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R Felix

Publications and source records attributed to R Felix.

At least 325 records · Page 18Linked to original sources
PubMed1997

[Experimental validation of a semi-quantitative single-layer procedure for proton-spin tomographic imaging of regional cerebral perfusion].

PURPOSE: The aim of the present study was to validate a simple MRI-procedure for semiquantitative assessment of regional cerebral blood flow. MATERIALS AND METHODS: Unilateral cerebral ischaemia (30 minutes) in the territory of the middle cerebral artery was induced in 14 anesthetised rates. The MRI-experiment consisted in an intravenous bolus injection of gadolinium-DTPA, recording of the cerebral contrast kinetics with a T2*-weighted pulse sequence, and measurement of the maximal concentration change at a chosen reference point of time. To measure perfusion quantitatively, a microsphere technique, an accepted reference technique was used. With both methods a perfusion index related to the contralateral side was calculated. RESULTS: In all cases decreased perfusion was detected by the MRI technique. The perfusion indices correlated with a coefficient of correlation of r = 0.89 (p < 0.001). CONCLUSION: The results demonstrate that contrast-enhanced MRI with bolus injection can be implemented with clinical potential as a semiquantitative instrument for the assessment of cerebral perfusion. Regional cerebral blood volume and collateral blood flow may interfere with the estimate of blood flow.

Animals↗
PubMed1997

[Contrast agent enhanced duplex ultrasonography: visualization of the hepatic artery after orthotopic liver transplantation].

PURPOSE: A prospective study was carried out to determine whether an improved assessment of the anatomy and flow velocity in the hepatic artery could be achieved by the administration of a capillary transversing contrast agent (Levovist) in patients after orthotopic liver transplantation. METHODS: In 21 (62%) of 34 patients after liver transplantation, only an insufficient visualisation of the hepatic artery was achieved. Therefore, a capillary transversing contrast agent was administered intravenously. Pre- and post-contrast peak velocity and Doppler frequency shift in the proper hepatic artery were measured and image quality of colour and spectral Doppler was assessed by a qualitative scale. RESULTS: Image quality, with complete visualisation of hepatic artery in 79% (precontrast 38%) of all cases, was significantly improved (p < 0.01 (Wilcoxon test)) by the administration of a contrast agent. CONCLUSIONS: Visualisation of the hepatic artery after orthotopic liver transplantation can be improved by the administration of Levovist. It allows a reliable measurement of peak velocity and Doppler frequency shift and helps to avoid further imaging.

Adult↗
PubMed1997

[Vascularization patterns in focal liver lesions: comparison of plain and signal-enhanced amplitude-modulated color duplex ultrasonography].

PURPOSE: Morphology of focal liver lesions was studied by power Doppler. Plain images and images after i.v. application of galactose-based microbubbles (Levovist, Schering AG) were compared. METHODS: 21 patients with focal liver lesions were studied by power Doppler before and after application of the signal enhancer. RESULTS: In lesions that showed short pulsations in plain studies, vascular structures were visible after application of the signal enhancer. In hepatocellular carcinomas, multiple arteries with small diameter became visible. Peripheral veins were detected in metastases. A large feeding artery was detected in 1/2 haemangiomas with flow and in a focal nodular hyperplasia. CONCLUSION: In comparison to plain amplitude-modulated colour-coded duplex ultrasound, vascular patterns of focal liver lesions were more clearly visible after injection of a signal-enhancer.

Adult↗
PubMed1997

[Volumetric and morphological CT parameters for assessing prognosis and treatment control in hepatocellular carcinoma undergoing arterial chemoembolization].

PURPOSE: To evaluate volumetric CT data as a guide for indication and assessment of prognosis for transarterial chemo-embolisation (TAE) of hepatocellular carcinomas (HCC). MATERIAL AND METHOD: 74 patients with HCC were treated with repeated TAE. 50 mg Adriblastin/m2 body surface, 50 mg cisplatin/m2 body surface and 10 ml lipiodol were combined with 2-10 ml Spherex and injected selectively (25 cases) or superselectively (49 cases); in 28 patients a single injection and in 46 patients multiple injections were used. RESULTS: CT findings before and after the procedure showed a solitary lesion in 17 patients, two lesions in 18 patients and in 39 patients there were three or more lesions. Mean expectation of life was 523 days (median = 372 days; 57% of one year survival probability). In 29 patients with > 75% lipiodol retention, mean survival was 819 days; in 17 patients with < 75% lipiodol retention it was 382 days; lower lipiodol retention of < 50% it was 231 days (< 25% 192 and < 10% 152 days). A statistically significant relationship (p < 0.0001) could be established between survival time and tumour volume, relationship of tumour to liver volume, intratumoral lipiodol retention, the type of tumour growth and the number of liver segments involved. CONCLUSION: TAE provides best survival rates after repeated injections of solitary HCC with tumour volumes < 50 ml and > 75% intra-tumoral lipiodol retention.

Aged↗
PubMed1997

[Dynamic computerized tomography of the bone marrow of normal and pathologic vertebrae].

PURPOSE: The contrast medium dynamics of normal and abnormal bone marrow was examined by CT. MATERIAL AND METHOD: Standardised sections of lumbar vertebrae were obtained after intravenous injection of 80 ml Ultravist 370 and time-density curves of the marrow spaces were calculated in 38 patients. RESULTS: Time-density curves of patients with normal bone marrow differed significantly from those with proliferative bone marrow diseases in respect of maximal density and uptake at 120 and 240 seconds. Patients treated by radiation showed reduced uptake. CONCLUSION: Variations in the time-density curves between normal and abnormal bone marrow provided evidence of different perfusion and uptake of the contrast medium in the extracellular space of the bone marrow. Further investigation will be necessary to determine whether dynamic CT is able to document the effect of radiotherapy or chemotherapy on malignant bone marrow infiltration.

Adenocarcinoma↗
PubMed1997

[Dynamic and static MRI using superparamagnetic MRI contrast medium Resovist for visualizing primary and secondary liver tumors].

PURPOSE: To analyse characteristics of benign and malignant liver tumours in dynamic and static MR imaging with the superparamagnetic MR contrast medium Resovist. MATERIAL AND METHODS: All 30 patients were examined on a 1.5 Tesla MR unit (Magnetom 63 SP, Siemens AG, Erlangen, Germany) using proton density (PD) weighted (w), T2-weighted-spin-echo, a T1-weighted SE, and a T1-weighted FLASH-2 D gradient echo (GRE) sequence before, during and after the application of Resovist. Dynamic imaging was performed using a T2-weighted GRE-sequence (TurboFLASH; TR/TE = 11/30; flip angle = 10 degrees; Tl = 600 ms). Histopathology revealed benign liver lesions in 8 patients and malignant lesions in 22 patients. RESULTS: Dynamic T2-weighted sequence revealed an early loss of signal intensity in normal liver parenchyma (percentage signal intensity loss (PSIL) = 40.0 +/- 12.2% by 4 mumol Fe/kg, 47.2 +/- 18.8% by 8 mumol Fe/kg and 62.7 +/- 13.0% by 16 mumol Fe/kg), in the spleen, as well as in FNH (PSIL = 49.5 +/- 7.3% by 8 mumol Fe/kg), and regenerating nodules in the first minute after application of Resovist. In two of 4 cases with HCC a short drop in signal intensity was immediately observed after the application, whereas signal intensity remained unchanged in all other malignant liver tumours. Enhanced PDw and T2-weighted SE-sequences revealed an improved detection and delineation of malignant liver lesions versus plain MR imaging. 17 liver lesions of a size lower 10 mm were additionally detected in postcontrast T2-weighted SE-sequences in 4 patients. CONCLUSION: Dynamic and static versus plain MR imaging of primary and secondary liver lesions is markedly improved by the superparamagnetic contrast material Resovist, especially in case of intravenous bolus application of this liver-specific contrast medium.

Adult↗
PubMed1997

[Use of Ga-67 SPECT in patients with malignant lymphoma after primary chemotherapy for further treatment planning: comparison with spiral CT].

PURPOSE: To compare the diagnostic value of gallium scintigraphy using a SPECT technique with spiral CT for evaluating activity following chemotherapy in patients with malignant lymphoma and to determine treatment options. MATERIAL AND METHOD: The results of gallium scintigraphy in 28 patients with malignant lymphoma (19 Hodgkin's disease, 9 high grade non-Hodgkin's lymphoma) following curative treatment were compared with the CT morphology in relation to inactive regions and residual masses. RESULTS: Ga-67-SPECT proved superior to CT for evaluating the activity in 85 initially involved nodes (sensitivity 94.4% against 83.3%; specificity 100% against 92.5%). It was, however, inferior for demonstrating organ involvement in 28 instances. In seven patients with residual masses, Ga-67-SPECT directly affected staging and further therapy. CONCLUSION: The increasing use of secondary treatment schemes for curative purposes makes Ga-67-SPECT a suitable method for the early recognition of residual activity in Hodgkin's disease and high grade non-Hodgkin's lymphoma.

Adult↗
PubMed1997

[Magnetic resonance imaging of the degree of pulmonary edema using a macromolecular contrast medium].

PURPOSE: Development and experimental validation of a method tor the quantification of pulmonary oedema by measurement of total lung water and intravascular lung water and by calculation of extravascular lung water. MATERIAL AND METHODS: Isolated sheep lung preparations with unilateral pulmonary oedema were perfused (pulsatile pump) and examined under ventilatory arrest and during ventilation. Total lung water was calculated from proton density obtained from a multi-spin echo sequence and gravimetrically (reference method). Pulmonary intravascular volume was calculated from signal intensity histograms obtained from 3D-TOF MR-angiograms before and after application of the macromolecular contrast medium gadolinium-DTPA-polylysine. The reference method was a dye-dilution technique. Extravascular lung water was calculated as the difference between total lung water and pulmonary intravascular volume. RESULTS: Under ventilatory arrest, the magnetic resonance technique for the measurement of extravascular lung water correlated well with the reference technique (r = 0.89, n = 42 lungs). In 10 lungs the correlation coefficients were r = 0.95 (ventilatory arrest) and r = 0.92 (ventilated lungs). CONCLUSION: The results demonstrate that magnetic resonance imaging enhanced by a macromolecular contrast medium may be applicable for quantification of pulmonary oedema.

Animals↗
PubMed1997

[Safety and use of gadobutrol in patients with brain tumors (phase III trial)].

PURPOSE: The purpose of the study was to investigate the use and safety of Gadobutrol, a new low-osmolar, non-ionic contrast agent for MRI using a total dose of 0.3 mmol/kg b.w. on the basis of a clinical phase 3 study. METHODS: 30 patients with primary brain tumours (n = 15) or cerebral metastases (n = 15) were examined via MRI before and after application of a total of 0.3 mmol/kg b.w. given in two fractions (0.1 and 0.2 mmol/kg b.w.). T2-weighted images were performed before, T1-weighted images before, between and after application of contrast material. RESULTS: In this study one-molar Gadobutrol showed a good tolerance. In half of the cases the contrast between lesion and brain was improved comparing single and triple dose, but this means only a slightly improvement of information for the primary brain tumours compared with single dose. The detected metastatic lesions increased in 40% of the patients after the single dose and in 53% of the patients after cumulative triple dose. There was a consecutive change in therapy in 20% of the patients. CONCLUSION: For the differentiation of primary brain tumours the single dose was sufficient, in metastatic lesions triple dose was essential for the detection or exclusion of multifocality.

Adenoma↗
PubMed1997

[In vitro evaluation of MR thermometry in the implementation of laser-induced thermotherapy].

PURPOSE: To optimize the MR sequences parameter for monitoring hyperthermic effects in the tissue during laser induced thermotherapy (LITT). MATERIAL AND METHODS: Experimental studies were performed for the evaluation of MR-thermometry using a contrast-agent-water solution and a pig-liver. A T1-weighted TurboFLASH sequence and a FLASH-2D sequence were used. The TurboFLASH sequence was used with various T1 settings (between 100 and 1250 ms). MR findings were correlated with temperature measurements using a fluoride optical temperature measuring system in a distance of 1, 2, and 5 cm from the laser applicator. RESULTS: Using the contrast-agent-water solution demonstrated the temperature sensitivity of both sequences. In vitro evaluations using pig liver demonstrated a near linear increase of signal versus increasing tissue temperatures in a distance of 1 cm to the tip of the laser applicator. Optimal visualization of the temperature effects was obtained using a T1 between 100 ms and 400 ms. Using the FLASH-2D sequence a signal loss was documented at a TR of 110 ms. CONCLUSION: MR-thermometry using sequentially TurboFLASH and FLASH-2D sequences allowed a non-invasive monitoring of the laser induced temperature changes.

Animals↗
PubMed1997

Abdominal CT features and survival in acquired immunodeficiency.

PURPOSE: HIV-infected patients show a high incidence of abdominal disease. This investigation was made to determine whether abdominal CT provided prognostically relevant information in these patients. MATERIAL AND METHODS: Images from 533 abdominal CT examinations in 339 HIV-infected patients were retrospectively reviewed for signs of abdominal disease, and correlated with clinical data and survival rates. The Kaplan-Meier analysis and rank testing of survival, and proportional hazards regression were used to define prognostic clinical and imaging findings. RESULTS: Of the 339 patients, 278 (82%) showed abnormal abdominal findings on CT. Median survival was 29 months. Of the imaging findings, hepatic masses (n = 11), pathologically enlarged lymph nodes (n = 48), and ascites (n = 7) were associated with poor survival, giving a median survival of respectively 13 months, 15 months, and less than 1 month. These three features showed no association with CD4(+)-T-lymphocyte count or CDC category. Main determinants of survival were a low CD4(+)-T-lymphocyte count, and certain abnormal CT findings. Splenomegaly (n = 147), hepatomegaly (n = 144), and lymphadenopathy (n = 111) were the most common abdominal findings on CT but lacked prognostic relevance. CONCLUSION: Abdominal CT offered prognostic implications in HIV-infected patients and might serve in risk stratification in selected patients. CT features such as hepatic masses, grossly enlarged lymph nodes, or ascites indicate advanced immunosuppression.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Magnetic resonance imaging in the diagnosis of acute injured distal tibiofibular syndesmosis.

RATIONALE AND OBJECTIVES: This study assessed the diagnostic potential of magnetic resonance imaging for the evaluation of the tibiofibular syndesmosis. METHODS: A total of 38 patients with an acute ankle trauma and clinical suspicion of a syndesmotic tear were prospectively studied with conventional plain film radiography and magnetic resonance imaging. Magnetic resonance imaging studies included plain T1-weighted (T1-w) and T2-weighted (T2-w) sequences and contrast-enhanced T1-w sequences 0 to 3 days after trauma. All images were read by two independent radiologists before surgical intervention. Sensitivity and specificity were determined for the two observers and the concordance of the two observers were calculated using the interobserver analysis (Kappa-Test). Intraoperative inspection (n = 21) revealed rupture of the anterior tibiofibular ligament (ATIF) in 15 patients, intact ATIF in 6 patients, and intact posterior tibiofibular ligament (PTIF) in 21 cases. Clinical and follow-up examinations revealed an intact syndesmotic complex in another 17 patients. RESULTS: Primary diagnostic criteria for diagnosing a ligamentous tear included tibiofibular diastasis in conventional plain films; nonvisualization of the ATIF; an abnormal course, a wavy, irregular contour of the ligament; increased signal intensity of the ligament in T2-w sequences, in plain T1-w sequence, and marked enhancement in T1-w after contrast. Important secondary signs were defined as joint fluid in the tibiofibular space and prolapse of interspace fat. Highest diagnostic accuracy was achieved if three or more diagnostic criteria could be visualized. Both readers performed best with the enhanced T1-weighted and the T2-weighted images in transverse orientation. The interobserver analysis resulted in high concordance: Kappa = 0.9 (confidence interval: 0.76 to 1.00) for all patients, and in Kappa = 0.76 (confidence interval: 0.45 to 1.0) for surgically treated patients. CONCLUSIONS: Magnetic resonance imaging of the syndesmotic complex is a highly sensitive and specific tool for the pretherapeutic-evaluation of syndesmotic injury.

Acute Disease↗
PubMed1997

Evaluation of metastases and reactive lymph nodes in Doppler sonography using an ultrasound contrast enhancer.

RATIONALE AND OBJECTIVES: The authors conducted a prospective study in D-galactose signal-enhanced Doppler sonography of lymph nodes to investigate new aspects in differentiating malignant from reactive lymph nodes of patients with suspected malignancy of the neck. METHODS: Twenty-one patients with suspected squamous epithelial cell carcinoma metastases of the neck were examined by Doppler sonography before and after administration of an ultrasound signal-enhancing agent, consisting of D-galactose microbubbles. Qualitative sonomorphology, peak flow rates, and pulsatility and resistive indices were assessed. RESULTS: Compared with conventional Doppler, enhanced Doppler sonography gave detailed additional information about vascularization of metastases or reactive lymph nodes. Signal-enhanced Doppler of metastases showed a relatively characteristic pattern of vascularity, therefore facilitating differential diagnoses and allowing better discrimination from surrounding tissue, demonstrated by the infiltration of neighboring vessels in the neck. Concerning reactive lymph nodes, vascularization could be stated and measured in many cases only after signal enhancement. Evaluating peak velocities and pulsatility and resistive indices could not differentiate significantly malignant from reactive lymph nodes. CONCLUSIONS: Administration of a D-galactose-based signal-enhancer helps to differentiate malignant from reactive lymph nodes of the neck. It is superior to conventional Doppler by improving evaluation of the vascularity and could be of use for staging procedures.

Aged↗
PubMed1997

Hemodynamic tolerance of intravascular contrast agents for magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Intravascular contrast agents for magnetic resonance imaging (MRI) facilitate the quantification of tissue perfusion. The authors determined the hemodynamic tolerance of these agents. METHODS: Doses of 0.05, 0.15, and 0.45 mmol/kg of the polymeric intravascular contrast agent gadolinium-DTPA-polylysine, and di-nitrobenzyl-gadolinium-DTPA, a non-polymeric intravascular contrast agent with high protein binding, and gadolinium-DTPA dimeglumine, a paramagnetic contrast agent with extracellular distribution, were injected into 18 normal male rats as a peripheral intravenous bolus. Systolic, diastolic, and mean blood pressure, left ventricular end-diastolic and developed pressure, positive rate of pressure change (+dP/dt), dP/dt, the rate-pressure product, and heart rate were recorded during a period of 20 minutes. Hemodynamic effects were established by analysis of variance for repeated measurements. RESULTS: There was a transient increase of all blood pressure parameters and contractility for Gd-DTPA-polylysine at the dose of 0.45 mmol/kg only. Di-nitrobenzyl-Gd-DTPA increased blood pressure parameters at 0.45 mmol/kg only. At doses of 0.05 and 0.15 mmol/kg, no significant hemodynamic effects were observed. CONCLUSIONS: The authors conclude that Gd-DTPA-polylysine is hemodynamically safe at doses to 0.15 mmol/kg and acts like a plasma expander at higher doses after peripheral bolus injection in normal rats. Additional investigations are indicated to elucidate the mechanism of a nonsignificant and satiable transient hemodynamic depression after injection of 0.05 mmol/kg DNB-Gd-DTPA.

Animals↗
PubMed1997

Uveal melanoma: detection of extraocular growth with MR imaging and US.

PURPOSE: To compare the sensitivity and specificity of magnetic resonance (MR) imaging with that of ultrasound (US) in the detection of extraocular extension of uveal melanoma. MATERIALS AND METHODS: In 70 patients, the diagnosis of melanoma and absence or presence of extraocular growth were confirmed with histologic examination (13 patients) or with ophthalmoscopy and surgery (57 patients). Unenhanced and enhanced T1-weighted and T2-weighted MR imaging was performed with surface coils at 1.5 T. A- and B-mode US scans were obtained with 8- and 10-MHz probes, respectively. RESULTS: Extraocular growth was confirmed in seven patients: Five patients had retrobulbar tumor, and two had optic nerve infiltration. US enabled detection in three cases, whereas six cases were diagnosed with MR imaging including both cases of optic nerve infiltration. False-positive findings were more frequent with US (n = 5) than with MR imaging (n = 1). CONCLUSION: MR imaging proved to be more sensitive and more specific than US in the detection of extraocular extension of uveal melanoma.

Eye Neoplasms↗
PubMed1997

Peripheral washout sign on contrast-enhanced MR images of the breast.

PURPOSE: To assess the value of the peripheral washout sign on delayed contrast material-enhanced magnetic resonance (MR) images in differentiation of benign from malignant breast masses. MATERIALS AND METHODS: In 49 women with 79 breast lesions (55 malignant and 24 benign), dynamic contrast-enhanced MR imaging was performed every 90 seconds during the first 7 minutes and repeated at 10, 20, 30, 40, 50, and 60 minutes after injection of contrast material. Qualitative analysis of the images was performed to evaluate the presence of the peripheral washout sign (a hypointense zone in the periphery of the lesion relative to the center). Quantitative analysis of the images was performed by measuring the signal intensity of the periphery and center of the lesions. RESULTS: The peripheral washout sign was seen in 28 (51%) of the 55 carcinomas on delayed contrast-enhanced MR images (> 10 minutes). Quantitative analysis demonstrated different enhancement profiles of the periphery and center of these lesions. The periphery showed early increase and decrease of enhancement, while the center showed gradual increase and persistent enhancement. The peripheral washout sign was not seen in any of the benign lesions. Specificity was 100% and sensitivity was 51% for diagnosis of breast carcinoma. CONCLUSION: Peripheral washout may be a reliable sign of malignancy on delayed contrast-enhanced MR images of the breast.

Adult↗
PubMed1997

Hepatocellular carcinoma: evaluation with dynamic and static gadobenate dimeglumine-enhanced MR imaging and histopathologic correlation.

PURPOSE: To analyze the potential of gadobenate dimeglumine-enhanced magnetic resonance (MR) imaging for the characterization and diagnosis of hepatocellular carcinoma (HCC) by using static and dynamic sequences. MATERIALS AND METHODS: Twenty-eight patients with histopathologically proved HCC were evaluated with T1- and T2-weighted spin-echo and static and dynamic gradient-echo sequences before, during, and after intravenous administration of 0.1 mmol/kg gadobenate dimeglumine (0.5 mol/L). RESULTS: During the perfusion phase of the dynamic sequence, all 16 nodular well-differentiated HCC lesions showed a rapid increase in signal intensity 10-30 seconds after injection followed by a progressive decrease in signal intensity. The nine poorly differentiated HCC lesions showed no rapid increase in signal intensity. All eight large (> 3 cm), nodular, well-differentiated HCC lesions showed a hypointense rim before injection and both hypo- and hyperintense rims (double-ring sign) immediately after injection, compared with normal liver parenchyma. About 55 seconds after injection, substantial single-rim enhancement was detected in 21 of the 28 HCC lesions. CONCLUSION: Dynamic gadobenate dimeglumine-enhanced MR imaging allows improved characterization of HCC lesions, which show rapid increase in signal intensity during the early, arterial phase in well-differentiated HCC lesions and a double-ring sign in large well-differentiated nodular HCC lesions.

Carcinoma, Hepatocellular↗