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Biomedical subjects

R Felix

Publications and source records attributed to R Felix.

At least 739 records · Page 41Linked to original sources
PubMed1985

Brain tumors: MR imaging with gadolinium-DTPA.

Magnetic resonance (MR) imaging was performed on 40 patients with intracranial tumors, before and after intravenous administration of gadolinium-DTPA (Gd-DTPA). Precontrast studies included a comprehensive protocol of spin-echo sequences. Tumors were visualized on precontrast images either directly or indirectly by anatomic distortion caused by the mass. However, differentiation of the tumor from adjacent tissues was possible in only 17 of 40 cases. Delineation of the tumor was best on precontrast, T2-weighted images. After administration of Gd-DTPA (0.1 mmol/kg), increased signal intensity from the tumor was observed in all patients. The localized increase in signal intensity in the tumor considerably improved the tumor delineation in 36 of 40 patients. Whereas most of the meningiomas, neuromas, and adenomas could be delineated prior to administration of contrast material if appropriate pulse sequences were applied, glioblastomas and intracranial metastases required Gd-DTPA administration for diagnostically sufficient tumor display.

Adenoma↗
PubMed1985

[Detection of regional hypertrophy in hypertrophic cardiomyopathy with ECG triggered nuclear magnetic resonance tomography--comparison with hypertensive patients and persons with healthy hearts].

Gated magnetic resonance tomography (MRT) was conducted in 40 patients (13 normal volunteers, 9 hypertensives and 18 patients with hypertrophic cardiomyopathy) using a 0.35 Tesla superconducting magnet. Multisectional spin echo imaging (35/400 msec) was obtained in coronal, transversal and sagittal planes. Myocardial wall thickness was measured in different segments and the three groups were compared to each other. 15/18 patients with hypertrophic cardiomyopathy (HCM) had asymmetrical regional thickening involving the septum and the anterior wall, in 8/15 the lateral wall was also hypertrophic. The distribution pattern in 3/15 patients with HCM was symmetric. Involvement of the right ventricle was found in 14/18 patients with HCM. There were significant differences (p less than 0.001) in wall thickness for the septal segment in all three groups and for the ratio septal to posterior wall between the HCM and the hypertensives and the normal volunteers. We conclude that MRT can differentiate HCM from hypertensives and normals, and is superior to echocardiographic imaging in the evaluation of the distribution of left ventricular hypertrophy in hypertrophic cardiomyopathy.

Adult↗
PubMed1985

[Modification of the image quality of i.v. DSA by the iodine concentration of the contrast medium].

In randomised, double-blind clinical trials it could be demonstrated that in iv. DSA the image quality is reduced if the iodine concentration of the nonionic contrast medium iopromide is higher than 370 mgI/ml, the total amount of injected iodine being constant. This effect is due to the increased viscosity of contrast media containing a high iodine concentration per ml solution. The increased viscosity produces a longer transit time of the contrast material from the injection site to the target region. Due to this effect there is an increased dilution of contrast material with blood.

Cerebral Angiography↗
PubMed1985

Fat as a factor affecting resolution in diagnostic ultrasound: possibilities for improving picture quality.

Fat and air are the main factors affecting quality by causing interference in ultrasound. Deterioration in resolution with increasing thickness of overlapping fat has been verified experimentally. The following factors have provided better resolution in experimental studies: large aperture transducers; compound technique (good axial resolution compensates for poor lateral resolution); compression of fat and location of the fat in the focus of the transducer; large beam width of the ultrasound signal. In a clinical study with 663 patients the influence of compression and compound technique on visualisation of abdominal structures was tested with a Combison 100 real-time scanner, Combison 202 compound scanner and the Octoson system. The retroperitoneal space was not demonstrated in 66 patients. Compression with the real-time transducer improved demonstration in 50% of studies (33/66), as compared to 20% (19/66) with the compound technique. Resolution was affected by velocity errors and reflection in 30% of cases (19/66) examined with the compound technique.

Adipose Tissue↗
PubMed1985

[Computed tomographic and nuclear spin tomographic diagnosis of brain tumors using conventional and paramagnetic contrast media].

52 patients with cerebral tumours were examined by both CT and MR. Contrast media containing iodine were used in CT, whereas in MR a paramagnetic contrast medium (gadolinium-DTPA) was applied by IV injection. A comparison of CT and MR findings showed that with both methods it was often not possible to achieve sufficient visualization and delineation of tumour tissue without employing a contrast medium. After application of the contrast medium, the shape and size contrast enhancement in the tumour tissue in both CT and MR was practically identical. This enables direct visualization of the tumour, superior delineation from the adjacent tissue, and differentiation between oedema and tumour, resulting in effective treatment planning which would otherwise not be possible.

Aged↗
PubMed1985

[Diagnosis of kidney diseases with magnetic resonance tomography including the use of nuclear magnetic resonance contrast media].

Magnetic resonance imaging of normal and pathological kidneys and the method of examination are demonstrated. The anatomy of the kidneys is excellently displayed by means of magnetic resonance imaging which can also distinguish between the renal cortex and renal medulla. Renal tumors and cysts can easily be recognized and differentiated by means of magnetic resonance imaging and the extension of the tumor (staging) can be defined. The principles of magnetic resonance imaging contrast media are described as well as the primary results obtained from administration of contrast media in volunteers. At the present time, ultrasound and computed tomography are the first imaging methods in recognition and differentiation of space occupying lesions of the kidneys. Magnetic resonance imaging should only be utilised in complicated cases, e.g. haemorrhagic cysts or when computed tomographic results show a suspected tumor invasion of the renal vein or tumor thrombus in the vena cava.

Diagnosis, Differential↗
PubMed1985

[Modification of the NMR-tomogram by blood flow].

Blood flow causes alterations of the NMR-Signal. Cross-sections of vessels will sometimes be imaged as dark spots, sometimes as highlighted areas. These highlightings of the lumen of vessels are often interpreted as caused by obstruction. In this paper the mechanisms of signal-intensity alterations as caused by blood flow will be described in order to prevent errors in interpreting of NMR-Images. The results of flow-measurements with the 0.35 Tesla imaging system in Berlin will also be presented. Finally, clinical examples of flow influence on images will be discussed.

Blood Flow Velocity↗
PubMed1985

[Intravascular rheologic changes following the administration of a contrast medium--animal experiment studies].

An angiographic animal study showed that hyperosmolar, ionic contrast media with a low viscosity produce the greatest increase in blood flow and the shortest diagnostically useful contrasting time of the vessels. The longest vessel contrast time and the smallest secondary increase in blood flow is seen for a nonionic, nearly isotonic contrast medium with a somewhat higher viscosity.

Angiography↗
PubMed1985

[Significance of magnetic resonance tomography in disseminated encephalomyelitis].

23 out of 24 patients with multiple sclerosis showed multiple, distinct lesions on investigation with cerebral nuclear magnetic resonance imaging (NMR). Arguments for the specific relationship of these lesions to demyelinating foci are: 1. Morphology and pattern of distribution agree to the known pathological observations. 2. Single lesions shown by computerized tomography (CT) were similarly located to lesions shown by NMR. The morphology and distribution of the lesions in the NMR show a common pattern largely independent of the individual neurological deficits. The nuclear magnetic resonance imaging is a method of high sensitivity and specificity for the diagnosis of multiple sclerosis. It offers valuable additional information in particular for early diagnosis and in cases of diagnostic uncertainty.

Adult↗
PubMed1984

Continuous aerosol inhalation scintigraphy in the evaluation of early and advanced airways obstruction.

By means of continuous lung imaging, regional mucociliary removal rates of inhaled 99mTc-labeled human serum albumin minimicrospheres were determined over upper, middle, lower, central, and peripheral anterior lung areas. Additionally, an index was employed for analysis of initial pulmonary radioaerosol distribution in order to quantify the site of particle deposition in various degrees of airways obstruction. The study involved 15 volunteer healthy subjects, 20 asymptomatic smokers with early small airways obstruction, and 30 patients with advanced chronic obstruction of large airways. The healthy group showed evenly distributed lung activity and (normal) clearance rates consistent with data from earlier work. While most uneven lung aerosol distribution was seen in the patients with large airways obstruction, slowest mucociliary clearance velocity was encountered in the smokers with small airways dysfunction. The aerosol technique, if carefully controlled, can be a useful supplement to pulmonary ventilatory function testing, showing reduction of bronchial mucous velocity to be one of the earliest signs of functional impairment in asymptomatic cigarette smokers.

Aerosols↗
PubMed1984

Magnetic resonance tomography (MRT) of intracranial tumours: initial experience with the use of the contrast medium Gadolinium-DTPA.

The present study provides an introduction to the clinical diagnosis of intracranial lesions by means of magnetic resonance tomography (MRT). The demonstration of different tissue qualities (bone and bone marrow, cerebral cortex and medulla, ventricular system (CSF), blood, tumour and perifocal oedema) in the MR tomogram is explained. The principles of specific MRT contrast media and their clinical application in brain tumours are discussed in detail.

Adult↗
PubMed1984

The subcellular distribution of [14C]dichloromethylenebisphosphonate and [14C]1-hydroxyethylidene-1,1-bisphosphonate in cultured calvaria cells.

Rat calvaria cells were cultured for 6 days in the presence or absence of [14C]dichloromethylenebisphosphonate [( 14C]Cl2MBP) or [14C]1-hydroxyethylidene-1, 1-bisphosphonate [( 14C]HEBP), after which cell organelles were separated by differential centrifugation. The distribution of protein, glutamate dehydrogenase, acid phosphatase, and 5'-nucleotidase was similar for cells treated or not treated with Cl2MBP. About 70-80% of the [14C]Cl2MBP and [14C]HEBP was found to be present in the supernatant. This was the only fraction that showed a ratio higher than 1 for the relative specific radioactivity, indicating that the bisphosphonates accumulated mainly in the cytosol. Rapid separation of particulate components and soluble cytoplasm of cells treated with [14C]Cl2MBP confirmed this finding, showing that it is unlikely that the result was due to leakage from the organelles. The uptake of [14C]Cl2MBP into cells was similar in different cell types. The binding of both bisphosphonates to macromolecules in the medium was 0.1-0.2% and 1-4% in the cells. This binding is not due to metabolic activity of the cells. About 15-20% of [14C]HEBP and [14C]Cl2MBP was modified by the living cells.

Acid Phosphatase↗
PubMed1984

Comparative study of deflazacort, a new synthetic corticosteroid, and dexamethasone on the synthesis of collagen in different rat bone cell populations and rabbit articular chondrocytes.

Deflazacort is a new synthetic glucocorticoid which is an oxazoline derivative of prednisolone. In previous studies, it was shown that deflazacort, depending on the test model used, not only showed considerably more antiinflammatory potency than prednisolone in animals but also caused less deleterious effects on bone mineral metabolism than equivalent amounts of other glucocorticoids in man. In this study, we have compared the effects of deflazacort with those of dexamethasone on the synthesis of collagen in various rat bone cell populations and chondrocytes. Three bone cell populations were prepared by sequential time-dependent collagenase treatment of 1-day-old rat calvaria. Each cell population was further purified on a Percoll gradient (10-90%) yielding three populations of which two are different in alkaline and acid phosphatase and response to parathyroid hormone. A 3-day treatment of bone cell populations with deflazacort and dexamethasone (10(-11)-10(-5) M) revealed that both glucocorticoids, although at different concentrations, inhibited collagen synthesis. 21-desacetyl-deflazacort (5 beta, 11 beta, 16 beta)-11,21-dihydroxy-2'-methyl-5-H-pregna-1-enol [17,16-d]oxazole-3,20-dione), the presumably active form of the steroid, which is formed in vivo after administration, produced nearly identical results as its precursor. Glucocorticoid concentrations at which inhibition was initially observed were 10(-9) M and 10(-7) M for dexamethasone and deflazacort respectively. Inhibition of collagen synthesis was significantly impaired only in cells isolated from bone during early tissue digestion, and not in those obtained during extensive collagenase treatment. Chondrocytes isolated from articular cartilage of 3-month-old rabbits and grown in primary cultures did not respond to either steroid.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Phosphatase↗
PubMed1984

[Noninvasive tomographic measurement of regional cerebral blood flow].

The measurement of the regional cerebral bloodflow by means of the dynamic single-photon-emission-computed tomography is a method of examination which is completely free of risk for the patient, causes no inconvenience and can be repeated whenever it seems necessary. This method gives a quantitative explanation for the distribution of the effective cerebral perfusion and can only be substituted by the very complicated positron-emission-computed tomography. As well as the exact assessment of the hemodynamic relevance of cerebral vascular disease, this method enables us to prove whether or not in various types of psychiatric disorders an interference in the regional perfusion exists. This method can also contribute to the clarification of pathogenic mechanisms, as well as to the nosological classification of specific psychopathological conditions.

Adult↗
PubMed1984

[Human testing of the nuclear spin tomographic contrast medium gadolinium-DTPA. Tolerance, contrast affect and the 1st clinical results].

In an initial clinical trial we examined the tolerance and the influence exercised on signals in nuclear magnetic resonance tomography by gadolinium-DTPA. In an open study, 4 dosages between 0.005 and 0.25 mmol Gd-DTPA/kg body-weight were tested on 5 healthy volunteers each. To ensure renal elimination of Gd-DTPA, NMR images were produced (0.35 T Magnetom) visualising the kidneys and urinary bladder before and more than 60 minutes after application of the contrast medium. The article shows in what manner the image is influenced by the dosage of the contrast medium and also by the time interval elapsing between injection of the contrast medium and production of the NMR tomogram. - Finally, first clinical results of NMR tomography contrast medium application are demonstrated in the case of 5 patients with cerebral tumours.

Adult↗