PubMed Health⌕ Search

Biomedical subjects

C L Truwit

Publications and source records attributed to C L Truwit.

At least 19 recordsLinked to original sources
PubMed2002

Diffusion-weighted MR imaging findings in carbon monoxide poisoning.

Diffusion-weighted MR imaging (DWI) of two patients with carbon monoxide (CO) poisoning demonstrated white matter and cortical hyperintensities. In one patient, the changes on the FLAIR sequence were more subtle than those on DWI. The DWI abnormality in this patient represented true restriction. In the second patient, repeated exposure to CO caused restricted diffusion. DWI may be helpful for earlier identification of the changes of acute CO poisoning.

Acute Disease↗
PubMed2001

Improving diagnostic yield in brain biopsy: coupling spectroscopic targeting with real-time needle placement.

The purpose of this study was to determine the utility of intraoperative magnetic resonance spectroscopy (MRS) for targeting during brain biopsy using a skull-mounted trajectory guide. From January 1999 to January 2001, 17 patients had intraoperative MRS-guided brain biopsy using a trajectory guide. Ten had turbo spectroscopic imaging (TSI), and seven had both SVS (single-voxel spectroscopy) and TSI. Prospective stereotaxy was used to align the device in a short-bore 1.5-T MR scanner. Areas of elevated choline relative to creatine on SVS and TSI were targeted during the biopsy. Intraoperative imaging confirmed appropriate positioning of the biopsy needle at the time of tissue sampling in all cases. All 17 biopsies (100%) yielded diagnostic tissue. Six patients (34%) had glioblastomas multiforme, three (18%) had anaplastic astrocytomas, three (18%) had anaplastic oligodendrogliomas, two (12%) had radiation necrosis, and one each (6%) had germinoma, ganglioglioma, and astrocytoma. Postoperative imaging confirmed the absence of clinically and radiographically relevant hemorrhage. The findings on SVS correlated with the pathology in all seven cases (100%). In 13 of 17 patients (76%) who had TSI, the spectra correlated well with the permanent pathologic examination. The SVS and TSI spectra were similar in six of seven (86%) cases. Intraoperative MRS-guided brain biopsy using a trajectory guide is a simple, safe, and accurate technique for accessing areas of the brain of diagnostic interest. J. Magn. Reson. Imaging 2001;13:12-15.

Biopsy, Needle↗
PubMed2001

Biopsy needle tip artifact in MR-guided neurosurgery.

A thorough understanding of both the appearance and origin of metallic biopsy needle tip artifact in magnetic resonance imaging (MRI) as well as its interaction with various magnetic resonance (MR) sequence parameters is beneficial for its application in today's MR-guided therapeutic procedures. In a more practical setting, this investigation has focused on the characteristics of MR image artifacts associated with a finite-length metallic needle, specifically at the tip of a biopsy needle when it is approximately parallel to the main magnetic field. The image artifact at needle tip, which exhibits as a blooming ball-shaped signal void, was demonstrated and studied using MR imaging and numerical simulation employing the finite difference method (FDM). In order to understand the origin of this image artifact, a numerical model or simulation software based on the FDM has been developed specifically to solve for the field disturbance to a uniform magnetic field due to a finite-length metallic needle. The solution for magnetic field shows that the field disturbance is spatially localized at the needle tip. From the numerical results, simulated images were generated which were in a very satisfactory agreement MR imaging experiment. Results showed that the MR image artifacts associated with MR-compatible metallic biopsy needles are not only present due to the magnetic susceptibility difference between the needle and its surrounding tissue, but also predictable in routine MR-guided procedures, and the size of the image artifacts could be reduced if optimal imaging parameters were used. J. Magn. Reson. Imaging 2001;13:16-22.

Artifacts↗
PubMed2001

Prospective stereotaxy: a novel method of trajectory alignment using real-time image guidance.

PURPOSE: To describe prospective stereotaxy, a novel method of trajectory alignment that works in real-time. MATERIALS AND METHODS: Prospective stereotaxy was used in minimally-invasive neurosurgical procedures in 74 patients since February 1999. This methodology differs from framed and frameless stereotaxy, both of which are based on retrospective data. Rather, prospective stereotaxy uses real-time MR images to align a surgical trajectory. RESULTS: Phantom tests and clinical procedures in all patients were successfully performed using prospective stereotaxy. In all cases, surgical targets were accessed, and the diagnostic yield of neurobiopsy using prospective stereotaxy was 100%. CONCLUSION: Prospective stereotaxy is applicable to all cross-sectional imaging, and is particularly useful for MR- and CT-guided interventions. The method is simple, reproducible, and accurate in surgical targeting for neurobiopsy and electrode placement. It does not require cumbersome stereotactic frames or expensive optical detectors, and it offers immediate entry into the field of interventional MR with cylindrical MR scanners.

Biopsy, Needle↗
PubMed2001

An efficient chemical shift imaging scheme for magnetic resonance-guided neurosurgery.

An efficient magnetic resonance spectroscopic imaging (MRSI) or chemical shift imaging (CSI) technique based on multiple spin echoes (MSE) has been implemented, validated, and used in both phantom and in vivo MR-guided neurosurgical applications. The key concept of the method is to employ MSE to significantly speed up the data collection rate for mapping hydrogen-containing metabolites. Using an echo train length (ETL) of three per excitation to simultaneously fill three consecutive k-space areas, the total scan time for a spectroscopic image matrix size of 32 x 32 has been shortened to approximately 11 minutes. An interecho spacing time of 273 msec was used to null the phase anomalies of lactate double peaks due to the J-coupling. This allowed a sufficient long data sampling time to achieve 4 Hz spectral resolution. Performing CSI intraopertively during an MR-guided neurosurgical procedure was shown to be feasible at 1.5 T. More importantly, it was shown that more relevant information can be obtained regarding neurochemistry about a targeted lesion, in addition to conventional MR morphological imaging noninvasively. In 25 MR-guided neurosurgical cases, the alleviated choline signal has been found to be consistent with the existence of rapid tumor cell proliferation in the corresponding area. The actual neurobiopsy guided by the spectroscopic imaging method demonstrated that it could provide valuable information in specifying the optimal site in a biopsy procedure, especially in the case involving a nonenhancing tumor. The multiecho scheme has made the CSI technique efficient enough to be routinely used in MR-guided surgical procedures at 1.5 T and also allows the possibility of taking full advantage of MRI capability.

Adult↗
PubMed2001

Subarachnoid hemorrhage associated with cyclosporine A neurotoxicity in a bone-marrow transplant recipient.

We report subarachnoid hemorrhage associated with cyclosporine A (CSA) neurotoxicity after bone-marrow transplantation for chronic myelogenous leukemia. CT showed occipital subarachnoid hemorrhage. MRI confirmed this, and demonstrated cortical and subcortical edema in the posterior temporal, occipital, and posterior frontal lobes bilaterally, which was typical of CSA neurotoxicity. Recognition of CSA neurotoxicity as the cause of the subarachnoid hemorrhage obviated angiographic investigation. After cessation of cyclosporine therapy, the cortical and subcortical edema resolved on follow-up MRI with some residual blood products in the subarachnoid space.

Adult↗
PubMed2001

Intraspinal epidermoid cyst: diffusion-weighted MRI.

We report a 7-year-old boy who presented with two-month history of worsening low back and right leg pain. Conventional MR images demonstrated a poorly outlined intradural mass recognized by the displacement of the conus medullaris and the nerve roots of the cauda equina at the L2-3 level. The signal intensity of the lesion was similar to CSF There was no contrast enhancement of the lesion. Diffusion-weighted images and ADC values revealed restricted diffusion within the mass. Myelography confirmed the mass as an intradural filling defect with myelographic block at the L2-3 level. The patient underwent total surgical excision of the mass. Pathologic examination revealed the diagnosis of epidermoid cyst.

Child↗
PubMed2001

Intra-operative MRI-guided approaches to the pediatric posterior fossa tumors.

INTRODUCTION: The posterior fossa in a child poses a considerable challenge to the neurosurgeon. MRI-guided surgery allows for real time interaction between imaging and the neurosurgeon, not permitted by frameless stereotaxy, and with higher resolution than ultrasound or CT. MATERIALS AND METHODS: The University of Minnesota 1.5 T Phillips interventional MRI was used. From 1997 to 2000, nine posterior fossa intraoperative magnet cases out of eleven were pediatric. The mean age was 6.4 years and the median age 7. Seven midline craniotomies were performed, of which three were re-operations. Two were burr hole placements, one for cyst aspiration and P32 instillation, and the other for tumor biopsy. RESULTS: Two tumors were predominantly in the fourth ventricle, four in the cerebellum, two in the brainstem, and one in the prepontine cystern. Four tumors were juvenile pilocytic astrocytomas, two were anaplastic astrocytomas, and one each was ependymoma, craniopharyngioma cyst, and medulloblastoma. Four patients had complete radiologic resection. Two had maximal resections limited by vital structures. P32 instillation and tumor biopsy were done in a single pass. Follow-up ranged from 3 months to 1.4 years. The cyst that was aspirated and had P32 instillation remains absent. The two mortalities were in the patients with medulloblastoma and anaplastic astrocytoma. There were no intra-operative mortalities. The other patient with anaplastic astrocytoma progressed. The remainder had stable imaging. CONCLUSION: MRI-guided surgery results in improved resection imaging and real-time needle guidance in tumor operations. Its value could lie in low-grade lesions, where maximal resection is most beneficial.

Child↗
PubMed2001

Brain biopsy sampling by using prospective stereotaxis and a trajectory guide.

OBJECT: The authors describe their initial results obtained using a skull-mounted trajectory guide for intraoperative magnetic resonance (MR) imaging-guided brain biopsy sampling. The device was used in conjunction with a new methodology known as prospective stereotaxis for surgical trajectory alignment. METHODS: Between January 1999 and March 2000, 38 patients underwent 40 brain biopsy procedures in which prospective stereotaxis was performed with the trajectory guide in a short-bore 1.5-tesla MR imager. In most cases, orthogonal T2-weighted half-Fourier acquisition single-shot turbo spin-echo (HASTE) images were used to determine the desired trajectory and align the device. The surgical trajectory was defined as a line connecting three points: the target, pivot, and alignment stem points. In all cases, surgical specimens were submitted for frozen section and pathological examination. Postoperative turbofluid-attenuated inversion-recovery and gradient-echo images were obtained to exclude the presence of hemorrhage. Trajectory determination and alignment was simple and efficient, requiring less than 5 minutes. Confirmatory HASTE images were obtained along the biopsy needle as it was being advanced or after reaching the target. All biopsy procedures yielded diagnostic tissue. One patient with a lesion near the motor strip experienced a transient hemiparesis of the hand related to passage of the biopsy needle, and another sustained a fatal postoperative myocardial infarction. No patient suffered a clinically significant or radiologically visible hemorrhage. CONCLUSIONS: In combination with prospective stereotaxis, the trajectory guide provided a safe and accurate way to perform brain biopsy procedures.

Adolescent↗
PubMed2001

Preliminary assessment of turbo spectroscopic imaging for targeting in brain biopsy.

BACKGROUND AND PURPOSE: Brain biopsy remains an integral and necessary component in the diagnosis of brain lesions. We assessed the ability of turbo spectroscopic imaging (TSI) to provide a physiologically based target for tissue sampling. METHODS: TSI was performed in 26 anesthetized patients immediately before MR-guided brain biopsy. In 10 patients, single-voxel spectroscopy was performed on the TSI-indicated target and correlated with the TSI findings. Biopsy samples were taken from the imaging and spectroscopically defined target(s) under MR guidance, and pathologic findings were compared with preoperative spectra. RESULTS: TSI alone provided a definitive target based on a region of elevated choline in 17 of 21 patients in whom a neoplasm was confirmed. The remaining four neoplasms exhibited relatively low metabolic levels and were difficult to distinguish from the five cases of radiation necrosis seen in this study. TSI findings were in qualitative agreement with those obtained at single-voxel spectroscopy, although TSI spectra exhibited more contamination. Quantitative spectral analysis of TSI data is limited by low spectral resolution. CONCLUSION: TSI is helpful for determining an appropriate biopsy target in heterogeneous lesions. Coupling TSI targeting with conventional imaging and intraoperative confirmation of needle positioning resulted in a 100% diagnostic success rate and increased the clinician's confidence in the histologic findings.

Adolescent↗
PubMed2001

Perfusion MR neuroimaging in patients undergoing balloon test occlusion of the internal carotid artery.

BACKGROUND AND PURPOSE: We sought to investigate whether the combination of conventional, diffusion-weighted, and perfusion-weighted MR imaging increases the diagnostic accuracy of balloon test occlusion of the internal carotid artery. We describe perfusion anomalies and patterns of enhancement seen in areas of altered brain perfusion during MR-monitored temporary balloon occlusion of the internal carotid artery. METHODS: Nine patients underwent balloon occlusion testing under standard angiographic conditions with continuous clinical and EEG monitoring. One patient who failed the test by clinical criteria underwent an external carotid to internal carotid bypass operation, followed by a repeat balloon test occlusion, thereby bringing the total number of procedures to 10. Patients were further imaged at 1.5 T with perfusion- and diffusion-weighted imaging as well as with conventional noncontrast and contrast-enhanced turbo fluid-attenuated inversion recovery (FLAIR) and T1-weighted sequences. RESULTS: Seven of 10 patients who tolerated unilateral carotid test occlusion without adverse clinical neurologic or EEG changes exhibited delayed first-pass transit of contrast material through the affected cerebral hemisphere, indicative of altered perfusion without significant concurrent cerebral blood flow or blood volume changes. Four of these patients and both symptomatic patients showed pial or subarachnoid contrast staining in areas of altered perfusion without abnormalities on diffusion-weighted images. CONCLUSION: Our findings indicate that MR perfusion-weighted imaging is safe and easily accomplished in a high-field-strength magnet and that contrast-enhanced turboFLAIR imaging may provide clinically useful MR imaging evidence of abnormal cerebral blood flow and subclinical ischemia.

Adult↗
PubMed2001

Intraoperative MR systems. High-field approaches.

Since the introduction of MR-guided neurosurgery, the field has evolved considerably. As it has been convincingly demonstrated, MR-guided therapy seems to be feasible and safe at all clinical field strengths up to 1.5 T. This article discusses the technology of MR-guided therapy at 1.5 T, and in particular, the multiple approaches that have been advanced to date.

Brain↗
PubMed2001

Optimizing brain tumor resection. High-field interventional MR imaging.

High-field strength iMRI guidance is an effective tool for brain tumor resection. Although its use lengthens the average time for a craniotomy, the reward is a more extensive tumor excision compared with conventional neurosurgery without an increased risk to the patient (Table 4). Although intraoperative patient transfer into and out of the magnet is cumbersome, the possibility for complete resection, especially for a low-grade glioma, makes the effort worthwhile. The cost and technical support required for this system presently limits its use to only a few sites worldwide. As with any technology, further refinements will make this system less expensive and more attainable. Practical consideration aside, high-field strength iMRI is presently [table: see text] the most effective tool available for brain tumor resection. Because of its novelty, future studies are necessary to determine if this technology lowers the incidence of and extends the duration to tumor recurrence as the preliminary data in children suggests. These are the ultimate measures of efficacy for any brain tumor treatment. Based on the rapid advancement of technology, will today's high-field strength interventional magnet become tomorrow's low-field system? Very high-field strength designs may improve diagnostic capabilities through higher resolution, but their interventional applications may be hindered by increased sensitivity for clinically insignificant abnormalities and decreased specificity for clinically relevant lesions. As new technology is developed, clinicians must continue to explore and refine the existing high-field strength iMRI to make it cost-effective and widely applicable.

Adolescent↗
PubMed2001

Neuronavigation in interventional MR imaging. Prospective stereotaxy.

A practical MR imaging-based guidance/control methodology has been developed successfully and validated for improving the performance of stereotactic neurosurgerical procedures such as brain lesion biopsy. The use of the device and method in 40 routine MR-guided procedures has revealed its potential as an alternative approach. Superior to the traditional stereotactic systems, which rely on the old images, the new method, based on prospective guidance, can provide good and acceptable targeting accuracy in the presence of brain shift. Furthermore, the use of MR monitoring of the overall neurosurgical procedure provides another independent assurance for the success of a complicated surgery. The advantages of the new surgical guidance system and method are simple and compatible with the existing capabilities of conventional MR scanners. More importantly, it allows a more effective surgical guidance in the presence of brain shift during the typical neurosurgery. Another important advantage of the guidance method and device is the performance of a truly MR-guided neurosurgical procedure in a conventional, short bore high field MR scanner. Surgical procedures using the guidance system and method have been accepted by radiologists and neurosurgeons as an attractive MR-based stereotactic approach. It can be expected that this guidance scheme will be a useful addition to the MR-based stereotactic system for neurosurgery, and animal research, in which cumbersome stereotactic frames have been used.

Biopsy, Needle↗
PubMed2001

Minimally invasive procedures. Interventional MR image-guided functional neurosurgery.

Intraoperative MR imaging techniques have the potential to greatly improve the stereotactic methods used for functional neurosurgery. No longer are neurosurgeons and patients always constrained by uncomfortable head frames and conventional stereotaxy. Accuracy and complication avoidance are improved by intraoperative imaging. Safety of operative machinery and equipment in an MR imaging operative suite is attainable, even with deep brain stimulating electrodes in depth electrodes for epilepsy. Although cost-effectiveness remains to be determined (see article by Kucharczyk et al in this issue), the minor inconveniences of operating within an iMRI environment seem to be significantly outweighed by the benefits.

Brain↗
PubMed2001

Cost-efficacy of MR-guided neurointerventions.

This article summarizes the available data on the cost-efficacy of interventional MR imaging and discusses its potential future role in the diagnosis and management of neurologic diseases and disorders.

Humans↗
PubMed2000

Functional neuroanatomy of spatial working memory in children.

Functional magnetic resonance imaging (fMRI) was used to examine spatial working memory in 8- to 11-year-old children tested under three conditions. In the visual condition, children were asked to examine the location of a dot on a screen. In the motor condition, children were instructed to push a button that corresponded to the location of a dot presented on a screen. In the memory condition, children were asked to remember the location of a dot presented 1 or 2 trials previously. Subtracting the activation of the motor condition from the memory condition revealed activity in the dorsal aspects of the prefrontal cortex and in the posterior parietal and anterior cingulate cortex. These findings were also obtained in the analysis of the memory minus visual conditions except that motor cortex activation was also observed. These findings parallel those reported in comparable studies of adults and suggest that fMRI may be a useful means of examining function-structure relations in developmental populations.

Adult↗