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Biomedical subjects

W A Hall

Publications and source records attributed to W A Hall.

At least 73 records · Page 4Linked to original sources
PubMed1995

Maintaining accuracy in stereotactic radiosurgery.

PURPOSE: To provide the manufacture's specification for the base phantom of a commercially available stereotactic radiosurgery system so that its accuracy can be confirmed, and to describe a calibration device that allows the accuracy of the base phantom to be verified quickly and on a routine basis. Modifications to the target pointer system that make matching the pointer tips easier and less likely to damage the pointer tips are also described. METHODS AND MATERIALS: In stereotactic radiosurgery, spatial accuracy is the key factor for successful dose delivery. With some commercially available systems, this accuracy depends on the accuracy of the base phantom coordinate system, how closely the tip of the target pointer can be matched to the tip of the base phantom pointer, and how accurately the coordinates set on the isocentric subsystem match those set on the base phantom. Two major problems, usually overlooked when evaluating system accuracy are, first, the base phantom, which establishes the stereotactic coordinate system, is assumed to be completely accurate. This is a dangerous assumption because the base phantom is used frequently for routine patient treatments and for standard quality assurance tests. To exacerbate the problem, no independent device is provided with stereotactic systems to check the accuracy of the base phantom. Second, the accuracy of the isocenter coordinates set on the head support stand depends upon how closely the target pointer and the base phantom pointer can be aligned. The hardware provided with the system is difficult to use and easily leads to damage of the pointer tips. RESULTS: In this work, we provide the manufacturer's specifications for a popular stereotactic system, describe a device that can be used to check quickly and easily the accuracy of the base phantom, and describe a modification to the transfer pointer system that allows the pointer tips to be more easily aligned with reduced possibility of damage to the pointer tips. CONCLUSION: The methods and apparatus described in this paper should be useful to anyone using a base phantom for testing radiosurgery accuracy.

Equipment Design↗
PubMed1995

Diagnosis, management, and survival of patients with leptomeningeal cancer based on cerebrospinal fluid-flow status.

BACKGROUND: The authors assessed cerebrospinal fluid (CSF) flow in patients with carcinomatous meningitis using technetium-99m-DTPA (Tc-99) ventriculography to determine the frequency of flow abnormalities, their reversibility with treatment, and the implications for successful therapy and survival. METHODS: Technetium-99m-DTPA flow studies were performed in 31 patients after placement of Ommaya reservoirs (Baxter, McGaw Park, IL). Two millicuries of Tc-99 were injected into the reservoir. Planar images of the head and entire spine were obtained after 10 and 30 minutes and after 1, 4, 6, and 24 hours. Follow-up studies were performed for 12 patients whose initial studies were abnormal or who developed complications of therapy. RESULTS: In 19 of the 31 patients (61%), ventricular-outlet, spinal, or convexity blocks were identified. In 11 of these 19 patients, focal radiotherapy to the site of the block restored normal flow. Survival among patients with initially normal, abnormal but correctable, and abnormal but uncorrectable CSF flow differed significantly (6.9, 13.0, and 0.7 months respectively; P < 0.001). Some patients who were treated intrathecally despite abnormal CSF flow experienced drug-related toxicity. CONCLUSIONS: Cerebrospinal fluid-flow blocks are common in patients with carcinomatous meningitis and may occur at the skull base, in the spinal canal, and over the convexities. These flow abnormalities often can be corrected with appropriately directed radiotherapy. If untreated, CSF tumor progression (protected site effect), neurotoxicity (high concentration effect), and systemic toxicity (reservoir effect) can occur, resulting in shortened survival and treatment-related morbidity. Therefore, intrathecal chemotherapy should be preceded by a radionuclide flow study and should be delayed if abnormal flow is documented until appropriate radiotherapy reestablishes normal flow.

Adolescent↗
PubMed1995

Multifocal enhancing magnetic resonance imaging lesions following cranial irradiation.

Radiation necrosis is a delayed complication of cranial irradiation, typically presenting as a single intracerebral mass that is radiographically indistinguishable from recurrent tumor. We describe 6 patients with a distinct radiographic syndrome of multifocal enhancing lesions on magnetic resonance images, and their variable clinical courses: some fluctuating, some spontaneously resolving, and some demonstrating fulminant progression to frank necrosis.

Adult↗
PubMed1995

Sacrococcygeal chordoma metastatic to the brain with review of the literature.

A 29-year-old man presented with headache, confusion, word-finding difficulty, and a visual field deficit 16 months after complete removal of a sacrococcygeal chordoma. Magnetic resonance imaging of the head demonstrated two discrete enhancing left occipital lesions with associated cerebral edema. Both masses were surgically excised and their histological appearance was consistent with chordoma. Chordoma from the sacral region is known to metastasize to the lungs and the vertebral bodies but has rarely been shown to spread to the brain. Dissemination to the brain in this case may be related to the extent of the metastatic pulmonary disease and the anaplastic appearance of the primary tumor.

Adult↗
PubMed1995

Stereotactic radiosurgery for recurrent malignant gliomas.

PURPOSE: To evaluate the role of stereotactic radiosurgery in the management of recurrent malignant gliomas. PATIENTS AND METHODS: We treated 35 patients with large (median treatment volume, 28 cm3) recurrent tumors that had failed to respond to conventional treatment. Twenty-six patients (74%) had glioblastomas multiforme (GBM) and nine (26%) had anaplastic astrocytomas (AA). RESULTS: The mean time from diagnosis to radiosurgery was 10 months (range, 1 to 36), from radiosurgery to death, 8.0 months (range, 1 to 23). Twenty-one GBM (81%) and six AA (67%) patients have died. The actuarial survival time for all patients was 21 months from diagnosis and 8 months from radiosurgery. Twenty-two of 26 patients (85%) died of local or marginal failure, three (12%) of noncontiguous failure, and one (4%) of CSF dissemination. Age (P = .0405) was associated with improved survival on multivariate analysis, and age (P = .0110) and Karnofsky performance status (KPS) (P = .0285) on univariate analysis. Histology, treatment volume, and treatment dose were not significant variables by univariate analysis. Seven patients required surgical resection for increasing mass effect a mean of 4.0 months after radiosurgery, for an actuarial reoperation rate of 31%. Surgery did not significantly influence survival. At surgery, four patients had recurrent tumor, two had radiation necrosis, and one had both tumor and necrosis. The actuarial necrosis rate was 14% and the pathologic findings could have been predicted by the integrated logistic formula for developing symptomatic brain injury. CONCLUSION: Stereotactic radiosurgery appears to prolong survival for recurrent malignant gliomas and has a lower reoperative rate for symptomatic necrosis than does brachytherapy. Patterns of failure are similar for both of these techniques.

Actuarial Analysis↗
PubMed1995

In vitro and in vivo variation in transferrin receptor expression on a human medulloblastoma cell line.

The poor prognosis associated with pediatric central nervous system tumors such as medulloblastoma has led to the development and investigation of a variety of new treatment techniques. Therapeutic agents include targeted-toxin conjugates or immunotoxins that show significant in vitro activity against many brain tumors. Transferrin receptors (TRs) are specific, cell-surface antigens that are expressed preferentially on brain tumors rather than on normal human brain tissue. This antigen has been successfully targeted in human and nonhuman brain tumors in vitro and in vivo. In this study, when TRs were used as a target in the DAOY human medulloblastoma-derived cell line in vitro, a significant level of expression was confirmed by testing the sensitivity to different immunotoxins. To ensure the relevance of the in vitro data to the in vivo situation, we also analyzed TR expression in DAOY tumors growing in athymic mice and rats. Immunocytochemistry, immunohistochemistry, immunobead binding, immunofluorescence, 125iodine-transferrin binding, and Northern blot analysis were used to compare TR expression in DAOY cells in vitro and in vivo. All in vitro assays demonstrated significant TR expression, whereas in vivo, the TR expression was negligible in the DAOY tissue. The results caution against extrapolating in vitro antigen and receptor expression data directly to the in vivo situation. Using a transferrin-toxin conjugate in a nude rat model of leptomeningeal carcinomatosis, we achieved therapeutic efficacy, despite demonstrating reduced TR expression on tumor tissue. With respect to clinical efficacy, the reduced expression of TR on DAOY medulloblastoma in vivo may be less significant than expected because of the extreme potency of immunotoxins observed in central nervous system tumors.

Animals↗
PubMed1995

Functional magnetic resonance imaging as a management tool for cerebral arteriovenous malformations.

The location of eloquent cortex, such as the motor strip, the visual cortex, or Broca's area, may be difficult to predict even with multiprojectional magnetic resonance imaging (MRI). Distortion and displacement of this cortex may occur with a congenital lesion, such as an arteriovenous malformation, or by an acquired disease, such as a neoplasm. A desire to avoid damaging these eloquent areas by conventional surgery, radiosurgery, or endovascular surgery makes their accurate identification an important part of the pretherapeutic planning process. Blood oxygen level dependent functional MRI is a technique that uses the local increase of oxyhemoglobin concentration in the patient that occurs as a result of the increase in flow rate and blood volume in eloquent cortex undergoing stimulation from, for example, flashing lights, hand movements, or speech. We have used the blood oxygen level dependent technique to localize eloquent cortex relative to arteriovenous malformations and tumors. Using a 4.0-T magnetic resonance (MR) system, there is a sufficiently high degree of spatial resolution of the MR signal intensity changes during stimulation to allow the identification of eloquent cortex. Alternative, non-MR, invasive techniques for functional localization include electrocorticography and stimulation from subdural grids and strips. Noninvasive, non-MR technologies, such as positron emission tomography and magnetoencephalography, can also provide functional localization of eloquent cortex. However, the perfection of functional MRI at the 1.5-T field strength and the large number of such MR systems in operation mean that a highly accurate cerebral cortical localization technique can be available to most neuroscientists without the need to purchase alternative expensive technology.

Adult↗
PubMed1994

Pituitary magnetic resonance imaging in normal human volunteers: occult adenomas in the general population.

OBJECTIVE: To determine the prevalence of focal lesions of the pituitary gland that suggest the presence of a pituitary adenoma in asymptomatic persons. DESIGN: 100 normal volunteers (70 women, 30 men; age range, 18 to 60 years old) were studied by high-resolution magnetic resonance imaging (MRI) of the pituitary gland before and after administration of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA). SETTING: Occult pituitary adenomas are identified at autopsy in 3% to 27% of unselected asymptomatic patients. The frequency of incidental pituitary adenomas detected by MRI in normal persons is unknown. MEASUREMENTS: The MRI scans from volunteers were randomly mixed with scans of 57 patients with Cushing disease and interpreted independently by three blinded reviewers. RESULTS: Seven women (10%) and three men (10%) had focal areas of decreased signal intensity in the pituitary gland after administration of Gd-DTPA. The lesions ranged from 3 to 6 mm in greatest diameter and were diagnosed as pituitary adenomas by at least two of the three reviewers. When similar lesions were detected on MRI scans in patients with Cushing disease, the positive predictive value for identification of an adenoma at that site was 86%. CONCLUSIONS: About 10% of the normal adult population have pituitary abnormalities on MRI scans that are compatible with the diagnosis of asymptomatic pituitary adenomas. Most pituitary adenomas remain asymptomatic and do not require treatment.

Adenoma↗
PubMed1994

Nude rat models for human tumor metastasis to CNS. Procedures for intracarotid delivery of cancer cells and drugs.

Models for hematogenous spread of human cancer to the central nervous system (CNS) were established by injecting human tumor cells into the internal carotid artery of nude rats. With 4 out of 10 cell lines, belonging to four different tumor types, metastases developed in all injected animals. Tumor growth manifested clinically as neurological symptoms which appeared after a median latency ranging from 19-87 days for the different tumors. The H-146 and DMS-273 small cell lung cancers and the LOX melanoma almost exclusively gave meningeal tumors, whereas with FEMX-I melanoma cells bone metastases in the skull dominated. For these tumor types a correlation was found between the capacity for experimental metastasis formation and the s.c. tumorigenicity. In agreement with clinical experience, none of the 2 sarcoma and 2 glioblastoma lines gave CNS metastases. With a modified microsurgical technique, allowing for repeated ipsilateral intracarotid injections, we analyzed the drug concentrations obtained in tumor and surrounding brain tissue after i.v. treatment with doxorubicin. The concentration in the LOX tumor reached therapeutic levels and was approximately 100 x higher than in normal brain tissue, both with and without intraarterial pretreatment with arabinose. In the same model, the tissue concentrations of 9.2.27-abrin immunotoxin 10 min after intracarotid injection were examined. Although the levels were low, a tumor to brain concentration ratio of up to 9 was achieved. The data demonstrate that clinically relevant tumor models can be established with the techniques described, and these models may successfully be used to evaluate the pharmacokinetics and effect of intravenous or intraarterial therapy.

Animals↗
PubMed1994

Rhinocerebral mucormycosis: changing patterns of disease.

Eleven cases of rhinocerebral mucormycosis (RM) encountered over a 13-year period were reviewed. Predisposing factors included leukemia (36%), diabetes mellitus (27%), aplastic anemia (9%), myelodysplastic syndrome (9%), and treatment with immunosuppressive medications necessary to maintain solid organ or bone marrow graft viability (64%). Two patients had no predisposing factors. Clinical findings included headache (73%), fever (55%), black nasal eschar (45%), orbitofacial cellulitis (36%), cranial nerve palsy (36%), altered sensorium (36%), and hemiparesis (27%). Seven patients presented with destruction of the paranasal sinuses and local invasion; three with direct extension to the frontal or temporal lobes. Four patients displayed hematogenous dissemination to the cerebrum, brain stem, and cerebellum from a primary pulmonary focus. The seven patients with sinus involvement were treated with aggressive surgical debridement. Two patients with focal intracerebral lesions underwent either open craniotomy or stereotactic biopsy. Amphotericin B was administered intravenously to all patients. Local irrigation via a percutaneous catheter was performed in the seven patients with sinus disease and in one case of intracranial abscess. All seven patients with intracranial infection died, in contrast to four patients that survived with infection localized to the sinuses and orbits. All survivors had been treated with a combination of surgery and amphotericin B therapy. This review demonstrates that RM is increasingly affecting patients with sources of immunosuppression other than diabetes mellitus. Early aggressive therapy to prevent cerebral involvement by this severe infection provides the best chance for a good outcome.

Adolescent↗
PubMed1994

New fatherhood: myths and realities.

Despite evidence for the existence of nurturing fathers, little is known about how and why men increase their involvement with their children. The qualitative study from which these findings were taken explored the experience of 10 Canadian fathers in dual-earner families after the birth of their first infants. The constant comparative method was used to generate a grounded theory explicating the men's process of redefining their roles as spouses, workers, and fathers. Findings from 20 semi-structured interviews conducted with a purposive sample of fathers in their homes revealed that the fathers' experiences consisted of coping with many demands from children, partners, and jobs. These men redefined their roles as fathers after their partners returned to full-time employment. Two stages of monitoring role strain and limiting role strain captured the variation in behavior. This study contributes to community health nurses' understanding of how men respond to the lack of concurrence among societal expectations, others' expectations, and their own realities of fatherhood.

Adaptation, Psychological↗
PubMed1994

In vivo efficacy of intrathecal transferrin-Pseudomonas exotoxin A immunotoxin against LOX melanoma.

Neoplastic meningitis due to the dissemination of systemic cancer or primary central nervous system tumors through the cerebrospinal fluid carries a very poor prognosis. Current treatments for this disease are ineffective, and new therapeutic modalities such as immunotoxins may be beneficial. We created an animal model of human carcinomatous meningitis with LOX melanoma-derived tissue-culture cells in athymic rats for testing the efficacy of intrathecal therapy with transferrin-Pseudomonas exotoxin A (Tfn-PE) immunotoxin. An injection of 5 x 10(5) LOX cells into the intrathecal space through an indwelling catheter resulted in the reproducible development of lower-extremity paraplegia at 9.24 +/- 1.77 days because of focal deposits of tumor growth adjacent to the thoracic and lumbar spinal cord. A dose of 2.5 or 5 micrograms of intrathecal Tfn-PE immunotoxin was neurotoxic and resulted in the deaths of 8 of 10 animals within 24 hours. Histological evidence of central nervous system damage was seen as hemorrhagic degeneration around the central canal or a pathological cleft at the level of the cervical spinal cord. Because no neurotoxicity was seen with 1 microgram of intrathecal Tfn-PE immunotoxin, this dose was administered in treatment experiments. Twenty-four hours after the intrathecal instillation of LOX cells, 10 animals received intrathecally either 1 microgram of Tfn-PE or phosphate-buffered saline with 0.1% human serum albumin (control group).(ABSTRACT TRUNCATED AT 250 WORDS)

ADP Ribose Transferases↗
PubMed1994

Hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber disease) presenting with polymicrobial brain abscess. Case report.

A 26-year-old man presented with expressive aphasia, weakness of the right arm, and anemia but there was no family history of hereditary hemorrhagic telangiectasia. Computerized tomography (CT) of the head demonstrated an enhancing left frontal mass, which was aspirated and on culture yielded multiple organisms. Pulmonary arteriovenous fistulae identified in both lungs by chest radiography, CT, and angiography were treated with coil embolization. Treatment of pulmonary arteriovenous fistulae and prolonged surveillance are necessary to prevent future neurological complications.

Adult↗
PubMed1994

Central neurocytoma. Diagnosis and treatment.

Central neurocytoma is a rare intraventricular brain tumor that affects young adults and presents with nonspecific signs and symptoms. This distinct clinicopathological entity has a benign biological behavior with good prognosis following surgical intervention. Two cases of central neurocytoma are presented and the diagnosis and treatment discussed.

Adult↗
PubMed1994

Radiologic diagnosis, staging, and follow-up of adult central nervous system primary malignant glioma.

Glioma represents the most common primary intra-axial brain tumor. Currently, magnetic resonance (MR) imaging is the study of choice for the radiographic evaluation of patients with primary central nervous system glioma prior to and following therapeutic intervention. Computed tomography and MR imaging are frequently used for stereotactic biopsy and mapping. MR spectroscopy and/or thallium-201 single photon emission computed tomography may prove helpful in differentiating recurrent malignancy from radiation-induced necrosis.

Adolescent↗
PubMed1993

The spatial distribution of immunotoxins in solid tumors: assessment by quantitative autoradiography.

The spatial distribution of i.v. administered immunotoxins in s.c. human rhabdomyosarcoma RD2 xenografts was studied. The toxin and immunotoxins were: (a) diphtheria toxin (DT); (b) a binding-deficient form of DT (CRM107) linked to a monoclonal IgG1 antibody (454A12) directed against the human transferrin receptor (454A12-107); (c) the binding-deficient form of DT linked to the Fab' fragment of 454A12 (Fab'-107); and (d) the binding-deficient form of DT coupled to MOPC21, a monoclonal IgG1 with no significant binding to RD2 cells. DT and the immunotoxins were radiolabeled with 125I and injected via the tail vein into tumor-bearing athymic mice (median tumor weight, 0.25 g). Tumors were removed 2, 6, and 24 h after injection of DT or immunotoxin. Film images of 20-microns frozen sections were digitized by video microscopy, and gray levels were converted to tissue concentrations based upon the film response to radioactivity standards and the specific activity of the radiolabeled toxins. Images of the tumors were characterized quantitatively by the kurtosis and the area above threshold; the kurtosis is a measure of the spatial heterogeneity of the radiolabeled immunotoxins, and the area above threshold is defined here as the fractional tumor area that reaches or exceeds 1.5% of the initial plasma concentration. The spatial distribution of DT in the tumors was extremely uniform, characterized by low kurtosis values. In contrast, the autoradiograms of 454A12-107 were punctate in appearance and were characterized by very high kurtosis values. Fab'-107, which has approximately one-half the molecular weight of the intact immunotoxin and binds only monovalently, also produced punctate images with kurtosis values similar to those for 454A12-107. The nonbinding immunotoxin distributed somewhat less uniformly than DT but much more homogeneously than either of the binding immunotoxins. DT, 454A12-107, and Fab'-107 have similar affinities for their respective receptors, but the concentration of binding sites for DT on RD2 cells (<3,000 receptors/cell) is much lower than the concentration of transferrin receptor (60,000 receptors/cell). Thus, the heterogeneous distribution of 454A12-107 and Fab'-107 probably reflects retarded penetration due to binding to the tumor cells. The area above threshold was greatest for DT and lowest for 454A12-107; the fragment and nonbinding immunotoxins had intermediate values. The lower area above threshold for the nonbinding immunotoxin as compared with DT may be due to the considerably large molecular weight and hence the lower capillary permeability and diffusion coefficient of the immunotoxin.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Managing the early discharge experience: taking control.

The purpose of this study was to understand women's experiences in an early discharge programme. Using grounded theory, the investigator collected, coded, compared and contrasted data gathered in unstructured interviews with eight women. The women managed their early discharge experience, first, by taking control of their antenatal and intrapartal care once they were accepted into the programme and, later, by taking control of their postpartum recovery and their infants' care. Taking control was influenced by the women's beliefs about family and home; their personalities, e.g. their ability to accept help; and their available support. Their beliefs, personalities and available support were central to their motivation to participate in the early discharge programme and to their perception of a successful experience. The women used a number of strategies to take control. These strategies emerged during organizing antepartal requirements, meeting their own expectations during labour and birth, and learning to trust their abilities to manage self-care and parenting postpartum. The women anticipated their increased family involvement, family integration and participation in decision-making. They did not, however, anticipate their increased feelings of confidence and competence. Taking control has implications for health professionals who are working with childbearing women experiencing early discharge.

Adaptation, Psychological↗