What limits performance of weakly supervised deep learning for chest CT classification?

Weakly supervised learning with noisy data has drawn attention in the medical imaging community due to the sparsity of high-quality disease labels. However, little is known about the limitations of such weakly supervised learning and the effect of these constraints on disease classification performance. In this paper, we test the effects of such weak supervision by examining model tolerance for three conditions. First, we examined model tolerance for noisy data by incrementally increasing error in the labels within the training data. Second, we assessed the impact of dataset size by varying the amount of training data. Third, we compared performance differences between binary and multi-label classification. Results demonstrated that the model could endure up to 10% added label error before experiencing a decline in disease classification performance. Disease classification performance steadily rose as the amount of training data was increased for all disease classes, before experiencing a plateau in performance at 75% of training data. Last, the binary model outperformed the multilabel model in every disease category. However, such interpretations may be misleading, as the binary model was heavily influenced by co-occurring diseases and may not have learned the specific features of the disease in the image. In conclusion, this study may help the medical imaging community understand the benefits and risks of weak supervision with noisy labels. Such studies demonstrate the need to build diverse, large-scale datasets and to develop explainable and responsible AI.Comment: 16 pages , 8 figures. arXiv admin note: text overlap with arXiv:2202.1170

Rate of change in abdominal aortic aneurysm diameter after endovascular repair

AbstractObjective: Untreated abdominal aortic aneurysms (AAAs) enlarge at a mean rate of 3.9 mm/y with great individual variability. We sought to determine the effect of endovascular repair on the rate of change in aneurysm size. Methods: There were 110 patients who underwent endovascular AAA repair at Stanford University Medical Center and who were followed up for 1 to 30 months (mean, 10 months) with serial contrast-infused helical computed tomography (CT). Maximal aneurysm diameter was determined using two independent methods: (1) measured manually, from cross-sectional computed tomography (XSCT) angiograms and (2) calculated from quantitative three-dimensional computed tomography (3DCT) data as orthonormal diameter. Results: Maximal cross-sectional aneurysm diameter measured by hand (XSCT) and calculated as orthonormal values (3DCT) correlated closely (r = 0.915; P <.001). The XSCT-measured diameter was larger by 2.3 ± 3.75 mm (P <.001), and the 95% CI for SE of the bias was 1.85 to 2.75 mm. Preoperative aneurysm diameter (XSCT 59.1 ± 8.4 mm; 3DCT 58.1 ± 9.3 mm) did not differ significantly from the initial postoperative diameter. Considering all patients, XSCT diameter decreased at a rate of 0.34 ± 0.69 mm/mo, and 3DCT diameter decreased at a rate of 0.28 ± 0.79 mm/mo. Aneurysms in patients without endoleaks had a higher rate of decrease, an XSCT diameter by 0.50 ± 0.74 mm/mo, and 3DCT diameter by 0.46 ± 0.84 mm/mo. In these patients, mean absolute decrease in diameter at 6 months was 3.4 ± 4.5 mm (XSCT) and 3.3 ± 5.9 mm (3DCT) and at 12 months, 5.9 ± 5.7 mm (XSCT) and 5.4 ± 5.7 mm (3DCT). Aneurysms in patients with persistent endoleaks did not change in mean XSCT diameter, and 3DCT diameter increased by 0.12 ± 0.52 mm/mo (not significant). Aneurysm diameter remained within 4 mm of original size in 68% (3DCT) to 71% (XSCT) of patients. In one patient, aneurysm diameter increased (XSCT and 3DCT) more than 5 mm. Four patients who had a new onset endoleak had a much higher expansion rate than those with a chronic endoleak (P <.05). Conclusions: The rate of decrease in aneurysm size (annualized 3.4-4.1 mm/y) after endovascular repair of AAA approximates the reported expansion rate in untreated aneurysms. However, individual aneurysm behavior is unpredictable, and the presence of an endoleak is unreliable in predicting changes in diameter. New onset endoleaks are associated with an enlargement rate greater than that of untreated aneurysms. (J Vasc Surg 2000;32:108-15.

Right coronary wall cmr in the older asymptomatic advance cohort: positive remodeling and associations with type 2 diabetes and coronary calcium

<p>Abstract</p> <p>Background</p> <p>Coronary wall cardiovascular magnetic resonance (CMR) is a promising noninvasive approach to assess subclinical atherosclerosis, but data are limited in subjects over 60 years old, who are at increased risk. The purpose of the study was to evaluate coronary wall CMR in an asymptomatic older cohort.</p> <p>Results</p> <p>Cross-sectional images of the proximal right coronary artery (RCA) were acquired using spiral black-blood coronary CMR (0.7 mm resolution) in 223 older, community-based patients without a history of cardiovascular disease (age 60-72 years old, 38% female). Coronary measurements (total vessel area, lumen area, wall area, and wall thickness) had small intra- and inter-observer variabilities (r = 0.93~0.99, all p < 0.0001), though one-third of these older subjects had suboptimal image quality. Increased coronary wall thickness correlated with increased coronary vessel area (p < 0.0001), consistent with positive remodeling. On multivariate analysis, type 2 diabetes was the only risk factor associated with increased coronary wall area and thickness (p = 0.03 and p = 0.007, respectively). Coronary wall CMR measures were also associated with coronary calcification (p = 0.01-0.03).</p> <p>Conclusions</p> <p>Right coronary wall CMR in asymptomatic older subjects showed increased coronary atherosclerosis in subjects with type 2 diabetes as well as coronary calcification. Coronary wall CMR may contribute to the noninvasive assessment of subclinical coronary atherosclerosis in older, at-risk patient groups.</p

CAD-RADS™ 2.0 - 2022 Coronary Artery Disease – Reporting and Data System an expert consensus document of the Society of Cardiovascular Computed Tomography (SCCT), the American College of Cardiology (ACC), the American College of Radiology (ACR) and the North America society of cardiovascular imaging (NASCI)

Coronary Artery Disease Reporting and Data System (CAD-RADS) was created to standardize reporting system for patients undergoing coronary CT angiography (CCTA) and to guide possible next steps in patient management. The goal of this updated 2022 CAD-RADS 2.0 is to improve the initial reporting system for CCTA by considering new technical developments in Cardiac CT, including data from recent clinical trials and new clinical guidelines. The updated CAD-RADS classification will follow an established framework of stenosis, plaque burden, and modifiers, which will include assessment of lesion-specific ischemia using CT fractional-flow-reserve (CT-FFR) or myocardial CT perfusion (CTP), when performed. Similar to the method used in the original CAD-RADS version, the determinant for stenosis severity classification will be the most severe coronary artery luminal stenosis on a per-patient basis, ranging from CAD-RADS 0 (zero) for absence of any plaque or stenosis to CAD-RADS 5 indicating the presence of at least one totally occluded coronary artery. Given the increasing data supporting the prognostic relevance of coronary plaque burden, this document will provide various methods to estimate and report total plaque burden. The addition of P1 to P4 descriptors are used to denote increasing categories of plaque burden. The main goal of CAD-RADS, which should always be interpreted together with the impression found in the report, remains to facilitate communication of test results with referring physicians along with suggestions for subsequent patient management. In addition, CAD-RADS will continue to provide a framework of standardization that may benefit education, research, peer-review, artificial intelligence development, clinical trial design, population health and quality assurance with the ultimate goal of improving patient care

A field assessment of the value of steady shape hydraulic tomography for characterization of aquifer heterogeneities

This is the published version. Copyright American Geophysical Union[1] Hydraulic tomography is a promising approach for obtaining information on variations in hydraulic conductivity on the scale of relevance for contaminant transport investigations. This approach involves performing a series of pumping tests in a format similar to tomography. We present a field-scale assessment of hydraulic tomography in a porous aquifer, with an emphasis on the steady shape analysis methodology. The hydraulic conductivity (K) estimates from steady shape and transient analyses of the tomographic data compare well with those from a tracer test and direct-push permeameter tests, providing a field validation of the method. Zonations based on equal-thickness layers and cross-hole radar surveys are used to regularize the inverse problem. The results indicate that the radar surveys provide some useful information regarding the geometry of the K field. The steady shape analysis provides results similar to the transient analysis at a fraction of the computational burden. This study clearly demonstrates the advantages of hydraulic tomography over conventional pumping tests, which provide only large-scale averages, and small-scale hydraulic tests (e.g., slug tests), which cannot assess strata connectivity and may fail to sample the most important pathways or barriers to flow

The genomes of two key bumblebee species with primitive eusocial organization

Background: The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High-quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats. Results: We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits. Conclusions: These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation

Characterisation of Australian MRSA Strains ST75- and ST883-MRSA-IV and Analysis of Their Accessory Gene Regulator Locus

Background: Community-acquired methicillin-resistant Staphylococcus aureus have become a major problem in Australia. These strains have now been isolated throughout Australia including remote Indigenous communities that have had minimal exposure to healthcare facilities. Some of these strains, belonging to sequence types ST75 and ST883, have previously been reported to harbour highly divergent alleles of the housekeeping genes used in multilocus sequence typing. Methodology/Principal Findings: ST75-MRSA-IV and ST883-MRSA-IV isolates were characterised in detail. Morphological features as well as 16S sequences were identical to other S. aureus strains. Although a partial rnpB gene sequence was not identical to previously known S. aureus sequences, it was found to be more closely related to S. aureus than to other staphylococci. Isolates also were screened using diagnostic DNA microarrays. These isolates yielded hybridisation results atypical for S. aureus. Primer directed amplification assays failed to detect species markers (femA, katA, sbi, spa). However, arbitrarily primed amplification indicated the presence of unknown alleles of these genes. Isolates could not be assigned to capsule types 1, 5 or 8. The allelic group of the accessory gene regulator (agr) locus was not determinable. Sequencing of a region of agrB, agrC and agrD (approximately 2,100 bp) revealed a divergent sequence. However, this sequence is more related to S. aureus agr alleles I and IV than to agr sequences from other Staphylococcus species. The predicted autoinducing peptide (AIP) sequence of ST75 was identical to that of agr group I, while the predicted AIP sequence of ST883 was identical to agr group IV. Conclusions/Significance: The genetic properties of ST75/ST883-MRSA may be due to a series of evolutionary events in ancient insulated S. aureus strains including a convergent evolution leading to agr group I- or IV-like AIP sequences and a recent acquisition of SCCmec IV elements

Integrating acute stroke telemedicine consultations into specialists' usual practice: a qualitative analysis comparing the experience of Australia and the United Kingdom

Stroke telemedicine can reduce healthcare inequities by increasing access to specialists. Successful telemedicine networks require specialists adapting clinical practice to provide remote consultations. Variation in experiences of specialists between different countries is unknown. To support future implementation, we compared perceptions of Australian and United Kingdom specialists providing remote acute stroke consultations. Specialist participants were identified using purposive sampling from two new services: Australia's Victorian Stroke Telemedicine Program (n = 6; 2010-13) and the United Kingdom's Cumbria and Lancashire telestroke network (n = 5; 2010-2012). Semi-structured interviews were conducted pre- and post-implementation, recorded and transcribed verbatim. Deductive thematic and content analysis (NVivo) was undertaken by two independent coders using Normalisation Process Theory to explore integration of telemedicine into practice. Agreement between coders was M = 91%, SD = 9 and weighted average κ = 0.70. Cross-cultural similarities and differences were found. In both countries, specialists described old and new consulting practices, the purpose and value of telemedicine systems, and concerns regarding confidence in the assessment and diagnostic skills of unknown colleagues requesting telemedicine support. Australian specialists discussed how remote consultations impacted on usual roles and suggested future improvements, while United Kingdom specialists discussed system governance, policy and procedures. Australian and United Kingdom specialists reported telemedicine required changes in work practice and development of new skills. Both groups described potential for improvements in stroke telemedicine systems with Australian specialists more focused on role change and the United Kingdom on system governance issues. Future research should examine if cross-cultural variation reflects different models of care and extends to other networks