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Biomedical subjects

A Kalnin

Publications and source records attributed to A Kalnin.

6 recordsLinked to original sources
PubMed2000

Positioning of vagal nerve stimulators: technical note.

BACKGROUND: Vagal nerve stimulation has become an important treatment for patients with intractable seizure disorders. Many of these patients will require magnetic resonance imaging (MRIs) of the brain after the stimulator has been implanted to monitor underlying neurologic conditions. Functional MRI (fMRI) is also being used in the evaluation of epilepsy. With the current recommended implant techniques the magnetic field of the MRI will deactivate the pulse generator while the patient is in the supine position for the scan. A simple change in positioning of the pulse generator will help to avoid deactivating the device during an MRI. This will avoid exposing the patient to lengthy time periods with a deactivated stimulator and also allow for the performance of fMRIs and any other MRI scans needed to monitor underlying neurologic conditions. METHODS: A working model of the NeuroCybernetic Prosthesis (NCP) pulse generator was assessed with an oscilloscope and LED light connected to it that related activation of the generator while in the MRI. This simulation was performed with the device alone, in multiple positions. Then patients with implanted devices who could personally confirm the activation of their stimulators were also studied. RESULTS: A pulse generator placed with the electrode inputs parallel to the long axis of the body was not deactivated by the magnetic field of the MRI when the patient was in the supine position. CONCLUSION: Changing the implant position of a vagal nerve stimulator pulse generator will help to prevent deactivation of the device while in the MRI, allowing for the performance of fMRIs while not exposing the patient to lengthy time periods with a deactivated vagal nerve stimulator.

Electric Stimulation Therapy↗
PubMed1999

Cortical representation of swallowing in normal adults: functional implications.

OBJECTIVE: Dysphagia of neurogenic or postsurgical origin presents management and therapeutic challenges to the otolaryngologist. Improvements in management and therapeutic approaches may be facilitated by understanding how the central nervous system controls swallowing. The purpose of this investigation was to utilize functional magnetic resonance imaging to determine patterns of cortical activity during swallowing in normal, healthy adult subjects. STUDY DESIGN: Functional magnetic resonance imaging (fMRI) was performed on eight healthy adult subjects using conventional BOLD (blood oxygenation level dependent) techniques. METHODS: Subjects performed three different swallowing tasks including dry and bolus swallows, and performed a control finger movement task. Statistical maps of cortical activation were generated using a cross-correlation analysis. One-way and two-way ANOVA statistical analyses were performed to compare activated areas among the different tasks and to determine the effects of task sequence. RESULTS: Activation during the three swallowing tasks occurred in the primary motor cortex, primary somatosensory cortex, and other cortical and subcortical sites. Cortical representation of swallowing and finger movement followed somatotopic maps. Differential distribution of cortical activation was observed for the different swallowing tasks. CONCLUSIONS: Activation of the primary motor and somatosensory cortices, as well as other sensory-motor areas, occurs with swallowing in normal adults. Differential distribution of cortical activity with different swallowing tasks suggests differential functional organization for different swallowing tasks. Understanding these mechanisms may facilitate improved management and therapeutic intervention for neurogenic and postsurgical dysphagia.

Adult↗
PubMed1999

Functional magnetic resonance imaging and radiosurgical dose planning.

OBJECTIVE: To assess the effect of functional magnetic resonance imaging (fMRI) on stereotactic radiosurgical (SRS) dose planning. METHODS: Patients included those undergoing SRS whose lesions were in or near areas that could be identified with fMRI. After processing, an fMR scan was registered to the anatomic scan, and this dataset was registered to a stereotactic CT scan. The imaged functional areas were contoured along with standard anatomical targets. Dose planning was done at first with the functional volumes rendered invisible; the plans were then adjusted as needed using the functional targets. Doses were measured using a dose-volume histogram tool. RESULTS: SRS was performed in 12 patients, 1 of whom also underwent SRT. Functional volumes studied included motor cortex in 8 patients, visual in 6 and language in 3; a total of 33 functional targets were imaged. Prescription doses ranged from 12 to 22.5 Gy (mean 19.5 Gy), and the maximum dose to functional volumes from 8 cGy to 18.5 Gy (mean 2.9 Gy). In 6 patients, arc adjustment using functional targets yielded a >50% reduction in dose to at least one functional volume; in all patients, the dose reduction to 50 and 75% of functional volumes averaged 4% (12 cGy) and 13% (30 cGy), respectively, while the reduction of maximal dose averaged 24% (50 cGy). CONCLUSIONS: fMRI can be used in SRS to reduce irradiation of eloquent brain using standard prescription doses. Appropriate arc adjustment may allow for escalation of the dose to the targeted lesion.

Adult↗
PubMedDate not supplied

Intraoperative functional MRI using a real-time neurosurgical navigation system.

A 42-year-old-man had focal left hand motor seizures. MR studies demonstrated a right posterior frontal brain tumor. Functional MRI was performed, localizing the motor cortex posterior to the lesion. The functional images were integrated with a neurosurgical navigation computer. A real-time intraoperative display of the anatomic and functional images was produced, registered to a neurosurgical probe. Excellent correlation was demonstrated between the functional maps and invasive electrophysiologic mapping performed at the time of craniotomy.

Adult↗
PubMedDate not supplied

Leukoencephalopathy in normal and pathologic aging: 2. MRI of brain lucencies.

A pilot study was performed to test the ability of MR to evaluate the brain lucencies shown by CT in Alzheimer disease patients and in normal control subjects. Eight patients with presumed Alzheimer disease and 47 normal controls, 12 over the age of 45 years and 35 under age 45, were studied. Each group included subjects with and without CT evidence of leukoencephalopathy. Inversion recovery, saturation recovery, and spin-echo scans were obtained using a 0.3-T permanent magnet prototype unit. Results indicated that MR was more sensitive than CT to parenchymal disease. Seven of the eight patients with Alzheimer disease showed patches of increased signal intensity on SE scans; only three had lucencies on their CT studies. None of the normal subjects under the age of 45 showed periventricular patches of increased SE signal intensity. T2-weighted SE imaging was performed in nine of the 12 normal subjects over 45 years old. Eight of the nine demonstrated periventricular patches of increased SE signal intensity. Faint CT lucencies were present in only one of these. The configuration of the patches of increased signal intensity was similar for both the normal and Alzheimer groups, but the extent of white-matter involvement was greater in the Alzheimer group.

Aged↗