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PubMed1997

Clinical assessment of Hokkaido University PACS.

The paper describes the hardware and software used in the Hokkaido University picture archiving and communication system (HUPACS), which has been in use for the past two years. An evaluation of the system is also included. Fuji computed radiography completely replaces conventional X-ray radiographs, and 10:1 data compression is routinely employed. The PACS LAN is connected to the hospital information system through the main-frame computer and it is linked, not only to the radiology department, but also to the outpatient clinics. Image data have been steadily stored in the optical disc library, which contains more than 200,000 images. The original image can be accessed within 1 min. Image quality on a cathode ray tube (CRT) is clinically acceptable. Nevertheless, the transfer time of a newly made image is prolonged in some cases, during periods of heavy usage of the system. During scheduled radiology conferences, image reading tends to take more time on a CRT than on film. An improvement in the ease of operation of the workstations is necessary for full acceptance of CRT diagnoses. Generally speaking, however, HUPACS is working well and is appreciated by most of the clinicians.

Computer Systems↗
PubMed1983

Intraarterial digital subtraction angiography: a comparative view.

Intraarterial digital subtraction angiography (IA DSA) was performed in 122 patients undergoing a variety of diagnostic and interventional angiographic procedures. Owing to the increased contrast resolution of DSA, diluted contrast material in concentrations of from 12-19% could be employed, thereby significantly reducing contrast material doses compared to doses used with conventional film-screen angiography or intravenous DSA. Patient discomfort was convincingly reduced due to the injection of dilute contrast material. Subtracted digital images could be viewed immediately on a cathode ray tube (CRT) resulting in faster procedures with less catheter time. Savings in film costs relative to conventional angiography were also achieved.

Angiography↗
PubMed1986

An anesthesia information system for monitoring and record keeping during surgical anesthesia.

We have developed an anesthesia information system (AIS) that supports the anesthesiologist in monitoring and recording during a surgical operation. In development of the system, emphasis was placed on providing an anesthesiologist-computer interface that can be adapted to typical situations during anesthesia and to individual user behavior. One main feature of this interface is the integration of the input and output of information. The only device for interaction between the anesthesiologist and the AIS is a touch-sensitive, high-resolution color display screen. The anesthesiologist enters information by touching virtual function keys displayed on the screen. A data window displays all data generated over time, such as automatically recorded vital signs, including blood pressure, heart rate, and rectal and esophageal temperatures, and manually entered variables, such as administered drugs, and ventilator settings. The information gathered by the AIS is presented on the cathode ray tube in several pages. A main distributor page gives an overall view of the content of every work page. A one-page record of the anesthesia is automatically plotted on a multicolor digital plotter during the operation. An example of the use of the AIS is presented from a field test of the system during which it was evaluated in the operating room without interfering with the ongoing operation. Medical staff who used the AIS imitated the anesthesiologist's recording and information search behavior but did not have responsibility for the conduct of the anesthetic.

Anesthesia Department, Hospital↗
PubMed2000

Contrast-detail characteristic evaluations of several display devices.

The contrast-detail characteristic of a display system is a powerful tool for evaluating displayed image quality. It takes into account the physical properties of the display, the psychophysical aspects of the observer, and the viewing conditions. It is a more sensitive measurement of the displayed image quality than a simple Society of Motion Picture and Television (SMPTE) pattern. Yet, it is relatively simple to measure and requires no special equipment or analysis tools. In this presentation, the results of the evaluation of several cathode ray tube (CRT) monitors and a digital projector will be presented. Contrast-detail characteristics of these display devices were measured under various gamma and display settings. The results show excellent intraobserver and interobserver variance (<1 step on the grayscale). Extraneous light, such as room lighting, affects the contrast threshold more severely at low background levels more than at high background. Gamma settings on graphics adapters affect the shapes of the contrast-detail curve for all display types. Gamma settings of approximately 2.0 result in a better contrast threshold for both high and low background brightness. The results show complex differences in contrast-detail characteristics for different display types. The digital projector display not only has significantly worse performance than CRT monitors, but also is affected more by extraneous light. High-brightness monitors with optimal monitor and graphics adapter settings have better performance than color or low-brightness monitors. However, under some settings, the performance of high-brightness monitors is not always better at all object sizes and background levels.

Computer Terminals↗
PubMed1992

Quality monitoring of soft-copy displays for medical radiography.

As presentation of medical radiographic images on soft-copy displays (cathode ray tubes) becomes increasingly prevalent in electronic radiography, methods of quality assurance must be developed to ensure that radiologists can effectively transfer film-based reading skills. Luminance measurements provide the basis for evaluating the state of soft-copy displays. An integrated approach has been implemented at Mallinckrodt Institute of Radiology (MIR, Washington University, St Louis, MO) that facilitates measurement of geographically distributed soft-copy displays with centralized data logging, performance tracking, and calibration. MIR's central radiology image manager exercises the display station that drives the monitor, harvests the measurement data, stores the results, and submits the resulting data for additional processing. The luminance measurements are collected by a small, portable, photometric instrument designed at MIR that includes a serial port that is accessed via local area terminal service supported by the radiology image manager. The design details of the photometric instrument and example luminance characteristics of several soft-copy displays used at MIR are presented in this report.

Computer Peripherals↗
PubMed1995

Image quality control for digital mammographic systems: initial experience and outlook.

This report presents (1) a broad topical review and a tutorial of the possibilities for image quality control (IQC) with digital systems, and (2) results and initial experience for IQC with two commercial digital imaging systems, but with limited discussion on any particular method. Digital imaging systems used for mammographically guided digital stereotactic breast biopsy were evaluated extensively at the University of Arizona. Measurements were made of linearity, sensitivity, signal-to-noise ratio, and square-wave modulation. Images of phantoms such as the American College of Radiology Accreditation Phantom and the contrast detail mammography Phantom were evaluated as well as images of the x-ray source's focal spot. The evaluation also included the cathode ray tubes for the imaging systems. The data collected show that digital imaging systems have an important advantage over film-screen systems because they provide a digital signal as output that can be used for quantitative analysis. As a result, IQC can become a much more quantitative discipline than presently practiced, providing more information on the imaging systems under evaluation, and providing better control over their properties during actual operation.

Computer Terminals↗
PubMed1991

Picture archiving and communication system in Hokkaido University Hospital: advantage and disadvantage of HU-PACS chest roentgenogram images in the outpatient clinic.

A new Hokkaido University picture archiving and communication system (HU-PACS) has been in clinical use in the outpatient clinic at HU Hospital. To evaluate the quality of the cathode-ray tube (CRT) monitor images, we compared the detectability of line shadows in the chest roentgenogram images on the CRT monitor with those on the computed radiography (CR) film. We randomized chest roentgenograms from 20 patients who were admitted to the outpatient clinic with pulmonary disease. Two physicians, whose speciality is chest roentgenogram diagnosis, checked whether they could recognize a horizontal fissure line (hairline) on the posteroanterior view and a minor fissure line and major fissure lines on the lateral view. Only 30% of hairlines were recognized on CRT monitor as compared with 65% on CR film. On the lateral view, only 68% of major fissures and 53% of minor fissures on CRT monitor were recognized as compared with 89% and 79%, respective on CR film. Furthermore, it was somewhat difficult to follow entire lines on some of the CRT monitor images. Clinically, the greatest advantage of the PACS is immediate availability of images, including chest roentgenogram, chest computed tomography (CT) and magnetic resonance imaging (MRI). PACS is also convenient for consulting colleagues in other departments. Unfortunately, the quality of the image on the CRT monitor is not yet good enough to visualize line shadows and small solitary lesions on the chest roentgenogram image. Recent advances in high technology have been so rapid, however, that higher resolution CRT monitors will be available soon.

Computer Terminals↗
PubMed1991

Management and clinical utilization of computed tomography, magnetic resonance imaging, and angiography in Hokkaido University Hospital picture archiving and communication system.

We made a preliminary assessment of the Hokkaido University picture archiving and communication system (HU-PACS). Data access time from either imaging machines or data base to workstations was 1.5 minutes, which is great benefit for data communication in routine examinations. Image quality of the work station was estimated in terms of brain computed tomography (CT) and digitized cerebral angiograms. Cerebral infarction was definitely observed on the cathode-ray tube (CRT) monitor of the work station. Although the picture quality of CRT was acceptable, we had to manipulate window level and width for CRT diagnosis of cerebral angiography. Data compression was routinely used without significant degradation of those image quality. Nevertheless, further improvement of maneuverability of the workstation should be considered.

Angiography, Digital Subtraction↗
PubMed1991

Three monochrome displays from a single, true color video display controller.

Some nuclear medicine computer displays, as well as many image processing workstations are "true color" machines characterized by independent memory and grey scale mapping for each of the red, green and blue color channels. Other color image display systems produce a color image from a single grey scale map composed of red, green, and blue intensity values ("pseudo color"). In the true color system the final image is obtained by overlays of three independent color images. In an effort to present complete nuclear medicine studies for diagnosis from cathode-ray tubes (CRTs) we have employed a true color display to present three times as much spatial information as the system was designed for by directing each color output from the display controller to a different monochrome black and white (b/w) monitor. Therefore our system displays a 512 x 512 x 24-bit true-color image, or three 512 x 512 x 8-bit monochrome images, or any combination of smaller size matrices. Monitor requirements, cabling, and general software considerations are detailed here. The ability to display complete nuclear medicine studies on CRTs (as currently presented on film) has been provided by adding monitors and software revisions to a commercially available nuclear medicine computer system.

Color↗
PubMed2000

Quantitative analysis using the star volume method applied to skeleton patterns extracted with a morphological filter.

In this study, a morphological filter was combined with star volume analysis and applied to digital images to determine its potential usefulness in assessing trabecular structure. Three digital "geometric" test patterns (square, rectangle, circle) were created on a CRT (cathode ray tube). Each shape was arranged into five groups by size to yield 15 final "skeletal" patterns that were subsequently assessed with star volume analysis. Also, three digital X-ray images (background, soft tissue, bone block) were processed with a morphological filter to create three sets of 11 skeletal patterns each. These patterns were also assessed with star volume analysis and the ratio of extracted skeletal elements (in pixel numbers) to total pixel numbers was expressed as the pixel percentage. Star volume analysis was then applied to these digital skeletal images to yield the volume of extracted "skeletal" trabecular elements (Vsk) and the volume of nonskeletal (marrow space) elements (Vsp). The Vsk and Vsp were compared for all the different skeletal patterns. The pixel percentages were then compared to the star volume results for the X-ray test patterns. The Vsk decreased and Vsp increased as the number of operations (n) increased for both digital X-ray images and the geometric test patterns when the X-ray images were depicted by pixel percentages. Also, all true bone test patterns were clearly different both visually and quantitatively when compared to the noise skeletons extracted from background and soft tissue. Therefore, as Vsk was increased, so was connectivity. It can be concluded that the application of morphological filters and star volume analysis may be a useful tool in quantitatively determining the characteristics and continuity of trabecular skeletal structures. Further studies involving a larger number of bone samples and using models to compare measurements of calculated versus actual volume should reveal the true potential of this method for evaluating bone structure and its relationship to bone strength and also increase the tools available for evaluating bone diseases such as osteoporosis.

Femur↗
PubMed2005

The influence of liquid crystal display (LCD) monitors on observer performance for the detection of nodular lesions on chest radiographs.

PURPOSE: To access the influence of liquid crystal display (LCD) monitors on the detectability of nodular lesions depicted on chest radiographs by comparing them with a high-resolution cathode ray tube (CRT) monitor. MATERIAL AND METHODS: Ten radiologists interpreted 247 soft-copy images on LCD monitors with pixel arrays of 1,024x1,280, 1,200x1,600, 1,536x2,048 and 2,048x2,560, and a CRT monitor with a pixel array of 2,048x2,560, and were asked to indicate their individual confidence levels regarding the presence of a nodule. These images were chest radiographs with and without a lung nodule from the "Standard Digital Image Database" created by the Japanese Society of Radiological Technology. The luminance distributions of all monitors were adjusted to the same, and the ambient illumination was 200 lux. Observer performance was analyzed in terms of the receiver-operating characteristics. RESULTS: No significant statistical differences in nodule detection performance were found among the four LCD monitors and the CRT monitor. CONCLUSION: The nodule detection performance on the LCD monitors with a spatial resolution higher than a matrix size of 1,024x1,280 was found to be equivalent to that on the high-resolution CRT monitor.

Analysis of Variance↗
PubMed2001

Evaluation of the usability of two types of image display systems, during laparoscopy.

BACKGROUND: This study was performed to assess the optimal display location of a flat-screen monitor for laparoscopy. It was also performed to assess the posture (objective), opinion, and preference (subjective) of subjects using a flat-screen monitor positioned in the optimal display location and a cathode-ray tube monitor on a tower next to the operating table (current situation). METHODS: Twelve surgeons performed cholecystectomies using the two display systems alternately. The postures of the operator and the assistant were assessed by an infrared video analysis system. RESULTS: The posture of the assistant is significantly better when using a flat-screen monitor [more neutral head flexions (p = 0.036) and neutral neck torsions (p = 0.012)]. No significant differences were found for the posture of the operator. The operators and assistants felt more comfortable when using a flat-screen monitor (p = 0.008) and they preferred this display to the use of a monitor on a tower. CONCLUSIONS: The use of flat-screen monitors is better for the physical and psychological comfort of the users, even though the technical performance is inferior in comparison with that of regular monitors.

Cholecystectomy↗
PubMed2006

Optimum view distance for laparoscopic surgery.

BACKGROUND: Proper visualization of the surgical field without fatigue is essential in laparoscopic surgery and reduces the risk of iatrogenic injuries. One of the important factors influencing visualization is the viewing distance between the surgeon and the monitor. This was the subject of the current investigation. METHODS: For this study, 14 surgeons participated in experiments designed to determine two working distances from a standard 34-cm (14 in. diagonal) cathode ray tube (CRT) monitor: (a) the maximum view distance permitting small prints of a near vision chart to be identified clearly by sight, (b) and the minimum view distance (of a standard resolution chart) just short of flicker, image degradation, or both. The range of the monitor optimal working distance for laparoscopic surgery was extrapolated from these data sets. RESULTS: The maximum view distance allowing identification of detail averaged 221 cm (range, 166-302 cm). The mean minimal view distance short of flicker/image degradation was 136 cm (range, 102-168 cm). The coefficient of variation for the two view distances was almost identical (18% vs 17%, respectively), and a frequency histogram confirmed the normality of the two data sets. Thus, for most surgeons, the extrapolated monitor view distances for laparoscopic surgery using a 14-in. diagonal (34-cm) monitor range from 139 to 303 cm (57-121 in.) for maximal distance viewing and from 90 to 182 cm (36-73 in.) for close-up viewing (i.e., a monitor optimal working distance ranging from 90 to 303 cm (36-121 in.). CONCLUSIONS: For most surgeons operating from a 14-in. diagonal CRT monitor, both the maximal and minimal (close-up) view distances are individually variable, but the surgeon should never be farther than 3 m (10 ft) or less than 0.9 m (3 ft) from the monitor. However, within limits, the maximal view distance increases with increasing monitor size. The limit for close-up distance is 0.9 m, irrespective of monitor size.

Clinical Competence↗
PubMed2001

Determining the sharpness of electronic image displays: an evaluation of three methods.

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.

Data Display↗
PubMed2002

Implementing the DICOM Grayscale Standard Display Function for mixed hard- and soft-copy operations.

The aim of this work was to implement the DICOM Grayscale Standard Display Function (GSDF) at all stages of image presentation for computed radiography (CR) and direct digital radiography (DR) modalities. Cathode-ray tubes (CRT) were calibrated according to vendor procedures. Printer look-up-tables (LUT) were measured. Custom LUTs were created and loaded. Fuji CR gradation processing parameters were adjusted to accommodate a GSDF printer LUT. Conformance to the GSDF for hard-copy and soft-copy displays was measured with DICOM Part 14 procedures. One system was intended to completely incorporate the GSDF, although the hard-copy result was correct. The CR systems required creation of custom GSDF printer LUTs, adjustment of gradation processing parameters, and/or calibration of CRT luminance response at the quality control station. The picture archiving and communication system workstations from one vendor required third-party software for calibration. Current implementations of DICOM GSDF by vendors may be inconsistent or nonexistent. Significant effort by in-house staff must be expended to properly incorporate the GSDF.

Data Display↗
PubMed2004

SCAR R&D Symposium 2003: comparing the efficacy of 5-MP CRT versus 3-MP LCD in the evaluation of interstitial lung disease.

The efficacy of two medical-grade, self-calibrating, gray scale displays were compared with regard to impact on sensitivity and specificity for the detection of interstitial lung disease (ILD) on computed radiographs (CR). The displays were a 5-megapixel (MP) cathode ray tube (CRT) device and a 3-MP liquid crystal display (LCD). A sample consisting of 230 anteroposterior (AP), posteroanterior (PA), and lateral views of the chest with CT-proven findings characteristic for ILD as well as 80 normal images were compared. This double-blinded trial produced a sample sufficient to detect if the sensitivity of the LCD was 10% or more reduced (one-sided) from the "gold standard" CRT display. Both displays were calibrated to the DICOM gray scale standard and the coefficient of variation of the luminance function varied less than 2% during the study. Five board-certified radiologists specializing in thoracic radiology interpreted the sample on both displays and the intraobserver Az (area under the ROC curve) showed no significant correlation to the display used. In addition, an interobserver kappa analysis showed that the relative disagreement between any observer pair remained relatively constant between displays, and thus was display invariant. This study demonstrated there is no significant change in observer performance sensitivity on 5-MP CRT versus 3-MP LCD displays for CR examinations demonstrating ILD of the chest.

Calibration↗
PubMed2004

Use of a human visual system model to predict observer performance with CRT vs LCD display of images.

This Project evaluated a human visual system model (JNDmetrix) based on just noticeable difference (JND) and frequency-channel vision-modeling principles to assess whether a Cathode ray tube (CRT) or a liquid crystal display (LCD) monochrome display monitor would yield better observer performance in radiographic interpretation. Key physical characteristics, such as veiling glare and modulation transfer function (MTF) of the CRT and LCD were measured. Regions of interest from mammographic images with masses of different contrast levels were shown once on each display to six radiologists using a counterbalanced presentation order. The images were analyzed using the JNDmetrix model. Performance as measured by receiver operating characteristic (ROC) analysis was significantly better overall on the LCD display (P = 0.0120). The JNDmetrix model predicted the result (P = 0.0046) and correlation between human and computer observers was high (r (2) (quadratic) = 0.997). The results suggest that observer performance with LCD displays is superior to CRT viewing, at least for on-axis viewing.

Breast Neoplasms↗
PubMed2005

Solution for nonuniformities and spatial noise in medical LCD displays by using pixel-based correction.

Liquid crystal displays (LCD) are rapidly replacing cathode ray tube displays (CRT) for medical imaging. LCD technology has improved significantly in the last few years and has important advantages over CRT. However, there are still some aspects of LCD that raise questions as to the usefulness of liquid crystal displays for very subtle clinical diagnosis such as mammography. One drawback of modern LCD displays is the existence of spatial noise expressed as measurable stationary differences in the behavior of individual pixels. This type of noise can be described as a random stationary image superposed on top of the medical image being displayed. It is obvious that this noise image can make subtle structures invisible or add nonexistent patterns to the medical image. In the first case, subtle abnormalities in the medical image could remain undetected, whereas in the second case, it could result into a false positive. This paper describes a method to characterize the spatial noise present in high-resolution medical displays and a technique to solve the problem. A medical display with built-in compensation for the spatial noise at pixel level was developed and improved image quality is demonstrated.

Algorithms↗