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1.  Automatic Monitoring of Localized Skin Dose with Fluoroscopic and Interventional Procedures 
Journal of Digital Imaging  2010;24(4):626-639.
This software tool locates and computes the intensity of radiation skin dose resulting from fluoroscopically guided interventional procedures. It is comprised of multiple modules. Using standardized body specific geometric values, a software module defines a set of male and female patients arbitarily positioned on a fluoroscopy table. Simulated X-ray angiographic (XA) equipment includes XRII and digital detectors with or without bi-plane configurations and left and right facing tables. Skin dose estimates are localized by computing the exposure to each 0.01 × 0.01 m2 on the surface of a patient irradiated by the X-ray beam. Digital Imaging and Communications in Medicine (DICOM) Structured Report Dose data sent to a modular dosimetry database automatically extracts the 11 XA tags necessary for peak skin dose computation. Skin dose calculation software uses these tags (gantry angles, air kerma at the patient entrance reference point, etc.) and applies appropriate corrections of exposure and beam location based on each irradiation event (fluoroscopy and acquistions). A physicist screen records the initial validation of the accuracy, patient and equipment geometry, DICOM compliance, exposure output calibration, backscatter factor, and table and pad attenuation once per system. A technologist screen specifies patient positioning, patient height and weight, and physician user. Peak skin dose is computed and localized; additionally, fluoroscopy duration and kerma area product values are electronically recorded and sent to the XA database. This approach fully addresses current limitations in meeting accreditation criteria, eliminates the need for paper logs at a XA console, and provides a method where automated ALARA montoring is possible including email and pager alerts.
PMCID: PMC3138926  PMID: 20706859
Peak skin dose; sentinal event; DICOM structured report dose; patient entrance reference point; fluoroscopy; interventional radiology; Joint Commission (JC); radiation dose; Digital Imaging and Communications in Medicine (DICOM)
2.  Introduction to Grayscale Calibration and Related Aspects of Medical Imaging Grade Liquid Crystal Displays 
Journal of Digital Imaging  2007;21(2):193-207.
Consistent presentation of digital radiographic images at all locations within a medical center can help ensure a high level of patient care. Currently, liquid crystal displays (LCDs) are the electronic display technology of choice for viewing medical images. As the inherent luminance (and thereby perceived contrast) properties of different LCDs can vary substantially, calibration of the luminance response of these displays is required to ensure that observer perception of an image is consistent on all displays. The digital imaging and communication in medicine (DICOM) grayscale standard display function (GSDF) defines the luminance response of a display such that an observer’s perception of image contrast is consistent throughout the pixel value range of a displayed image. The main purpose of this work is to review the theoretical and practical aspects of calibration of LCDs to the GSDF. Included herein is a review of LCD technology, principles of calibration, and other practical aspects related to calibration and observer perception of images presented on LCDs. Both grayscale and color displays are considered, and the influence of ambient light on calibration and perception is discussed.
PMCID: PMC3043865  PMID: 17333412
Medical imaging grade liquid crystal displays (LCDs); DICOM GSDF; observer perception; ambient light
3.  Determining the Sharpness of Electronic Image Displays: An Evaluation of Three Methods  
Journal of Digital Imaging  2001;14(2):83-91.
The authors evaluated 3 methods developed to assess the level of monitor cathode ray tube (CRT) sharpness. Results include a comparison of 2 observer-based methods to a charged coupled device (CCD) digital camera-based method for the purposes of CRT equipment comparison, acceptance testing, and routine CRT quality control. Three methods designed to measure a monitor's sharpness were evaluated on a single 20-inch CRT monitor. We defined signal-to-noise ratio (SNR) to be the overall signal difference measured by each method from the highest to lowest values divided by the average standard deviation of the measurements. Comparing the results of the 3 methods, the authors found that the digital CCD camera-based method provided a much higher SNR than the 2 observer-based methods and, therefore, is the preferred of the 3 methods for measuring the sharpness of CRT displays. The SNR values for the CCD, Cx and line target methods were 151.5, 4.9, and 4.3, respectively. The Cx target observer-based method (a novel target and scoring routine dubbed the "Cx" target because of its appearance) had a higher SNR than the line target observer-based method. The average time and standard deviation required to score the Cx and the line targets were 5.45 +/- 2.15 minutes and 8.34 +/- 2.95 minutes, respectively. The observer-based method results (and variability) versus the camera-based method results (and variability) indicate strong linear relationships. Exploring this finding and the optimization of the camera-based method are the subjects of future research.
PMCID: PMC3452757  PMID: 11440258
4.  Optimization of a contrast-detail-based method for electronic image display quality evaluation 
Journal of Digital Imaging  1999;12(2):60-67.
The authors previously reported a general technique based on contrast-detail methods to provide an overall quantitative evaluation of electronic image display quality. The figure-of-merit reflecting overall display quality is called maximum threshold contrast or MTC. In this work we have optimized the MTC technique through improvements in both the test images and the figure-of-merit computation. The test images were altered to match the average luminance with that observed for clinical computed radiographic images. The figure-of-merit calculation was altered to allow for contrast-detail data with slopes not equal to −1. Preliminary experiments also were conducted to demonstrate the response of the MTC measurements to increased noise in the displayed image. MTC measurements were obtained from five observers using the improved test images displayed with maximum monitor luminance settings of 30-, 50-, and 70-ft-Lamberts. Similar measurements were obtained from two observers using test images altered by the addition of a low level of image noise. The noise-free MTC and MTC difference measurements exhibited standard deviations of 0.77 and 1.55, respectively. This indicates good measurement precision, comparable or superior to that observed using the earlier MTC technique. No statistically significant image quality differences versus maximum monitor luminance were seen. The noise-added MTC measurements were greater than the noise-free values by an average of 4.08 pixel values, and this difference was statistically significant. This response is qualitatively correct, and is judged to indicate good sensitivity of the MTC measurement to increased noise levels.
PMCID: PMC3452489  PMID: 10342248
contrast-detail experiments; electronic image display; image quality evaluation
5.  Quantitative evaluation of overall electronic display quality 
Journal of Digital Imaging  1998;11(Suppl 1):180-186.
This study indicates that contrast-detail data should be very helpful in providing quantitative measurements of overall electronic display quality. The method would be suitable for new equipment selection, acceptance testing, and quality control. The recommended protocol would only involve observer data obtained using test images with mid-range background pixed values. Improvements to the current linear curve fit may also provide increased levels of measurement precision and sensitivity. To put the measurements in proper context, MTC measurements of a group of displays currently in use and deemed acceptable for the clinical display) should be obtained by a group of observers, if possible.
When making quantitative recommendations regarding equipment selection, or display configuration (eg, maximum display luminance or ambient room lighting levels), a group of observers should be used, since the decisions made will presumably affect a large number of radiologists, technologists or clinical physicians using the display workstations. With a group of five observers, and using the group paired difference analysis technique, measurement precision will be 9.0%, and sensitivity to MTC changes will be 11.1%. Each set of raw data for a measurement of MTC can be collected and analyzed for each observer in approximately 30 minutes, so data sufficient for a comparison of two devices could be collected and analyzed within an hour.
When making measurements for equipment acceptance testing or routine QC measurements (eg, on a quarterly or twice-yearly basis), measurements from a single observer should suffice since the goal is an assessment of the relative performance of an individual device. Precision of the single observer MTC measurements will be 6.8%, and sensitivity will be 15.2%. Measurements made over a period of time should have a reproducibility of about 5%.
PMCID: PMC3453343  PMID: 9735464

Results 1-5 (5)