Performance evaluation of a commercial system for quantitative measurement of display resolution
One of the key metrics that carry information about image quality of medical displays is resolution. Until now, this property has been quantitatively assessed in laboratory settings. For the first time, a device consisting of a CCD camera and analysis software has been made commercially available for measuring the resolution of medical displays in a clinical setting. This study aimed to evaluate this new product in terms of accuracy and precision. In particular, attention was paid to determine whether the device is appropriate for clinical use. This work involved the measurement of the Modulation Transfer Function (MTF) of a medical Liquid Crystal Display (LCD) using the software/camera system. To check for accuracy, the results were compared with published values of the resolution for the same display. To assess the system's precision, measurements were made multiple times at the same setting. The performance of the system was also ascertained as a function of the focus setting of the camera. In terms of repeatability, the results indicate that when the camera is focused within ±0.64 mm of the optimum focus setting, the MTF values lie within approximately 14% of the best focus MTF at the Nyquist frequency and 11% of the optimum total sharpness (JMTF df). Similar results were obtained in the horizontal and vertical directions. Also, the MTF results track with luminance values as expected. In terms of accuracy, the device provides MTF figures within 10% to 20% of the previously measured values.
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