Biomedical subjects

E K Fram

Publications and source records attributed to E K Fram.

At least 37 records · Page 2Linked to original sources

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↗

PubMed1988

Aqueductal stenosis: evaluation with gradient-echo rapid MR imaging.

To assess the utility of gradient echo (GRE) magnetic resonance (MR) imaging in documenting aqueductal patency, spin-echo (SE) and GRE axial images were obtained with a 1.5-T system in 26 patients with aqueductal or periaqueductal lesions and in 26 control subjects. All SE images with a long repetition time (TR) were obtained with first-order gradient moment nulling. GRE imaging was performed with the use of the sequential section acquisition technique called gradient recalled acquisition in the steady state (GRASS), with a TR of 150 msec, an echo time of 14-17 msec, and a flip angle of 50 degrees, so to depict stationary cerebrospinal fluid (CSF) as low intensity and flowing CSF as high intensity. All patent aqueducts were seen as high intensity on GRE images. In 18 of 20 obstructed aqueducts, low intensity was seen within the aqueducts on GRE images. SE images obtained with gradient moment nulling did not allow confident distinction between patent and obstructed aqueducts. It appears that GRE imaging is useful in rapidly assessing aqueductal patency.

Cerebral Aqueduct↗

PubMed1988

Vascular intracranial lesions: applications of gradient-echo MR imaging.

To investigate the role of the gradient-echo (GRE) technique in clinical intracranial magnetic resonance (MR) imaging, 63 patients with a variety of vascular intracranial lesions were examined at 1.5 T with the use of spin-echo (SE) and GRE sequences. In all cases, the sequential section acquisition technique called gradient recalled acquisition in the steady state (GRASS) was employed; a repetition time of 150-200 msec, an echo time of 13-16 msec, and a flip angle of 50 degrees-60 degrees were used to optimize the depiction of blood flow as high intensity and the depiction of stationary fluid as low intensity. In 61 of 63 cases, gradient moment nulling was utilized to compensate for first-order flow effects. Although GRE images rapidly demonstrated flow in vascular intracranial lesions as high intensity, the vascular nature of these lesions was also clearly evident on SE images in most cases. In some cases, GRE images can be used to clarify the vascular nature of a lesion or to characterize a neoplasm. Other applications include the detection of vascular thrombosis, occult vascular malformations, and hemorrhagic complications of vascular lesions.

Brain Neoplasms↗

PubMed1988

Comparison of [125I]HIPDm and [125I]iodoantipyrine in quantifying regional cerebral blood flow in rats.

We determined regional cerebral blood flow (rCBF) using [125I]HIPDm [N,N,N'-trimethyl-N'-(2-hydroxy-3-methyl-5-iodobenzyl)-1,3-propanediamin e] and [125I]iodoantipyrine autoradiography under control and pathologic conditions (hypercapnia [acidosis], hypocapnia [alkalosis], and disrupted blood-brain barrier) conditions in 35 rats. In control rats, HIPDm rCBF (indicator fractionation method, n = 5) was lower than the corresponding IAP rCBF (diffusible indicator method, n = 4), most notably in the infratentorial regions and subcortical nuclei. In hypercapnia, rCBF increased by 100% and 37% in the HIPDm (n = 5) and IAP (n = 5) groups, respectively. In hypocapnia, IAP rCBF (n = 4) decreased 34% but HIPDm rCBF (n = 4) did not change. Following disruption of the blood-brain barrier by intracarotid infusion of mannitol in eight rats, both radiotracers (HIPDm n = 4, IAP n = 4) showed decreased rCBF to regions of disruption as defined by trypan blue extravasation. Our work indicates that modeling HIPDm uptake to quantify rCBF using the indicator fractionation method will underestimate blood flow and that HIPDm kinetics are influenced by compartmental pH dynamics that will limit the accuracy of this method in quantifying rCBF in pathologic conditions.

Acidosis, Respiratory↗

PubMed1987

Rapid calculation of T1 using variable flip angle gradient refocused imaging.

We present a method for rapid measurement of T1 relaxation times using gradient refocused images at limited flip angles and short repetition times. This "variable nutation" techniques was investigated using a T1 phantom. There was a high correlation between measurements obtained with the variable nutation and partial saturation techniques. The ability of this method to create calculated T1 images is also demonstrated. We conclude that the variable nutation method may allow measurement of T1 relaxation times with a significant reduction in acquisition time compared to partial saturation techniques.

Humans↗

PubMed1987

Evaluation of steady and pulsatile flow with dynamic MRI using limited flip angles and gradient refocused echoes.

Magnetic resonance imaging sequences utilizing limited flip angles and gradient echoes yield rapid (less than 2 min) dynamic images of the cardiovascular system. These images contain both accurate anatomical and functional information. Using a gradient refocused acquisition in the steady state (GRASS) in the CINE mode, we studied the relationship between gradient echo signal intensity and velocity of steady and pulsatile flow in a phantom simulating medium to large vessels. Images were acquired on a 1.5 Tesla system (repetition time = 21 ms, echo time = 12 ms, flip angle = 30 degrees). Data from each pulse interval were sorted in 16 images. Signal intensities from flow tube lumina and surrounding stationary water jacket were used to calculate contrast ratios which were compared to velocity measurements made with electromagnetic (EM) flow probes outside the magnet room. During steady flow, signal intensity contrast ratios increased with increasing flow and in a 10 mm thick slice, reached a peak at 48 cm/s, and declined for velocities up to 90 cm/s. Changes in instantaneous velocity during pulsatile flow correlated well (r greater than .88) with signal intensity changes up to a maximum mean velocity of 17 cm/s. Total signal intensity from the lumen for an "R to R" interval correlated extremely well (r greater than .97) with mean pulsatile flow velocities up to 30 cm/s. The excellent correlation between gradient echo signal intensity and actual flow velocities suggests that this imaging sequence might be useful for evaluating normal and pathologic flow phenomena.

Blood Circulation↗

PubMed1987

Optimizing electrocardiograph electrode placement for cardiac-gated magnetic resonance imaging.

Electrocardiographs recorded in a magnetic field for cardiac-gating in magnetic resonance imaging (MRI) are complicated by blood flow-induced potentials. This study examines which lead of the standard 12-lead ECG maximizes the QRS while minimizing flow-induced interference. Twelve-lead ECGs were performed on normal volunteers (n = 9) and patients (n = 13) in and out of the bore of a 1.5 Tesla imaging magnet. The amplitude of the major flow-induced potentials was measured, and the vectors of largest induced potential and the QRS axis were plotted for each subject. ECGs obtained outside and inside the magnet were digitized and subtracted (in magnet ECG--out of magnet ECG = artifact ECG) and the peaks of the resultant curves measured. Superimposed potentials were largest in the early T wave and late S-T segment in leads I, II, V1, and V2, and smallest in III and AVF. A low-amplitude 7-to 10-Hz signal occurred in most leads. In the frontal plane, QRS axes and flow potential vectors were closely clustered. In the transverse plane, QRS axes generally followed leads V5 or V6, whereas the flow potential vectors followed leads V1, V2, or V3. The normal and patient groups did not differ. Although leads III and AVP showed the smallest superimposed potentials, V5, V6, or a left posterior chest lead may maximize QRS and reduce artifact most consistently. A 7- to 10-Hz frequency filter may help eliminate artifacts in some subjects.

Blood Flow Velocity↗

PubMed1986

Quantitative three-dimensional reconstruction and carbohydrate cytochemistry of rat nonciliated bronchiolar (Clara) cells.

We have employed three-dimensional reconstructions and cytochemistry to analyze nonciliated bronchiolar epithelial (Clara) cells from rat lungs. We identified a previously unreported ovoid granule type, which was characterized by its relative electron-lucency and eccentric electron-dense core. These electron-lucent granules were less common than electron-dense granules and were polarized toward the Golgi. They occupied 0.51% of the cell volume. Quantitative analysis of cell volume fractions showed the more numerous electron-dense granules to be polarized toward the air border; they occupied 2.5% of the cell volume. Periodic acid-thiocarbohydrazide-silver protein staining for hexose sugars indicated no differences between the granule types with regard to their carbohydrate content. Multivesicular bodies occupied 0.42% of total cell volume and were distinctly polarized toward the surface of the Golgi. Rod-shaped granules were present in 4 of the 6 reconstructed cells, ranging in number from 0 to 9 per cell. Nine apparent secretory events were seen in 6 cells and all appeared as exocytosis. We conclude that rat Clara cells contain at least 3 morphologically distinct granule types located in different volumes of the cell, and that exocytosis is the mode of secretion. The functional relationship between the ovoid granule types could include precursor-product lineage or different secretory products. We suggest that multivesicular bodies and light granules are stages in dark granule genesis.

Animals↗

PubMed1985

Three-dimensional reconstruction and quantitative analysis of rat lung type II cells: a computer-based study.

The three-dimensional structure of alveolar epithelial type II cells was imaged using a computer-based system designed for reconstruction and quantitative analysis of serially sectioned specimens. Six type II cells were reconstructed from serial ultrathin sections of lungs from two Sprague Dawley male rats and the results were compared to standard morphometric estimates of type II cell composition from five other Sprague Dawley male rats. A minor portion of the type II cell surface was in contact with the alveolar airspace while most of the cell surface was embedded in the alveolar septal interstitium. The type II cells contained multiple Golgi regions located close to the nucleus. Mitochondria formed a few branching filamentous networks extending throughout the cell. The reconstructed cells appeared to represent a homogeneous population having fractional volumes of intracellular organelles very similar to those found by morphometric techniques. The spatial distribution of secretory organelle volume suggests that the organization of this cell type reflects an ordered progression of secretory particle maturation which is consistent with earlier hypotheses of lamellar body assembly.

Animals↗

PubMed1985

Secretion of surfactant by rat alveolar type II cells: morphometric analysis and three-dimensional reconstruction.

Secretion of surfactant by alveolar type II cells occurs by exocytosis and is stimulated by several mechanical and hormonal mechanisms, including beta-agonists. We examined the morphological correlates of this process by electron microscopy and by three dimensional reconstructions of rat lung alveolar epithelial type II cells before and after isoproterenol stimulation. Male rats were given a dose of isoproterenol 2 hours prior to anesthesia. The lungs were fixed by intratracheal instillation and lung tissue was processed by methods designed to enhance the retention of saturated phospholipids. The type II cells were evaluated by transmission and scanning electron microscopy and morphometry of the type II cells was performed. Three dimensional reconstruction of secretory events at the alveolar air border was also done. We observed a dose dependent increase in elliptical cell-surface pores averaging 0.2 X 0.4 micron in size on the alveolar luminal side of type II cells. Most often these pores were surrounded by an elevated area lacking microvilli and overlying an area of granular cytoplasm. The pores observed were about half the average diameter of the lamellar bodies and a deformation of that spherical secretory organelle was seen frequently. We conclude these cell-surface pores represent the structures through which surfactant is released by type II cells. During the secretion of lamellar bodies, deformation may be imposed at the restriction of the surface pores. This deformation could be important in the transformation of the lamellar material from an intracellular storage site to its active role on the alveolar surface.

Animals↗

PubMed1984

CT assessment of the adult intrathoracic cross section of the trachea.

After phantom validation of the method, normal tracheal morphology of 25 women and 25 men was studied retrospectively at level 1, the thoracic inlet; level 2, the supracarinal level, and level 3, halfway between. In no case was the minimal cross-sectional area less than 68% of the maximum of the three levels. Areas at the same level were different depending on sex, but not on other body parameters, and so were the means of the three levels: 194 mm2 (SD 35) in women and 272 mm2 (SD 33) in men. Mean tracheal area correlated with mean tracheal diameter (r = 0.98). Average configuration of the trachea was sagittal at the thoracic inlet and transverse supracarinally. Absolute tracheal cross sections of less than 120 mm2 in women and 190 mm2 in men and relative values of less than two-thirds compared with other levels should suggest an abnormality. Although static and not in competition with functional tests, noninvasive CT area calculation may be useful in demonstrating and quantifying tracheal obstruction when mediastinal neoplasms are staged or as a complementary morphological test when ventilatory studies do not afford enough information to localize the lesion and to decide about treatment.

Adult↗

PubMed1983

Tracheal cross-sectional area in children: CT determination.

A computer method that calculates tracheal cross-sectional area by compensating for partial volume averaging was developed and validated in a study with phantoms. The program was then used to determine the tracheal cross-sectional area of 30 normal children who ranged in age from four months to 18 years. CT-derived cross sections were correlated with age, height, weight, and body-surface area, and they were compared with findings of published clinical and post-mortem studies. CT cross-sectional areas ranged from 20-275 mm2, varied by as much as 22% at the three different tracheal levels studied, and appeared to correlate most closely with body height. CT-derived tracheal cross-sectional areas are quite similar to those in published reports of postmortem and clinical studies. Measurement of tracheal cross section by CT may prove useful in quantitating tracheal compromise by intrinsic or extrinsic causes.

Adolescent↗

PubMed1983

Morphometric characteristics of cells in the alveolar region of mammalian lungs.

Morphometric procedures have been used to study the characteristics of cells in the alveolar region of the lungs of rats, dogs, baboons, and humans. Compared with the other species, human lungs were found to contain greater numbers of macrophages and to have larger alveolar type II, endothelial, and interstitial cells. The thickness of the interstitium and the pulmonary capillary endothelium were also significantly greater in the human lungs. These differences in human lung anatomy may be due to increased exposure to airborne pollutants and to tobacco smoke. Despite the above differences and the fact that there are large variations in size and functional characteristics of the lungs of these mammals, an overall striking similarity in characteristics of individual lung cells was found. The distribution of cells in alveolar tissue was remarkably constant between species as was the average volume and surface area of most cell types. Computer-aided three-dimensional reconstruction techniques were used to determine the spatial relationship of organelles in individual alveolar type II cells from rats. A three-dimensional reconstruction of cells permits quantification of number, size, surface area, and volume of subcellular organelles and correlations of their three-dimensional spatial relationships.

Animals↗

PubMed1983

Tracheal compression by mediastinal masses in children: CT evaluation.

Chest computed tomography (CT) was valuable in detecting extrinsic tracheal compression by mediastinal masses in two pediatric patients. This prompted an independent evaluation by CT of 14 children with masses involving the middle mediastinum and possible intrathoracic tracheal narrowing. Computer programs permit precise calculation of tracheal cross-sectional areas. Any apparent decrease in tracheal area may be compared with CT-derived data in normal children. Chest CT not only demonstrates the presence of extrinsic airway compression in pediatric patients with mediastinal masses, but also is capable of precisely measuring the extent of this narrowing. This method identifies children at potential risk for respiratory compromise and may aid in subsequent therapy.

Adolescent↗

PubMed1982

CT densitometry of pulmonary nodules: a phantom study.

Density determinations by computed tomography (CT) have been used to distinguish benign from malignant pulmonary nodules. Unfortunately, clinical scanning of pulmonary nodules frequently yields artifactually low CT numbers because of partial volume artifacts from the surrounding aerated lung. In order to determine the best performance that can be expected from a CT scanner in providing CT numbers for pulmonary nodules free of partial volume artifacts, we scanned a phantom containing plastic spheres surrounded by air to simulate nodules in aerated lung. The relations among size of the sphere, slice thickness (collimation), and centering of the CT slice critically affected the number of accurate voxel values. A simple computer model accurately duplicated the experimental findings. These data enable us to define the basic geometric requirements for accurate CT densitometry of pulmonary nodules.

Densitometry↗

PubMed1982

Distinguishing benign from malignant pulmonary nodules by computed tomography.

Investigators have been able to distinguish benign pulmonary nodules from malignant ones in about two-thirds of the cases studied by detecting high computed tomography (CT) numbers (attributed to microscopic calcifications) within many benign nodules. This paper reports a similar analysis on a series of 22 benign and 14 malignant pulmonary nodules. Although about one-third of the benign nodules gave high CT numbers, all but one of the nodules diagnosed as benign by CT could also be diagnosed by detection of calcification on plain radiographs or conventional tomograms.

Calcinosis↗

PubMed1982

Gated multiplanar cardiac computed tomography.

Multiplanar reformatting was combined with electrocardiographically gated computed tomography (CT) to provide a three-dimensional assessment of the beating heart of a live dog. Separate systolic and diastolic images were made in transverse, sagittal, coronal, and paraxial views. Three-dimensional contour images that outlined the cardiac chambers and the myocardium were then made using a separate research computer. This three-dimensional appreciation of cardiac morphology could be extended to assess regional function. Practical problems that limit the application of these methods are discussed, along with the proposed solutions.

Animals↗