Research Topics
| Andrew AlexanderSummaryAffiliation: University of Wisconsin Country: USA Publications
Research Grants
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Detail Information
Publications
Characterization of cerebral white matter properties using quantitative magnetic resonance imaging stainsAndrew L Alexander
Department of Medical Physics, University of Wisconsin, Madison, Wisconsin 53705, USA
Brain Connect 1:423-46. 2011..This article provides an overview of the qMRI stain mechanisms, acquisition and analysis strategies, and applications for these qMRI stains...- Diffusion tensor imaging of the brainAndrew L Alexander
Department of Medical Physics, University of Wisconsin Madison, Madison, Wisconsin 53706, USA
Neurotherapeutics 4:316-29. 2007..g., radial or axial). To maximize the specificity and better characterize the tissue microstructure, future studies should use multiple diffusion tensor measures (e.g., MD and FA, or D(a) and D(r))... 
Comparison of diffusion tensor imaging measurements at 3.0 T versus 1.5 T with and without parallel imagingAndrew L Alexander
Department of Medical Physics, University of Wisconsin, Madison, WI 53706, USA
Neuroimaging Clin N Am 16:299-309, xi. 2006..5 T to 3.0 T, but was reduced by 50% when using parallel imaging. In summary, DTI studies at 3.0 T using parallel imaging will provide significantly improved DTI measurements relative to studies at 1.5 T...- Diffusion tensor imaging of the corpus callosum in AutismAndrew L Alexander
Department of Medical Physics, University of Wisconsin, Madison, WI, USA
Neuroimage 34:61-73. 2007..These results suggest that the microstructure of the corpus callosum is affected in autism, which may be related to nonverbal cognitive performance... 
An experimental evaluation of diffusion tensor image segmentation using graph-cutsDeok Han
Waisman Laboratory for Brain Imaging and Behavior, University of Wisconsin Madison, WI, USA
Conf Proc IEEE Eng Med Biol Soc 2009:5653-6. 2009..Overall, the graph cuts method performed well, giving an average segmentation accuracy of about 0.90, 0.77 and 0.88 for WM, GM and CSF respectively in terms of volume overlap(VO)...- Amygdala volume and nonverbal social impairment in adolescent and adult males with autismBrendon M Nacewicz
Waisman Laboratory for Brain Imaging and Behavior, University of Wisconsin-Madison, Waisman Center, 1500 Highland Avenue, Madison, WI 53705, USA
Arch Gen Psychiatry 63:1417-28. 2006..047). CONCLUSIONS: These findings best support a model of amygdala hyperactivity that could explain most volumetric findings in autism. Further psychophysiological and histopathological studies are indicated to confirm these findings... - Diffusion tensor imaging of cerebral white matter: a pictorial review of physics, fiber tract anatomy, and tumor imaging patternsBrian J Jellison
Department of Radiology, University of Wisconsin Hospital and Clinics, 600 Highland Avenue, E3/311 CSC, Madison, WI 53792-3252, USA
AJNR Am J Neuroradiol 25:356-69. 2004 - Investigation of anomalous estimates of tensor-derived quantities in diffusion tensor imagingCheng Guan Koay
Department of Physics, University of Wisconsin Madison, Madison, Wisconsin, USA
Magn Reson Med 55:930-6. 2006..Simulation results show that the CNLS method is, in terms of mean squared error for estimating trace and FA, the most effective method for correcting negative eigenvalues... - Quantitative analysis of diffusion tensor orientation: theoretical frameworkYu-Chien Wu
Department of Medical Physics, University of Wisconsin, Madison 53705, USA
Magn Reson Med 52:1146-55. 2004..This novel approach distills the rich, 3D information available from the diffusion tensor into a form that lends itself to quantitative analysis and statistical hypothesis testing... - Diffusion tensor imaging of white matter in the superior temporal gyrus and temporal stem in autismJee Eun Lee
Waisman Laboratory for Brain Imaging and Behavior, Waisman Center, Madison, WI, United States
Neurosci Lett 424:127-32. 2007..These results suggest that white matter microstructure in autism is abnormal in these temporal lobe regions, which is consistent with theories of aberrant brain connectivity in autism... - Contextual modulation of amygdala responsivity to surprised facesHackjin Kim
University of Wisconsin-Madison, Madison, WI 53705, USA
J Cogn Neurosci 16:1730-45. 2004..Connectivity analyses identified candidate cortical-subcortical systems subserving this modulation... - Repetitive transcranial magnetic stimulation dissociates working memory manipulation from retention functions in the prefrontal, but not posterior parietal, cortexBradley R Postle
University of Wisconsin, USA
J Cogn Neurosci 18:1712-22. 2006..In the SPL, they illustrate the importance of supplementing the fundamentally correlational data from neuroimaging with a disruptive method, which affords stronger inference about structure-function relations... - Intraoperative intracerebral MRI-guided navigation for accurate targeting in nonhuman primatesMarina E Emborg
Preclinical Parkinson s Research Program, Wisconsin National Primate Research Center, University of Wisconsin Madison, 1223 Capitol Court, Madison, WI 53715, USA
Cell Transplant 19:1587-97. 2010..5 mm. Our results in nonhuman primates confirm the accuracy of intraoperative MRI intracerebral navigation combined with an adaptable, pivot point-based targeting system and validates its use for preclinical intracerebral procedures... - Gaze fixations predict brain activation during the voluntary regulation of picture-induced negative affectCarien M van Reekum
Laboratory for Affective Neuroscience, Department of Psychology, University of Wisconsin Madison, Madison, WI 53706, USA
Neuroimage 36:1041-55. 2007..Furthermore, this variation in gaze fixation accounted for substantial amounts of variance in brain activation. These data point to the importance of controlling for gaze fixation in studies of emotion regulation that use visual stimuli... - Hybrid diffusion imagingYu Chien Wu
Department of Radiology, University of Wisconsin Madison, Madison, WI, USA
Neuroimage 36:617-29. 2007..In this study, an HYDI encoding scheme with 102 diffusion-weighted measurements was obtained over most of the human cerebrum in under 30 min... - Gaze-fixation, brain activation, and amygdala volume in unaffected siblings of individuals with autismKim M Dalton
Waisman Center, University of Wisconsin, Madison, Wisconsin, USA
Biol Psychiatry 61:512-20. 2007..These characteristics primarily affect the social aspects of language, communication, and human interaction. The current research focuses on possible neurobehavioral characteristics associated with the broad autism phenotype... - Individual differences in amygdala and ventromedial prefrontal cortex activity are associated with evaluation speed and psychological well-beingCarien M van Reekum
University of Wisconsin Madison, Madison, WI 52706, USA
J Cogn Neurosci 19:237-48. 2007.... - A method for calibrating diffusion gradients in diffusion tensor imagingYu Chien Wu
Department of Radiology, University of Wisconsin Madison, Madison, WI, USA
J Comput Assist Tomogr 31:984-93. 2007..To calibrate and correct the gradient errors including gradient amplitude scaling errors, background/imaging gradients, and residual gradients in diffusion tensor imaging (DTI)... - Effect of Alzheimer disease risk on brain function during self-appraisal in healthy middle-aged adultsSterling C Johnson
Geriatric Research Education and Clinical Center, William S Middleton Memorial Veterans Hospital, 2500 Overlook Terrace, Madison, WI 53705, USA
Arch Gen Psychiatry 64:1163-71. 2007.... - White matter is altered with parental family history of Alzheimer's diseaseBarbara B Bendlin
Geriatric Research Educational and Clinical Center, William S Middleton Memorial Veterans Hospital, Madison, WI, USA
Alzheimers Dement 6:394-403. 2010..We examined the main effects of family history and APOE varepsilon4 on brain integrity, in addition to assessing possible additive effects of these two risk factors... - White matter in aging and cognition: a cross-sectional study of microstructure in adults aged eighteen to eighty-threeBarbara B Bendlin
Geriatric Research Educational and Clinical Center, William S Middleton Memorial Veterans Hospital, Madison, Wisconsin 53705, USA
Dev Neuropsychol 35:257-77. 2010..The complex relationships between cognition, white matter microstructure, and white matter volume still require further investigation... - Classification in DTI using shapes of white matter tractsNagesh Adluru
Dept of Psychology, Brigham Young Univ, UT, USA
Conf Proc IEEE Eng Med Biol Soc 2009:2719-22. 2009.... - A study of diffusion tensor imaging by tissue-specific, smoothing-compensated voxel-based analysisJee Eun Lee
Waisman Laboratory for Brain Imaging and Behavior, Waisman Center, Madison, WI 53705, USA
Neuroimage 44:870-83. 2009..The T-SPOON method may be also applicable to other quantitative imaging maps such as T1 or T2 relaxometry, magnetization transfer, or PET tracer maps... - Computation of diffusion function measures in q-space using magnetic resonance hybrid diffusion imagingYu Chien Wu
Department of Radiology, University of Wisconsin Madison, 600 Highland Ave, Madison, WI 53792, USA
IEEE Trans Med Imaging 27:858-65. 2008..Although this study focused on data using the HYDI scheme, this computation approach may be applied to other diffusion sampling schemes including Cartesian diffusion spectrum imaging... - Automatic physiological waveform processing for FMRI noise correction and analysisDaniel J Kelley
Waisman Laboratory for Brain Imaging and Behavior, Waisman Center, University of Wisconsin, Madison, Wisconsin, United States of America
PLoS ONE 3:e1751. 2008..PhysioNoise consistently identifies physiological fluctuations for fMRI noise correction and also generates covariates for subsequent analyses of brain activation and connectivity... - Creating physical 3D stereolithograph models of brain and skullDaniel J Kelley
Waisman Laboratory for Brain Imaging and Behavior, Waisman Center, Madison, Wisconsin, United States of America
PLoS ONE 2:e1119. 2007..Compared to 2D images, VR and stereolithograph models provide an extra dimension that enhances both the quality of visual information and utility of surface visualization in neuroscience and medicine... - Hybrid diffusion imaging (HYDI)Andrew L Alexander
Waisman Laboratory for Brain Imaging and Behavior, University of Wisconsin, Madison, WI 53705, USA
Conf Proc IEEE Eng Med Biol Soc 1:2245-8. 2006..HYDI experiments were performed on the brains of healthy volunteers and the results are presented. Overall, HYDI is an efficient and promising method for characterizing complex diffusion in the human brain and potentially other tissues... - The cerebral response during subjective choice with and without self-referenceSterling C Johnson
William S Middleton VA Medical Center, Madison, WI 53705, USA
J Cogn Neurosci 17:1897-906. 2005..The findings suggest that self-referential processing, rather than subjective judgments among ambiguous response alternatives, accounted for the AMPFC and RSC response... - Bootstrap white matter tractography (BOOT-TRAC)Mariana Lazar
WM Keck Laboratory for Functional Brain Imaging and Behavior, University of Wisconsin, Madison, WI 53705, USA
Neuroimage 24:524-32. 2005..The approach was used to generate probabilistic connectivity maps between the cerebral peduncles and specific cortical regions... - An error analysis of white matter tractography methods: synthetic diffusion tensor field simulationsMariana Lazar
Department of Physics, University of Utah, Salt Lake City, UT 84112, USA
Neuroimage 20:1140-53. 2003..These models may be used in future studies to assess the level of confidence associated with a tractography result... - Efficient parametric encoding scheme for white matter fiber bundlesMoo K Chung
Waisman Laboratory for Brain Imaging and Behavior at the University of Wisconsin, Madison, WI, USA
Conf Proc IEEE Eng Med Biol Soc 2009:6644-7. 2009..As an illustration, we apply the proposed method in characterizing abnormal tracts that pass through the splenium of the corpus callosum in autistic subjects... - Less white matter concentration in autism: 2D voxel-based morphometryMoo K Chung
Department of Statistics, University of Wisconsin Madison, Madison, WI 53706, USA
Neuroimage 23:242-51. 2004..Further, it is shown that the less white matter concentration in the corpus callosum in autism is due to hypoplasia rather than atrophy... - Diffusion tensor eigenvector directional color imaging patterns in the evaluation of cerebral white matter tracts altered by tumorAaron S Field
Department of Radiology, University of Wisconsin Medical School, Madison, Wisconsin 53792 3252, USA
J Magn Reson Imaging 20:555-62. 2004..To categorize the varied appearances of tumor-altered white matter (WM) tracts on diffusion tensor eigenvector directional color maps... - Diffusion tensor imaging in cerebral tumor diagnosis and therapyAaron S Field
Departments of Radiology and Biomedical Engineering, University of Wisconsin, Madison, WI, USA
Top Magn Reson Imaging 15:315-24. 2004.... - Gaze fixation and the neural circuitry of face processing in autismKim M Dalton
Waisman Center, University of Wisconsin, 1500 Highland Avenue, Madison, Wisconsin 53705 2280, USA
Nat Neurosci 8:519-26. 2005..In addition, variation in eye fixation within autistic individuals was strongly and positively associated with amygdala activation across both studies, suggesting a heightened emotional response associated with gaze fixation in autism... - Stability of amygdala BOLD response to fearful faces over multiple scan sessionsTom Johnstone
W M Keck Laboratory for Functional Brain Imaging and Behavior, University of Wisconsin, WI 53705, USA
Neuroimage 25:1112-23. 2005..Future studies might manipulate the experimental design to either amplify or attenuate this variability, according to the goals of the research... - Cortical thickness analysis in autism with heat kernel smoothingMoo K Chung
Department of Statistics, University of Wisconsin, 1210 West Dayton Street, Madison, WI 53706, USA
Neuroimage 25:1256-65. 2005..As an illustration, we apply our methods in detecting the regions of abnormal cortical thickness in 16 high functioning autistic children via random field based multiple comparison correction that utilizes the new smoothing technique... - Axial asymmetry of water diffusion in brain white matterMariana Lazar
W M Keck Laboratory for Functional Brain Imaging and Behavior, Madison, WI 53705, USA
Magn Reson Med 54:860-7. 2005..This study shows that WM axial asymmetry causes anisotropic dispersion patterns in the estimated tract trajectories. The medium and minor eigenvector patterns may be useful for elucidating the local dispersion distributions of WM tracts... - Generation and visualization of four-dimensional MR angiography data using an undersampled 3-D projection trajectoryJing Liu
Department of Electrical and Computer Engineering, University of Wisconsin Madison, E3 311 Clinical Sciences Center, WI 53792 3252, USA
IEEE Trans Med Imaging 25:148-57. 2006..Results from volunteer and patient studies demonstrate the advantages of dynamic imaging with high spatial resolution... - Principal diffusion direction in peritumoral fiber tracts: Color map patterns and directional statisticsAaron S Field
Department of Radiology, University of Wisconsin, 600 Highland Avenue, CSC E3 311, Madison, WI 53792, USA
Ann N Y Acad Sci 1064:193-201. 2005..These examples serve to demonstrate our approach to the quantitation of regional diffusion tensor distributions using directional statistical methods... - Motion correction and the use of motion covariates in multiple-subject fMRI analysisTom Johnstone
Waisman Laboratory for Brain Imaging and Behavior, University of Wisconsin Madison, Madison, Wisconsin 53705, USA
Hum Brain Mapp 27:779-88. 2006..Based on these results, we present a general strategy for block designs, event-related designs, and hybrid designs to identify and eliminate probable motion artifacts while maximizing sensitivity to true activations... - Amygdala and ventromedial prefrontal cortex are inversely coupled during regulation of negative affect and predict the diurnal pattern of cortisol secretion among older adultsHeather L Urry
Waisman Laboratory for Brain Imaging and Behavior, University of Wisconsin Madison, Madison, Wisconsin 53706, USA
J Neurosci 26:4415-25. 2006..Individual differences yielded the predicted link between brain function while reducing negative affect in the laboratory and diurnal regulation of endocrine activity in the home environment... - Longitudinal changes in patients with traumatic brain injury assessed with diffusion-tensor and volumetric imagingBarbara B Bendlin
Geriatric Research Education and Clinical Center, William S Middleton Memorial Veterans Hospital, Madison, WI, USA
Neuroimage 42:503-14. 2008.... - Human amygdala responses during presentation of happy and neutral faces: correlations with state anxietyLeah H Somerville
W.M. Keck Laboratory for Functional Brain Imaging and Behavior, University of Wisconsin, Madison, Wisconsin 53705, USA
Biol Psychiatry 55:897-903. 2004..Here, an observed relationship between state anxiety and ventral amygdala response to happy versus neutral faces was explained by response to neutral faces... - Helium-3 MR q-space imaging with radial acquisition and iterative highly constrained back-projectionRafael L O'Halloran
Department of Medical Physics, University of Wisconsin, Madison, Wisconsin 53792, USA
Magn Reson Med 63:41-50. 2010..This technique represents the first demonstration of a spatially resolved hyperpolarized helium-3 q-space imaging technique and shows promise for microstructural evaluation of lung disease in three dimensions... - Myelin water fraction in human cervical spinal cord in vivoYijing Wu
Department of Medical Physics, University of Wisconsin Medical School, Madison, WI 53792-3252, USA
J Comput Assist Tomogr 30:304-6. 2006..This technical note reports the test-retest reproducibility of a short T2-based estimate of myelin content in human spinal cord in vivo... - A calorie-restricted diet decreases brain iron accumulation and preserves motor performance in old rhesus monkeysErik K Kastman
Geriatric Research Education and Clinical Center, William S Middleton Memorial Veterans Hospital, Madison, Wisconsin 53705, USA
J Neurosci 30:7940-7. 2010..Our observations suggest that the CR-induced benefit of reduced iron deposition and preserved motor function may indicate neural protection similar to effects described previously in aging rodent and primate species... - Diffusion tensor imaging of the corticospinal tract before and after mass resection as correlated with clinical motor findings: preliminary dataBryan J Laundre
Department of Radiology, University of Wisconsin Medical School, Madison, WI 53792-3252, USA
AJNR Am J Neuroradiol 26:791-6. 2005..Further study is warranted to define the role of DTI in planning tumor resections and predicting postoperative motor function... - Reduced evoked gamma oscillations in the frontal cortex in schizophrenia patients: a TMS/EEG studyFabio Ferrarelli
Department of Psychiatry, University of Wisconsin, Madison, WI, USA
Am J Psychiatry 165:996-1005. 2008..The authors investigated EEG responses in schizophrenia patients and healthy comparison subjects following the application of TMS to the premotor cortex... - Diffusion tensor imaging in an infant with traumatic brain swellingAaron S Field
Department of Radiology, University of Wisconsin Medical School, Madison, Wisconsin 53792-3252, USA
AJNR Am J Neuroradiol 24:1461-4. 2003..This case engenders important hypotheses regarding mechanisms of traumatic brain swelling and anisotropic diffusion of water in pathologic tissues... - Inverse amygdala and medial prefrontal cortex responses to surprised facesHackjin Kim
W M Keck Laboratory for Functional Brain Imaging, Department of Psychiatry, University of Wisconsin-Madison, 53705, USA
Neuroreport 14:2317-22. 2003.... - Diffusion-tensor imaging of white matter tracts in patients with cerebral neoplasmBrian P Witwer
Department ofNeurological Surgery, University of Wisconsin School of Medicine, Madison 53792, USA
J Neurosurg 97:568-75. 2002..Whether resection of these involved fibers results in subtle postoperative neurological deficits requires further systematic study... - White matter tractography using diffusion tensor deflectionMariana Lazar
Department of Physics, University of Utah, Salt Lake City, Utah, USA
Hum Brain Mapp 18:306-21. 2003..This approach is promising for mapping the organizational patterns of white matter in the human brain as well as mapping the relationship between major fiber trajectories and the location and extent of brain lesions... - Application of Brodmann's area templates for ROI selection in white matter tractography studiesPaul Thottakara
Waisman Laboratory for Brain Imaging and Behavior, The Waisman Center, 1500 Highland Avenue Madison, WI 53705, USA
Neuroimage 29:868-78. 2006..In the future, this method could be used to help elucidate relationships between function and anatomical structure... - Does fractional anisotropy have better noise immunity characteristics than relative anisotropy in diffusion tensor MRI? An analytical approachKhader M Hasan
Department of Radiology, University of Texas Medical School at Houston, Houston, Texas, USA
Magn Reson Med 51:413-7. 2004..This theoretical behavior was verified using both Monte Carlo simulations and bootstrap analysis of DT-MRI data acquired in a spherical water phantom and normal human subjects... - Correction of slab boundary artifact using histogram matchingEugene G Kholmovski
Department of Physics, University of Utah, Salt Lake City, Utah 84108, USA
J Magn Reson Imaging 15:610-7. 2002..To improve the imaging efficiency of multi-slab three-dimensional acquisitions by decreasing slab overlap and the number of blanked slices... - A functional magnetic resonance imaging predictor of treatment response to venlafaxine in generalized anxiety disorderPaul J Whalen
Department of Psychological and Brain Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA
Biol Psychiatry 63:858-63. 2008..Here, we sought to determine whether pretreatment amygdala and rostral ACC (rACC) reactivity to facial expressions could predict treatment outcomes in patients with generalized anxiety disorder (GAD)... - UNFOLD using a temporal subtraction and spectral energy comparison techniqueYijing Wu
Department of Physics, University of Utah, Salt Lake City, Utah, USA
Magn Reson Med 48:559-64. 2002..The combination resulted in a factor of 4 improvement in acquisition speed. Application of this method to a time-resolved, contrast-enhanced flow phantom study is presented...
Research Grants
- DIFFUSION MRI OF THE HUMAN BRAINAndrew Alexander; Fiscal Year: 2003..A new model of tissue diffusion with two tensor components will be evaluated. This project is a comprehensive approach to improving the accuracy and understanding of white matter mapping techniques within in the human brain. ..
- Structural & Functional Measures of Brain DevelopmentAndrew Alexander; Fiscal Year: 2004..Future studies of brain development in children with developmental disabilities (e.g., Autism, Fragile X, Downs, etc.) will be designed and performed based upon the results from this study. ..
- DIFFUSION MRI OF THE HUMAN BRAINAndrew Alexander; Fiscal Year: 2007..Pilot studies will be performed to evaluate if these innovative diffusion imaging methods are promising for clinical applications. ..