Biomedical subjects

S L Talagala

Publications and source records attributed to S L Talagala.

9 recordsLinked to original sources

PubMed1998

Functional MRI using steady-state arterial water labeling.

Flow-sensitive functional MRI (fMRI) was performed using steady-state arterial water labeling (SS-AWL). Arterial water labeling was accomplished by flow induced adiabatic fast passage. The signal intensity of the visual cortex in arterial water labeled images decreased by approximately 1.4% during visual stimulation of the brain. Acquisition of arterial water unlabeled and labeled images allows measurement of relative cerebral blood flow increase during brain activation. During visual stimulation, cerebral blood flow in the visual cortex increased by 17 to 35% as measured by SS-AWL. Quantitation of brain activation in terms of a physiological parameter using SS-AWL will facilitate comparative fMRI studies under different conditions.

Adult↗

PubMed1997

Phosphorus-31 magnetic resonance brain spectroscopy of children at risk for a substance use disorder: preliminary results.

The purpose of this exploratory investigation was to evaluate the heuristic potential of 31P magnetic resonance spectroscopy (MRS) in elucidating a neurobiologic component of the liability for a substance use disorder (SUD). We investigated 31P MRS spectra employing chemical shift imaging (CSI) derived from four distinct anatomic brain locations (i.e. frontal, occipital, right parietal, left parietal) in three groups of peripubertal children who are hypothesized to be at increasing levels of familial SUD risk. Specifically, we studied children with a positive paternal family history of SUD and a disruptive behavior disorder (DBD) diagnosis (SUD+/DBD+; n = 10), in contrast, to those with a positive paternal SUD history in the absence of other psychopathology (SUD+/DBD-; n = 13) and matched control children from normal families (SUD-/DBD-; n = 13). In addition, we examined neurocognitive tests of our subjects to determine any associations between cognitive capacities with regional 31P MRS spectra. The highest-risk sample (SUD+/DBD+) demonstrated a diminished proportion of phosphodiesters confined to the right parietal voxel. This right parietal phosphodiester proportion correlated only with the Information Scale score on a standard intelligence test for children. This suggested a relationship between general learning ability and motivation for academic achievement and right parietal physiology in the highest-risk sample. Variations in synaptic pruning could account for this observation.

Adolescent↗

PubMed1995

Evaluation of the renal arteries in kidney donors: value of three-dimensional phase-contrast MR angiography with maximum-intensity-projection or surface rendering.

OBJECTIVE: Donors routinely undergo preoperative conventional arteriography to evaluate the renal arteries before nephrectomy. The purpose of this study was to assess the capability of three-dimensional phase-contrast MR angiograms postprocessed with maximum-intensity-projection and surface-rendering techniques to show the renal arteries of potential donors. MATERIALS AND METHODS: Postprocessed three-dimensional phase-contrast MR angiograms of 17 patients were retrospectively reviewed by two experienced radiologists for the number and length of renal arteries visualized. Conventional arteriograms were used as the reference standard. Coronal maximum-intensity-projection and surface-rendered MR angiograms were also compared with each other with regard to the delineation of renal arteries from overlapping vessels. RESULTS: MR angiograms showed all 34 single or dominant renal arteries but only eight of 10 accessory arteries seen on conventional arteriograms. One of the nonvisualized accessory arteries was located within the imaged volume, and the other one arose from the distal aorta beyond the imaged regions. Five of six arterial branches arising from the proximal 30-mm portions of the renal arteries were seen on MR angiograms. Postprocessing with either maximum-intensity projection or surface-rendering showed the same number of renal arteries, although surface rendering separated overlapping veins from the renal arteries better than the maximum-intensity-projection technique. CONCLUSION: These results suggest that three-dimensional MR angiography is a reliable method of imaging single or dominant renal arteries, but not for showing all accessory renal arteries and small arterial branches. Surface rendering may provide specific advantages over maximum-intensity-projection in delineating renal arteries from overlapping vessels.

Adult↗

PubMed1993

Blood flow in the portal vein: velocity quantitation with phase-contrast MR angiography.

Quantitative phase-contrast magnetic resonance (MR) angiography of the portal vein was prospectively evaluated in 79 fasting patients and 23 healthy volunteers. Images were obtained during a 12-second breath-hold acquisition in the coronal (n = 102) and axial (n = 11) planes. Pathologic correlation was available in 55 of 79 patients and included findings of cholangiocarcinoma, cirrhosis, hepatocellular carcinoma, hepatitis, and metastatic disease. Forty-one patients had correlative Doppler ultrasound (US) findings. MR and US findings correlated as to flow direction in all cases. In nine patients, Doppler US velocity measurements were available and closely correlated with MR findings. A comparison of axial and coronal portal venous phase-contrast measurements in 11 patients revealed no substantial difference with regard to the plane used. Quantitative phase-contrast MR angiography is a simple and rapid technique for the assessment of portal venous patency, flow direction, and flow velocity and, combined with high-resolution conventional MR imaging, may obviate the current use of both computed tomographic and US examinations.

Blood Flow Velocity↗

PubMed1992

MR angiography of the head and neck: value of two-dimensional phase-contrast projection technique.

MR angiography is commonly performed by using two- and three-dimensional time-of-flight and three-dimensional phase-contrast techniques. These procedures require long examination times and processing of imaging data by computing maximum intensity projections. Two-dimensional phase-contrast projection angiography has neither of these disadvantages. We analyzed the value of this technique for head and neck MR angiography in 84 patients and 15 control subjects. Patients were examined to resolve specific clinical questions such as the presence of arteriovenous malformations (20 cases), patency of carotid and vertebral arteries (35 cases), patency of the superior sagittal sinus (14 cases), patency of saphenous vein bypass grafts (11 cases), and vascularity of masses (four cases). Conventional angiograms were available for correlation in 22 patients. Two-dimensional phase-contrast projection angiograms were generated by using a gradient-recalled-echo sequence sensitized to flow with the use of flow-encoding gradients. Projection MR angiograms were obtained in approximately 3.5 min by combining images obtained with flow-encoding gradients applied along the axes defining the image plane. MR angiograms were subjectively evaluated by three observers without reference to routine MR images or conventional angiograms. High-quality studies were obtained in 93% of control subjects and 90% of patients examined. The findings based on phase-contrast angiography were confirmed with conventional angiography in 21 of 22 patients for whom conventional angiograms were available. Evaluation of vascular grafts and of the patency of major cranial vessels was easily done with two-dimensional phase-contrast angiography and was useful in postoperative follow-up examinations. We also advocate its use for superior sagittal sinus thrombosis and follow-up examinations in patients with arteriovenous malformations.

Arteriovenous Malformations↗

PubMedDate not supplied

Effects of MR exposure at 1.5 T on early embryonic development of the chick.

The potential teratogenicity of magnetic resonance (MR) field exposure on the early development of the chick embryo was examined. Eggs at four developmental stages within the first 42 hours of incubation were exposed to a static magnetic field of 1.5 T for 6 hours and to 64-MHz radio-frequency field pulses and a switched magnetic field gradient with an amplitude of 0.6 G/cm for 4 h. When the embryos were sacrificed shortly thereafter (at approximately 53 hours of incubation), the abnormality and mortality rates of exposed and unexposed (control) embryos in each of the developmental groups did not show a consistent pattern. When embryos were sacrificed on the 6th day of incubation, exposed embryos from all developmental groups showed a trend toward higher abnormality and mortality rates than their controls. More extensive studies are needed to confirm these findings.

Abnormalities, Radiation-Induced↗

PubMedDate not supplied

Effects of MR exposure on cell proliferation and migration of chick motoneurons.

The effect of magnetic resonance (MR) exposure on the proliferation and migration of motoneurons was examined in chick embryos. Embryos were exposed in ovo to a static magnetic field of 1.5 T for 6 hours and to 64-MHz radio-frequency field pulses and a switched magnetic field gradient with an amplitude of 0.6 G/cm for 4 hours. For cell proliferation studies, embryos were exposed to MR fields during the developmental stage at which motoneuron proliferation is most active. For cell migration studies, embryos were exposed to MR fields at the developmental stage just before lateral motoneuron migration. The results show that the birth dates, migration, and proliferation of lateral motoneurons were unaffected by the MR exposure conditions in this study.

Abnormalities, Radiation-Induced↗

PubMedDate not supplied

Fast three-dimensional time-of-flight MR angiography of the intra-cranial vasculature.

Magnetic resonance angiography is most commonly performed with the three-dimensional (3D) time-of-flight (TOF) technique. As currently practiced, this requires long image acquisition times (5-10 minutes). The authors show that the acquisition time of 3D TOF images can be reduced to less than 1 minute by using a very short TR (< 10 msec). Under normal flow conditions, the major vessels of the circle of Willis were consistently well demonstrated on these fast 3D TOF images. Signal saturation was observed in studies of patients with abnormal blood flow. In those cases, it was demonstrated that serial acquisition of fast 3D TOF data during and after contrast agent administration could be used to overcome the saturation effects. Time-resolved fast 3D TOF imaging during and after contrast agent administration can also provide qualitative assessment of flow and may depict other features that cannot be observed in TOF studies with long imaging times.

Adult↗

PubMedDate not supplied

In vivo detection of cortical plaques by MR imaging in patients with multiple sclerosis.

BACKGROUND AND PURPOSE: In vivo detection of cortical lesions in patients with multiple sclerosis (MS) by MR imaging is hampered by several factors. Among them is the low contrast between small cortical lesions and surrounding cortical gray matter offered by present techniques. METHODS: T1-weighted 3D spoiled gradient-recalled-echo (SPGR) volumes and 2D fluid-attenuated inversion recovery (FLAIR) sequences of 22 patients with MS who had 12 monthly brain MR imaging examinations at 1.5T, using a quadrature head coil, were retrospectively analyzed. These serial studies were coregistered and averaged to generate a single high signal-to-noise ratio (SNR) mean image, which was used to identify cortical lesions. The means of 12 FLAIRs and SPGRs from 14 age- and sex-matched healthy volunteers were analyzed as well. RESULTS: No cortical lesions were found on images of healthy subjects. Eighty-six cortical lesions were identified in 13 (59.1%) patients, predominantly in the frontal lobe (73.3%); 23.3% of cortical lesions lay entirely in the cortex, whereas the remaining lesions invaded the white matter underneath. CONCLUSION: Averaging multiple SPGRs created a single high SNR volume, allowing identification of cortical lesions. Because data were obtained monthly for 1 year, the average image does not account for transient lesion activity. However, for cortical lesions that remained stable during this time, the findings are valid in demonstrating the importance of high SNR images for detecting cortical brain abnormalities in MS.

Adult↗