Matthew B. Smith, M.D.

Ceacam1 separates graft-versus-host-disease from graft-versus-tumor activity after experimental allogeneic bone marrow transplantation
Lu, Sydney X; Kappel, Lucy W; Charbonneau-Allard, Anne-Marie; Atallah, Renee; Holland, Amanda M; Turbide, Claire; Hubbard, Vanessa M; Rotolo, Jimmy A; Smith, Marsinay; Suh, David; King, Christopher; Rao, Uttam K; Yim, Nury; Bautista, Johanne L; Jenq, Robert R; Penack, Olaf; Na, Il-Kang; Liu, Chen; Murphy, George; Alpdogan, Onder; Blumberg, Richard S; Macian, Fernando; Holmes, Kathryn V; Beauchemin, Nicole; van den Brink, Marcel R M
2011 ;6(7):e21611-e21611, PLoS ONE
BACKGROUND: Allogeneic bone marrow transplantation (allo-BMT) is a potentially curative therapy for a variety of hematologic diseases, but benefits, including graft-versus-tumor (GVT) activity are limited by graft-versus-host-disease (GVHD). Carcinoembryonic antigen related cell adhesion molecule 1 (Ceacam1) is a transmembrane glycoprotein found on epithelium, T cells, and many tumors. It regulates a variety of physiologic and pathological processes such as tumor biology, leukocyte activation, and energy homeostasis. Previous studies suggest that Ceacam1 negatively regulates inflammation in inflammatory bowel disease models. METHODS: We studied Ceacam1 as a regulator of GVHD and GVT after allogeneic bone marrow transplantation (allo-BMT) in mouse models. In vivo, Ceacam1(-/-) T cells caused increased GVHD mortality and GVHD of the colon, and greater numbers of donor T cells were positive for activation markers (CD25(hi), CD62L(lo)). Additionally, Ceacam1(-/-) CD8 T cells had greater expression of the gut-trafficking integrin alpha(4)beta(7), though both CD4 and CD8 T cells were found increased numbers in the gut post-transplant. Ceacam1(-/-) recipients also experienced increased GVHD mortality and GVHD of the colon, and alloreactive T cells displayed increased activation. Additionally, Ceacam1(-/-) mice had increased mortality and decreased numbers of regenerating small intestinal crypts upon radiation exposure. Conversely, Ceacam1-overexpressing T cells caused attenuated target-organ and systemic GVHD, which correlated with decreased donor T cell numbers in target tissues, and mortality. Finally, graft-versus-tumor survival in a Ceacam1(+) lymphoma model was improved in animals receiving Ceacam1(-/-) vs. control T cells. CONCLUSIONS: We conclude that Ceacam1 regulates T cell activation, GVHD target organ damage, and numbers of donor T cells in lymphoid organs and GVHD target tissues. In recipients of allo-BMT, Ceacam1 may also regulate tissue radiosensitivity. Because of its expression on both the donor graft and host tissues, this suggests that targeting Ceacam1 may represent a potent strategy for the regulation of GVHD and GVT after allogeneic transplantation
— id: 150324, year: 2011, vol: 6, page: e21611, stat: Journal Article,

Reducing SAR and enhancing cerebral signal-to-noise ratio with high permittivity padding at 3 T
Yang, Qing X; Wang, Jianli; Wang, Jinghua; Collins, Christopher M; Wang, Chunsheng; Smith, Michael B
2011 Feb;65(2):358-362, Magnetic resonance in medicine
Previous works have shown that placement of a high-dielectric pad can improve image intensity in a region adjacent to the pad, or that placement of dielectric pads around a large surface of the head can improve image homogeneity on an entire plane through the head in high-field MRI. Here, experimental results show that use of high-dielectric pads around the human head can reduce the required input radiofrequency power by 50% while enhancing image signal-to-noise ratio by 20-40% throughout the cerebrum at 3 T. Thus, dielectric pads may be used to provide a relatively simple and low-cost method for improving quality and safety of MRI in a variety of applications at 3 T
— id: 148972, year: 2011, vol: 65, page: 358, stat: Journal Article,

Reducing SAR and enhancing cerebral signal-to-noise ratio with high permittivity padding at 3 T
Yang QX; Wang J; Wang J; Collins CM; Wang C; Smith MB
2010 Nov 30;:?-?, Magnetic resonance in medicine
Previous works have shown that placement of a high-dielectric pad can improve image intensity in a region adjacent to the pad, or that placement of dielectric pads around a large surface of the head can improve image homogeneity on an entire plane through the head in high-field MRI. Here, experimental results show that use of high-dielectric pads around the human head can reduce the required input radiofrequency power by 50% while enhancing image signal-to-noise ratio by 20-40% throughout the cerebrum at 3 T. Thus, dielectric pads may be used to provide a relatively simple and low-cost method for improving quality and safety of MRI in a variety of applications at 3 T. Magn Reson Med, 2010. (c) 2010 Wiley-Liss, Inc
— id: 148973, year: 2010, vol: , page: ?, stat: Journal Article,

Array-optimized composite pulse for excellent whole-brain homogeneity in high-field MRI
Collins, Christopher M; Wang, Zhangwei; Mao, Weihua; Fang, Jieming; Liu, Wanzhan; Smith, Michael B
2007 Mar;57(3):470-474, Magnetic resonance in medicine
A number of methods to improve excitation homogeneity in high-field MRI have been proposed, and some of these methods rely on separate control of radiofrequency (RF) coils in a transmit array. In this work we combine accurate RF field calculations and the Bloch equation to demonstrate that by using a sequence of pulses with individually optimized current distributions (i.e., an array-optimized composite pulse), one can achieve remarkably homogeneous distributions of available signal intensity over the entire brain volume. This homogeneity is greater than that achievable using the same transmit array to produce either a single optimized (or RF shimmed) pulse or a single RF shimmed field distribution in a standard 90x-90y composite pulse arrangement. Simulations indicate that with a very simple array-optimized composite pulse, excellent whole-brain excitation homogeneity can be achieved at up to 600 MHz
— id: 148988, year: 2007, vol: 57, page: 470, stat: Journal Article,

Direct magnetic resonance imaging of histological tissue samples at 3.0T
Meadowcroft, Mark D; Zhang, Shutong; Liu, Wanzhan; Park, Bu Sik; Connor, James R; Collins, Christopher M; Smith, Michael B; Yang, Qing X
2007 May;57(5):835-841, Magnetic resonance in medicine
Direct imaging of a histological slice is challenging. The vast difference in dimension between planar size and the thickness of histology slices would require an RF coil to produce a uniform RF magnetic (B1) field in a 2D plane with minimal thickness. In this work a novel RF coil designed specifically for imaging a histology slice was developed and tested. The experimental data demonstrate that the coil is highly sensitive and capable of producing a uniform B1 field distribution in a planar region of histological slides, allowing for the acquisition of high-resolution T2 images and T2 maps from a 60-microm-thick histological sample. The image intensity and T2 distributions were directly compared with histological staining of the relative iron concentration of the same slice. This work demonstrates the feasibility of using a microimaging histological coil to image thin slices of pathologically diseased tissue to obtain a precise one-to-one comparison between stained tissue and MR images
— id: 148987, year: 2007, vol: 57, page: 835, stat: Journal Article,

Chronic pain and psychopathology: One psychiatrist's view
Smith, Matthew B
2007 ;14(9):55-68 Sep, Primary Psychiatry
Chronic pain involves a somatic basis that is distinct from that of acute pain. It differs in its subjective experience and involves behavioral, personality, and syndromal pathologies which serve to worsen function and quality of life. Prior psychopathology makes an important contribution. The final state is one of both somatic and psychic suffering such that the two are not phenomenologically or etiologically distinguishable. Assessment and treatment must deal with the psychopathology as well as the physical pathology.
— id: 92729, year: 2007, vol: 14, page: 55, stat: Journal Article,

SAR and temperature: simulations and comparison to regulatory limits for MRI
Wang, Zhangwei; Lin, James C; Mao, Weihua; Liu, Wanzhan; Smith, Michael B; Collins, Christopher M
2007 Aug;26(2):437-441, Journal of magnetic resonance imaging
PURPOSE: To present and discuss numerical calculations of the specific absorption rate (SAR) and temperature in comparison to regulatory limits. While it is possible to monitor whole-body or whole-head average SAR and/or core body temperature during MRI in practice, this is not generally true for local SAR values or local temperatures throughout the body. While methods of calculation for SAR and temperature are constantly being refined, methods for interpreting results of these calculations in light of regulatory limits also warrant discussion. MATERIALS AND METHODS: Numerical calculations of SAR and temperature for the human head in a volume coil for MRI at several different frequencies are presented. RESULTS: Just as the field pattern changes with the frequency, so do the temperature distribution and the ratio of maximum local SAR (in 1-g or 10-g regions) to whole-head average SAR. In all of the cases studied here this ratio is far greater than that in the regulatory limits, indicating that existing limits on local SAR will be exceeded before limits on whole-body or whole-head average SAR are reached. CONCLUSION: Calculations indicate that both SAR and temperature distributions vary greatly with B(1) field frequency, that temperature distributions do not always correlate well with SAR distributions, and that regulatory limits on local temperature may not be exceeded as readily as those on local SAR
— id: 148986, year: 2007, vol: 26, page: 437, stat: Journal Article,

Consideration of magnetically-induced and conservative electric fields within a loaded gradient coil
Mao, Weihua; Chronik, Blaine A; Feldman, Rebecca E; Smith, Michael B; Collins, Christopher M
2006 Jun;55(6):1424-1432, Magnetic resonance in medicine
We present a method to calculate the electric (E)-fields within and surrounding a human body in a gradient coil, including E-fields induced by the changing magnetic fields and 'conservative' E-fields originating with the scalar electrical potential in the coil windings. In agreement with previous numerical calculations, it is shown that magnetically-induced E-fields within the human body show no real concentration near the surface of the body, where nerve stimulation most often occurs. Both the magnetically-induced and conservative E-fields are shown to be considerably stronger just outside the human body than inside it, and under some circumstances the conservative E-fields just outside the body can be much larger than the magnetically-induced E-fields there. The order of gradient winding and the presence of conductive RF shield can greatly affect the conservative E-field distribution in these cases. Though the E-fields against the outer surface of the body are not commonly considered, understanding gradient E-fields may be important for reasons other than peripheral nerve stimulation (PNS), such as potential interaction with electrical equipment
— id: 148991, year: 2006, vol: 55, page: 1424, stat: Journal Article,

Exploring the limits of RF shimming for high-field MRI of the human head
Mao, Weihua; Smith, Michael B; Collins, Christopher M
2006 Oct;56(4):918-922, Magnetic resonance in medicine
Several methods have been proposed for overcoming the effects of radiofrequency (RF) magnetic field inhomogeneity in high-field MRI. Some of these methods rely at least in part on the ability to independently control magnitude and phase of different drives in either one multielement RF coil or in different RF coils in a transmit array. The adjustment of these drive magnitudes and phases alone to create uniform RF magnetic (B(1)) fields has been called RF shimming, and has certain limits at every frequency as dictated by possible solutions to Maxwell's equations. Here we use numerical calculations to explore the limits of RF shimming in the human head. We found that a 16-element array can effectively shim a single slice at frequencies up to 600 MHz and the whole brain at up to 300 MHz, while an 80-element array can shim the whole brain at up to 600 MHz
— id: 148990, year: 2006, vol: 56, page: 918, stat: Journal Article,

Central brightening due to constructive interference with, without, and despite dielectric resonance
Collins, Christopher M; Liu, Wanzhan; Schreiber, Weston; Yang, Qing X; Smith, Michael B
2005 Feb;21(2):192-196, Journal of magnetic resonance imaging
PURPOSE: To aid in discussion about the mechanism for central brightening in high field magnetic resonance imaging (MRI), especially regarding the appropriateness of using the term dielectric resonance to describe the central brightening seen in images of the human head. MATERIALS AND METHODS: We present both numerical calculations and experimental images at 3 T of a 35-cm-diameter spherical phantom of varying salinity both with one surface coil and with two surface coils on opposite sides, and further numerical calculations at frequencies corresponding to dielectric resonances for the sphere. RESULTS: With two strategically placed surface coils it is possible to create central brightening even when one coil alone excites an image intensity pattern either bright on one side only or bright on both sides with central darkening. This central brightening can be created with strategic coil placement even when the resonant pattern would favor central darkening. Results in a conductive sample show that central brightening can similarly be achieved in weakly conductive dielectric materials where any true resonances would be heavily damped, such as in human tissues. CONCLUSION: Constructive interference and wavelength effects are likely bigger contributors to central brightening in MR images of weakly conductive biological samples than is true dielectric resonance
— id: 148996, year: 2005, vol: 21, page: 192, stat: Journal Article,

Combination of optimized transmit arrays and some receive array reconstruction methods can yield homogeneous images at very high frequencies
Collins, Christopher M; Liu, Wanzhan; Swift, Bryan J; Smith, Michael B
2005 Dec;54(6):1327-1332, Magnetic resonance in medicine
Image inhomogeneity related to high radiofrequencies is one of the major challenges for high field imaging. This inhomogeneity can be thought of as having 2 radiofrequency-field related contributors: the transmit field distribution and the reception field distribution. Adjusting magnitude and phase of currents in elements of a transmit array can significantly improve flip angle homogeneity at high field. Effective application of some well-known parallel imaging and other receive array post-processing methods removes receptivity patterns from the intensity distribution in the final image, though noise then becomes a function of position in the final image. Here simulations are used to show that, assuming high signal-to-noise ratio, very homogeneous images in the human head can be acquired with the combination of transmit arrays and some receive array reconstruction methods at frequencies as high as 600 MHz
— id: 148993, year: 2005, vol: 54, page: 1327, stat: Journal Article,

Hexagonal zero mode TEM coil: a single-channel coil design for imaging multiple small animals
Lazovic, Jelena; Stojkovic, Dragan S; Collins, Christopher M; Yang, Qing X; Vaughan, J Thomas; Smith, Michael B
2005 May;53(5):1150-1157, Magnetic resonance in medicine
A novel hexagonal coil design for simultaneous imaging of multiple small animals is presented. The design is based on a coaxial cavity and utilizes the magnetic field formed between two coaxial conductors with hexagonal cross-sections. An analytical solution describing the B(1) field between conductors of the hexagonal coil was found from the Biot-Savart law. Both experimental results and analytical calculations showed a variation in the B(1) field within the imaging region of less than 10%. Numerical calculations predicted approximately 35% improvement in B(1) field homogeneity with the hexagonal coil design compared to a cylindrical coaxial cavity design. The experimentally-measured signal-to-noise ratio (SNR) of the hexagonal coil loaded with six 50-mM phantoms was only 4-5% lower than that of a single parallel plate resonator loaded with one phantom. In vivo spin-echo (SE) images of six 7-day-old rat pups acquired simultaneously demonstrated sufficient SNR for microimaging. The construction scheme of the coil, simple methods for tuning and matching, and an anesthesia device and animal holder designed for the coil are described. The hexagonal coil design utilizes a single receiver and allows for simultaneous imaging of six small animals with no significant compromise in SNR
— id: 148995, year: 2005, vol: 53, page: 1150, stat: Journal Article,

B(1) destructive interferences and spatial phase patterns at 7 T with a head transceiver array coil
Van de Moortele, Pierre-Francois; Akgun, Can; Adriany, Gregor; Moeller, Steen; Ritter, Johannes; Collins, Christopher M; Smith, Michael B; Vaughan, J Thomas; Ugurbil, Kamil
2005 Dec;54(6):1503-1518, Magnetic resonance in medicine
RF behavior in the human head becomes complex at ultrahigh magnetic fields. A bright center and a weak periphery are observed in images obtained with volume coils, while surface coils provide strong signal in the periphery. Intensity patterns reported with volume coils are often loosely referred to as 'dielectric resonances,' while modeling studies ascribe them to superposition of traveling waves greatly dampened in lossy brain tissues, raising questions regarding the usage of this term. Here we address this question experimentally, taking full advantage of a transceiver coil array that was used in volume transmit mode, multiple receiver mode, or single transmit surface coil mode. We demonstrate with an appropriately conductive sphere phantom that destructive interferences are responsible for a weak B(1) in the periphery, without a significant standing wave pattern. The relative spatial phase of receive and transmit B(1) proved remarkably similar for the different coil elements, although with opposite rotational direction. Additional simulation data closely matched our phantom results. In the human brain the phase patterns were more complex but still exhibited similarities between coil elements. Our results suggest that measuring spatial B(1) phase could help, within an MR session, to perform RF shimming in order to obtain more homogeneous B(1) in user-defined areas of the brain
— id: 148992, year: 2005, vol: 54, page: 1503, stat: Journal Article,

Temperature and SAR calculations for a human head within volume and surface coils at 64 and 300 MHz
Collins, Christopher M; Liu, Wanzhan; Wang, Jinghua; Gruetter, Rolf; Vaughan, J Thomas; Ugurbil, Kamil; Smith, Michael B
2004 May;19(5):650-656, Journal of magnetic resonance imaging
PURPOSE: To examine relationships between specific energy absorption rate (SAR) and temperature distributions in the human head during radio frequency energy deposition in MRI. MATERIALS AND METHODS: A multi-tissue numerical model of the head was developed that considered thermal conductivity, heat capacity, perfusion, heat of metabolism, electrical properties, and density. Calculations of SAR and the resulting temperature increase were performed for different coils at different frequencies. RESULTS: Because of tissue-dependent perfusion rates and thermal conduction, there is not a good overall spatial correlation between SAR and temperature increase. When a volume coil is driven to induce a head average SAR level of either 3.0 or 3.2 W/kg, it is unlikely that a significant temperature increase in the brain will occur due to its high rate of perfusion, although limits on SAR in any 1 g of tissue in the head may be exceeded. CONCLUSION: Attempts to ensure RF safety in MRI often rely on assumptions about local temperature from local SAR levels. The relationship between local SAR and local temperature is not, however, straightforward. In cases where high SAR levels are required due to pulse sequence demands, calculations of temperature may be preferable to calculations of SAR because of the more direct relationship between temperature and safety
— id: 148999, year: 2004, vol: 19, page: 650, stat: Journal Article,

Model of local temperature changes in brain upon functional activation
Collins, Christopher M; Smith, Michael B; Turner, Robert
2004 Dec;97(6):2051-2055, Journal of applied physiology (Bethesda)
Experimental results for changes in brain temperature during functional activation show large variations. It is, therefore, desirable to develop a careful numerical model for such changes. Here, a three-dimensional model of temperature in the human head using the bioheat equation, which includes effects of metabolism, perfusion, and thermal conduction, is employed to examine potential temperature changes due to functional activation in brain. It is found that, depending on location in brain and corresponding baseline temperature relative to blood temperature, temperature may increase or decrease on activation and concomitant increases in perfusion and rate of metabolism. Changes in perfusion are generally seen to have a greater effect on temperature than are changes in metabolism, and hence active brain is predicted to approach blood temperature from its initial temperature. All calculated changes in temperature for reasonable physiological parameters have magnitudes <0.12 degrees C and are well within the range reported in recent experimental studies involving human subjects
— id: 148997, year: 2004, vol: 97, page: 2051, stat: Journal Article,

Effects of end-ring/shield configuration on homogeneity and signal-to-noise ratio in a birdcage-type coil loaded with a human head
Liu, Wanzhan; Collins, Christopher M; Delp, Pamela J; Smith, Michael B
2004 Jan;51(1):217-221, Magnetic resonance in medicine
We modeled four different end-ring/shield configurations of a birdcage coil to examine their effects on field homogeneity and signal-to-noise ratio (SNR) at 64 MHz and 125 MHz. The configurations are defined as: 1) conventional: a conventional cylindrical shield; 2) surrounding shield: a shield with annular extensions to closely shield the end rings; 3) solid connection: a shield with annular extensions connected to the rungs; and 4) thin wire connection: a shield with thin wires connected to the rungs. At both frequencies, the coil with conventional end-ring/shield configuration produces the most homogeneous RF magnetic (B1) field when the coil is empty, but produces the least homogeneous B1 field when the coil is loaded with a human head. The surrounding shield configuration results in the most homogeneous B1 and highest SNR in the coil loaded with the human head at both frequencies, followed closely by the solid connection configuration
— id: 149001, year: 2004, vol: 51, page: 217, stat: Journal Article,

Effect of gender on in vivo cartilage magnetic resonance imaging T2 mapping
Mosher, Timothy J; Collins, Christopher M; Smith, Harvey E; Moser, Lauren E; Sivarajah, Rebecca T; Dardzinski, Bernard J; Smith, Michael B
2004 Mar;19(3):323-328, Journal of magnetic resonance imaging
PURPOSE: To determine if gender is a significant variable for in vivo magnetic resonance imaging (MRI) T2-mapping of knee articular cartilage in young asymptomatic volunteers. MATERIALS AND METHODS: Cartilage MRI T2 mapping was performed in a young healthy population consisting of seven male and 10 female volunteers, 22 to 29 years of age. High-resolution in vivo T2 maps were obtained of patellar, tibial, and weight-bearing femoral articular cartilage. Spatial dependency of cartilage T2 between groups was evaluated through a comparison of cartilage T2 as a function of normalized distance from bone. RESULTS: Bulk cartilage T2 values were similar at all three anatomic sites, and between male and female volunteers. All volunteers demonstrated similar spatial variation in cartilage MRI T2 values, with a minimum located in the radial zone and increasing T2 values toward the articular surface. There was no difference in spatial dependency of cartilage T2 between males and females. CONCLUSION: In young, healthy volunteers, the magnitude and spatial dependency of cartilage T2 does not differ with gender
— id: 149000, year: 2004, vol: 19, page: 323, stat: Journal Article,

Phantom design method for high-field MRI human systems
Yang, Qing X; Wang, Jinghua; Collins, Christopher M; Smith, Michael B; Zhang, Xiaoliang; Ugurbil, Kamil; Chen, Wei
2004 Nov;52(5):1016-1020, Magnetic resonance in medicine
A phantom design method suitable for high-field MRI based on the RF field wave characteristics of sample and experimental validations at 7.0 T and 3.0 T are presented. The RF field distribution in a phantom with a given RF coil system is primarily determined by the sample size relative to the wavelength inside the sample, and the ratio between the displacement and conduction currents. Experimental results demonstrate that the MR image intensity patterns associated with wave behavior in human samples at a given field strength can be reproduced with a phantom at the same or different field strengths once the dimension and penetration constant are scaled by the corresponding wavelength in the sample medium
— id: 148998, year: 2004, vol: 52, page: 1016, stat: Journal Article,

Theoretical and experimental evaluation of detached endcaps for 3 T birdcage coils
Alecci, Marcello; Collins, Christopher M; Wilson, James; Liu, Wanzhan; Smith, Michael B; Jezzard, Peter
2003 Feb;49(2):363-370, Magnetic resonance in medicine
The use of detached endcaps for 3 T birdcage coils was investigated both theoretically and experimentally. Finite difference time domain analysis, along with workbench and MRI techniques, were used to map the radiofrequency (RF) B(1) distribution along the coil axis with and without an endcap. Without an endcap the measured B(1) value at the service end of the birdcage was only 45% of the value at the coil's center. This was improved to 85% with a detached endcap of maximum achievable diameter (375 mm), positioned 4 mm from the RF shield. The B(1) field distribution on the patient side of the coil was unaffected by the presence of the endcap. The dependence of the B(1) distribution as a function of endcap diameter was also investigated. Surprisingly, simulations and experiments show that there is an optimum ratio of endcap-to-birdcage coil diameter (approximately 1.08) that gives the best B(1) homogeneity. In the human head the optimized endcap, positioned 16 mm from the RF shield, improves the MRI signal amplitude from 55% to 85% of maximum toward the service end. This novel endcap design is easy to implement with existing birdcage coils, and could prove useful when flexibility in access to the RF coil is required
— id: 149003, year: 2003, vol: 49, page: 363, stat: Journal Article,

Spatial resolution of numerical models of man and calculated specific absorption rate using the FDTD method: a study at 64 MHz in a magnetic resonance imaging coil
Collins, Christopher M; Smith, Michael B
2003 Sep;18(3):383-388, Journal of magnetic resonance imaging
PURPOSE: To examine how fine a model resolution is necessary for calculation of specific energy absorption rate (SAR) for the human head in regions as small as 1 g. MATERIALS AND METHODS: Here we perform a simple study comparing the maximum SAR averaged over any 1 cm(3) and SAR averaged over the entire head for several models of the same human head within the same radiofrequency coil, but with spatial resolutions varying from 8-100 Yee cells per cm(3). RESULTS: Over the range of model resolutions from 8-100 Yee cells per cm(3), there is only a 16% variation in maximum SAR in any 1 cm(3) of tissue in the head, and only a 7% variation in SAR averaged over the entire head. CONCLUSION: While it is always desirable to perform SAR calculations with the greatest possible accuracy, in calculations of the maximum SAR levels in any 1 cm(3) of tissue, spatial resolutions greater than 5 mm may not yield notably different results than those with a spatial resolution of 5 mm
— id: 149002, year: 2003, vol: 18, page: 383, stat: Journal Article,

Numerical calculations of the static magnetic field in three-dimensional multi-tissue models of the human head
Collins, Christopher M; Yang, Bei; Yang, Qing X; Smith, Michael B
2002 Jun;20(5):413-424, Magnetic resonance imaging
Susceptibility-induced perturbation of the static magnetic field by the human body during magnetic resonance imaging (MRI) leads to undesirable artifacts as well as valuable physiological information, as in functional MRI. The ability to calculate these perturbations for a multi-tissue human body model provides a powerful tool in designing hardware and acquisition methods for reducing the artifacts, and in relating observed image contrast to physiological origins. We have developed a method for calculating the static field in arbitrary 3D magnetic susceptibility distributions and performed calculations in a complete model of the human head and shoulders. The accuracy of our method was validated in regular geometries with known analytical solutions and in comparison with experimental results acquired from the head of the same human subject used for computer modeling. Results are presented in parts per million (ppm) deviation from the applied field strength and are valid for any imaging or spectroscopy system
— id: 149006, year: 2002, vol: 20, page: 413, stat: Journal Article,

Polarization of the RF field in a human head at high field: a study with a quadrature surface coil at 7.0 T
Wang, Jinghua; Yang, Qing X; Zhang, Xiaoliang; Collins, Christopher M; Smith, Michael B; Zhu, Xiao-Hong; Adriany, Gregor; Ugurbil, Kamil; Chen, Wei
2002 Aug;48(2):362-369, Magnetic resonance in medicine
The RF field intensity distribution in the human brain becomes inhomogeneous due to wave behavior at high field. This is further complicated by the spatial distribution of RF field polarization that must be considered to predict image intensity distribution. An additional layer of complexity is involved when a quadrature coil is used for transmission and reception. To study such complicated RF field behavior, a computer modeling method was employed to investigate the RF field of a quadrature surface coil at 300 MHz. Theoretical and experimental results for a phantom and the human head at 7.0 T are presented. The results are theoretically important and practically useful for high-field quadrature coil design and application
— id: 149005, year: 2002, vol: 48, page: 362, stat: Journal Article,

Analysis of wave behavior in lossy dielectric samples at high field
Yang, Qing X; Wang, Jinghua; Zhang, Xiaoliang; Collins, Christopher M; Smith, Michael B; Liu, Haiying; Zhu, Xiao-Hong; Vaughan, J Thomas; Ugurbil, Kamil; Chen, Wei
2002 May;47(5):982-989, Magnetic resonance in medicine
Radiofrequency (RF) field wave behavior and associated nonuniform image intensity at high magnetic field strengths are examined experimentally and numerically. The RF field produced by a 10-cm-diameter surface coil at 300 MHz is evaluated in a 16-cm-diameter spherical phantom with variable salinity, and in the human head. Temporal progression of the RF field indicates that the standing wave and associated dielectric resonance occurring in a pure water phantom near 300 MHz is greatly dampened in the human head due to the strong decay of the electromagnetic wave. The characteristic image intensity distribution in the human head is the result of spatial phase distribution and amplitude modulation by the interference of the RF traveling waves determined by a given sample-coil configuration. The numerical calculation method is validated with experimental results. The general behavior of the RF field with respect to the average brain electrical properties in a frequency range of 42-350 MHz is also analyzed
— id: 149007, year: 2002, vol: 47, page: 982, stat: Journal Article,

Hope and despair: keys to the socio-psychodynamics of youth
Smith, M B
1983 Jul;53(3):388-399, American journal of orthopsychiatry
A psychology of hope and despair is offered, integrating findings from recent psychological research in application to the interpretation of unrest among youth in the 1960s, of present socially problematic behavior, and of response to life under threat of nuclear holocaust. Survey data suggest a complex pattern: the majority of youth are hopeful about their own immediate future, but far fewer are optimistic about their nation and the world. Implications for individual action and social policy are offered
— id: 140462, year: 1983, vol: 53, page: 388, stat: Journal Article,

Seizures associated with a high plasma maprotiline level
Smith, M; Angrist, B; Cooper, T
1983 Feb;3(1):57-58, Journal of clinical psychopharmacology
— id: 106696, year: 1983, vol: 3, page: 57, stat: Journal Article,

Differential assessments of "blindisms"
Smith, M A; Chethik, M; Adelson, E
1969 Oct;39(5):807-817, American journal of orthopsychiatry
— id: 145500, year: 1969, vol: 39, page: 807, stat: Journal Article,