Arterial spin-labeled (ASL) perfusion in children with Sturge-Weber syndrome: a retrospective cross-sectional study

PURPOSE

Sturge-Weber syndrome (SWS) is a developmental disorder with venous hypertension and associated tissue responses including pial angiomatosis, cortical calcifications, and cerebral atrophy. Arterial spin-labeled (ASL) perfusion is an advanced MR sequence which can assess perfusion, without the need for contrast. We systematically evaluated the potential benefits of using ASL in Sturge-Weber syndrome, to determine the extent of intracranial perfusion abnormality and stage of disease, relevant for prognostication and surgical planning.

METHODS

Two pediatric neuroradiologists retrospectively evaluated ASL perfusion imaging of 31 children with confirmed SWS and recorded the presence of hyper-perfusion, hypo-perfusion, or normal perfusion. The presence and distribution of ASL abnormality were compared against the presence and side of atrophy/calcification and pial angiomatosis on standard MR sequences.

RESULTS

Thirty-one children (52% female, median age 16.7 months) with SWS had ASL imaging. Seven (23%) had hyper-perfusion, 15 (48%) had hypo-perfusion, and 9 (29%) had no perfusion abnormalities. ASL perfusion abnormality matched the location of SWS findings on conventional imaging in 86% (19/22). ASL demonstrated statistically significant increased perfusion in the early stage of the disease and decreased perfusion when there was atrophy. The parietal lobe was involved in 86% of cases.

CONCLUSION

ASL perfusion imaging is an advanced technique which may contribute to earlier diagnosis and more accurate prognostication of Sturge-Weber syndrome, helping guide management and potential surgical planning.

Radiology artificial intelligence: a systematic review and evaluation of methods (RAISE)

OBJECTIVE

There has been a large amount of research in the field of artificial intelligence (AI) as applied to clinical radiology. However, these studies vary in design and quality and systematic reviews of the entire field are lacking.This systematic review aimed to identify all papers that used deep learning in radiology to survey the literature and to evaluate their methods. We aimed to identify the key questions being addressed in the literature and to identify the most effective methods employed.

METHODS

We followed the PRISMA guidelines and performed a systematic review of studies of AI in radiology published from 2015 to 2019. Our published protocol was prospectively registered.

RESULTS

Our search yielded 11,083 results. Seven hundred sixty-seven full texts were reviewed, and 535 articles were included. Ninety-eight percent were retrospective cohort studies. The median number of patients included was 460. Most studies involved MRI (37%). Neuroradiology was the most common subspecialty. Eighty-eight percent used supervised learning. The majority of studies undertook a segmentation task (39%). Performance comparison was with a state-of-the-art model in 37%. The most used established architecture was UNet (14%). The median performance for the most utilised evaluation metrics was Dice of 0.89 (range .49-.99), AUC of 0.903 (range 1.00-0.61) and Accuracy of 89.4 (range 70.2-100). Of the 77 studies that externally validated their results and allowed for direct comparison, performance on average decreased by 6% at external validation (range increase of 4% to decrease 44%).

CONCLUSION

This systematic review has surveyed the major advances in AI as applied to clinical radiology.

KEY POINTS

• While there are many papers reporting expert-level results by using deep learning in radiology, most apply only a narrow range of techniques to a narrow selection of use cases. • The literature is dominated by retrospective cohort studies with limited external validation with high potential for bias. • The recent advent of AI extensions to systematic reporting guidelines and prospective trial registration along with a focus on external validation and explanations show potential for translation of the hype surrounding AI from code to clinic.

Radiology artificial intelligence, a systematic evaluation of methods (RAISE): a systematic review protocol

INTRODUCTION

There has been a recent explosion of research into the field of artificial intelligence as applied to clinical radiology with the advent of highly accurate computer vision technology. These studies, however, vary significantly in design and quality. While recent guidelines have been established to advise on ethics, data management and the potential directions of future research, systematic reviews of the entire field are lacking. We aim to investigate the use of artificial intelligence as applied to radiology, to identify the clinical questions being asked, which methodological approaches are applied to these questions and trends in use over time.

METHODS AND ANALYSIS

We will follow the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines and by the Cochrane Collaboration Handbook. We will perform a literature search through MEDLINE (Pubmed), and EMBASE, a detailed data extraction of trial characteristics and a narrative synthesis of the data. There will be no language restrictions. We will take a task-centred approach rather than focusing on modality or clinical subspecialty. Sub-group analysis will be performed by segmentation tasks, identification tasks, classification tasks, pegression/prediction tasks as well as a sub-analysis for paediatric patients.

ETHICS AND DISSEMINATION

Ethical approval will not be required for this study, as data will be obtained from publicly available clinical trials. We will disseminate our results in a peer-reviewed publication. Registration number PROSPERO: CRD42020154790.

Differentiating combined pulmonary fibrosis and emphysema from pure emphysema: utility of late gadolinium-enhanced MRI

Background

Differentiating combined pulmonary fibrosis with emphysema (CPFE) from pure emphysema can be challenging on high-resolution computed tomography (HRCT). This has antifibrotic therapy implications.

Methods

Twenty patients with suspected CPFE underwent late gadolinium-enhanced (LGE) thoracic magnetic resonance imaging (LGE-MRI) and HRCT. Data from twelve healthy control subjects from a previous study who underwent thoracic LGE-MRI were included for comparison. Quantitative LGE signal intensity (SI) was retrospectively compared in regions of fibrosis and emphysema in CPFE patients to similar lung regions in controls. Qualitative comparisons for the presence/extent of reticulation, honeycombing, and traction bronchiectasis between LGE-MRI and HRCT were assessed by two readers in consensus.

Results

There were significant quantitative differences in fibrosis SI compared to emphysema SI in CPFE patients (25.8, IQR 18.4–31.0 versus 5.3, IQR 5.0–8.1, p < 0.001). Significant differences were found between LGE-MRI and HRCT in the extent of reticulation (12.5, IQR 5.0–20.0 versus 25.0, IQR 15.0–26.3, p = 0.038) and honeycombing (5.0, IQR 0.0–10.0 versus 20.0, IQR 10.6–20.0, p = 0.001) but not traction bronchiectasis (10.0, IQR 5–15 versus 15.0, IQR 5–15, p = 0.878). Receiver operator curve analysis of fibrosis SI compared to similarly located regions in control subjects showed an area under the curve of 0.82 (p = 0.002). A SI cutoff of 19 yielded a sensitivity of 75% and specificity of 86% in differentiating fibrosis from similarly located regions in control subjects.

Conclusion

LGE-MRI can differentiate CPFE from pure emphysema and may be a useful adjunct test to HRCT in patients with suspected CPFE.

The 100 Citation Classics in the Irish Medical Literature; A Bibliometric Analysis

Identifying citation classics is a valuable metric of research performance. Ireland has a distinguished history of medical research, although Ireland's top-cited articles are unknown. The SCOPUS database identified all medical and surgical articles published by journals in the Republic of Ireland or Northern Ireland. The 100 top-cited articles were analysed. The most cited article received 240 citations. There is an observed trend of increasing number of authors over time (p<0.05). General medicine and public health are the most common topics. The majority of works originate from Irish institutions. Collaborative research and non-Irish research are poorly represented among the citation classics. The Irish medical literature contains multiple highly cited and influential articles.

Martian CH(4): sources, flux, and detection

Recent observations have detected trace amounts of CH(4) heterogeneously distributed in the martian atmosphere, which indicated a subsurface CH(4) flux of ~2 x 10(5) to 2 x 10(9) cm(2) s(1). Four different origins for this CH(4) were considered: (1) volcanogenic; (2) sublimation of hydrate- rich ice; (3) diffusive transport through hydrate-saturated cryosphere; and (4) microbial CH(4) generation above the cryosphere. A diffusive flux model of the martian crust for He, H(2), and CH(4) was developed based upon measurements of deep fracture water samples from South Africa. This model distinguishes between abiogenic and microbial CH(4) sources based upon their isotopic composition, and couples microbial CH(4) production to H(2) generation by H(2)O radiolysis. For a He flux of approximately 10(5) cm(2) s(1) this model yields an abiogenic CH(4) flux and a microbial CH(4) flux of approximately 10(6) and approximately 10(9) cm(2) s(1), respectively. This flux will only reach the martian surface if CH(4) hydrate is saturated in the cryosphere; otherwise it will be captured within the cryosphere. The sublimation of a hydrate-rich cryosphere could generate the observed CH(4) flux, whereas microbial CH(4) production in a hypersaline environment above the hydrate stability zone only seems capable of supplying approximately 10(5) cm(2) s(1) of CH(4). The model predicts that He/H(2)/CH(4)/C(2)H(6) abundances and the C and H isotopic values of CH(4) and the C isotopic composition of C(2)H(6) could reveal the different sources. Cavity ring-down spectrometers represent the instrument type that would be most capable of performing the C and H measurements of CH(4) on near future rover missions and pinpointing the cause and source of the CH(4) emissions.

Concepts and approaches to in situ luminescence dating of Martian sediments

In this paper we present the concept of a robotic instrument for in situ luminescence dating of near-surface sediments on Mars. The scientific objectives and advantages to be gained from the development of such an instrument are described, and the challenges presented by the Mars surface environment to the design and operation of the instrument are outlined.

The state and future of Mars polar science and exploration

As the planet's principal cold traps, the martian polar regions have accumulated extensive mantles of ice and dust that cover individual areas of approximately 10(6) km2 and total as much as 3-4 km thick. From the scarcity of superposed craters on their surface, these layered deposits are thought to be comparatively young--preserving a record of the seasonal and climatic cycling of atmospheric CO2, H2O, and dust over the past approximately 10(5)-10(8) years. For this reason, the martian polar deposits may serve as a Rosetta Stone for understanding the geologic and climatic history of the planet--documenting variations in insolation (due to quasiperiodic oscillations in the planet's obliquity and orbital elements), volatile mass balance, atmospheric composition, dust storm activity, volcanic eruptions, large impacts, catastrophic floods, solar luminosity, supernovae, and perhaps even a record of microbial life. Beyond their scientific value, the polar regions may soon prove important for another reason--providing a valuable and accessible reservoir of water to support the long-term human exploration of Mars. In this paper we assess the current state of Mars polar research, identify the key questions that motivate the exploration of the polar regions, discuss the extent to which current missions will address these questions, and speculate about what additional capabilities and investigations may be required to address the issues that remain outstanding.