Alayar Kangarlu

Alayar Kangarlu
Columbia University | CU · Department of Psychiatry

PhD, Physics

About

123
Publications
14,482
Reads
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3,836
Citations
Citations since 2016
12 Research Items
1330 Citations
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Introduction
I am interested in development of imaging techniques for study of the brain and its functions to help exploring the etiology of psychiatric disorders. Also, I have been working on neuromodulation techniques such as transcranial magnetic stimulation (TMS) and its effect on fMRI signatures of brain networks.
Additional affiliations
March 2012 - present
New York State Psychiatric Institute
Position
  • Researcher
April 2004 - present
Columbia University
Position
  • Director, MRI Physics & Engineering
Description
  • Alayar Kangarlu leads the physics and engineering group at MRI research center at Columbia University in New York City. He is an associate professor at the department of Psychiatry and a senior physicist at NYSPI.
December 1995 - April 2004
The Ohio State University
Position
  • Reseach Scientist
Description
  • Built the 8 Tesla whole body MRI scanner and carried out research with it on important physics, engineering, and clinical isuues at high field.

Publications

Publications (123)
Chapter
Magnetic resonance is a versatile technology that has offered the medical field a powerful imaging technique, magnetic resonance imaging (MRI) that has revolutionised medicine for the past 4 decades. The magnetic field of MRI scanners plays a central role in the quality of images and as such there has been a relentless drive toward higher magnetic...
Article
Full-text available
Purpose Heating of gradient coils and passive shim components is a common cause of instability in the B0 field, especially when gradient intensive sequences are used. The aim of the study was to set a benchmark for typical drift encountered during MR spectroscopy (MRS) to assess the need for real-time field-frequency locking on MRI scanners by comp...
Article
Full-text available
Transcranial magnetic stimulation (TMS) is an approved intervention for treatment-resistant depression (TRD), but current targeting approaches are only partially successful. Our objectives were (1) to examine the feasibility of MRI-guided TMS in the clinical setting using a recently published surface-based, multimodal parcellation in patients with...
Article
Full-text available
There is increasing focus on use of resting-state functional connectivity (RSFC) analyses to subtype depression and to predict treatment response. To date, identification of RSFC patterns associated with response to electroconvulsive therapy (ECT) remain limited, and focused on interactions between dorsal prefrontal and regions of the limbic or def...
Article
Accurate and reliable quantification of brain metabolites measured in vivo using 1H magnetic resonance spectroscopy (MRS) is a topic of continued interest. Aside from differences in the basic approach to quantification, the quantification of metabolite data acquired at different sites and on different platforms poses an additional methodological ch...
Article
The development of brain circuits is coupled with changes in neurovascular coupling, which refers to the close relationship between neural activity and cerebral blood flow (CBF). Studying the characteristics of CBF during resting state in developing brain can be a complementary way to understand the functional connectivity of the developing brain....
Chapter
Magnetic resonance is a powerful phenomenon that has offered the medical field an imaging technique, magnetic resonance imaging (MRI) that has revolutionized medicine for the past 3 decades. The magnetic field of MRI scanners plays a central role in the quality of images and as such there has been a relentless drive toward higher magnetic fields. T...
Chapter
Magnetic resonance imaging (MRI) allows detection of signal from constituent of biological tissues. Hydrogen (1H) is the most widely used element from which spectra and images are detected due to its abundance and high sensitivity manifested in its gyromagnetic ratio. The high contrast for soft tissue have afforded scientists invaluable information...
Poster
Full-text available
Diffusion Tensor Imaging (DTI) is very sensitive to subject motion. This can result in artifacts which are especially severe in DTI data of infants, children, and clinical populations, such as those with attention deficit hyperactivity disorder. The detection and correction of motion is therefore important for DTI studies of these populations, in o...
Poster
Full-text available
Diffusion Tensor Imaging (DTI) is a useful tool for noninvasive study of white matter properties and structural connectivity in the living brain, by measuring the anisotropic diffusion of water in white matter tract, such as fractional anisotropy (FA). However, DTI data often suffer from noise and artifacts caused by thermal radio frequency noise a...
Article
Many computational models assume that reinforcement learning relies on changes in synaptic efficacy between cortical regions representing stimuli and striatal regions involved in response selection, but this assumption has thus far lacked empirical support in humans. We recorded hemodynamic signals with fMRI while participants navigated a virtual m...
Article
Proton magnetic resonance spectroscopic imaging (1H MRSI) has been used for the in vivo measurement of intramyocellular lipids (IMCLs) in human calf muscle for almost two decades, but the low spectral resolution between extramyocellular lipids (EMCLs) and IMCLs, partially caused by the magnetic field inhomogeneity, has hindered the accuracy of spec...
Article
Full-text available
Emotions elicited by interpersonal versus non-interpersonal experiences have different effects on neurobiological functioning in both animals and humans. However, the extent to which the brain circuits underlying interpersonal and non-interpersonal emotions are distinct still remains unclear. The goal of our study was to assess whether different ne...
Article
Full-text available
Dysfunctional learning systems are thought to be central to the pathogenesis of and impair recovery from addictions. The functioning of the brain circuits for episodic memory or learning that support goal-directed behavior has not been studied previously in persons with cocaine dependence (CD). Thirteen abstinent CD and 13 healthy participants unde...
Article
Full-text available
In multiple sclerosis (MS), MRI is the most important paraclinical tool used to inform diagnosis and for monitoring disease evolution, either natural or modified by treatment. The increased availability of ultra-high-field magnets (7 Tesla or higher) gives rise to questions about the main benefits of and challenges for their use in patients with MS...
Article
Differing imaging modalities provide unique channels of information to probe differing aspects of the brain's structural or functional organization. In combination, differing modalities provide complementary and mutually informative data about tissue organization that is more than their sum. We acquired and spatially coregistered data in four MRI m...
Article
Full-text available
Schizophrenia is associated with extensive neurocognitive and behavioral impairments. Studies indicate that N-acetylaspartate (NAA), a marker of neuronal integrity, and choline, a marker of cell membrane turnover and white matter integrity, may be altered in schizophrenia. Davunetide is a neurotrophic peptide that can enhance cognitive function in...
Article
Full-text available
Compressed sensing (CS), parallel imaging and partial Fourier (PF) acquisition are all effective methods to reduce k-space sampling and therefore accelerate MR acquisition. The combined use of these methods gives us more options to balance the needs for scan speed and image quality. We conducted simulations on full k-space data to demonstrate the p...
Article
Full-text available
Multisection magnetic resonance spectroscopic imaging is a widely used pulse sequence that has distinct advantages over other spectroscopic imaging sequences, such as dynamic shimming, large region-of-interest coverage within slices, and rapid data acquisition. It has limitations, however, in the number of slices that can be acquired in realistic s...
Article
Full-text available
This study tested whether mothers with interpersonal violence-related posttraumatic stress disorder (IPV-PTSD) vs healthy controls (HC) would show greater limbic and less frontocortical activity when viewing young children during separation compared to quiet play. Mothers of 20 children (12–42 months) participated: 11 IPV-PTSD mothers and 9 HC with...
Article
Full-text available
The contribution of microenvironment to tumor growth has important implications for optimizing chemotherapeutic response and understanding the biology of recurrent tumors. In this study, we tested the effects of locally administered topotecan on a rat model of glioblastoma that is induced by intracerebral injection of PDGF (platelet-derived growth...
Article
Although temporo-parietal cortices mediate spatial navigation in animals and humans, the neural correlates of reward-based spatial learning are less well known. Twenty-five healthy adults performed a virtual reality fMRI task that required learning to use extra-maze cues to navigate an 8-arm radial maze and find hidden rewards. Searching the maze i...
Article
Full-text available
The circumplex model of affect construes all emotions as linear combinations of 2 independent neurophysiological dimensions, valence and arousal. We used functional magnetic resonance imaging to identify the neural networks subserving valence and arousal, and we assessed, in 10 participants, the associations of the BOLD (blood oxygen level-dependen...
Article
Imaging of human brain function is possible only through a few techniques of which magnetic resonance is the safest and most widely used. The soft tissue contrast and high resolution functional maps of the human brain are making a profound contribution to our understanding of the brain function. Resolution and strength of activation signal in fMRI...
Article
Magnetic Resonance Imaging (MRI) is a promising tool for the noninvasive, longitudinal study of developing primate brains. We developed a protocol to scan pregnant baboons serially at 3T for up to 3h per session. This protocol includes procedures for animal preparation, anesthesia, MRI scanning, and post-scan animal care. We applied this protocol t...
Article
This article explores the role of high-field (HF) MR imaging in medicine. It analyzes advantages of HF MR imaging in application to human subjects and how best they can be used to unravel the secrets of diseases, such as multiple sclerosis. Special emphasis is placed on morphologic imaging to highlight the role of soft tissue contrast, MR spectrosc...
Article
We aimed to study the neural processing of emotion-denoting words based on a circumplex model of affect, which posits that all emotions can be described as a linear combination of two neurophysiological dimensions, valence and arousal. Based on the circumplex model, we predicted a linear relationship between neural activity and incremental changes...
Chapter
Full-text available
In recent years, functional magnetic resonance imaging (fMRI) has become a widely used approach for neuroscience. However, this method has the potential to be improved with regard to both spatial and temporal resolution. The blood-oxygenation level-dependent contrast (BOLD) represents signal changes in T2 or T2* weighted images. These sequences are...
Article
To optimize the homogeneity and efficiency of the B(1) magnetic field of a four-ring birdcage head coil that is double-tuned at the Larmor frequencies of both (31)P and (1)H and optimized to acquire magnetic resonance spectroscopy (MRS) data at 3T for the study of infants. We developed a finite difference time domain (FDTD) tool in-house to iterati...
Article
Direct observational data on the development of the brains of human and nonhuman primates is on remarkably scant, and most of our understanding of primate brain development is extrapolated from findings in rodent models. Magnetic resonance imaging (MRI) is a promising tool for the noninvasive, longitudinal study of the developing primate brain. We...
Article
Increasing evidence supports the existence of distinct neural systems that subserve two dimensions of affect--arousal and valence. Ten adult participants underwent functional magnetic resonance imaging during which they were presented a range of standardized faces and then asked, during the scan, to rate the emotional expressions of the faces along...
Article
Full-text available
Computational methods such as the finite difference time domain (FDTD) play an important role in simulating radiofrequency (RF) coils used in magnetic resonance imaging (MRI). The choice of absorbing boundary conditions affects the final outcome of such studies. We have used FDTD to assess the Berenger's perfectly matched layer (PML) as an absorbin...
Article
To study the specific absorption rates (SAR) associated with implantable devices at 3T and 7 T. Studies were carried out utilizing a finite difference time domain (FDTD) model that treats the radio frequency (RF) coil and an anatomically detailed human head mesh as a single system. Analyses were performed at 3 T and 7 T for different orientations a...
Article
While magnetic resonance images essentially contain a map of the both circularly polarized components of the RF transverse magnetic fields (B(1) field), the thermal heat and electromagnetic power deposition is generated by the associated electric fields. Measurement of electric field distributions/intensities across a sample yields an indirect indi...
Article
Full-text available
Conventional imaging of ex-vivo brain at 1.5T in multiple sclerosis (MS) detects only a small fraction of the gray matter cerebral cortical lesions that can be detected by pathology. Our purpose was to examine if imaging at 8T can detect plaques in cortical gray matter (CGM) not evident at 1.5T. An ex-vivo brain obtained at autopsy from a patient w...
Article
Full-text available
Introduction Proliferation of high and ultra high field scanners at a staggering rate will inevitably be ensued with the daunting question of implantable devices compatibility and safety (1-3). This fact compounded by the technical difficulty of the experimental assessment of implantable devices compatibility gives credence to computational techniq...
Article
To correct eddy-current artifacts in diffusion tensor (DT) images without the need to obtain auxiliary scans for the sole purpose of correction. DT images are susceptible to distortions caused by eddy currents induced by large diffusion gradients. We propose a new postacquisition correction algorithm that does not require any auxiliary reference sc...
Article
Tractography algorithms for diffusion tensor (DT) images consecutively connect directions of maximal diffusion across neighboring DTs in order to reconstruct the 3-dimensional trajectories of white matter tracts in vivo in the human brain. The performance of these algorithms, however, is strongly influenced by the amount of noise in the images and...
Article
This study was performed to non-invasively visualize and characterize osteochondral (OC) repair in ex vivo goat stifles using an 8 T magnetic resonance imaging (MRI) scanner and to compare the MR morphology with images obtained from 1.5 T, gross morphology and histology. Mature, neutered male goats were assigned to an 8-week (n = 4) or 16-week (n =...
Article
In this paper, two TEM resonators were evaluated experimentally and numerically at 8 tesla (T) (340 MHz for 1H imaging). The coils were constructed to be 21.2-cm long (standard) and 11-cm long (a proposed less claustrophobic design). The experimental evaluation was done on a single cadaver using an ultra high field, 8 T, whole-body magnet. The nume...
Article
The purpose of this study was to quantify the spatial resolution of microscopic arteries on magnetic resonance images acquired at 8 Tesla (T). Techniques similar to those used for standard MRI of the human brain in vivo at 8 T were utilized to generate high-resolution gradient echo (GE) images of a whole postmortem human brain whose common carotid...
Article
Deterioration of radiofrequency (RF) inhomogeneity with increasing static magnetic field in magnetic resonance imaging (MRI) is one of the fundamental challenges preventing their clinical rendition and posing safety hazards. Variation in RF coil designs could help redistribute RF energy absorption over the imaged object. This work is intended to de...
Article
Full-text available
Imaging methods are currently being optimized in an attempt to assess and monitor angiogenesis in vivo. The purpose of this investigation was to determine whether areas of apparently increased tumor vascularity, as identified on 8-T gradient-echo (GE) imaging of a known glioblastoma multiforme (GBM), corresponds to foci of increased microvascularit...
Article
To quantify the minimum magnetic resonance imaging (MRI) spatial resolution of the visible deoxygenated microscopic vessels of the human brain at 8 T. This study compared 8-T gradient echo (GE) images of a human cadaver brain having an in-plane resolution of 195 x 195 microm to corresponding digital photographs of 205 cryomicrotome sections of the...
Article
The field strength of the static field in MRI has increased from 0.015 to 12 Tesla (T) during the last 25 years, which is about an 800 fold increase. In addition to low- and high field systems (1.5-4 T), ultra-high field systems with field strengths above 4 T are now available for human MRI. The extension of non-significant risk status for clinical...
Article
Full-text available
Die Feldstärke des statischen Grundfeldes hat sich in der MRT in den letzten 25 Jahren von 0,015 auf bis zu 12 Tesla (T) mehr als verachthundertfacht. Neben Niedrig- und Hochfeldsystemen (1,5–4 T) stehen nun Ultrahochfeldsysteme mit Feldstärken oberhalb von 4 T zur MR-Tomographie und Spektroskopie am Menschen zur Verfügung. Die Erweitung der Unbede...
Conference Paper
HTML Purpose: Imaging the cortical plaques of multiple sclerosis which has until now been impossible using conventional imaging at 1.5 T. The improved signal-to-noise ratio of imaging at 8T provided an opportunity to examine these plaques. Methods and Materials: Postmortem formalin-fixed brain slices from an MS patient were examined for cortical pa...
Article
Full-text available
In this study, we compared 8-T gradient-echo MR images of the microvasculature in the live human brain with images of the unembalmed and embalmed postmortem brain. Small vessels were well visualized in the live brain and even better seen in the unembalmed postmortem brain, but they could not be visualized in the embalmed postmortem brain. These fin...
Article
To discover whether there was a measurable alteration in cognitive performance in humans when exposed to a static magnetic field of 8 Tesla (T). Twenty-five normal human subjects were evaluated at both 0.05 and 8 T in a randomized order. Six standardized neuropsychological tests were administered and auditory reaction times were assessed. The cogni...
Article
PurposeTo determine if increasing static magnetic field strength exposures up to 8 Tesla (T) affect vital signs or electrocardiograms (ECGs) in normal human volunteers.Materials and Methods We studied 25 normal subjects, consisting of 19 men and six women, ages 24–53 years. The vital signs and ECGs of the subjects were measured 14 times inside and...
Article
Water diffusion within the structure of a brain extracellular space is analyzed numerically for various diffusion parameters of brain tissue namely extracellular space porosity and tortuosity. An algorithm for predicting diffusion pattern of water molecules within human brain considering the mechanics of water diffusion within porous media is devel...
Article
Water diffusion within the brain is studied numerically for various clinical conditions. The numerical procedure used in this work is based on the Galerkin weighted residual method of finite-element formulation. A wide range of pertinent parameters such as Lewis number, cell volume, and the buoyancy ratio are considered in the present study. Compar...