The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Guy Cloutier - One of the best experts on this subject based on the ideXlab platform.
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A multimodality vascular Imaging Phantom of an abdominal aortic aneurysm with a visible thrombus
Medical physics, 2013Co-Authors: Louise Allard, Gilles Soulez, Zhao Qin, Boris Chayer, David Roy, Guy CloutierAbstract:Purpose: With the continuous development of new stent grafts and implantation techniques, it has now become technically feasible to treat abdominal aortic aneurysms (AAA) with challenging anatomy using endovascular repair with standard, fenestrated, or branched stent-grafts. In vitro experimentations are very useful to improve stent-graft design and conformability or Imaging guidance for stent-graft delivery or follow-up. Vascular replicas also help to better understand the limitation of endovascular approaches in challenging anatomy and possibly improve surgical planning or training by practicing high risk clinical procedures in the laboratory to improve outcomes in the operating room. Most AAA Phantoms available have a very basic anatomy, which is not representative of the clinical reality. This paper presents a method of fabrication of a realistic AAA Phantom with a visible thrombus, as well as some mechanical properties characterizing such Phantom. Methods: A realistic AAA geometry replica of a real patient anatomy taken from a multidetector computed tomography (CT) scan was manufactured. To demonstrate the multimodality Imaging capability of this new Phantom with a thrombus visible in magnetic resonance (MR) angiography, CT angiography (CTA), digital subtraction angiography (DSA), and ultrasound, image acquisitions with all these modalities were performed by using standard clinical protocols. Potential usemore » of this Phantom for stent deployment was also tested. A rheometer allowed defining hyperelastic and viscoelastic properties of Phantom materials. Results: MR Imaging measurements of SNR and CNR values on T1 and T2-weighted sequences and MR angiography indicated reasonable agreement with published values of AAA thrombus and abdominal components in vivo. X-ray absorption also lay within normal ranges of AAA patients and was representative of findings observed on CTA, fluoroscopy, and DSA. Ultrasound propagation speeds for developed materials were also in concordance with the literature for vascular and abdominal tissues. Conclusions: The mimicked abdominal tissues, AAA wall, and surrounding thrombus were developed to match Imaging features of in vivo MR, CT, and ultrasound examinations. This Phantom should be of value for image calibration, segmentation, and testing of endovascular devices for AAA endovascular repair.« less
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a multimodality vascular Imaging Phantom with fiducial markers visible in dsa cta mra and ultrasound
Medical Physics, 2004Co-Authors: Guy Cloutier, Gilles Soulez, Pierre Teppaz, Salah D. Qanadli, Zhao Qin, Louise Allard, Francois Cloutier, Louis-gilles DurandAbstract:The objective was to design a vascular Phantom compatible with digital subtraction angiography, computerized tomography angiography, ultrasound and magnetic resonance angiography (MRA). Fiducial markers were implanted at precise known locations in the Phantom to facilitate identification and orientation of plane views from three-dimensional (3-D) reconstructed images. A vascular conduit connected to tubing at the extremities of the Phantom ran through an agar-based gel filling it. A vessel wall in latex was included around the conduit to avoid diffusion of contrast agents. Using a lost-material casting technique based on a low melting point metal, geometries of pathological vessels were modeled. During the experimental testing, fiducial markers were detectable in all modalities without distortion. No leak of gadolinium through the vascular wall was observed on MRA after 5 hours. Moreover, no significant deformation of the vascular conduit was noted during the fabrication process (confirmed by microtome slicing along the vessel). The potential use of the Phantom for calibration, rescaling, and fusion of 3-D images obtained from the different modalities as well as its use for the evaluation of intra- and inter-modality comparative studies of Imaging systems are discussed. In conclusion, the vascular Phantom can allow accurate calibration of radiological Imaging devices based on x-ray, magnetic resonance and ultrasound and quantitative comparisons of the geometric accuracy of the vessel lumen obtained with each of these methods on a given well defined 3-D geometry.
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Medical Imaging: Image-Guided Procedures - Multimodality vascular Imaging Phantom for calibration purpose
Medical Imaging 2003: Visualization Image-Guided Procedures and Display, 2003Co-Authors: Guy Cloutier, Gilles Soulez, Pierre Teppaz, Salah D. Qanadli, Zhao Qin, Louis-gilles DurandAbstract:The objective of the project was to design a vascular Phantom compatible with X-ray, ultrasound and MRI. Fiducial markers were implanted at precise known locations in the Phantom to facilitate identification and orientation of plane views from the 3D reconstructed images. They also allowed optimizing image fusion and calibration. A vascular conduit connected to tubing at the extremities of the Phantom ran through an agar-based gel filling it. A vessel wall in latex was included to avoid diffusion of contrast agents. Using a lost-material casting technique based on a low melting point metal, complex realistic geometries of normal and pathological vessels were modeled. The fiducial markers were detectable in all modalities without distortion. No leak of gadolinium through the vascular wall was observed on MRI for 5h of scan. The potential use of the Phantom for calibration, rescaling, and fusion of 3D images obtained from the different modalities as well as its use for the evaluation of intra and inter-modality comparative studies of Imaging systems were recently demonstrated by our group (results published in SPIE-2003). Endovascular prostheses were also implanted into the lumen of the Phantom to evaluate the extent of metallic Imaging artifacts (results submitted elsewhere). In conclusion, the Phantom can allow accurate calibration of radiological Imaging devices and quantitative comparisons of the geometric accuracy of each radiological Imaging method tested.
Chingpo Lin - One of the best experts on this subject based on the ideXlab platform.
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resolving crossing fibres using constrained spherical deconvolution validation using diffusion weighted Imaging Phantom data
NeuroImage, 2008Co-Authors: Jacquesdonald Tournier, Chunhung Yeh, Fernando Calamante, Kuanhung Cho, Alan Connelly, Chingpo LinAbstract:Diffusion-weighted Imaging can potentially be used to infer the connectivity of the human brain in vivo using fibre-tracking techniques, and is therefore of great interest to neuroscientists and clinicians. A key requirement for fibre tracking is the accurate estimation of white matter fibre orientations within each Imaging voxel. The diffusion tensor model, which is widely used for this purpose, has been shown to be inadequate in crossing fibre regions. A number of approaches have recently been proposed to address this issue, based on high angular resolution diffusion-weighted Imaging (HARDI) data. In this study, an experimental model of crossing fibres, consisting of water-filled plastic capillaries, is used to thoroughly assess three such techniques: constrained spherical deconvolution (CSD), super-resolved CSD (super-CSD) and Q-ball Imaging (QBI). HARDI data were acquired over a range of crossing angles and b-values, from which fibre orientations were computed using each technique. All techniques were capable of resolving the two fibre populations down to a crossing angle of 45°, and down to 30° for super-CSD. A bias was observed in the fibre orientations estimated by QBI for crossing angles other than 90°, consistent with previous simulation results. Finally, for a 45° crossing, the minimum b-value required to resolve the fibre orientations was 4000s/mm2 for QBI, 2000s/mm2 for CSD, and 1000s/mm2 for super-CSD. The quality of estimation of fibre orientations may profoundly affect fibre tracking attempts, and the results presented provide important additional information regarding performance characteristics of well-known methods.
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resolving crossing fibres using constrained spherical deconvolution validation using diffusion weighted Imaging Phantom data
NeuroImage, 2008Co-Authors: Jacquesdonald Tournier, Chunhung Yeh, Fernando Calamante, Kuanhung Cho, Alan Connelly, Chingpo LinAbstract:Diffusion-weighted Imaging can potentially be used to infer the connectivity of the human brain in vivo using fibre-tracking techniques, and is therefore of great interest to neuroscientists and clinicians. A key requirement for fibre tracking is the accurate estimation of white matter fibre orientations within each Imaging voxel. The diffusion tensor model, which is widely used for this purpose, has been shown to be inadequate in crossing fibre regions. A number of approaches have recently been proposed to address this issue, based on high angular resolution diffusion-weighted Imaging (HARDI) data. In this study, an experimental model of crossing fibres, consisting of water-filled plastic capillaries, is used to thoroughly assess three such techniques: constrained spherical deconvolution (CSD), super-resolved CSD (super-CSD) and Q-ball Imaging (QBI). HARDI data were acquired over a range of crossing angles and b-values, from which fibre orientations were computed using each technique. All techniques were capable of resolving the two fibre populations down to a crossing angle of 45 degrees , and down to 30 degrees for super-CSD. A bias was observed in the fibre orientations estimated by QBI for crossing angles other than 90 degrees, consistent with previous simulation results. Finally, for a 45 degrees crossing, the minimum b-value required to resolve the fibre orientations was 4000 s/mm(2) for QBI, 2000 s/mm(2) for CSD, and 1000 s/mm(2) for super-CSD. The quality of estimation of fibre orientations may profoundly affect fibre tracking attempts, and the results presented provide important additional information regarding performance characteristics of well-known methods.
Fernando Calamante - One of the best experts on this subject based on the ideXlab platform.
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resolving crossing fibres using constrained spherical deconvolution validation using diffusion weighted Imaging Phantom data
NeuroImage, 2008Co-Authors: Jacquesdonald Tournier, Chunhung Yeh, Fernando Calamante, Kuanhung Cho, Alan Connelly, Chingpo LinAbstract:Diffusion-weighted Imaging can potentially be used to infer the connectivity of the human brain in vivo using fibre-tracking techniques, and is therefore of great interest to neuroscientists and clinicians. A key requirement for fibre tracking is the accurate estimation of white matter fibre orientations within each Imaging voxel. The diffusion tensor model, which is widely used for this purpose, has been shown to be inadequate in crossing fibre regions. A number of approaches have recently been proposed to address this issue, based on high angular resolution diffusion-weighted Imaging (HARDI) data. In this study, an experimental model of crossing fibres, consisting of water-filled plastic capillaries, is used to thoroughly assess three such techniques: constrained spherical deconvolution (CSD), super-resolved CSD (super-CSD) and Q-ball Imaging (QBI). HARDI data were acquired over a range of crossing angles and b-values, from which fibre orientations were computed using each technique. All techniques were capable of resolving the two fibre populations down to a crossing angle of 45°, and down to 30° for super-CSD. A bias was observed in the fibre orientations estimated by QBI for crossing angles other than 90°, consistent with previous simulation results. Finally, for a 45° crossing, the minimum b-value required to resolve the fibre orientations was 4000s/mm2 for QBI, 2000s/mm2 for CSD, and 1000s/mm2 for super-CSD. The quality of estimation of fibre orientations may profoundly affect fibre tracking attempts, and the results presented provide important additional information regarding performance characteristics of well-known methods.
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resolving crossing fibres using constrained spherical deconvolution validation using diffusion weighted Imaging Phantom data
NeuroImage, 2008Co-Authors: Jacquesdonald Tournier, Chunhung Yeh, Fernando Calamante, Kuanhung Cho, Alan Connelly, Chingpo LinAbstract:Diffusion-weighted Imaging can potentially be used to infer the connectivity of the human brain in vivo using fibre-tracking techniques, and is therefore of great interest to neuroscientists and clinicians. A key requirement for fibre tracking is the accurate estimation of white matter fibre orientations within each Imaging voxel. The diffusion tensor model, which is widely used for this purpose, has been shown to be inadequate in crossing fibre regions. A number of approaches have recently been proposed to address this issue, based on high angular resolution diffusion-weighted Imaging (HARDI) data. In this study, an experimental model of crossing fibres, consisting of water-filled plastic capillaries, is used to thoroughly assess three such techniques: constrained spherical deconvolution (CSD), super-resolved CSD (super-CSD) and Q-ball Imaging (QBI). HARDI data were acquired over a range of crossing angles and b-values, from which fibre orientations were computed using each technique. All techniques were capable of resolving the two fibre populations down to a crossing angle of 45 degrees , and down to 30 degrees for super-CSD. A bias was observed in the fibre orientations estimated by QBI for crossing angles other than 90 degrees, consistent with previous simulation results. Finally, for a 45 degrees crossing, the minimum b-value required to resolve the fibre orientations was 4000 s/mm(2) for QBI, 2000 s/mm(2) for CSD, and 1000 s/mm(2) for super-CSD. The quality of estimation of fibre orientations may profoundly affect fibre tracking attempts, and the results presented provide important additional information regarding performance characteristics of well-known methods.
Alan Connelly - One of the best experts on this subject based on the ideXlab platform.
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resolving crossing fibres using constrained spherical deconvolution validation using diffusion weighted Imaging Phantom data
NeuroImage, 2008Co-Authors: Jacquesdonald Tournier, Chunhung Yeh, Fernando Calamante, Kuanhung Cho, Alan Connelly, Chingpo LinAbstract:Diffusion-weighted Imaging can potentially be used to infer the connectivity of the human brain in vivo using fibre-tracking techniques, and is therefore of great interest to neuroscientists and clinicians. A key requirement for fibre tracking is the accurate estimation of white matter fibre orientations within each Imaging voxel. The diffusion tensor model, which is widely used for this purpose, has been shown to be inadequate in crossing fibre regions. A number of approaches have recently been proposed to address this issue, based on high angular resolution diffusion-weighted Imaging (HARDI) data. In this study, an experimental model of crossing fibres, consisting of water-filled plastic capillaries, is used to thoroughly assess three such techniques: constrained spherical deconvolution (CSD), super-resolved CSD (super-CSD) and Q-ball Imaging (QBI). HARDI data were acquired over a range of crossing angles and b-values, from which fibre orientations were computed using each technique. All techniques were capable of resolving the two fibre populations down to a crossing angle of 45°, and down to 30° for super-CSD. A bias was observed in the fibre orientations estimated by QBI for crossing angles other than 90°, consistent with previous simulation results. Finally, for a 45° crossing, the minimum b-value required to resolve the fibre orientations was 4000s/mm2 for QBI, 2000s/mm2 for CSD, and 1000s/mm2 for super-CSD. The quality of estimation of fibre orientations may profoundly affect fibre tracking attempts, and the results presented provide important additional information regarding performance characteristics of well-known methods.
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resolving crossing fibres using constrained spherical deconvolution validation using diffusion weighted Imaging Phantom data
NeuroImage, 2008Co-Authors: Jacquesdonald Tournier, Chunhung Yeh, Fernando Calamante, Kuanhung Cho, Alan Connelly, Chingpo LinAbstract:Diffusion-weighted Imaging can potentially be used to infer the connectivity of the human brain in vivo using fibre-tracking techniques, and is therefore of great interest to neuroscientists and clinicians. A key requirement for fibre tracking is the accurate estimation of white matter fibre orientations within each Imaging voxel. The diffusion tensor model, which is widely used for this purpose, has been shown to be inadequate in crossing fibre regions. A number of approaches have recently been proposed to address this issue, based on high angular resolution diffusion-weighted Imaging (HARDI) data. In this study, an experimental model of crossing fibres, consisting of water-filled plastic capillaries, is used to thoroughly assess three such techniques: constrained spherical deconvolution (CSD), super-resolved CSD (super-CSD) and Q-ball Imaging (QBI). HARDI data were acquired over a range of crossing angles and b-values, from which fibre orientations were computed using each technique. All techniques were capable of resolving the two fibre populations down to a crossing angle of 45 degrees , and down to 30 degrees for super-CSD. A bias was observed in the fibre orientations estimated by QBI for crossing angles other than 90 degrees, consistent with previous simulation results. Finally, for a 45 degrees crossing, the minimum b-value required to resolve the fibre orientations was 4000 s/mm(2) for QBI, 2000 s/mm(2) for CSD, and 1000 s/mm(2) for super-CSD. The quality of estimation of fibre orientations may profoundly affect fibre tracking attempts, and the results presented provide important additional information regarding performance characteristics of well-known methods.
Marvin M. Doyley - One of the best experts on this subject based on the ideXlab platform.
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Noninvasive carotid artery elastography using multielement synthetic aperture Imaging: Phantom and in vivo evaluation.
Medical physics, 2017Co-Authors: Rohit Nayak, Giovanni Schifitto, Marvin M. DoyleyAbstract:Purpose Vascular elastography can visualize the strain distribution in the carotid artery, which could be useful in assessing the propensity of advanced plaques to rupture. In our previous studies, we demonstrated that sparse synthetic aperture (SA) Imaging can produce high quality vascular strain elastograms. However, the low output power of SA Imaging may hamper its clinical utility. In this study, we hypothesize that multi-element defocused emissions can overcome this limitation and improve the quality of the vascular strain elastograms. Methods To assess the impact of attenuation on the elastographic performance of SAand (multi-element synthetic aperture) MSA Imaging, we conducted experiments using het-erogeneous vessel Phantoms with ideal (0.1 dB/cm/MHz) and realistic (0.75 dB/cm/MHz) attenuation. Further, we validated the results of the Phantom study in vivo, on a healthy male volunteer. All echo Imaging was performed at a transmit frequency of 5 MHz, using a commercially available ultrasound scanner (Sonix RP, Ultrasonix Medical Corp., Richmond, BC, Canada). Results The results from the Phantom results demonstrated that plaques were visible in all strain elastograms, but those produced using MSA Imaging had less artifacts. MSA Imaging improved the elastographic contrast to noise ratio (CNRe) of the vascular elas-tograms by 14.58 dB relative to SA Imaging, and 9.1 dB relative to compounded plane wave (CPW) Imaging. Further, the results demonstrated that the elastographic performance of MSA Imaging improved with increase in (i) the number of transmit-receive events and (ii) the size of the transmit sub-aperture, up to 13 elements. Using larger sub-apertures degraded the elastographic performance. The results from the in vivo study were in good agreement with the Phantom results. Speci_cally, using a defocused multi-element transmit sub-aperture for SA Imaging improved the performance of vascular elastography. Conclusions The results suggested that MSA Imaging can produce reliable vascular stain elastograms. Future studies will involve using coded excitations to improve the CNRe and frame-rate of the proposed technique for vascular elastography. This article is protected by copyright. All rights reserved.
