Personal computer versus workstation display: observer performance in detection of wrist fractures on digital radiographs

PURPOSE: To retrospectively compare the accuracy of observer performance with personal computer (PC) compared with that with dedicated picture archiving and communication system (PACS) workstation display in the detection of wrist fractures on computed radiographs. MATERIALS AND METHODS: This study was conducted according to the principles of the Declaration of Helsinki (2002 version) of the World Medical Association. The institutional clinical board approved the study; informed consent was not required. Seven observers independently assessed randomized anonymous digital radiographs of the wrist from 259 subjects; 146 had fractures, and 113 were healthy control subjects (151 male and 108 female subjects; average age, 33 years). Follow-up radiographs and/or computed tomographic scans were used as the reference standard for patients with fractures, and follow-up radiographs and/or clinical history data were used as the reference standard for controls. The PC was a standard hospital machine with a 17-inch (43-cm) color monitor with which Web browser display software was used. The PACS workstation had two portrait 21-inch (53-cm) monochrome monitors that displayed 2300 lines. The observers assigned scores to the radiographs on a scale of 1 (no fracture) to 5 (definite fracture). Receiver operating characteristic (ROC) curves, sensitivity, specificity, and accuracy were compared. RESULTS: The areas under the ROC curves were almost identical for the PC and workstation (0.910 vs 0.918, respectively; difference, 0.008; 95% confidence interval: -0.029, 0.013). The average sensitivity with the PC was almost identical to that with the workstation (85% vs 84%, respectively), as was the average specificity (82% vs 81%, respectively). The average accuracy (83%) was the same for both. CONCLUSION: The results of this study showed that there was no difference in accuracy of observer performance for detection of wrist fractures with a PC compared with that with a PACS workstation.     

Influence of the digital image display monitor on observer performance.

OBJECTIVE: To assess the influence of the display monitor on observer performance. MATERIAL AND METHODS: Artificial enamel lesions were created in 40 extracted teeth at random using 1/4 and 1/2 round burs. Teeth were mounted in dental stone blocks to simulate a hemidentition. Approximate exposures were recorded at 70 kVp using a Digota (Soredex, Orion Corp, Helsinki, Finland) digital imaging system, calibrated to achieve optimum density. Six dentists rated each image on a five-point scale for the presence or absence of a lesion. Radiographic images were viewed on the following monitors: (1) AlphaScan 711 (Sampo Corp.); (2) Multiscan 17 Se II (Sony Electronics Inc.); (3) DS 2000 (Clinton Electronics Corp.) and (4) Latitude CP Laptop (Dell Computer Corp.). Raters were allowed to magnify and to adjust density and contrast of each image at will. Receiver Operating Characteristic (ROC) analysis was performed and curves were plotted for each image. Data was subjected to repeated measures analysis of variance and ordinal logistic regression to test for significance between variables and to determine odds ratios. RESULTS: Mean ROC curve areas ranged from 0.8728 for the Sampo monitor to 0.8395 for the Sony. Repeated measures analysis of variance showed significant differences between observers (P < 0.0001), lesion size (P < 0.0001), examiner/monitor interaction (P < 0.033) and examiner/block interaction (P < 0.013). However, no significant difference was found between monitors. CONCLUSION: This study suggests that observer performance is independent of the visual characteristics of the display monitor.     

Radiology in suspected non-accidental injury: theory and practice in The Netherlands

Introduction

This study evaluates radiological imaging in suspected non accidental injury (NAI) in children below the age of 2 years in the Netherlands.

Material and methods

The study consisted of two parts; first an on-line questionnaire on suspected NAI, amongst radiological practices within the Netherlands. The second part of the study was a retrospective analysis of skeletal surveys in children under the age of 2 years, which were reviewed in an expert centre of forensic medicine on request of the public prosecutor.

Results

Out of 116 hospitals 45 (39%) radiologists completed the on-line questionnaire; 8 (8%) of the proposed skeletal surveys complied with the ACR criteria. A total of 29 skeletal surveys in 26 children were reviewed. The median age at the time of the radiographic exam was 3 months for both boys and girls. Only 2 (7%) studies complied with the ACR criteria.

Discussion

The results of our study show that, in theory as well as in practice, Dutch radiological practices show a large variation in imaging protocols for suspected NAI.     

胸片中肺癌的计算机辅助检测(CAD):对阅片者绩效的影响

目的评价在胸片发现的早期肺癌中,计算机辅助检测(CAD)是如何影响阅片者的绩效。材料与方法经伦理委员会批准,本回顾性研究包括46例CT发现并经组织学证实     

The effect of image display size on observer performance an assessment of variance components

RATIONALE AND OBJECTIVE: Our goal was to investigate the effect of the displayed image size on variance components during the performance of an observer performance study to detect masses on abdominal computed tomography (CT) examinations. MATERIALS AND METHODS: A previously performed receiver operating characteristic (ROC) study with eight observers to detect abdominal masses on 166 CT examinations was reanalyzed to assess variance components when comparing two similar modes with displayed image sizes varying by a factor of 2. Case, mode, and reader-related variance components were estimated for the group of eight observers and subsets of readers after excluding each of the participants. RESULTS: There was no significant difference in the average area under the ROC curves between the two modes using the two image sizes (P > .05). Reader and reader-by-case variability were substantially larger for the mode displaying enlarged images for the group and all subsets formed by excluding a single reader. Reader variability was affected by one observer who actually performed better with the enlarged images. CONCLUSION: Sequential viewing of enlarged CT images for the detection of abdominal masses did not improve performance and increased reader variability.     

Diagnostic performance of teleradiology in cervical spine fracture detection.

This study was done to assess the diagnostic accuracy of high-resolution (5 lp/mm) teleradiology for detecting cervical spine fractures. Single radiographs from 25 patients with and 25 patients without cervical spine fractures were transmitted between two units of our teleradiology system (Dupont DTR 2000) located 5 miles apart. Each image was examined by four readers. Fracture detection accuracy was assessed by generating receiver operating characteristic (ROC) curves and comparing the areas under each reader's curves for original and transmitted images. Two readers had statistically significant better fracture detection using nontransmitted images, whereas two had no significant differences in accuracy. The authors conclude that high resolution in and of itself is not adequate for fracture detection, and that issues concerning image contrast manipulation also will have to be addressed before teleradiology systems can be used for clinical cervical spine fracture screening.     

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 liquid crystal display monitors on observer performance for detection of diffuse pulmonary disease on chest radiographs

Purpose The purpose of this study was to assess the influence of liquid crystal display (LCD) monitors on the detectability of diffuse pulmonary diseases depicted on chest radiographs by comparing them with a high-resolution cathode ray tube (CRT) monitor. Materials and methods A group of 17 radiologists interpreted 87 soft-copy images on LCD monitors with pixel arrays of 1024 × 1280, 1200 × 1600, 1536 × 2048, and 2048 × 2560 and on a CRT monitor with a pixel array of 2048 × 2560. They were asked to indicate their individual confidence levels regarding the presence of diffuse pulmonary diseases. The luminance distributions of all monitors were adjusted to the same distributions, and the ambient illumination was 200 lux. Observer performance was analyzed in terms of the receiver operating characteristics (ROC). Results The average ROC curves for the five monitor types were similar, and there were no statistically reliable effects of the five monitor types on the readers’ diagnostic performances (P = 0.7587). Conclusion The detectability of diffuse pulmonary disease on the LCD monitors with a spatial resolution equal to or higher than a matrix size of 1024 × 1280 was found to be equivalent to that on the high-resolution CRT monitor.     

Diagnostic accuracy and patient acceptance of MRI in children with suspected appendicitis

Objective

To compare magnetic resonance imaging (MRI) and ultrasound in children with suspected appendicitis.

Methods

In a single-centre diagnostic accuracy study, children with suspected appendicitis were prospectively identified at the emergency department. All underwent abdominal ultrasound and MRI within 2 h, with the reader blinded to other imaging findings. An expert panel established the final diagnosis after 3 months. We evaluated the diagnostic accuracy of three imaging strategies: ultrasound only, conditional MRI after negative or inconclusive ultrasound, and MRI only. Significance between sensitivity and specificity was calculated using McNemar’s test statistic.

Results

Between April and December 2009 we included 104 consecutive children (47 male, mean age 12). According to the expert panel, 58 patients had appendicitis. The sensitivity of MRI only and conditional MRI was 100 % (95 % confidence interval 92–100), that of ultrasound was significantly lower (76 %; 63–85, P?<?0.001). Specificity was comparable among the three investigated strategies; ultrasound only 89 % (77–95), conditional MRI 80 % (67–89), MRI only 89 % (77–95) (P values 0.13, 0.13 and 1.00).

Conclusion

In children with suspected appendicitis, strategies with MRI (MRI only, conditional MRI) had a higher sensitivity for appendicitis compared with a strategy with ultrasound only, while specificity was comparable.

Key Points

? In children, MRI has a higher sensitivity for appendicitis than ultrasound. ? Ultrasound followed by MRI in negative or inconclusive findings is accurate. ? The tolerance for ultrasound and MRI in children is comparable. ? MRI can be performed in children in an emergency setting.     

Diagnostic accuracy of computed tomography angiography in detection of post traumatic renal vascular injury

Objectives

To evaluate accuracy of computed tomography angiography (CTA) in evaluation of post traumatic renal vascular injury.

Influence of film and monitor display luminance on observer performance and visual search

RATIONALE AND OBJECTIVES: The purpose of this study was to measure the influence of display luminance on detection performance and visual search behavior. The results of the study should be helpful in establishing minimally acceptable display conditions for viewing radiographs on cathode-ray tube (CRT) monitors. MATERIALS AND METHODS: Two groups of six radiologists each viewed 50 pairs of mammograms. One group viewed film images on a standard mammographic view box; the other viewed images on a high-resolution CRT monitor. Two luminance levels were studied for each display type. Observers reported on the presence or absence of masses or microcalcification clusters and on their confidence in that decision. Confidence data were analyzed by using alternative free-response receiver operating characteristic (AFROC) techniques. Eye position also was recorded as observers viewed the images. RESULTS: For both the film and monitor studies, detection performance (AFROC area under the curve) was not affected significantly by display luminance, but search behavior was. Total viewing and decision dwell times were shorter with the higher-luminance displays, especially for true-negative decisions. Significantly more fixation clusters were generated during the search of lesion-free than of lesion-containing images with the lower-luminance displays. CONCLUSION: Display luminance affects visual search performance with both film and monitor displays without affecting detection performance significantly. Higher-luminance displays yield more efficient search performance. The true-negative dwell times and number of clusters are suggestive that lower-luminance levels prolong the search and recognition of normal, lesion-free areas compared with lesion-containing areas.     

Diagnostic outcome and observer performance in sagittal tomography of the temporomandibular joint

The diagnostic outcome and observer performance of sagittal tomography in detecting degenerative lesions of the temporomandibular joint was studied. Thirty tomograms depicting findings such as cyst, erosion, osteophyte and sclerosis and 30 with a normal appearance were selected. The joint status was verified histologically. Four observers evaluated the tomograms with the aid of reference tomograms, independent of the microscopic examination. The diagnostic accuracy was high (80-87%). The sensitivity was between 67% and 90% and the specificity between 73% and 93%. An osteophyte was, with few exceptions, a true finding whereas sclerosis most frequently was false. About two-thirds of the reports of cyst and erosion were found to be true. The interobserver overall agreement rates for any two observers varied between 68% and 90%, for three observers between 65% and 82%, and for all four observers was 63%. The Kappa value for any two observers was 0.40-0.80, indicating fair to substantial agreement. The intra-observer agreement was only somewhat higher than the interobserver. This study shows that, with the aid of reference tomograms, high diagnostic accuracy and observer agreement can be achieved in sagittal tomography.     

Dose reduction and its influence on diagnostic accuracy and radiation risk in digital mammography: an observer performance study using an anthropomorphic breast phantom

This study aimed to investigate the effect of dose reduction on diagnostic accuracy and radiation risk in digital mammography. Simulated masses and microcalcifications were positioned in an anthropomorphic breast phantom. Thirty digital images, 14 with lesions, 16 without, were acquired of the phantom using a Mammomat Novation (Siemens, Erlangen, Germany) at each of three dose levels. These corresponded to 100%, 50% and 30% of the normally used average glandular dose (AGD; 1.3 mGy for a standard breast). Eight observers interpreted the 90 unprocessed images in a free response study, and the data were analysed with the jackknife free response receiver operating characteristic (JAFROC) method. Observer performance was assessed using the JAFROC figure of merit (FOM). The benefit of radiation risk reduction was estimated based on several risk models. There was no statistically significant difference in performance, as described by the FOM, between the 100% and the 50% dose levels. However, the FOMs for both the 100% and the 50% dose were significantly different from the corresponding quantity for the 30% dose level (F-statistic = 4.95, p-value = 0.01). A dose reduction of 50% would result in three to nine fewer breast cancer fatalities per 100,000 women undergoing annual screening from the age of 40 to 49 years. The results of the study indicate a possibility of reducing the dose to the breast to half the dose level currently used. This has to be confirmed in clinical studies, and possible differences depending on lesion type should be examined further.     

Comparison of digital and conventional musculoskeletal radiography: an observer performance study

Interpretations of 122 musculoskeletal radiographs were compared with interpretations of their digital counterparts at a resolution of 1,024 X 840 X 12 bits. Images were evaluated by four readers and included subtle and nonsubtle abnormalities and normal findings. Joint receiver operating characteristic (ROC) analysis results were averaged over all readers and demonstrated no statistically significant difference between the two imaging methods. High interobserver variability limited identifiable differences. Review of cases with subtle findings on the digital system at a resolution of 2,048 X 1,680 X 12 bits (2.5 line pairs per millimeter) revealed adequate visualization of the abnormality in every case. It is concluded that a resolution of 1,024 X 840 X 12 bits is adequate for the interpretation of many musculoskeletal abnormalities but that a resolution of 2,048 X 1,680 X 12 bits is needed for visualization of some subtle abnormalities.     

Diagnostic accuracy of 18F-FDG PET/CT for detection of suspected recurrence in patients with oesophageal carcinoma

Purpose

To evaluate the role of ¹⁸F-FDG PET/CT in the detection of recurrence in patients with oesophageal carcinoma, suspected clinically or following conventional investigations.

Methods

This was a retrospective study. Data from 180 patients (age 56.3?±?10.4 years; 126 men, 54 women) with histopathologically proven oesophageal carcinoma (squamous cell 115, adenocarcinoma 59, neuroendocrine carcinoma 4, small cell 1, poorly differentiated 1) who had undergone 227 ¹⁸F-FDG PET/CT studies for suspected recurrence were analysed. Recurrence was suspected clinically or following conventional investigations. PET/CT images were revaluated by two nuclear medicine physicians in consensus. Findings were grouped into local, nodal and distant recurrence. Results were compared to those from contrast-enhanced (CE) CT when available (109 patients). Clinical/imaging follow-up (minimum 6 months) with histopathology (when available) was taken as the reference standard.

Results

Of the 227 ¹⁸F-FDG PET/CT studies,166 were positive and 61 were negative for recurrent disease. PET/CT showed local recurrence in 134, nodal recurrence in 115 and distant recurrence in 47, with more than one site of recurrence in 34. The PET/CT findings were true-positive in 153 studies, true-negative in 54, false-positive in 13 and false-negative in 7. The sensitivity of ¹⁸F-FDG PET/CT was 96 %, the specificity was 81 %, the positive and negative predictive values were 92 % and 89 %, respectively, and the accuracy was 91 %. PET/CT showed similar accuracy in patients with squamous cell carcinoma and in those with adenocarcinoma (P?=?0.181).¹⁸F-FDG PET/CT was more specific than CECT (67 % vs. 21 %; P?<?0.0001). PET/CT was superior to CECT for the detection of nodal recurrence (P?<?0.0001), but not local recurrence (P?=?0.093) or distant metastases (P?=?0.441).

Conclusion

¹⁸F-FDG PET/CT shows high accuracy in the detection of suspected recurrence in patients with oesophageal carcinoma. It is more specific than and is superior to CECT in the detection of nodal recurrence.