Monochrome Liquid Crystal Displays Research Articles

Assessment Tool of Image Quality for Medical Liquid-crystal Displays Using Commercially Available Digital Cameras

We developed a simplified tool for measuring image quality of medical liquid-crystal displays (LCDs) using a commercially available color digital camera. This tool implemented as a plug-in software for ImageJ (open-source image processing program) was designed to compute modulation transfer functions (MTFs) and Wiener spectra (WS) of monochrome and color LCDs from LCD photographed images captured by a camera. The intensities of the red (R), green (G), and blue (B) signals of the unprocessed image data depend on the spectral sensitivity of the image sensor used in the camera. In order to evaluate image quality based on LCD luminance, the plug-in software calibrates the RGB signals from the camera using measured luminance of the LCD and converts them into grayscale signals that correspond to the luminance of the LCD. The MTFs and WS are determined based on the line response from a one-pixel line image and the one-dimensional noise profiles acquired by scanning the uniform image using numerically synthesized slit, respectively. With this plug-in software for ImageJ, we are able to readily compute MTFs and WS of both monochrome and color LCDs from unprocessed image data of cameras. Our simplified tool is helpful to evaluate and understand the physical performance of LCDs for a large number of display users in hospitals and medical centers.

A method for evaluating image quality of monochrome and color displays based on luminance by use of a commercially available color digital camera.

The aim of this study is to propose a method for the quantitative evaluation of image quality of both monochrome and color liquid-crystal displays (LCDs) using a commercially available color digital camera. The intensities of the unprocessed red (R), green (G), and blue (B) signals of a camera vary depending on the spectral sensitivity of the image sensor used in the camera. For consistent evaluation of image quality for both monochrome and color LCDs, the unprocessed RGB signals of the camera were converted into gray scale signals that corresponded to the luminance of the LCD. Gray scale signals for the monochrome LCD were evaluated by using only the green channel signals of the camera. For the color LCD, the RGB signals of the camera were converted into gray scale signals by employing weighting factors (WFs) for each RGB channel. A line image displayed on the color LCD was simulated on the monochrome LCD by using a software application for subpixel driving in order to verify the WF-based conversion method. Furthermore, the results obtained by different types of commercially available color cameras and a photometric camera were compared to examine the consistency of the authors' method. Finally, image quality for both the monochrome and color LCDs was assessed by measuring modulation transfer functions (MTFs) and Wiener spectra (WS). The authors' results demonstrated that the proposed method for calibrating the spectral sensitivity of the camera resulted in a consistent and reliable evaluation of the luminance of monochrome and color LCDs. The MTFs and WS showed different characteristics for the two LCD types owing to difference in the subpixel structure. The MTF in the vertical direction of the color LCD was superior to that of the monochrome LCD, although the WS in the vertical direction of the color LCD was inferior to that of the monochrome LCD as a result of luminance fluctuations in RGB subpixels. The authors' method based on the use of a commercially available color camera is useful to evaluate and understand the display performances of both monochrome and color LCDs in radiology departments.

Chromaticity and correlated color temperature of the white point in medical liquid–crystal display

The color characteristics of medical liquid-crystal displays (LCDs) have become one of the main interests in quality assurance and quality control of medical display devices. It is necessary to evaluate variations of the color characteristics in medical LCDs in order to provide consistent color characteristics for image reading. In this study, we characterize the color characteristics in grayscale images displayed on medical LCDs. Eight medical color LCDs and eight medical monochrome LCDs were used in this study with operating times ranging from 800 to 25 000 h. Default settings of correlated color temperature (CCT) of white points for all color LCDs were set at 7500 K. We measured chromaticity in the Commission Internationale de l'Éclairage (CIE) u'v' color space and CCT of the white point at 18 luminance levels. A colorimeter and grayscale test patterns with various luminance levels were used for the measurements. First, we examined differences in chromaticity and CCT at 18 luminance levels for each LCD. Second, we compared chromaticities of the different LCDs. Then, chromaticity and CCT of LCDs were measured at different ambient light conditions (30 and 560 lux) and compared to those measured in a dark room. Finally, the relationship between operating times and CCT was evaluated. The chromaticities of monochrome LCDs changed toward the blue and CCT increased as luminance decreased. In color LCDs, the chromaticity and CCT of the white point except at the minimum luminance were nearly constant to those measured at the maximum luminance. We observed differences in chromaticity between color and monochrome LCDs because of the nonadjustable white point of monochrome LCDs. When the ambient light increased, chromaticity varied, and CCT decreased on every LCD. Ambient light had a much greater impact on chromaticity and CCT at lower luminance levels. The CCT of LCDs decreased in longer operating times. The grayscale of LCDs with longer operating times was measured to be more yellowish due to the degradation of cold cathode fluorescent lamps. Our results clearly indicate that the white point in grayscale images displayed on medical LCDs changes depending on luminance levels, color or monochrome LCDs, ambient light conditions, and operating times. These data provide useful information to understand color characteristics of LCD for image reading, especially for quality assurance and quality control of LCDs.

Effect of greyscale liquid crystal displays of different resolutions on observer performance during detection of small solitary pulmonary nodules

The aim of this study was to evaluate the effect of monochrome liquid crystal displays (LCDs) with different resolutions on observer performance during detection of small solitary pulmonary nodules. Chest images of digital radiography were selected online from the hospital's picture archiving and communication system. Of the 164 images selected, small solitary non-calcified pulmonary nodules were present in 63 images and absent in 101 images. Observer performance was assessed among 3 extremely experienced, 3 very experienced and 3 moderately experienced radiologists, who independently interpreted these images on 2, 3 and 5 megapixel greyscale LCDs. A five-point confidence level rating scale was used to represent the presence of nodules: definite absence, probable absence, indetermination, probable presence and definite presence. The observers were requested to rank each image on the given display according to the presence of the pulmonary nodule. Observer performance was analysed in terms of receiver operating characteristics (ROCs). The areas under the ROC curves which represented the observer performance for the 2, 3 and 5 megapixel LCDs were found to be 0.705, 0.722 and 0.764, respectively, for the extremely experienced radiologists; 0.687, 0.712 and 0.721, respectively, for the very experienced radiologists; and 0.689, 0.696 and 0.711, respectively, for the moderately experienced radiologists. These differences were not statistically significant. The observer performances for detection of small solitary non-calcified pulmonary nodules by radiologists with varying degrees of experience were comparable between the 2, 3 and 5 megapixel monochrome LCDs.

SU‐E‐I‐43: Verification of the Usefulness of Evaluation Method for Angular Performance with the ANG Test Pattern

Purpose: A simple method with the ANG test pattern to evaluate the angular performance of medical‐grade liquid‐crystal display (LCD) monitors was proposed by the International Electrotechnical Commission (IEC) in December 2009 (IEC 62563‐1). The purpose of this study was to investigate correlation between the results obtained by using the ANG test pattern and the angular performance measured by a luminance meter. We also examined the effect of ambient‐light conditions on the results evaluated by using the ANG test pattern. Methods: Three LCDs, a medical‐grade monochrome LCD (Radiforce GS220, 500 cd/m2, Eizo Nanao), a medical‐grade color LCD (Radiforce RX211, 300 cd/m2, Eizo Nanao), and a general‐purpose LCD (SyncMaster940B, 180 cd/m2, Samsung) were used in this study. The ANG test pattern was observed by eight observers under three ambient‐light conditions (0, 35, and 327 lux). Two different scoring methods were used. One is the method proposed by the IEC 62563‐1, and the other is the method modified for comparison of results measured by a luminance meter. The luminance performance was measured as a function of viewing angle, and evaluated as the relative contrast ratio. Finally, the results in terms of the modified scores were compared to the luminance performance in various viewing angles. Results: Variations of the modified scores and the relative contrast ratio as a function of viewing angle indicated a similar tendency for medical‐grade LCDs. On the other hand, the two results did not correspond well for the general‐purpose LCD. The difference between the results obtained at 0 and 327 lux was 0.11 at a maximum for all LCDs used in this study. Conclusions: The evaluation method with the ANG test pattern is considered to be useful for evaluation of the angular performance for medical‐grade LCDs taking ambient‐light conditions into consideration.

SU‐E‐I‐44: Investigation of the Contrast Ratio Required for Medical‐Grade Liquid‐Crystal Displays

Purpose: Liquid‐crystal displays (LCDs) with a higher contrast ratio (CR) have been recently developed. However, only a few studies have been reported regarding the CR of the LCDs required for displaying medical images. The purpose of this study was to investigate the CR of LCDs required for displaying medical images.Methods: A two‐megapixel monochrome LCD (GS220, maximum 1,000 cd/m2, recommended 500 cd/m2, Eizo Nanao, Japan) was used in this study. This LCD was calibrated to the grayscale standard display function (GSDF) with different maximum‐luminance settings such as 250, 500, and 700 cd/m2 for mammograms and 175, 500, and 700 cd/m2 for chest radiographs. The minimum luminance of the LCD was kept at 0.7 cd/m2 for each calibration. The CR was calculated from the maximum and minimum luminance of each luminance setting. Mammograms (40 images) and chest radiographs (10 images) were selected as research subjects. To examine the maximum luminance (Lmax) and the minimum luminance (Lmin) in each image, region of interests (ROIs) were set based on the histogram analysis. Then, luminance corresponding to ROIs was calculated by using the GSDF curve with different maximum luminance settings. Finally, luminance ratio (LRimg) in mammograms and chest radiographs were obtained from the Lmax and Lmin in each image.Results: The average LRimg of mammograms with the maximum‐luminance setting of 250, 500, and 700 cd/m2 was 209:1, 388:1, and 523:1, respectively. On the other hand, the average LRimg of chest radiographs with the maximum‐luminance settings of 175, 500, and 700 cd/m2 was 37:1, 70:1, and 86:1, respectively Conclusions: We found that the CR of the LCD required for displaying mammograms and chest radiographs ranged from 209:1 to 523:1 and 37:1 to 86:1, respectively. A significant difference in the CR of LCD required for displaying medical image was observed between mammograms and chest radiographs.

SU‐E‐I‐42: Variations of the Chromaticity in Gray‐Scale Images Displayed on Different Liquid‐Crystal Display Monitors

Purpose: Purpose in this study was to investigate variations of the chromaticity in gray‐scale images displayed on different liquid‐crystal display (LCD) monitors at different illuminance. Method and Materials:Four color LCD monitors (RX210, 240 cd/m2, two‐megapixel, Eizo Nanao), and four monochrome LCD monitors (G31, 450 cd/m2, three‐megapixel, Eizo Nanao) were used in this study. These LCDs have various operating hours ranging from 4,000 hours to 23,000 hours. The chromaticity in gray‐scale images with 18 different luminance levels was measured by use of the BN test patterns (JESRA X‐0093‐2010) and a chromameter (CS‐200:KONICA MINOLTA). Distances in CIE uˈvˈ color space, delta uˈvˈ, for all possible pairs of LCD monitors were calculated based on AAPM TG‐18 guideline. The chromaticity of the LCDs was measured at different illuminance (0, 30, and 560 lux). Variations of the chromaticity at different illuminance compared to 0 lux were examined using delta uˈvˈ. Results: Delta uˈvˈ for all possible pairs of LCD monitors did not exceed 0.01. Delta uˈvˈ of the monochrome and the color LCDs indicated greater differences than those for different color LCDs or different monochrome LCDs. There was no difference of chromaticity depending on the operating hours. When illuminance increased, the chromaticity varied on every LCD. Although delta uˈvˈ between 0 lux and 560 lux exceeded 0.01 at low‐luminance levels of 30 cd/m2 or less, delta uˈvˈ between 0 and 30 lux did not exceed 0.01. Conclusions: Variations of the chromaticity for all possible pairs of LCD monitors used in this study were less than 0.01. We found that the chromaticity varied on every LCD with increasing illuminance.

Effect of LCD monitor type and observer experience on diagnostic performance in soft-copy interpretations of the maxillary sinus on panoramic radiographs

PurposeThe aim of this study was to evaluate the effect of liquid crystal display (LCD) monitor type and observer experience on the diagnostic performance in soft-copy interpretations of maxillary sinus inflammatory lesions on panoramic radiographs.Materials and MethodsNinety maxillary sinuses on panoramic images were grouped into negative and positive groups according to the presence of inflammatory lesions, using CT for confirmation. Monochrome and color LCDs were used. Six observers participated and ROC analysis was performed to evaluate the diagnostic performance. The reading time, fatigue score, and inter-/intra-observer agreements were assessed.ResultsThe interpretation of maxillary sinus inflammatory lesions was affected by the LCD monitor type used and by the experience of the observer. The reading time was not significantly different, however the fatigue score was significantly different between two LCD monitors. Inter-observer agreement was relatively good in experienced observers, while the intra-observer agreement for all observers was good with monochrome LCD but not with color LCD.ConclusionThe less experienced observers showed lowered diagnostic ability with a general color LCD.

ＲＯＣ解析による患者体動に起因する不鋭の検出能の評価 ―ファントム画像による診断用ＬＣＤと画像プレビュー用ＬＣＤの比較―

To evaluate the detectability of image unsharpness due to a patient's movement, a receiver operating characteristic (ROC) analysis was conducted to compare the diagnostic and preview liquid-crystal displays (LCDs). Phantom images that simulated a patient's movement were obtained by using a moving metronome and acrylic plates with a computed radiography (CR) system. A total of 104 images were classified into five groups according to the degrees of image unsharpness determined based on the metronome velocity and exposure time. In an ROC observer study (n=6), a 2-megapixel diagnostic monochrome LCD (2M-LCD) and a 1.3-megapixel general color LCD for preview (1.3M-LCD) were compared in terms of the detection of image unsharpness due to the movement. A statistical test was performed using the multi-reader multi-case (MRMC) method. In the results, the average areas under the ROC curve values for the detection of image unsharpness using the 2M-LCD and 1.3M-LCD were 0.952 and 0.850, respectively. The detection of image unsharpness using the 2M-LCD was significantly better than that using the 1.3M-LCD (p<0.05). In addition, some images with slight unsharpness were identified correctly only using the 2M-LCD. The results suggest that the low-resolution LCD (i.e., the 1.3M-LCD for preview) had a limitation in identifying image unsharpness due to the patient's movement. Slight unsharpness could be missed in primary image checks performed on a preview monitor equipped with an imaging system. Therefore, the high-resolution LCD (i.e., a 2M-LCD) is necessary when using radiography for diagnostics.

Influence of liquid crystal displays (LCDs) with different resolutions on the detection of pulmonary nodules: An observer performance study

Purpose To evaluate the influence of monochrome LCDs with different resolutions on the detection performance of pulmonary nodules. Materials and methods 187 chest DR images were selected from our hospital's picture archiving and communication system (PACS), including 111 normal cases and 76 cases with solitary pulmonary nodules. Those positive images were divided into two groups, A and B, according to the diameter of nodules. Three high-, three mid-, and three low-experienced radiologists interpreted those images with a 2 megapixel (MP), a 3 MP and a 5 MP monochrome LCD independently. Regarding the presence of the nodule, five-point confidence level rating scale was used: definite absence, probable absence, indetermination, probable presence and definite presence. The observers were requested to rank each image on the given display according to the presence of pulmonary nodule. Receiver operation characteristic (ROC) analysis was used to interpret the data. Results When detecting the pulmonary nodules of Group A on 2 MP-, 3 MP- and 5 MP-LCD, the areas under ROC curves (AUCs) were 0.641, 0.683 and 0.732 for high-experienced radiologists, 0.633, 0.679 and 0.716 for mid-experienced radiologists, 0.620, 0.652 and 0.719 for low-experienced radiologists, respectively; when detecting the pulmonary nodules of Group B, the AUCs were 0.811, 0.830 and 0.842 for high-experienced radiologists, 0.771, 0.821 and 0.837 for mid-experienced radiologists, 0.759, 0.770 and 0.829 for low-experienced radiologists, respectively. However, there were no significant differences among different reading modalities. Conclusion For detecting pulmonary nodules, it is equivalent of observer performance among 2 MP-, 3 MP- and 5 MP-LCD.

Comparison of detectability of a simple object with low contrast displayed on a high-brightness color LCD and a monochrome LCD

The goal of this study was to investigate the effect of the different luminance settings of a high-brightness color liquid-crystal display (LCD) on the detectability of a simple grayscale object with low contrast by use of receiver operating characteristic (ROC) analysis. The detectability of a high-brightness color LCD with two maximum-luminance settings (500 and 170 cd/m(2)) was compared with the detectability of a monochrome LCD (500 cd/m(2)). The two LCDs used in this study were calibrated to the grayscale standard display function. The average areas under the ROC curve (AUCs) and the standard deviations for all thirteen observers for the 500 cd/m(2) color LCD, 500 cd/m(2) monochrome LCD, and 170 cd/m(2) color LCD were 0.937 +/- 0.040, 0.924 +/- 0.056, and 0.915 +/- 0.068, respectively. There were no statistically significant differences in the average AUCs among the three LCD monitor conditions. On the other hand, the total observation time for the 170 cd/m(2) color LCD was significantly shorter than that for the 500 cd/m(2) color and monochrome LCDs (p < 0.05). Irrespective of the maximum luminance settings (500 and 170 cd/m(2)), the color LCD provided a performance comparable to the monochrome LCD for detection of a simple grayscale object with low contrast.

SU-GG-I-48: Evaluation of Viewing Angle Performance on the Latest High-Brightness Color LCD Monitors with the In-Plane Switching Panel for Medical Images

Purpose: Our purpose was to compare the viewing angle performance on high‐brightness color liquid‐crystal display (LCD) monitors to that of monochrome LCD monitors. Method and Materials: We used four LCD monitors with an in‐plane switching (IPS) panel: two high‐brightness color LCD unt il 300 cd/m2, two‐megapixel, Eizo), and RX210, 220, cd/m2, two‐megapixel, Eizo), and two monochrome LCD monitors, (GS220, 500 cd/m2, two‐megapixel, Eizo, and G31‐S, 450 cd/m2, three‐megapixel, Eizo). The luminance performance of each LCD monitor was measured as a function of the viewing angle (−60° to +60°) in the horizontal, the vertical, and the diagonal directions by use of a telescopic‐type luminance meter without any ambient lighting. The viewing angle performance was evaluated with a relative contrast ratio of 70 % or greater. Results: The range of viewing angle in terms of relative contrast ratio on the 300 cd/m2 high‐brightness color, the 240 cd/m2 high‐brightness color, the 500 cd/m2 two‐megapixel monochrome, and the 450 cd/m2 three‐megapixel monochrome LCD monitors with similar IPS panels were 34° to 74°, 29° to 48°, 55° to 81°, and 39° to 74°, respectively. The relative contrast ratios showed notable variations for different viewing angles in spite of similar types of panels. Our results indicate that the viewing angle performance on the 240 cd/m2 color LCD monitor tended to provide a slightly inferior angular performance to the two monochrome LCD monitors used in this study. On the other hand, the 300 cd/m2 color LCD monitor had a comparable viewing angle performance with the 450 cd/m2 monochrome LCD monitor. Conclusion: The viewing angle performance on the high‐brightness color LCD monitors is inferior to that of monochrome LCD monitors. However the 300 cd/m2 color LCD monitor had comparable viewing angle performance with the 450 cd/m2 monochrome LCD monitor.

医用液晶ディスプレイを用いたＸ線画像観察による眼の疲労度の客観的な評価

The aim of this study was to evaluate visual fatigue objectively by measuring accommodation time and critical fusion frequency (CFF) before and after reading posteroanterior chest radiographs displayed on medical-grade liquid-crystal displays (LCDs) under different monitor conditions. A color LCD (500, 170 cd/m²) and a monochrome LCD (500 cd/m²) were used in this study. Six observers independently kept reading the radiographs for two hours to understand various lung nodules in the "Fatigue Session". Objective visual fatigue was measured by using the accommodation device and the CFF meter before and after the Fatigue Session. The ambient lighting of the laboratory was set at 35 lux. Both the accommodation time and the CFF between before and after the Fatigue Session indicated statistically significant differences (p<0.05). Our results on accommodation time and CFF before and after reading the radiographs on medical-grade LCDs indicated that visual fatigue could be evaluated objectively.

正規化順位法による解像度や表示色が異なる医用画像表示用液晶ディスプレイの評価

The purposes of this study were to evaluate the image quality of five types of liquid-crystal display (LCD) monitors by utilizing the normalized-rank approach and to investigate the effect of LCD monitor specifications, such as display colors, luminance, and resolution, on the evaluators' ranking. The LCD monitors used in this study were 2, 3 and 5 mega-pixel monochrome LCD monitors, and 2 and 3 mega-pixel color LCD monitors (Eizo Nanao Corporation). All LCD monitors were calibrated to the grayscale standard display function (GSDF) with different maximum luminance (recommended luminance) settings. Also, four kinds of radiographs were used for observer study based on the normalized-rank approach: three adult chest radiographs, three pediatric chest radiographs, three ankle joint radiographs, and four double-contrasted upper gastrointestinal radiographs. Ten radiological technologists participated in the observer study. Monochrome LCD monitors exhibited superior ranking with statistically significant differences (p<0.05) compared to color LCD monitors in all kinds of radiographs. The major difference between monochrome and color monitors was luminance. Therefore, it is considered that the luminance of LCD monitors affects observers' evaluations based on image quality. Moreover, in the case of radiographs that include high frequency image components, the monitor resolution also affects the evaluation. In clinical practice, it is necessary to optimize the luminance and choose appropriate LCD monitors for diagnostic images.

MO‐FF‐A4‐05: Comparison of Detectability of a Simple Object with Low Contrast Displayed On a High‐Brightness Color LCD Monitor and a Monochrome LCD Monitor

Purpose: To examine the potential usefulness of a high‐brightness color liquid crystal display (LCD) monitor, the detectability of the color monitor was compared with the detectability of a monochrome LCD monitor by using receiver operating characteristic (ROC) analysis. Materials and Method: Two LCD monitors were used in this study: a two‐megapixel high‐brightness color monitor (RX‐211, 750 cd/m2 (maximum), Nanao, Japan), and a two‐megapixel monochrome monitor (GS‐220, 1,000 cd/m2 (maximum), Nanao, Japan). Both monitors were calibrated to grayscale standard display function. We examined the detectability of a color LCD monitor with different luminance settings (500 and 170 cd/m2) and a monochrome LCD monitor (500 cd/m2). Totally, 40 images were taken — including 20 images with a ball (8 mm in diameter), which was used as a signal and put on the surface of a 15.5 cm acrylic plate. All images were acquired by use of a computed radiographic system (CR9000, Fuji Film, Japan). All images were displayed on the LCD monitors with 8‐bit gray scale without any ambient lighting. Finally, the confidence data obtained by thirteen observers were analyzed by use of software (DBM MRMC, The University of Chicago) for ROC analysis, and the statistically significant differences between the areas under the ROC curve (AUC) were determined with the jackknife method. Results: The AUCs of color the LCD monitor with a maximum luminance of 500 cd/m2, 170 cd/m2 and monochrome LCD monitor with a maximum luminance of 500 cd/m2 were 0.937, 0.924, and 0.915, respectively. There were no statistically significant differences between the monochrome LCD monitor and the color LCD monitor with different luminance settings. Conclusion: The detectability of a high‐brightness color LCD monitor indicated comparable performances obtained with a monochrome LCD monitor.

A New Resolution Enhancement Technology Using the Independent Sub-Pixel Driving for the Medical Liquid Crystal Displays

A new resolution enhancement technology using the independent sub-pixel driving technology was developed for the medical monochrome liquid crystal displays (LCDs). Each pixel of monochrome LCDs, which employ the color liquid crystal panels that its color filters are removed, consists of three sub-pixels. In the new LCD system implemented with this new technology, the sub-pixel intensities were modulated according to the detailed image information, and consequently resolution was enhanced three times. Thus the new technology realized a 15 mega-pixels (MP) super high-resolution LCD (SHR-LCD) out of a conventional 5 MP LCD and a 9 MP SHR-LCD out of a conventional 3 MP LCD. Physical measurements and perceptual evaluations performed in this study proved that the achieved 15 MP (through our new technology) was appropriate and efficient to depict the finer anatomical structures such as the micro calcifications in mammography.

Analysis method of noise power spectrum for medical monochrome liquid crystal displays

We investigated methods of analyzing the noise power spectrum (NPS) measurement for medical liquid crystal displays (LCDs). Uniform images displayed on the LCDs were imaged with a high-performance digital camera equipped with a close-up lens, and then the NPSs were calculated from the image data by means of several analysis methods. In a method using the 2D fast Fourier transform (FFT) with a 256 x 256 pixels data segment (basic method), we examined the efficacy of a background trend correction (BTC) and a Hanning windowing process used for reducing the spectral estimation errors in the Fourier analysis. To improve the frequency resolution of the basic method, we examined two 2D FFT methods by using 512 x 512 and 1024 x 1024 pixel segments. In addition, we studied a 1D FFT method with 1024-point 1D noise profiles (1D method). In these three methods, the BTC by a second-order polynomial fit and Hanning windowing were commonly applied. A 3-mega-pixel (MP) and a 5-MP monochrome LCD were employed for evaluating the respective methods. Also, a prototype 5-MP LCD equipped with a new anti-reflection surface-coated panel was compared with the conventional 5-MP LCD. The Hanning windowing process was indispensable for avoiding the spectral leakage errors caused by the pixel structures of the LCD. Sufficient frequency resolution was obtained by the 2D FFT method with the 1024 x 1024 pixels segments and the 1D method. The method which provided the most reliable NPSs was the 1D method, with which the BTC was achieved successfully.

High-resolution monochrome liquid crystal display versus efficient household colour liquid crystal display: comparison of their diagnostic performance with unenhanced CT images in focal liver lesions

This study compared the ability of an efficient household liquid crystal display (LCD) and a medical high-resolution LCD to detect small hepatic lesions on unenhanced computed tomography (CT) images. We obtained the images from 100 subjects who had undergone abdominal CT. They consisted of 41 patients with a single space-occupying lesion (SOL) in the liver and 59 control subjects with no SOL. Independently, five radiologists rated their confidence concerning the presence of hepatic SOLs on a continuous scale from 0 to 1. Receiver-operating characteristic (ROC) analysis was performed using the jackknife method using the program LABMRMC. We evaluated the differences in A(z) based on the 95% confidence intervals. The mean A(z) of the five observers was 0.9594 with the efficient household LCD vs. 0.9335 with the medical high-resolution LCD. The difference was -0.0422, and the 95% confidence interval was -0.1101 to 0.0257 (p=0.2203). There was no significant difference in the A(z) value between the two types of LCDs. The diagnostic performance with the household LCD was comparable to that with the high-resolution LCD, implying that the former type of LCD can be used to diagnose CT images.

A comparative contrast‐detail study of five medical displaysa)

The objective of this study was to compare the contrast-detail performance of five different commercial liquid crystal displays (LCDs) to other LCD and cathode-ray tube (CRT) displays for medical applications. A contrast-detail phantom, supplemented with 5 in. of acrylic, was imaged on a commercial digital radiographic system using techniques comparable to chest radiography. The phantom design enabled observer evaluation by a four-alternative forced choice paradigm. The acquired images were independently scored by five observers on five medical display devices: a 5 megapixel monochrome LCD, a 3 megapixel monochrome LCD, a 9 megapixel color LCD, a 5 megapixel monochrome CRT, and a mammographic-grade monochrome CRT. The data were analyzed using the method suggested by the manufacturer based on a nearest neighbor correction technique. They were further analyzed using a logistic regression response model with a natural threshold using an overall chi-square test for display type followed by pairwise comparisons for individual display performance. The differences between the display devices were small. The standard analysis of the results based on the manufacturer-recommended method did not yield any statistically discernible trend among displays. The logistic regression analysis, however, indicated that the 5 megapixel monochrome LCD was statistically significantly (p <0.0001) superior to the others, followed by the 3 megapixel monochrome LCD (p<0.0001). The three other displays exhibited lower but generally similar performance characteristics. The findings suggest that 5 and 3 megapixel monochrome LCDs provide comparable but subtly superior contrast detectability than other tested displays, with the former performing slightly better in the detection of subtle and fine details.

Viewing angle performance of medical liquid crystal displays

Cathode-ray tube (CRT) and liquid crystal display (LCD) are currently two main technologies for displaying medical images. LCDs possess a number of advantages, but their performance varies as a function of viewing angle. Our purpose in this study was to characterize the angular response performance of five medical-grade LCDs, and to substantiate their impact on their compliance with the DICOM gray scale display function (GSDF). Furthermore, the study aimed to test a framework to define an angular acceptance range for medical LCDs based on the recent AAPM TG18 guidelines. Measurements were made on five calibrated dual-domain LCDs, including two 3 megapixel monochrome LCDs, two 5 megapixel monochrome LCDs, and one 9 megapixel color LCD. The luminance performance of each display device was measured as a function of the viewing angle at 17 discrete levels using TG18-LN test patterns and a Fourier-optics-based luminance meter. The luminance data were analyzed according to the AAPM TG18 methodology. The displays showed notable variation in luminance and contrast performance as a function of the viewing angle, particularly in diagonal viewing orientations. Overall, the luminance ratio remained greater than 175 within +/-20 degrees and +/-33 degrees viewing angle cones (beta175 = 20 degrees-33 degrees). Aiming to maintain a maximum deviation from the GSDF contrast less than 0.3, i.e., kappa17 < or = 0.3, acceptable viewing angle cones of +/-22 degrees and +/-35 degrees were indicated (alpha 0.3= 22 degrees-35 degrees). The findings demonstrate the significant impact of angular response on image contrast, and the utility of alpha 0.3 and beta175 quantities for defining the viewing angle cones within which a medical LCD device can be effectively utilized.