Propagation of measurement noise through backprojection reconstruction in electrical impedance tomography

A framework to analyze the propagation of measurement noise through backprojection reconstruction algorithms in electrical impedance tomography (EIT) is presented. Two measurement noise sources were considered: noise in the current drivers and in the voltage detectors. The influence of the acquisition system architecture (serial/semi-parallel) is also discussed. Three variants of backprojection reconstruction are studied: basic (unweighted), weighted and exponential backprojection. The results of error propagation theory have been compared with those obtained from simulated and experimental data. This comparison shows that the approach provides a good estimate of the reconstruction error variance. It is argued that the reconstruction error in EIT images obtained via backprojection can be approximately modeled as a spatially nonstationary Gaussian distribution. This methodology allows us to develop a spatial characterization of the reconstruction error in EIT images.Peer Reviewe

QuantiDOPA: A Quantification Software for Dopaminergic Neurotransmission SPECT

Quantification of neurotransmission Single-Photon Emission Computed Tomography (SPECT) studies of the dopaminergic system can be used to track, stage and facilitate early diagnosis of the disease. The aim of this study was to implement QuantiDOPA, a semi-automatic quantification software of application in clinical routine to reconstruct and quantify neurotransmission SPECT studies using radioligands which bind the dopamine transporter (DAT). To this end, a workflow oriented framework for the biomedical imaging (GIMIAS) was employed. QuantiDOPA allows the user to perform a semiautomatic quantification of striatal uptake by following three stages: reconstruction, normalization and quantification. QuantiDOPA is a useful tool for semi-automatic quantification inDAT SPECT imaging and it has revealed simple and flexibl

FocusDET: Herramienta multimodal para la localización del foco epileptógeno en la epilepsia farmacorresistente

Los pacientes epilépticos con crisis parciales complejas resistentes a tratamiento farmacológico son candidatos a la escisión de la región focal del cerebro que induce dichas crisis. La correcta localización del foco epileptógeno es esencial para considerar la cirugía como posible tratamiento. El objetivo de este trabajo es el desarrollo de una aplicación médica para la localización del foco epileptógeno a partir de datos multimodales. Para el desarrollo de esta nueva herramienta se utiliza GIMIAS, una plataforma de software para la implementación y prototipado de aplicaciones médicas. La nueva herramienta desarrollada, FocusDET, permite llevar a cabo la técnica SISCOM y el análisis de datos EEG-RM f ictal, de imágenes PET y de distintas modalidades de imagen de RM. FocusDET, gracias a su interfaz amigable y a su rapidez de procesamiento, puede ser adecuada para la rutina clínica

Propagation of measurement noise through backprojection reconstruction in electrical impedance tomography

A framework to analyze the propagation of measurement noise through backprojection reconstruction algorithms in electrical impedance tomography (EIT) is presented. Two measurement noise sources were considered: noise in the current drivers and in the voltage detectors. The influence of the acquisition system architecture (serial/semi-parallel) is also discussed. Three variants of backprojection reconstruction are studied: basic (unweighted), weighted and exponential backprojection. The results of error propagation theory have been compared with those obtained from simulated and experimental data. This comparison shows that the approach provides a good estimate of the reconstruction error variance. It is argued that the reconstruction error in EIT images obtained via backprojection can be approximately modeled as a spatially nonstationary Gaussian distribution. This methodology allows us to develop a spatial characterization of the reconstruction error in EIT images.Peer Reviewe

Deployment of self-expandable stents in aneurysmatic cerebral vessels: comparison of different computational approaches for interventional planning

In the last few years, there has been a growing focus on faster computational methods to support clinicians in planning stenting procedures. This study investigates the possibility of introducing computational approximations in modelling stent deployment in aneurysmatic cerebral vessels to achieve simulations compatible with the constraints of real clinical workflows. The release of a self-expandable stent in a simplified aneurysmatic vessel was modelled in four different initial positions. Six progressively simplified modelling approaches (based on Finite Element method and Fast Virtual Stenting – FVS) have been used. Comparing accuracy of the results, the final configuration of the stent is more affected by neglecting mechanical properties of materials (FVS) than by adopting 1D instead of 3D stent models. Nevertheless, the differences/nshowed are acceptable compared to those achieved by considering different stent initial positions. Regarding computational/ncosts, simulations involving 1D stent features are the only ones feasible in clinical context.This work was partially supported within the CENIT CDTEAM (2006–2009) and cvREMOD (2010–2012) projects funded by the Spanish MICINN-CDTI, and partly within the framework of the @neurIST Integrated Project (IST-2005-027703), which is cofinanced by the European Commission within the IST Program of Sixth Framework Program

Deployment of self-expandable stents in aneurysmatic cerebral vessels: comparison of different computational approaches for interventional planning

In the last few years, there has been a growing focus on faster computational methods to support clinicians in planning stenting procedures. This study investigates the possibility of introducing computational approximations in modelling stent deployment in aneurysmatic cerebral vessels to achieve simulations compatible with the constraints of real clinical workflows. The release of a self-expandable stent in a simplified aneurysmatic vessel was modelled in four different initial positions. Six progressively simplified modelling approaches (based on Finite Element method and Fast Virtual Stenting – FVS) have been used. Comparing accuracy of the results, the final configuration of the stent is more affected by neglecting mechanical properties of materials (FVS) than by adopting 1D instead of 3D stent models. Nevertheless, the differences/nshowed are acceptable compared to those achieved by considering different stent initial positions. Regarding computational/ncosts, simulations involving 1D stent features are the only ones feasible in clinical context.This work was partially supported within the CENIT CDTEAM (2006–2009) and cvREMOD (2010–2012) projects funded by the Spanish MICINN-CDTI, and partly within the framework of the @neurIST Integrated Project (IST-2005-027703), which is cofinanced by the European Commission within the IST Program of Sixth Framework Program

Cardiac motion estimation by joint alignment of tagged MRI sequences

Image registration has been proposed as an automatic method for recovering cardiac displacement fields from Tagged Magnetic Resonance Imaging (tMRI) sequences. Initially performed as a set of pairwise registrations, these techniques have evolved to the use of 3D+t deformation models, requiring metrics of joint image alignment (JA). However, only linear combinations of cost functions defined with respect to the first frame have been used. In this paper, we have applied k-Nearest Neighbors Graphs (kNNG) estimators of the -entropy (H ) to measure the joint similarity between frames, and to combine the information provided by different cardiac views in an unified metric. Experiments performed on six subjects showed a significantly higher accuracy (p < 0.05) with respect to a standard pairwise alignment (PA) approach in terms of mean positional error and variance with respect to manually placed landmarks. The developed method was used to study strains in patients with myocardial infarction, showing a consistency between strain, infarction location, and coronary occlusion. This paper also presents/nan interesting clinical application of graph-based metric estimators, showing their value for solving practical problems found in medical imaging

Patient-specific computational hemodynamics of intracranial aneurysms from 3D rotational angiography and CT angiography: an in vivo reproducibility study

Patient-specific simulations of the hemodynamics in intracranial aneurysms can be constructed by using image-based vascular models and CFD techniques. This work evaluates the impact of the choice of imaging technique on these simulationsThis work was partially supported by the @neurIST Integrated Project (cofinanced by the European Commission through contract no. IST-027703) and the CD-TEAM grant funded by the Spanish Ministry of Science and Innovation. Support from Philips Healthcare B.V. and ANSYS Europe Ltd is also acknowledged

The role of computational fluid dynamics in the management of unruptured intracranial aneurysms: a clinicians' view

Objective: The importance of hemodynamics in the etiopathogenesis of intracranial aneurysms (IAs) is widely accepted./nComputational fluid dynamics (CFD) is being used increasingly for hemodynamic predictions. However, alogn with the/ncontinuing development and validation of these tools, it is imperative to collect the opinion of the clinicians. Methods: A workshop/non CFD was conducted during the European Society of Minimally Invasive Neurological Therapy (ESMINT) Teaching Course,/nLisbon, Portugal. 36 delegates, mostly clinicians, performed supervised CFD analysis for an IA, using the @neuFuse software/ndeveloped within the European project @neurIST. Feedback on the workshop was collected and analyzed. The performance/nwas assessed on a scale of 1 to 4 and, compared with experts’ performance. Results: Current dilemmas in the management of/nunruptured IAs remained the most important motivating factor to attend the workshop and majority of participants showed/ninterest in participating in a multicentric trial. The participants achieved an average score of 2.52 (range 0–4) which was 63% (range 0–100%) of an expert user. Conclusions: Although participants showed a manifest interest in CFD, there was a clear lack of/nawareness concerning the role of hemodynamics in the etiopathogenesis of IAs and the use of CFD in this context. More efforts/ntherefore are required to enhance understanding of the clinicians in the subject.The authors would like to thank the European Commission,/nVI Framework Program, Priority 2, Information Society/nComputational Intelligence and Neuroscience 11/nTechnologies, a European Public Funded Organization,/nfor funding @neurIST Project (2) (www.aneurist.org) and/nallowing this study (Research Grant no. IST-FP6-027703). The funding was provided in the form of financial support/nto first two authors along with the arrangement of necessary/nresources to conduct the workshop

Automated Segmentation of Cerebral Vasculature with Aneurysms in 3DRA and TOF-MRA using Geodesic Active Regions: an Evaluation Study

Purpose: To evaluate the suitability of an improved version of an automatic segmentation method based on geodesic active regions (GAR) for segmenting cerebral vasculature with aneurysms from 3D X-ray reconstruc-/ntion angiography (3DRA) and time of °ight magnetic resonance angiography (TOF-MRA) images available in the clinical routine./nMethods: Three aspects of the GAR method have been improved: execution time, robustness to variability in imaging protocols and robustness to variability in image spatial resolutions. The improved GAR was retrospectively evaluated on images from patients containing intracranial aneurysms in the area of the Circle of Willis and imaged with two modalities: 3DRA and TOF-MRA. Images were obtained from two clinical centers, each using di®erent imaging equipment. Evaluation included qualitative and quantitative analyses of/nthe segmentation results on 20 images from 10 patients. The gold standard was built from 660 cross-sections (33 per image) of vessels and aneurysms, manually measured by interventional neuroradiologists. GAR has also been compared to an interactive segmentation method: iso-intensity surface extraction (ISE). In addition, since patients had been imaged with the two modalities, we performed an inter-modality agreement analysis with respect to both the manual measurements and each of the two segmentation methods. Results: Both GAR and ISE di®ered from the gold standard within acceptable limits compared to the imaging resolution. GAR (ISE, respectively) had an average accuracy of 0.20 (0.24) mm for 3DRA and 0.27 (0.30) mm for TOF-MRA, and had a repeatability of 0.05 (0.20) mm. Compared to ISE, GAR had a lower qualitative error in the vessel region and a lower quantitative error in the aneurysm region. The repeatability/nof GAR was superior to manual measurements and ISE. The inter-modality agreement was similar between GAR and the manual measurements. Conclusions: The improved GAR method outperformed ISE qualitatively as well as quantitatively and is suitable for segmenting 3DRA and TOF-MRA images from clinical routine.The authors would like to acknowledge J. Schneiders for providing part of the TOF-MRA imaging data. The authors would like to thank also A. G. Radaelli, M. Nieber, and X. Planes for the help in implementing some of the methods. This work was partially supported by the @neurIST Integrated Project (co-financed by the European Commission through Contract No. IST-027703), the CDTI CENIT-CDTEAM grant funded by the Spanish Ministry of Science and Innovation (MICINN-CDTI), the AGAUR-FI fellowship from Generalitat de Catalunya, and Philips Healthcare (Best, The Netherlands)