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Biomedical subjects

E K Fram

Publications and source records attributed to E K Fram.

At least 19 recordsLinked to original sources
PubMed1998

Differentiating recurrent tumor from radiation necrosis: time for re-evaluation of positron emission tomography?

UNLABELLED: Our purpose was to evaluate the ability of FDG PET to differentiate recurrent tumor from posttherapy radiation necrosis. METHODS: MR images, PET scans, and medical records of 84 consecutive patients with a history of a treated intracranial neoplasm were evaluated retrospectively. In all patients, recurrent tumor or radiation necrosis was suggested by clinical or MR findings. Metabolic activity of the PET abnormality was compared qualitatively with normal contralateral gray and white matter. RESULTS: PET findings were confirmed histologically in 31 patients. With contralateral white matter as the standard of comparison, the PET scan sensitivity and specificity were found to be 86% and 22%, respectively. With contralateral gray matter as the reference standard, the sensitivity and specificity became 73% and 56%, respectively. Overall, nearly one third of the patients would have been treated inappropriately in either scheme had the PET scan been the sole determinant of therapy. CONCLUSION: Our data suggest that the ability of FDG PET to differentiate recurrent tumor from radiation necrosis is limited. Both false-positive and false-negative PET scan results contributed to unacceptably low sensitivity and specificity values.

Diagnosis, Differential↗
PubMed1997

The variable MR appearance of primary lymphoma of the central nervous system: comparison with histopathologic features.

PURPOSE: To describe the MR features of primary central nervous system (CNS) lymphoma and to determine whether there is a correlation with histopathologic findings. METHODS: The MR images, pathologic specimens, and clinical records of 23 patients with primary CNS lymphoma were reviewed. The imaging and pathologic characteristics were tabulated and compared by using the standard tests for association in a two-dimensional contingency table. RESULTS: A total of 61 lesions were present in 23 patients; 12 patients (52%) had multiple lesions. All lesions were isointense or hypointense on T1-weighted images, and 53% were isointense or hypointense on T2-weighted images. Twenty patients received intravenous contrast material, and 43 (91%) of 47 lesions enhanced. The three patients who had nonenhancing lesions received steroids before the initial MR studies. Enhancement patterns differed between the immunocompetent and the immunocompromised hosts, with the latter group harboring a higher percentage of rim-enhancing lesions. Twenty-seven (44%) of the lesions were centered in a cerebral hemisphere and 14 (23%) were centered in the central gray matter. There was a statistically significant correlation between a higher degree of necrosis histologically and hyperintensity on T2-weighted MR images. The degree of necrosis also showed a positive correlation with rim enhancement. CONCLUSIONS: Primary CNS lymphoma has a variable MR appearance that correlates with the severity of intratumoral necrosis. These imaging characteristics, as well as lesion location, mean lesion size, and proclivity to harbor necrosis, are altered in the immunocompromised host.

Adult↗
PubMed1996

An alternative to GRASE: toward spin-echo-like contrast with independent reconstruction of gradient-echo images.

Multiple gradient echoes are generated for each RF echo of a Carr-Purcell-Meiboom-Gill (CPMG) train. Independently, phase-encoded fast spin-echo images are obtained from the different gradient echoes. Presently, three images are formed from three gradient-echoes from each of four RF echoes. The two peripheral gradient echo images are encoded for a late effective TE, then summed after reconstruction: this image has decreased fat intensity and increased susceptibility contrast compared with fast spin echo. The central gradient echoes yielded another image of intermediate contrast useful for neuroimaging. Raw data from the variously timed gradient echoes are not combined as they are in GRASE.

Brain↗
PubMed1995

A Nyquist modulated echo-to-view mapping scheme for fast spin-echo imaging.

A new scheme for assignment of echoes to views in fast spin-echo imaging was developed. The scheme places early and late echoes in alternating lines of the periphery of k-space; continued alternation of echoes arising closer to the middle of the echo train encodes the central portion of k-space. The scheme has two effects: a) The echo-to-echo signal decay that usually gives rise to multiple faint ghosts, now yields a single Nyquist ghost that is removed by phase over-sampling. b) Mapping earlier echoes (and thus more energy) to the periphery of k-space yields sharper edges.

Humans↗
PubMed1995

Transient resolution of bilateral tremor after unilateral thalamotomy, associated with focal injury of the corpus callosum: case report.

We present a patient with Parkinson's disease whose bilateral tremor transiently resolved after a unilateral left ventrolateral thalamotomy. The transient resolution of the bilateral tremor was associated with a focal thalamic lesion and a second lesion in the corpus callosum. The mechanism of this phenomenon may be related to temporary disruption of descending bilateral corticostriate projections by the callosal lesion.

Corpus Callosum↗
PubMed1994

Neurologic complications of cerebral angiography.

PURPOSE: To examine the incidence of neurologic complications associated with modern cerebral angiography and to assess patient characteristics associated with an increased risk of complications. METHODS: One thousand consecutive cerebral angiographic procedures were evaluated prospectively. Examinations were performed using transfemoral catheterization and film-screen methods. For purposes of this trial, a neurologic complication was defined as any new focal neurologic deficit or change in mental status occurring during the angiogram or within the following 24 hours. Patients were evaluated during and at the completion of angiography. Follow-up evaluations were performed on the day of and the day after angiography. RESULTS: There were a total of 10 neurologic complications within 24 hours of angiography, 5 of which were persistent. Onset of 5 of the deficits occurred during angiography, the other 5 (3 persistent) were delayed. All complications occurred in patients being evaluated for stroke/transient ischemic attack or (in one case) asymptomatic bruit. A higher average age, longer average procedure time, and greater volume of radiographic contrast was noted in these patients than in the study population. CONCLUSION: Cerebral angiography was associated with a 1% overall incidence of neurologic deficit and a 0.5% incidence of persistent deficit. All complications occurred in patients presenting with a history of stroke/transient ischemic accident or carotid bruit, which may reflect the difficulty of performing angiography in this population at risk for atherosclerotic changes.

Adolescent↗
PubMed1994

Evaluation of shared-view acquisition using repeated echoes (SHARE): a dual-echo fast spin-echo MR technique.

PURPOSE: To compare the clinical efficacy of a dual-echo fast spin-echo imaging technique, SHARE (share-view acquisition using repeated echoes), with conventional long-repetition-time spin-echo imaging. METHODS: Conventional spin-echo and SHARE fast spin-echo MR images of the brain were acquired in 50 randomized patients and interpreted separately in conjunction with the T1-weighted images. All images were reviewed independently by two neuroradiologists who were blinded to the clinical history and previous interpretations. RESULTS: The diagnoses rendered for the spin-echo and SHARE images were concordant in 48 of the 50 subjects (96%) by the first reader and in all 50 cases (100%) by the second reader. SHARE images were acquired in one-fourth of the imaging time yet image contrast, quality, and sensitivity to long T2 lesions were comparable. The SHARE technique was less sensitive to hemorrhagic residua. CONCLUSIONS: SHARE is a viable time-saving alternative to the conventional long-repetition-time pulse sequence. Although SHARE images are not as sensitive to magnetic susceptibility effects, the time saved using this technique could be used to perform a gradient-echo sequence when indicated.

Adolescent↗
PubMed1993

Recycling of surfactant lipid and apoprotein-A studied by electron microscopic autoradiography.

Recycling of lipid and apoprotein components by lung epithelium appears to be a key part of the metabolism of surfactant, but many details of this process are poorly understood, including its efficiency and which intracellular pathways participate. We chose electron microscopic autoradiography to track time-dependent changes in the intracellular location of [methyl-3H]-choline dipalmitoyl phosphatidylcholine or 125I-labeled apoprotein-A that were incorporated into liposomes and instilled intratracheally into rats or added to cultures of freshly isolated rat lung type II cells. At times from 2 to 120 min after the start of labeling, lungs or cells were fixed and processed for autoradiography. We found a time-dependent uptake of lipid and apoprotein by type II cells and by macrophages but not by other lung cell types. There was a time-dependent incorporation of lipid and apoprotein label into lamellar bodies, but the labels appeared in other intracellular compartments without a convincing time-dependent relationship to lamellar bodies. Although all type II cell organelles received some lipid-bound label, the apoprotein-bound label was not found within electron-dense multivesicular bodies (d-MVB). Selective lack of apoprotein label in d-MVB indicated a segregation of lipid and apoprotein labels and suggested a unique role for the d-MVB, possibly as a degradation pathway. Our results also provided conclusive morphological evidence of surfactant lipid and apoprotein recycling by type II cells.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

Carotid artery stenosis: clinical efficacy of two-dimensional time-of-flight MR angiography.

To assess the clinical efficacy of two-dimensional time-of-flight magnetic resonance (MR) angiography in the evaluation of carotid artery stenosis, a group of patients was evaluated in which 73 vessels were studied with both MR and conventional angiography. Four experienced neuroradiologists each scored both the MR and conventional angiograms in a blinded manner by using a standardized scoring scheme. Comparison of the scores revealed a high degree of correlation. In particular, MR angiography served to discriminate reliably between mildly narrowed and severely narrowed or occluded vessels. Furthermore, severe stenoses were accurately discriminated from occlusions in all cases. MR angiography is a robust and accurate modality for the characterization of carotid artery stenosis. It is useful in conjunction with routine MR imaging of the brain in the evaluation of the patient with suspected carotid arterial disease.

Carotid Arteries↗
PubMed1992

Intracranial vascular stenosis and occlusion: evaluation with three-dimensional time-of-flight MR angiography.

To assess the usefulness of magnetic resonance (MR) angiography in the characterization of intracranial arterial stenosis and occlusion, a three-dimensional time-of-flight method was compared with conventional angiography in 214 vessels in 29 patients. Studies were independently interpreted by two neuroradiologists who scored each vessel as normal, narrowed, or occluded. Overall, 97% of normal vessels and 100% of occlusions were correctly graded. Sixty-one percent of stenoses were graded correctly; the remainder were graded as normal. The portions of the intracranial vessels near the skull base and especially the paracavernous and supraclinoid segments of the internal carotid arteries were areas of frequent over- and underestimation of stenosis due to the presence of dephasing artifacts. In patients with stenosis or occlusion, MR angiography also provided information regarding the presence of collateral flow in the circle of Willis. When used in conjunction with MR imaging of the brain and MR angiography of the extracranial carotid arteries, intracranial MR angiography allows a more complete evaluation of the patient with symptoms of cerebral ischemia or infarction.

Adolescent↗
PubMed1991

Development of type II pneumocytes in rat lung.

At a late stage of fetal development, the mammalian alveolar epithelium undergoes an abrupt differentiation as a part of the preparation of the lung for the postnatal demands of gas exchange. Some of the most striking changes occur in the type II pneumocytes as they lose their glycogen and start to produce the lamellated inclusion granules that contain pulmonary surfactant. Premature birth before adequate type II cell maturation results in the neonatal respiratory distress syndrome, which is frequently fatal. We have used serial ultrathin sectioning, electron microscopy, and three-dimensional reconstructions to study the ultrastructural features of maturation of rat type II cells from a single rat each at age gestational day 20 through adult stages. We found evidence over this time span for compartmentation of several secretory granule precursors within type II cells. Changes in the polarization of lamellar bodies were observed over the time period studied. We also found marked gestational changes in the number and morphology of type II cell cytoplasmic processes that perforate the basement membrane. Type II cell mitochondria changed in shape during postnatal development from single, spherical to complex, branched structures. Volume composition obtained from serial sections of a small number of type II cells agreed closely with published morphometric data, indicating that throughout the animal's lifespan, type II cells are a homogenous population.

Aging↗
PubMed1990

Alveolar type II cell responses to chronic inhalation of chrysotile asbestos in rats.

The effects of chronic exposure to chrysotile asbestos on alveolar type II cells were examined in the lungs of Fischer 344 rats. Morphometric and three-dimensional analyses were used to characterize the alveolar type II cell and to determine the relationship of asbestos fiber localization to ultrastructural change in these cells. During the 2-yr period of study, type II cell number and volume increased to values more than 4 times those seen in controls. Ultrastructurally, cisternal dilations of the rough endoplasmic reticulum (RER) composed 12% of the total cell volume after 12 mo of exposure to asbestos and was still 15% of the total cell volume 1 yr after fiber exposure had ended compared to less than 1% in control cells. Asbestos fiber density surrounding these cells was directly proportional to the degree of cisternal dilatation in the cell; however, lamellar body volume and number in these cells were not different from that found in control type II cells. The incidence of a subset of type II cells with large lamellated inclusions was 10-fold greater in regions near bronchiolar-alveolar duct junctions, compared to more distal gas exchange regions of the lungs. Normal-sized lamellar bodies were fused to these large lamellated inclusions. These cells also contained significantly greater numbers of lamellar bodies and multivesicular bodies than those type II cells in more distal lung regions. These ultrastructural changes observed in type II cells may be a simple dose response to inhaled asbestos or the manifestation of two distinct populations of cells in the lungs that respond to asbestos in different ways. Asbestos fiber dose, cellular microenvironment, and aberrations of the cell plasma membrane and/or cell cytoskeleton (i.e., microtubules and filaments) are discussed as potential factors in the changes noted in type II cells.

Administration, Inhalation↗
PubMed1989

Septo-optic dysplasia: MR imaging.

Septo-optic dysplasia is the diagnosis when optic nerve hypoplasia is seen in conjunction with dysgenesis of the septum pellucidum. Nearly two-thirds of these patients have hypothalamic-pituitary dysfunction, and half have schizencephaly. The disorder is difficult to classify because of the diversity of clinical and pathologic manifestations. Magnetic resonance images of 11 patients with clinical and radiographic evidence of septo-optic dysplasia were reviewed retrospectively. The "syndrome" appears to include two subsets of patients whose abnormalities have different embryogenesis and neuropathologic findings. The existence of these two subsets helps to explain the diversity of the clinical and radiologic findings.

Adolescent↗
PubMed1989

MR angiography with two-dimensional acquisition and three-dimensional display. Work in progress.

Magnetic resonance arteriograms of healthy volunteers and selected patients were produced with a new spoiled gradient-echo pulse sequence based on time-of-flight phenomena. The procedure involves sequential acquisition of many contiguous, thin (1.5-mm) axial two-dimensional sections. These volume data are then submitted to a raytracing projection program, which retrospectively yields multiple arbitrary projection angles rotating through any plane. Venous structures are suppressed with a presaturation slab superior to the current section. The slab location is advanced in concert with advancement of each new section location. The acquisition time varies from 6 to 13 minutes, depending on the number of sections acquired for three-dimensional display. This method obviates the subtraction of image data sets to suppress signals from stationary spins, is more sensitive to slow blood flow than three-dimensional methods of acquisition, and shows special promise for the study of extracranial vascular disease.

Adult↗
PubMed1988

Effects of turbulence on signal intensity in gradient echo images.

Although the appearance of laminar vascular flow in magnetic resonance (MR) images has been characterized, there is no general agreement about the effect of turbulent flow on MR signal intensity. This study uses a fast scan gradient echo pulse sequence to evaluate nonpulsatile turbulent flow in two different models. The first model simulated flow in normal vascular structure. It generated nonpulsatile, laminar and turbulent flow in straight, smooth-walled Plexiglas tubes. The second model simulated flow through a vascular stenosis. It generated nonpulsatile, laminar, and turbulent flow through an orifice. Velocities and flow rates ranged from low physiologic to well above the physiologic range (velocity = .3 to 280 cm/second, flow rate from .15 to 40 L/minute). Transition from laminar to turbulent flow was observed with dye streams. Turbulent flow in straight, smooth-walled vessels was not associated with a decrease in MR signal intensity even at the highest velocities and flow rates studied. The transition from laminar to turbulent flow through an orifice is not associated with a decrease in gradient echo signal intensity. As the intensity of the turbulent flow increases, however, there is a threshold above which signal intensity decreases linearly as turbulence increases (r = .97). This study suggests that flow in normal vascular structures should not be associated with decreased signal intensity in gradient echo images. Turbulent flow through areas such as valves, valvular lesions or vascular stenoses, may be associated with a decrease in gradient echo signal intensity.

Blood Flow Velocity↗
PubMed1988

Microcomputer-based technique for 3-D reconstruction and volume measurement of computer tomographic images. Part 1: Phantom studies.

This paper presents a microcomputer-based technique that accurately quantifies volumes from computed tomographic (CT) scans of irregularly shaped objects as well as displaying 3-D reconstructions. The method uses standard CT film, allowing analysis of previous or outside CT studies. The planimetry method showed less than 5% error in measuring irregular 2-D areas larger than 6 mm2. The method is demonstrated to be significantly more accurate than spherical, ellipsoid, or rectangular geometric models in quantifying object volume by CT (P less than .001). With a single gantry angle, planimetry showed a two standard deviation error under 10% in measuring the volume of irregular objects compared with an error over 30% for ellipsoid models. The inaccuracy of the spherical model (80% error) and the rectangular prism model (192% error) renders them impractical to provide quantitative object volume. Microcomputer planimetry provides an accurate and versatile means to measure the volume and produce 3-D reconstructions of objects scanned with CT, and it has potential application in quantifying tumor response with CT and magnetic resonance imaging.

Humans↗
PubMed1988

Microcomputer-based technique for 3-D reconstruction and volume measurement of computed tomographic images. Part 2: Anaplastic primary brain tumors.

Serial computed tomography (CT) plays an integral part in monitoring effects of therapy for primary anaplastic brain tumors. Despite advances in CT technology, clinicians often cannot obtain accurate quantitative volume information to complement the qualitative assessment of tumor change. This paper presents a microcomputer-based method that provides both quantitative volume measurements and 3-D reconstructions of primary anaplastic brain tumors based on their hard copy CT or magnetic resonance imaging studies. The findings of this study demonstrate that planimetry is feasible for routine clinical use and is superior in accuracy to the spherical geometric model, which is shown to significantly overestimate tumor volume. The findings of 62 quantitative tumor studies (17 patients) showed a direct relationship between the total tumor volume and the volume of the hypodense intratumor core. There was no evidence of a relationship between the total tumor volume and the amount of peritumor low density (edema).

Astrocytoma↗