Longer life expectancies lead to increases in the prevalence of age-associated illnesses. The num... more Longer life expectancies lead to increases in the prevalence of age-associated illnesses. The number of Australians with dementia is predicted to rise, from 234,000 in 2009 to over 1 million by 2050, as a result of the increased prevalence of Alzheimer's disease (AD), the leading cause of dementia in the elderly. Early diagnosis of AD will become more important as disease-modifying therapies emerge within the next decade. Advances in molecular neuroimaging with amyloid-β-specific radioligands for positron emission tomography, aided by magnetic resonance imaging techniques, allow detection of AD years before symptoms of dementia develop. Longitudinal prospective studies, such as the Australian Imaging Biomarkers and Lifestyle (AIBL) study of ageing, will determine the sensitivity and specificity of these analysis techniques for diagnosing AD and predicting cognitive decline.
Society of Photo Optical Instrumentation Engineers Conference Series, Feb 1, 2009
Despite the increasing adoption of other imaging modalities, ultrasound guidance is widely used f... more Despite the increasing adoption of other imaging modalities, ultrasound guidance is widely used for surgical procedures and clinical imaging due to its low cost, non-invasiveness, and real-time visual feedback. Many ultrasound-guided procedures require extensive training and where possible training on simulations should be preferred over patients. Computational resources for existing approaches to ultrasound simulation are usually limited by real-time requirements. Unlike previous approaches we simulate freehand ultrasound images from CT data on the Graphics Processing Unit (GPU). We build upon the method proposed by Wein et al. for estimating ultrasound reflection properties of tissue and modify it to a computationally more efficient form. In addition to previous approaches, we also estimate ultrasound absorption properties from CT data. Using NVIDIA's "Compute Unified Device Architecture" (CUDA), we provide a physically plausible simulation of ultrasound reflection, shadowing artifacts, speckle noise and radial blurring. The same algorithm can be used for simulating either linear or radial imaging, and all parameters of the simulated probe are interactively configurable at runtime, including ultrasound frequency and intensity as well as field geometry. With current hardware we are able to achieve an image width of up to 1023 pixels from raw CT data in real-time, without any pre-processing and without any loss of information from the CT image other than from interpolation of the input data. Visual comparison to real ultrasound images indicates satisfactory results.
2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2015
The main challenge in prostate cancer radiotherapy is to deliver the prescribed dose to the clini... more The main challenge in prostate cancer radiotherapy is to deliver the prescribed dose to the clinical target while minimizing the dose to the neighboring organs at risk and thus avoiding subsequent toxicity-related events. With the aim of improving toxicity prediction following prostate cancer radiotherapy, the goal of our work is to propose a new predictive variable computed with independent component analysis to predict late rectal toxicity, and to compare its performance to other models (logistic regression, normal tissue complication probability model and recent principal component analysis approach). Clinical data and dose-volume histograms were collected from 216 patients having received 3D conformal radiation for prostate cancer with at least two years of follow-up. Independent component analysis was trained to predict the risk of 3-year rectal bleeding Grade ≥ 2. The performance of all the models was assessed by computing the area under the receiving operating characteristic curve. Clinical parameters combined with the new variable were found to be predictors of rectal bleeding. The mean area under the receiving operating curve for our proposed approach was 0:75. The AUC values for the logistic regression, the Lyman-Kutcher-Burman model and the recent principal component analysis approach were 0:62, 0:53 and 0:62, respectively. Our proposed new variable may be an useful new tool in predicting late rectal toxicity. It appears as a strong predictive variable to improve classical models.
2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2015
Adaptive radiation therapy (ART) is based on the optimization of the treatment plan during the tr... more Adaptive radiation therapy (ART) is based on the optimization of the treatment plan during the treatment delivery to compensate for anatomical deformations. Deformable Image Registration (DIR) then constitutes a key step in order to analyze the huge amount of daily or weekly images to provide clinically usefull information. Two main applications of DIR have been developped in ART: delineation propagation and dose accumulation. If delineation propagation is well validated and transfered in the clinic, some challenges remain to address for dose accumulation. In this paper, we review the recent developments of DIR in ART, particularly in prostate and head-and-neck (H&N), with a focus on their evaluation.
In Image-Guided Radiation Therapy of prostate cancer, the CBCT scan acquired at each treatment fr... more In Image-Guided Radiation Therapy of prostate cancer, the CBCT scan acquired at each treatment fraction could be used to estimate a cumula-tive dose distribution thanks to non-rigid registration. However, this cumulative dose estimation is highly sensitive to non-rigid registration errors. For this rea-son, validation of the registration algorithm with organ overlap measures or visual assessment is not sufficient. In this paper, we describe the construction of a nu-merical phantom based on a finite element model of the prostate and the neighbor organs which can be used to assess the non-rigid registration accuracy. Prelimi-nary results show the potential of this phantom to better characterize registration algorithms than traditional Dice score.
Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention, 2008
Accurate cortical thickness estimation in-vivo is important for the study of many neurodegenerati... more Accurate cortical thickness estimation in-vivo is important for the study of many neurodegenerative diseases. When using magnetic resonance images (MRI), accuracy may be hampered by artifacts such as partial volume (PV) as the cortex spans only a few voxels. In zones of opposed sulcal banks (tight sulci) the measurement can be even more difficult. The aim of this work is to propose a voxel-based cortical thickness estimation method from MR by integrating a mechanism for correcting sulci delineation after an improved partial volume classification. First, an efficient and accurate framework was developed to enhance partial volume classification with structural information. Then, the correction of sulci delineation is performed after a homotopic thinning of a cost function image. Integrated to our voxel-based cortical thickness estimation pipeline, the overall method showed a better estimate of thickness and a high reproducibility on real data (R2 > 0.9). A quantitative analysis on ...
IEEE Journal of Biomedical and Health Informatics, 2014
The understanding of dose/side-effects relationships in prostate cancer radiotherapy is crucial t... more The understanding of dose/side-effects relationships in prostate cancer radiotherapy is crucial to define appropriate individual's constraints at the therapy planning. Most of the existing methods to predict side effects do not fully exploit the rich spatial information conveyed by the three-dimensional planned dose distributions. We propose a new classification method for three-dimensional individuals' doses, based on a new semi-nonnegative ICA algorithm to identify patients at risk of presenting rectal bleeding from a population treated for prostate cancer. The method firstly determines two bases of vectors from the population data (the first basis corresponds to rectal bleeding patients and the second one characterizes the non rectal bleeding patients). The classification is then achieved by projecting a new three-dimensional individual planned dose onto both subspaces spanned by the two bases. A given patient is thus classified by calculating its distance to the two subspaces. The results, obtained on a cohort of 87 patients (at two years follow-up) treated with radiotherapy, showed high performance in terms of sensitivity and specificity.
2011 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, 2011
ABSTRACT In prostate cancer radiotherapy, accurate segmentation of prostate and organs at risk in... more ABSTRACT In prostate cancer radiotherapy, accurate segmentation of prostate and organs at risk in planning CT and follow-up CBCT images is an essential part of the therapy planning and optimization. Automatic segmentation is challenging because of the poor constrast in soft tissues. Although atlas-based approaches may provide a priori structural information by propagating manual expert delineations to a new individual space, the interindividual variability and registration errors can introduce bias in the results. Multi-atlas approaches can partly overcome some of these difficulties by selecting the most similar atlases among a large data base but the definition of similarity measure between the available atlases and the query individual has still to be addressed. The purpose of this paper is the evaluation of different strategies to simultaneously segment prostate, bladder and rectum from CT images, by selecting the most similar atlases from a prebuilt 24 atlas subset. Three similarity measures were considered: cross-correlation (CC), sum of squared differences (SSD) and mutual information (MI). Experiments on atlas ranking, selection strategies and fusion decision rules were carried out. Propagation of labels using the diffeomorphic demons non-rigid registration were used and the results were compared with manual delineations. Results suggest that CC and SSD are the best predictors for selecting similar atlases and that a vote decision rule is better suited to cope with large variabilities.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2005
A two-step method to determine the seed parameters for the planning of peripheral intravascular b... more A two-step method to determine the seed parameters for the planning of peripheral intravascular brachytherapy, which took the actual vessel geometry into consideration, was developed. Firstly, the characteristics of the vessel geometry was obtained by using active navigation; Then a method combined genetic algorithm with BFGS algorithm was applied to optimize the number of seeds, and the parameters associated with each seed such as the position, and the dwell time. Application of the method to a phantom model and three animal models of stenosis shows that promising result could be obtained, and the planning of peripheral intravascular brachytherapy should take actual vessel geometry into consideration.
Medical Imaging 2002: Visualization, Image-Guided Procedures, and Display, 2002
ABSTRACT In most planning procedures of intravascular brachytherapy the lesion path is assumed to... more ABSTRACT In most planning procedures of intravascular brachytherapy the lesion path is assumed to be a straight line and the dose distribution is essentially specified with respect to the seed. We propose a new approach for the planning of peripheral intravascular brachytherapy based on the characterization of the vessel by virtual exploratory navigation. In order to make the procedure more secure and reliable, the dosimetry planning takes actually account of the geometrical characteristics of the vessel (length, diameter, curvature). Virtual exploratory navigation constitutes the basis of optimal path planning (centering, positioning, trajectory definition) and dosimetry planning for high dose rate brachytherapy. In order to estimate the post-angioplasty vessel centerline and inner surface, a simplified simulation of the transluminal angioplasty procedure is performed using a single pre-angioplasty CT data set. Thanks to the dose rate computation performed in the whole CT volume, the irradiation of the surrounding anatomical structures can be anticipated. A virtual angioscopy like process is used to check the homogeneity of the dose distribution in the vessel wall. Preliminary results obtained from a phantom model and from an animal model of stenosis are reported.
Medical Imaging 2002: Physiology and Function from Multidimensional Images, 2002
ABSTRACT The characterization of the vessel and its lesion is part and parcel of any patient spec... more ABSTRACT The characterization of the vessel and its lesion is part and parcel of any patient specific planning of endovascular interventions. Thanks to the virtual exploration of a CT volume image acquired under clinical routine conditions we provide the practitioner with the primary elements to plan the intervention. Thus, the curve representing the evolution of the area of the lumen cross-section along the vessel centerline as well as the localization of the stenosis are derived from the virtual exploratory navigation. Due to the lack of reference in medical applications, an animal model of stenosis has been created and used to evaluate our approach. The stenosis characterization through virtual exploratory navigation has been applied to a set of ten sheep iliac arteries and compared with the characterization performed from classical reformatted CT slices and histological cross-sections. The validation of this virtual navigation based analysis is essential to the elaboration of planning systems aimed at the prevention of restenosis phenomena in transluminal angioplasty (accurate localization and covering of the lesion), as well as the treatment of the restenosis phenomena by intravascular brachytherapy (taking the vessel geometry into account).
2013 IEEE 10th International Symposium on Biomedical Imaging, 2013
ABSTRACT Although accurate delineations of the prostate on computed tomography (CT) images are re... more ABSTRACT Although accurate delineations of the prostate on computed tomography (CT) images are required for the planning in prostate cancer radiotherapy, these images do not provide the reliable soft tissue contrast. On the contrary, magnetic resonance (MR) images offer the possibility to better delineate both the tumor and healthy prostate tissues. Because CT is still used during the planning, MRICT image registration is an essential step to improve the targeting. In this paper, we propose a new framework to propagate the MRI prostate delineation to the CT-scan based on a robust contour matching approach. Prostate boundaries in CT are characterized with several multi-scale features and detected with a support vector machine (SVM) classifier. A new cost function for aligning the MRI delineation to the detected contours was developed. We evaluated the proposed approach on 11 manually aligned and delineated MR and CT images. The method outperformed the widely used mutual information (MI) and demonstrated the drawbacks of this metric for this application.
2009 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, 2009
ABSTRACT Polygon meshes representing the cerebral cortex have been increas-ingly used for visuali... more ABSTRACT Polygon meshes representing the cerebral cortex have been increas-ingly used for visualisation and analysis in biomedical imaging in recent years. Due to the highly convoluted structure of the cere-bral cortex, a number of methods have been proposed for inflating ...
Medical Imaging 2007: Ultrasonic Imaging and Signal Processing, 2007
Ultrasound (US) is one of the most used imaging modalities today as it is cheap, reliable, safe a... more Ultrasound (US) is one of the most used imaging modalities today as it is cheap, reliable, safe and widely available. There are a number of issues with US images in general. Besides reflections which is the basis of ultrasonic imaging, other phenomena such as diffraction, refraction, attenuation, dispersion and scattering appear when ultrasound propagates through different tissues. The generated images
Longer life expectancies lead to increases in the prevalence of age-associated illnesses. The num... more Longer life expectancies lead to increases in the prevalence of age-associated illnesses. The number of Australians with dementia is predicted to rise, from 234,000 in 2009 to over 1 million by 2050, as a result of the increased prevalence of Alzheimer's disease (AD), the leading cause of dementia in the elderly. Early diagnosis of AD will become more important as disease-modifying therapies emerge within the next decade. Advances in molecular neuroimaging with amyloid-β-specific radioligands for positron emission tomography, aided by magnetic resonance imaging techniques, allow detection of AD years before symptoms of dementia develop. Longitudinal prospective studies, such as the Australian Imaging Biomarkers and Lifestyle (AIBL) study of ageing, will determine the sensitivity and specificity of these analysis techniques for diagnosing AD and predicting cognitive decline.
Society of Photo Optical Instrumentation Engineers Conference Series, Feb 1, 2009
Despite the increasing adoption of other imaging modalities, ultrasound guidance is widely used f... more Despite the increasing adoption of other imaging modalities, ultrasound guidance is widely used for surgical procedures and clinical imaging due to its low cost, non-invasiveness, and real-time visual feedback. Many ultrasound-guided procedures require extensive training and where possible training on simulations should be preferred over patients. Computational resources for existing approaches to ultrasound simulation are usually limited by real-time requirements. Unlike previous approaches we simulate freehand ultrasound images from CT data on the Graphics Processing Unit (GPU). We build upon the method proposed by Wein et al. for estimating ultrasound reflection properties of tissue and modify it to a computationally more efficient form. In addition to previous approaches, we also estimate ultrasound absorption properties from CT data. Using NVIDIA's "Compute Unified Device Architecture" (CUDA), we provide a physically plausible simulation of ultrasound reflection, shadowing artifacts, speckle noise and radial blurring. The same algorithm can be used for simulating either linear or radial imaging, and all parameters of the simulated probe are interactively configurable at runtime, including ultrasound frequency and intensity as well as field geometry. With current hardware we are able to achieve an image width of up to 1023 pixels from raw CT data in real-time, without any pre-processing and without any loss of information from the CT image other than from interpolation of the input data. Visual comparison to real ultrasound images indicates satisfactory results.
2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2015
The main challenge in prostate cancer radiotherapy is to deliver the prescribed dose to the clini... more The main challenge in prostate cancer radiotherapy is to deliver the prescribed dose to the clinical target while minimizing the dose to the neighboring organs at risk and thus avoiding subsequent toxicity-related events. With the aim of improving toxicity prediction following prostate cancer radiotherapy, the goal of our work is to propose a new predictive variable computed with independent component analysis to predict late rectal toxicity, and to compare its performance to other models (logistic regression, normal tissue complication probability model and recent principal component analysis approach). Clinical data and dose-volume histograms were collected from 216 patients having received 3D conformal radiation for prostate cancer with at least two years of follow-up. Independent component analysis was trained to predict the risk of 3-year rectal bleeding Grade ≥ 2. The performance of all the models was assessed by computing the area under the receiving operating characteristic curve. Clinical parameters combined with the new variable were found to be predictors of rectal bleeding. The mean area under the receiving operating curve for our proposed approach was 0:75. The AUC values for the logistic regression, the Lyman-Kutcher-Burman model and the recent principal component analysis approach were 0:62, 0:53 and 0:62, respectively. Our proposed new variable may be an useful new tool in predicting late rectal toxicity. It appears as a strong predictive variable to improve classical models.
2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2015
Adaptive radiation therapy (ART) is based on the optimization of the treatment plan during the tr... more Adaptive radiation therapy (ART) is based on the optimization of the treatment plan during the treatment delivery to compensate for anatomical deformations. Deformable Image Registration (DIR) then constitutes a key step in order to analyze the huge amount of daily or weekly images to provide clinically usefull information. Two main applications of DIR have been developped in ART: delineation propagation and dose accumulation. If delineation propagation is well validated and transfered in the clinic, some challenges remain to address for dose accumulation. In this paper, we review the recent developments of DIR in ART, particularly in prostate and head-and-neck (H&N), with a focus on their evaluation.
In Image-Guided Radiation Therapy of prostate cancer, the CBCT scan acquired at each treatment fr... more In Image-Guided Radiation Therapy of prostate cancer, the CBCT scan acquired at each treatment fraction could be used to estimate a cumula-tive dose distribution thanks to non-rigid registration. However, this cumulative dose estimation is highly sensitive to non-rigid registration errors. For this rea-son, validation of the registration algorithm with organ overlap measures or visual assessment is not sufficient. In this paper, we describe the construction of a nu-merical phantom based on a finite element model of the prostate and the neighbor organs which can be used to assess the non-rigid registration accuracy. Prelimi-nary results show the potential of this phantom to better characterize registration algorithms than traditional Dice score.
Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention, 2008
Accurate cortical thickness estimation in-vivo is important for the study of many neurodegenerati... more Accurate cortical thickness estimation in-vivo is important for the study of many neurodegenerative diseases. When using magnetic resonance images (MRI), accuracy may be hampered by artifacts such as partial volume (PV) as the cortex spans only a few voxels. In zones of opposed sulcal banks (tight sulci) the measurement can be even more difficult. The aim of this work is to propose a voxel-based cortical thickness estimation method from MR by integrating a mechanism for correcting sulci delineation after an improved partial volume classification. First, an efficient and accurate framework was developed to enhance partial volume classification with structural information. Then, the correction of sulci delineation is performed after a homotopic thinning of a cost function image. Integrated to our voxel-based cortical thickness estimation pipeline, the overall method showed a better estimate of thickness and a high reproducibility on real data (R2 > 0.9). A quantitative analysis on ...
IEEE Journal of Biomedical and Health Informatics, 2014
The understanding of dose/side-effects relationships in prostate cancer radiotherapy is crucial t... more The understanding of dose/side-effects relationships in prostate cancer radiotherapy is crucial to define appropriate individual's constraints at the therapy planning. Most of the existing methods to predict side effects do not fully exploit the rich spatial information conveyed by the three-dimensional planned dose distributions. We propose a new classification method for three-dimensional individuals' doses, based on a new semi-nonnegative ICA algorithm to identify patients at risk of presenting rectal bleeding from a population treated for prostate cancer. The method firstly determines two bases of vectors from the population data (the first basis corresponds to rectal bleeding patients and the second one characterizes the non rectal bleeding patients). The classification is then achieved by projecting a new three-dimensional individual planned dose onto both subspaces spanned by the two bases. A given patient is thus classified by calculating its distance to the two subspaces. The results, obtained on a cohort of 87 patients (at two years follow-up) treated with radiotherapy, showed high performance in terms of sensitivity and specificity.
2011 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, 2011
ABSTRACT In prostate cancer radiotherapy, accurate segmentation of prostate and organs at risk in... more ABSTRACT In prostate cancer radiotherapy, accurate segmentation of prostate and organs at risk in planning CT and follow-up CBCT images is an essential part of the therapy planning and optimization. Automatic segmentation is challenging because of the poor constrast in soft tissues. Although atlas-based approaches may provide a priori structural information by propagating manual expert delineations to a new individual space, the interindividual variability and registration errors can introduce bias in the results. Multi-atlas approaches can partly overcome some of these difficulties by selecting the most similar atlases among a large data base but the definition of similarity measure between the available atlases and the query individual has still to be addressed. The purpose of this paper is the evaluation of different strategies to simultaneously segment prostate, bladder and rectum from CT images, by selecting the most similar atlases from a prebuilt 24 atlas subset. Three similarity measures were considered: cross-correlation (CC), sum of squared differences (SSD) and mutual information (MI). Experiments on atlas ranking, selection strategies and fusion decision rules were carried out. Propagation of labels using the diffeomorphic demons non-rigid registration were used and the results were compared with manual delineations. Results suggest that CC and SSD are the best predictors for selecting similar atlases and that a vote decision rule is better suited to cope with large variabilities.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2005
A two-step method to determine the seed parameters for the planning of peripheral intravascular b... more A two-step method to determine the seed parameters for the planning of peripheral intravascular brachytherapy, which took the actual vessel geometry into consideration, was developed. Firstly, the characteristics of the vessel geometry was obtained by using active navigation; Then a method combined genetic algorithm with BFGS algorithm was applied to optimize the number of seeds, and the parameters associated with each seed such as the position, and the dwell time. Application of the method to a phantom model and three animal models of stenosis shows that promising result could be obtained, and the planning of peripheral intravascular brachytherapy should take actual vessel geometry into consideration.
Medical Imaging 2002: Visualization, Image-Guided Procedures, and Display, 2002
ABSTRACT In most planning procedures of intravascular brachytherapy the lesion path is assumed to... more ABSTRACT In most planning procedures of intravascular brachytherapy the lesion path is assumed to be a straight line and the dose distribution is essentially specified with respect to the seed. We propose a new approach for the planning of peripheral intravascular brachytherapy based on the characterization of the vessel by virtual exploratory navigation. In order to make the procedure more secure and reliable, the dosimetry planning takes actually account of the geometrical characteristics of the vessel (length, diameter, curvature). Virtual exploratory navigation constitutes the basis of optimal path planning (centering, positioning, trajectory definition) and dosimetry planning for high dose rate brachytherapy. In order to estimate the post-angioplasty vessel centerline and inner surface, a simplified simulation of the transluminal angioplasty procedure is performed using a single pre-angioplasty CT data set. Thanks to the dose rate computation performed in the whole CT volume, the irradiation of the surrounding anatomical structures can be anticipated. A virtual angioscopy like process is used to check the homogeneity of the dose distribution in the vessel wall. Preliminary results obtained from a phantom model and from an animal model of stenosis are reported.
Medical Imaging 2002: Physiology and Function from Multidimensional Images, 2002
ABSTRACT The characterization of the vessel and its lesion is part and parcel of any patient spec... more ABSTRACT The characterization of the vessel and its lesion is part and parcel of any patient specific planning of endovascular interventions. Thanks to the virtual exploration of a CT volume image acquired under clinical routine conditions we provide the practitioner with the primary elements to plan the intervention. Thus, the curve representing the evolution of the area of the lumen cross-section along the vessel centerline as well as the localization of the stenosis are derived from the virtual exploratory navigation. Due to the lack of reference in medical applications, an animal model of stenosis has been created and used to evaluate our approach. The stenosis characterization through virtual exploratory navigation has been applied to a set of ten sheep iliac arteries and compared with the characterization performed from classical reformatted CT slices and histological cross-sections. The validation of this virtual navigation based analysis is essential to the elaboration of planning systems aimed at the prevention of restenosis phenomena in transluminal angioplasty (accurate localization and covering of the lesion), as well as the treatment of the restenosis phenomena by intravascular brachytherapy (taking the vessel geometry into account).
2013 IEEE 10th International Symposium on Biomedical Imaging, 2013
ABSTRACT Although accurate delineations of the prostate on computed tomography (CT) images are re... more ABSTRACT Although accurate delineations of the prostate on computed tomography (CT) images are required for the planning in prostate cancer radiotherapy, these images do not provide the reliable soft tissue contrast. On the contrary, magnetic resonance (MR) images offer the possibility to better delineate both the tumor and healthy prostate tissues. Because CT is still used during the planning, MRICT image registration is an essential step to improve the targeting. In this paper, we propose a new framework to propagate the MRI prostate delineation to the CT-scan based on a robust contour matching approach. Prostate boundaries in CT are characterized with several multi-scale features and detected with a support vector machine (SVM) classifier. A new cost function for aligning the MRI delineation to the detected contours was developed. We evaluated the proposed approach on 11 manually aligned and delineated MR and CT images. The method outperformed the widely used mutual information (MI) and demonstrated the drawbacks of this metric for this application.
2009 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, 2009
ABSTRACT Polygon meshes representing the cerebral cortex have been increas-ingly used for visuali... more ABSTRACT Polygon meshes representing the cerebral cortex have been increas-ingly used for visualisation and analysis in biomedical imaging in recent years. Due to the highly convoluted structure of the cere-bral cortex, a number of methods have been proposed for inflating ...
Medical Imaging 2007: Ultrasonic Imaging and Signal Processing, 2007
Ultrasound (US) is one of the most used imaging modalities today as it is cheap, reliable, safe a... more Ultrasound (US) is one of the most used imaging modalities today as it is cheap, reliable, safe and widely available. There are a number of issues with US images in general. Besides reflections which is the basis of ultrasonic imaging, other phenomena such as diffraction, refraction, attenuation, dispersion and scattering appear when ultrasound propagates through different tissues. The generated images
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Papers by Oscar Acosta