Publications by Year: 2010

Tina Kapur, Clare M. Tempany, and Ferenc A. Jolesz. 2010. “Proceedings of the 3rd Image Guided Therapy Workshop.” Image Guided Therapy Workshop 3, Pp. 1-87. 2010 IGT Workshop Proceedings
Thomas Kahn, Ferenc A Jolesz, and Jonathan S Lewin. 2010. “Proceedings of the 8th Interventional MRI Symposium.” 8th Interventional MRI Symposium 8, Pp. 1-340. 2010 iMRI Symposium Proceedings
Tzu-Cheng Chao, Hsiao-Wen Chung, Scott W Hoge, and Bruno Madore. 2010. “A 2D MTF approach to evaluate and guide dynamic imaging developments.” Magn Reson Med, 63, 2, Pp. 407-18.Abstract
As the number and complexity of partially sampled dynamic imaging methods continue to increase, reliable strategies to evaluate performance may prove most useful. In the present work, an analytical framework to evaluate given reconstruction methods is presented. A perturbation algorithm allows the proposed evaluation scheme to perform robustly without requiring knowledge about the inner workings of the method being evaluated. A main output of the evaluation process consists of a two-dimensional modulation transfer function, an easy-to-interpret visual rendering of a method's ability to capture all combinations of spatial and temporal frequencies. Approaches to evaluate noise properties and artifact content at all spatial and temporal frequencies are also proposed. One fully sampled phantom and three fully sampled cardiac cine datasets were subsampled (R = 4 and 8) and reconstructed with the different methods tested here. A hybrid method, which combines the main advantageous features observed in our assessments, was proposed and tested in a cardiac cine application, with acceleration factors of 3.5 and 6.3 (skip factors of 4 and 8, respectively). This approach combines features from methods such as k-t sensitivity encoding, unaliasing by Fourier encoding the overlaps in the temporal dimension-sensitivity encoding, generalized autocalibrating partially parallel acquisition, sensitivity profiles from an array of coils for encoding and reconstruction in parallel, self, hybrid referencing with unaliasing by Fourier encoding the overlaps in the temporal dimension and generalized autocalibrating partially parallel acquisition, and generalized autocalibrating partially parallel acquisition-enhanced sensitivity maps for sensitivity encoding reconstructions.
Serena H Wong, Mario Kupnik, Ronald D Watkins, Kim Butts-Pauly, and Butrus Pierre T Khuri-Yakub. 2010. “Capacitive micromachined ultrasonic transducers for therapeutic ultrasound applications.” IEEE Trans Biomed Eng, 57, 1, Pp. 114-23.Abstract
Therapeutic ultrasound guided by MRI is a noninvasive treatment that potentially reduces mortality, lowers medical costs, and widens accessibility of treatments for patients. Recent developments in the design and fabrication of capacitive micromachined ultrasonic transducers (CMUTs) have made them competitive with piezoelectric transducers for use in therapeutic ultrasound applications. In this paper, we present the first designs and prototypes of an eight-element, concentric-ring, CMUT array to treat upper abdominal cancers. This array was simulated and designed to focus 30-50 mm into tissue, and ablate a 2- to 3-cm-diameter tumor within 1 h. Assuming a surface acoustic output pressure of 1 MPa peak-to-peak (8.5 W/cm (2)) at 2.5 MHz, we simulated an array that produced a focal intensity of 680 W/cm (2) when focusing to 35 mm. CMUT cells were then designed to meet these frequency and surface acoustic intensity specifications. These cell designs were fabricated as 2.5 mm x 2.5 mm test transducers and used to verify our models. The test transducers were shown to operate at 2.5 MHz with an output pressure of 1.4 MPa peak-to-peak (16.3 W/cm (2)). With this CMUT cell design, we fabricated a full eight-element array. Due to yield issues, we only developed electronics to focus the four center elements of the array. The beam profile of the measured array deviated from the simulated one because of the crosstalk effects; the beamwidth matched within 10% and sidelobes increased by two times, which caused the measured gain to be 16.6 compared to 27.4.
Ruth E Propper, Lauren J O'Donnell, Stephen Whalen, Yanmei Tie, Isaiah H Norton, Ralph O Suarez, Lilla Zollei, Alireza Radmanesh, and Alexandra J Golby. 2010. “A combined fMRI and DTI examination of functional language lateralization and arcuate fasciculus structure: Effects of degree versus direction of hand preference.” Brain Cogn, 73, 2, Pp. 85-92.Abstract
The present study examined the relationship between hand preference degree and direction, functional language lateralization in Broca's and Wernicke's areas, and structural measures of the arcuate fasciculus. Results revealed an effect of degree of hand preference on arcuate fasciculus structure, such that consistently-handed individuals, regardless of the direction of hand preference, demonstrated the most asymmetric arcuate fasciculus, with larger left versus right arcuate, as measured by DTI. Functional language lateralization in Wernicke's area, measured via fMRI, was related to arcuate fasciculus volume in consistent-left-handers only, and only in people who were not right hemisphere lateralized for language; given the small sample size for this finding, future investigation is warranted. Results suggest handedness degree may be an important variable to investigate in the context of neuroanatomical asymmetries.
Ralph O Suarez, Alexandra J Golby, Stephen Whalen, Susumu Sato, William H Theodore, Conrad V Kufta, Orrin Devinsky, Marshall Balish, and Edward B Bromfield. 2010. “Contributions to singing ability by the posterior portion of the superior temporal gyrus of the non-language-dominant hemisphere: first evidence from subdural cortical stimulation, Wada testing, and fMRI.” Cortex, 46, 3, Pp. 343-53.Abstract

INTRODUCTION: Although the substrates that mediate singing abilities in the human brain are not well understood, invasive brain mapping techniques used for clinical decision making such as intracranial electro-cortical testing and Wada testing offer a rare opportunity to examine music-related function in a select group of subjects, affording exceptional spatial and temporal specificity. METHODS: We studied eight patients with medically refractory epilepsy undergoing indwelling subdural electrode seizure focus localization. All patients underwent Wada testing for language lateralization. Functional assessment of language and music tasks was done by electrode grid cortical stimulation. One patient was also tested non-invasively with functional magnetic resonance imaging (fMRI). Functional organization of singing ability compared to language ability was determined based on four regions-of-interest (ROIs): left and right inferior frontal gyrus (IFG), and left and right posterior superior temporal gyrus (pSTG). RESULTS: In some subjects, electrical stimulation of dominant pSTG can interfere with speech and not singing, whereas stimulation of non-dominant pSTG area can interfere with singing and not speech. Stimulation of the dominant IFG tends to interfere with both musical and language expression, while non-dominant IFG stimulation was often observed to cause no interference with either task; and finally, that stimulation of areas adjacent to but not within non-dominant pSTG typically does not affect either ability. Functional fMRI mappings of one subject revealed similar music/language dissociation with respect to activation asymmetry within the ROIs. CONCLUSION: Despite inherent limitations with respect to strictly research objectives, invasive clinical techniques offer a rare opportunity to probe musical and language cognitive processes of the brain in a select group of patients.

Claus Reinsberger, Naoaki Tanaka, Andrew J Cole, Jong Woo Lee, Barbara A Dworetzky, Edward B Bromfield, Lorie Hamiwka, Blaise F Bourgeois, Alexandra J Golby, Joseph R Madsen, and Steven M Stufflebeam. 2010. “Current Dipole Orientation and Distribution of Epileptiform Activity Correlates with Cortical Thinning in Left Mesiotemporal Epilepsy.” Neuroimage, 52, 4, Pp. 1238-42.Abstract

To evaluate cortical architecture in mesial temporal lobe epilepsy (MTLE) with respect to electrophysiology, we analyze both magnetic resonance imaging (MRI) and magnetoencephalography (MEG) in 19 patients with left MTLE. We divide the patients into two groups: 9 patients (Group A) have vertically oriented antero-medial equivalent current dipoles (ECDs). 10 patients (Group B) have ECDs that are diversely oriented and widely distributed. Group analysis of MRI data shows widespread cortical thinning in Group B compared with Group A, in the left hemisphere involving the cingulate, supramarginal, occipitotemporal and parahippocampal gyri, precuneus and parietal lobule, and in the right hemisphere involving the fronto-medial, -central and -basal gyri and the precuneus. These results suggest that regardless of the presence of hippocampal sclerosis, in a subgroup of patients with MTLE a large cortical network is affected. This finding may, in part, explain the unfavorable outcome in some MTLE patients after epilepsy surgery.

Stephan E Maier, Yanping Sun, and Robert V Mulkern. 2010. “Diffusion imaging of brain tumors.” NMR Biomed, 23, 7, Pp. 849-64.Abstract
MRI offers a tremendous armamentarium of different methods that can be employed in brain tumor characterization. MR diffusion imaging has become a widely accepted method to probe for the presence of fluid pools and molecular tissue water mobility. For most clinical applications of diffusion imaging, it is assumed that the diffusion signal vs diffusion weighting factor b decays monoexponentially. Within this framework, the measurement of a single diffusion coefficient in brain tumors permits an approximate categorization of tumor type and, for some tumors, definitive diagnosis. In most brain tumors, when compared with normal brain tissue, the diffusion coefficient is elevated. The presence of peritumoral edema, which also exhibits an elevated diffusion coefficient, often precludes the delineation of the tumor on the basis of diffusion information alone. Serially obtained diffusion data are useful to document and even predict the cellular response to drug or radiation therapy. Diffusion measurements in tissues over an extended range of b factors have clearly shown that the monoparametric description of the MR diffusion signal decay is incomplete. Very high diffusion weighting on clinical systems requires substantial compromise in spatial resolution. However, after suitable analysis, superior separation of malignant brain tumors, peritumoral edema and normal brain tissue can be achieved. These findings are also discussed in the light of tissue-specific differences in membrane structure and the restrictions exerted by membranes on diffusion. Finally, measurement of the directional dependence of diffusion permits the assessment of white matter integrity and dislocation. Such information, particularly in conjunction with advanced post-processing, is considered to be immensely useful for therapy planning. Diffusion imaging, which permits monoexponential analysis and provides directional diffusion information, is performed routinely in brain tumor patients. More advanced methods require improvement in acquisition speed and spatial resolution to gain clinical acceptance.
James J Levitt, Marek Kubicki, Paul G Nestor, Hal Ersner-Hershfield, C-F Westin, Jorge L Alvarado, Ron Kikinis, Ferenc A Jolesz, Robert W McCarley, and Martha E Shenton. 2010. “A diffusion tensor imaging study of the anterior limb of the internal capsule in schizophrenia.” Psychiatry Res, 184, 3, Pp. 143-50.Abstract
Frontal-subcortical cognitive and limbic feedback loops modulate higher cognitive functioning. The final step in these feedback loops is the thalamo-cortical projection through the anterior limb of the internal capsule (AL-IC). Using diffusion tensor imaging (DTI), we evaluated abnormalities in the AL-IC fiber tract in schizophrenia. Participants comprised 16 chronic schizophrenia patients and 19 male, normal controls, who were group matched for handedness, age, and parental socioeconomic status, and underwent DTI on a 1.5 Tesla GE system. We measured the diffusion indices, fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD), and manually segmented, based on FA maps, AL-IC volume, normalized for intracranial contents (ICC). The results showed a significant reduction in the ICC-corrected volume of the AL-IC in schizophrenia, but did not show diffusion measure group differences in the AL-IC in FA, MD, RD or AD. In addition, in the schizophrenia patients, AL-IC FA correlated positively with performance on measures of spatial and verbal declarative/episodic memory, and right AL-IC ICC-corrected volume correlated positively with more perseverative responses on the Wisconsin Card Sort Test (WCST). We found a reduction in AL-IC ICC-corrected volume in schizophrenia, without FA, MD, RD or AD group differences, implicating the presence of a structural abnormality in schizophrenia in this subcortical white matter region which contains important cognitive, and limbic feedback pathways that modulate prefrontal cortical function. Despite not demonstrating a group difference in FA, we found that AL-IC FA was a good predictor of spatial and verbal declarative/episodic memory performance in schizophrenia.
Padmavathi Sundaram, William M Wells III, Robert V Mulkern, Ellen J Bubrick, Edward B Bromfield, Mirjam Münch, and Darren B Orbach. 2010. “Fast human brain magnetic resonance responses associated with epileptiform spikes.” Magn Reson Med, 64, 6, Pp. 1728-38.Abstract

Neuronal currents produce local electromagnetic fields that can potentially modulate the phase of the magnetic resonance signal and thus provide a contrast mechanism tightly linked to neuronal activity. Previous work has demonstrated the feasibility of direct MRI of neuronal activity in phantoms and cell culture, but in vivo efforts have yielded inconclusive, conflicting results. The likelihood of detecting and validating such signals can be increased with (i) fast gradient-echo echo-planar imaging, with acquisition rates sufficient to resolve neuronal activity, (ii) subjects with epilepsy, who frequently experience stereotypical electromagnetic discharges between seizures, expressed as brief, localized, high-amplitude spikes (interictal discharges), and (iii) concurrent electroencephalography. This work demonstrates that both MR magnitude and phase show large-amplitude changes concurrent with electroencephalography spikes. We found a temporal derivative relationship between MR phase and scalp electroencephalography, suggesting that the MR phase changes may be tightly linked to local cerebral activity. We refer to this manner of MR acquisition, designed explicitly to track the electroencephalography, as encephalographic MRI (eMRI). Potential extension of this technique into a general purpose functional neuroimaging tool requires further study of the MR signal changes accompanying lower amplitude neuronal activity than those discussed here.

Riad Ababneh, Jing Yuan, and Bruno Madore. 2010. “Fat-water Separation in Dynamic Objects using an UNFOLD-like Temporal Processing.” J Magn Reson Imaging, 32, 4, Pp. 962-70.Abstract

PURPOSE: To separate fat and water signals in dynamic imaging. Because important features may be embedded in fat, and because fat may take part in disease processes, separating fat and water signals may be of great importance in a number of clinical applications. This work aims to achieve such separation at nearly no loss in temporal resolution compared to usual, nonseparated acquisitions. In contrast, the well-known 3-point Dixon method may cause as much as a 3-fold reduction in temporal resolution. MATERIALS AND METHODS: The proposed approach involves modulating the echo time TE from frame to frame, to force fat signals to behave in a conspicuous manner through time, so they can be readily identified and separated from water signals. The strategy is inspired from the "unaliasing by Fourier encoding the overlaps in the temporal direction" (UNFOLD) method, although UNFOLD involves changes in the sampling function rather than TE, and aims at suppressing aliased material rather than fat. RESULTS: The method was implemented at 1.5 T and 3 T, on cardiac cine and multiframe steady-state free precession sequences. In addition to phantom results, in vivo results from volunteers are presented. CONCLUSION: Good separation of fat and water signals was achieved in all cases.

Lauren J O'Donnell, Carl-Fredrik Westin, Isaiah Norton, Stephen Whalen, Laura Rigolo, Ruth Propper, and Alexandra J Golby. 2010. “The fiber laterality histogram: a new way to measure white matter asymmetry.” Med Image Comput Comput Assist Interv, 13, Pt 2, Pp. 225-32.Abstract
The quantification of brain asymmetries may provide biomarkers for presurgical localization of language function and can improve our understanding of neural structure-function relationships in health and disease. We propose a new method for studying the asymmetry of the white matter tracts in the entire brain, and we apply it to a preliminary study of normal subjects across the handedness spectrum. Methods for quantifying white matter asymmetry using diffusion MRI tractography have thus far been based on comparing numbers of fibers or volumes of a single fiber tract across hemispheres. We propose a generalization of such methods, where the "number of fibers" laterality measurement is extended to the entire brain using a soft fiber comparison metric. We summarize the distribution of fiber laterality indices over the whole brain in a histogram, and we measure properties of the distribution such as its skewness, median, and inter-quartile range. The whole-brain fiber laterality histogram can be measured in an exploratory fashion without hypothesizing asymmetries only in particular structures. We demonstrate an overall difference in white matter asymmetry in consistent- and inconsistent-handers: the skewness of the fiber laterality histogram is significantly different across handedness groups.
Peter Savadjiev, Yogesh Rathi, James G Malcolm, Martha E Shenton, and Carl-Fredrik Westin. 2010. “A geometry-based particle filtering approach to white matter tractography.” Med Image Comput Comput Assist Interv, 13, Pt 2, Pp. 233-40.Abstract
We introduce a fibre tractography framework based on a particle filter which estimates a local geometrical model of the underlying white matter tract, formulated as a 'streamline flow' using generalized helicoids. The method is not dependent on the diffusion model, and is applicable to diffusion tensor (DT) data as well as to high angular resolution reconstructions. The geometrical model allows for a robust inference of local tract geometry, which, in the context of the causal filter estimation, guides tractography through regions with partial volume effects. We validate the method on synthetic data and present results on two types in vivo data: diffusion tensors and a spherical harmonic reconstruction of the fibre orientation distribution function (fODF).
Z Kikinis, JH Fallon, M Niznikiewicz, P Nestor, C Davidson, L Bobrow, PE Pelavin, B. Fischl, A Yendiki, RW McCarley, R. Kikinis, M Kubicki, and ME Shenton. 2010. “Gray Matter Volume Reduction in Rostral Middle Frontal Gyrus in Patients with Chronic Schizophrenia.” Schizophr Res, 123, 2-3, Pp. 153-9.Abstract

The dorsolateral prefrontal cortex (DLPFC) is a brain region that has figured prominently in studies of schizophrenia and working memory, yet the exact neuroanatomical localization of this brain region remains to be defined. DLPFC primarily involves the superior frontal gyrus and middle frontal gyrus (MFG). The latter, however is not a single neuroanatomical entity but instead is comprised of rostral (anterior, middle, and posterior) and caudal regions. In this study we used structural MRI to develop a method for parcellating MFG into its component parts. We focused on this region of DLPFC because it includes BA46, a region involved in working memory. We evaluated volume differences in MFG in 20 patients with chronic schizophrenia and 20 healthy controls. Mid-rostral MFG (MR-MFG) was delineated within the rostral MFG using anterior and posterior neuroanatomical landmarks derived from cytoarchitectonic definitions of BA46. Gray matter volumes of MR-MFG were then compared between groups, and a significant reduction in gray matter volume was observed (p<0.008), but not in other areas of MFG (i.e., anterior or posterior rostral MFG, or caudal regions of MFG). Our results demonstrate that volumetric alterations in MFG gray matter are localized exclusively to MR-MFG. 3D reconstructions of the cortical surface made it possible to follow MFG into its anterior part, where other approaches have failed. This method of parcellation offers a more precise way of measuring MR-MFG that will likely be important in further documentation of DLPFC anomalies in schizophrenia.

Kunio Morishige, Daniel F Kacher, Peter Libby, Lee Josephson, Peter Ganz, Ralph Weissleder, and Masanori Aikawa. 2010. “High-Resolution Magnetic Resonance Imaging Enhanced with Superparamagnetic Nanoparticles Measures Macrophage Burden in Atherosclerosis.” Circulation, 122, 17, Pp. 1707-15.Abstract

BACKGROUND: Macrophages contribute to the progression and acute complications of atherosclerosis. Macrophage imaging may serve as a biomarker to identify subclinical inflamed lesions, to predict future risk, and to aid in the assessment of novel therapies. METHODS AND RESULTS: To test the hypothesis that nanoparticle-enhanced, high-resolution magnetic resonance imaging (MRI) can measure plaque macrophage accumulation, we used 3-T MRI with a macrophage-targeted superparamagnetic nanoparticle preparation (monocrystalline iron oxide nanoparticles-47 [MION-47]) in cholesterol-fed New Zealand White rabbits 6 months after balloon injury. In vivo MRI visualized thickened abdominal aortas on both T1- and T2-weighted spin-echo images (T1 spin echo, 20 axial slices per animal; T2 spin echo, 28 slices per animal). Seventy-two hours after MION-47 injection, aortas exhibited lower T2 signal intensity compared with before contrast imaging (signal intensity ratio, aortic wall/muscle: before, 1.44 ± 0.26 versus after, 0.95 ± 0.22; 164 slices; P<0.01), whereas T1 spin echo images showed no significant change. MRI on ex vivo specimens provided similar results. Histological studies colocalized iron accumulation with immunoreactive macrophages in atheromata. The magnitude of signal intensity reduction on T2 spin echo in vivo images further correlated with macrophage areas in situ (150 slices; r=0.73). Treatment with rosuvastatin for 3 months yielded diminished macrophage content (P<0.05) and reversed T2 signal intensity changes (P<0.005). Signal changes in rosuvastatin-treated rabbits correlated with reduced macrophage burden (r=0.73). In vitro validation studies showed concentration-dependent MION-47 uptake by human primary macrophages. CONCLUSION: The magnitude of T2 signal intensity reduction in high-resolution MRI after administration of superparamagnetic phagocytosable nanoparticles can assess macrophage burden in atheromata, providing a clinically translatable tool to identify inflamed plaques and to monitor therapy-mediated changes in plaque inflammation.

Nathalie YR Agar, James G Malcolm, Vandana Mohan, Hong W Yang, Mark D Johnson, Allen Tannenbaum, Jeffrey N Agar, and Peter M Black. 2010. “Imaging of meningioma progression by matrix-assisted laser desorption ionization time-of-flight mass spectrometry.” Anal Chem, 82, 7, Pp. 2621-5.Abstract
Often considered benign, meningiomas represent 32% of intracranial tumors with three grades of malignancy defined by the World Health Organization (WHO) histology based classification. Malignant meningiomas are associated with less than 2 years median survival. The inability to predict recurrence and progression of meningiomas induces significant anxiety for patients and limits physicians in implementing prophylactic treatment approaches. This report presents an analytical approach to tissue characterization based on matrix-assisted laser desorption ionization time-of-flight (MALDI TOF) mass spectrometry imaging (MSI) which is introduced in an attempt to develop a reference database for predictive classification of brain tumors. This pilot study was designed to evaluate the potential of such an approach and to begin to address limitations of the current methodology. Five recurrent and progressive meningiomas for which surgical specimens were available from the original and progressed grades were selected and tested against nonprogressive high-grade meningiomas, high-grade gliomas, and nontumor brain specimens. The common profiling approach of data acquisition was compared to imaging and revealed significant benefits in spatially resolved acquisition for improved spectral definition. A preliminary classifier based on the support vector machine showed the ability to distinguish meningioma image spectra from the nontumor brain and from gliomas, a different type of brain tumor, and to enable class imaging of surgical tissue. Although the development of classifiers was shown to be sensitive to data preparation parameters such as recalibration and peak picking criteria, it also suggested the potential for maturing into a predictive algorithm if provided with a larger series of well-defined cases.
Junichi Tokuda, Gregory S Fischer, Simon P Dimaio, David G Gobbi, Csaba Csoma, Philip W Mewes, Gabor Fichtinger, Clare M Tempany, and Nobuhiko Hata. 2010. “Integrated navigation and control software system for MRI-guided robotic prostate interventions.” Comput Med Imaging Graph, 34, 1, Pp. 3-8.Abstract
A software system to provide intuitive navigation for MRI-guided robotic transperineal prostate therapy is presented. In the system, the robot control unit, the MRI scanner, and the open-source navigation software are connected together via Ethernet to exchange commands, coordinates, and images using an open network communication protocol, OpenIGTLink. The system has six states called "workphases" that provide the necessary synchronization of all components during each stage of the clinical workflow, and the user interface guides the operator linearly through these workphases. On top of this framework, the software provides the following features for needle guidance: interactive target planning; 3D image visualization with current needle position; treatment monitoring through real-time MR images of needle trajectories in the prostate. These features are supported by calibration of robot and image coordinates by fiducial-based registration. Performance tests show that the registration error of the system was 2.6mm within the prostate volume. Registered real-time 2D images were displayed 1.97 s after the image location is specified.
Peter Savadjiev, Gordon L Kindlmann, Sylvain Bouix, Martha E Shenton, and Carl-Fredrik Westin. 2010. “Local white matter geometry from diffusion tensor gradients.” Neuroimage, 49, 4, Pp. 3175-86.Abstract
We introduce a mathematical framework for computing geometrical properties of white matter fibers directly from diffusion tensor fields. The key idea is to isolate the portion of the gradient of the tensor field corresponding to local variation in tensor orientation, and to project it onto a coordinate frame of tensor eigenvectors. The resulting eigenframe-centered representation then makes it possible to define scalar indices (or measures) that describe the local white matter geometry directly from the diffusion tensor field and its gradient, without requiring prior tractography. We derive new scalar indices of (1) fiber dispersion and (2) fiber curving, and we demonstrate them on synthetic and in vivo data. Finally, we illustrate their applicability to a group study on schizophrenia.
Giorgio Bonmassar, Sunao Iwaki, Gregory Goldmakher, Leonardo M Angelone, John W Belliveau, and Michael H Lev. 2010. “On the Measurement of Electrical Impedance Spectroscopy (EIS) of the Human Head.” Int J Bioelectromagn, 12, 1, Pp. 32-46.Abstract
We are introducing a system for Electrical Impedance Spectroscopy (EIS) measurements for future use in Neurological Intensive Care Unit (NICU) settings. The system consists mostly of commercially available components and the software was developed in Labview (National Instruments). The system is based on the principle that acute hemorrhagic stroke may produce detectable changes in the impedance spectrum measured on the subject's scalp due to parenchimal local increases of blood volume. EIS measurements were performed on four healthy control subjects to establish a baseline for a real time stroke detector. Measurements were performed using white noise currents in the 0-50 kHz frequency band using ten shielded electrodes placed on a subject's scalp, with electrical potentials measured with a large-dynamic range for increased EIS accuracy. EIS measurements yielded highly symmetrical impedance spectra, which was only obtainable using the proposed continuos spectral electrical impedance estimation.
Jong Woo Lee, Patrick Y Wen, Shelley Hurwitz, Peter M Black, Santosh Kesari, Jan Drappatz, Alexandra J Golby, William M Wells III, Simon K Warfield, Ron Kikinis, and Edward B Bromfield. 2010. “Morphological characteristics of brain tumors causing seizures.” Arch Neurol, 67, 3, Pp. 336-42.Abstract

OBJECTIVE: To quantify size and localization differences between tumors presenting with seizures vs nonseizure neurological symptoms. DESIGN: Retrospective imaging survey. We performed magnetic resonance imaging-based morphometric analysis and nonparametric mapping in patients with brain tumors. SETTING: University-affiliated teaching hospital. PATIENTS OR OTHER PARTICIPANTS: One hundred twenty-four patients with newly diagnosed supratentorial glial tumors. MAIN OUTCOME MEASURES: Volumetric and mapping methods were used to evaluate differences in size and location of the tumors in patients who presented with seizures as compared with patients who presented with other symptoms. RESULTS: In high-grade gliomas, tumors presenting with seizures were smaller than tumors presenting with other neurological symptoms, whereas in low-grade gliomas, tumors presenting with seizures were larger. Tumor location maps revealed that in high-grade gliomas, deep-seated tumors in the pericallosal regions were more likely to present with nonseizure neurological symptoms. In low-grade gliomas, tumors of the temporal lobe as well as the insular region were more likely to present with seizures. CONCLUSIONS: The influence of size and location of the tumors on their propensity to cause seizures varies with the grade of the tumor. In high-grade gliomas, rapidly growing tumors, particularly those situated in deeper structures, present with non-seizure-related symptoms. In low-grade gliomas, lesions in the temporal lobe or the insula grow large without other symptoms and eventually cause seizures. Quantitative image analysis allows for the mapping of regions in each group that are more or less susceptible to seizures.