front sensor—to do a validation of DICOM and other tests. DICOM Part 3.14, Grayscale Standard Display Function, is one of the standards used by many hospitals to maintain and calibrate displays.  The Image Systems QA solution, Calibration Feedback System, measures conformance of the displays. The newest version has been upgraded to include color calibration and enhanced reporting features.

At this time, Allina is not planning to purchase network software to perform monitor calibration and remote testing. “We have confidence in the stability of our monitors,” says Emerson. “Every day a trained professional is viewing these monitors and making diagnoses. If there is a problem, it’s spotted.”

Going remote with calibration

At Delnor-Community Hospital in Geneva, Ill., a 128-bed hospital that is completely filmless and does approximately 109,000 radiology procedures annually, they rely on network calibration software for QA, says Brian Daily, PACS administrator.

The hospital uses Double Black Imaging’s black and white displays.  The typical workstation configuration is a pair of Double Blacks, IF 2103M (3 MP) or IP 2105M (5 MP) and a 19-inch or 20-inch color display from NEC, which is used primarily to view worklists. 

Delnor relies on Double Black’s network calibration software, LumiCal, for performance testing, calibration and maintenance. “The software resides on a server. You just need to put in all of the different monitor combinations with the serial numbers and tell it to go out at 2 a.m., or whenever you want it to, and it calibrates the systems for you,” says Daily. “We do it once a week.” 

The network management software which can run at any time, allows Daily to adjust luminance levels, create reports, run visual tests and sends automatic alerts if there is a failure with any display on the network, as well as calibrating locally or remotely.

Double Black’s calibration process is performed by several sensors on the displays. “On the 5 MP, the sensor is automatic, it’s stationary and always out; but in the 3 MPs, it motorizes out,” Daily says. The LCDs also come equipped with a backlight sensor for continuous luminance calibration. 

Daily wanted self-calibrating displays, but found that the term doesn’t necessarily mean the same for all vendors. To Daily, it means backlight and front light sensors, being able to calibrate brightness, adjust the black level, white level and contrast and the ability to retrieve reports.

“We wanted to have