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Biomedical subjects

R Felix

Publications and source records attributed to R Felix.

At least 217 records · Page 12Linked to original sources
PubMed1999

[Diagnostic value of signal-enhanced color Doppler ultrasound in space-occupying lesions of the skin and skin appendages].

PURPOSE: Prospective evaluation of the diagnostic outcome of plain and signal-enhanced color Doppler sonography for the differentiation between benign and malignant cutis-involving lesions. MATERIALS AND METHODS: 39 patients with 40 suspected malignant skin lesions received an preoperative ultrasound examination before and after application of 4 g Levovist i.v. Spectral Doppler, conventional color and power Doppler were performed. The images were analyzed semiquantitatively using a specially developed software. The diagnoses were confirmed by histological analysis (37 cases) or by follow up controls (3 cases). RESULTS: Whereas the B-mode criteria such as echogenoity, borderline and homogenecity, and the spectral Doppler analysis were not useful for differentiation between malignant and benign lesions, the analysis of the intratumorously visible number of vessels and of the ratio of the vascularized area using a special software, especially after injection of the signal enhancing agent, provided valuable information. In 10 of 18 benign but only in 1 of 22 malignant lesions, no intratumorous vessels were visible after application of Levovist (plain: 10/18 benign and 6/22 malignant lesions). The number of visible vessels increased strongly after signal enhancement. Using a "ratio of the vascularized area (percentage vessel area) > 5%" as a criterion of malignancy, 2 false positive and 2 false negative results were observed after application of Levovist (without/with Levovist sensitivity 73%/91%, specificity 89%/89%). CONCLUSIONS: The signal-enhanced color Doppler sonography provides useful additional information for the differentiation between benign and malignant cutis-involving lesions, especially the semiquantitative vascularization analysis. The latter is superior to B-mode ultrasound and to spectral Doppler analysis. The signal enhancer increases the sensitivity, whereas the specificity remains unchanged.

Adolescent↗
PubMed1999

[Fat-saturated, contrast-enhanced spin-echo sequences in the magnetic resonance tomographic diagnosis of peritoneal carcinosis].

PURPOSE: To evaluate contrast-enhanced, fat-saturated spin echo sequences for the detection of peritoneal carcinosis with MRI. MATERIALS AND METHODS: 61 patients, 35 with and 26 without peritoneal carcinosis, were examined with abdominal MRI. Fat-saturated, T1-weighted spin echo sequences were performed before and after administration of Gd-DTPA. In addition, 22 patients with peritoneal carcinosis were examined with contrast-enhanced abdominal CT. RESULTS: 32 of 35 patients with peritoneal carcinosis demonstrated contrast enhancement of the visceral and 30 of 35 enhancement of the parietal peritoneum (91 and 86%, respectively). Wall thickening of the intestine or parietal peritoneum were noted in 21 and 20 of 35 patients (60 and 57%, respectively), ascites in 18 of 35 patients (51%). False positive contrast enhancement of the peritoneum was noted in 4 of 26 patients (15%). In the direct comparison of MRI and CT, 22 of 22 patients versus 7 of 22 patients showed contrast enhancement of the visceral peritoneum (100 and 32%, respectively). For other signs of peritoneal carcinosis (e.g., ascites, peritoneal seedings), no differences in diagnostic reliability were demonstrated. CONCLUSIONS: The use of fat-saturated, spin echo sequences facilitates the diagnosis of peritoneal carcinosis by artifact reduction and improved detection of peritoneal contrast enhancement. MRI with fat-saturated sequences was superior to CT.

Adult↗
PubMed1999

[Project graph technique for time management in abdominal ultrasound evaluations].

PURPOSE: German insurance companies are cutting down the time required for ultrasound examinations. To determine the minimal examination time to perform an ultrasound examination a project graph technique was applied. MATERIALS AND METHODS: Time measurements of abdominal ultrasound examinations were performed by two independent observers. The different jobs for the performance of an ultrasound examination were determined and the critical pathway method applied. The total available time for abdominal ultrasound examinations (leeway) was determined, the minimal time to perform each job was measured and the critical time required for the procedure was calculated. RESULTS: 14 different jobs were identified to complete one abdominal ultrasound examination. The project graph displayed the shortest possible time of 24 minutes to perform an ultrasound examination. The pure ultrasound exam without colour Doppler examination was 6 minutes ("hands on the ultrasound probe"). The jobs performed by the physician were fully within the critical period. In consequence, the physician had no leeway or time lag in relation to a total time of 24 minutes for an ultrasound examination, whereas by contrast the nurse has a total leeway of 7.5 minutes. CONCLUSIONS: The applied project graph technique is an effective instrument for the purpose of quality management for hospitals as well as in private practice. The workflow and actions necessary to perform a treatment or examination can be analysed. Human resources management and cost planning should be performed on the basis of project graphs.

Abdomen↗
PubMed1999

[Retroperitoneal recurrence of non-seminomatous testicular tumors: computerized tomography findings before retroperitoneal lymph node excision].

PURPOSE: In relapsing testicular cancer, additional chemotherapy is followed by abdominal CT. If residual lesions are found, retroperitoneal lymphadenectomy is considered. We studied retrospectively whether morphological criteria can help in selected cases in deciding about lymphadenectomy by distinguishing between vital tumor, scarring and mature teratoma. METHODS: In 26 patients who had been treated by salvage chemotherapy and retroperitoneal lymphadenectomy for non-seminomatous testicular cancer between 1990 and 1997, abdominal computed tomography and histology were correlated. RESULTS: Histological examination found scarring in 10 patients, vital tumor in 6, mature teratoma in 4, and simultaneous teratoma and vital tumor in 6. A single CT criterion for distinguishing between these histologies was not identified. In two patients with large masses which were partly cystic and partly solid vital tumor and teratoma were verified. Scarrings may be expected in cystic lesions at the level of the renal hilus which are lined by a thin and smooth wall. Size did not matter. CONCLUSION: Accurate differentiation between vital tumor and necrosis was not possible. Before lymphadenectomy CT, however, localised lesions.

Adolescent↗
PubMed1999

[PTLA (percutaneous transluminal laser angioplasty) recanalization of femoral artery stenoses/occlusions after Angio-Seal administration].

PURPOSE: To demonstrate desobliration of Angio-Seal-induced femoral artery stenosis and occlusion by Excimer-laser assisted angioplasty and PTA. PATIENTS AND METHODS: The Angio-Seal hemostatic closure device was applied to the puncture site in 1500 patients after diagnostic or therapeutic coronary artery catheterisation. In 5 of 1500 cases symptoms of claudication occurred. Following the determination of the walking distance and ankle-brachial systolic pressure index (ABI) and diagnostic angiography, therapeutic percutaneous transluminal laser angioplasty (PTLA) and PTA was performed. RESULTS: 5 patients with acute symptoms of peripheral artery disease presented with superficial femoral artery occlusions (three cases) and high grade stenoses of the common femoral arteries (two cases). Angiographic and clinical improvement was achieved after PTLA/PTA in all five patients. The mean walking distance increased from 61 meters to 600 meters. The average ankle-brachial systolic pressure index increased from 0.40 to 0.82. CONCLUSIONS: PTLA/PTA is a satisfactory therapeutic method for femoral artery occlusion or high-grade stenosis following Angio-Seal application.

Aged↗
PubMed1999

[The extracapsular spread of cervical lymph node metastases: the diagnostic value of computed tomography].

OBJECTIVE: To assess the value of computed tomography in the determination of extracapsular neoplastic spread and soft tissue infiltration of cervical lymph nodes. MATERIALS AND METHODS: Prospectively 165 CT reports of patients with squamous cell carcinoma in the head-neck region were compared with the histologic specimens after neck dissection. RESULTS: CT reached a sensitivity of 80.9% in the determination of extra-capsular neoplastic spread. The infiltration of cervical muscles and the jugular vein was always determined but-often diagnosed false-positive. Therefore, the overall specificity in determining extracapsular neoplastic spread was low with 72.7%. CONCLUSIONS: The accuracy of computed tomography (76.3%) in the determination of extracapsular neoplastic spread, infiltration of cervical muscles and the jugular vein is only partially satisfying.

Carcinoma, Squamous Cell↗
PubMed1999

High-resolution magnetic resonance imaging in patients with facial haemiatrophy.

The aim of this clinical study was to evaluate the use of high-resolution magnetic resonance imaging (MRI) in the diagnosis of facial haemiatrophy. A total of 14 patients with clinically suspected facial haemiatrophy were investigated using high-resolution MRI. The T1- (500/25) and T2- (2200/50) weighted images were analysed visually and numerically. The results of the affected skin portions were compared with the contralateral skin and correlated with the clinical results. The subcutis could not be delineated by high-resolution MRI in 9 patients with facial haemiatrophy. The dermis was not discernible in 6 cases and was "smooth" in a further 6 patients. The signal-to-noise ratio of affected skin portions and contralateral skin or clinical severity did not correlate. The higher the clinical severity, the more pronounced was the magnetic resonance ratio between dermis and subcutis thickness. Thus high-resolution MRI is a useful method for objective description of pathological changes in clinically suspected facial haemiatrophy.

Adult↗
PubMed1999

Muscle metabolism of professional athletes using 31P-spectroscopy.

PURPOSE: The aim of the study was to examine muscle metabolism in athletes by 31P-spectroscopy (MRS) and to evaluate to what degree the respective resonance spectrum correlates with the kind of muscle exercise. MATERIAL AND METHODS: Twelve runners and 12 young ice skaters were studied by 31P-spectroscopy of the gastrocnemic medialis muscle and the vastus medialis muscle using a surface coil at 1.5 T. RESULTS: Sprinters displayed a higher phosphocreatinine/inorganic phosphate (PCr/Pi) and PCr/beta-ATP ratios than marathon runners. The respective parameters for middle distance runners were in between. Ice skaters could prospectively be divided into sprint- and long-distance runners by our results which correlated with the athletes' training performance. CONCLUSION: 31P-spectroscopy can evaluate the distribution of muscle fiber types. Thus, the athlete's potential for sprint- or long-distance running can be determined. Additional studies will have to demonstrate to what extent training may change muscle fiber distribution.

Adenosine Triphosphate↗
PubMed1999

Fast spectroscopic imaging for non-invasive thermometry using the Pr[MOE-DO3A] complex.

The praseodymium complex of 10-(2-methoxyethyl)-1,4,7,10-tetraaza-cyclododecane-1,4,7-tr iacetate) was evaluated as a temperature-sensitive contrast agent using the temperature dependence (approximately 0.12 ppm degrees C(-1)) of the chemical shift of its methoxy side group signal. Pr[MOE-DO3A] was employed in combination with spectroscopic imaging (SI) methods for the determination of spatially resolved 2D and 3D temperature distributions in phantoms. Conventional SI and fast echo planar SI sequences (EPSI) were implemented on a 4.7 T MR imaging system fulfilling the demands for non-invasive thermometry (NIT) with respect to thermal and temporal resolution, being <1 degree C and <20 s total measuring time, respectively. The sequences are based on a fast spin echo SI method taking into account the very short relaxation times of the Pr complex methoxy group (T1 = 28 ms, T2 = 13 ms) and its chemical shift difference (-24 ppm) from water. Calibration curves were measured in a uniformly heated water phantom and 2D SI methods were applied to dynamic heating experiments. The average differences between the temperatures measured via fibreoptic thermometer and those derived from the spectroscopic methods were < or =0.2 degrees C. Furthermore, 3D EPSI experiments with a 16 x 16 x 16 matrix size yielded temperature measurements within 17 s from voxels of size 3 x 3 x 3 mm3.

Calibration↗
PubMed1999

Comparison of four magnetic resonance methods for mapping small temperature changes.

Non-invasive detection of small temperature changes (< 1 degree C) is pivotal to the further advance of regional hyperthermia as a treatment modality for deep-seated tumours. Magnetic resonance (MR) thermography methods are considered to be a promising approach. Four methods exploiting temperature-dependent parameters were evaluated in phantom experiments. The investigated temperature indicators were spin-lattice relaxation time T1, diffusion coefficient D, shift of water proton resonance frequency (water PRF) and resonance frequency shift of the methoxy group of the praseodymium complex (Pr probe). The respective pulse sequences employed to detect temperature-dependent signal changes were the multiple readout single inversion recovery (T One by Multiple Read Out Pulses; TOMROP), the pulsed gradient spin echo (PGSE), the fast low-angle shot (FLASH) with phase difference reconstruction, and the classical chemical shift imaging (CSI). Applying these sequences, experiments were performed in two separate and consecutive steps. In the first step, calibration curves were recorded for all four methods. In the second step, applying these calibration data, maps of temperature changes were generated and verified. With the equal total acquisition time of approximately 4 min for all four methods, the uncertainties of temperature changes derived from the calibration curves were less than 1 degree C (Pr probe 0.11 degrees C, water PRF 0.22 degrees C, D 0.48 degrees C and T1 0.93 degrees C). The corresponding maps of temperature changes exhibited slightly higher errors but still in the range or less than 1 degree C (0.97 degrees C, 0.41 degrees C, 0.70 degrees C, 1.06 degrees C respectively). The calibration results indicate the Pr probe method to be most sensitive and accurate. However, this advantage could only be partially transferred to the thermographic maps because of the coarse 16 x 16 matrix of the classical CSI sequence. Therefore, at present the water PRF method appears to be most suitable for MR monitoring of small temperature changes during hyperthermia treatment.

Body Temperature↗
PubMed1999

Radiation exposure in spiral computed tomography. Dose distribution and dose reduction.

RATIONALE AND OBJECTIVES: The authors investigate the dose distribution of spiral and conventional computed tomography (CT) with film densitometry and to present a new method of evaluating the possibility of dose savings with spiral CT. METHODS: Films were exposed in a cuboid polymethyl-methacrylate phantom in conventional and spiral scan technique. Axial density profiles were obtained by digitizing the films using a fluorescent light scanner. The ratio of the number of rotations in spiral CT to the number of slices in conventional CT was calculated. RESULTS: In spiral CT with a pitch of 2, the densities in all points were lower than those in corresponding points in spiral CT with a pitch of 1 and in conventional CT with slice distance equal to slice thickness. A pitch of 1.5 in spiral CT led to a dose reduction of 14% to 30% compared with conventional CT. CONCLUSIONS: Increasing the pitch in spiral CT leads to a reduction of both integral dose and absorbed doses within the examined body region. The reduction of the integral dose can be significant, especially in cases where slice overlapping is diagnostically advantageous.

Humans↗
PubMed1999

D-galactose-based signal-enhanced color Doppler sonography of breast tumors and tumorlike lesions.

RATIONALE AND OBJECTIVES: This study sought to evaluate prospectively the diagnostic potential of unenhanced and enhanced color Doppler and power Doppler for the differentiation of tumors and tumorlike lesions of the breast. METHODS: Ninety-two patients with 110 tumors or tumorlike lesions of the breast were investigated by unenhanced and enhanced color and power Doppler ultrasound. The sonomorphologic aspects of vascularization were analyzed. In addition, maximal systolic frequency shift, resistance, and pulsatility indices were determined. RESULTS: In 15 (24%) of 63 primary carcinomas, 15 (68%) of 22 fibroadenomas, and all (100%) of 14 postoperative lesions, the sonomorphologic analysis for the differential diagnosis of breast tumors was improved after contrast enhancement in color Doppler mode. In comparing unenhanced color Doppler to power Doppler, the latter was found to be slightly superior (sensitivity, 60% vs. 67%; specificity, 39% vs. 45%, respectively); after enhancement, both modes were equivalent (sensitivity, 100% vs. 100%; specificity, 95% vs. 95%, respectively). Signal enhancement resulted in a significant improvement in sensitivity and specificity (P < 0.01). Typical signs of malignancy were irregular vessel calibers, serpiginous courses, penetration of the tumor's margin, and irregular reticular vascularization. The quantitative parameters proved not to be helpful for the differential diagnosis of breast tumors. CONCLUSIONS: By improved analysis of the vascularization pattern, d-galactose-enhanced color Doppler sonography was found to provide more reliable differential diagnostic information than unenhanced Doppler ultrasound in tumors and tumorlike lesions of the breast.

Adolescent↗
PubMed1999

Differential diagnosis of lymph node lesions. A semiquantitative approach with power Doppler sonography.

RATIONALE AND OBJECTIVES: To assess the value of power Doppler for distinguishing reactive from malignant lymph node disease. METHODS: In a prospective study, 48 untreated patients with palpable cervical lymph node enlargement (n = 211) underwent examination with power Doppler sonography. The perfusion sites were subdivided into three groups: central, peripheral, and hilar perfusion. In addition, the authors qualified the intensity of perfusion using a semiquantitative scale from 0 (no perfusion) to III (high perfusion). Finally, the overall perfused lymph node area was measured and the percentage of perfused nodal area was calculated. RESULTS: Power Doppler sonography showed perfusion in 183 of 211 lymph nodes. Histologic examination revealed 67 reactively enlarged lymph nodes, 72 metastases, and 44 lymphomas. Reactively enlarged lymph nodes showed characteristically intense hilar perfusion (82.1%), whereas nodal metastases exhibited mainly peripherally located flow (84.7%) of grade intensity I to III. Lymph nodes invaded by malignant lymphoma were highly perfused, displaying color signals in the center as well as in the nodal periphery (90.9%). CONCLUSIONS: The perfusion patterns of lymph nodes provide useful additional information in the differential diagnosis of cervical lymphadenopathy.

Adolescent↗
PubMed1999

Thoracic computed tomography of patients infected with the human immunodeficiency virus: relevance for the course of disease.

To determine the diagnostic accuracy and prognostic implications of thoracic computed tomography (CT) in patients with human immunodeficiency virus infection (HIV), CT scans of 154 HIV-infected patients (mean age, 41 years; range 23-65 years; 18 female) with suspicion of pulmonary disease were retrospectively reviewed for signs of disease by two investigators blinded to clinical data other than positive HIV serology. Abnormal CT features were correlated with CD4-T lymphocyte count, histologic or microbiologic diagnosis, and survival. Computed tomography detected features of pulmonary disease in 133 patients. A recent chest film was available in 96 patients, and it was normal in 16. In 17 of 99 patients (17%) with histologic or microbiologic correlation, pathologic CT features could be demonstrated, though histologic and microbiological studies were unrevealing. Median survival was 649 days. Confluent pulmonary infiltrates and bilateral masses on CT indicated advanced disease with a median survival of 115 days (n = 11, p = 0.0005) and 174 days (n = 15, p < 0.0001), respectively. The authors concluded that thoracic CT detects pulmonary lesions in an appreciable portion of HIV-infected patients in whom chest radiographs, microbiologic methods, or histology failed to establish a diagnosis, and that CT findings allow for an estimation of patient survival in acquired immunodeficiency syndrome.

Adult↗
PubMed1999

Radiologic anatomy of ventricular assist devices.

Ventricular assist devices (VAD) allow for long-term circulatory support of patients with end-stage heart failure. With the increasing duration of circulatory support, diagnostic imaging plays an important role in the management of patients on a VAD. The aim of our review was to analyze the radiologic features of different VADs. From 1987 to 1996, 319 patients (mean age 42 years, range 3 to 74 years) were treated with a VAD. A Berlin Heart VAD was implanted in 263 of the patients, the univentricular Baxtor Novacor was implanted in three patients, and the univentricular CI Heartmate was implanted in 19 patients. All patients were studied by serial chest radiographs. In addition, 70 patients underwent computed tomography (CT), and five patients underwent electron beam CT. The Berlin Heart VAD was used as a biventricular support system in 218 patients. In all cases, the position of the wire-directed cannulae was identified on the chest radiographs, while the exact position of the cannula tip could be visualized by CT only. The plastic cannulae of both the Novacor and the Heartmate were not discernible on radiographs, but required CT for evaluation. Computed tomography also resolved the metal components of the pumps. The titanium-made pump housing of the Heartmate caused beam-hardening artefacts that might conceal fluid accumulations in the pump pocket. Computed tomography is the standard of reference for examinations of cannula position, pump position, and pump components of ventricular assist devices.

Adolescent↗
PubMed1999

Visualization and registration of three-dimensional E-field distributions in annual-phased-array applicators.

A testing system is presented allowing registration, digitization, and evaluation of three-dimensional power distributions rendered by annular-phased-array applicators in homogeneous liquid media. The system is based on a lamp phantom originally developed to visualize power distributions. Now the brightness distribution is registered via a charge-coupled device camera and transferred to a PC-based evaluation system outside the shielding room. An appropriate mechanical coupling of camera and sensor matrix probing the phantom was built in order to keep optical image conditions constant under movement. For visualization and evaluation commercially customized software was employed. The evaluation of the system shows the linearity between sensor signal and power density magnitude to be sufficient for evaluation and graphical representation of three-dimensional data sets. In a first practical application the testing system was employed to evaluate dependencies of power distributions as a function of frequency and phase settings on temperatures and, subsequently, the relevance of those results for clinical hyperthermia in a SIGMA-60 applicator (BSD-2000 system). Now, the system is ready to evaluate more complex multiantenna array applicators like the SIGMA-Eye applicator. The measuring system is particularly suitable for a fast comparison of APA applicators applied for a homogeneous medium. Implications for heterogeneous structures (like in patients) are then possible via modeling calculations.

Calibration↗
PubMed1999

Effect of MALP-2, a lipopeptide from Mycoplasma fermentans, on bone resorption in vitro.

Mycoplasmas may be associated with rheumatoid arthritis in various animal hosts. In humans, mycoplasma arthritis has been recorded in association with hypogammaglobulinemia. Mycoplasma fermentans is one mycoplasma species considered to be involved in causing arthritis. To clarify which mycoplasmal compounds contribute to the inflammatory, bone-destructive processes in arthritis, we used a well-defined lipopeptide, 2-kDa macrophage-activating lipopeptide (MALP-2) from M. fermentans, as an example of a class of macrophage-activating compounds ubiquitous in mycoplasmas, to study its effects on bone resorption. MALP-2 stimulated osteoclast-mediated bone resorption in murine calvaria cultures, with a maximal effect at around 2 nM. Anti-inflammatory drugs inhibited MALP-2-mediated bone resorption by about 30%. This finding suggests that MALP-2 stimulates bone resorption partially by stimulating the formation of prostaglandins. Since interleukin-6 (IL-6) stimulates bone resorption, we investigated IL-6 production in cultured calvaria. MALP-2 stimulated the liberation of IL-6, while no tumor necrosis factor was detectable. Additionally, MALP-2 stimulated low levels of NO in calvaria cultures, an effect which was strongly increased in the presence of gamma interferon, causing an inhibition of bone resorption. MALP-2 stimulated the bone-resorbing activity of osteoclasts isolated from long bones of newborn rats and cultured on dentine slices without affecting their number. In bone marrow cultures, MALP-2 inhibited the formation of osteoclasts. It appears that MALP-2 has two opposing effects: it increases the bone resorption in bone tissue by stimulation of mature osteoclasts but inhibits the formation of new ones.

Animals↗