Rajiv Gupta - Academia.edu (original) (raw)

Papers by Rajiv Gupta

BACKGROUND AND PURPOSE: Systematic facial mutilations during mummification have never been descri... more BACKGROUND AND PURPOSE: Systematic facial mutilations during mummification have never been described before. The purpose of this work was to study a wrapped mummified head using high-resolution CT scanning. MATERIALS AND METHODS: An isolated mummified head from the Egyptian Middle Kingdom was scanned at 200 m isotropic resolution. A prototype flat panel CT scanner was used to generate 800 nonoverlapping CT sections at 120 kV and 50 mA. This dataset was analyzed to discern various surgical alterations during mummification. RESULTS: There were large defects in the cribriform plate and the posterior fossa. Systematic mutilations of the facial bones and mandible, involving the anterior and inferior walls of the maxillary sinuses, the floor of both orbits, and the zygomatic arches with contiguous segments of the zygomas, were demonstrated. The coronoid processes of both mandibles had been sharply excised and the articular tubercles of the temporomandibular joints fractured. CONCLUSION: D...

Scientific Reports, 2019

Dual-energy CT (DECT) was introduced to address the inability of conventional single-energy compu... more Dual-energy CT (DECT) was introduced to address the inability of conventional single-energy computed tomography (SECT) to distinguish materials with similar absorbances but different elemental compositions. However, material decomposition algorithms based purely on the physics of the underlying attenuation process have several limitations, leading to low signal-to-noise ratio (SNR) in the derived material-specific images. To overcome these, we trained a convolutional neural network (CNN) to develop a framework to reconstruct non-contrast SECT images from DECT scans. We show that the traditional physics-based decomposition algorithms do not bring to bear the full information content of the image data. A CNN that leverages the underlying physics of the DECT image generation process as well as the anatomic information gleaned via training with actual images can generate higher fidelity processed DECT images.

Cancers, Jan 6, 2015

There is an increasing body of evidence establishing the advantages of dual-energy CT (DECT) for ... more There is an increasing body of evidence establishing the advantages of dual-energy CT (DECT) for evaluation of head and neck squamous cell carcinoma (HNSCC). Focusing on a single-source DECT system with fast kVp switching, we will review the principles behind DECT and associated post-processing steps that make this technology especially suitable for HNSCC evaluation and staging. The article will review current applications of DECT for evaluation of HNSCC including use of different reconstructions to improve tumor conspicuity, tumor-normal soft tissue interface, accuracy of invasion of critical structures such as thyroid cartilage, and reduce dental artifact. We will provide a practical approach for DECT implementation into routine clinical use and a multi-parametric approach for scan interpretation based on the experience at our institution. The article will conclude with a brief overview of potential future applications of the technique.

PloS one, 2015

X-ray phase-contrast tomography can significantly increase the contrast-resolution of conventiona... more X-ray phase-contrast tomography can significantly increase the contrast-resolution of conventional attenuation-contrast imaging, especially for soft-tissue structures that have very similar attenuation. Just as in attenuation-based tomography, phase contrast tomography requires a linear dependence of aggregate beam direction on the incremental direction alteration caused by individual voxels along the path of the X-ray beam. Dense objects such as calcifications in biological specimens violate this condition. There are extensive beam deflection artefacts in the vicinity of such structures because they result in large distortion of wave front due to the large difference of refractive index; for such large changes in beam direction, the transmittance of the silicon analyzer crystal saturates and is no longer linearly dependent on the angle of refraction. This paper describes a method by which these effects can be overcome and excellent soft-tissue contrast of phase tomography can be pr...

Scientific reports, Jan 14, 2015

X-ray phase-contrast imaging (XPCI) can dramatically improve soft tissue contrast in X-ray medica... more X-ray phase-contrast imaging (XPCI) can dramatically improve soft tissue contrast in X-ray medical imaging. Despite worldwide efforts to develop novel XPCI systems, a numerical framework to rigorously predict the performance of a clinical XPCI system at a human scale is not yet available. We have developed such a tool by combining a numerical anthropomorphic phantom defined with non-uniform rational B-splines (NURBS) and a wave optics-based simulator that can accurately capture the phase-contrast signal from a human-scaled numerical phantom. Using a synchrotron-based, high-performance XPCI system, we provide qualitative comparison between simulated and experimental images. Our tool can be used to simulate the performance of XPCI on various disease entities and compare proposed XPCI systems in an unbiased manner.

AJNR. American journal of neuroradiology, 2004

A CT scanner employing a digital flat-panel detector is capable of very high spatial resolution a... more 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. 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 microm 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. 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 th...

Journal of Medical Devices, 2012

This paper describes the design of a compact, lightweight CT-compatible, drill-press that is desi... more This paper describes the design of a compact, lightweight CT-compatible, drill-press that is designed to be used in either a hand-held or stand-alone mode to assist with percutaneous bone based interventions. Previous medical drilling tools that have been developed have a metal structure and typically have one actuator for advancing the drill (feed) and another for rotating it (speed). After defining the device functional requirements and specifications, a deterministic design process was followed to generate several design concepts that were then evaluated based on their ability to satisfy the functional requirements. A final concept that uses a custom screw-spline to achieve helical motion of a shaft that is attached to a standard orthopedic drill was selected for prototyping. The design uses a single actuator to drive both the screw and spline nuts through two different gear ratios, resulting in a fixed ratio between the feed and speed. Apart from the motor which is placed away f...

Stroke, 2013

Background and Purpose— Contrast medium extravasation (CE) in intracerebral hemorrhage (ICH) is a... more Background and Purpose— Contrast medium extravasation (CE) in intracerebral hemorrhage (ICH) is a marker of ongoing bleeding and a predictor of hematoma expansion. The aims of the study were to establish an ICH model in which CE can be quantified, characterized in ICH during warfarin and dabigatran anticoagulation, and to evaluate effects of prothrombin complex concentrates on CE in warfarin-associated ICH. Methods— CD1-mice were pretreated orally with warfarin, dabigatran, or vehicle. Prothrombin complex concentrates were administered in a subgroup of warfarin-treated mice. ICH was induced by stereotactic injection of collagenase VIIs into the right striatum. Contrast agent (350 μL Isovue 370 mg/mL) was injected intravenously after ICH induction (2–3.5 hours). Thirty minutes later, mice were euthanized, and CE was measured by quantifying the iodine content in the hematoma using dual-energy computed tomography. Results— The optimal time point for contrast injection was found to be 3...

RadioGraphics, 2008

Flat-panel volume computed tomography (CT) systems have an innovative design that allows coverage... more 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. ©

Journal of The Royal Society Interface, 2013

Engineered cartilage is a promising option for auricular reconstruction. We have previously demon... more Engineered cartilage is a promising option for auricular reconstruction. We have previously demonstrated that a titanium wire framework within a composite collagen ear-shaped scaffold helped to maintain the gross dimensions of the engineered ear after implantation, resisting the deformation forces encountered during neocartilage maturation and wound healing. The ear geometry was redesigned to achieve a more accurate aesthetic result when implanted subcutaneously in a nude rat model. A non-invasive method was developed to assess size and shape changes of the engineered ear in three dimensions. Computer models of the titanium framework were obtained from CT scans before and after implantation . Several parameters were measured including the overall length, width and depth, the minimum intrahelical distance and overall curvature values for each beam section within the framework. Local curvature values were measured to gain understanding of the bending forces experienced by the framewor...

Tissue engineering. Part A, 2009

Regenerative technology promises to alleviate the problem of limited donor supply for bone or org... more Regenerative technology promises to alleviate the problem of limited donor supply for bone or organ transplants. Most expensive and time consuming is cell expansion in laboratories. We propose a method of magnetically enriched osteoprogenitor stem cells, dispersed in self-assembling hydrogels and applied onto new ultra-high resolution, jet-based, three-dimensional printing of living human bone in a single-step for in situ bone regeneration. Human bone marrow-derived mesenchymal stem cells (hBMSCs) were enriched with CD 117+ cells, dispersed in different collagen I and RAD 16I hydrogel mixes, and applied onto three-dimensional printed btricalcium phosphate=poly(lactic-co-glycolic acid) scaffolds, printed from ultra-high-resolution volumetric CT images of a human thumb. Constructs were directly implanted subcutaneously into nude mice for 6 weeks. In vivo radiographic volumetric CT scanning and histological evaluations were performed at 1, 2, 4, and 6 weeks, and expression of bone-spec...

Bone, 2006

Trabecular bone is a material of choice for reconstruction after trauma and tumor resection and f... more Trabecular bone is a material of choice for reconstruction after trauma and tumor resection and for correction of congenital defects. Autologous bone grafts are available in limited shapes and sizes; significant donor site morbidity is another major disadvantage to this approach. To overcome these limitations, we used a tissue engineering approach to create bone replacements in vitro, combining bone-marrow-derived differentiated mesenchymal stem cells (MSCs) suspended in hydrogels and 3-dimensionally printed (3DP) porous scaffolds made of β-tricalcium-phosphate (β-TCP). The scaffolds provided support for the formation of bone tissue in collagen I, fibrin, alginate, and pluronic F127 hydrogels during culturing in oscillating and rotating dynamic conditions. Histological evaluation including toluidine blue, alkaline phosphatase, and von Kossa staining was done at 1, 2, 4, and 6 weeks. Radiographic evaluation and high-resolution volumetric CT (VCT) scanning, expression of bone-specific genes and biomechanical compression testing were performed at 6 weeks. Both culture conditions resulted in similar bone tissue formation. Histologically collagen I and fibrin hydrogels specimens had superior bone tissue, although radiopacities were detected only in collagen I samples. VCT scan revealed density values in all but the Pluronic F127 samples, with Houndsfield unit values comparable to native bone in collagen I and fibrin glue samples. Expression of bone-specific genes was significantly higher in the collagen I samples. Pluronic F127 hydrogel did not support formation of bone tissue. All samples cultured in dynamic oscillating conditions had slightly higher mechanical strength than under rotating conditions. Bone tissue can be successfully formed in vitro using constructs comprised of collagen I hydrogel, MSCs, and porous β-TCP scaffolds.

Bone, 2010

Osteopenia is a complication of anorexia nervosa (AN) associated with a two-to threefold increase... more Osteopenia is a complication of anorexia nervosa (AN) associated with a two-to threefold increase in fractures. Nutritional deficits and hormonal abnormalities are thought to mediate AN-induced bone loss. Alterations in bone microarchitecture may explain fracture risk independent of bone mineral density (BMD). Advances in CT imaging now allow for noninvasive evaluation of trabecular microstructure at peripheral sites in vivo. Few data are available regarding bone microarchitecture in AN. We therefore performed a cross-sectional study of 23 women (12 with AN and 11 healthy controls) to determine hormonal predictors of trabecular bone microarchitecture. Outcome measures included bone microarchitectural parameters at the ultradistal radius by flat panel Volume CT (fpVCT); BMD at the PA and lateral spine, total hip, femoral neck and ultradistal radius by dual energy X-ray absorptiometry (DXA); and IGF-I, leptin, estradiol, testosterone and free testosterone levels. Bone microarchitectural measures, including apparent (app.) bone volume fraction, app. trabecular thickness, and app. trabecular number, were reduced (p<0.03) and app. trabecular spacing was increased (p=0.02) in AN vs. controls. Decreased structural integrity at the ultradistal radius was associated with decreased BMD at all sites (p=0.05) except for total hip. IGF-I, leptin, testosterone and free testosterone levels predicted bone microarchitecture. All associations between both IGF-I and leptin levels and bone microarchitectural parameters, and most associations between androgen levels and microarchitecture remained significant after controlling for body mass index. We concluded that bone microarchitecture is abnormal in women with AN. Endogenous IGF-I, leptin and androgen levels predict bone microarchitecture independent of BMI.

Annals of Plastic Surgery, 2007

Traumatic amputation of a thumb with bone loss leaves a patient in severe disability. Reconstruct... more Traumatic amputation of a thumb with bone loss leaves a patient in severe disability. Reconstructive procedures are restricted by limited shape and have the disadvantage of severe donor-site morbidity. To overcome these limitations, we used a tissue engineering approach to create a distal thumb bone phalanx, combining magnetically sorted 133ϩ human mesenchymal stem cells (hMSCs) suspended in successful tested hydrogels for bone formation and porous 3-dimensionally printed scaffolds (3DP) in the shape of a distal thumb bone phalanx. Collagen I and fibrin glue hydrogels with suspended hMSCs were first histologically evaluated in vitro for bone formation after 6 weeks. Then 3DP scaffolds, made from a mix of osteoinductive and-conductive ␤-tricalciumphosphate (␤-TCP) and poly-caprolactone (PCL), with hydrogels and suspended hMSCs, were implanted into nude mice subcutaneously for 15 weeks. Histologic evaluation, high-resolution volumetric CT (VCT) scanning, and biomechanical testing confirmed formation of bonelike tissue. Both hydrogels with CD 133ϩ hMSCs on 3DP scaffolds supported bone formation. Collagen I resulted in radiologically better bone formation. Bone tissue can be successfully tissue engineered with CD 133ϩ hMSCs, collagen I hydrogels, and porous 3DP ␤-TCP/PCL scaffolds.

American Journal of Neuroradiology, 2008

BACKGROUND AND PURPOSE: Systematic facial mutilations during mummification have never been descri... more BACKGROUND AND PURPOSE: Systematic facial mutilations during mummification have never been described before. The purpose of this work was to study a wrapped mummified head using highresolution CT scanning. MATERIALS AND METHODS: An isolated mummified head from the Egyptian Middle Kingdom was scanned at 200 m isotropic resolution. A prototype flat panel CT scanner was used to generate 800 nonoverlapping CT sections at 120 kV and 50 mA. This dataset was analyzed to discern various surgical alterations during mummification. RESULTS: There were large defects in the cribriform plate and the posterior fossa. Systematic mutilations of the facial bones and mandible, involving the anterior and inferior walls of the maxillary sinuses, the floor of both orbits, and the zygomatic arches with contiguous segments of the zygomas, were demonstrated. The coronoid processes of both mandibles had been sharply excised and the articular tubercles of the temporomandibular joints fractured. CONCLUSION: Defects in the ethmoid and the posterior skull base are consistent with previous descriptions of excerebration. Mutilations of the facial skeleton and jaw, which are unrelated to the process of excerebration, have never been described previously. It is noteworthy that the osteotomies selectively include the insertions of the muscles of mastication. These mutilations apparently were designed for mobilization of lower jaw. The "Opening of the Mouth" ceremony, described in the ancient texts, would be difficult to perform in the presence of rigor mortis; it is probable that the observed osteotomies were performed to facilitate this ceremony. Our research suggests that by the Middle Kingdom, Egyptian embalmers had developed highly sophisticated surgical techniques that have not been appreciated previously. X-Ray Radiographs Radiographs of the mummified head were taken to study the highresolution projectional anatomy of the skull. Standard projectional x-ray views of the head were acquired to first look at the structure of the head. Morphometric measurements and the integrity (and lack of integrity) of various skull bones were established. Multidetector CT Detailed tomographic examination was undertaken to investigate the internal structure of the bones and to look inside the cranial vault by

American Journal of Otolaryngology, 1983

Tissue engineering. Part A, 2009

Regenerative technology promises to alleviate the problem of limited donor supply for bone or org... more Regenerative technology promises to alleviate the problem of limited donor supply for bone or organ transplants. Most expensive and time consuming is cell expansion in laboratories. We propose a method of magnetically enriched osteoprogenitor stem cells, dispersed in self-assembling hydrogels and applied onto new ultra-high resolution, jet-based, three-dimensional printing of living human bone in a single-step for in situ bone regeneration. Human bone marrow-derived mesenchymal stem cells (hBMSCs) were enriched with CD 117+ cells, dispersed in different collagen I and RAD 16I hydrogel mixes, and applied onto three-dimensional printed btricalcium phosphate=poly(lactic-co-glycolic acid) scaffolds, printed from ultra-high-resolution volumetric CT images of a human thumb. Constructs were directly implanted subcutaneously into nude mice for 6 weeks. In vivo radiographic volumetric CT scanning and histological evaluations were performed at 1, 2, 4, and 6 weeks, and expression of bone-spec...

BACKGROUND AND PURPOSE: Systematic facial mutilations during mummification have never been descri... more BACKGROUND AND PURPOSE: Systematic facial mutilations during mummification have never been described before. The purpose of this work was to study a wrapped mummified head using high-resolution CT scanning. MATERIALS AND METHODS: An isolated mummified head from the Egyptian Middle Kingdom was scanned at 200 m isotropic resolution. A prototype flat panel CT scanner was used to generate 800 nonoverlapping CT sections at 120 kV and 50 mA. This dataset was analyzed to discern various surgical alterations during mummification. RESULTS: There were large defects in the cribriform plate and the posterior fossa. Systematic mutilations of the facial bones and mandible, involving the anterior and inferior walls of the maxillary sinuses, the floor of both orbits, and the zygomatic arches with contiguous segments of the zygomas, were demonstrated. The coronoid processes of both mandibles had been sharply excised and the articular tubercles of the temporomandibular joints fractured. CONCLUSION: D...

Scientific Reports, 2019

Dual-energy CT (DECT) was introduced to address the inability of conventional single-energy compu... more Dual-energy CT (DECT) was introduced to address the inability of conventional single-energy computed tomography (SECT) to distinguish materials with similar absorbances but different elemental compositions. However, material decomposition algorithms based purely on the physics of the underlying attenuation process have several limitations, leading to low signal-to-noise ratio (SNR) in the derived material-specific images. To overcome these, we trained a convolutional neural network (CNN) to develop a framework to reconstruct non-contrast SECT images from DECT scans. We show that the traditional physics-based decomposition algorithms do not bring to bear the full information content of the image data. A CNN that leverages the underlying physics of the DECT image generation process as well as the anatomic information gleaned via training with actual images can generate higher fidelity processed DECT images.

Cancers, Jan 6, 2015

There is an increasing body of evidence establishing the advantages of dual-energy CT (DECT) for ... more There is an increasing body of evidence establishing the advantages of dual-energy CT (DECT) for evaluation of head and neck squamous cell carcinoma (HNSCC). Focusing on a single-source DECT system with fast kVp switching, we will review the principles behind DECT and associated post-processing steps that make this technology especially suitable for HNSCC evaluation and staging. The article will review current applications of DECT for evaluation of HNSCC including use of different reconstructions to improve tumor conspicuity, tumor-normal soft tissue interface, accuracy of invasion of critical structures such as thyroid cartilage, and reduce dental artifact. We will provide a practical approach for DECT implementation into routine clinical use and a multi-parametric approach for scan interpretation based on the experience at our institution. The article will conclude with a brief overview of potential future applications of the technique.

PloS one, 2015

X-ray phase-contrast tomography can significantly increase the contrast-resolution of conventiona... more X-ray phase-contrast tomography can significantly increase the contrast-resolution of conventional attenuation-contrast imaging, especially for soft-tissue structures that have very similar attenuation. Just as in attenuation-based tomography, phase contrast tomography requires a linear dependence of aggregate beam direction on the incremental direction alteration caused by individual voxels along the path of the X-ray beam. Dense objects such as calcifications in biological specimens violate this condition. There are extensive beam deflection artefacts in the vicinity of such structures because they result in large distortion of wave front due to the large difference of refractive index; for such large changes in beam direction, the transmittance of the silicon analyzer crystal saturates and is no longer linearly dependent on the angle of refraction. This paper describes a method by which these effects can be overcome and excellent soft-tissue contrast of phase tomography can be pr...

Scientific reports, Jan 14, 2015

X-ray phase-contrast imaging (XPCI) can dramatically improve soft tissue contrast in X-ray medica... more X-ray phase-contrast imaging (XPCI) can dramatically improve soft tissue contrast in X-ray medical imaging. Despite worldwide efforts to develop novel XPCI systems, a numerical framework to rigorously predict the performance of a clinical XPCI system at a human scale is not yet available. We have developed such a tool by combining a numerical anthropomorphic phantom defined with non-uniform rational B-splines (NURBS) and a wave optics-based simulator that can accurately capture the phase-contrast signal from a human-scaled numerical phantom. Using a synchrotron-based, high-performance XPCI system, we provide qualitative comparison between simulated and experimental images. Our tool can be used to simulate the performance of XPCI on various disease entities and compare proposed XPCI systems in an unbiased manner.

AJNR. American journal of neuroradiology, 2004

A CT scanner employing a digital flat-panel detector is capable of very high spatial resolution a... more 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. 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 microm 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. 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 th...

Journal of Medical Devices, 2012

This paper describes the design of a compact, lightweight CT-compatible, drill-press that is desi... more This paper describes the design of a compact, lightweight CT-compatible, drill-press that is designed to be used in either a hand-held or stand-alone mode to assist with percutaneous bone based interventions. Previous medical drilling tools that have been developed have a metal structure and typically have one actuator for advancing the drill (feed) and another for rotating it (speed). After defining the device functional requirements and specifications, a deterministic design process was followed to generate several design concepts that were then evaluated based on their ability to satisfy the functional requirements. A final concept that uses a custom screw-spline to achieve helical motion of a shaft that is attached to a standard orthopedic drill was selected for prototyping. The design uses a single actuator to drive both the screw and spline nuts through two different gear ratios, resulting in a fixed ratio between the feed and speed. Apart from the motor which is placed away f...

Stroke, 2013

Background and Purpose— Contrast medium extravasation (CE) in intracerebral hemorrhage (ICH) is a... more Background and Purpose— Contrast medium extravasation (CE) in intracerebral hemorrhage (ICH) is a marker of ongoing bleeding and a predictor of hematoma expansion. The aims of the study were to establish an ICH model in which CE can be quantified, characterized in ICH during warfarin and dabigatran anticoagulation, and to evaluate effects of prothrombin complex concentrates on CE in warfarin-associated ICH. Methods— CD1-mice were pretreated orally with warfarin, dabigatran, or vehicle. Prothrombin complex concentrates were administered in a subgroup of warfarin-treated mice. ICH was induced by stereotactic injection of collagenase VIIs into the right striatum. Contrast agent (350 μL Isovue 370 mg/mL) was injected intravenously after ICH induction (2–3.5 hours). Thirty minutes later, mice were euthanized, and CE was measured by quantifying the iodine content in the hematoma using dual-energy computed tomography. Results— The optimal time point for contrast injection was found to be 3...

RadioGraphics, 2008

Flat-panel volume computed tomography (CT) systems have an innovative design that allows coverage... more 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. ©

Journal of The Royal Society Interface, 2013

Engineered cartilage is a promising option for auricular reconstruction. We have previously demon... more Engineered cartilage is a promising option for auricular reconstruction. We have previously demonstrated that a titanium wire framework within a composite collagen ear-shaped scaffold helped to maintain the gross dimensions of the engineered ear after implantation, resisting the deformation forces encountered during neocartilage maturation and wound healing. The ear geometry was redesigned to achieve a more accurate aesthetic result when implanted subcutaneously in a nude rat model. A non-invasive method was developed to assess size and shape changes of the engineered ear in three dimensions. Computer models of the titanium framework were obtained from CT scans before and after implantation . Several parameters were measured including the overall length, width and depth, the minimum intrahelical distance and overall curvature values for each beam section within the framework. Local curvature values were measured to gain understanding of the bending forces experienced by the framewor...

Tissue engineering. Part A, 2009

Regenerative technology promises to alleviate the problem of limited donor supply for bone or org... more Regenerative technology promises to alleviate the problem of limited donor supply for bone or organ transplants. Most expensive and time consuming is cell expansion in laboratories. We propose a method of magnetically enriched osteoprogenitor stem cells, dispersed in self-assembling hydrogels and applied onto new ultra-high resolution, jet-based, three-dimensional printing of living human bone in a single-step for in situ bone regeneration. Human bone marrow-derived mesenchymal stem cells (hBMSCs) were enriched with CD 117+ cells, dispersed in different collagen I and RAD 16I hydrogel mixes, and applied onto three-dimensional printed btricalcium phosphate=poly(lactic-co-glycolic acid) scaffolds, printed from ultra-high-resolution volumetric CT images of a human thumb. Constructs were directly implanted subcutaneously into nude mice for 6 weeks. In vivo radiographic volumetric CT scanning and histological evaluations were performed at 1, 2, 4, and 6 weeks, and expression of bone-spec...

Bone, 2006

Trabecular bone is a material of choice for reconstruction after trauma and tumor resection and f... more Trabecular bone is a material of choice for reconstruction after trauma and tumor resection and for correction of congenital defects. Autologous bone grafts are available in limited shapes and sizes; significant donor site morbidity is another major disadvantage to this approach. To overcome these limitations, we used a tissue engineering approach to create bone replacements in vitro, combining bone-marrow-derived differentiated mesenchymal stem cells (MSCs) suspended in hydrogels and 3-dimensionally printed (3DP) porous scaffolds made of β-tricalcium-phosphate (β-TCP). The scaffolds provided support for the formation of bone tissue in collagen I, fibrin, alginate, and pluronic F127 hydrogels during culturing in oscillating and rotating dynamic conditions. Histological evaluation including toluidine blue, alkaline phosphatase, and von Kossa staining was done at 1, 2, 4, and 6 weeks. Radiographic evaluation and high-resolution volumetric CT (VCT) scanning, expression of bone-specific genes and biomechanical compression testing were performed at 6 weeks. Both culture conditions resulted in similar bone tissue formation. Histologically collagen I and fibrin hydrogels specimens had superior bone tissue, although radiopacities were detected only in collagen I samples. VCT scan revealed density values in all but the Pluronic F127 samples, with Houndsfield unit values comparable to native bone in collagen I and fibrin glue samples. Expression of bone-specific genes was significantly higher in the collagen I samples. Pluronic F127 hydrogel did not support formation of bone tissue. All samples cultured in dynamic oscillating conditions had slightly higher mechanical strength than under rotating conditions. Bone tissue can be successfully formed in vitro using constructs comprised of collagen I hydrogel, MSCs, and porous β-TCP scaffolds.

Bone, 2010

Osteopenia is a complication of anorexia nervosa (AN) associated with a two-to threefold increase... more Osteopenia is a complication of anorexia nervosa (AN) associated with a two-to threefold increase in fractures. Nutritional deficits and hormonal abnormalities are thought to mediate AN-induced bone loss. Alterations in bone microarchitecture may explain fracture risk independent of bone mineral density (BMD). Advances in CT imaging now allow for noninvasive evaluation of trabecular microstructure at peripheral sites in vivo. Few data are available regarding bone microarchitecture in AN. We therefore performed a cross-sectional study of 23 women (12 with AN and 11 healthy controls) to determine hormonal predictors of trabecular bone microarchitecture. Outcome measures included bone microarchitectural parameters at the ultradistal radius by flat panel Volume CT (fpVCT); BMD at the PA and lateral spine, total hip, femoral neck and ultradistal radius by dual energy X-ray absorptiometry (DXA); and IGF-I, leptin, estradiol, testosterone and free testosterone levels. Bone microarchitectural measures, including apparent (app.) bone volume fraction, app. trabecular thickness, and app. trabecular number, were reduced (p<0.03) and app. trabecular spacing was increased (p=0.02) in AN vs. controls. Decreased structural integrity at the ultradistal radius was associated with decreased BMD at all sites (p=0.05) except for total hip. IGF-I, leptin, testosterone and free testosterone levels predicted bone microarchitecture. All associations between both IGF-I and leptin levels and bone microarchitectural parameters, and most associations between androgen levels and microarchitecture remained significant after controlling for body mass index. We concluded that bone microarchitecture is abnormal in women with AN. Endogenous IGF-I, leptin and androgen levels predict bone microarchitecture independent of BMI.

Annals of Plastic Surgery, 2007

Traumatic amputation of a thumb with bone loss leaves a patient in severe disability. Reconstruct... more Traumatic amputation of a thumb with bone loss leaves a patient in severe disability. Reconstructive procedures are restricted by limited shape and have the disadvantage of severe donor-site morbidity. To overcome these limitations, we used a tissue engineering approach to create a distal thumb bone phalanx, combining magnetically sorted 133ϩ human mesenchymal stem cells (hMSCs) suspended in successful tested hydrogels for bone formation and porous 3-dimensionally printed scaffolds (3DP) in the shape of a distal thumb bone phalanx. Collagen I and fibrin glue hydrogels with suspended hMSCs were first histologically evaluated in vitro for bone formation after 6 weeks. Then 3DP scaffolds, made from a mix of osteoinductive and-conductive ␤-tricalciumphosphate (␤-TCP) and poly-caprolactone (PCL), with hydrogels and suspended hMSCs, were implanted into nude mice subcutaneously for 15 weeks. Histologic evaluation, high-resolution volumetric CT (VCT) scanning, and biomechanical testing confirmed formation of bonelike tissue. Both hydrogels with CD 133ϩ hMSCs on 3DP scaffolds supported bone formation. Collagen I resulted in radiologically better bone formation. Bone tissue can be successfully tissue engineered with CD 133ϩ hMSCs, collagen I hydrogels, and porous 3DP ␤-TCP/PCL scaffolds.

American Journal of Neuroradiology, 2008

BACKGROUND AND PURPOSE: Systematic facial mutilations during mummification have never been descri... more BACKGROUND AND PURPOSE: Systematic facial mutilations during mummification have never been described before. The purpose of this work was to study a wrapped mummified head using highresolution CT scanning. MATERIALS AND METHODS: An isolated mummified head from the Egyptian Middle Kingdom was scanned at 200 m isotropic resolution. A prototype flat panel CT scanner was used to generate 800 nonoverlapping CT sections at 120 kV and 50 mA. This dataset was analyzed to discern various surgical alterations during mummification. RESULTS: There were large defects in the cribriform plate and the posterior fossa. Systematic mutilations of the facial bones and mandible, involving the anterior and inferior walls of the maxillary sinuses, the floor of both orbits, and the zygomatic arches with contiguous segments of the zygomas, were demonstrated. The coronoid processes of both mandibles had been sharply excised and the articular tubercles of the temporomandibular joints fractured. CONCLUSION: Defects in the ethmoid and the posterior skull base are consistent with previous descriptions of excerebration. Mutilations of the facial skeleton and jaw, which are unrelated to the process of excerebration, have never been described previously. It is noteworthy that the osteotomies selectively include the insertions of the muscles of mastication. These mutilations apparently were designed for mobilization of lower jaw. The "Opening of the Mouth" ceremony, described in the ancient texts, would be difficult to perform in the presence of rigor mortis; it is probable that the observed osteotomies were performed to facilitate this ceremony. Our research suggests that by the Middle Kingdom, Egyptian embalmers had developed highly sophisticated surgical techniques that have not been appreciated previously. X-Ray Radiographs Radiographs of the mummified head were taken to study the highresolution projectional anatomy of the skull. Standard projectional x-ray views of the head were acquired to first look at the structure of the head. Morphometric measurements and the integrity (and lack of integrity) of various skull bones were established. Multidetector CT Detailed tomographic examination was undertaken to investigate the internal structure of the bones and to look inside the cranial vault by

American Journal of Otolaryngology, 1983

Tissue engineering. Part A, 2009

Regenerative technology promises to alleviate the problem of limited donor supply for bone or org... more Regenerative technology promises to alleviate the problem of limited donor supply for bone or organ transplants. Most expensive and time consuming is cell expansion in laboratories. We propose a method of magnetically enriched osteoprogenitor stem cells, dispersed in self-assembling hydrogels and applied onto new ultra-high resolution, jet-based, three-dimensional printing of living human bone in a single-step for in situ bone regeneration. Human bone marrow-derived mesenchymal stem cells (hBMSCs) were enriched with CD 117+ cells, dispersed in different collagen I and RAD 16I hydrogel mixes, and applied onto three-dimensional printed btricalcium phosphate=poly(lactic-co-glycolic acid) scaffolds, printed from ultra-high-resolution volumetric CT images of a human thumb. Constructs were directly implanted subcutaneously into nude mice for 6 weeks. In vivo radiographic volumetric CT scanning and histological evaluations were performed at 1, 2, 4, and 6 weeks, and expression of bone-spec...