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Biomedical subjects

E F Jackson

Publications and source records attributed to E F Jackson.

At least 19 recordsLinked to original sources
PubMed2003

Assessment of geometrical accuracy of magnetic resonance images for radiation therapy of lung cancers.

The purpose of this research was to investigate the geometrical accuracy of magnetic resonance (MR) images used in the radiation therapy treatment planning for lung cancer. In this study, the capability of MR imaging to acquire dynamic two-dimensional images was explored to access the motion of lung tumors. Due to a number of factors, including the use of a large field-of-view for the thorax, MR images are particularly subject to geometrical distortions caused by the inhomogeneity and gradient nonlinearity of the magnetic field. To quantify such distortions, we constructed a phantom, which approximated the dimensions of the upper thorax and included two air cavities. Evenly spaced vials containing contrast agent could be held in three directions with their cross-sections in the coronal, sagittal, and axial planes, respectively, within the air cavities. MR images of the phantom were acquired using fast spin echo (FSE) and fast gradient echo (fGRE) sequences. The positions of the vials according to their centers of mass were measured from the MR images and registered to the corresponding computed tomography images for comparison. Results showed the fGRE sequence exhibited no errors >2.0 mm in the sagittal and coronal planes, whereas the FSE sequence produced images with errors between 2.0 and 4.0 mm along the phantom's perimeter in the axial plane. On the basis of these results, the fGRE sequence was considered to be clinically acceptable in acquiring images in all sagittal and coronal planes tested. However, the spatial accuracy in periphery of the axial FSE images exceeded the acceptable criteria for the acquisition parameters used in this study.

Computer Simulation↗
PubMed2001

Radiation-induced morphologic changes in the rhesus monkey (Macaca mulatta) brain.

The right cerebral hemisphere of 24 rhesus monkeys scheduled for necropsy at the completion of another project were studied histopathologically 1-30 days after a single dose of 60Co-irradiation. Histopathologically, inflammation and gliosis consistently occurred at specific time points but varied in severity between individuals. Multifocal hemorrhage, edema, and an acute neutrophilic inflammatory response were observed initially whereas perivascular accumulations of lymphocytes were observed in specimens at the end of the study. Microglia/macrophages were most prominent during the first week after irradiation, whereas astrocytes were reactive throughout the observation period. The early clinical manifestations of the central nervous system (CNS), because of brain irradiation in humans, correspond temporally with acute vascular responses, acute and subacute inflammatory cell responses, and subacute demyelination and reactive astrocytic and microglial responses observed in the rhesus monkey. Initial responses of the CNS to gamma-irradiation may have potential implications for the development of radiation-induced late injury of the CNS.

Animals↗
PubMed2000

Brain volume in children with neurofibromatosis type 1: relation to neuropsychological status.

OBJECTIVE: To determine characteristics of brain morphology in children and adolescents with neurofibromatosis type 1 and relate these characteristics to neuropsychological functioning. BACKGROUND: Neurofibromatosis type 1 is associated with numerous CNS abnormalities and cognitive impairment. Abnormal high signal intensity visible on brain MRI, brain tumors, and macrocephaly are common. Research into links between neuroanatomic and cognitive features has been inconclusive. METHODS: Fifty-two children and adolescents with neurofibromatosis type 1 were compared with 19 control subjects on several quantitative neuroanatomic and neuropsychological measures. RESULTS: Total brain volume, especially gray matter, was significantly greater for neurofibromatosis type 1 subjects than the control subjects. Group differences in the ratio of gray matter to white matter were more prominent in younger than in older subjects. Volume of gray matter in the subjects with neurofibromatosis type 1 was related to their degree of learning disability. Corpus callosum size was significantly larger for subjects in the neurofibromatosis type 1 group, and diminished performance on measures of academic achievement and visual-spatial and motor skills were associated with greater regional corpus callosum size. CONCLUSIONS: Neuroanatomic morphology and the developmental pattern of gray matter and white matter in subjects with neurofibromatosis type 1 differed from in control subjects. Some of these differences are related to the neuropsychological status of the neurofibromatosis type 1 group. We propose that delayed developmental apoptosis results in macrocephaly and a delay in the development of appropriate neuronal connections in children with neurofibromatosis type 1. We further propose that these morphologic delays are related to the cognitive profile of neurofibromatosis type 1.

Adolescent↗
PubMed2000

Triple-dose contrast-enhanced images in neurologically symptomatic HIV-positive patients.

Our purpose was to determine whether triple-dose delayed contrast-enhanced images would improve lesion detection in patients with symptomatic human immunodeficiency virus (HIV) infection. We reviewed 33 MRI studies on 29 patients. Single-dose immediate T1-weighted spin-echo (1x-T1) images were compared with delayed triple-dose images (D3x-T1). Two neuroradiologists decided which technique showed more lesions, increased lesion conspicuity and/or altered the radiologic diagnosis. The D3x-T1 technique improved lesion detection in 14 of 29 patients (48%). In two patients (7%), the improvement changed the radiologic diagnosis by showing new meningeal lesions.

Adult↗
PubMed2000

Magnetic resonance imaging and magnetic resonance angiography before postchemotherapy retroperitoneal lymph node dissection.

OBJECTIVES: Retroperitoneal lymph node dissection (RPLND) after primary chemotherapy is an accepted therapeutic approach for metastatic nonseminomatous germ cell testicular cancer. Because of the intense desmoplastic reaction and adherence to venous and arterial walls, accurate imaging of the retroperitoneal vasculature and its relation to residual tumor is essential. We report our experience with magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA), including the recently developed technique of bolus-contrast MRA, in patients undergoing postchemotherapy RPLND. METHODS: Eighteen patients underwent MRI of the retroperitoneal region before RPLND. In addition to routine sequences, MRA was performed in 10 patients, including 8 with a three-dimensional technique using bolus intravenous MR contrast. Results were compared with intraoperative and pathologic findings. RESULTS: MRI and MRA provided detailed information on retroperitoneal vasculature and its relation to tumor, including multiple renal vessels (n = 5), duplex inferior vena cava (n = 1), left retroaortic renal vein (n = 2), and common iliac vein thrombus (n = 1). In all cases, bolus-contrast MRA provided unique information on the location and number of renal and lumbar arteries, in addition to information on the aorta and the mesenteric and iliac vessels. The origin and number of renal arteries were accurately identified in all patients by bolus-contrast MRA; 2 patients had supernumerary renal arteries discovered at RPLND that had not been identified on non-bolus-contrast MRI. CONCLUSIONS: Bolus-contrast three-dimensional MRA provides unique information on renal and lumbar vessels. The potential benefit of avoiding vascular injury during dissection should be prospectively evaluated.

Adult↗
PubMed2000

Quantitative morphology of the corpus callosum in children with neurofibromatosis and attention-deficit hyperactivity disorder.

Neurofibromatosis-1 is a common autosomal-dominant genetic disorder associated with numerous physical anomalies and an increased incidence of attention-deficit hyperactivity disorder (ADHD). Studies of children with idiopathic ADHD have suggested a link between corpus callosum size and symptom severity. This study examines the contribution of corpus callosum morphology to symptoms of ADHD in children with neurofibromatosis. Eighteen control subjects and 36 children with neurofibromatosis underwent magnetic resonance imaging of the brain. Twelve subjects with neurofibromatosis had evidence of ADHD and 24 did not. Subjects with neurofibromatosis had significantly larger total corpus callosum area and significantly larger regional measurements in three of seven areas. However, there were no differences between the neurofibromatosis alone and neurofibromatosis plus ADHD groups. Increased severity of attention problems was associated with smaller total callosal areas. These results suggest that some features of ADHD in children with neurofibromatosis could be linked to quantifiable differences in brain morphology, but the nature of the genetic mutation in neurofibromatosis suggests that neurochemical effects also could be important.

Adolescent↗
PubMed1998

Correlation between dynamic MRI and outcome in patients with malignant gliomas.

We assessed the correlation between dynamic MRI results and clinical outcomes in patients with malignant gliomas. Rapid serial MRIs were obtained after bolus injection of gadolinium that resulted in an initial fast uptake followed by a slow uptake of contrast. The maximum rate of uptake and delayed rate of uptake were correlated with survival and prognostic covariates such as age and histology. In 121 subjects, higher maximum uptake rates, 3.6 signal intensity units per second or greater, were associated with shorter survival (p = 0.0066). The correlation of delayed rate of uptake with survival was less significant. After adjusting for age, histology, and Karnofsky performance score, the maximum rate of uptake remained more significantly correlated with survival than the delayed rate of uptake. Thirty-one patients had surgery within 1 month of dynamic MRI, and those with glioblastoma multiforme or anaplastic gliomas had higher maximum rates of uptake than those with pure necrosis or mixed tumor and necrosis (p = 0.022). No correlation between delayed rate of uptake and histology was seen in this group of patients. Our results suggest that the maximum rate of uptake in dynamic MRI can be a prognostic measure for patients with malignant gliomas. Further prospective study is needed to assess the utility of this technique for evaluating brain tumors.

Adolescent↗
PubMed1998

The hippocampus: normal anatomy and pathology.

The hippocampus is a complex and fascinating region of the brain that has enormous clinical significance. Specifically, small imaging abnormalities may cause major symptoms. We believe that the detection of these lesions will be improved if imaging clinicians have an organized reference that facilitates identification of the cellular zones that comprise the hippocampus.

Adult↗
PubMed1997

A review of MRI pulse sequences and techniques in neuroimaging.

BACKGROUND: The unmatched soft tissue contrast provided by magnetic resonance imaging (MRI) has made it the modality of choice for many neuroimaging examinations. The fact that signal intensity in MRI depends on many parameters, including spin-lattice and spin-spin relaxation times, proton density, and velocity, makes it possible to highlight various pathologies by appropriate choice of pulse sequences and pulse sequence parameters. It is somewhat overwhelming however, to filter through various pulse sequences and parameters in order to understand how their selection affects image contrast. This brief review is intended to highlight common pulse sequences and parameters as well as introduce new techniques currently being released for clinical use. MATERIALS: Basic pulse sequences are described and the influence of the acquisition parameters on image contrast are illustrated. Such basic sequences include the ubiquitous spin echo, fast spin echo, and gradient echo sequences. Specialized techniques for fat suppression and magnetic resonance angiography are also presented. Currently approved contrast agents for use in MRI are briefly reviewed, and various advanced pulse sequences, such as those for diffusion and magnetization transfer contrast imaging, are briefly outlined. RESULTS: The utility of basic and advanced pulse sequences are demonstrated by clinical examples and images of normal brain and spine. New sequences and techniques are briefly outlined with regard to their potential for improving neuroimaging examinations. CONCLUSIONS: This brief review outlines how the choice of pulse sequence and acquisition parameters influences the resulting image contrast for a variety of basic and advanced imaging techniques.

Humans↗
PubMed1997

Introduction to hippocampal spectroscopy.

The use of MR spectroscopy to obtain nonivasive, in vivo biochemical information from the central nervous system might provide a powerful complement to the exquisite anatomic detail provided by MR imaging. This article briefly reviews current MR spectroscopy methodology and spectral analysis, introduces some of the recent applications of 1H and 31P MR spectroscopy of the brain, and discusses the applications of MR spectroscopy to the study of the anterior temporal lobe and hippocampus.

Aspartic Acid↗
PubMed1997

Magnetic resonance imaging of the central nervous system of the rhesus monkey.

The purpose of the study reported here was to document the ability of magnetic resonance imaging to depict the imaging characteristics of normal structures within the central nervous system of adult rhesus monkeys. The head and the cervical and thoracic parts of the spinal cord of two rhesus monkeys were imaged in a clinical 1.5-T whole-body imager. Specific images were selected, and some notable structures were identified. Results of this study document the usefulness of MRI as an expeditious, noninvasive research and diagnostic imaging technique and illustrates the normal magnetic resonance signal patterns of the brain and spinal cord in rhesus monkeys.

Animals↗
PubMed1996

Neuropsychological significance of areas of high signal intensity on brain MRIs of children with neurofibromatosis.

Of children with neurofibromatosis (NF), 40% have a cognitive or learning impairment. Approximately 60% also have anomalous areas of high signal intensity on T2-weighted brain MRIs. The association of these hyperintensities and neuropsychological status is not fully understood. We administered a battery of neuropsychological tests and a standard clinical MRI to determine the impact of hyperintensity presence, number, and location on cognitive status in 84 children (8 to 16 years) with NF type 1. These children underwent standard clinical MRI using a GE 1.5-tesla scanner (except one child who was examined with a 1.0-tesla scanner). We conducted three types of analyses: Hyperintensity presence or absence.-Scores of children with (55%) and without hyperintensities (45%) were compared using t tests. No statistically significant differences between groups in intellectual functioning or any neuropsychological variable were found. Number of hyperintensities-The number of hyperintensity locations per child ranged from one to five (mean = 2.22). Pearson correlations revealed no significant association between the number of hyperintensities and neuropsychological performance. Location of hyperintensities-In four of the five locations studied, no statistically significant differences were found between scores of children with a hyperintensity in an area and those with one elsewhere. However, mean scores for IQ, Memory, Motor, Distractibility, and Attention domains for children with hyperintensities in the thalamus were significantly lower than scores for those with hyperintensities elsewhere. These results suggest that the simple presence or absence of hyperintensities, or their total number, is not as important as their anatomic location for detecting their relationship with neuropsychological status. Taking location into account, hyperintensities in the cerebral hemispheres, basal ganglia, brainstem, or cerebellum seem to have no impact on neuropsychological functioning, whereas hyperintensities in the thalamus do.

Adolescent↗
PubMed1995

Soft-tissue sarcoma of the extremities. MR appearance of post-treatment changes and local recurrences.

MR imaging has the potential to provide valuable insights into intratumoral changes following preoperative therapy and has proven beneficial in the diagnosis of recurrent soft-tissue sarcoma of the extremities and differentiation of recurrence from postsurgical/postradiation changes. As advances occur in surgical and adjuvant treatment programs, further refinements of qualitative and quantitative MR imaging parameters should continue to enhance the role of MR imaging in the post-treatment evaluation of patients with soft-tissue sarcoma of the extremities.

Chemotherapy, Adjuvant↗
PubMed1994

Current imaging techniques for the evaluation of brain neoplasms.

The purpose of this article is to discuss the current imaging approaches and new techniques that have been developed in the examination and management of the patient with a brain neoplasm. These approaches and techniques include 1) functional imaging, perfusion, diffusion, localization of task activation, and dynamic circulatory changes; 2) three-dimensional imaging and techniques for tissue segmentation, surgical planning, and treatment planning; 3) positron emission tomography and single photon emission computed tomography, brain tumor diagnosis, and separation of brain tumor from radiation necrosis; 4) in vivo magnetic resonance spectroscopy, brain tumor differentiation and grading, and evaluation of the effects of therapy; and 5) future directions in the evaluation of brain neoplasms.

Brain Neoplasms↗
PubMed1993

Proton magnetic resonance imaging and spectroscopic studies of the pathogenesis and treatment of juvenile dermatomyositis.

Juvenile dermatomyositis is an inflammatory disorder of muscle, skin, and connective tissue. Immune vasculopathy is central to the pathophysiology. We studied a 13-year-old boy with juvenile dermatomyositis using proton magnetic resonance imaging (MRI) with short tau inversion recovery (STIR), and proton magnetic resonance spectroscopy (MRS) to quantitate lipid and water in affected regions of muscle. Tissue perfusion was assessed by measuring tissue water concentration changes during isometric exercise of the tibialis anterior muscle. During sequential studies over 3 months of steroid treatment, STIR image abnormalities, resting water concentrations, and diminished perfusion returned to normal. Resting lipid concentrations increased during this period. MRI serves to guide muscle biopsy and monitor progress of the disease state. MRS demonstrates the vasculopathy and provides noninvasive assessment of steroid therapy in juvenile dermatomyositis.

Adolescent↗