Biomedical subjects

R Felix

Publications and source records attributed to R Felix.

At least 145 records · Page 8Linked to original sources

PubMed2001

Hemorrhagic cavernoma or ruptured dermoid of the orbit: Diagnosis with MRI.

MRI is a useful tool to study space-occupying lesions of the orbit. We present two cases of intraorbital lesions that were found to be a hemorrhagic cavernous hemangioma and a ruptured dermoid, respectively. The difficulties in arriving at the diagnosis of these rare entities with MRI are discussed. In general, dermoids are characterized by a peripheral, extra-conal location in the immediate vicinity of an orbital suture, while cavernous hemangiomas tend to be intraconal. Secondary complications of both entities, such as hemorrhage or rupture, may alter the characteristic MRI signal patterns found in uncomplicated lesions. Inflammatory reactions may be observed. The signal of the fatty dermoid and the hemorrhagic part of a cavernoma are both of high intensity on the T1-weighted images, and this may lead to diagnostic difficulties.

Journal Article↗

PubMed2001

CT-guided percutaneous core biopsies of pulmonary lesions. Diagnostic accuracy, complications and therapeutic impact.

PURPOSE: To evaluate the diagnostic accuracy, complications, and therapeutic impact of CT-guided percutaneous core biopsies of pulmonary lesions. MATERIAL AND METHODS: Seventy-nine patients underwent diagnostic CT-guided percutaneous core biopsies of pulmonary lesions between July 1995 and March 1999. Evaluation included corresponding clinical data, pathologic results, and therapeutic consequences. RESULTS: There were 29 benign and 50 malignant lesions. Percutaneous core biopsy had an overall diagnostic accuracy of 95%. For malignant lesions, core biopsy was positive in 48 patients (sensitivity 96%), and for benign lesions, in 27 (sensitivity 93%). There were no false-positive findings. Pneumothoraces were observed in 19 patients (24%) and 4 of them required a chest drain (5%). There were no hematothoraces or major bleeding complications; however, postinterventional local hemorrhages were observed in 23 patients (29%). No hemoptysis was noted. CONCLUSION: Percutaneous core biopsies of pulmonary lesions offer excellent diagnostic accuracy for both benign and malignant pulmonary lesions at a low complication rate.

Adult↗

PubMed2001

Vascularization of malignant and benign skin tumours measured by D-galactose-based signal-enhanced colour Doppler sonography.

PURPOSE: Evaluation of colour Doppler criteria to differentiate between malignant and benign skin tumours on the basis of the degree of vascularization. MATERIAL AND METHODS: The B-mode sonomorphology and the degree of vascularization in colour Doppler of 81 clinically potentially malignant tumours of cutaneous and subcutaneous structures were analyzed and quantified by number of intratumoral vessels per sonographic slice and percentage vessel area. RESULTS: Of all criteria employed, counting the intratumoral vessels visible on one ultrasound slice after application of a signal-enhancing agent led to highest sensitivity (94%) of all used criteria but the specificity was poor (64%). The highest specificity (88%) and greatest diagnostic accuracy (86%) discriminating benign and malignant lesions were found using the criterion "percentage vessel area >5.0%" after all inflamed lesions had been excluded on the basis of clinical criteria. Plain colour Doppler increased the specificity up to 97%, although the sensitivity decreased simultaneously to max. 75%. Analysis of the B-mode morphology and spectral Doppler parameter of intratumoral vessels did not contribute to the differential diagnosis. CONCLUSION: Signal-enhanced colour Doppler sonography is a valuable tool in the pretherapeutic assessment of cutaneous lesions. This method may be relevant for therapy and prognosis.

Adolescent↗

PubMed2001

Detection of myocardial ischemia by electron beam CT. Experimental studies.

PURPOSE: To determine if contrast-enhanced electron beam CT (EBCT) can detect areas of acute myocardial ischemia, and if pharmacological stress testing improves the diagnostic accuracy of EBCT. MATERIAL AND METHODS: We injected 0.5 ml/kg and 1.0 ml/kg b.w. of iopromide at a rate of 4 ml/s into the right atrium of 5 ventilated female minipigs at rest and after occlusion of the left anterior descending (LAD) coronary artery. Both ventricles were examined at six short axis levels with an EBCT unit. Myocardial perfusion was calculated from the time-density curves of four left ventricular myocardial segments and the aorta. We also tested the effect of the contrast agent on myocardial density after i.v. administration of 0.6 mg/kg dipyridamole before and after LAD occlusion. RESULTS: At rest, the contrast agent increased myocardial density by 28+/-2 HU, corresponding to a myocardial perfusion estimate of 67+/-7 ml/min/100 g. After dipyridamole, myocardial density increased by 29+/-4 HU. Following occlusion of the LAD, anteroseptal myocardium displayed 10+/-4 HU density increase. The area of non-enhancement corresponded to ischemic myocardium in stained pathologic sections. CONCLUSION: Contrast-enhanced stress EBCT can be used to detect areas of myocardial ischemia, and EBCT stress perfusion imaging may be necessary to consistently differentiate ischemic from non-ischemic myocardial tissue.

Animals↗

PubMed2001

Stent placement in short unilateral iliac occlusion. Technique and 24-month results.

PURPOSE: To determine the success rate and 24-month follow-up results of primary stent implantation for reconstruction of unilateral short iliac occlusion involving the aortic bifurcation. MATERIAL AND METHODS: In 90 patients attempts of percutaneous transluminal recanalization of a short unilateral occlusion of the iliac arteries were performed. In 72/90 patients, the treatment was successful. Stent implantation was performed after recanalization in all 72 patients. Pre-interventional angiography of successfully treated patients showed unilateral occlusions and contralateral stenosis in 34/72 patients. In 38/72 patients unilateral occlusion without contralateral stenosis was diagnosed. The recanalization of the common iliac artery obstructions were performed with a guidewire and excimer laser angioplasty. Totally 152 stents were used for the treatment of iliac occlusion. Standardized treadmill testing and color-coded Doppler ultrasound were performed before treatment and during the follow-up. RESULTS: In all patients, stents were placed successfully; 5 major and 7 minor complications were observed. A clinical improvement of +2 to +3 according to the American Heart Association criteria was observed in 62 and 10 patients, respectively. Angiographic control was performed after 1-30 months. The primary angiographic patency rate was 83.1%. Angiography revealed significant restenoses in 4 patients successfully treated with transluminal angioplasty, and re-occlusion in 6 patients which were referred to surgery. The patency rate after 24 months was 90.0%. CONCLUSION: Primary stent implantation is an effective treatment for short iliac obstructions and represents a true endovascular alternative to surgery.

Adult↗

PubMed2001

Histopathological correlation to MRI findings during and after laser-induced thermotherapy in a pig pancreas model.

RATIONALE AND OBJECTIVES: To investigate whether percutaneous laser-induced thermotherapy (LITT) with continuous magnetic resonance (MR) monitoring of thermal effects within the pancreas is feasible in a porcine model. METHODS: Laser applicators were placed in the pancreas of 15 female pigs. A temperature-sensitive (thermo--fast low-angle shot) sequence was used for continuous monitoring of thermal effects during LITT at 1.5 T. Follow-up MR images were acquired, the pigs were observed for 7 days, and then a pathological examination was performed after sacrifice. RESULTS: Continuous MR monitoring visualized thermal effects in pancreatic tissue and thermal damage of the spleen (n = 1), the left kidney (n = 1), and peripancreatic fat (n = 4) but missed the thermal damage of the duodenum (n = 2). Thermal-induced lesions (10--32-mm diameter) were clearly visualized on contrast-enhanced T1-weighted images. CONCLUSIONS: Laser-induced thermotherapy of pancreatic tissue was feasible in this porcine model, and online monitoring was practicable. Further studies are necessary to increase the accuracy of online MR imaging of thermal effects.

Amylases↗

PubMed2001

Combined CT pulmonary angiography and venography for diagnosis of pulmonary embolism and deep vein thrombosis: radiation dose.

A major concern about combined pulmonary CT angiography (PCTA) and CT venography (CTV) refers to the additional radiation exposure to the patient. The purpose of this paper is to analyze the organ dose, the effective dose, and the gonadal dose of combined PCTA and CTV. Effective dose and gonadal dose in PCTA and CTV were calculated. Also measured was the organ doses with thermoluminescence dosimeters in six patients who underwent combined PCTA/CTV. The risk from the effective dose and gonadal dose in combined PCTA/CTV is low. Nevertheless, additional CTV increases the gonadal dose by a significant factor and use of this procedure should be limited in younger patients.

Angiography↗

PubMed2001

Survey of conventional and spiral ct doses.

PURPOSE: To investigate the radiation dose for conventional computed tomography (CT) and spiral CT during different CT examinations at various hospitals and practices. MATERIALS AND METHODS: CT dose index with an active length of 15 cm was measured in 16 different types of CT scanners by using ionization chamber dosimetry. Twenty-six holders (one who has legal responsibility under national law for a radiologic installation) operating a total of seven conventional and 20 spiral CT scanners were asked for their standard parameters for various CT examinations. Weighted CT dose index and dose-length product were determined for each examination. RESULTS: For most examinations, the tube current time product was significantly higher for conventional CT than for spiral CT (.002 </= P </=.05). The ratio of section distance to section thickness for conventional CT was significantly lower than the pitch for spiral CT (.001 </= P </=.05). The weighted CT dose index and dose-length product for spiral CT were about half of those for conventional CT. The third quartiles for weighted CT dose index and dose-length product for spiral CT were much lower than those recommended as reference doses. CONCLUSION: CT examinations with conventional CT scanners are often performed with unnecessarily high radiation dose. For the establishment of reference doses, the radiation dose with spiral CT scanners should be taken into account.

Humans↗

PubMed2001

The role of phosphoinositide 3-kinase in spreading osteoclasts induced by colony-stimulating factor-1.

BACKGROUND: Colony-stimulating factor-1 (CSF-1), a growth and survival factor for osteoclasts, stimulates these cells to spread and migrate towards a gradient of CSF-1. This may support the translocation of osteoclasts to new sites on the bone surface to be resorbed. Phosphoinositide 3-kinase (PI 3-K) is a lipid kinase participating in various signal transduction pathways. OBJECTIVE: To investigate the role of PI 3-K in the CSF-1-induced spreading of osteoclasts. METHODS: In isolated rat osteoclasts treated with or without CSF-1, the distribution of PI 3-K and proteins phosphorylated on tyrosine were investigated using immunofluorescence. In murine osteoclast-like cells grown from bone marrow cells co-cultured with osteoblasts, the activation of the PI 3-K by CSF-1 was determined both in vivo and in vitro. In vivo, the enzyme product in the cell was determined after extraction and separation with thin layer chromatography; in vitro, PI 3-K activity was measured in the pellet immunoprecipitated from the cell lysate. RESULTS: Inhibition of PI 3-K blocked the CSF-1-induced spreading of osteoclasts. In spreading osteoclasts, a portion of PI 3-K was translocated to the periphery where proteins phosphorylated on tyrosine appeared simultaneously. In osteoclast-like cells, CSF-1 stimulated PI 3-K activity. This activity could be immunoprecipitated with antibody against phophotyrosine residues. CONCLUSION: PI 3-K participates in the CSF-1-induced spreading of osteoclasts. The activated PI 3-K may induce the reorganization of the cytoskeleton resulting in spreading and migration.

Androstadienes↗

PubMed2001

[MRI in the diagnosis of tumors of the shoulder girdle area].

The aim of the study was to estimate the value of MRI for evaluation tumors of the shoulder girdle. We diagnosed respectively 13 patients with lesions in the shoulder region. The imaging has been done with a "Magnetom SP 63" (Siemens, Erlangen, Germany). The protocol consisted of T1- and T2-based SE-sequences in axial slice orientation, T1-based imaging in coronary respectively in sagittal slice orientation as well as T1-based sequences after application of contrast medium. The evaluation of the tumor expansion within the soft tissue was possible. The exact diagnosis in some individual cases--neurinoma, cyst of the synovia--could be found by MRI. Estimation of the dignity in the case of infiltrative growth was possible in most cases. To assess the exact type of tumor was often difficult. Especially the dignity of the cartilaginous tumors could not be precisely described.

Acromion↗

PubMed2001

[MRI diagnosis of injuries and diseases of peroneal tendons].

Injuries of the peroneus tendons are common and both the athlete and the older population are at risk. MR imaging is a useful technique for revealing injuries of the peroneus tendons as well as showing anatomic factors associated with these lesions. This article reviews clinical factors and MR imaging characteristics of injuries of the peroneus tendons.

Ankle Injuries↗

PubMed2001

[The use of cross-sectional imaging modalities in the diagnosis of heart valve diseases].

Exact visualization of valve morphology seems to be possible with the cross-sectional imaging modalities, magnetic resonance imaging (MRI) and the recently introduced technique of multi-detector computed tomography (MDCT). These techniques are used, if other non-invasive imaging modalities, like echocardiography, fail or provide only insufficient information. This commonly occurs in the assessment of right ventricular valves. Quantification of valve stenosis is possible by calculating valve orifice area, which can be performed with MRI and MDCT. An estimation of the instantaneous peak gradient can only be achieved by MR flow measurements. MR flow measurement is a reliable method to quantify the degree of mild to moderate stenoses. Quantification of valve regurgitation is possible by measurement of the regurgitation fraction with MR flow measurements as well as with MR volumetry/CT volumetry. But only the MR flow measurement is suitable for the quantification of valve regurgitation in patients with multiple valves involved or cardiac shunting. MRI and probably MDCT are the most reliable methods in the evaluation of ventricular volumes and therefore suitable for the follow-up in patients with valvular heart disease, because changes in volumes are important for therapeutic decisions in these patients. The crucial advantages of MRI compared to CT in the diagnostic of valvular heart diseases however are the absence of radiation exposure, the possibility of quantitative evaluation of valves function using flow measurements and the higher temporal resolution as compared to MDCT.

Adolescent↗

PubMed2001

[Multi-slice spiral CT: 3D CT angiography for evaluating therapeutically relevant stenosis in peripheral arterial occlusive disease].

PURPOSE: Evaluation of 3D multislice CT angiography for the assessment of relevant stenoses of pelvic arteries and arteries of the lower extremity in patients with peripheral artery occlusive disease compared to digital subtraction angiography. METHOD/MATERIALS: For this study we examined 31 patients with peripheral artery occlusive disease. All patients received a multislice helical CT angiography and arterial digital subtraction angiography. Multislice CT angiography was performed with a Somatom Plus 4 Volume Zoom (Siemens, Erlangen, Germany). After test bolus injection of 20 ml Ultravist 370 (Schering AG, Berlin) additional 150 ml were applied with a flow rate of 3 ml/sec and a scan delay between 20-35 sec depending on individual blood circulation time. Collimation was 4 x 2.5 mm with a pitch of 6. Reconstructed slice thickness was 3 mm. 3D reconstructions of arteries of pelvic and lower extremity arteries were performed in volume rendering technique on a 3D Virtuoso workstation (Siemens, Erlangen). RESULTS: For the assessment of therapeutically relevant stenoses (over 50% reduction of luminal diameter) multislice CT achieved the following results compared to conventional angiography for the diagnosis of stenosis: sensitivity of 86%, specificity of 86% and an accuracy of 72%. CONCLUSIONS: Multislice helical CT angiography of pelvic arteries and arteries of the thigh represents a reliable means for the detection of relevant stenoses in patients with peripheral occlusive artery disease.

Adult↗

PubMed2000

Reversibility of the Ca(2+) channel alpha(1)-beta subunit interaction.

The auxiliary beta subunit importantly regulates voltage-dependent Ca(2+) channel activity through an interaction with the AID domain, a binding site located in the cytoplasmic I-II linker of the ion-conducting alpha(1) subunit. In the present study, we used two synthetic peptides corresponding to partial sequences of the I-II linker of alpha(1A) (AID(A)-peptides) as tools to disrupt the alpha(1)-beta interaction. In vitro binding experiments confirmed that these peptides exhibit a reasonable affinity to the neuronal beta(3) subunit to serve this purpose, although they failed to prevent immunoprecipitation of native N- and P/Q-type channels by anti-beta(3) antibodies. Together, our results (i) provide evidence for the reversibility of channel subunit association suggesting that the disruption of the alpha(1)-beta interaction may be a possible mechanism for Ca(2+) channel regulation in vivo, and (ii) support a model whereby the alpha(1)-beta association is based on multiple interaction sites.

Amino Acid Sequence↗

PubMed2000

Preoperative radiochemotherapy in locally advanced or recurrent rectal cancer: regional radiofrequency hyperthermia correlates with clinical parameters.

PURPOSE: Preoperative radiochemotherapy (RCT) is a widely used means of treatment for patients suffering from primary, locally advanced, or recurrent rectal cancer. We evaluated the efficacy of treatment due to additional application of regional hyperthermia (HRCT) to this conventional therapy regime in a Phase II study, employing the annular phased-array system BSD-2000 (SIGMA-60 applicator). The clinical results of the trial were encouraging. We investigated the relationship between a variety of thermal and clinical parameters in order to assess the adequacy of thermometry, the effectiveness of hyperthermia therapy, and its potential contribution to clinical endpoints. METHODS AND MATERIALS: A preoperative combination of radiotherapy (1.8 Gy for 5 days a week, total dose 45 Gy applied over 5 weeks) and chemotherapy (low-dose 5-fluorouracil [5-FU] plus leucovorin in the first and fourth week) was administered to 37 patients with primary rectal cancer (PRC) and 18 patients with recurrent rectal cancer (RRC). Regional hyperthermia (RHT) was applied once a week prior to the daily irradiation fraction of 1.8 Gy. Temperatures were registered along rectal catheters using Bowman thermistors. Measurement points related to the tumor were specified after estimating the section of the catheter in near contact with the tumor. Three patients with local recurrence after abdominoperineal resection, had their catheters positioned transgluteally under CT guidance, where the section of the catheter related to the tumor was estimated from the CT scans. Index temperatures (especially T(max), T(90)) averaged over time, cumulative minutes (cum min) (here for T(90) > reference temperature 40.5 degrees C), and equivalent minutes (equ min) (with respect to 43 degrees C) were derived from repetitive temperature-position scans (5- to 10-min intervals) utilizing software specially developed for this purpose on a PC platform. Using the statistical software package SPSS a careful analysis was performed, not only of the variance of thermal parameters with respect to clinical criteria such as toxicity, response, and survival but also its dependency on tumor characteristics. RESULTS: The rate of resectability (89%) and response (59%) were high for the PRC group, and a clear positive correlation existed between index temperatures (T(90)) and thermal doses (cum min T(90) >/= 40.5 degrees C). Even though the overall 5-year survival was encouraging (60%) and significantly associated with response, there was no statistically significant relationship between temperature parameters and long-term survival for this limited number of patients. However, nonresectable tumors with higher thermal parameters (especially cum min T(90) >/= 40.5 degrees C) had a tendency for better overall survival. We found even higher temperatures in patients with recurrences (T(90) = 40.7 degrees C versus T(90) = 40.2 degrees C). However, these conditions for easier heating did not involve a favorable clinical outcome, since surgical resectability (22%) and response rate (28%) for the RRC group were low. We did not notice any other dependency of thermal parameters to a specific tumor or patient characteristics. Finally, neither acute toxicity (hot spots) induced by hyperthermia or RCT nor perioperative morbidity were correlated with temperature-derived parameters. Only a higher probability for the occurrence of hot spots was found during treatment with elevated power levels. CONCLUSION: In this study with two subgroups, i.e., patients with PRC (n = 37) and RRC (n = 18), there exists a positive interrelationship between thermal parameters (such as T(90), cum min T(90) >/= 40,5 degrees C) and clinical parameters concerning effectiveness. Additional hyperthermia treatment does not seem to enhance toxicity or subacute morbidity. Procedures to measure temperatures and to derive thermal parameters, as well as the hyperthermia technique itself appear adequate enough to classify heat treatments in

Age Factors↗

PubMed2000

Clinical evaluation and verification of the hyperthermia treatment planning system hyperplan.

PURPOSE: A prototype of the hyperthermia treatment planning system (HTPS) HyperPlan for the SIGMA-60 applicator (BSD Medical Corp., Salt Lake City, Utah, USA) has been evaluated with respect to clinical practicability and correctness. MATERIALS AND METHODS: HyperPlan modules extract tissue boundaries from computed tomography (CT) images to generate regular and tetrahedral grids as patient models, to calculate electric field (E-field) distributions, and to visualize three-dimensional data sets. The finite difference time-domain (FDTD) method is applied to calculate the specific absorption rate (SAR) inside the patient. Temperature distributions are calculated by a finite-element code and can be optimized. HyperPlan was tested on 6 patients with pelvic tumors. For verification, measured SAR values were compared with calculated SAR values. Furthermore, intracorporeal E-field scans were performed and compared with calculated profiles. RESULTS: The HTPS can be applied under clinical conditions. Measured absolute SAR (in W/kg), as well as relative E-field scans, correlated well with calculated values (+/-20%) using the contour-based FDTD method. Values calculated by applying the FDTD method directly on the voxel (CT) grid, were less well correlated with measured data. CONCLUSION: The HyperPlan system proved to be clinically feasible, and the results were quantitatively and qualitatively verified for the contour-based FDTD method.

Algorithms↗

PubMed2000

Dual regulation of the T-type Ca(2+) current by serum albumin and beta-estradiol in mammalian spermatogenic cells.

This study provides evidence for a novel mechanism of voltage-gated Ca(2+) channel regulation in mammalian spermatogenic cells by two agents that affect sperm capacitation and the acrosome reaction (AR). Patch-clamp experiments demonstrated that serum albumin induced an increase in Ca(2+) T current density in a concentration-dependent manner, and significant shifts in the voltage dependence of both steady-state activation and inactivation of the channels. These actions were not related to the ability of albumin to remove cholesterol from the membrane. In contrast, beta-estradiol significantly inhibited Ca(2+) channel activity in a concentration-dependent and essentially voltage-independent fashion. In mature sperm this dual regulation may influence capacitation and/or the AR.

Animals↗

PubMed2000

Electron-beam computed tomography in the assessment of coronary artery disease after heart transplantation.

BACKGROUND: Our aim was to compare the electron-beam CT (EBCT) features of coronary arteries in heart transplant recipients with those of biplane coronary angiography and intracoronary ultrasound (ICUS). METHODS AND RESULTS: We examined 112 heart transplant recipients (25 female; age, 17 to 69 years; median, 52 years) 1 to 153 months (median, 46 months) after surgery by EBCT to detect coronary artery calcifications. Calcifications were quantified by the Agatston scoring system. EBCT scores were compared with coronary angiography in all patients and ICUS of the left anterior descending coronary artery (LAD) in 100 patients. Coronary artery calcifications were found in 84 patients (75%). Angiographically, 16 patients displayed >50% coronary artery stenoses, all of whom had some degree of coronary artery calcification and only 1 of whom had a score of <55 (P<0.0001). With this threshold, EBCT had a sensitivity of 94%, a specificity of 79%, a positive predictive value of 43%, and a negative predictive value of 99% for detecting stenosis. ICUS confirmed the presence of calcified plaques in all patients with an LAD score >9. EBCT total calcium score was associated with the degree of intimal proliferation in that patients without ICUS features of allograft vasculopathy had a median score of 0 (25th percentile, 0; 75th percentile, 0), whereas patients with Stanford class IV vasculopathy had a median score of 41 (9 to 98, P<0.0001). CONCLUSIONS: EBCT is a promising noninvasive test for the detection of coronary heart disease in cardiac transplant recipients.

Adolescent↗