Expertise:
Medical
Physicist with expertise in Magnetic Resonance Imaging (diffusion
tensor imaging, functional magnetic resonance imaging)
PROPELLER MRI: data acquisition
and image reconstruction:
PROPELLER imaging is an MRI data acquisition and reconstruction
technique with greatly reduced sensitivity to various sources
of image artifacts (geometric distortions related to B 0-inhomogeneities
and eddy currents, motion artifacts). However, the imaging
time in PROPELLER MRI is considerably longer than in acquisition
techniques such as echo-planar imaging (EPI). In the most
recent form of PROPELLER imaging, named Turboprop, data acquisition
is accelerated by reading out multiple lines of k-space in
a manner similar to the gradient and spin-echo (GRASE) sequence.
In this project we are investigating PROPELLER MRI data
acquisition and image reconstruction methods. We have recently
studied the effects of k-space under-sampling on the reconstructed
PROPELLER images as an alternative method to accelerate PROPELLER
MRI. We have discovered sampling patterns that are both time-efficient
(reduce acquisition time by 50% compared to that of a fully
sampled case) and result in images with very few artifacts.
Improving white matter fiber tractography
by means of PROPELLER MRI:
White matter fiber tractography by means of diffusion tensor
MRI is the only non-invasive method that can provide estimates
of brain structural connectivity. Tractography algorithms
are in general sensitive to noise, and image artifacts. However,
the conventional DTI data acquisition technique used for
fiber tractography is based on EPI, which suffers from severe
geometric distortions due to B 0 inhomogeneities, and eddy-current
artifacts. Turboprop-DTI is relatively immune to such artifacts.
Our goal in this project is to investigate the use of Turboprop-DTI
in tractography applications. We have recently shown that
Turboprop-DTI provides anatomically correct, undistorted
fiber-tracts throughout the brain.
Optimization of diffusion tensor imaging acquisition schemes:
Diffusion tensor imaging (DTI), is a noninvasive imaging
technique that can be used to probe, in vivo, the
intrinsic diffusion properties of deep tissues. DTI models
diffusion in each volume element of the brain with a diffusion
tensor D. The eigenvectors of the diffusion
tensor D define the local fiber tract direction
field and the eigenvalues are the diffusivities along these
directions. DTI has been applied in several studies in our
lab to infer the microstructural characteristics of the brain,
in normal, as well as, in disease conditions, such as cerebral
ischemia, acute stroke, epilepsy, psychiatric disorders and
traumatic brain injury. Precision in the estimation of the
elements of D, and consequently of the scalar
quantities derived from it, is crucial for many DTI studies.
For that reason, we are giving special attention in constructing
acquisition schemes that provide optimal estimates of D.
Early detection
of Alzheimer’s
disease:
Alzheimer’s
disease (AD) affects 5-10% of the population over the
age of 65 and an even higher percentage of the population
over 85, causing an impairment of recent memory function
and attention, a deterioration of language skills, visuospatial
orientation, abstract thinking and judgment, and alterations
of personality. Even though there are behavioral clinical
criteria to diagnose possible or probable AD, the definitive
diagnosis is based on post-mortem histopathological examination.
Possible treatments may benefit the most only those patients
who are diagnosed early. Our goal in this project is
to develop a non-invasive method to identify the signs of
early damage due to AD.
Electrical injury:
We have shown that electric fields of the magnitude and
duration likely to occur in electrical injury result in skeletal
muscle electroporation and subsequent tissue necrosis. The
goal of our project is to use MR imaging techniques to visualize
the effects of electrical injury in muscle. We have shown
that electrical injury leads to edema and increased T2 values.
Therefore, T2-weighted imaging can be used to localize the
injury, and estimate the volume of injured tissue.
Specific research projects:
-- PROPELLER MRI: data acquisition and image reconstruction
-- Improving white matter fiber tractography
by means of PROPELLER MRI
-- Optimization of diffusion tensor imaging acquisition
schemes
-- Early
detection of Alzheimer’s
disease
-- Diffusion tensor imaging in prenatal
stroke
-- White matter integrity in patients
with intermittent explosive disorder
-- Imaging electrical injury and quantifying
the outcome of therapy
Laboratory personnel:
Ashish Anil Tamhane, MS
Minzhi Gui
Huiling Peng
John Collins, MS
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