Comparison of liquid crystal versus cathode ray tube display for the detection of simulated chest lesions

Research Progress on Flexible Oxide-Based Thin Film Transistors

Oxide semiconductors have drawn much attention in recent years due to their outstanding electrical performance, such as relatively high carrier mobility, good uniformity, low process temperature, optical transparency, low cost and especially flexibility. Flexible oxide-based thin film transistors (TFTs) are one of the hottest research topics for next-generation displays, radiofrequency identification (RFID) tags, sensors, and integrated circuits in the wearable field. The carrier transport mechanism of oxide semiconductor materials and typical device configurations of TFTs are firstly described in this invited review. Then, we describe the research progress on flexible oxide-based TFTs, including representative TFTs fabricated on different kinds of flexible substrates, the mechanical stress effect on TFTs and optimized methods to reduce this effect. Finally, an outlook for the future development of oxide-based TFTs is given.

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

OBJECTIVE

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.

METHODS

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).

RESULTS

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.

CONCLUSION

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.

Detection of cervical spine fracture on computed radiography images a monitor resolution study

RATIONALE AND OBJECTIVES

The purpose of this study was to evaluate the diagnostic accuracy of radiologists using monochrome medical-grade 5 megapixel (MP), 3 MP, 2 MP, and 1 MP displays for the detection of cervical fractures on cervical radiographs, while controlling factors such as luminance and ambient conditions.

MATERIALS AND METHODS

Institutional review board approval was obtained. Two hundred lateral cervical computed radiography images, 97 with fractures, were randomly displayed on 5-MP, 3-MP, 2-MP, or 1-MP liquid crystal displays (LCDs) for a total of 450 interpretations per display. These radiographs were presented in eight sessions, each with 25 radiographs, to nine readers. The reference standard for all cases was computed tomography. Ambient lighting, monitor luminance, and gamma were controlled throughout the study. Measures included receiver operator characteristic areas under the curve (AUC), sensitivity, specificity, and accuracy, mean elapsed time by display, and mean confidence level by display. One way analysis of variance was performed. Results were considered to be significant at an alpha level of 0.05.

RESULTS

AUCs were 0.76 (95% CI, 0.72-0.80) for the 1 MP, 0.80 (95% CI, 0.76-0.84) for the 2 MP, 0.77 (95% CI, 0.73-0.81) for the 3 MP, and 0.76 (95% CI, 0.72-0.80) for the 5 MP medical grade LCDs. There was no significant difference in the AUCs (P values between .0651 and .8693), confidence (P = .158), or interpretation times (P = .751).

CONCLUSION

When controlling factors such as luminance and ambient light, a difference in accuracy in the detection of cervical fractures by resolution could not be detected when using medical-grade displays. Interpretation time and confidence were also not affected by resolution.

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.

Soft-copy display and reading: what the radiologist should know in the digital era

The basic scheme of modern medical imaging consists of the following steps: (1) data acquisition, (2) data (image) processing, (3) further data processing by the computer graphic system, (4) image display, and finally (5) visual perception and interpretation. Medical monitors represent a forgotten part of the whole chain. The purpose of this review is to present the key facts about the display technologies used today, as well as their characterization and quality assurance.

Comparison of observer performance on soft-copy reading of digital chest radiographs: High resolution liquid-crystal display monitors versus cathode-ray tube monitors

The purpose of this study is to compare observer performance for detection of abnormalities on chest radiographs with 5-megapixel resolution liquid-crystal displays (LCD) and 5-megapixel resolution cathode-ray tube (CRT) monitors under bright and subdued ambient light conditions. Six radiologists reviewed a total of 254 digital chest radiographs under four different conditions with a combination of two types of monitors (a 5-megapixel resolution LCD and a 5-megapixel resolution CRT monitor) and with two types of ambient light (460 and 50 lux). The abnormalities analyzed were nodules, pneumothorax and interstitial lung disease. For each reader, the detection performance using 5-megapixel LCD and 5-megapixel CRT monitors under bright and subdued ambient light conditions were compared using multi-case and multi-modality ROC analysis. For each type of ambient light, the average detection performance with the two types of monitors was also compared. For each reader, the observer performance of 5-megapixel LCD and 5-megapixel CRT monitors, under both bright and subdued ambient light conditions, showed no significant statistical differences for detecting nodules, pneumothorax and interstitial lung disease. In addition, there was no significant statistical difference in the average performance when the two monitor displays, under both bright and subdued ambient light conditions, were compared.

Influence of display quality on radiologists' performance in the detection of lung nodules on radiographs

The purpose of this study was to evaluate the influence of display quality on radiologists' performance in the detection of lung nodules. Display systems with various technical properties were considered based on their general availability in a radiology department. Their quality was assessed by physical tests. Multireader-multicase receiver operating characteristic (ROC) analysis was used to evaluate observer performance. The area under the curve (Az) was used as a metric for detectability of simulated lung nodules with diameters of 5 mm and 10 mm, and peak contrast values ranging from 0.1 (subtle) to 0.4 (evident) that were digitally superimposed on normal chest radiographs. Three experienced radiologists interpreted a batch of 60 radiographs on five different display systems; four monitors (two liquid crystal display (LCD) and two cathode ray tube (CRT) monitors) and one printed hardcopy. The physical tests showed superior performance of the two LCD monitors. ROC analysis resulted in the following Az scores: LCD-5MP Az = 0.78, hardcopy Az = 0.77, LCDc-2MP Az = 0.75, CRT-5MP Az = 0.72 and CRTc-1MP Az = 0.71. Difference in Az scores between the LCD-5MP monitor and both the CRT-5MP (p = 0.04) and CRTc-1MP (p = 0.01) monitors was significant. The primary class CRT-5MP monitor that showed reduced observer performance failed to comply with physical acceptance requirements. Luminance response was particularly observed to be insufficient. The results indicate that a quality assurance program has the potential to detect non-optimised display systems that could otherwise result in reduced observer performance.

Recent Advances in Chest Radiography

There have been many remarkable advances in conventional thoracic imaging over the past decade. Perhaps the most remarkable is the rapid conversion from film-based to digital radiographic systems. Computed radiography is now the preferred imaging modality for bedside chest imaging. Direct radiography is rapidly replacing film-based chest units for in-department posteroanterior and lateral examinations. An exciting aspect of the conversion to digital radiography is the ability to enhance the diagnostic capabilities and influence of chest radiography. Opportunities for direct computer-aided detection of various lesions may enhance the radiologist's accuracy and improve efficiency. Newer techniques such as dual-energy and temporal subtraction radiography show promise for improved detection of subtle and often obscured or overlooked lung lesions. Digital tomosynthesis is a particularly promising technique that allows reconstruction of multisection images from a short acquisition at very low patient dose. Preliminary data suggest that, compared with conventional radiography, tomosynthesis may also improve detection of subtle lung lesions. The ultimate influence of these new technologies will, of course, depend on the outcome of rigorous scientific validation.

Detection of masses and microcalcifications of breast cancer on digital mammograms: comparison among hard-copy film, 3-megapixel liquid crystal display (LCD) monitors and 5-megapixel LCD monitors: an observer performance study

The purpose of the study was to compare observer performance in the detection of masses and microcalcifications of breast cancer among hard-copy reading and soft-copy readings using 3-megapixel (3M) and 5-megapixel (5M) liquid crystal display (LCD) monitors. For the microcalcification detection test, we prepared 100 mammograms: 40 surgically verified cancer cases and 60 normal cases. For the mass detection test, we prepared 100 mammograms: 50 cancer cases and 50 normal cases. After six readers assessed both microcalcifications and masses set for each modality, receiver operating characteristic (ROC) analysis was performed. The average A(z)s for mass detection using a hard copy and 3M and 5M LCD monitors were 0.923, 0.927 and 0.920, respectively; there were no significant differences. The average A(z) for microcalcification detection using hard copy, 3M and 5M LCD monitors was 0.977, 0.954 and 0.972, respectively. There were no significant differences, but the P-values between the hard copy and 3M LCD monitor and that between the 3M and 5M LCD monitor were 0.08 and 0.09, respectively. In conclusion, the observer performances for detecting masses of breast cancers were comparable among the hard copy and two LCD monitors; however, soft-copy reading with a 3M LCD monitor showed slightly lower observer performance for detecting microcalcifications of breast cancers than hard-copy or 5M LCD monitor reading.

Comparison of LCD and CRT displays based on efficacy for digital mammography

RATIONALE AND OBJECTIVES

To compare two display technologies, cathode ray tube (CRT) and liquid crystal display (LCD), in terms of diagnostic accuracy for several common clinical tasks in digital mammography.

MATERIALS AND METHODS

Simulated masses and microcalcifications were inserted into normal digital mammograms to produce an image set of 400 images. Images were viewed on one CRT and one LCD medical-quality display device by five experienced breast-imaging radiologists who rated the images using a categorical rating paradigm. The observer data were analyzed to determine overall classification accuracy, overall lesion detection accuracy, and accuracy for four specific diagnostic tasks: detection of benign masses, malignant masses, and microcalcifications, and discrimination of benign and malignant masses.

RESULTS

Radiologists had similar overall classification accuracy (LCD: 0.83 +/- 0.01, CRT: 0.82 +/- 0.01) and lesion detection accuracy (LCD: 0.87 +/- 0.01, CRT: 0.85 +/- 0.01) on both displays. The difference in accuracy between LCD and CRT for the detection of benign masses, malignant masses, and microcalcifications, and discrimination of benign and malignant masses was -0.019 +/- 0.009, 0.020 +/- 0.008, 0.012 +/- 0.013, and 0.0094 +/- 0.011, respectively. Overall, the two displays did not exhibit any statistically significant difference (P > .05).

CONCLUSION

This study explored the suitability of two different soft-copy displays for the viewing of mammographic images. It found that LCD and CRT displays offer similar clinical utility for mammographic tasks.

Pulmonary nodule detection with digital projection radiography: an ex-vivo study on increased latitude post-processing

To evaluate increased image latitude post-processing of digital projection radiograms for the detection of pulmonary nodules. 20 porcine lungs were inflated inside a chest phantom, prepared with 280 solid nodules of 4-8 mm in diameter and examined with direct radiography (3.0x2.5 k detector, 125 kVp, 4 mAs). Nodule position and size were documented by CT controls and dissection. Four intact lungs served as negative controls. Image post-processing included standard tone scales and increased latitude with detail contrast enhancement (log-factors 1.0, 1.5 and 2.0). 1280 sub-images (512x512 pixel) were centred on nodules or controls, behind the diaphragm and over free parenchyma, randomized and presented to six readers. Confidence in the decision was recorded with a scale of 0-100%. Sensitivity and specificity for nodules behind the diaphragm were 0.87/0.97 at standard tone scale and 0.92/0.92 with increased latitude (log factor 2.0). The fraction of "not diagnostic" readings was reduced (from 208/1920 to 52/1920). As an indicator of increased detection confidence, the median of the ratings behind the diaphragm approached 100 and 0, respectively, and the inter-quartile width decreased (controls: p<0.001, nodules: p=0.239) at higher image latitude. Above the diaphragm, accuracy and detection confidence remained unchanged. Here, the sensitivity for nodules was 0.94 with a specificity from 0.96 to 0.97 (all p>0.05). Increased latitude post-processing has minimal effects on the overall accuracy, but improves the detection confidence for sub-centimeter nodules in the posterior recesses of the lung.

ROC analysis for diagnostic accuracy of fracture by using different monitors

BACKGROUND

The purpose of this study was to compare diagnostic accuracy by using two types of monitors.

METHODS

Four radiologists with 10 years experience twice interpreted the films of 77 fracture cases by using the ViewSonic P75f+ and BARCO MGD221 monitors, with a time interval of 3 weeks. Each time the radiologists used one type of monitor to interpret the images. The image browser used was the Unisight software provided by Atlastiger Company (Shanghai, China), and interpretation result was analyzed via the LABMRMC software.

RESULTS

In studies of receiver operating characteristics to score the presence or absence of fracture, the results of images interpreted through monochromic monitors showed significant statistical difference compared to those interpreted using the color monitors.

CONCLUSION

A significant difference was observed in the results obtained by using two kinds of monitors. Color monitors cannot serve as substitutes for monochromatic monitors in the process of interpreting computed radiography (CR) images with fractures.

Image quality performance of liquid crystal display systems: influence of display resolution, magnification and window settings on contrast-detail detection

The aim of this study was to investigate the combined effects of liquid crystal display (LCD) resolution, image magnification and window/level adjustment on the low-contrast performance in soft-copy image interpretation in digital radiography and digital mammography. In addition, the effect of a new LCD noise reduction mechanism on the low-contrast detectability was studied. Digital radiographs and mammograms of two dedicated contrast-detail phantoms (CDRAD 2.0 and CDMAM 3.4) were scored on five LCD devices with varying resolutions (1-3- and 5-megapixel) and one dedicated 5-megapixel cathode ray tube monitor. Two 5-megapixel LCDs were included. The first one was a standard 5-megapixel LCD and the second had a new (Per Pixel Uniformity) noise reduction mechanism. A multi-variate analysis of variance revealed a significant influence of LCD resolution, image magnification and window/level adjustment on the image quality performance assessed with both the CDRAD 2.0 and the CDMAM 3.4 phantoms. The interactive adjustment of brightness and contrast of digital images did not affect the reading time, whereas magnification to full resolution resulted in a significantly slower soft-copy interpretation. For digital radiography applications, a 3-megapixel LCD is comparable with a 5-megapixel CRT monitor in terms of low-contrast performance as well as in reading time. The use of a 2-megapixel LCD is only warranted when radiographs are analysed in full resolution and when using the interactive window/level adjustment. In digital mammography, a 5-megapixel monitor should be the first choice. In addition, the new PPU noise reduction system in the 5-megapixel LCD devices provides significantly better results for mammography reading as compared to a standard 5-magapixel LCD or CRT. If a 3-megapixel LCD is used in mammography setting, a very time-consuming magnification of the digital mammograms would be necessary.