Image size influences visual search and perception of hemorrhages when reading cranial CT: an eye tracking study

Objectives: To explore reader gaze, performance and preference during interpretation of cranial computed tomography (cCT) in stack mode at two different sizes. Background: Digital display of medical images allows for the manipulation of many imaging factors, like image size, by the radiologists, yet it is often not known what display parameters better suit human perception. Materials and Methods: Twenty-one radiologists provided informed consent to be eye tracked while reading 20 cCT cases. Half of these cases were presented at a size of 14x14 cm (512x512 pixels), half at 28x28 cm (1024x1024 pixels). Visual search, performance and preference for the two image sizes were assessed. Results: When reading small images significantly fewer, but longer fixations were observed, and these covered significantly more slices. Time to first fixation of True Positive findings was faster in small images, but dwell time on true findings was longer. Readers made more False Positive decisions in small images, but no overall difference in either JAFROC or reading time was found. Conclusions: Overall performance is not affected by image size. However, small stack mode cCT images may better support the use of motion perception and acquiring an overview, whereas large stack mode cCT images seem better suited for detailed analyses. Application: Subjective and eye tracking data suggest that image size influences how images are searched and that different search strategies might be beneficial under different circumstances

Color Calibration In Digital Pathology: The Clinical Impact Of A Novel Test Object

Introduction/ Background Guidance from the Food and Drug Administration has recommended color standardization for whole slide imaging, as with all other digital systems. However there is known, unresolved and substantial variation in color between digital slide scanners. To address this issue, we created a novel color calibration test object which uniquely utilizes histochemical stains and a tissue-like substrate, affording accurate internal calibration of WSIs. Aims We aimed to evaluate the clinical application of the novel test object. Objectives included: 1. Whether calibration made WSIs appear closer in color to the glass slide counterpart; 2. Whether pathologists prefer calibrated WSIs; and, 3. Whether calibration affected diagnostic confidence. Methods Six pathology cases that present known difficulties when viewed using a digital microscope were selected and WSIs were generated. These WSIs were calibrated using a color ICC profile created using spectral measurements from the test object. Twelve pathologists, blinded to intervention, compared calibrated and uncalibrated versions of each WSI on a medical-grade monitor. The display was color calibrated using a colorimeter which accounted for ambient lighting. Three, subjective responses were recorded on 7-point Likert scales. Results Calibrated WSIs were closer in appearance to the microscope in 40 of 72 trials, (56%) and were preferred in 46 of 72 trials (64%). Calibration improved diagnostic confidence (median 6.00 vs. 5.00, p=0.001). Diagnostic confidence with the calibrated slides was correlated with preference for color calibration (r=0.499; p<0.001)

The variation of radiologists' performance over the course of a reading session

The radiologist's task of reviewing many cases successively is highly repetitive and requires a high level of concentration. Fatigue effects have, for example, been shown in studies comparing performance at different times of day. However, little is known about changes in performance during an individual reading session. During a session reading an enriched case set, performance may be affected by both fatigue (i.e. decreasing performance) and training (i.e. increasing performance) effects. In this paper, we reanalyze 3 datasets from 4 studies for changes in radiologist performance during a reading session. Studies feature 8-20 radiologists reading and assessing 27-60 cases in single, uninterrupted sessions. As the studies were not designed for this analysis, study setups range from bone fractures to mammograms and randomization varies between studies. Thus, they are analyzed separately using mixed-effects models. There is some indication that, as time goes on, specificity increases (shown with p<0.05 for 2 out of 3 datasets, no significant difference for the other) while sensitivity may also increase (p<0.05 for 1 out of 3 datasets). The difficulty of 'normal' (healthy / non-malignant) and 'abnormal' (unhealthy / malignant) cases differs (p<0.05 for 3 out of 3 datasets) and the reader's experience may also be relevant (p<0.05 for 1 out of 3 datasets). These results suggest that careful planning of breaks and session length may help optimize reader performance. Note that the overall results are still inconclusive and a targeted study to investigate fatigue and training effects within a reading session is recommended. © 2013 SPIE

Retrospective review of the drop in observer detection performance over time in lesion-enriched experimental studies.

The vigilance decrement describes a decrease in sensitivity or increase in specificity with time on task. It has been observed in a variety of repetitive visual tasks, but little is known about these patterns in radiologists. We investigated whether there is systematic variation in performance over the course of a radiology reading session. We re-analyzed data from six previous lesion-enriched radiology studies. Studies featured 8-22 participants assessing 27-100 cases (including mammograms, chest CT, chest x-ray, and bone x-ray) in a reading session. Changes in performance and speed as the reading session progressed were analyzed using mixed effects models. Time taken per case decreased 9-23% as the reading session progressed (p < 0.005 for every study). There was a sensitivity decrease or specificity increase over the course of reading 100 chest x-rays (p = 0.005), 60 bone fracture x-rays (p = 0.03), and 100 chest CT scans (p < 0.0001). This effect was not found in the shorter mammography sessions with 27 or 50 cases. We found evidence supporting the hypothesis that behavior and performance may change over the course of reading an enriched test set. Further research is required to ascertain whether this effect is present in radiological practice

Breast cancer in Mongolia: an increasingly important health policy issue

Delgermaa Demchig,&nbsp;Claudia Mello-Thoms,&nbsp;Patrick C Brennan Medical Image Optimization and Perception Group (MIOPeG), Faculty of Health Science, The University of Sydney, Sydney, NSW, Australia Abstract: Breast cancer is a leading cause of cancer-related death for women in both developed and developing countries. The incidence and mortality of breast cancer in Mongolia, while low compared with other counties, has been increasing on an annual basis. In addition, in Mongolia, approximately 90% of the patients are diagnosed at a late stage, resulting in high mortality, with the majority of individuals diagnosed with breast cancer dying within 5 years of diagnosis. Breast cancer screening plays an important role in reducing mortality in Western countries and has been adopted by a number of Asian countries; however, no such approach exists in Mongolia. In a country of limited resources, implementation of expensive health strategies such as screening requires effective allocations of resources and the identification of the most effective imaging methods. This requirement relies on recent accurate data; however, at this time, there is a paucity of information around breast cancer in Mongolia. Until data around features of the disease are available, effective strategies to diagnose breast cancer that recognize the economic climate in Mongolia cannot be implemented and the impact of breast cancer is likely to increase. Keywords: incidence, mortality, breast screening, Mongoli

Computer-based image analysis in breast pathology

Whole slide imaging (WSI) has the potential to be utilized in telepathology, teleconsultation, quality assurance, clinical education, and digital image analysis to aid pathologists. In this paper, the potential added benefits of computer-assisted image analysis in breast pathology are reviewed and discussed. One of the major advantages of WSI systems is the possibility of doing computer-based image analysis on the digital slides. The purpose of computer-assisted analysis of breast virtual slides can be (i) segmentation of desired regions or objects such as diagnostically relevant areas, epithelial nuclei, lymphocyte cells, tubules, and mitotic figures, (ii) classification of breast slides based on breast cancer (BCa) grades, the invasive potential of tumors, or cancer subtypes, (iii) prognosis of BCa, or (iv) immunohistochemical quantification. While encouraging results have been achieved in this area, further progress is still required to make computer-based image analysis of breast virtual slides acceptable for clinical practice

Determining image processing features describing the appearance of challenging mitotic figures and miscounted nonmitotic objects

Context: Previous studies showed that the agreement among pathologists in recognition of mitoses in breast slides is fairly modest. Aims: Determining the significantly different quantitative features among easily identifiable mitoses, challenging mitoses, and miscounted nonmitoses within breast slides and identifying which color spaces capture the difference among groups better than others. Materials and Methods: The dataset contained 453 mitoses and 265 miscounted objects in breast slides. The mitoses were grouped into three categories based on the confidence degree of three pathologists who annotated them. The mitoses annotated as “probably a mitosis” by the majority of pathologists were considered as the challenging category. The miscounted objects were recognized as a mitosis or probably a mitosis by only one of the pathologists. The mitoses were segmented using k-means clustering, followed by morphological operations. Morphological, intensity-based, and textural features were extracted from the segmented area and also the image patch of 63 × 63 pixels in different channels of eight color spaces. Holistic features describing the mitoses' surrounding cells of each image were also extracted. Statistical Analysis Used: The Kruskal–Wallis H-test followed by the Tukey-Kramer test was used to identify significantly different features. Results: The results indicated that challenging mitoses were smaller and rounder compared to other mitoses. Among different features, the Gabor textural features differed more than others between challenging mitoses and the easily identifiable ones. Sizes of the non-mitoses were similar to easily identifiable mitoses, but nonmitoses were rounder. The intensity-based features from chromatin channels were the most discriminative features between the easily identifiable mitoses and the miscounted objects. Conclusions: Quantitative features can be used to describe the characteristics of challenging mitoses and miscounted nonmitotic objects