... John F. Schenck MA Hussain ... McKeehan suggested a number of methods for designing cylindric... more ... John F. Schenck MA Hussain ... McKeehan suggested a number of methods for designing cylindrically symmetric svstems using the harmonic functions• The theory was taken to its most successful level in a classicl~e~es of papers by Milan Wayne Garrett Using the theory of zonal ...
Proceedings of the National Academy of Sciences, 2010
Recent advances in high-field MRI have dramatically improved the visualization of human brain ana... more Recent advances in high-field MRI have dramatically improved the visualization of human brain anatomy in vivo. Most notably, in cortical gray matter, strong contrast variations have been observed that appear to reflect the local laminar architecture. This contrast has been attributed to subtle variations in the magnetic properties of brain tissue, possibly reflecting varying iron and myelin content. To establish the origin of this contrast, MRI data from postmortem brain samples were compared with electron microscopy and histological staining for iron and myelin. The results show that iron is distributed over laminae in a pattern that is suggestive of each region’s myeloarchitecture and forms the dominant source of the observed MRI contrast.
The ability of magnetic resonance imaging to detect small temperature elevations from focused ult... more The ability of magnetic resonance imaging to detect small temperature elevations from focused ultrasound surgery beams was studied. In addition, the value of a contrast agent in delineating the necrosed tissue volume was investigated. Gradient-recalled acquisition in a steady state (GRASS) T1-weighted images were used to follow the temperature elevation and tissue changes during 2-minute sonications in the thigh muscles of 10 rabbits. The effects of the treatment on the vascular network was investigated by injecting a contrast agent bolus before or after the sonication. The signal intensity decreased during the sonication, and the reduction was directly proportional to the applied power and increase in temperature. The signal intensity returned gradually back to baseline after the ultrasound was turned off. Injection of the contrast agent increased the signal intensity in muscle, but not in the necrosed tissue. The dimensions of the delineated tissue volume were the same as measured from the T2-weighted fast-spin-echo images and postmortem tissue examination. These results indicate that magnetic resonance imaging can be used to detect temperature elevations that do not cause tissue damage and that contrast agent can be used to delineate the necrosed tissue volume.
A radio-frequency coil, for nuclear magnetic resonance imaging at Larmor frequencies associated w... more A radio-frequency coil, for nuclear magnetic resonance imaging at Larmor frequencies associated with a magnetic field of greater than about 0.5 Tesla, comprises a slotted-tube radio-frequency resonator having an elliptical cross-section. First and second complementary outer resonator portions have central bands connecting juxtaposed wing structures; the end of each of the four wings is spaced from a complementary wing portion of the other outer portion and capacitively coupled thereto. An inner structure has a pair of elliptical guard rings placed substantially in registration with the elliptical portions of the outer structure wing portions. The eccentricity ratio of the elliptical cross-section of the resonator and the resonator dimensions are arranged to provide an interior volume into which a human head or body extremity can be placed for imaging purposes.
A hydrogen (1H) nuclear magnetic resonance (NMR) imaging study of the normal head, thorax, and li... more A hydrogen (1H) nuclear magnetic resonance (NMR) imaging study of the normal head, thorax, and limbs is reported. The images are 10 to 15 mm thick transverse slices obtained in 2 to 4 min using a two-dimensional Fourier transform technique. Spatial resolution in the imaging plane is about 2 mm, enabling the optic nerve and many small blood vessels to be observed. Thorax scans show details of the cardiac chambers, aorta wall, and lungs without artefacts arising from physiological motion.
... John F. Schenck MA Hussain ... McKeehan suggested a number of methods for designing cylindric... more ... John F. Schenck MA Hussain ... McKeehan suggested a number of methods for designing cylindrically symmetric svstems using the harmonic functions• The theory was taken to its most successful level in a classicl~e~es of papers by Milan Wayne Garrett Using the theory of zonal ...
Proceedings of the National Academy of Sciences, 2010
Recent advances in high-field MRI have dramatically improved the visualization of human brain ana... more Recent advances in high-field MRI have dramatically improved the visualization of human brain anatomy in vivo. Most notably, in cortical gray matter, strong contrast variations have been observed that appear to reflect the local laminar architecture. This contrast has been attributed to subtle variations in the magnetic properties of brain tissue, possibly reflecting varying iron and myelin content. To establish the origin of this contrast, MRI data from postmortem brain samples were compared with electron microscopy and histological staining for iron and myelin. The results show that iron is distributed over laminae in a pattern that is suggestive of each region’s myeloarchitecture and forms the dominant source of the observed MRI contrast.
The ability of magnetic resonance imaging to detect small temperature elevations from focused ult... more The ability of magnetic resonance imaging to detect small temperature elevations from focused ultrasound surgery beams was studied. In addition, the value of a contrast agent in delineating the necrosed tissue volume was investigated. Gradient-recalled acquisition in a steady state (GRASS) T1-weighted images were used to follow the temperature elevation and tissue changes during 2-minute sonications in the thigh muscles of 10 rabbits. The effects of the treatment on the vascular network was investigated by injecting a contrast agent bolus before or after the sonication. The signal intensity decreased during the sonication, and the reduction was directly proportional to the applied power and increase in temperature. The signal intensity returned gradually back to baseline after the ultrasound was turned off. Injection of the contrast agent increased the signal intensity in muscle, but not in the necrosed tissue. The dimensions of the delineated tissue volume were the same as measured from the T2-weighted fast-spin-echo images and postmortem tissue examination. These results indicate that magnetic resonance imaging can be used to detect temperature elevations that do not cause tissue damage and that contrast agent can be used to delineate the necrosed tissue volume.
A radio-frequency coil, for nuclear magnetic resonance imaging at Larmor frequencies associated w... more A radio-frequency coil, for nuclear magnetic resonance imaging at Larmor frequencies associated with a magnetic field of greater than about 0.5 Tesla, comprises a slotted-tube radio-frequency resonator having an elliptical cross-section. First and second complementary outer resonator portions have central bands connecting juxtaposed wing structures; the end of each of the four wings is spaced from a complementary wing portion of the other outer portion and capacitively coupled thereto. An inner structure has a pair of elliptical guard rings placed substantially in registration with the elliptical portions of the outer structure wing portions. The eccentricity ratio of the elliptical cross-section of the resonator and the resonator dimensions are arranged to provide an interior volume into which a human head or body extremity can be placed for imaging purposes.
A hydrogen (1H) nuclear magnetic resonance (NMR) imaging study of the normal head, thorax, and li... more A hydrogen (1H) nuclear magnetic resonance (NMR) imaging study of the normal head, thorax, and limbs is reported. The images are 10 to 15 mm thick transverse slices obtained in 2 to 4 min using a two-dimensional Fourier transform technique. Spatial resolution in the imaging plane is about 2 mm, enabling the optic nerve and many small blood vessels to be observed. Thorax scans show details of the cardiac chambers, aorta wall, and lungs without artefacts arising from physiological motion.
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