Biomedical subjects

Meiyappan Solaiyappan

Publications and source records attributed to Meiyappan Solaiyappan.

12 recordsLinked to original sources

PubMed2005

Dynamic imaging of allogeneic mesenchymal stem cells trafficking to myocardial infarction.

BACKGROUND: Recent results from animal studies suggest that stem cells may be able to home to sites of myocardial injury to assist in tissue regeneration. However, the histological interpretation of postmortem tissue, on which many of these studies are based, has recently been widely debated. METHODS AND RESULTS: With the use of the high sensitivity of a combined single-photon emission CT (SPECT)/CT scanner, the in vivo trafficking of allogeneic mesenchymal stem cells (MSCs) colabeled with a radiotracer and MR contrast agent to acute myocardial infarction was dynamically determined. Redistribution of the labeled MSCs after intravenous injection from initial localization in the lungs to nontarget organs such as the liver, kidney, and spleen was observed within 24 to 48 hours after injection. Focal and diffuse uptake of MSCs in the infarcted myocardium was already visible in SPECT/CT images in the first 24 hours after injection and persisted until 7 days after injection and was validated by tissue counts of radioactivity. In contrast, MRI was unable to demonstrate targeted cardiac localization of MSCs in part because of the lower sensitivity of MRI. CONCLUSIONS: Noninvasive radionuclide imaging is well suited to dynamically track the biodistribution and trafficking of mesenchymal stem cells to both target and nontarget organs.

Animals↗

PubMed2004

3-dimensional magnetic resonance imaging modeling of the pelvic floor musculature in classic bladder exstrophy before pelvic osteotomy.

PURPOSE: We provide a 3-dimensional (3D) model of the pelvic floor musculature in patients with classic bladder exstrophy using magnetic resonance imaging (MRI). MATERIALS AND METHODS: Five male infants 1 day to 12 months old underwent MRI of the pelvis, which was compared to pelvic MRI of 1 male infant without pelvic floor abnormalities. Of the patients 3 were studied before primary closure and 2 before reclosure. None of the patients had a prior pelvic osteotomy. While the entire pelvic floor was imaged, special attention was paid to the contours of the levator ani muscle group which were drawn on T1-weighted axial and coronal images. The overlap of contours in these 2 planes was used to construct a 3D model of this muscle group. The diastasis of the pubic symphysis was also measured for all patients on a plain pelvic radiograph. RESULTS: The levator ani muscle group conformed to an elliptical dome shape in the control. For the patients the 3D shape was somewhat irregular with an apparent kink in the ellipse. The elliptical shape of the group was described by a shape factor, s, which equals the ratio of the maximum height-to-the length of the base of the ellipse. The shape factor was equal to 0.176 in the control compared to a mean of 0.448 for the patients. There was no relationship between diastasis of the pubic symphysis and the extent of disproportionate curvature of the levator group. CONCLUSIONS: To our knowledge this is the first qualitative description of the pelvic floor anatomy in bladder exstrophy using MRI. Our model gives further insights into the true pelvic floor anatomy in exstrophy cases and is the first to suggest that abnormalities in the pelvic floor may not correlate with abnormalities of the bony pelvis.

Bladder Exstrophy↗

PubMed2003

Fast method for correcting image misregistration due to organ motion in time-series MRI data.

Time-series MRI data often suffers from image misalignment due to patient movement and respiratory and other physiologic motion during the acquisition process. It is necessary that this misalignment be corrected prior to any automated quantitative analysis. In this article a fast and automated technique for removing in-plane misalignment from time-series MRI data is presented. The method is computationally efficient, robust, and fine-tuned for the clinical setting. The method was implemented and tested on data from 21 human subjects, including myocardial perfusion imaging, renal perfusion imaging, and blood-oxygen level-dependent cardiac T(2*) imaging. In these applications 10-fold or better reduction in image misalignment is reported. The improvement after registration on representative time-intensity curves is shown. Although the method currently corrects translation motion using image center of mass, the mathematical framework of our approach may be extended to correct rotation and other higher-order displacements.

Algorithms↗

PubMed2003

Dipole source analysis of laser-evoked subdural potentials recorded from parasylvian cortex in humans.

The location of the human nociceptive area(s) near the Sylvian fissure is still controversial in spite of evidence from imaging and evoked potential studies that noxious heat stimuli activate somatosensory areas in that region. Some studies have suggested the secondary somatosensory cortex (SII) on the upper bank of the Sylvian fissure posterior to the central sulcus, others the anterior insula or parietal area 7b. In this study, we applied dipole source analysis techniques to laser-evoked potentials (LEPs) that were recorded from subdural grid electrodes in three patients. As a functional marker, auditory-evoked potentials (AEPs) with a generator on the opposite bank of the Sylvian fissure were recorded from the same electrodes. The LEP global field power (GFP), a measure of spatial variance, showed a first peak at about 150 ms latency, corresponding to the latency of the N1 recorded from the scalp. In contrast to scalp recordings, the amplitude of the first GFP peak recorded from the grid was larger than the second peak (P2). This finding suggests that the generator of N1, but not that of later LEP components, was close to the subdural grids. When a regional source was fitted to the first GFP peak, its location was within the frontoparietal operculum in all patients. On average, the LEP source was 13 mm anterior, 6 mm superior, and 2 mm medial of the AEP source. This relative location also suggests a source within the frontoparietal operculum overlying the insula. At the latency of the first GFP peak, source orientation pointed inward, suggesting a generator within the inner vertical surface of the operculum. Somatotopy was assessed in one patient and was consistent with that of the projection area of the presumed nociceptive thalamic nucleus posterior part of the ventromedial nucleus, but differed from that of SII. These findings suggest that the nociceptive area in human parasylvian cortex that is activated most rapidly by noxious heat pulses may be separate from the tactile SII area.

Adult↗

PubMed2003

Reduction of vascular and permeable regions in solid tumors detected by macromolecular contrast magnetic resonance imaging after treatment with antiangiogenic agent TNP-470.

PURPOSE: The availability of noninvasive techniques to detect the effects of antiangiogenic agents is critically important for optimizing treatment of cancer with these agents. Magnetic resonance imaging (MRI) is one such noninvasive technique that is routinely used clinically. EXPERIMENTAL DESIGN: In this study, we have evaluated the use of MRI of the intravascular contrast agent albumin-GdDTPA to detect the effects of the antiangiogenic agent TNP-470 on the vascular volume and permeability of the MatLyLu prostate cancer model. RESULTS: TNP-470-treated tumors demonstrated a significant decrease of vascular volume, as well as a significant reduction in vascular and permeable regions, compared with volume-matched control tumors. Although the fractional volume of permeable regions in the tumor decreased, the average value of tumor permeability did not decrease significantly. This was attributable to increase in permeability in some regions of the tumor. These regions were mostly associated with low vascular volume. ELISA assays of control and treated MatLyLu tumors also detected a significant increase of vascular endothelial growth factor in the TNP-470-treated tumors. CONCLUSION: MRI detected significant changes in tumor vascular characteristics after treatment with TNP-470.

Angiogenesis Inhibitors↗

PubMed2002

Brain white matter anatomy of tumor patients evaluated with diffusion tensor imaging.

We applied multislice, whole-brain diffusion tensor imaging (DTI) to two patients with anaplastic astrocytoma. Data were analyzed using DTI-based, color-coded images and a 3-D tract reconstruction technique for the study of altered white matter anatomy. Each tumor was near two major white matter tracts, namely, the superior longitudinal fasciculus and the corona radiata. Those tracts were identified using the color-coded maps, and spatial relationships with the tumors were characterized. In one patient the tumor displaced adjacent white matter tracts, whereas in the other it infiltrated the superior longitudinal fasciclus without displacement of white matter. DTI provides new information regarding the detailed relationship between tumor growth and nearby white matter tracts, which may be useful for preoperative planning.

Adult↗

PubMed2002

MRI detection of myocardial perfusion defects due to coronary artery stenosis with MS-325.

PURPOSE: To assess the value of an intravascular, albumin-targeted contrast agent, MS-325, in visualizing myocardial ischemia with magnetic resonance imaging (MRI). MATERIALS AND METHODS: Left anterior descending coronary artery (LAD) stenosis was created in 19 pigs using a closed-chest modified angioplasty technique. Myocardial ischemia was detected by first-pass, contrast-enhanced MRI at peak dipyridamole stress and was compared to Technetium-99m (Tc-99m) sestamibi single photon emission computed tomography (SPECT). Regional coronary blood flow was determined using microspheres. RESULTS: Inducible myocardial ischemia with >40% reduction in stress myocardial blood flow was created in eight animals. An MRI defect, classified as > or=75% reduction in peak myocardial signal intensity in the affected territory, was detected in 92.3% of these animals. In the presence of mild coronary stenosis, there was uniform enhancement with MRI and tracer uptake by SPECT. Concordance of MRI and SPECT for detecting perfusion defects was 85%. CONCLUSION: The pattern of prolonged and persistent MR hypoenhancement of the ischemic myocardial bed using MS-325, which is retained primarily in the vascular bed due to its albumin-binding properties, facilitates the detection of myocardial perfusion defects.

Animals↗

PubMed2002

Imaging cortical association tracts in the human brain using diffusion-tensor-based axonal tracking.

Diffusion-tensor fiber tracking was used to identify the cores of several long-association fibers, including the anterior (ATR) and posterior (PTR) thalamic radiations, and the uncinate (UNC), superior longitudinal (SLF), inferior longitudinal (ILF), and inferior fronto-occipital (IFO) fasciculi. Tracking results were compared to existing anatomical knowledge, and showed good qualitative agreement. Guidelines were developed to reproducibly track these fibers in vivo. The interindividual variability of these reconstructions was assessed in a common spatial reference frame (Talairach space) using probabilistic mapping. As a first illustration of this technical capability, a reduction in brain connectivity in a patient with a childhood neurodegenerative disease (X-linked adrenoleukodystrophy) was demonstrated.

Adrenoleukodystrophy↗

PubMed2002

A framework for callosal fiber distribution analysis.

This paper presents a framework for analyzing the spatial distribution of neural fibers in the brain, with emphasis on interhemispheric fiber bundles crossing through the corpus callosum. The proposed approach combines methodologies for fiber tracking and spatial normalization and is applied on diffusion tensor images and standard magnetic resonance images.

Adult↗

PubMedDate not supplied

Extracellular acidification alters lysosomal trafficking in human breast cancer cells.

Cancer cells invade by secreting degradative enzymes, which are sequestered in lysosomal vesicles. In this study, the impact of an acidic extracellular environment on lysosome size, number, and distance from the nucleus in human mammary epithelial cells (HMECs) and breast cancer cells of different degrees of malignancy was characterized because the physiological microenvironment of tumors is frequently characterized by extracellular acidity. An acidic extracellular pH (pH(e)) resulted in a distinct shift of lysosomes from the perinuclear region to the cell periphery irrespective of the HMECs' degree of malignancy. With decreasing pH, larger lysosomal vesicles were observed more frequently in highly metastatic breast cancer cells, whereas smaller lysosomes were observed in poorly metastatic breast cancer cells and HMECs. The number of lysosomes decreased with acidic pH values. The displacement of lysosomes to the cell periphery driven by extracellular acidosis may facilitate exocytosis of these lysosomes and increase secretion of degradative enzymes. Filopodia formations, which were observed more frequently in highly metastatic breast cancer cells maintained at acidic pH(e), may also contribute to invasion.

Antigens, CD↗

PubMedDate not supplied

Quantitative differentiation of breast lesions based on three-dimensional morphology from magnetic resonance imaging.

OBJECTIVE: The purpose of this study was to develop geometric indices, based on morphologic measurements, of contrast-enhanced breast lesions using three-dimensional magnetic resonance imaging (MRI) that can statistically differentiate between benign and malignant lesions. METHODS: Thirty-three patients with abnormal mammograms were scanned using three-dimensional MRI. The lesion was then extracted from the volume data set using interactive volume-rendering software. From the extracted region of interest, the surface boundary corresponding to the lesion was extracted using an isosurface method. The boundary was represented as a triangular mesh, from which the surface area and volume enclosed by the surface were computed. The following variables were tested for discrimination ability between benign and malignant lesions: 1) the volume-to-surface area (V/S) ratio, 2) spherical shape index (SSI), and 3) resolution reduction for V/S and SSI values (100%, 16%, 8%, 4%, 2%, and 1% resolution). In addition, comparisons were made between the V/S and SSI values at 100% versus their reduced resolutions. RESULTS: Thirty-three subjects (15 malignant tumors and 18 benign tumors) were studied. The SSI index (P = 0.0063) was a significant discriminator for malignancy. The V/S ratio (P = 0.9280) did not seem to be a useful variable in distinguishing benign and malignant masses. The V/S resolution comparisons (P > 0.5897) and the SSI resolution comparisons (P > 0.05) were also not useful discriminating variables. CONCLUSION: The SSI seems to be a useful factor in differentiating between benign and malignant lesions. Current clinical interpretation of breast lesions using MRI may be enhanced by the adjunctive use of this objective postanalysis method.

Adolescent↗

PubMedDate not supplied

Right ventricle shape and contraction patterns and relation to magnetic resonance imaging findings.

OBJECTIVE: To analyze and to describe the shape and contraction of the normal right ventricle (RV) as visualized by magnetic resonance imaging (MRI). METHODS: Thirty normal volunteers were imaged using cine MRI in axial, short-axis, and long-axis planes. The shape and contraction of the RV were qualitatively evaluated. Quantitative evaluation of RV shape was performed by calculating the angle subtended between the planes of horizontal long-axis view (HLA) and axial view and the RV base-to-apex distance. Multiplanar reformation was used to visualize changes between corresponding views. RESULTS: The spectrum of major RV shape (wedge, box, and round) was more variable on axial images (17%, 43%, and 23%, respectively) than on HLA images (63%, 20%, and 0%, respectively). Focal outpouching of the RV free wall was more frequent on the axial view than on the HLA view. The subtended plane angle and base-to-apex distance showed statistically significant dependence indicative of an artificially foreshortened RV in the axial view with a direct influence on RV variations. CONCLUSIONS: With increasing subtended angles, variation of the normal RV appearance is substantially higher on axial views compared with HLA views.

Adult↗