Abstract:In this paper we evaluate the accuracy of warping of neuro-images using brain deformation predicted by means of a patient-specific biomechanical model against registration using a BSpline-based free form deformation algorithm. Unlike the Bspline algorithm, biomechanics-based registration does not require an intra-operative MR image which is very expensive and cumbersome to acquire. Only sparse intra-operative data on the brain surface is sufficient to compute deformation for the whole brain. In this contributi… Show more
“…The efficiency and effectiveness of this method has been verified through application in the studies on computation of brain deformation for neuroimage registration (Joldes et al, 2009b; Wittek et al, 2010). Although no commonly accepted specific guidelines regarding the required quality of hexahedral meshes in biomechanics are available, several authors have formulated their experience-based recommendations (Ito et al, 2009; Mostayed et al, 2013; Shepherd and Johnson, 2009; Yang and King, 2011). Following Ito et al (2009), Shepherd and Johnson (2009) and Yang and King (2011), we used element Jacobian and warpage to assess mesh quality.…”
Section: Methodsmentioning
confidence: 99%
“…This ensures plausibility and robustness of the predicted deformations. In particular, patient-specific biomechanical modelling has been successfully used in numerous studies on computing the brain deformations for neuroimage registration (Garlapati et al, 2014; Hu et al, 2007; Ji et al, 2009; Mostayed et al, 2013; Wittek et al, 2010; Xu and Nowinski, 2001). …”
Section: Introductionmentioning
confidence: 99%
“…Challenges to overcome when applying biomechanical modelling for medical image registration include quick and reliable generation of patient-specific computational models, automatic segmentation of radiographic images and efficient solution of the models (Miller, 2011; Miller et al, 2010; Mostayed et al, 2013). To facilitate rapid generation of patient-specific biomechanical models for whole-body CT image registration, we abandon time-consuming image segmentation that divides the problem domain into non-overlapping constituents with different material properties.…”
Whole-body computed tomography (CT) image registration is important for cancer diagnosis, therapy planning and treatment. Such registration requires accounting for large differences between source and target images caused by deformations of soft organs/tissues and articulated motion of skeletal structures. The registration algorithms relying solely on image processing methods exhibit deficiencies in accounting for such deformations and motion. We propose to predict the deformations and movements of body organs/tissues and skeletal structures for whole-body CT image registration using patient-specific non-linear biomechanical modelling. Unlike the conventional biomechanical modelling, our approach for building the biomechanical models does not require time-consuming segmentation of CT scans to divide the whole body into non-overlapping constituents with different material properties. Instead, a Fuzzy C-Means (FCM) algorithm is used for tissue classification to assign the constitutive properties automatically at integration points of the computation grid. We use only very simple segmentation of the spine when determining vertebrae displacements to define loading for biomechanical models. We demonstrate the feasibility and accuracy of our approach on CT images of seven patients suffering from cancer and aortic disease. The results confirm that accurate whole-body CT image registration can be achieved using a patient-specific non-linear biomechanical model constructed without time-consuming segmentation of the whole-body images.
“…The efficiency and effectiveness of this method has been verified through application in the studies on computation of brain deformation for neuroimage registration (Joldes et al, 2009b; Wittek et al, 2010). Although no commonly accepted specific guidelines regarding the required quality of hexahedral meshes in biomechanics are available, several authors have formulated their experience-based recommendations (Ito et al, 2009; Mostayed et al, 2013; Shepherd and Johnson, 2009; Yang and King, 2011). Following Ito et al (2009), Shepherd and Johnson (2009) and Yang and King (2011), we used element Jacobian and warpage to assess mesh quality.…”
Section: Methodsmentioning
confidence: 99%
“…This ensures plausibility and robustness of the predicted deformations. In particular, patient-specific biomechanical modelling has been successfully used in numerous studies on computing the brain deformations for neuroimage registration (Garlapati et al, 2014; Hu et al, 2007; Ji et al, 2009; Mostayed et al, 2013; Wittek et al, 2010; Xu and Nowinski, 2001). …”
Section: Introductionmentioning
confidence: 99%
“…Challenges to overcome when applying biomechanical modelling for medical image registration include quick and reliable generation of patient-specific computational models, automatic segmentation of radiographic images and efficient solution of the models (Miller, 2011; Miller et al, 2010; Mostayed et al, 2013). To facilitate rapid generation of patient-specific biomechanical models for whole-body CT image registration, we abandon time-consuming image segmentation that divides the problem domain into non-overlapping constituents with different material properties.…”
Whole-body computed tomography (CT) image registration is important for cancer diagnosis, therapy planning and treatment. Such registration requires accounting for large differences between source and target images caused by deformations of soft organs/tissues and articulated motion of skeletal structures. The registration algorithms relying solely on image processing methods exhibit deficiencies in accounting for such deformations and motion. We propose to predict the deformations and movements of body organs/tissues and skeletal structures for whole-body CT image registration using patient-specific non-linear biomechanical modelling. Unlike the conventional biomechanical modelling, our approach for building the biomechanical models does not require time-consuming segmentation of CT scans to divide the whole body into non-overlapping constituents with different material properties. Instead, a Fuzzy C-Means (FCM) algorithm is used for tissue classification to assign the constitutive properties automatically at integration points of the computation grid. We use only very simple segmentation of the spine when determining vertebrae displacements to define loading for biomechanical models. We demonstrate the feasibility and accuracy of our approach on CT images of seven patients suffering from cancer and aortic disease. The results confirm that accurate whole-body CT image registration can be achieved using a patient-specific non-linear biomechanical model constructed without time-consuming segmentation of the whole-body images.
“…The system will create an augmented reality visualisation of the intra-operative configuration of the patient’s brain merged with high resolution pre-operative imaging data, including diffusion tensor imaging (DTI) and functional MR imaging (fMRI), in order to better localise the tumour and critical healthy tissues. We accomplish this by registering high quality pre-operative neuroimages onto the current, intra-operative configuration of the patient’s brain; however, we do not use an intra-operative image as a target (2, 3)(Fig. 1).…”
To enhance neuro-navigation, high quality pre-operative images must be registered onto intra-operative configuration of the brain. Therefore evaluation of the degree to which structures may remain misaligned after registration is critically important. We consider two Hausdorff Distance (HD)-based evaluation approaches: the edge-based HD (EBHD) metric and the Robust HD (RHD) metric as well as various commonly used intensity-based similarity metrics such as Mutual Information (MI), Normalized Mutual Information (NMI), Entropy Correlation Coefficient (ECC), Kullback-Leibler distance (KLD) and Correlation Ratio (CR). We conducted the evaluation by applying known deformations to simple sample images and real cases of brain shift. We conclude that the intensity-based similarity metrics such as MI, NMI, ECC, KLD and CR do not correlate well with actual alignment errors, and hence are not useful for assessing misalignment. On the contrary, the EBHD and the RHD metrics correlated well with actual alignment errors; however, they have been found to underestimate the actual misalignment. We also note that it is beneficial to present HD results as a percentile-HD curve rather than a single number such as the 95-percentile HD. Percentile-HD curves present full range of alignment errors and also facilitate the comparison of results obtained using different approaches. Furthermore, the qualities that should be possessed by an ideal evaluation metric were highlighted. Future studies could focus on developing such an evaluation metric.
“…In the past nonrigid registration of CTs (and other radiographic image modalities) relied solely on image processing methods that predict the deformation field within the human body organs/tissues without taking into account the principles of mechanics governing deformations of such organs/tissues [2,4]. Such methods do not ensure plausibility of the predicted deformations and their accuracy tends to decrease when the differences between the source and target images become large due to articulated motion of the body segments and soft tissue deformations [4][5][6]. Therefore, biomechanical models, in which predicting the organs/tissue deformation is treated as a computational problem of solid mechanics, have been introduced [7][8][9][10][11].…”
Biomechanical modeling methods can be used to predict deformations for medical image registration and particularly, they are very effective for whole-body computed tomography (CT) image registration because differences between the source and target images caused by complex articulated motions and soft tissues deformations are very large. The biomechanics-based image registration method needs to deform the source images using the deformation field predicted by finite element models (FEMs). In practice, the global and local coordinate systems are used in finite element analysis. This involves the transformation of coordinates from the global coordinate system to the local coordinate system when calculating the global coordinates of image voxels for warping images. In this paper, we present an efficient numerical inverse isoparametric mapping algorithm to calculate the local coordinates of arbitrary points within the eight-noded hexahedral finite element. Verification of the algorithm for a nonparallelepiped hexahedral element confirms its accuracy, fast convergence, and efficiency. The algorithm's application in warping of the whole-body CT using the deformation field predicted by means of a biomechanical FEM confirms its reliability in the context of whole-body CT registration.
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