Obuchowski-Rockette analysis for multi-reader multi-case (MRMC) readers-nested-in-test study design with unequal numbers of readers.

The Obuchowski-Rockette method has been an important tool for analyzing multi-reader multi-case (MRMC) radiologic imaging data. Although the typical study design for such studies has been the factorial design, where each reader reads each case using each test (modality), sometimes a reader-nested-in-test design is more appropriate. We consider such an example in this talk, where 53 Australian and 15 Singaporean breast radiologists interpreted the same test in their respective locations. In this paper we show how the Obuchowski-Rockette method can be used for analysis of such data, without assuming that the number of readers is the same for each test.

Body composition reference values in Singaporean adults using dual-energy X-ray absorptiometry-The Yishun study.

OBJECTIVES: This study establishes age- and sex-specific reference values for fat mass index (FMI), lean mass index (LMI), appendicular LMI (aLMI), and body fat distribution indices including Android/Gynoid % fat ratio and Trunk/Limb % fat ratio in multi-ethnic Singaporean adults. METHODS: A population-based cross-sectional study using dual-energy X-ray absorptiometry (Hologic Discovery Wi) was carried out to measure whole body and regional fat and lean mass in community-dwelling adults. A total of 537 adults (57.5% women), aged from 21 to 90 years, were recruited from the large north-eastern residential town of Yishun. Age- and sex-specific percentile reference values were generated for FMI, LMI, aLMI, Android/Gynoid % fat ratio and Trunk/Limb % fat ratio using the Lambda-Mu-Sigma method. The relationship between the parameters and age were assessed through the Pearson's correlation coefficient. RESULTS: All parameters demonstrated significant correlation with age (p < 0.05) for both men and women, except for LMI in women, with the strength of r ranging from 0.12 (weak correlation) to 0.54 (strong correlation). LMI (r = -0.45) and appendicular LMI (r = -0.54) were negatively associated with age in men while none (r = -0.06) to weak correlation (r = -0.14) were shown in women for the same parameters respectively. The Android/Gynoid % fat ratio and Trunk/Limb % fat ratio were positively related to age for both men (r = 0.37 & 0.43, p < 0.001) and women (r = 0.52 & 0.48, p < 0.001). CONCLUSION: We have established DXA-based body composition reference data for the Singapore adult population. These reference data will be particularly useful in geriatric, obesity and oncology clinics, enabling the prescription of appropriate therapy to individuals at risk of morbidity from unfavorable body composition phenotypes. It also adds on to the limited reference database on Southeast Asian body composition.

Telereporting in Breast Imaging Involving More Than 1 Country Requires Careful Consideration.

PURPOSE: To examine the effect that a test set from 1 region of the world has on the performance of expert breast radiologists from that region and from a distant region. METHODS: Forty-seven Australian and 15 Singaporean breast radiologists interpreted the same test set (ie, 60 mammograms of Australian women consisting of 40 typical and 20 atypical cases) in their respective locations. The radiologists assigned each case a confidence score of 1 to 5, where 1 was typical, 2 was benign, and 3 to 5 indicated identifiable cancer. Localization-response operating characteristic area under the curve (AUC), receiver operating characteristic AUC, location sensitivity, case sensitivity, and specificity were calculated for each radiologist and compared between Australian and Singaporean readers using nonparametric 2-tailed Mann-Whitney U tests. RESULTS: Australian readers performed better than did their Singaporean counterparts with respect to localization-response operating characteristic AUC (.738 vs .642, P = .0395) and location sensitivity (.775 vs .660, P = .0185). DISCUSSION: Technological advancement has made possible telereporting, in which radiologists report on mammograms originating from other countries. However, those readers' levels of performance might be affected by interpreting images from populations that are different from those with which they are familiar. CONCLUSION: Radiologist performance differed between the groups when localization of lesions was taken into account. This difference might be because of the Australians' reading mammograms from populations with which they were familiar, in contrast to the Singaporeans.

Rates and Predictors of Nonadherence to Postophthalmic Screening Tertiary Referrals in Patients with Type 2 Diabetes.

Purpose: To determine the rates and develop an initial risk prediction model for nonadherence to post screening ophthalmic referral (PSOR) in type 2 diabetes mellitus (T2DM) patients attending a national diabetic retinopathy screening program in Singapore. Methods: Data from 2387 patients with T2DM (mean [standard deviation] age: 66.5 [11] years; 52.5% female patients) who underwent teleophthalmic screening between 2010 and 2014 under the Singapore Integrated Diabetic Retinopathy Program were extracted from electronic medical records. All were referred for tertiary ophthalmic management at the Singapore National Eye Centre (SNEC). Nonadherence was defined as not attending the SNEC appointment within 6 months of the assigned appointment date. Regression analysis using traditional modified Poisson and conditional inference models was used to construct and evaluate the discriminative ability of the preliminary risk prediction model to identify nonadherent individuals. Results: Nonadherence rates to PSOR was 12.7% (95% confidence interval, 11.4%-14.1%). In traditional multivariable models adjusted for sociodemographic, lifestyle, and ocular factors, nonadherent individuals had higher triglyceride levels and were less likely to have a referable eye condition (P < 0.05). This model was able to identify nonadherent individuals with an accuracy (area under the curve) of 84%. In contrast, the conditional inference model was able to achieve similar discriminative ability using only participants' ocular health characteristics. Conclusions: The rates of nonadherence to PSOR in Singaporean individuals with T2DM is low, with better ocular health being strongly predictive of nonadherence in our Asian population. Translational Relevance: Our results may inform interventions to decrease nonadherence to PSOR.

Breast Cancer Diagnostic Efficacy in a Developing South-East Asian Country

Background: Breast cancer, is increasing in prevalence amongst South East (SE) Asian women, highlighting the need for high quality, early diagnoses. This study investigated radiologists' detection efficacy in a developing (DC) and developed (DDC) SE Asian country, as compared to Australian radiologists. Methods: Using a test-set of 60 mammographic cases, 20 containing cancer, JAFROC figures of merit (FOM) and ROC area under the curves (AUC) were calculated as well as location sensitivity, sensitivity and specificity. The test set was examined by 35, 15, and 53 radiologists from DC, a DDC and Australia, respectively. Results: DC radiologists, compared to both groups of counterparts, demonstrated significantly lower JAFROC FOM, ROC AUC and specificity scores. DC radiologists had a significantly lower location sensitivity than Australian radiologists. DC radiologists also demonstrated significantly lower values for age, hours of reading per week, and years of mammography experience when compared with other radiologists. Conclusion: Significant differences in breast cancer detection parameters can be attributed to the experience of DC radiologists. The development of inexpensive, innovative, interactive training programs are discussed. This nonuniform level of breast cancer detection between countries must be addressed to achieve the World Health Organisation goal of health equity.

Certain performance values arising from mammographic test set readings correlate well with clinical audit.

INTRODUCTION: Test sets have been increasingly utilised to augment clinical audit in breast screening programmes; however, their relationship has never been satisfactorily understood. This study examined the relationship between mammographic test set performance and clinical audit data. METHODS: Clinical audit data over a 2-year period was generated for each of 20 radiologists. Sixty mammographic examinations, consisting of 40 normal and 20 cancer cases, formed the test set. Readers located any identifiable cancer, and levels of confidence were scored from 2 to 5, where a score of 3 and above is considered a recall rating. Jackknifing free response operating characteristic (JAFROC) figure-of-merit (FOM), location sensitivity and specificity were calculated for individual readers and then compared with clinical audit values using Spearman's rho. RESULTS: JAFROC FOM showed significant correlations to: recall rate at a first round of screening (r = 0.51; P = 0.02); rate of small invasive cancers per 10 000 reads (r = 0.5; P = 0.02); percentage of all cancers read that were not recalled (r = -0.51; P = 0.02); and sensitivity (r = 0.51; P = 0.02). Location sensitivity demonstrated significant correlations with: rate of small invasive cancers per 10 000 reads (r = 0.46; P = 0.04); rate of DCIS (ductal carcinoma in situ) per 10 000 reads (r = 0.44; P = 0.05); detection rate of all invasive cancers and DCIS per 10 000 reads (r = 0.54; P = 0.01); percentage of all cancers read that were not recalled (r = -0.57; P = 0.009); and sensitivity (r = 0.57; P = 0.009). No other significant relationships were noted. CONCLUSION: Performance indicators from test set demonstrate significant correlations with specific aspects of clinical performance, although caution needs to be exercised when generalising test set specificity to the clinical situation.

E-tutorial improves students' ability to detect lesions.

PURPOSE: This Australian study explores the effects of an educational intervention on first-year medical radiation sciences (MRS) students by examining eye-tracking metrics while they attempted to detect breast lesions on radiologic images before and after an e-learning tutorial. The study also analyzes performance using receiver operating characteristic methodology. METHODS: Fourteen first-year MRS students were equally and randomly assigned to a control or experiment group to participate in 2 image-detection sessions. The experiment group completed an online e-learning tutorial between sessions. Eighty mammographic breast images from 20 cases were obtained from a validated online image bank. Of those 20 cases, 30% were normal and 70% demonstrated a single-lesion abnormality. RESULTS: The experiment group demonstrated a 45% increase in the mean number of fixations per case (P = .047), with a 30% increase in sensitivity (P = .022) following the tutorial. The experiment group also demonstrated improved lesion detection overall and a 49% decrease in mean time to first fixation on the lesion (P = .016). DISCUSSION: This study demonstrates that increased lesion detection is possible after a brief e-learning tutorial. Early changes in the viewing patterns of less-experienced technologists are intriguing, and explanation may be gained from our current understanding of radiologic perception and cognitive neuroscience. The task for the first-year MRS students in this study was only to positively detect a lesion, and we recognize that a higher level of visual processing would be required to critique image quality. Exposure to the brief tutorial, however, might have triggered some learning-related neural changes at an early level of visual processing, representing stimuli relating to task performance. CONCLUSION: Participants in the experiment group improved their ability to identify breast lesions, which coincided with changes in eye position metrics and error type analysis. The data presented here suggest that the intervention resulted in a significant improvement in detection by the experiment group.

Breast screen new South wales generally demonstrates good radiologic viewing conditions.

This study measured reading workstation monitors and the viewing environment currently available within BreastScreen New South Wales (BSNSW) centres to determine levels of adherence to national and international guidelines. Thirteen workstations from four BSNSW service centres were assessed using the American Association of Physicists in Medicine Task Group 18 Quality Control test pattern. Reading workstation monitor performance and ambient light levels when interpreting screening mammographic images were assessed using spectroradiometer CS-2000 and chroma meter CL-200. Overall, radiologic monitors within BSNSW were operating at good acceptable levels. Some non-adherence to published guidelines included the percentage difference in maximum luminance between pairs of primary monitors at individual workstations (61.5 % or 30.8 % of workstations depending on specific guidelines), maximum luminance (23.1 % of workstations), luminance non-uniformity (11.5 % of workstations) and minimum luminance (3.8 % of workstations). A number of ambient light measurements did not comply with the only available evidence-based guideline relevant to the methodology used in this study. Larger ambient light variations across sites are shown when monitors were switched off, suggesting that differences in ambient lighting between sites can be masked when a standard mammogram is displayed for photometric measurements. Overall, BSNSW demonstrated good adherence to available guidelines, although some non-compliance has been shown. Recently updated United Kingdom and Australian guidelines should help reduce confusion generated by the plethora and sometimes dated nature of currently available recommendations.