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Biomedical subjects

W A Hall

Publications and source records attributed to W A Hall.

At least 19 recordsLinked to original sources
PubMed2006

Programmable shunt-related suicide attempt.

The treatment of hydrocephalus has benefited recently from the use of programmable shunt valves. These devices can be adjusted using magnets to regulate how much spinal fluid is drained. However, it is unclear to what extent other environmental magnetic sources can affect programmable valves. We present the case of a man who attempted suicide by successfully turning his adjustable valve to a near-maximal setting using a hand-held electromagnet, and discuss other reported cases in order to better understand the effects of environmental magnets on programmable shunt valves.

Brain↗
PubMed2006

Effects of an intervention aimed at reducing night waking and signaling in 6- to 12-month-old infants.

This quasi-experimental one-group pre- and posttest pilot study evaluated an intervention aimed at reducing night waking and signaling for infants between 6 and 12 months of age. Thirty-nine healthy infants and their parents were recruited. Thirty-five infants completed the intervention and data collection. Both parents participated in a group teaching session with telephone follow-up for 2 weeks. Actigraphy and sleep diary data were collected at baseline and 6 and 16 weeks postintervention. We hypothesized a decrease in length and number of infant waking and crying periods and an increase in longest night sleep and nap time. Following the intervention, infants had significantly reduced length of night crying and number of wakes and longer night sleep periods. The intervention warrants evaluation with a randomized controlled design.

Adult↗
PubMed2003

The roles of functional MRI in MR-guided neurosurgery in a combined 1.5 Tesla MR-operating room.

BACKGROUND AND PURPOSE: During MR-guided neurosurgical procedures performed in a combined 1.5 Tesla MR-operating room (MR-OR), we have successfully implemented and validated a functional MRI (fMRI) scheme for efficiently localizing eloquent functional areas and assessing their proximity to a lesion volume immediately prior to the craniotomy. METHODS: The fMRI examination consists of a dynamical blood oxygenation level dependent (BOLD) MR imaging technique and a task paradigm that is designed to activate the brain area of interest. The functional imaging technique was based on gradient-echo (GE) echo-planar imaging (EPI) (TR/TE = 2000-3000/40-50 msec). The motor task paradigm involves a periodic movement task, such as alternating between thumb and the other four fingers as a finger-tapping task, while the language involved a covert repeat of a series of words given as a task stimulus. While patient is performing the task, a dynamical fMRI was performed concurrently covering the volume of interest every 2 or 3 sec. Also, we have used a temporal series averaging (TSA) method for correcting the background drift in the raw fMRI signal, and developed a scheme for presenting fMRI results to neurosurgeons in an intuitive 3-dimensional volume-rendered display format. RESULTS: By using the fMRI scheme, we have successfully performed sixteen fMRI examinations immediately prior to neurosurgery in the combined MR-OR on the same surgical table to localize various eloquent functional areas of interests. TSA was successful in reducing the background drift in the fMRI time course data, and the 3-dimensional volume-rendered display was proven effective in presenting the resulting brain activations to neurosurgeons. More importantly, in three representative cases (one biopsy and two tumor resections) presented, the information provided by fMRI have indeed contributed significantly in making the optimal surgical decisions prior to craniotomy. CONCLUSIONS: Intra-operative fMRI can be an indispensable tool for determining the location of a neighboring eloquent functional area of concern in reference to a targeted lesion. Information provided by fMRI has helped in improving the outcome and clinician confidence of all surgeries performed.

Adolescent↗
PubMed2003

Costs and benefits of intraoperative MR-guided brain tumor resection.

We retrospectively compared the costs and benefits of brain tumor resection in the conventional operating room (cOR) with the interventional magnetic resonance (iMR) suite from 1993-1998. Comparisons were made for adults (diagnosis-related group (DRG) 001) and children (DRG 003) for length of stay (LOS), hospital charges and payments, hospital total direct and indirect costs, readmission rates, repeat resection (RR) interval, and net health outcome. Statistical analysis was with ANOVA, Dunnett's, and Bonferroni tests. For DRG 001, iMR LOS (3.7 days (d)) was 54.9% shorter than for cOR (8.2 d) for first resections (FR) (P < 0.001) and RR (6.0 vs. 8.7 d (31.0%), P < 0.05). IMR hospital charges were 12.2% lower ($4063) for FR and 4.1% lower ($922) for RR than for cOR. Total iMR hospital costs were 14.4% lower ($3415) than for cOR for FR and 3.3% lower ($723) than costs for RR. Cost-to-charge ratio (c/c) for FR was 69.6% (iMR) and 71.4% (cOR) and for RR 70.9% (iMR) and 71.1% (cOR). For DRG 003, iMR LOS (4.5 d) was shorter than for cOR (14.1 d, P < 0.001) for FR and for RR (8.0 vs. 13.3 d). IMR hospital charges were 43.8% lower than for cOR for FR (P < 0.05) and RR. The iMR costs were lower for FR (46.4%, P < 0.01) and RR (44.7%) than cOR. IMR c/c was 71.4% and 74.8% for cOR. For RR, the iMR c/c was 72.8% and 73.9% for cOR. No RR have followed iMR surgery. COR RR rate was 20% in adults and 30% in children. The mean time from iMR surgery was 11.3 months in adults and 18.0 in children. For the cOR, the mean time to RR was 9.3 months in adults and 13.3 in children. This data suggests that iMR surgery improves net health outcomes by reduced LOS, reduced RR, and reduced hospital charges and costs.

Adolescent↗
PubMed2003

Influence of 1.5-Tesla intraoperative MR imaging on surgical decision making.

To determine the frequency that high-field magnetic resonance (MR) imaging sequences influenced surgical decision making during intraoperative MR-guided surgery. From January 1997 to February 2001, 346 MR-guided procedures were performed using a 1.5-Tesla MR system (NT-ACS, Philips Medical Systems). This system can perform functional MR imaging (fMRI), diffusion weighted imaging (DWI), MR spectroscopy (MRS), MR angiography (MRA), and MR venography (MRV) in addition to T1-weighted, T2-weighted, and turbo FLAIR (fluid-attenuated inversion recovery) imaging. FMRI was used to determine areas of brain activation for language, motor function, and memory. DWI was utilized after tumor resection to exclude cerebral ischemia or infarction. MRS was obtained to identify areas of elevated choline that were suspected to correlate with tumor presence. MRA and MRV localized vascular structures adjacent to tumors prior to resection. The intraoperative procedures performed included 140 brain biopsies of which 82 utilized a trajectory guide and prospective stereotaxy. MRS was used in 42 biopsies (30%), of which 29 had turbo spectroscopic imaging (TSI) and 21 had single voxel spectroscopy (SVS). In all biopsy cases, diagnostic tissue was obtained. There were 103 tumor resections of which 18 (17%) had MRS. Functional MRI was used in 17 cases; 3 biopsies (2%) and 14 planned resections (14%). Speech function was localized in 3 cases, memory function in 3, and motor function in 11. In one case where the motor function of the tongue was intimately involved with a low-grade glioma, resection was not attempted. DWI was used in less than 10% of tumor resections. MRA and MRV were performed in 3 (3%) and 2 (2%) of tumor resections, respectively. The imaging capabilities (i.e., fMRI, DWI, MRA, MRV) associated with high-field intraoperative MR influenced surgical decision making primarily for tumor resections. MRS influenced target selection during brain biopsy.

Biopsy↗
PubMed2003

Selective cyclooxygenase-2 inhibition does not affect the healing of cutaneous full-thickness incisional wounds in SKH-1 mice.

BACKGROUND: The inducible cyclooxygenase-2 (COX-2) enzyme is upregulated in inflammatory diseases, as well as in epithelial cancers, and has an established role in angiogenesis and tissue repair. OBJECTIVE: Because of these physiological effects and the widespread use of the selective COX-2 inhibitor, celecoxib, we wanted to determine if inhibition of COX-2 would affect incisional skin wound healing. METHODS: Using a cutaneous full-thickness, sutured, incisional wound model in hairless SKH-1 mice, we evaluated the role of COX-2 in the wound healing process by comparing the effects of a nonselective COX inhibitor, diclofenac, with a selective COX-2 inhibitor, SC-791. Healing was monitored for up to 28 days postincision histologically and for recovery of wound strength. RESULTS: COX-2 expression was observed over the first week of healing, peaking at day 3 and was not affected by treatment with the selective COX-2 or nonselective COX inhibitors. Infiltrating macrophages, as well as keratinocytes and dermal fibroblasts at the wound site, expressed COX-2. Neither selective COX-2, nor nonselective COX inhibition had a significant effect on the macroscopic or microscopic morphology of the wounds, whereas dexamethasone treatment resulted in epidermal and granulation tissue atrophy. In addition, neither selective COX-2, nor nonselective COX inhibition altered keratinocyte proliferation and differentiation, dermal angiogenesis or the recovery of wound tensile strength, whereas dexamethasone reduced the tensile strength of the wounds by 30-38% throughout the healing period. CONCLUSIONS: These data indicate that selective COX-2 inhibition does not affect the healing of surgical skin wounds.

Animals↗
PubMed2003

Measurement and analysis of brain deformation during neurosurgery.

Recent studies have shown that the surface of the brain is deformed by up to 20 mm after the skull is opened during neurosurgery, which could lead to substantial error in commercial image-guided surgery systems. We quantitatively analyze the intraoperative brain deformation of 24 subjects to investigate whether simple rules can describe or predict the deformation. Interventional magnetic resonance images acquired at the start and end of the procedure are registered nonrigidly to obtain deformation values throughout the brain. Deformation patterns are investigated quantitatively with respect to the location and magnitude of deformation, and to the distribution and principal direction of the displacements. We also measure the volume change of the lateral ventricles by manual segmentation. Our study indicates that brain shift occurs predominantly in the hemisphere ipsi-lateral to the craniotomy, and that there is more brain deformation during resection procedures than during biopsy or functional procedures. However, the brain deformation patterns are extremely complex in this group of subjects. This paper quantitatively demonstrates that brain deformation occurs not only at the surface, but also in deeper brain structure, and that the principal direction of displacement does not always correspond with the direction of gravity. Therefore, simple computational algorithms that utilize limited intraoperative information (e.g., brain surface shift) will not always accurately predict brain deformation at the lesion.

Adult↗
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

Does the extent of surgery have an impact on the survival of patients who receive postoperative radiation therapy for supratentorial low-grade gliomas?

We evaluate the impact of extent of surgery (EOS) on survival of patients with supratentorial nonpilocytic low-grade gliomas (LGG) treated with postoperative radiation therapy (PORT). Sixty-five patients with pathologically confirmed supratentorial nonpilocytic LGG (36 astrocytomas and 29 oligodendrogliomas) were treated with PORT after different extents of surgery: 12 gross total resections (GTR), 27 minimal or subtotal resections (MR/SR), and 26 biopsies (B). EOS was confirmed with postoperative imaging. The median radiation dose delivered was 5,940 cGy (range, 4,950-6,620 cGy). One of 12 patients (8%) in the GTR group and 12 of 53 patients (23%) in the less than GTR group demonstrated contrast enhancement. The median follow-up was 61 months (range 5-194 month). The 10-year overall survival (OS) was 82.5% and 32% for the GTR and the less than GTR groups, respectively (P = 0.0008). The corresponding 10-year disease-specific survival (DSS) was 90% and 41.4%%, respectively (P = 0.001). Multivariate analysis showed that only contrast enhancement and EOS were predictors for OS and DSS. Our data suggest that EOS correlates with OS and DSS in patients who have PORT. GTR should be the goal if technically achievable without causing significant morbidity, and its combination with PORT is compatible with long-term survival.

Adult↗
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

Immunization with dendritic cells pulsed with tumor extract increases survival of mice bearing intracranial gliomas.

The purpose of this study is to investigate the efficacy of dendritic cell-mediated immunotherapy against intracranial gliomas. Cloned DC2.4 dendritic cells originating from C57BL/6 mice were pulsed with glioma GL261 cell extracts and administered i.p. to C57BL/6 mice with intracranial GL261 gliomas. The survival of mice with and without pulsed dendritic cells was monitored after intracranial implantation of the GL261 glioma cells. Fluorescence activated cell sorting (FACS) analysis showed that DC2.4 cells express high levels of MHC class I and class II molecules, costimulatory molecules B7-1 and B7-2, and the cell adhesion molecule ICAM-1. Antigen-presenting capabilities in these dendritic cells were initially characterized in vitro by a mixed lymphocyte reaction, showing that Balb/c CD4+ and CD8+ T cells were able to generate allogeneic responses to DC2.4 cells. Tumor extract-pulsed DC2.4 dendritic cells were then used for the treatment of C57BL/6 mice with syngeneic GL261 gliomas. Animals with intracranial GL261 gliomas and vaccinated i.p. with pulsed DC2.4 dendritic cells exhibited significantly enhanced survival, relative to animals treated with saline or non-pulsed DC2.4 cells alone. In addition, cured animals showed an increased delayed-type hypersensitivity response to GL261 cells and survived when rechallenged with intracranial GL261 gliomas. In summary these results indicate that dendritic cells pulsed with tumor extract can enhance immune responses to tumor antigen and therefore represent a potential immunotherapeutic approach for treating patients with intracranial gliomas.

Animals↗
PubMed2001

Importance of dose intensity in neuro-oncology clinical trials: summary report of the Sixth Annual Meeting of the Blood-Brain Barrier Disruption Consortium.

Therapeutic options for the treatment of malignant brain tumors have been limited, in part, because of the presence of the blood-brain barrier. For this reason, the Sixth Annual Meeting of the Blood-Brain Barrier Disruption Consortium, the focus of which was the "Importance of Dose Intensity in Neuro-Oncology Clinical Trials," was convened in April 2000, at Government Camp, Mount Hood, Oregon. This meeting, which was supported by the National Cancer Institute, the National Institute of Neurological Disorders and Stroke, and the National Institute of Deafness and Other Communication Disorders, brought together clinicians and basic scientists from across the U.S. to discuss the role of dose intensity and enhanced chemotherapy delivery in the treatment of malignant brain tumors and to design multicenter clinical trials. Optimizing chemotherapy delivery to the CNS is crucial, particularly in view of recent progress identifying certain brain tumors as chemosensitive. The discovery that specific constellations of genetic alterations can predict which tumors are chemoresponsive, and can therefore more accurately predict prognosis, has important implications for delivery of intensive, effective chemotherapy regimens with acceptable toxicities. This report summarizes the discussions, future directions, and key questions regarding dose-intensive treatment of primary CNS lymphoma, CNS relapse of systemic non-Hodgkin's lymphoma, anaplastic oligodendroglioma, high-grade glioma, and metastatic cancer of the brain. The promising role of cytoenhancers and chemoprotectants as part of dose-intensive regimens for chemosensitive brain tumors and development of improved gene therapies for malignant gliomas are discussed.

Adult↗
PubMed2001

Focal intracranial infections due to Propionibacterium acnes: report of three cases.

OBJECTIVE AND IMPORTANCE: Except for its role in shunt infections, Propionibacterium acnes has been of little interest to neurosurgeons. The rarity and indolent nature of focal intracranial infections by P. acnes limit their recognition. Three cases of serious intracranial infection due to this organism are described. CLINCAL PRESENTATION: Three patients with histories of immunosuppression and neurosurgical procedures developed nonspecific, delayed presentations (5 wk to 5 yr after surgery) of intracranial infections. In two patients, radiological investigations showed enhancing lesions that were later found to be brain abscesses. A subdural empyema was found in the third patient. INTERVENTION: All three patients underwent surgical drainage of the purulent collections. P. acnes was isolated in each case, and each patient was treated with a 6-week course of intravenous penicillin. All three patients made good recoveries, and subsequent imaging showed no recurrence of the infectious collections. CONCLUSION: P. acnes is an indolent organism that may rarely cause severe intracranial infections. This organism should be suspected when an intracranial purulent collection is discovered in a patient with a history of neurosurgical procedures. Immunosuppressed patients may be susceptible to this otherwise benign organism. Surgical drainage and treatment with intravenous penicillin should be considered standard therapy.

Adult↗
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

Enhancing the rigor of grounded theory: incorporating reflexivity and relationality.

Some proponents of the grounded theory method appear to treat interview and participant observation data as though they mirror informants' realities. Others claim that grounded theory incorporates reflexivity. It is claimed in this article that the principal texts on grounded theory do not attend to the effects of interactions between researchers and participants in interview and participant observation contexts. Descriptions of the effects of interactions on interview data and attention to relationships between interviewers and interviewees are necessary for attending to the rigor of grounded theory findings. Therefore, it is argued that reflexivity and relationality, which are defined as attending to the effects of researcher-participant interactions on the construction of data and to power and trust relationships between researchers and participants, should be incorporated into grounded theory.

Focus Groups↗