Auer, D. P. | Search bioRxiv

bioRxiv2020

Coordinate Density Analysis of neuroimaging studies

Functional MRI and voxel-based morphometry (VBM) are important approaches to testing hypotheses in neuroscience, helping us to understand neurological disease, and brain function and development. However, they are technically challenging with no one optimal generalisable method, and the multiple popular techniques have been shown to produce different results. Furthermore, results may be sensitive to settings, such as smoothing or statistical thresholding, that can be difficult to optimise per hypothesis. It is useful, therefore, to be able to meta-analyse published results from such studies that tested a similar hypothesis potentially using different analysis methods, scanners, and protocols as well as different subjects. Coordinate based meta-analysis (CBMA) offers this using only commonly reported summary results. It is the aim of CBMA to find those results that indicate replicable effects across studies. However, just like the multiple analysis methods offered for neuroimaging, there are now multiple CBMA algorithms each with specific features and empirical parameters/assumptions. Results derived from CBMA are inevitably conditional on the algorithm used, so conclusions are clearer when the analysis approach is easy to understand. With this in mind a new CBMA method (Analysis of Brain Coordinates; ABC) is presented, with the aim of being easy to interpret by eliminating empirical assumptions where possible and by relating statistical thresholding directly to replication of effect.

neuroscience↗

bioRxiv2020

Ensemble learning for robust knee cartilage segmentation: data from the osteoarthritis initiative.

PurposeTo evaluate the performance of an ensemble learning approach for fully automated cartilage segmentation on knee magnetic resonance images of patients with osteoarthritis. Materials and MethodsThis retrospective study of 88 participants with knee osteoarthritis involved the study of three-dimensional (3D) double echo steady state (DESS) MR imaging volumes with manual segmentations for 6 different compartments of cartilage (Data available from the Osteoarthritis Initiative). We propose ensemble learning to boost the sensitivity of our deep learning method by combining predictions from two models, a U-Net for the segmentation of two labels (cartilage vs background) and a multi-label U-Net for specific cartilage compartments. Segmentation accuracy is evaluated using Dice coefficient, while volumetric measures and Bland Altman plots provide complimentary information when assessing segmentation results. ResultsOur model showed excellent accuracy for all 6 cartilage locations: femoral 0.88, medial tibial 0.84, lateral tibial 0.88, patellar 0.85, medial meniscal 0.85 and lateral meniscal 0.90. The average volume correlation was 0.988, overestimating volume by 9% {+/-} 14% over all compartments. Simple post processing creates a single 3D connected component per compartment resulting in higher anatomical face validity. ConclusionOur model produces automated segmentation with high Dice coefficients when compared to expert manual annotations and leads to the recovery of missing labels in the manual annotations, while also creating smoother, more realistic boundaries avoiding slice discontinuity artifacts present in the manual annotations. Key ResultsO_LICombining a 2-label U-Net (cartilage vs background) with a multi-class U-Net for segmentation of cartilage compartment boosts the accuracy of our deep learning model leading to the recovery of missing annotations in the manual dataset. C_LIO_LIAutomatically generated segmentations have high Dice coefficients (0.85-0.90) and reduce inter-slice discontinuity artefact caused by slice wise delineation. C_LIO_LIModel refinement yields more anatomically plausible segmentations where each cartilage label is composed of only a single 3D region of interest. C_LI

pathology↗