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R Felix

Publications and source records attributed to R Felix.

At least 469 records · Page 26Linked to original sources
PubMed1994

[The digital reprocessing of underexposed x-rays. Studies with a fluorescent light scanner].

Incorrect exposure of conventional radiographs frequently leads to repetition of the examination and thereby to increased radiation exposure for the patient. Underexposed films of an Alderson-Rando phantom, an ankle joint and a patella were digitised by means of an inexpensive fluorescent light scanner, and subsequent image manipulation improved quality so as to make the image diagnostically adequate. For the demonstration of markedly underexposed structures digitalisation with subsequent contrast enhancement was used. Well exposed structures are best evaluated in contrast enhanced transmitted light. Our results suggest it should be possible to reduce the number of repeat exposures and thereby to limit radiation exposure.

Ankle Joint↗
PubMed1994

[Communication and integration of medical documents for the teleconference use. An outcome of the BERMED project].

The collaboration between physicians is supported in the BERMED project by implementing the remote access to distributed patient data and the realisation of computer-based medical conferencing. This requires the integration of the multimedia data in form of a meta-patient record for our medical application systems. These applications are supported by a distributed information management promoting access to different information systems, imaging modalities and digital archival storage systems. The features of image processing are concerned with quantification, segmentation and 3-D-visualisation to obtain additional information. This paper gives an overview of the actual state of the teleconferencing system in radiology.

Computer Communication Networks↗
PubMed1994

[The spiral CT of orbital space-occupying lesions: improved imaging possibilities via freely reconstructible planes].

In a prospective study the value of spiral CT for the detection and differential diagnosis of intraorbital masses was investigated. Thirty patients with various orbital diseases were examined with transverse spiral computed tomography. After performing two contiguous 1 mm spiral CT scans, coronal, parasagittal, and other reconstructions were obtained. Compared with separately generated 2 mm slices, the 1 mm spiral CT images showed a slightly decreased signal-to-noise ratio, but due to the better spatial resolution, the image quality of secondary reconstructions was similar to that of the original transverse spiral CT slices. Generally the orbital masses were visualized best in the coronal reconstruction. In certain cases, the parasagittal reconstructions were superior. Reconstructions in freely definable slice planes based on 1 mm spirals provides better visualization of orbital diseases without increasing radiation dose. This method allows multiplanar reconstructions similar to magnetic resonance tomography.

Adolescent↗
PubMed1994

[The MRT of scaphoid pseudarthrosis with Gd-DTPA. Its staging and clinical correlation].

During a period of two years, 134 patients with pseudo-arthrosis of the scaphoid were examined by conventional radiography and by MRI in the course of a prospective study. The aim of the study was to define radiological staging using contrast enhanced MRI in order to improve the prognostic criteria. All MRI examinations were carried out with a 1.5 tesla scanner (SP63) using a surface coil and T1 weighted spin echo sequences in sagittal and frontal projection and frontal FLASH T2 sequences and axial spin echo T2 sequences. The T1 weighted SE sequences in frontal projection were carried out before and after iv contrast (0.1 mmol Gd-DTPA/kg KG). All sequences were compared with conventional radiographs and the operative findings. Eight patients in stage 0 showed high signal intensity of both fragments in T1 weighted SE sequences and at surgery there was good vascularisation. In 22 cases there was reduced signal intensity in at least one fragment (stage I). 45 patients with scaphoid pseudo-arthrosis showed complete signal loss but marked contrast uptake with still vital nuclei at surgery (stage II). In 22 patients, there was no increase in signal intensity after contrast and complete loss of vitality of the fragments at surgery. Staging was not possible in 37 patients because of previous operative intervention. The use of contrast enhanced MRI provides additional information compared with conventional radiography or plain MRI.

Adolescent↗
PubMed1994

[Cerebral arteriovenous angiomas: 3-dimensional demonstration by spiral CT].

In 20 patients with known or suspected supratentorial arteriovenous malformations, an attempt was made to see how far CT angiography with 3-dimensional reconstructions is able to make a diagnosis and to differentiate the various components of the angioma. Spiral CT was performed following an intravenous bolus injection of 60-80 ml of iodine containing contrast medium. In all patients the diagnosis was confirmed by intra-arterial DSA of the vertebral vessels. In 13 patients, av malformations could be diagnosed following multiplanar 3-D reconstructions which agreed with the findings on DSA. The large supplying vessels, the nidus and the large draining veins could be defined with certainty. In 6 patients follow-up examination after embolisation was performed. The results could be demonstrated in three dimensions and the success of treatment could be documented unequivocally. CT angiography with 3-D reconstruction is able to supply important information in the majority of intracranial av malformations, both during initial investigation and following treatment.

Adolescent↗
PubMed1994

Long-term regulation of calcium channels in clonal pituitary cells by epidermal growth factor, insulin, and glucocorticoids.

In rat pituitary GH3 cells, epidermal growth factor (EGF) and insulin stimulate prolactin production, whereas glucocorticoids exert the opposite effect. In the present study, GH3 cells were subjected to whole-cell patch clamp to assess the chronic actions of such regulatory factors on voltage-dependent calcium currents. Before the electrical recording, cells were grown 5-6 d either under standard conditions or in the presence of 5 nM EGF, 100 nM insulin, 1 microM dexamethasone or 5 microM cortisol. EGF induced a twofold selective increase in high-threshold calcium current density. Insulin and glucocorticoids, on the other hand, specifically regulated low-threshold Ca channels. Current density through these channels increased by 70% in insulin-treated cells, and decreased by 50% in cells exposed to dexamethasone or cortisol. Other Ca channel properties investigated (conductance-voltage curves, deactivation rates, time course and voltage dependence of low-threshold current inactivation) were unaffected by the chemical messengers. The alterations in current density persisted for many hours after removing the regulatory factors from the culture medium. In fact, the stimulatory action of EGF on high-threshold current lasted > 3 d. The results suggest that the control of prolactin production by the factors tested involves regulation of the surface density of functional Ca channels in the plasma membrane.

Animals↗
PubMed1994

Kallman syndrome versus idiopathic hypogonadotropic hypogonadism at MR imaging.

PURPOSE: To identify morphologic differences between Kallman syndrome (KS) and idiopathic hypogonadotropic hypogonadism (IHH) and establish a role for magnetic resonance (MR) imaging in these disorders. MATERIALS AND METHODS: Twenty-eight patients were compared with 10 eugonal male volunteers. Eighteen patients had KS (hypogonadotropic hypogonadism with anosmia) and 10 had IHH. All participants underwent hormone analysis, a sniff-bottle smell test, and gadolinium-enhanced MR imaging. Changes in the hypothalamic-hypophyseal region and the rhinencephalon were evaluated. RESULTS: MR imaging revealed intracranial morphologic changes in all patients on plain T1-weighted sections. Seventeen patients with KS demonstrated aplasia of an olfactory bulb; one olfactory sulcus was absent in six, rudimentary in four, and normal in eight. Olfactory bulbs were present in all 10 IHH patients and three showed one slightly hypoplastic bulb. Ten patients with KS and three with IHH showed an enlarged paranasal sinus system. Further MR findings were similar. CONCLUSION: MR imaging demonstrates abnormalities of the rhinencephalon present in KS patients and occasionally absent in IHH patients.

Adult↗
PubMed1994

Enlarged cervical lymph nodes at helical CT.

PURPOSE: To evaluate criteria for differentiating malignant versus reactive lymph nodes in the head and neck on the basis of findings at helical computed tomography (CT). MATERIALS AND METHODS: Helical CT scans were evaluated of 70 consecutive patients (46 men and 24 women, aged 20-78 years [mean, 51 years]) with known head and neck tumors and cervical lymph node enlargement. The ratio of the maximal longitudinal to the maximal axial diameter (L/T) was calculated for nodes larger than 8 mm in diameter based on measurements obtained from coronal, paraxial, and sagittal reconstructions. RESULTS: At histologic examination, 96 of 164 nodes were malignant. Of these, 94 of 96 nodes had an L/T of less than 2 (sensitivity, 97%; specificity, 97%; accuracy, 97% for malignancy). Minimal diameter was more than 8 mm in 83 of 96 nodes (sensitivity, 87%; specificity, 89%; accuracy, 88% for malignancy). Low-attenuation centers and rim enhancement were seen in 75 of 96 nodes (sensitivity, 78%; specificity, 100%; accuracy, 86% for malignancy). CONCLUSION: The L/T at helical CT provide an accurate assessment of reactive versus malignant nodes in the head and neck.

Adult↗
PubMed1994

Glomus tumors of the skull base: combined use of MR angiography and spin-echo imaging.

PURPOSE: To evaluate the use of magnetic resonance (MR) angiography in the diagnosis of glomus tumors of the skull base. MATERIALS AND METHODS: In 40 patients with pulsatile tinnitus, spin-echo (SE) images, single sections, and maximum intensity projections from gradient-echo sequences, including arterial MR angiography and MR venography, were evaluated for tumor detection. Interpretations by two independent observers were correlated with findings from histologic examination, digital subtraction angiography, computed tomography, and clinical follow-up. RESULTS: Glomus tumors were detected near the tympanic plexus (n = 8) and close to the superior (n = 8) and inferior (n = 1) ganglia of the vagus nerve. Sixteen of 18 proved tumors were detected with SE images alone. Although four high-lying jugular bulbs were misinterpreted as tumor due to similar signal intensity, combined evaluation allowed differentiation between tumor and sinusal blood flow in all cases. CONCLUSION: The authors recommend combined SE imaging and MR angiography for ruling out tumor in patients with pulsatile tinnitus.

Adult↗
PubMed1994

Role of colony stimulating factor-1 in the establishment and regulation of tissue macrophages during postnatal development of the mouse.

Colony stimulating factor-1 (CSF-1) regulates the survival, proliferation and differentiation of mononuclear phagocytes. The osteopetrotic (op/op) mutant mouse is devoid of CSF-1 due to an inactivating mutation in the CSF-1 gene and is deficient in several mononuclear phagocyte subpopulations. To analyze more fully the requirement for CSF-1 in the establishment and maintenance of mononuclear phagocytes, the postnatal development of cells bearing the macrophage marker antigens F4/80 and MOMA-1, in op/op mice and their normal (+/op or +/+) littermates, were studied during the first three months of life. In normal mice, maximum expression of tissue F4/80+ cells was generally correlated with the period of maximum organogenesis and/or cell turnover. Depending on the tissue, the F4/80+ cell density either decreased, transiently increased or gradually increased with age. In op/op mice, tissues that normally contain F4/80+ cells could be classified into those in which F4/80+ cells were absent and those in which the F4/80+ cell densities were either reduced, normal or initially normal then subsequently reduced. To assess which F4/80+ populations were regulated by circulating CSF-1 in normal mice, op/op mice in which the circulating CSF-1 concentration was restored to above normal levels by daily subcutaneous injection of human recombinant CSF-1 from day 3 were analyzed. These studies suggest that circulating CSF-1 exclusively regulates both the F4/80+ cells in the liver, spleen and kidney and the MOMA-1+ metallophilic macrophages in the spleen. Macrophages of the dermis, bladder, bone marrow and salivary gland, together with a subpopulation in the gut, were partially restored by circulating CSF-1, whereas macrophages of the muscle, tendon, periosteum, synovial membrane, adrenals and the macrophages intimately associated with the epithelia of the digestive tract, were not corrected by restoration of circulating CSF-1, suggesting that they are exclusively locally regulated by this growth factor. Langerhans cells, bone marrow monocytes and macrophages of the thymus and lymph nodes were not significantly affected by circulating CSF-1 nor decreased in op/op mice, consistent with their regulation by other growth factors. These results indicate that important differences exist among mononuclear phagocytes in their dependency on CSF-1 and the way in which CSF-1 is presented to them. They also suggest that the prevalent role of CSF-1 is to influence organogenesis and tissue turnover by stimulating the production of tissue macrophages with local trophic and/or scavenger (physiological) functions. Macrophages involved in inflammatory and immune (pathological) responses appear to be dependent on other factors for their ontogenesis and function.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1994

Dural sinus thrombosis: value of venous MR angiography for diagnosis and follow-up.

OBJECTIVE: The purpose of this study was to determine the value of venous MR angiography as the sole procedure for the diagnosis and follow-up of dural sinus thrombosis. MATERIALS AND METHODS: Forty-two patients with clinical findings suggestive of dural sinus thrombosis were examined with venous MR angiography and spin-echo MR imaging. Maximum-intensity-projection reconstructions and individual sections of the MR angiograms were examined for direct and indirect signs of dural sinus thrombosis by assessing flow signal from the major sinuses, the jugular bulb, upper jugular veins, ascending cortical veins (occlusion or increased flow due to formation of collaterals), diploe (emissary) veins and extracranial veins, and the deep subcortical veins (Galen's and internal cerebral veins). Direct signs of dural sinus thrombosis on MR angiograms included lack of typical high flow signal from a sinus that did not appear aplastic or hypoplastic on single sections from MR angiography and the frayed appearance of the flow signal from a sinus after recanalization. Indirect signs of dural sinus thrombosis included evidence of formation of collaterals, unusually prominent flow signal from deeper medullary veins, cerebral hemorrhage, visualization of emissary veins, and signs of increased intracranial pressure. When available, conventional angiograms were evaluated by analogous criteria as appropriate. Digital subtraction or cut-film angiograms were available for correlation in nine patients. In nine patients, MR angiography was repeated up to eight times during the course of follow-up. The results of MR angiography for all patients were compared with results in 10 control subjects. Confirmation of the diagnosis of dural sinus thrombosis was based either on conventional angiographic findings or on the changes seen in follow-up examinations. RESULTS: Dural sinus thrombosis could be ruled out in 25 of the 42 patients on the basis of clinical and MR angiographic findings. In 17 patients with MR angiographic findings that indicated dural sinus thrombosis, conventional angiography confirmed the diagnosis in nine patients, and changes seen on repeat MR angiograms during follow-up confirmed the diagnosis in nine patients as well (one patient's diagnosis was confirmed by both techniques). Individual frames from two-dimensional fast low-angle shot sequences allowed direct visualization of thrombus. Limited spin-echo sequences as performed here provided inconsistent findings and were insufficient for diagnosis. In the 10 control subjects, attenuation of flow signal was seen in the torcular Herophili in all studies; one subject had a nonpathologic variant of the sinojugular system. CONCLUSION: MR angiography is the technique of choice for diagnostic evaluation and follow-up of dural sinus thrombosis, and it is reliable as the sole examination for this condition. When MR angiographic findings are unremarkable and other abnormalities must be ruled out, routine spin-echo MR imaging should be performed.

Adult↗
PubMed1994

Diagnostic evaluation and surgical management of the aberrant right subclavian artery.

A case of dysphagia and dyspnea secondary to compression of the esophagus and the trachea by an aberrant right subclavian artery is presented. As the pathology of the aberrant right subclavian artery is extremely diverse, the diagnosis without radiologic investigation is hardly feasible. Conventional angiography of the aortic arch may be avoided by 3-dimensional magnetic resonance angiography, that is a suitable noninvasive method to diagnose and visualize the vascular pathology and the postoperative results after corrective vascular surgery. With the use of a Gore-Tex prosthesis the right aberrant subclavian artery was successfully translocated to the ascending aorta through a mid-sternal, transmediastinal approach. In contrast to previous reports the retro-esophageal vascular segment was kept in situ. The literature is reviewed with the reference to the diagnostic procedure and the treatment of dysphagia lusoria.

Adult↗
PubMed1994

[CT-morphologic aspects of the liver in patients with HIV infection].

CT examinations of the liver in HIV-infected patients show more frequent pathological findings. The extended spectrum of differential diagnosis and atypical manifestations of disorders in immunodeficient patients needs to be considered in the interpretation of CT scans. Difficulties in the differential diagnosis of focal hepatic lesions in HIV-infected patients are demonstrated in the following. Besides the relatively common findings in HIV-infection such as hepato-or hepatosplenomegalia, lymphoma, and inflammatory changes of the bowel an infection with Cryptococcus neoformans, hepatitis, and local steatosis of the liver are discussed as the rare causes for suspect computertomographic findings in the live of HIV-infected patients. The examinations were obtained consecutively in 76 HIV-infected patients during abdominal CT staging.

AIDS-Related Opportunistic Infections↗
PubMed1994

[Multiple sclerosis. Clinical topodiagnosis in comparison with cerebral MRI findings].

Clinicotopographic correlations were performed in a larger group of patients with multiple sclerosis (n = 121). In the assessment of two raters working independently from one another, 73% of all clinical brainstem findings (n = 74) could be traced back to demyelination plaques in the supposed localization as visualized by MRI. The clinical topodiagnostic was especially in accordance with MRI findings concerning internuclear ophthalmoplegia (85%) and abducens palsy (79%). Cerebellar dysfunctions (n = 60) correlated with morphological findings in 87%. More than half of all patients with cerebellar and brainstem symptoms exhibited a periventricular demyelination around the 4th ventricle which was associated with the clinical topodiagnostic. Unequivocal MRI correlations could be hardly found for clinical findings of low topodiagnostical value (symptoms of the long motor and sensory pathways). The clinical status as expressed by Kurtzke's EDSS reflects the extent of cerebral demyelination as seen by MRI only in a larger patient group.

Adolescent↗
PubMed1994

[Contrast medium enhanced MR angiography].

Magnetic resonance angiography (MRA) protocols are based on standard sequence protocols like time of flight MRA, which evaluates inflowing spins. This technique is limited by a variety of artifacts like the saturation artifact via turbulent blood flow. Contrast media diminish these artifacts like extracellular agents and blood-pool contrast media. The clinical value of the contrast-enhanced MRA for cerebral pathologies is based on the use of the paramagnetic contrast agent Gd-DTPA. For extracerebral diseases this technique is restricted because of the simultaneous visualization of both arterial and venous vascular territories. Occult venous sinus thrombosis or AV malformations are clinical essential indications for the use of C-MRA. Experimental data prove the excellent contrast abilities of blood-pool agents like Gd-DTPA-polylysin or Gd-DTPA-albumin, which demonstrate long intravascular persistence and retarded excretion.

Algorithms↗
PubMed1994

Dopamine D2 receptor imaging with iodine-123-iodobenzamide SPECT in idiopathic rotational torticollis.

UNLABELLED: The cause of idiopathic rotational torticollis (IRT) is not completely understood to date. However, basal ganglia are believed to be involved in the pathophysiology of IRT. To elucidate this disorder further, the value of iodobenzamide (IBZM) SPECT was studied for the evaluation of striatal dopamine D2 receptors in these patients. METHODS: Striatal dopamine D2 receptor density was assessed in 10 patients with IRT using 123I-IBZM SPECT. The images were interpreted by a nuclear medicine physician initially to determine IBZM binding within the striatum and the cerebellum and, secondly, interstriatal IBZM binding. The results were correlated with the clinical parameters of the patients and compared with the results obtained from normal controls. RESULTS: No difference was found in average, specific striatal IBZM binding (basal ganglia/cerebellum ratio) between patients and controls. However, interstriatal analysis of IBZM binding revealed a significantly higher binding in the striatum contralateral to the direction of the torticollis (p = 0.026, by chi-square test). CONCLUSION: It was concluded that the striatal dopamine D2 receptor status is altered in patients with IRT.

Adult↗