International Journal of Computer Assisted Radiology and Surgery, 2011
Purpose According to differences in patient characteristics, surgical performance, or used surgic... more Purpose According to differences in patient characteristics, surgical performance, or used surgical technological resources, surgical interventions have high variability. No methods for the generation and comparison of statistical ‘mean’ surgical procedures are available. The convenience of these models is to provide increased evidence for clinical, technical, and administrative decision-making. Methods Based on several measurements of patient individual surgical treatments, we present a method of how to calculate a statistical ‘mean’ intervention model, called generic Surgical Process Model (gSPM), from a number of interventions. In a proof-of-concept study, we show how statistical ‘mean’ procedure courses can be computed and how differences between several of these models can be quantified. Patient individual surgical treatments of 102 cataract interventions from eye surgery were allocated to an ambulatory or inpatient sample, and the gSPMs for each of the samples were computed. Both treatment strategies are exemplary compared for the interventional phase Capsulorhexis. Results Statistical differences between the gSPMs of ambulatory and inpatient procedures of performance times for surgical activities and activity sequences were identified. Furthermore, the work flow that corresponds to the general recommended clinical treatment was recovered out of the individual Surgical Process Models. Conclusion The computation of gSPMs is a new approach in medical engineering and medical informatics. It supports increased evidence, e.g. for the application of alternative surgical strategies, investments for surgical technology, optimization protocols, or surgical education. Furthermore, this may be applicable in more technical research fields, as well, such as the development of surgical workflow management systems for the operating room of the future.
IEEE Transactions on Information Technology in Biomedicine, 2009
Intraoperative brain deformations decrease accuracy in image-guided neurosurgery. Approaches to q... more Intraoperative brain deformations decrease accuracy in image-guided neurosurgery. Approaches to quantify these deformations based on 3-D reconstruction of cortectomy surfaces have been described and have shown promising results regarding the extrapolation to the whole brain volume using additional prior knowledge or sparse volume modalities. Quantification of brain deformations from surface measurement requires the registration of surfaces at different times along the surgical procedure, with different challenges according to the patient and surgical step. In this paper, we propose a new flexible surface registration approach for any textured point cloud computed by stereoscopic or laser range approach. This method includes three terms: the first term is related to image intensities, the second to Euclidean distance, and the third to anatomical landmarks automatically extracted and continuously tracked in the 2-D video flow. Performance evaluation was performed on both phantom and clinical cases. The global method, including textured point cloud reconstruction, had accuracy within 2 mm, which is the usual rigid registration error of neuronavigation systems before deformations. Its main advantage is to consider all the available data, including the microscope video flow with higher temporal resolution than previously published methods.
The a uthors present t heir experiments in the c ommon u se of MEG data a nd 3 D navigation syste... more The a uthors present t heir experiments in the c ommon u se of MEG data a nd 3 D navigation system i n image guided n eurosurgery. The MagnetoEncephalographic data a re provided by a Magnes I biomagnetometer system from Bti and the neuro-navigation system is the Surgical Microscope Navigator ( SMN) developed b y Carl Zeiss. These systems
This paper presents the principle of multimodal and multi-informational neuronavigation as well a... more This paper presents the principle of multimodal and multi-informational neuronavigation as well as the data fusion environment we have developed for these techniques. Our fusion envi- ronment supports the planning step and includes registration, segmentation, 3D visualisation as well as data browsing and interaction tools. We provide a neuronavigation system with relevant information for the performance of the surgical act.
Detecting perfusion interhemispheric asymmetry in neurologic nuclear medicine imaging is an inter... more Detecting perfusion interhemispheric asymmetry in neurologic nuclear medicine imaging is an interesting approach to epilepsy. Methods: This study compared 4 methods that detect interhemispheric asymmetries of brain perfusion in SPECT. The first (M1) was conventional side-by-side expert-based visual interpretation of SPECT. The second (M2) was visual interpretation assisted by an interhemispheric difference (IHD) volume. The last 2 were automatic methods: unsupervised analysis using volumes of interest (M3) and unsupervised analysis of the IHD volume (M4). Use of these methods to detect possible perfusion asymmetry was compared on 60 simulated SPECT datasets by controlling the presence and location of asymmetries. From the detection results, localization receiver operating characteristic curves were generated and areas under curves were estimated and compared. Finally, the methods were applied to analyze interictal SPECT datasets to localize the epileptogenic focus in temporal lobe epilepsies. Results: This study showed an improvement in asymmetry detection on SPECT images with the methods using IHD volume (M2 and M4), in comparison with the other methods (M1 and M3). However, the most useful method for analyzing clinical SPECT datasets appeared to be visual inspection assisted by the IHD volume, since the automatic method using the IHD volume was less specific. Conclusion: The use of quantitative methods can improve performance in detection of perfusion asymmetry over visual inspection alone.
New MR imaging protocols enable visualisation of brain structures. However, for dedicated clinica... more New MR imaging protocols enable visualisation of brain structures. However, for dedicated clinical applications such as targeting Deep Brain Stimulation (DBS), a more accurate localisation requires the use of atlases. We developed a three-dimensional digitised mono-subject anatomical template of the human brain based on 3T MR images. By averaging 15 registered T1 image acquisitions, we have shown that the final image corresponds to an optimal image, limited by the performance of the 3T MR machine. We compared different preprocessing workflows for template construction. With the optimal strategy along with validated existing processing methods, one T1 template, one T2 template and one T1-T2 mixing template were created in order to improve visualisation of spatially complex deep structures. Reduction of voxel size to 0.25mm³ was also advantageous to observe fine structures and White Matter/Gray Matter intensity crossings. Results demonstrated that such a template also improved inter-patient registration for population comparison in DBS. These MR templates are made freely available to our community (http://www.vmip.org/mritemplate) to serve as a reference for neuro-image processing methods.
Among the basal ganglia nuclei, the subthalamic nucleus (STN) is considered to play a major role ... more Among the basal ganglia nuclei, the subthalamic nucleus (STN) is considered to play a major role in output modulation. The STN represents a relay of the motor cortico-basal ganglia-thalamo-cortical circuit and has become the standard surgical target for treating Parkinson’s patients with long-term motor fluctuations and dyskinesia. But chronic bilateral stimulation of the STN produces cognitive effects. According to animal and clinical studies, the STN also appears to have direct or indirect connections with the frontal associative and limbic areas. This prospective study was conducted to analyse regional cerebral blood flow changes in single-photon emission computed tomography imaging of six Parkinson’s patients before and after STN stimulation. We particularly focused on the dorsolateral prefrontal cortex and the frontal limbic areas using a manual anatomical MRI segmentation method. We defined nine regions of interest, segmenting each MR slice to quantify the regional cerebral blood flow on pre- and postoperative SPECT images. We normalised the region-of-interest-based measurements to the entire brain volume. The patients showed increased activation during STN stimulation in the dorsolateral prefrontal cortex bilaterally and no change in the anterior cingulate and orbito-frontal cortices. In our study, STN stimulation induced activation of premotor and associative frontal areas. Further studies are needed to underline involvement of the STN with the so-called limbic system.
International Journal of Computer Assisted Radiology and Surgery, 2006
Jannin P, Grova C, Maurer C. Model for designing and reporting reference based validation procedu... more Jannin P, Grova C, Maurer C. Model for designing and reporting reference based validation procedures in medical image processing. Int Journ.
We present a method to validate MRI/SPECT registration methods based on a set of computer-generat... more We present a method to validate MRI/SPECT registration methods based on a set of computer-generated SPECT data. The data set was produced through Monte Carlo simulations from an attenuation map and an activity map derived from a manually labeled T1-weighted MRI data set. Our approach intrinsically provides a gold standard to assess MRI/SPECT registration methods. It was successfully applied to the comparison of four registration methods based on similarity measurements: Mutual Information, Normalised Mutual Information, Correlation Ratio and Woods Criterion.
This paper describes an unsupervised method to help detection of significant functional inter-hem... more This paper describes an unsupervised method to help detection of significant functional inter-hemispheric asymmetries in brain SPECT. A validation of this method was performed with realistic simulated SPECT data sets with known asymmetries (in size and amplitude) as gold standard. Detection performances were assessed through Receiver Operating Characteristic (ROC) analysis based on measures of the overlap between known and detected asymmetries.
We present a technique to reconstruct the surface of the surgical field during neurosurgery. The ... more We present a technique to reconstruct the surface of the surgical field during neurosurgery. The images are taken with a stereo camera mounted on a surgical microscope, which is part of a neuronavigation system. We use an intensity-based method to calculate a dense disparity map over the whole image extend. Correspondences are established by exploiting the epipolar geometry and comparing image intensities along corresponding epipolar lines. The method does not require a strong calibration. Only the colineation denoted by the fundamental matrix, which maps corresponding epipolar lines from one image to the other, has to be known. The results show that our method is able to reconstruct the surface of the surgical field upto a few areas. It is limited at points of specular reflections of the wet brain surface and points of uniform texture.
This paper presents a new method for displaying in the same 3D scene multimodal preoperative imag... more This paper presents a new method for displaying in the same 3D scene multimodal preoperative images of a patient and images of the operative field viewed through surgical microscope binoculars for image-guided neurosurgery.
Part of the planning and performance of neurosurgery consists of determining target areas, areas ... more Part of the planning and performance of neurosurgery consists of determining target areas, areas to be avoided, landmark areas, and trajectories, all of which are components of the surgical script. Nowadays, neurosurgeons have access to multimodal medical imaging to support the definition of the surgical script. The purpose of this paper is to present a software environment developed by the authors that allows full multimodal and multi-informational planning as well as neuronavigation for epilepsy and tumor surgery. We have developed a data fusion environment dedicated to neuronavigation around the Surgical Microscope Neuronavigator system (Carl Zeiss, Oberkochen, Germany). This environment includes registration, segmentation, 3D visualization, and interaction-applied tools. It provides the neuronavigation system with the multimodal information involved in the definition of the surgical script: lesional areas, sulci, ventricles segmented from magnetic resonance imaging (MRI), vessels segmented from magnetic resonance angiography (MRA), functional areas from magneto-encephalography (MEG), and functional magnetic resonance imaging (fMRI) for somatosensory, motor, or language activation. These data are considered to be relevant for the performance of the surgical procedure. The definition of each entity results from the same procedure: registration to the anatomical MRI data set (defined as the reference data set), segmentation, fused 3D display, selection of the relevant entities for the surgical step, encoding in 3D surface-based representation, and storage of the 3D surfaces in a file recognized by the neuronavigation software (STP 3.4, Leibinger; Freiburg, Germany). Multimodal neuronavigation is illustrated with two clinical cases for which multimodal information was introduced into the neuronavigation system. Lesional areas were used to define and follow the surgical path, sulci and vessels helped identify the anatomical environment of the surgical field, and, finally, MEG and fMRI functional information helped determine the position of functional high-risk areas. In this short evaluation, the ability to access preoperative multi-functional and anatomical data within the neuronavigation system was a valuable support for the surgical procedure.
Objective: Improvement of the planning stage in image-guided surgery requires a better anticipati... more Objective: Improvement of the planning stage in image-guided surgery requires a better anticipation of the surgical procedure and its anatomical and functional environment. This anticipation should be provided by acquisition of multimodal medical images of the patient and by a better understanding of surgical procedures. In this paper, we propose improvements to the planning and performance of multimodal image-guided neurosurgery through the use of information models related to neurosurgical procedures.
In the general context of perfusion pattern modeling from single-photon emission computed tomogra... more In the general context of perfusion pattern modeling from single-photon emission computed tomographic (SPECT) data, the purpose of this study is to characterize interindividual functional variability and functional connectivity between anatomic structures in a set of SPECT data acquired from a homogeneous population of subjects. Materials and Methods. From volume of interest (VOI)-perfusion measurements performed on anatomically standardized SPECT data, we proposed to use correspondence analysis (CA) and hierarchical clustering (HC) to explore the structure of statistical dependencies among these measurements. The method was applied to study the perfusion pattern in two populations of subjects; namely, SPECT data from 27 healthy subjects and ictal SPECT data from 10 patients with mesiotemporal lobe epilepsy (MTLE). Results. For healthy subjects, anatomic structures showing statistically dependent perfusion patterns were classified into four groups; namely, temporomesial structures, internal structures, posterior structures, and remaining cortex. For patients with MTLE, they were classified as temporomesial structures, surrounding temporal structures, internal structures, and remaining cortex. Anatomic structures of each group showed similar perfusion behavior so that they may be functionally connected and may belong to the same network. Our main result is that the temporal pole and lenticular nucleus seemed to be highly relevant to characterize ictal perfusion in patients with MTLE. This exploratory analysis suggests that a network involving temporal structures, lenticular nucleus, brainstem, and cerebellum seems to be involved during MTLE seizures. Conclusion. CA followed by HC is a promising approach to explore brain perfusion patterns from SPECT VOI measurements. Key Words. Functional variability; single-photon emission computed tomography (SPECT); correspondence analysis (CA); hierarchical clustering (HC); mesio-temporal lobe epilepsy; ictal perfusion.
3D imaging systems and algorithms give virtual representations of the real world. New emergent ha... more 3D imaging systems and algorithms give virtual representations of the real world. New emergent hardware systems create links between virtual information and the real world. They allow the simulation and the remote performance of a real action. For instance, in image-guided surgery, 3D digitizers (localizers) give information from the real world to the virtual one and robotics environment from the virtual world to the real one. Virtual and real information must be also visually confronted to facilitate their understanding. The solution, we propose here, is the superimposition of the real view of the anatomical regions concerned by a surgical act with the 3D digital data sets. Rather than the solutions which display the virtual images in the real world, our method consists in a ray traced texture mapping which provides the display of real images in a computed world.
International Journal of Computer Assisted Radiology and Surgery, 2011
Purpose According to differences in patient characteristics, surgical performance, or used surgic... more Purpose According to differences in patient characteristics, surgical performance, or used surgical technological resources, surgical interventions have high variability. No methods for the generation and comparison of statistical ‘mean’ surgical procedures are available. The convenience of these models is to provide increased evidence for clinical, technical, and administrative decision-making. Methods Based on several measurements of patient individual surgical treatments, we present a method of how to calculate a statistical ‘mean’ intervention model, called generic Surgical Process Model (gSPM), from a number of interventions. In a proof-of-concept study, we show how statistical ‘mean’ procedure courses can be computed and how differences between several of these models can be quantified. Patient individual surgical treatments of 102 cataract interventions from eye surgery were allocated to an ambulatory or inpatient sample, and the gSPMs for each of the samples were computed. Both treatment strategies are exemplary compared for the interventional phase Capsulorhexis. Results Statistical differences between the gSPMs of ambulatory and inpatient procedures of performance times for surgical activities and activity sequences were identified. Furthermore, the work flow that corresponds to the general recommended clinical treatment was recovered out of the individual Surgical Process Models. Conclusion The computation of gSPMs is a new approach in medical engineering and medical informatics. It supports increased evidence, e.g. for the application of alternative surgical strategies, investments for surgical technology, optimization protocols, or surgical education. Furthermore, this may be applicable in more technical research fields, as well, such as the development of surgical workflow management systems for the operating room of the future.
IEEE Transactions on Information Technology in Biomedicine, 2009
Intraoperative brain deformations decrease accuracy in image-guided neurosurgery. Approaches to q... more Intraoperative brain deformations decrease accuracy in image-guided neurosurgery. Approaches to quantify these deformations based on 3-D reconstruction of cortectomy surfaces have been described and have shown promising results regarding the extrapolation to the whole brain volume using additional prior knowledge or sparse volume modalities. Quantification of brain deformations from surface measurement requires the registration of surfaces at different times along the surgical procedure, with different challenges according to the patient and surgical step. In this paper, we propose a new flexible surface registration approach for any textured point cloud computed by stereoscopic or laser range approach. This method includes three terms: the first term is related to image intensities, the second to Euclidean distance, and the third to anatomical landmarks automatically extracted and continuously tracked in the 2-D video flow. Performance evaluation was performed on both phantom and clinical cases. The global method, including textured point cloud reconstruction, had accuracy within 2 mm, which is the usual rigid registration error of neuronavigation systems before deformations. Its main advantage is to consider all the available data, including the microscope video flow with higher temporal resolution than previously published methods.
The a uthors present t heir experiments in the c ommon u se of MEG data a nd 3 D navigation syste... more The a uthors present t heir experiments in the c ommon u se of MEG data a nd 3 D navigation system i n image guided n eurosurgery. The MagnetoEncephalographic data a re provided by a Magnes I biomagnetometer system from Bti and the neuro-navigation system is the Surgical Microscope Navigator ( SMN) developed b y Carl Zeiss. These systems
This paper presents the principle of multimodal and multi-informational neuronavigation as well a... more This paper presents the principle of multimodal and multi-informational neuronavigation as well as the data fusion environment we have developed for these techniques. Our fusion envi- ronment supports the planning step and includes registration, segmentation, 3D visualisation as well as data browsing and interaction tools. We provide a neuronavigation system with relevant information for the performance of the surgical act.
Detecting perfusion interhemispheric asymmetry in neurologic nuclear medicine imaging is an inter... more Detecting perfusion interhemispheric asymmetry in neurologic nuclear medicine imaging is an interesting approach to epilepsy. Methods: This study compared 4 methods that detect interhemispheric asymmetries of brain perfusion in SPECT. The first (M1) was conventional side-by-side expert-based visual interpretation of SPECT. The second (M2) was visual interpretation assisted by an interhemispheric difference (IHD) volume. The last 2 were automatic methods: unsupervised analysis using volumes of interest (M3) and unsupervised analysis of the IHD volume (M4). Use of these methods to detect possible perfusion asymmetry was compared on 60 simulated SPECT datasets by controlling the presence and location of asymmetries. From the detection results, localization receiver operating characteristic curves were generated and areas under curves were estimated and compared. Finally, the methods were applied to analyze interictal SPECT datasets to localize the epileptogenic focus in temporal lobe epilepsies. Results: This study showed an improvement in asymmetry detection on SPECT images with the methods using IHD volume (M2 and M4), in comparison with the other methods (M1 and M3). However, the most useful method for analyzing clinical SPECT datasets appeared to be visual inspection assisted by the IHD volume, since the automatic method using the IHD volume was less specific. Conclusion: The use of quantitative methods can improve performance in detection of perfusion asymmetry over visual inspection alone.
New MR imaging protocols enable visualisation of brain structures. However, for dedicated clinica... more New MR imaging protocols enable visualisation of brain structures. However, for dedicated clinical applications such as targeting Deep Brain Stimulation (DBS), a more accurate localisation requires the use of atlases. We developed a three-dimensional digitised mono-subject anatomical template of the human brain based on 3T MR images. By averaging 15 registered T1 image acquisitions, we have shown that the final image corresponds to an optimal image, limited by the performance of the 3T MR machine. We compared different preprocessing workflows for template construction. With the optimal strategy along with validated existing processing methods, one T1 template, one T2 template and one T1-T2 mixing template were created in order to improve visualisation of spatially complex deep structures. Reduction of voxel size to 0.25mm³ was also advantageous to observe fine structures and White Matter/Gray Matter intensity crossings. Results demonstrated that such a template also improved inter-patient registration for population comparison in DBS. These MR templates are made freely available to our community (http://www.vmip.org/mritemplate) to serve as a reference for neuro-image processing methods.
Among the basal ganglia nuclei, the subthalamic nucleus (STN) is considered to play a major role ... more Among the basal ganglia nuclei, the subthalamic nucleus (STN) is considered to play a major role in output modulation. The STN represents a relay of the motor cortico-basal ganglia-thalamo-cortical circuit and has become the standard surgical target for treating Parkinson’s patients with long-term motor fluctuations and dyskinesia. But chronic bilateral stimulation of the STN produces cognitive effects. According to animal and clinical studies, the STN also appears to have direct or indirect connections with the frontal associative and limbic areas. This prospective study was conducted to analyse regional cerebral blood flow changes in single-photon emission computed tomography imaging of six Parkinson’s patients before and after STN stimulation. We particularly focused on the dorsolateral prefrontal cortex and the frontal limbic areas using a manual anatomical MRI segmentation method. We defined nine regions of interest, segmenting each MR slice to quantify the regional cerebral blood flow on pre- and postoperative SPECT images. We normalised the region-of-interest-based measurements to the entire brain volume. The patients showed increased activation during STN stimulation in the dorsolateral prefrontal cortex bilaterally and no change in the anterior cingulate and orbito-frontal cortices. In our study, STN stimulation induced activation of premotor and associative frontal areas. Further studies are needed to underline involvement of the STN with the so-called limbic system.
International Journal of Computer Assisted Radiology and Surgery, 2006
Jannin P, Grova C, Maurer C. Model for designing and reporting reference based validation procedu... more Jannin P, Grova C, Maurer C. Model for designing and reporting reference based validation procedures in medical image processing. Int Journ.
We present a method to validate MRI/SPECT registration methods based on a set of computer-generat... more We present a method to validate MRI/SPECT registration methods based on a set of computer-generated SPECT data. The data set was produced through Monte Carlo simulations from an attenuation map and an activity map derived from a manually labeled T1-weighted MRI data set. Our approach intrinsically provides a gold standard to assess MRI/SPECT registration methods. It was successfully applied to the comparison of four registration methods based on similarity measurements: Mutual Information, Normalised Mutual Information, Correlation Ratio and Woods Criterion.
This paper describes an unsupervised method to help detection of significant functional inter-hem... more This paper describes an unsupervised method to help detection of significant functional inter-hemispheric asymmetries in brain SPECT. A validation of this method was performed with realistic simulated SPECT data sets with known asymmetries (in size and amplitude) as gold standard. Detection performances were assessed through Receiver Operating Characteristic (ROC) analysis based on measures of the overlap between known and detected asymmetries.
We present a technique to reconstruct the surface of the surgical field during neurosurgery. The ... more We present a technique to reconstruct the surface of the surgical field during neurosurgery. The images are taken with a stereo camera mounted on a surgical microscope, which is part of a neuronavigation system. We use an intensity-based method to calculate a dense disparity map over the whole image extend. Correspondences are established by exploiting the epipolar geometry and comparing image intensities along corresponding epipolar lines. The method does not require a strong calibration. Only the colineation denoted by the fundamental matrix, which maps corresponding epipolar lines from one image to the other, has to be known. The results show that our method is able to reconstruct the surface of the surgical field upto a few areas. It is limited at points of specular reflections of the wet brain surface and points of uniform texture.
This paper presents a new method for displaying in the same 3D scene multimodal preoperative imag... more This paper presents a new method for displaying in the same 3D scene multimodal preoperative images of a patient and images of the operative field viewed through surgical microscope binoculars for image-guided neurosurgery.
Part of the planning and performance of neurosurgery consists of determining target areas, areas ... more Part of the planning and performance of neurosurgery consists of determining target areas, areas to be avoided, landmark areas, and trajectories, all of which are components of the surgical script. Nowadays, neurosurgeons have access to multimodal medical imaging to support the definition of the surgical script. The purpose of this paper is to present a software environment developed by the authors that allows full multimodal and multi-informational planning as well as neuronavigation for epilepsy and tumor surgery. We have developed a data fusion environment dedicated to neuronavigation around the Surgical Microscope Neuronavigator system (Carl Zeiss, Oberkochen, Germany). This environment includes registration, segmentation, 3D visualization, and interaction-applied tools. It provides the neuronavigation system with the multimodal information involved in the definition of the surgical script: lesional areas, sulci, ventricles segmented from magnetic resonance imaging (MRI), vessels segmented from magnetic resonance angiography (MRA), functional areas from magneto-encephalography (MEG), and functional magnetic resonance imaging (fMRI) for somatosensory, motor, or language activation. These data are considered to be relevant for the performance of the surgical procedure. The definition of each entity results from the same procedure: registration to the anatomical MRI data set (defined as the reference data set), segmentation, fused 3D display, selection of the relevant entities for the surgical step, encoding in 3D surface-based representation, and storage of the 3D surfaces in a file recognized by the neuronavigation software (STP 3.4, Leibinger; Freiburg, Germany). Multimodal neuronavigation is illustrated with two clinical cases for which multimodal information was introduced into the neuronavigation system. Lesional areas were used to define and follow the surgical path, sulci and vessels helped identify the anatomical environment of the surgical field, and, finally, MEG and fMRI functional information helped determine the position of functional high-risk areas. In this short evaluation, the ability to access preoperative multi-functional and anatomical data within the neuronavigation system was a valuable support for the surgical procedure.
Objective: Improvement of the planning stage in image-guided surgery requires a better anticipati... more Objective: Improvement of the planning stage in image-guided surgery requires a better anticipation of the surgical procedure and its anatomical and functional environment. This anticipation should be provided by acquisition of multimodal medical images of the patient and by a better understanding of surgical procedures. In this paper, we propose improvements to the planning and performance of multimodal image-guided neurosurgery through the use of information models related to neurosurgical procedures.
In the general context of perfusion pattern modeling from single-photon emission computed tomogra... more In the general context of perfusion pattern modeling from single-photon emission computed tomographic (SPECT) data, the purpose of this study is to characterize interindividual functional variability and functional connectivity between anatomic structures in a set of SPECT data acquired from a homogeneous population of subjects. Materials and Methods. From volume of interest (VOI)-perfusion measurements performed on anatomically standardized SPECT data, we proposed to use correspondence analysis (CA) and hierarchical clustering (HC) to explore the structure of statistical dependencies among these measurements. The method was applied to study the perfusion pattern in two populations of subjects; namely, SPECT data from 27 healthy subjects and ictal SPECT data from 10 patients with mesiotemporal lobe epilepsy (MTLE). Results. For healthy subjects, anatomic structures showing statistically dependent perfusion patterns were classified into four groups; namely, temporomesial structures, internal structures, posterior structures, and remaining cortex. For patients with MTLE, they were classified as temporomesial structures, surrounding temporal structures, internal structures, and remaining cortex. Anatomic structures of each group showed similar perfusion behavior so that they may be functionally connected and may belong to the same network. Our main result is that the temporal pole and lenticular nucleus seemed to be highly relevant to characterize ictal perfusion in patients with MTLE. This exploratory analysis suggests that a network involving temporal structures, lenticular nucleus, brainstem, and cerebellum seems to be involved during MTLE seizures. Conclusion. CA followed by HC is a promising approach to explore brain perfusion patterns from SPECT VOI measurements. Key Words. Functional variability; single-photon emission computed tomography (SPECT); correspondence analysis (CA); hierarchical clustering (HC); mesio-temporal lobe epilepsy; ictal perfusion.
3D imaging systems and algorithms give virtual representations of the real world. New emergent ha... more 3D imaging systems and algorithms give virtual representations of the real world. New emergent hardware systems create links between virtual information and the real world. They allow the simulation and the remote performance of a real action. For instance, in image-guided surgery, 3D digitizers (localizers) give information from the real world to the virtual one and robotics environment from the virtual world to the real one. Virtual and real information must be also visually confronted to facilitate their understanding. The solution, we propose here, is the superimposition of the real view of the anatomical regions concerned by a surgical act with the 3D digital data sets. Rather than the solutions which display the virtual images in the real world, our method consists in a ray traced texture mapping which provides the display of real images in a computed world.
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Papers by Pierre Jannin