Computing thickness of irregularly-shaped thin walls using a locally semi-implicit scheme with extrapolation to solve the Laplace equation: Application to the right ventricle.

Cardiac Magnetic Resonance (CMR) Imaging is currently considered the gold standard imaging modality in cardiology. However, it is accompanied by a tradeoff between spatial resolution and acquisition time. Providing accurate measures of thin walls relative to the image resolution may prove challenging. One such anatomical structure is the cardiac right ventricle. Methods for measuring thickness of wall-like anatomical structures often rely on the Laplace equation to provide point-to-point correspondences between both boundaries. This work presents limex, a novel method to solve the Laplace equation using ghost nodes and providing extrapolated values, which is tested on three different datasets: a mathematical phantom, a set of biventricular segmentations from CMR images of ten pigs and the database used at the RV Segmentation Challenge held at MICCAI'12. Thickness measurements using the proposed methodology are more accurate than state-of-the-art methods, especially with the coarsest image resolutions, yielding mean L1 norms of the error between 43.28% and 86.52% lower than the second-best methods on the different test datasets. It is also computationally affordable. Limex has outperformed other state-of-the-art methods in classifying RV myocardial segments by their thickness.

Methylprednisolone Pulses in Hospitalized COVID-19 Patients Without Respiratory Failure: A Randomized Controlled Trial.

Background: Corticosteroids are the cornerstone of the treatment of patients with COVID-19 admitted to hospital. However, whether corticosteroids can prevent respiratory worsening in hospitalized COVID-19 patients without oxygen requirements is currently unknown. Aims: To assess the efficacy of methylprednisolone pulses (MPP) in hospitalized COVID-19 patients with increased levels of inflammatory markers not requiring oxygen at baseline. Methods: Multicenter, parallel, randomized, double-blind, placebo-controlled trial conducted in Spain. Patients admitted for confirmed SARS-CoV-2 pneumonia with raised inflammatory markers (C-reactive protein >60 mg/L, interleukin-6 >40 pg/ml, or ferritin >1,000 µg/L) but without respiratory failure after the first week of symptom onset were randomized to receive a 3-day course of intravenous MPP (120 mg/day) or placebo. The primary outcome was treatment failure at 14 days, a composite variable including mortality, the need for ICU admission or mechanical ventilation, and clinical worsening, this last parameter defined as a PaO2/FiO2 ratio below 300; or a 15% decrease in the PaO2 from baseline, together with an increase in inflammatory markers or radiological progression. If clinical worsening occurred, patients received tocilizumab and unmasked corticosteroids. The secondary outcomes were 28-day mortality, adverse events, need for ICU admission or high-flow oxygen, length of hospital stay, SARS-CoV-2 clearance, and changes in laboratory parameters. Results: A total of 72 patients were randomized and 71 patients were analyzed (34 in the MPP group and 37 in the placebo group). Twenty patients presented with treatment failure (29.4 in the MPP group vs. 27.0% in the placebo group, p = 0.82), with no differences regarding the time to treatment failure between groups. There were no cases of death or mechanical ventilation requirements at 14 days post-randomization. The secondary outcomes were similar in MPP and placebo groups. Conclusions: A 3-day course of MPP after the first week of disease onset did not prevent respiratory deterioration in hospitalized COVID-19 patients with an inflammatory phenotype who did not require oxygen.

The prognostic value of blood pressure control delay in newly diagnosed hypertensive patients.

OBJECTIVE: Various studies have suggested that a delay in the time between diagnosing hypertension and its correct control (D-C, diagnostic-control time) is linked to a worse prognosis. The aim of this study was to examine the relationship between D-C time and all-cause mortality, or the incidence of cardiovascular events, in patients more than 60 years newly diagnosed with hypertension. METHODS: This is a longitudinal, retrospective, population study employing data gathered from the electronic medical records of patients recently diagnosed with hypertension in 45 primary healthcare centres located in Barcelona (Catalonia). A multivariable logistic regression and Cox regression models were constructed. Goodness-of-fit was assessed through the Hosmer & Lemeshow test. RESULTS: A total of 18 721 newly diagnosed hypertensive patients were included between 2007 and 2012. The follow-up lasted until October 2015, or the appearance of a cardiovascular event or death because of any cause. The median D-C time was 49 days and its distribution by tertiles was the following: 29 days or less, 30-124 days, and at least 125 days. Higher hypertensive status, obesity, diabetes mellitus, and male sex were independently associated with longer D-C time (≥125 days). At 5.4 years follow-up, patients with longer D-C times presented statistically significant greater incidence of all-cause mortality. CONCLUSION: A delay in blood pressure control is significantly associated with an increase in the rate of all-cause mortality.

Use of high resolution dual-energy x-ray absorptiometry-region free analysis (DXA-RFA) to detect local periprosthetic bone remodeling events.

Dual-energy x-ray absorptiometry (DXA) is the gold standard method for measuring periprosthetic bone remodeling, but relies on a region of interest (ROI) analysis approach. While this addresses issues of anatomic variability, it is insensitive to bone remodeling events at the sub-ROI level. We have validated a high-spatial resolution tool, termed DXA-region free analysis (DXA-RFA) that uses advanced image processing approaches to allow quantitation of bone mineral density (BMD) at the individual pixel (data-point) level. Here we compared the resolution of bone remodeling measurements made around a stemless femoral prosthesis in 18 subjects over 24 months using ROI-based analysis versus that made using DXA-RFA. Using the ROI approach the regional pattern of BMD change varied by region, with greatest loss in ROI5 (20%, p < 0.001), and largest gain in ROI4 (6%, p < 0.05). Analysis using DXA-RFA showed a focal zone of increased BMD localized to the prosthesis-bone interface (30-40%, p < 0.001) that was not resolved using conventional DXA analysis. The 20% bone loss observed in ROI5 with conventional DXA was resolved to a focal area adjacent to the cut surface of the infero-medial femoral neck (up to 40%, p < 0.0001). DXA-RFA enables high resolution analysis of DXA datasets without the limitations incurred using ROI-based approaches.

High-spatial-resolution bone densitometry with dual-energy X-ray absorptiometric region-free analysis.

PURPOSE: To outline the conceptual development of dual-energy absorptiometric (DXA) region-free analysis, quantify its precision, and evaluate its application to quantify the change in longitudinal femoral periprosthetic bone mineral density (BMD) in patients during the 12 months after total hip arthroplasty. MATERIALS AND METHODS: All subjects had undergone total hip arthroplasty for idiopathic arthritis, and the scans were collected as part of previous ethically approved studies (1998-2005) for which informed consent was provided. Contemporary image processing approaches were used to develop a region of interest-free DXA analysis method with increased spatial resolution for assessment of proximal femoral BMD. The method was calibrated, and its accuracy relative to a proprietary algorithm was assessed by using a hip phantom. The precision of the method was examined by using repeat DXA acquisitions in 29 patients, and its ability to allow spatial resolution of localized periprosthetic BMD change at the hip was assessed in an independent group of 19 patients who were measured throughout a 12-month period. Differences were evaluated with t tests (P < .05). RESULTS: The method allowed spatial resolution of more than 10 000 individual BMD data points on a typical archived prosthetic hip scan. The median data point-level error of the method after calibration was -1.9% (interquartile range, -7.2% to 3.5%) relative to a proprietary algorithm. The median data point-level precision, expressed as a coefficient of variation, was 1.4% (interquartile range, 1.2%-1.6%). Evaluation of BMD change in a model of periprosthetic bone loss demonstrated large but highly focal changes in BMD that would not be resolved by using traditional region of interest-based analysis approaches. CONCLUSION: The proposed approach provides a quantitative, precise method for extracting high-spatial-resolution BMD data from existing DXA datasets without the limitations imposed by region of interest-based analysis.

Soft thresholding for medical image segmentation.

A new soft thresholding method is presented. The method is based on relating each pixel in the image to the different regions via a membership function, rather than through hard decisions. The membership function of each of the regions is derived from the histogram of the image. As a consequence, each pixel will belong to different regions with a different level of membership. This feature is exploited through spatial processing to make the thresholding robust to noisy environments.

A Log-Euclidean polyaffine registration for articulated structures in medical images.

In this paper we generalize the Log-Euclidean polyaffine registration framework of Arsigny et al. to deal with articulated structures. This framework has very useful properties as it guarantees the invertibility of smooth geometric transformations. In articulated registration a skeleton model is defined for rigid structures such as bones. The final transformation is affine for the bones and elastic for other tissues in the image. We extend the Arsigny el al.'s method to deal with locally-affine registration of pairs of wires. This enables the possibility of using this registration framework to deal with articulated structures. In this context, the design of the weighting functions, which merge the affine transformations defined for each pair of wires, has a great impact not only on the final result of the registration algorithm, but also on the invertibility of the global elastic transformation. Several experiments, using both synthetic images and hand radiographs, are also presented.

Group-Slicer: a collaborative extension of 3D-Slicer.

In this paper, we describe a first step towards a collaborative extension of the well-known 3D-Slicer; this platform is nowadays used as a standalone tool for both surgical planning and medical intervention. We show how this tool can be easily modified to make it collaborative so that it may constitute an integrated environment for expertise exchange as well as a useful tool for academic purposes.

A computational TW3 classifier for skeletal maturity assessment. A Computing with Words approach.

This paper proposes a fuzzy methodology to translate the natural language descriptions of the TW3 method for bone age assessment into an automatic classifier. The classifier is built upon a modified version of a fuzzy ID3 decision tree. No large data records are needed to train the classifier, i.e., to find out the classification rules, since the classifier is built upon rules given by the TW3 method. Only small data records are needed to fine-tune the fuzzy sets used to implement the rulebase.