Paul A. Boynton

American Telemedicine Association's practice guidelines for teledermatology

The ATA assembled a group of experts to develop practice guidelines for teledermatology. This document represents the body of work that this distinguished group assembled. It was approved by the ATA Board of Directors and is presented here in its entirety.

Consistency and Standardization of Color in Medical Imaging: a Consensus Report

This article summarizes the consensus reached at the Summit on Color in Medical Imaging held at the Food and Drug Administration (FDA) on May 8–9, 2013, co-sponsored by the FDA and ICC (International Color Consortium). The purpose of the meeting was to gather information on how color is currently handled by medical imaging systems to identify areas where there is a need for improvement, to define objective requirements, and to facilitate consensus development of best practices. Participants were asked to identify areas of concern and unmet needs. This summary documents the topics that were discussed at the meeting and recommendations that were made by the participants. Key areas identified where improvements in color would provide immediate tangible benefits were those of digital microscopy, telemedicine, medical photography (particularly ophthalmic and dental photography), and display calibration. Work in these and other related areas has been started within several professional groups, including the creation of the ICC Medical Imaging Working Group.

21.4: Compensation for Stray Light in Projection Display Metrology

Electronic projection display specifications are often based on measurements made in ideal darkroom conditions and assume ideal measurement instrumentation. However, not everyone has access to such a facility, and the light-measuring devices may not necessarily provide the desired information. Simple tools are discussed that address some of these concerns.

Stray light elimination in making projection display measurements

Electronic front-projection display specifications are often based on measurements made in ideal darkroom conditions. However, not everyone has access to such a facility. In many environments, ambient light from other sources in the room illuminates the screen. This includes room lights directly illuminating the screen and the reflection of these light sources off of walls, floors, furniture, and other objects. Additionally, back-reflections from the projection screen must be considered. These stray light components contribute to the measured value, giving an inaccurate measurement of the projector light output. Thus, these conditions may make the task of adequately comparing and evaluating different projection systems difficult. We can better verify whether the projector is operating according to its specifications or compare its performance with other projectors by compensating for stray light. A simple projection mask constructed from black plastic and a stray-light elimination tube are presented as solutions that can provide an accurate measurement of projector light output in many ambient light conditions.

Color Error in the Digital Camera Image Capture Process

The color error in images taken by digital cameras is evaluated with respect to its sensitivity to the image capture conditions. A parametric study was conducted to investigate the dependence of image color error on camera technology, illumination spectra, and lighting uniformity. The measurement conditions were selected to simulate the variation that might be expected in typical telemedicine situations. Substantial color errors were observed, depending on the measurement conditions. Several image post-processing methods were also investigated for their effectiveness in reducing the color errors. The results of this study quantify the level of color error that may occur in the digital camera image capture process, and provide guidance for improving the color accuracy through appropriate changes in that process and in post-processing.

33.3: Small‐Area Black Luminance Measurements on White Screen Using Replica Masks

Luminance measurements of small areas of black pixels on white-screen backgrounds are often used as metrics in display measurements, such as character-stroke contrasts or deep modulation transfer functions. Serious errors may be made in measurements and subsequent ergonomic conclusions if glare contributions of the measurement are not considered. We show a simple method for accounting for glare corruption of luminance measurements by using replica masks.

A survey of the components of display-measurement standards

Several display standards are reviewed and distinctive elements are compared. With flat panel displays becoming more common and the CRT displays being so well established, the associated standards activities can be somewhat bewildering, even overwhelming. This paper attempts to identify complementary and inconsistent elements of related display standards.

Liquid-filled camera for the measurement of high-contrast images

Light-measurement instrumentation based upon high-quality charge-coupled-devices (CCD) is currently in use for measuring the characteristics of electronic displays. When such array detectors are used to measure scenes or images having high contrasts or wide color variations, they can suffer from the effects of veiling glare or lens flare and thereby inaccurately measure the darker luminances because of a mixing of the scene luminances or colors. A liquid-filled simulated-eye design (SED) camera was constructed to improve the ability to measure such images by reducing the internal scattering that contributes to the veiling glare. This paper discusses the investigation of the use of various liquids, in particular the effects of scattering within the liquids.

LCD display screen performance testing for handheld thermal imaging cameras

Handheld thermal imaging cameras are an important tool for the first responder community. As their use becomes more prevalent, it will become important for a set of standard test metrics to be available to characterize the performance of these cameras. A major factor in the performance of the imagers is the quality of the image on a display screen. An imager may employ any type of display screen, but the results of this paper will focus on those using liquid crystal displays. First responders, especially firefighters, in the field rely on the performance of this screen to relay vital information during critical situations. Current research on thermal imaging camera performance metrics for first responder applications uses trained observer tests or camera composite output signal measurements. Trained observer tests are subjective and composite output tests do not evaluate the performance of the complete imaging system. It is the goal of this work to develop a non-nondestructive, objective method that tests the performance of the entire thermal imaging camera system, from the infrared destructive, sensor to the display screen. Application of existing display screen performance metrics to thermal imaging cameras requires additional consideration. Most display screen test metrics require a well defined electronic input, with either full black or white pixel input, often encompassing detailed spatial patterns and resolution. Well characterized thermal inputs must be used to obtain accurate, repeatable, and non-destructive display screen measurements for infrared cameras. For this work, a thermal target is used to correlate the measured camera output with the actual display luminance. A test method was developed to determine display screen luminance. A well characterized CCD camera and digital recording device were used to determine an electro-optical transfer function for thermal imaging cameras. This value directly relates the composite output signal to the luminance of the display screen, providing a realistic characterization of system performance.

Stray light compensation in small area contrast measurements of projection displays

The accurate measurement of small area-black levels is important in projection display characterization. For example, techniques can be used to determine resolution of projection systems by measuring the contrast of alternating grille patterns or fully-modulated sine waves of various spatial frequencies. Unfortunately, the measurement of the contrast of these patterns may be influenced by stray light, either from ambient and reflected light in the environment, or from veiling glare scatter in the lens of the light-measuring device. Such stray-light corruption can lead to large errors in contrast determination, providing an inaccurate characterization of the projector. For large-area measurements, various techniques have been employed, including the use of frustums and masks, to minimize such unwanted effects and provide a more accurate measurement. With some modifications, these same tools may be used for small-area measurements with similar results. The design, construction, and implementation of these tools will be discussed. Results will be shown comparing small-area contrast measurements of projection systems, including resolution determination, with and without stray light compensation, for different measurement instrumentation.