Mode of failure and detection can be important. Back in the day of thermal printers, a blown pixel was a common failure mode, however, in practice, this failure mode is quite detectable and clear. A blown pixel will result in a very straight line through the entire image. What was more a concern was partially failing pixels or delta in resistance causing unnoticeable image changes that could impact diagnosis. For the blown pixel, we knew the radiologist (Based on lots of customer feedback and tech support notes) would stop using the printer for diagnosis. For the pixel resistance change, we implemented an onboard pixel tester that verified the resistance of all pixels frequently and if a pixel was off alerted the user. The radiologist may continue using the broken printer but he is made aware on the image output a small caption says "Image adjustment required"