Hongye Liang

Image browsing in slow medical liquid crystal displays.

RATIONALE AND OBJECTIVES Statistics show that radiologists are reading more studies than ever before, creating the challenge of interpreting an increasing number of images without compromising diagnostic performance. Stack-mode image display has the potential to allow radiologists to browse large three-dimensional (3D) datasets at refresh rates as high as 30 images/second. In this framework, the slow temporal response of liquid crystal displays (LCDs) can compromise the image quality when the images are browsed in a fast sequence. MATERIALS AND METHODS In this article, we report on the effect of the LCD response time at different image browsing speeds based on the performance of a contrast-sensitive channelized-hoteling observer. A stack of simulated 3D clustered lumpy background images with a designer nodule to be detected is used. The effect of different browsing speeds is calculated with LCD temporal response measurements from our previous work. The image set is then analyzed by the model observer, which has been shown to predict human detection performance in Gaussian and non-Gaussian lumpy backgrounds. This methodology allows us to quantify the effect of slow temporal response of medical liquid crystal displays on the performance of the anthropomorphic observers. RESULTS We find that the slow temporal response of the display device greatly affects lesion contrast and observer performance. A detectability decrease of more than 40% could be caused by the slow response of the display. CONCLUSIONS After validation with human observers, this methodology can be applied to more realistic background data with the goal of providing recommendations for the browsing speed of large volumetric image datasets (from computed tomography, magnetic resonance, or tomosynthesis) when read in stack-mode.

Color measurement methods for medical displays

— The effect of different measurement methods on the characterization of display color, maximum color difference, and luminance uniformity of medical liquid-crystal displays are reported. We use a telescopic colorimeter and a custom-designed collimated probe with an internal lens attached to a spectrometer. The maximum color-difference variations were found to be between 0.0047 to 0.0073, in the same range as variations among methods, displays, and screen locations.

Assessment of Mobile Technologies for Displaying Medical Images

We compared the characteristics of state-of-the-art mobile display systems based on reflective and transmissive liquid crystal displays (LCDs) and an organic light-emitting display with respect to physical characterization metrics and observer studies. Physical performance factors provided information on the differences among display technologies. Observer studies resulted in different system ranking between the task-based performance and user-preference approaches. The results of the physical characterization and preference study showed that the reflective LCD ranked lower. We also found that ambient illumination played a lesser role than previously seen in large-format workstation displays. The methodology developed in this study provides an initial insight into the comparison of alternative technologies for display of diagnostic images in small portable devices.

15.2: Distinguished Paper: Assessment of Temporal Blur-Reduction Methods Using a Computational Observer that Predicts Human Performance

We report on a method to assess the impact of temporal blur reduction techniques based on measured or modeled device temporal characteristics with a contrast-sensitive computational observer that predicts human performance. We applied the method to the comparison of different devices and temporal blur reduction approaches.

73.5L: Late‐News Paper: Observer Strategies for Assessment of Temporal Response — Effect of Technology

We compare the detection performance of human observers in LCDs and CRTs using artificial complex backgrounds. Our results suggest that the degradation in performance at high browsing speeds observed in LCDs is not seen or much more subtle in CRTs, even at 50 frames per second.

P‐244L: Late‐News Poster: Noise and Resolution in a Dual‐Layer LCD

The noise and resolution characteristics of a dual-layer LCD capable of high luminance range are presented with emphasis on the measurement and analysis methods considering the parallax effect. The results are compared to an identical panel with a single-layer structure.

Assessment of temporal display using observers

Most assessments of display performance are limited to studying the display quality for static images. However, dynamic scenes constitute a large fraction of medical images and are becoming more widespread due to the increase in the number of images to be interpreted. The image quality of a dynamic scene is affected by the displays temporal characteristics and the human visual systems temporal response. We propose to use a computational observer to understand the effect of image browsing speed in medical displays. We use a 3D cluster lumpy background to study the effect of different browsing speeds using liquid crystal display (LCD) temporal response measurements reported in our previous work. The image set is then analyzed by the computational observer. This allows us to quantify the effect of slow temporal response of medical LCDs on the performance of the anthropomorphic observer. Slow temporal response of the display device affects the lesion contrast and the observer performance. Human visual system also adds to the complexity of image perception of dynamic scenes. A human observer study was used to validate the computational observer results.

Assessment of display temporal response using a computational observer

— Temporal response is one of the major concerns for liquid-crystal-display (LCD) performance. Fast response time is preferred for high-fidelity image rendering. Several methods have been proposed to improve the LCD temporal performance. A method to assess the impact of temporal responses based on measured or modeled device temporal characteristics with a contrast-sensitive computational observer that is intended to predict human performance is reported. A method to compare different devices and temporal blur reduction approaches has been applied. It was found that slow temporal response of the display device greatly affects signal contrast and observer performance. This methodology, after validation with human observers, could be used to compare different displays with different inter-gray-level transition time profiles.

Effect of slow display on stack-mode reading of volumetric image datasets using an anthropomorphic observer

Active-matrix liquid crystal displays (LCDs) are becoming widely used in medical imaging applications. With the increasing volume of CT images to be interpreted per day, the ability of showing a fast sequence of images in stack mode is preferable for a medical display. Slow temporal response of LCD display can compromise the image quality/fidelity when the images are browsed in a fast sequence. In this paper, we report on the effect of the LCD response time at different image browsing speeds based on the performance of a contrast-sensitive channelized-Hotelling observer. A correlated stack of simulated cluster lumpy background images with a signal present in some of the images was used. The effect of different browsing speeds is calculated with LCD temporal response measurements established in our previous work. The image set is then analyzed by the model observer, which has been shown to predict human detection performance in non-Gaussian lumpy backgrounds. This allows us to quantify the effect of slow temporal response of medical liquid crystal displays on the performance of the anthropomorphic observer. Slow temporal response of the display device greatly affects the lesion contrast and observer performance. This methodology, after validation with human observers, could be used to set limits for the rendering speed of large volumetric image datasets (from CT, MR, or tomosynthesis) read in stack-mode.

9.2: Temporal and Color Measurements in Medical Displays

We report on the accurate characterization of temporal response, maximum color difference and luminance uniformity in medical liquid crystal displays. We find that the variability among results from different methods can be larger than measured color differences, and that poor response time estimates occur for transitions between neighboring gray levels.