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Biomedical subjects

R Felix

Publications and source records attributed to R Felix.

At least 379 records · Page 21Linked to original sources
PubMed1996

Comparison of gadolinium-DTPA and macromolecular gadolinium-DTPA-polylysine for contrast-enhanced pulmonary time-of-flight magnetic resonance angiography.

RATIONALE AND OBJECTIVES: The authors investigated the enhancing effect of low-dose administration of the macromolecular, paramagnetic contrast medium gadolinium (Gd)-DTPA-polylysine (average molecular weight, 40,000-50,000 dalton [D]) compared with Gd-DTPA (molecular weight, 547 D) in time-of-flight magnetic resonance angiography of unilaterally damaged sheep lungs. MATERIALS AND METHODS: Thirteen heart-lung preparations were examined in the head coil of a 1.5-tesla imager (Magnetom SP, Siemens, Erlangen, Germany). The authors performed time-of-flight angiograms (coronal; repetition time, 35 mseconds; echo time, 6 mseconds; 20 degrees flip angle; pixel size 1.0 x 1.0 x 1.5 mm3) before and after application of the contrast agents. Gadolinium-DTPA-polylysine was used in a dose of 0.027 mmol/kg body weight while Gd-DTPA was injected in variable doses. RESULTS: After Gd-DTPA-polylysine, signal intensity increased by 118% in pulmonary arteries in healthy lungs and by 121% in damaged lungs (P < 0.001). In addition, the contrast-to-noise ratio measured between pulmonary arteries and perivascular parenchyma increased significantly (P < 0.01). On three-dimensional angiograms, two more generations of vascular branches could be detected. A dose of Gd-DTPA 6.1 times higher than the Gd-DTPA-polylysine dose was necessary to obtain the same contrast enhancing effect as Gd-DTPA-polylysine in healthy lungs. In damaged lungs, none of the administered doses of Gd-DTPA reached the average contrast enhancement of Gd-DTPA-polylysine. CONCLUSIONS: The authors' measurements demonstrate significant improvement of time-of-flight angiograms by low-dose administration of Gd-DTPA-polylysine.

Animals↗
PubMed1996

Magnetic resonance imaging of focal liver lesions. Comparison of the superparamagnetic iron oxide resovist versus gadolinium-DTPA in the same patient.

RATIONALE AND OBJECTIVES: The authors assess the efficacy of static and dynamic magnetic resonance (MR) imaging using the superparamagnetic iron oxide SHU-555A (Resovist) versus standard dose of gadolinium (Gd)-DTPA in patients with focal liver lesions. METHODS: Magnetic resonance imaging was performed in 30 patients suffering from histopathologically verified malignant (n = 22) and benign (n = 8) liver lesions. T2-weighted conventional and fat-suppressed as well as T1-weighted sequences were used before, during, and after fast intravenous administration of Resovist (1 mL/minute) at three doses of 4, 8, and 16 mumol/kg body weight. One week before the Resovist-enhanced MR imaging study 20 patients underwent Gd-DTPA-enhanced MR imaging. RESULTS: Detection rate was improved for metastatic lesions revealing 36 lesions unenhanced versus 53 focal lesions using Resovist-enhanced MR imaging. Gadolinium-DTPA-enhanced scans showed no additional lesion versus unenhanced and Resovist-enhanced MR imaging. Static and dynamic imaging demonstrated no measurable percentage signal intensity loss (PSIL) using Resovist-enhanced MR imaging versus a percentage enhancement of 79.7% in Gd-DTPA enhanced scans. In the dynamic T2-weighted sequences, hepatocellular carcinoma nodules (n = 4) showed a rapid decrease in signal intensity starting at 44 seconds. Postinfusion of Resovist followed by a low, constant increase in signal intensity. Gadolinium-DTPA enhanced scans showed a percentage enhancement of 73.4 focal nodular hyperplasia (FNH) and hemangioma revealed a strong and early dose-dependent PSIL 44 to 60 seconds postinfusion with a prolonged signal loss for the FNH in the late study. Statistical evaluation revealed a statistically significant superiority of Resovist-enhanced MR imaging concerning the detection and delineation of focal liver lesions compared with unenhanced and Gd-DTPA enhanced scans (P < 0.05). CONCLUSIONS: The fast infusion of the new superparamagnetic contrast agent Resovist shows advantages for dynamic and static MR imaging of focal liver lesions.

Carcinoma, Hepatocellular↗
PubMed1996

Fourier phase mapping of the human heart. The use of spatial modulation of magnetization cine magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Fourier phase mapping of cine cardiac magnetic resonance (MR) imaging offers noninvasive analysis of temporal cardiac activation patterns. The aim of our investigation was to extend this analysis to intramyocardial dynamics. METHODS: A fast-imaging with steady-state precision (FISP) two-dimensional gradient echo spatial modulation of magnetization (SPAMM) sequence and a segmented two-dimensional FISP-SPAMM sequence were applied to acquire cine MR images of the complete cardiac cycle on a 1.5-tesla imager. Signal intensity data were submitted to pixel-wise Fourier phase analysis. Color-encoded amplitude and phase maps were displayed for visual analysis. RESULTS: Using the unsegmented SPAMM two-dimensional FISP sequence, a more consistent tag-to-myocardium contrast and a higher number of cardiac phases was achieved than by using the segmented version of this sequence. The typical tag displacement reflected complex intramyocardial dynamics, including rotation. Phase mapping displayed a pattern of contraction consistent with electrophysiologic concepts of cardiac activation. In contrast, the segmented sequence did not reflect any differences in the onset of cardiac contraction, although tag displacement was apparent with this sequence as well. CONCLUSIONS. Fourier phase mapping of cardiac MR imaging tagging studies allows for noninvasive analysis of intramyocardial activation patterns. A temporal resolution of 50 mseconds per image at a heart rate of 75 beats per minute allows for an assessment of spatial differences in the onset of myocardial activation.

Adult↗
PubMed1996

Superparamagnetic iron oxide--enhanced versus gadolinium-enhanced MR imaging for differential diagnosis of focal liver lesions.

PURPOSE: To assess AMI-25- versus gadolinium-enhanced magnetic resonance (MR) imaging in the differential diagnosis of liver tumors. MATERIALS AND METHODS: Twenty-nine patients with liver tumors underwent unenhanced, AMI-25-enhanced (15 micromol/kg), and gadolinium-enhanced(0.1 mmol/kg) imaging within 2 weeks. RESULTS: A significant (P< .05) difference in percentage signal intensity loss (PSIL) was seen in benign tumors on AMI-25-enhanced proton-density-weighted images (nine focal nodular hyperplasia [FNH], 41%; one adenoma, 32.4%) versus malignant tumors. Gadolinium-enhanced T1-weighted gradient-echo images showed strong enhancement in benign lesions (seven FNH, 147.5%; one adenoma, 91.3%) and moderate enhancement in malignant tumors (eight hepatocellular carcinomas, 116.2%, 11 metastases, 39.7%). Receiver operating characteristic analysis revealed a threshold PSIL of 10% on AMI-25-enhanced images as the most essential criteria to distinguish benign from malignant lesions (sensitivity, 88%; specificity. 89%). Interobserver analysis for two observers revealed specificity of 93% for AMI-25-enhanced imaging versus 81.5% for gadolinium-enhanced MR imaging. CONCLUSION: AMI-25 decreased the SI of benign tumors and helped differentiate benign from malignant tumors.

Adenoma↗
PubMed1996

Liver tumors: comparison of MR imaging with Gd-EOB-DTPA and Gd-DTPA.

PURPOSE: To compare the usefulness of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) and gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) in the diagnosis of focal liver lesions. MATERIALS AND METHODS: Thirty-one patients with focal liver lesions underwent T2- and T1-weighted spin-echo magnetic resonance (MR) imaging and fast low-angle shot two-dimensional MR imaging before, during, and after intravenous administration of three different doses of Gd-EOB-DTPA (12.5, 25, and 50 mumol per kilogram body weight). Gd-DTPA-enhanced imaging (dose, 0.1 mmol per kilogram body weight) was performed in the same patients within 1 week of Gd-EOB-DTPA imaging. RESULTS: During the perfusion phase (the 3 minutes after injection of contrast material), the dynamic enhancement characteristics seen after injection of 25 and 50 mumol of Gd-EOB-DTPA were similar to those seen with Gd-DTPA. At the lowest dose of Gd-EOB-DTPA (12.5 mumol), the dynamic enhancement characteristics were not comparable to those seen with Gd-DTPA. During the hepatobiliary phase (1.5 minutes to 4 hours after injection), Gd-EOB-DTPA-enhanced images yielded a dose-independent, statistically significant improvement in the detection rate of additional metastases, hepatocellular carcinomas, and hemangiomas compared with unenhanced and Gd-DTPA-enhanced images (P < .05). CONCLUSION: Gd-EOB-DTPA-enhanced MR imaging enables improved detection of hepatic lesions over Gd-DTPA-enhanced MR imaging while providing comparable differential diagnostic information.

Adult↗
PubMed1996

Recent developments in the understanding of the pathophysiology of osteopetrosis.

Osteopetrosis is a rare metabolic bone disease characterized by a generalized increase in skeletal mass. It is inherited in a number of mammalian species, including man, and results from a congenital defect in the development or function of the osteoclasts. The consequent impairment of bone resorption prevents formation of bone marrow cavities, causes delayed or absent tooth eruption and results often in abnormally shaped bone. The pathogenetic defect may be intrinsic either to the osteoclast lineage or to the mesenchymal cells that constitute the microenvironment supporting the development and activation of the osteoclasts. In the first example, the disease can be cured by transplantation of hemopoietic cells. In some cases, bone marrow transplantation has also been successful in curing human osteopetrosis. This, together with the variability in the age of onset and severity of clinical aspects, suggests that a multiplicity of genetic mutations may cause the human disease. In recent years the genetic effects of some osteopetrotic mutations have been identified. This new information has been essential for the understanding of osteoclast biology. Colony stimulating factor 1 (CSF-1), the growth factor for cells of the mononuclear phagocytic system, is also essential for the development of osteoclasts. In the osteopetrotic (op) mouse, no biologically active CSF-1 is synthesized due to a point mutation in the coding region of its gene. This leads to an almost complete lack of osteoclast development and to impaired bone resorption. Altered CSF-1 production seems also to be involved in the toothless (tl) rat osteopetrosis. Recently, the mutation responsible for the microphthalmic (mi) mouse osteopetrosis has been identified in the gene encoding a member of the basic-helix-loop-helix-leucine zipper (bHLH-ZIP) protein family of transcription factors. The mi gene product seems to play a role in the fusion process of osteoclast precursor cells. Finally, osteopetrosis has been the result of experimental gene disruption in mice. Targeted disruption of the c-src proto-oncogene encoding a nonreceptor tyrosine kinase leads to a form of osteopetrosis where osteoclasts are present but inactive. This indicates that pp60c-src, localized primarily on ruffled border membranes and vacuoles of the osteoclasts, is important for osteoclastic function. Disruption of the c-fos proto-oncogene, a major component of the AP-1 transcription factor complex, leads to an osteopetrotic phenotype characterized by a complete absence of osteoclasts. The defect is intrinsic to hemopoietic precursors that are unable to progress beyond an early stage of osteoclast differentiation. In humans, deficiency of carbonic anhydrase II has been identified as the primary defect in the autosomal recessive syndrome of osteopetrosis with renal tubular acidosis and cerebral calcification. A lack of expression of the vacuolar proton pump has been observed in osteoclasts of a patient with craniometaphyseal dysplasia. In conclusion, the disease, although rare, is of great pathophysiological relevance for our understanding of the processes that govern the development and function of osteoclasts.

Animals↗
PubMed1996

Iodine-123-iodo-lisuride SPECT in Parkinson's disease.

UNLABELLED: Recently, [123I]iodo-lisuride was synthesized for possible applications in SPECT studies. The purpose of this investigation was to compare the striatal binding and kinetics of this radioligand in patients with Parkinson's disease and normal controls. METHODS: Six patients with Parkinson's disease and three normal controls were examined. After intravenous injection of 111 MBq [123I]iodo-lisuride, sequential SPECT examinations at 20, 40, 80 and 120 min were performed. For each SPECT series the basal ganglia-to-cerebellum ratio of tracer accumulation was calculated. In one patient a repeat SPECT examination was undertaken under identical conditions to test the reproducibility of the procedure. In two other patients a second SPECT examination was performed after injection of cold lisuride as a receptor saturation study. In addition, the time course of the radioactivity was measured in the plasma and red blood cells in each individual. RESULTS: In both patients and controls, the highest tracer accumulation was found within the striatum. The basal ganglia-to-cerebellum ratio was 1.182 and 1.303 at 20 min, 1.353 and 1.450 at 40 min, 1.490 and 1.533 at 80 min, 1.550 and 1.583 at 120 min for patients and controls, respectively, which was not statistically different. In the saturation study, 50 micrograms and 100 micrograms cold lisuride led to a 28% and 33% reduction, respectively, of the basal ganglia-to-cerebellum ratio at 120 min. The ligand showed a rapid decline in plasma and red blood cells. The percent injected dose per liter was calculated to be 1.6 and 0.9, respectively, for plasma and red blood cells at 20 min. CONCLUSION: Iodine-123-iodo-lisuride SPECT seems useful for imaging intact striatal dopamine D2 receptors in patients with Parkinson's disease and may provide clinically relevant information for quantitative assessment of the availability and integrity of dopamine D2 receptors.

Adult↗
PubMed1996

[Cerebral SPECT with iodine-123 IBZM in patients with extrapyramidal system disorders: the evaluation of its sensitivity in therapy with dopaminergic drugs].

The functional integrity of striatal post-synaptic dopamine D2 receptors is requested for an effective pharmacologic treatment in patients with extrapyramidal movement disorders. Iodine-123 IBZM Single Photon Emission Computed Tomography (SPECT) is a noninvasive radionuclide technique for the morpho-functional imaging of post-synaptic dopamine D2 receptors. In this study, the results of iodine-123 IBZM SPECT and those of apomorphine tests were compared in 32 patients with extrapyramidal movement disorders--22 patients with idiopathic Parkinson's disease (IPD) and 10 with Parkinson's plus syndrome (PPS). Iodine-123 IBZM uptake was measured as the ratio between striatum and frontal cortex activities. Twenty of 22 IPD patients (91%) responded to apomorphine administration, while in 8 of 10 PPS patients (80%) the apomorphine test was negative. Iodine-123 IBZM uptake was significantly higher (p < 0.01) in IPD patients (1.39 +/- 0.114) than in PPS patients (1.27 +/- 0.078). Similarly, iodine-123 IBZM uptake was significantly higher (p < 0.01) in the patients with positive than in those with negative apomorphine test (1.38 +/- 0.113 vs. 1.26 +/- 0.078). In conclusion, the results of this study demonstrate that iodine-123 IBZM SPECT is a radionuclide technique capable of characterizing the patients with extrapyramidal movement disorders and of selecting the subjects who may respond to pharmacological dopamine treatment.

Adult↗
PubMed1996

[Theoretical principles and technical realization of high resolution nuclear magnetic resonance tomography with the example of a dedicated coil system].

The theory of high-resolution magnetic resonance imaging (MRI) and the physical properties of a dedicated coil system with its clinical application are reviewed. To evaluate the spatial resolution of the system, a phantom sample was depicted by a transverse T1-weighted sequence (time of repetition 500 ms, time of echo 25 ms, 256 x 256 matrix, 3 acquisitions, field of view 25 mm2). Relative signal intensity decrease was less using the 5-cm coil, as signal intensity field distribution depends on coil diameter. The phantom appeared as an attainable resolution of 100-microns pixel width using the 2.5-cm coil. For the 5-cm coil the pixel width was 200 microns, not accomplishing clear resolution of the phantom. Coil head choice depends on the anatomic depth of the target organ. Work-up of the skin and musculoskeletal lesions is the main indication for high-resolution MRI using surface coils.

Achilles Tendon↗
PubMed1996

[Leiomyosarcoma of the pulmonary artery].

In a 58-year-old man, a leiomyosarcoma was found to be the cause of unclear thoracal pain on the right side. The initial diagnose was an embolus of the pulmonary artery. The MRI showed a suspicious area similar to an intravasal tumor.

Diagnosis, Differential↗
PubMed1996

[Ultrasound examination of the female breast: comparison of 7.5 and 13 MHz].

PURPOSE: We investigated whether the high resolution ultrasound (13 MHz-scanner) shows smaller lesions and better differentiation than the 7.5 MHz-scanner. METHOD: Prospectively, sonography was performed on forty-seven patients with a 7.5 MHz-scanner as well as with a 13 MHz-scanner in identical slices. RESULTS: Obviously we could obtain more exact diagnoses by using the high resolution scanner. In two patients additional satellite of the primary tumor could be found. In four patients, unclear sonographic findings could be identified as cysts. A disadvantage in the usage of the 13 MHz-scanner is that mastopathy and benign lesions are more difficult to diagnose. With the high resolution more details could be seen although the inhomogeneity as well as the irregularity of the margins are seen more clearly and, therefore, the physician has to reestimate his point of view. To optimize the quality of the pictures made by high resolution ultrasound, it is necessary to regulate the system, which sometimes is quite difficult. CONCLUSION: The recognition of smallest lesions and the reliable presentation of cysts indicates that the 13 MHz-scanner is a good additive diagnostic parameter to the 7.5 MHz-scanner. Therefore, this method may become important for diagnosing multicentrity within carcinomas.

Adult↗
PubMed1996

[clinical application of multiplanar and 3D reconstruction of spiral CT in diagnosis of acetabulum fractures].

This review describes recent visualizations of computed tomography for the diagnosis of acetabular fractures. The techniques of conventional and helical-CT for the imaging of the acetabulum are compared. Furthermore, the different methods of multiplaner and three-dimensional reconstructions e.g. shaded surface display, maximum intensity projection, and volume rendering are presented. Figures of each method are demonstrated and the diagnostic potential of multiplanar and three-dimensional imaging for fractures of the pelvis is discussed.

Acetabulum↗
PubMed1996

[3-dimensional post-myelographic CT reconstruction in diagnosis and therapy planning of spinal dysraphism].

Dysrhaphia is often associated with severe osseous aberrations of the spine such as, for example scoliosis, hemivertebra, and synostosis. With the advanced possibilities of the post-processing of CT-data (segmentation, three-dimensional reconstruction), post-myelo-CT is an excellent method for the evaluation of osseous structures and the myelon in preoperative planning.

Adolescent↗
PubMed1996

[Differentiation of lacrimal gland tumors with high resolution computerized tomography in comparison with magnetic resonance tomography].

In a retrospective study of 15 patients with epithelial and non-epithelial masses of the lacrimal gland, the value of high-resolution computed tomography (CT) with multiplanar and three-dimensional reconstructions was compared to magnetic resonance imaging (MRI). For the differential diagnosis of lacrimal gland lesions the following parameters are important: shape of the lacrimal gland, internal structure, degree of contrast enhancement and integrity of adjacent bony structures. In evaluation of the extent of lacrimal gland lesions, thin-section CT with multiplanar and three-dimensional reconstruction is equal to MRI, while spiral CT with 1-mm slices is superior to standard CT with 2-mm slices. However, internal structure and contrast enhancement of lacrimal glands, integrity of adjacent bones and intracranial infiltration are better visualized with MRI than with CT. Only inhomogeneous mixed tissue tumors can be differentiated from homogeneous tumors by CT due to density differences. In conclusion, MRI is the method of choice if lacrimal gland tumors are suspected, while CT is only useful in doubtful cases concerning the bony structures as an additional method. Using modern imaging modalities, differentiation between epithelial and non-epithelial masses is possible for further diagnosis and therapeutic decisions. Both pleomorphic adenoma due to its different dense components and malignant masses due to bony destruction and intracranial attachment can be differentiated and treated in a specific way. Differentiation between non-epithelial masses (lymphoma and inflammatory pseudotumor) is only possible with a combination of imaging, clinical appearance and in some cases biopsy.

Adolescent↗
PubMed1996

[Anatomy and pathology of the retrobulbar space in MRI using a high-resolution surface coil].

Because of its high soft tissue resolution and its lack of radiation hazard, MRI is considered a valuable method in the diagnosis of orbital disease. Insufficient spatial resolution was considered the main drawback of orbital MRI. Another problem was the chemical shift artifact caused by shifting of the signal of fat and water. To optimize image quality, a high-resolution coil with a small diameter was constructed. Twenty patients with intraorbital changes were examined with MRI. We used a special surface coil with a diameter of 4 cm. For optimal image quality we modified the bandwidth and other parameters of the sequences. For comparison additional measurements were performed in 13 patients with the standard surface coil (diameter 11 cm) and/or the head coil. The best results were obtained with a middle bandwidth (78 Hz); the chemical shift was reduced significantly. Little motion artifacts are visible in every examination caused by involuntary eye movements, which led to evaluation limitations in 3 cases. Compared to the examination with normal coils, the detection of details was much better. In 3 cases small changes were only found with the high-resolution orbital coil. With the high-resolution surface coil it is possible to examine the orbit. It is like looking through a magnifying glass. Using an optimized bandwidth, both the signal-to-noise and the chemical shift are acceptable. The new orbital coil is especially useful for the detection of small orbital lesions.

Adolescent↗
PubMed1996

[Differential diagnosis of cervical lymph node enlargements: ultrasound and histomorphology of reactive lymph nodes].

The purpose of this study was to investigate the morphology of reactive lymph nodes of the neck in ultrasound and its histological implications. By revealing a characteristic sonomorphology of reactive lymph nodes we would like to contribute to the differential diagnosis of cervical lymph node enlargements. In 81 patients the morphology and the longitudinal/ transverse axis ratio (L/T ratio) of 257 reactively enlarged lymph nodes were examined. Besides 6 false-positive cases the L/T ratio turned out to be a reliable instrument in detecting reactive lymph nodes. Concerning the nodal texture, 89 lymph nodes (34.6%) appeared homogenously. Those lymph nodes which demonstrated a more complex nodal texture could be assigned to three sonomorphological groups: In 134 lymph nodes (52.1%) a centrally located echogenoic line ("central echogenoic line', CEL) was observed. Its maximal diameter was defined to be maximally up to one third of the lymph node width. In the histological examination this CEL could be identified as a widened hilus with an increased fibrosis. An echogenoic nodal area measuring between one third up to one half of the lymph node width demonstrated histologically a fatty replacement of the hilar tissue. This "echogenoic hilus reflex' occurred in 28 lymph nodes (10.9%). A nearly complete lipomatous atrophy of the lymph node parenchyma was found in 6 lymph nodes (2.4%) demonstrating a "central echogenicity' with just a small peripheral, less echogenoic border corresponding to the remaining parenchyma.

Adult↗
PubMed1996

[Contrast medium behavior of epithelial skin tumors and tumor-like changes in high resolution magnetic resonance tomography].

To evaluate the use of Gd-DTPA in imaging epithelial skin tumors and tumor-like lesions, 29 benign, 8 malignant and 4 semimalignant skin tumors were prospectively examined by high-resolution MRI at 1.5 Tesla using a 2.5-cm surface coil. For tumor assessment, transverse plain and contrast-enhanced scans (0.1 mmol Gd-DTPA/kg body mass) were performed (TR 500 ms, TE 25 ms, 3 acquisitions, 256 x 256 matrix, FOV 2.5 cm). Contrast enhancement was quantitively determined as the percent enhancement of signal intensity. Histologic findings were correlated using the Mann-Whitney-test (p < 0.05). Quality of contrast enhancement was independently assessed by three investigators, who mostly described inhomogeneous enhancement, regardless of histologic findings. Malignant tumors could not be differentiated from benign lesions by contrast enhancement. MRI using Gd-DTPA does not provide differentiation of skin tumor types.

Adolescent↗