Stanniocalcin (STC) is a polypeptide hormone that was first discovered in fish and recently ident... more Stanniocalcin (STC) is a polypeptide hormone that was first discovered in fish and recently identified in mammals. In fish, STC is released into the bloodstream in classical endocrine fashion and has well established regulatory effects on calcium and phosphate homeostasis. However, there are no suitable dose-response bioassays for STC and consequently no methods for assigning units of potency to preparations of the hormone. All the available in vitro bioassays are too complex from a technical standpoint to readily accommodate the large number of samples required in dose-response bioassays. Most in vivo bioassays are hampered by the fact that fish have natural rhythms governing plasma STC levels which tend to make them variably sensitive to the injected hormone. In this report we have developed a new in vivo bioassay for STC using rainbow trout. The key feature of the bioassay involves suppressing plasma STC levels to the extent that fish are always receptive to injected hormone. This has been accomplished by phosphate-loading the animals, which lowers their plasma calcium levels, removes the stimulus for STC secretion and brings about a reduction in resting plasma hormone levels. The net effect is an animal that is always responsive to injected STC. With this bioassay we have been able to obtain sensitive and reproducible, dose-related effects of salmon STC on gill calcium transport.
Development, characterization, and quality assurance of advanced x-ray imaging technologies requi... more Development, characterization, and quality assurance of advanced x-ray imaging technologies require phantoms that are quantitative and well suited to such modalities. This note reports on the design, construction, and use of an innovative phantom developed for advanced imaging technologies (e.g., multi-detector CT and the numerous applications of flat-panel detectors in dual-energy imaging, tomosynthesis, and cone-beam CT) in diagnostic and image-guided procedures. The design addresses shortcomings of existing phantoms by incorporating criteria satisfied by no other single phantom: (1) inserts are fully 3D—spherically symmetric rather than cylindrical; (2) modules are quantitative, presenting objects of known size and contrast for quality assurance and image quality investigation; (3) features are incorporated in ideal and semi-realistic (anthropomorphic) contexts; and (4) the phantom allows devices to be inserted and manipulated in an accessible module (right lung). The phantom consists of five primary modules: (1) head, featuring contrast-detail spheres approximate to brain lesions; (2) left lung, featuring contrast-detail spheres approximate to lung modules; (3) right lung, an accessible hull in which devices may be placed and manipulated; (4) liver, featuring conrast-detail spheres approximate to metastases; and (5) abdomen/pelvis, featuring simulated kidneys, colon, rectum, bladder, and prostate. The phantom represents a twofold evolution in design philosophy—from 2D (cylindrically symmetric) to fully 3D, and from exclusively qualitative or quantitative to a design accommodating quantitative study within an anatomical context. It has proven a valuable tool in investigations throughout our institution, including low-dose CT, dual-energy radiography, and cone-beam CT for image-guided radiation therapy and surgery.
We constructed a device to compress small samples of articu-lar cartilage while the samples were ... more We constructed a device to compress small samples of articu-lar cartilage while the samples were imaged in a 1.5 T imager. With the use of a piezoelectric piston, the device compressed 1-cm-diameter cylindrical samples of articular cartilage (200 m) at a rate of 2 Hz. Simultaneously, we imaged the samples with a displacement-sensitive stimulated-echo acquisition mode (STEAM) sequence. We validated the technique using tissue that mimicked silicone samples. We compared the results from the same cartilage samples before and after they were degraded by digestion in trypsin. The extent of degradation was visualized from T 1-weighted images of the samples after they were soaked in 0.5 mmolar of GdDTPA. The resulting elastographic images show compression and differential strain in directions both parallel and perpendicular to the surface of the cartilage. The static elastographic images that depict compression made before digestion and after 5 and 15 hr of trypsin digestion show that the elastic modulus of the samples decreased with a spatial variation consistent with the enzymatic digestion as revealed by the T 1 images. We believe this technique will be useful in studies of the mechanical properties of articular cartilage and other tissues, and may in the future be extended to the clinical setting. Magn Reson Med 53: 1065–1073, 2005.
Obtaining three-dimensional geometrical data of vascular systems is of major importance to a numb... more Obtaining three-dimensional geometrical data of vascular systems is of major importance to a number of research areas in medicine and biology. Examples are the characterization of tumor vasculature, modeling blood flow, or genetic effects on vascular development. The performance of the General Electric Medical Systems MS8 microCT scanner is examined in the context of these applications. The system is designed to acquire high-resolution images of specimens up to 5 cm in diameter. A maximum resolution of 38 lp/mm at the 10% modulation transfer function level or 22 m full width at half maximum of the plane spread function can be achieved with 8.5 m voxels and a 17 mm field of view. Three different contrast agents are discussed and applied for imaging of small animal vasculature: corrosion casting material Batson's No. 17 with an added lead pigment, silicon rubber MICROFIL MV122, and a suspension of barium sulfate Baritop in gelatin. Contrast for all of these agents was highly variable in different vessels as well as within the same vessel. Imaging of PMMA tubing filled with MICROFIL shows that even vessels below 20 m in diameter are detectable and that diameter estimation of vessels based on thresholding is possible with a precision of 2–3 pixels.
Stanniocalcin (STC) is a polypeptide hormone that was first discovered in fish and recently ident... more Stanniocalcin (STC) is a polypeptide hormone that was first discovered in fish and recently identified in mammals. In fish, STC is released into the bloodstream in classical endocrine fashion and has well established regulatory effects on calcium and phosphate homeostasis. However, there are no suitable dose-response bioassays for STC and consequently no methods for assigning units of potency to preparations of the hormone. All the available in vitro bioassays are too complex from a technical standpoint to readily accommodate the large number of samples required in dose-response bioassays. Most in vivo bioassays are hampered by the fact that fish have natural rhythms governing plasma STC levels which tend to make them variably sensitive to the injected hormone. In this report we have developed a new in vivo bioassay for STC using rainbow trout. The key feature of the bioassay involves suppressing plasma STC levels to the extent that fish are always receptive to injected hormone. This has been accomplished by phosphate-loading the animals, which lowers their plasma calcium levels, removes the stimulus for STC secretion and brings about a reduction in resting plasma hormone levels. The net effect is an animal that is always responsive to injected STC. With this bioassay we have been able to obtain sensitive and reproducible, dose-related effects of salmon STC on gill calcium transport.
Development, characterization, and quality assurance of advanced x-ray imaging technologies requi... more Development, characterization, and quality assurance of advanced x-ray imaging technologies require phantoms that are quantitative and well suited to such modalities. This note reports on the design, construction, and use of an innovative phantom developed for advanced imaging technologies (e.g., multi-detector CT and the numerous applications of flat-panel detectors in dual-energy imaging, tomosynthesis, and cone-beam CT) in diagnostic and image-guided procedures. The design addresses shortcomings of existing phantoms by incorporating criteria satisfied by no other single phantom: (1) inserts are fully 3D—spherically symmetric rather than cylindrical; (2) modules are quantitative, presenting objects of known size and contrast for quality assurance and image quality investigation; (3) features are incorporated in ideal and semi-realistic (anthropomorphic) contexts; and (4) the phantom allows devices to be inserted and manipulated in an accessible module (right lung). The phantom consists of five primary modules: (1) head, featuring contrast-detail spheres approximate to brain lesions; (2) left lung, featuring contrast-detail spheres approximate to lung modules; (3) right lung, an accessible hull in which devices may be placed and manipulated; (4) liver, featuring conrast-detail spheres approximate to metastases; and (5) abdomen/pelvis, featuring simulated kidneys, colon, rectum, bladder, and prostate. The phantom represents a twofold evolution in design philosophy—from 2D (cylindrically symmetric) to fully 3D, and from exclusively qualitative or quantitative to a design accommodating quantitative study within an anatomical context. It has proven a valuable tool in investigations throughout our institution, including low-dose CT, dual-energy radiography, and cone-beam CT for image-guided radiation therapy and surgery.
We constructed a device to compress small samples of articu-lar cartilage while the samples were ... more We constructed a device to compress small samples of articu-lar cartilage while the samples were imaged in a 1.5 T imager. With the use of a piezoelectric piston, the device compressed 1-cm-diameter cylindrical samples of articular cartilage (200 m) at a rate of 2 Hz. Simultaneously, we imaged the samples with a displacement-sensitive stimulated-echo acquisition mode (STEAM) sequence. We validated the technique using tissue that mimicked silicone samples. We compared the results from the same cartilage samples before and after they were degraded by digestion in trypsin. The extent of degradation was visualized from T 1-weighted images of the samples after they were soaked in 0.5 mmolar of GdDTPA. The resulting elastographic images show compression and differential strain in directions both parallel and perpendicular to the surface of the cartilage. The static elastographic images that depict compression made before digestion and after 5 and 15 hr of trypsin digestion show that the elastic modulus of the samples decreased with a spatial variation consistent with the enzymatic digestion as revealed by the T 1 images. We believe this technique will be useful in studies of the mechanical properties of articular cartilage and other tissues, and may in the future be extended to the clinical setting. Magn Reson Med 53: 1065–1073, 2005.
Obtaining three-dimensional geometrical data of vascular systems is of major importance to a numb... more Obtaining three-dimensional geometrical data of vascular systems is of major importance to a number of research areas in medicine and biology. Examples are the characterization of tumor vasculature, modeling blood flow, or genetic effects on vascular development. The performance of the General Electric Medical Systems MS8 microCT scanner is examined in the context of these applications. The system is designed to acquire high-resolution images of specimens up to 5 cm in diameter. A maximum resolution of 38 lp/mm at the 10% modulation transfer function level or 22 m full width at half maximum of the plane spread function can be achieved with 8.5 m voxels and a 17 mm field of view. Three different contrast agents are discussed and applied for imaging of small animal vasculature: corrosion casting material Batson's No. 17 with an added lead pigment, silicon rubber MICROFIL MV122, and a suspension of barium sulfate Baritop in gelatin. Contrast for all of these agents was highly variable in different vessels as well as within the same vessel. Imaging of PMMA tubing filled with MICROFIL shows that even vessels below 20 m in diameter are detectable and that diameter estimation of vessels based on thresholding is possible with a precision of 2–3 pixels.
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Papers by Cameron B Chiarot