The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Rajiv Gupta - One of the best experts on this subject based on the ideXlab platform.
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high resolution dynamic angiography using flat panel Volume CT feasibility demonstration for neuro and lower limb vascular applications
European Radiology, 2015Co-Authors: Michael Grasruck, Amit Mehndiratta, James D Rabinov, Eric C Liao, David Crandell, Rajiv GuptaAbstract:ObjeCTive This paper evaluates a prototype flat-panel Volume CT (fpVCT) for dynamic in vivo imaging in a variety of neurovascular and lower limb applications.
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Experimental Flat-Panel High-Spatial- Resolution Volume CT of the Temporal Bone
2014Co-Authors: Rajiv Gupta, Soenke H. Bartling, Samit Kumar Basu, W R Ross, H Becker, Armin Horst Pfoh, Thomas Brady, Hugh D CurtinAbstract:BACKGROUND AND PURPOSE: A CT scanner employing a digital flat-panel deteCTor is capable of very high spatial resolution as compared with a multi-seCTion CT (MSCT) scanner. Our purpose was to determine how well a prototypical Volume CT (VCT) scanner with a flat-panel deteCTor system defines fine struCTures in temporal bone. METHODS: Four partially manipulated temporal-bone specimens were imaged by use of a prototypical cone-beam VCT scanner with a flat-panel deteCTor system at an isometric resolu-tion of 150 m at the isocenter. These specimens were also depiCTed by state-of-the-art multiseCTion CT (MSCT). Forty-two struCTures imaged by both scanners were qualitatively assessed and rated, and scores assigned to VCT findings were compared with those of MSCT. RESULTS: Qualitative assessment of anatomic struCTures, lesions, cochlear implants, and middle-ear hearing aids indicated that image quality was significantly better with VCT (P <.001). StruCTures near the spatial-resolution limit of MSCT (e.g., bony covering of the tympanic segment of the facial canal, the incudo-stapedial joint, the proximal vestibular aqueduCT, the interscalar septum, and the modiolus) had higher contrast and less partial-Volume effeCT with VCT. CONCLUSION: The flat-panel prototype provides better definition of fine osseous struCTure
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temporal resolution of dynamic angiography using flat panel Volume CT in vivo evaluation of time dependent vascular pathologies
American Journal of Neuroradiology, 2011Co-Authors: Rajiv Gupta, Michael Grasruck, Christianne Leidecker, Amit Mehndiratta, Alim P Mitha, Christopher S Ogilvy, Thomas J BradyAbstract:BACKGROUND AND PURPOSE: Recently introduced fpVCT scanners can capture Volumetric (4D) time-varying projeCTions enabling whole-organ dynamic CTA imaging. The main objeCTive of this study was to assess the temporal resolution of dynamic CTA in discriminating various phases of rapid and slow time-dependent neurovascular pathologies in animal models. MATERIALS AND METHODS: Animal models were created to assess phasic blood flow, subclavian steal phenomena, saccular aneurysms, and neuroperfusion under protocols approved by the SRAC. Animals with progressively increasing heart rate—Macaca sylvanus (∼100 bpm), OryCTolagus cuniculus (NZW rabbit) (∼150 bpm), Rattus norvegicus (∼300 bpm), Mus musculus (∼500 bpm)—were imaged to challenge the temporal resolution of the system. FpVCT, a research prototype with a 25 × 25 × 18 cm coverage, was used for dynamic imaging with the gantry rotation time varying from 3 to 5 seconds. Volumetric datasets with 50% temporal overlap were reconstruCTed; 4D datasets were analyzed by using the Leonardo workstation. RESULTS: Dynamic imaging by using fpVCT was capable of demonstrating the following phenomena: 1) subclavian steal in rabbits (ΔT ≅ 3–4 seconds); 2) arterial, parenchymal, and venous phases of blood flow in mice (ΔT ≅ 2 seconds), rabbits (ΔT ≅ 3–4 seconds), and Macaca sylvanus (ΔT ≅ 3–4 seconds); 3) sequential enhancement of the right and left side of the heart in Macaca sylvanus and white rabbits (ΔT ≅ 2 seconds); and 4) different times of the peak opacification of cervical and intracranial arteries, venous sinuses, and the jugular veins in these animals (smallest, ΔT ≅ 1.5–2 seconds). The perfusion imaging in all animals tested was limited due to the fast transit time through the brain and the low contrast resolution of fpVCT. CONCLUSIONS: Dynamic imaging by using fpVCT can distinguish temporal processes separated by >1.5 seconds. Neurovascular pathologies with a time constant >1.5 seconds can be evaluated noninvasively by using fpVCT.
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distal radius in adolescent girls with anorexia nervosa trabecular struCTure analysis with high resolution flat panel Volume CT
Radiology, 2008Co-Authors: Miriam A Bredella, Arnold Cheung, Madhusmita Misra, Karen K Miller, Ijad Madisch, Ammar Sarwar, Anne Klibanski, Rajiv GuptaAbstract:Purpose: To examine trabecular microarchiteCTure with high-resolution flat-panel Volume computed tomography (CT) and bone mineral density (BMD) with dual-energy x-ray absorptiometry (DXA) in adolescent girls with anorexia nervosa (AN) and to compare these results with those in normal-weight control subjeCTs. Materials and Methods: The study was approved by the institutional review board and complied with HIPAA guidelines. Informed consent was obtained. Twenty adolescent girls, 10 with mild AN (mean age, 15.9 years; range, 13–18 years) and 10 age- and sex-matched normal-weight control subjeCTs (mean age, 15.9 years; range, 12–18 years) underwent flat-panel Volume CT of distal radius to determine apparent trabecular bone Volume fraCTion (BV/TV), apparent trabecular number (TbN), apparent trabecular thickness (TbTh), and apparent trabecular separation (TbSp). All subjeCTs underwent DXA of spine, hip, and whole body to determine BMD and body composition. The means and standard deviations (SDs) of struCTure parameters were calculated for AN and control groups. Groups were compared (Student t test). Linear regression analysis was performed. Results: AN subjeCTs compared with control subjeCTs, respeCTively, showed significantly lower mean values for BV/TV (0.37% ± 0.05 [SD] vs 0.46% ± 0.03, P = .0002) and TbTh (0.31 mm ± 0.03 vs 0.39 mm ± 0.03, P < .0001) and higher mean values for TbSp (0.54 mm ± 0.13 vs 0.44 mm ± 0.04, P = .02). TbN was lower in AN subjeCTs than in control subjeCTs, but the difference was not significant (1.17 mm−3 ± 0.15 vs 1.22 mm−3 ± 0.07, P = .43). There was no significant difference in BMD between AN and control subjeCTs. BMD parameters showed positive correlation with BV/TV and TbTh in the control group (r = 0.55–0.84, P = .05–.01) but not in AN patients. Conclusion: Flat-panel Volume CT is effeCTive in evaluation of trabecular struCTure in adolescent girls with AN and demonstrates that bone struCTure is abnormal in these patients compared with that in normal-weight control subjeCTs despite normal BMD. © RSNA, 2008
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flat panel Volume CT fundamental principles technology and applications
Radiographics, 2008Co-Authors: Rajiv Gupta, Michael Grasruck, Soenke H. Bartling, Thomas Flohr, Bernhard Schmidt, Arnold Cheung, Jennifer B Lisauskas, Christianne Leidecker, Thomas J BradyAbstract:Flat-panel Volume computed tomography (CT) systems have an innovative design that allows coverage of a large Volume per rotation, fluoroscopic and dynamic imaging, and high spatial resolution that permits visualization of complex human anatomy such as fine temporal bone struCTures and trabecular bone architeCTure. In simple terms, flat-panel Volume CT scanners can be thought of as conventional multideteCTor CT scanners in which the deteCTor rows have been replaced by an area deteCTor. The flat-panel deteCTor has wide z-axis coverage that enables imaging of entire organs in one axial acquisition. Its fluoroscopic and angiographic capabilities are useful for intraoperative and vascular applications. Furthermore, the high-Volume coverage and continuous rotation of the deteCTor may enable depiCTion of dynamic processes such as coronary blood flow and whole-brain perfusion. Other applications in which flat-panel Volume CT may play a role include small-animal imaging, nondestruCTive testing in animal survival surgeries, and tissue-engineering experiments. Such versatility has led some to prediCT that flat-panel Volume CT will gain importance in interventional and intraoperative applications, especially in specialties such as cardiac imaging, interventional neuroradiology, orthopedics, and otolaryngology. However, the contrast resolution of flat-panel Volume CT is slightly inferior to that of multideteCTor CT, a higher radiation dose is needed to achieve a comparable signal-to-noise ratio, and a slower scintillator results in a longer scanning time.
Thomas J Brady - One of the best experts on this subject based on the ideXlab platform.
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temporal resolution of dynamic angiography using flat panel Volume CT in vivo evaluation of time dependent vascular pathologies
American Journal of Neuroradiology, 2011Co-Authors: Rajiv Gupta, Michael Grasruck, Christianne Leidecker, Amit Mehndiratta, Alim P Mitha, Christopher S Ogilvy, Thomas J BradyAbstract:BACKGROUND AND PURPOSE: Recently introduced fpVCT scanners can capture Volumetric (4D) time-varying projeCTions enabling whole-organ dynamic CTA imaging. The main objeCTive of this study was to assess the temporal resolution of dynamic CTA in discriminating various phases of rapid and slow time-dependent neurovascular pathologies in animal models. MATERIALS AND METHODS: Animal models were created to assess phasic blood flow, subclavian steal phenomena, saccular aneurysms, and neuroperfusion under protocols approved by the SRAC. Animals with progressively increasing heart rate—Macaca sylvanus (∼100 bpm), OryCTolagus cuniculus (NZW rabbit) (∼150 bpm), Rattus norvegicus (∼300 bpm), Mus musculus (∼500 bpm)—were imaged to challenge the temporal resolution of the system. FpVCT, a research prototype with a 25 × 25 × 18 cm coverage, was used for dynamic imaging with the gantry rotation time varying from 3 to 5 seconds. Volumetric datasets with 50% temporal overlap were reconstruCTed; 4D datasets were analyzed by using the Leonardo workstation. RESULTS: Dynamic imaging by using fpVCT was capable of demonstrating the following phenomena: 1) subclavian steal in rabbits (ΔT ≅ 3–4 seconds); 2) arterial, parenchymal, and venous phases of blood flow in mice (ΔT ≅ 2 seconds), rabbits (ΔT ≅ 3–4 seconds), and Macaca sylvanus (ΔT ≅ 3–4 seconds); 3) sequential enhancement of the right and left side of the heart in Macaca sylvanus and white rabbits (ΔT ≅ 2 seconds); and 4) different times of the peak opacification of cervical and intracranial arteries, venous sinuses, and the jugular veins in these animals (smallest, ΔT ≅ 1.5–2 seconds). The perfusion imaging in all animals tested was limited due to the fast transit time through the brain and the low contrast resolution of fpVCT. CONCLUSIONS: Dynamic imaging by using fpVCT can distinguish temporal processes separated by >1.5 seconds. Neurovascular pathologies with a time constant >1.5 seconds can be evaluated noninvasively by using fpVCT.
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flat panel Volume CT fundamental principles technology and applications
Radiographics, 2008Co-Authors: Rajiv Gupta, Michael Grasruck, Soenke H. Bartling, Thomas Flohr, Bernhard Schmidt, Arnold Cheung, Jennifer B Lisauskas, Christianne Leidecker, Thomas J BradyAbstract:Flat-panel Volume computed tomography (CT) systems have an innovative design that allows coverage of a large Volume per rotation, fluoroscopic and dynamic imaging, and high spatial resolution that permits visualization of complex human anatomy such as fine temporal bone struCTures and trabecular bone architeCTure. In simple terms, flat-panel Volume CT scanners can be thought of as conventional multideteCTor CT scanners in which the deteCTor rows have been replaced by an area deteCTor. The flat-panel deteCTor has wide z-axis coverage that enables imaging of entire organs in one axial acquisition. Its fluoroscopic and angiographic capabilities are useful for intraoperative and vascular applications. Furthermore, the high-Volume coverage and continuous rotation of the deteCTor may enable depiCTion of dynamic processes such as coronary blood flow and whole-brain perfusion. Other applications in which flat-panel Volume CT may play a role include small-animal imaging, nondestruCTive testing in animal survival surgeries, and tissue-engineering experiments. Such versatility has led some to prediCT that flat-panel Volume CT will gain importance in interventional and intraoperative applications, especially in specialties such as cardiac imaging, interventional neuroradiology, orthopedics, and otolaryngology. However, the contrast resolution of flat-panel Volume CT is slightly inferior to that of multideteCTor CT, a higher radiation dose is needed to achieve a comparable signal-to-noise ratio, and a slower scintillator results in a longer scanning time.
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experimental flat panel high spatial resolution Volume CT of the temporal bone
American Journal of Neuroradiology, 2004Co-Authors: Rajiv Gupta, S Bartling, Samit Kumar Basu, W R Ross, H Becker, Armin Horst Pfoh, Thomas J Brady, Hugh D CurtinAbstract:BACKGROUND AND PURPOSE: A CT scanner employing a digital flat-panel deteCTor is capable of very high spatial resolution as compared with a multi-seCTion CT (MSCT) scanner. Our purpose was to determine how well a prototypical Volume CT (VCT) scanner with a flat-panel deteCTor system defines fine struCTures in temporal bone. METHODS: Four partially manipulated temporal-bone specimens were imaged by use of a prototypical cone-beam VCT scanner with a flat-panel deteCTor system at an isometric resolution of 150 μm at the isocenter. These specimens were also depiCTed by state-of-the-art multiseCTion CT (MSCT). Forty-two struCTures imaged by both scanners were qualitatively assessed and rated, and scores assigned to VCT findings were compared with those of MSCT. RESULTS: Qualitative assessment of anatomic struCTures, lesions, cochlear implants, and middle-ear hearing aids indicated that image quality was significantly better with VCT ( P < .001). StruCTures near the spatial-resolution limit of MSCT (e.g., bony covering of the tympanic segment of the facial canal, the incudo-stapedial joint, the proximal vestibular aqueduCT, the interscalar septum, and the modiolus) had higher contrast and less partial-Volume effeCT with VCT. CONCLUSION: The flat-panel prototype provides better definition of fine osseous struCTures of temporal bone than that of currently available MSCT scanners. This study provides impetus for further research in increasing spatial resolution beyond that offered by the current state-of-the-art scanners.
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experimental flat panel high spatial resolution Volume CT of the temporal bone
American Journal of Neuroradiology, 2004Co-Authors: Rajiv Gupta, Soenke H. Bartling, Samit Kumar Basu, W R Ross, H Becker, Armin Horst Pfoh, Thomas J Brady, Hugh D CurtinAbstract:BACKGROUND AND PURPOSE: A CT scanner employing a digital flat-panel deteCTor is capable of very high spatial resolution as compared with a multi-seCTion CT (MSCT) scanner. Our purpose was to determine how well a prototypical Volume CT (VCT) scanner with a flat-panel deteCTor system defines fine struCTures in temporal bone. METHODS: Four partially manipulated temporal-bone specimens were imaged by use of a prototypical cone-beam VCT scanner with a flat-panel deteCTor system at an isometric resolution of 150 μm at the isocenter. These specimens were also depiCTed by state-of-the-art multiseCTion CT (MSCT). Forty-two struCTures imaged by both scanners were qualitatively assessed and rated, and scores assigned to VCT findings were compared with those of MSCT. RESULTS: Qualitative assessment of anatomic struCTures, lesions, cochlear implants, and middle-ear hearing aids indicated that image quality was significantly better with VCT (P CONCLUSION: The flat-panel prototype provides better definition of fine osseous struCTures of temporal bone than that of currently available MSCT scanners. This study provides impetus for further research in increasing spatial resolution beyond that offered by the current state-of-the-art scanners.
Amit Mehndiratta - One of the best experts on this subject based on the ideXlab platform.
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high resolution dynamic angiography using flat panel Volume CT feasibility demonstration for neuro and lower limb vascular applications
European Radiology, 2015Co-Authors: Michael Grasruck, Amit Mehndiratta, James D Rabinov, Eric C Liao, David Crandell, Rajiv GuptaAbstract:ObjeCTive This paper evaluates a prototype flat-panel Volume CT (fpVCT) for dynamic in vivo imaging in a variety of neurovascular and lower limb applications.
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temporal resolution of dynamic angiography using flat panel Volume CT in vivo evaluation of time dependent vascular pathologies
American Journal of Neuroradiology, 2011Co-Authors: Rajiv Gupta, Michael Grasruck, Christianne Leidecker, Amit Mehndiratta, Alim P Mitha, Christopher S Ogilvy, Thomas J BradyAbstract:BACKGROUND AND PURPOSE: Recently introduced fpVCT scanners can capture Volumetric (4D) time-varying projeCTions enabling whole-organ dynamic CTA imaging. The main objeCTive of this study was to assess the temporal resolution of dynamic CTA in discriminating various phases of rapid and slow time-dependent neurovascular pathologies in animal models. MATERIALS AND METHODS: Animal models were created to assess phasic blood flow, subclavian steal phenomena, saccular aneurysms, and neuroperfusion under protocols approved by the SRAC. Animals with progressively increasing heart rate—Macaca sylvanus (∼100 bpm), OryCTolagus cuniculus (NZW rabbit) (∼150 bpm), Rattus norvegicus (∼300 bpm), Mus musculus (∼500 bpm)—were imaged to challenge the temporal resolution of the system. FpVCT, a research prototype with a 25 × 25 × 18 cm coverage, was used for dynamic imaging with the gantry rotation time varying from 3 to 5 seconds. Volumetric datasets with 50% temporal overlap were reconstruCTed; 4D datasets were analyzed by using the Leonardo workstation. RESULTS: Dynamic imaging by using fpVCT was capable of demonstrating the following phenomena: 1) subclavian steal in rabbits (ΔT ≅ 3–4 seconds); 2) arterial, parenchymal, and venous phases of blood flow in mice (ΔT ≅ 2 seconds), rabbits (ΔT ≅ 3–4 seconds), and Macaca sylvanus (ΔT ≅ 3–4 seconds); 3) sequential enhancement of the right and left side of the heart in Macaca sylvanus and white rabbits (ΔT ≅ 2 seconds); and 4) different times of the peak opacification of cervical and intracranial arteries, venous sinuses, and the jugular veins in these animals (smallest, ΔT ≅ 1.5–2 seconds). The perfusion imaging in all animals tested was limited due to the fast transit time through the brain and the low contrast resolution of fpVCT. CONCLUSIONS: Dynamic imaging by using fpVCT can distinguish temporal processes separated by >1.5 seconds. Neurovascular pathologies with a time constant >1.5 seconds can be evaluated noninvasively by using fpVCT.
Ruola Ning - One of the best experts on this subject based on the ideXlab platform.
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flat panel deteCTor based cone beam Volume CT breast imaging phantom and specimen study
Medical Imaging 2002: Physics of Medical Imaging, 2002Co-Authors: Ruola Ning, Biao Chen, David Conover, Linda Schiffhauer, Jeanne Cullinan, Yi Ning, Arvin E RobinsonAbstract:Conventional film-screen mammography is the most effeCTive tool for the early deteCTion of breast cancer currently available. However, conventional mammography has relatively low sensitivity to deteCT small breast cancers (under several millimeters) owing to an overlap in the appearances of benign and malignant lesions, and surrounding struCTure. The limitations accompanying conventional mammography is to be addressed by incorporating a cone beam Volume CT imaging technique with a recently developed flat panel deteCTor. A computer simulation study has been performed to prove the feasibility of developing a flat panel deteCTor-based cone beam Volume CT breast imaging (FPD-CBVCTBI) technique. In this study, a phantom and specimen experiment is performed to confirm the findings in the computer simulation using the current prototype cone beam Volume CT scanner. The results indicate that the CBVCTBI technique effeCTively removes struCTure overlap and significantly improves the deteCTability of small breast tumors. More importantly, the results also demonstrate the patient dose level required for FPD-based CBVCTBI to deteCT a small tumor (under 5 mm) and a small calcification is less than or equal to that of conventional mammography. The results from this study suggest that FPD-CBVCTBI is a potentially powerful breast-imaging tool.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstraCT is permitted for personal use only.
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cone beam Volume CT breast imaging feasibility study
Medical Physics, 2002Co-Authors: Biao Chen, Ruola NingAbstract:X-ray projeCTion mammography, using a film/screen combination, or digital techniques, has proven to be the most effeCTive imaging modality currently available for early deteCTion of breast cancer. However, the inherent superimposition of struCTures makes a small carcinoma (a few millimeters in size) difficult to deteCT when it is occult or in dense breasts, leading to a high false-positive biopsy rate. Cone-beam x-ray-projeCTion-based Volume imaging using flat panel deteCTors (FPDs) may allow obtaining three-dimensional breast images, resulting in more accurate diagnosis of struCTures and patterns of lesions while eliminating the hard compression of breasts. This article presents a novel cone-beam Volume computed tomographic breast imaging (CBVCTBI) technique based on the above techniques. Through a variety of computer simulations, the key issues of the system and imaging techniques were addressed, including the x-ray imaging geometry and corresponding reconstruCTion algorithms, x-ray charaCTeristics of breast tissue and lesions, x-ray setting techniques, the absorbed dose estimation, and the quantitative effeCT of x-ray scattering on image quality. The preliminary simulation results support the proposed CVBCTBI modality for breast imaging in respeCT to its feasibility and praCTicability. The absorbed dose level is comparable to that of current mammography and will not be a prominent problem for this imaging technique. Compared to conventional mammography, the proposed imaging technique with isotropic spatial resolution will potentially provide significantly better low-contrast deteCTability of breast tumors and more accurate location of breast lesions.
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a cone beam filtered backprojeCTion cb fbp reconstruCTion algorithm for a circle plus two arc orbit
Medical Physics, 2001Co-Authors: Xiangyang Tang, Ruola NingAbstract:The circle-plus-arc orbit possesses advantages over other "circle-plus" orbits for the application of x-ray cone beam (CB) Volume CT in image-guided interventional procedures requiring intraoperative imaging, in which movement of the patient table is to be avoided. A CB circle-plus-two-arc orbit satisfying the data sufficiency condition and a filtered backprojeCTion (FBP) algorithm to reconstruCT longitudinally unbounded objeCTs is presented here. In the circle suborbit, the algorithm employs Feldkamp's formula and another FBP implementation. In the arc suborbits, an FBP solution is obtained originating from Grangeat's formula, and the reconstruCTion computation is significantly reduced using a window funCTion to exclude redundancy in Radon domain. The performance of the algorithm has been thoroughly evaluated through computer-simulated phantoms and preliminarily evaluated through experimental data, revealing that the algorithm can regionally reconstruCT longitudinally unbounded objeCTs exaCTly and efficiently, is insensitive to the variation of the angle sampling interval along the arc suborbits, and is robust over praCTical x-ray quantum noise. The algorithm's merits include: only 1D filtering is implemented even in a 3D reconstruCTion, only separable 2D interpolation is required to accomplish the CB backprojeCTion, and the algorithm struCTure is appropriate for parallel computation.
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cone beam Volume CT image artifaCTs caused by defeCTive cells in x ray flat panel imagers and the artifaCT removal using a wavelet analysis based algorithm
Medical Physics, 2001Co-Authors: Xiangyang Tang, Ruola Ning, David ConoverAbstract:The application of x-ray flat panel imagers (FPIs) in cone beam Volume CT (CBVCT) has attraCTed increasing attention. However, due to a deficient semiconduCTor array manufaCTuring process, defeCTive cells unavoidably exist in x-ray FPIs. These defeCTive cells cause their corresponding image pixels in a projeCTion image to behave abnormally in signal gray level, and result in severe streak and ring artifaCTs in a CBVCT imagereconstruCTed from the projeCTion images. Since a three-dimensional (3-D) back-projeCTion is involved in CBVCT, the formation of the streak and ring artifaCTs is different from that in the two-dimensional (2-D) fan beam CT. In this paper, a geometric analysis of the abnormality propagation in the 3D back-projeCTion is presented, and the morphology of the streak and ring artifaCTs caused by the abnormality propagation is investigated through both computer simulation and phantom studies. In order to calibrate those artifaCTs, a 2D wavelet-analysis-based statistical approach to correCT the abnormal pixels is proposed. The approach consists of three steps: (1) the location-invariant defeCTive cells in an x-ray FPI are recognized by applying 2-D wavelet analysis on flat-field images, and a comprehensive defeCTive cell template is acquired; (2) based upon the template, the abnormal signal gray level of the projeCTion image pixels corresponding to the location-invariant defeCTive cells is replaced with the interpolation of that of their normal neighbor pixels; (3) that corresponding to the isolated location-variant defeCTive cells are correCTed using a narrow-windowed median filter. The CBVCT images of a CT low-contrast phantom are employed to evaluate this proposed approach, showing that the streak and ring artifaCTs can be reliably eliminated. The novelty and merit of the approach are the incorporation of the wavelet analysis whose intrinsic multi-resolution analysis and localizability make the recognition algorithm robust under variable x-ray exposure levels between 30% and 70% of the dynamic range of an x-ray FPI.
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flat panel deteCTor based cone beam Volume CT angiography imaging system evaluation
IEEE Transactions on Medical Imaging, 2000Co-Authors: Ruola Ning, Biao Chen, David Conover, Xiangyang Tang, Yi NingAbstract:Preliminary evaluation of recently developed large-area flat panel deteCTors (FPDs) indicates that FPDs have some potential advantages: compaCTness, absence of geometric distortion and veiling glare with the benefits of high resolution, high deteCTive quantum efficiency (DQE), high frame rate and high dynamic range, small image lag (<1%), and excellent linearity (/spl sim/1%). The advantages of the new FPD make it a promising candidate for cone-beam Volume computed tomography (CT) angiography (CBVCTA) imaging. The purpose of this study is to charaCTerize a prototype FPD-based imaging system for CBVCTA applications. A prototype FPD-based CBVCTA imaging system has been designed and construCTed around a modified GE 8800 CT scanner. This system is evaluated for a CBVCTA imaging task in the head and neck using four phantoms and a frozen rat. The system is first charaCTerized in terms of linearity and dynamic range of the deteCTor. Then, the optimal seleCTion of kVps for CBVCTA is determined and the effeCT of image lag and scatter on the image quality of the CBVCTA system is evaluated. Next, low-contrast resolution and high-contrast spatial resolution are measured. Finally, the example reconstruCTion images of a frozen rat are presented. The results indicate that the FPD-based CBVCT can achieve 2.75-1p/mm spatial resolution at 0% modulation transfer funCTion (MTF) and provide more than enough low-contrast resolution for intravenous CBVCTA imaging in the head and neck with clinically acceptable entrance exposure level. The results also suggest that to use an FPD for large cone-angle applications, such as body angiography, further investigations are required.
Thomas Flohr - One of the best experts on this subject based on the ideXlab platform.
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lowering kilovoltage to reduce radiation dose in contrast enhanced abdominal CT initial assessment of a prototype automated kilovoltage seleCTion tool
American Journal of Roentgenology, 2012Co-Authors: David M Hough, Bernhard Schmidt, Joel G Fletcher, Katharine L Grant, Jeff L Fidler, Lifeng Yu, Jennifer R Geske, Rickey E Carter, Rainer Raupach, Thomas FlohrAbstract:OBJECTIVE. The purpose of this study was to determine whether the use of an automated CT kilovoltage (kV) seleCTion tool (Auto kV) can result in lower radiation dose without sacrificing image quality in contrast-enhanced abdominopelvic CT. MATERIALS AND METHODS. Tube potential, radiation dose, and iodine contrast-to-noise ratio (CNR) were retrospeCTively evaluated in 36 patients who underwent abdominopelvic CT with Auto kV, and compared with results from size-matched control patients using identical protocols. Two radiologists evaluated image quality (sharpness, noise, and diagnostic confidence) blinded to kV. Volume CT dose index (CTDIvol) was also compared with what each patient would have received from scanning at 120 kV. RESULTS. Mean (SD) CTDIvol was 16.0 (4.4) mGy after Auto kV versus 19.5 (4.0) mGy using standard 120-kV prescription and was 19.3 (6.0) mGy in control subjeCTs (yielding dose reduCTions of 18.0% and 17.2%, respeCTively; p < 0.001 for both). Thirty of 36 patients were scanned at 100 kV...
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flat panel Volume CT fundamental principles technology and applications
Radiographics, 2008Co-Authors: Rajiv Gupta, Michael Grasruck, Soenke H. Bartling, Thomas Flohr, Bernhard Schmidt, Arnold Cheung, Jennifer B Lisauskas, Christianne Leidecker, Thomas J BradyAbstract:Flat-panel Volume computed tomography (CT) systems have an innovative design that allows coverage of a large Volume per rotation, fluoroscopic and dynamic imaging, and high spatial resolution that permits visualization of complex human anatomy such as fine temporal bone struCTures and trabecular bone architeCTure. In simple terms, flat-panel Volume CT scanners can be thought of as conventional multideteCTor CT scanners in which the deteCTor rows have been replaced by an area deteCTor. The flat-panel deteCTor has wide z-axis coverage that enables imaging of entire organs in one axial acquisition. Its fluoroscopic and angiographic capabilities are useful for intraoperative and vascular applications. Furthermore, the high-Volume coverage and continuous rotation of the deteCTor may enable depiCTion of dynamic processes such as coronary blood flow and whole-brain perfusion. Other applications in which flat-panel Volume CT may play a role include small-animal imaging, nondestruCTive testing in animal survival surgeries, and tissue-engineering experiments. Such versatility has led some to prediCT that flat-panel Volume CT will gain importance in interventional and intraoperative applications, especially in specialties such as cardiac imaging, interventional neuroradiology, orthopedics, and otolaryngology. However, the contrast resolution of flat-panel Volume CT is slightly inferior to that of multideteCTor CT, a higher radiation dose is needed to achieve a comparable signal-to-noise ratio, and a slower scintillator results in a longer scanning time.
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Ultra-high resolution flat-panel Volume CT: Fundamental principles, design architeCTure, and system charaCTerization
European Radiology, 2006Co-Authors: Rajiv Gupta, Michael Grasruck, Soenke H. Bartling, Christoph Suess, Klaus Stierstorfer, Tom Brady, Bernhard Schmidt, Stefan Popescu, Thomas FlohrAbstract:Digital flat-panel-based Volume CT (VCT) represents a unique design capable of ultra-high spatial resolution, direCT Volumetric imaging, and dynamic CT scanning. This innovation, when fully developed, has the promise of opening a unique window on human anatomy and physiology. For example, the Volumetric coverage offered by this technology enables us to observe the perfusion of an entire organ, such as the brain, liver, or kidney, tomographically (e.g., after a transplant or ischemic event). By virtue of its higher resolution, one can direCTly visualize the trabecular struCTure of bone. This paper describes the basic design architeCTure of VCT. Three key technical challenges, viz., scatter correCTion, dynamic range extension, and temporal resolution improvement, must be addressed for successful implementation of a VCT scanner. How these issues are solved in a VCT prototype and the modifications necessary to enable ultra-high resolution Volumetric scanning are described. The fundamental principles of scatter correCTion and dose reduCTion are illustrated with the help of an aCTual prototype. The image quality metrics of this prototype are charaCTerized and compared with a multi-deteCTor CT (MDCT).
