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R Felix

Publications and source records attributed to R Felix.

At least 361 records · Page 20Linked to original sources
PubMed1996

Failure of gadopentetate dimeglumine-enhanced, high-resolution magnetic resonance imaging to differentiate among melanin-containing skin tumors.

RATIONALE AND OBJECTIVES: We evaluated the diagnostic potential of gadopentetate dimeglumine-enhanced, high-resolution magnetic resonance (MR) imaging to differentiate benign from malignant melanin-containing skin tumors. METHODS: Forty-five patients were prospectively examined using high-resolution MR imaging at 1.5 T using a 2.5-cm surface coil. For tumor assessment, T1-weighted and T2-weighted transverse spin-echo sequences were acquired. After intravenous administration of gadopentetate dimeglumine (0.1 mmol/kg), the T1-weighted transverse sequence was repeated. Contrast enhancement was quantitatively determined as the percentage increase of signal intensity. Histologic findings were correlated using the Wilcoxon signed-ranks test. The quality of contrast enhancement was assessed by three independent investigators who were unaware of the patients' history and histologic data. The signal-to-noise ratio (SNR) was calculated in the T2-weighted sequence. Significance was tested using the Wilcoxon signed-ranks test. RESULTS: In all tumors, contrast enhancement was visually discernible. Half of the cases were enhanced inhomogeneously. The percentage of contrast enhancement did not correlate with histologic findings. Malignant melanomas could not be differentiated from benign melanocytic nevi with the use of gadopentetate dimeglumine. Determination of the SNR in T2-weighted sequences revealed no significant difference for histologic subgroups or tumor type. CONCLUSION: Gadopentetate dimeglumine-enhanced MR imaging does not differentiate malignant melanomas from benign melanocytic nevi. Determination of the SNR in the T2-weighted sequences revealed no significant difference for histologic subgroups.

Adolescent↗
PubMed1996

[3-D visualization of thoracic tumors from MR images].

AIM: In cooperation with the thoracic surgery department 3-D visualizations of tumors were generated to support the surgeons in preoperative planning. As opposed to 3-D reconstructions of CT data, those representations based on MRI images remain an exception. In this paper different methods of three dimensional visualization of lung tumors are presented and compared to each other. DESIGN: These methods are 1. contour based surface models, 2. threshold based surface models and 3. rendered scenes of segmented volume data with transparent, color-coded display. RESULTS: Combinations of all three methods in one single image are possible as well with the software we developed. Furthermore, cut planes through the original data can be integrated into the 3-D scene. The segmentation of anatomical objects is performed either manually or automatically with various procedures. CONCLUSIONS: Adequate possibilities of manipulation and archiving allow a fast handling and processing even of large data sets. The calculated volumes of the anatomical objects can be used for quantitative studies. Arbitrary views of the three dimensional reconstructions can be generated within a few seconds. Even animation can easily be calculated and displayed with 30 frames/second.

Adult↗
PubMed1996

[Duplex sonography in functional thyroid diagnosis].

PURPOSE: Assessment of the functional diagnostic value of Doppler sonographic or sonographic parameters, especially of the peak flow velocity in the inferior thyroid artery in patients with newly manifest autoimmunothyroiditis. MATERIAL AND METHOD: Morphological and Doppler sonographic measurements were done at the inferior thyroid artery on 69 patients suffering from newly manifest Graves' disease or Hashimoto's thyroiditis, as well as on a control group of 18 subjects. The measured data were correlated with thyroid hormone levels and with quantitative scintiscanning. RESULTS: A linear functional correlation was found between the peak flow velocities in the inferior thyroid artery and the fT3 or fT4 level. If the peak flow velocities were greater than 1.2 m/s, hyperthyroid metabolism prevailed, whereas at velocities below 0.3 m/s latent hypothyroidism was present. CONCLUSION: These results show that Doppler sonography of the inferior thyroid artery can supply pointers (capable of being recorded) to the state of functioning of the thyroid even before knowing the laboratory parameters.

Adult↗
PubMed1996

[MRT of the eye: the normal anatomy and detection of the smallest lesions with a high-resolution surface coil].

PURPOSE: A new, high-resolution surface coil for MRI of the eye was evaluated with regard to practicability, image quality and sensitivity for small lesions. MATERIAL AND METHODS: 48 patients in whom a space-occupying lesion of the eye or orbit was suspected were examined (1.5 T tomograph, 5 cm surface coil, T1- and T2-weighted spin-echo sequences, the former before and after i.v. gadolinium DTPA). RESULTS: 45/48 patients tolerated MR with the high-resolution surface coil. No adverse effects were experienced by the patients. In 11/48 patients a space occupying lesion of the eye was detected (melanoma, 5; metastases, 2; haemorrhage, 1; malformation, hamartoma and scarring after melanoma, one each). The smallest detectable lesion had a thickness of < 1 mm. CONCLUSION: First experiences with the high-resolution surface coil indicate that this device is suited for detection of very small lesions of the eye.

Adolescent↗
PubMed1996

[High-resolution magnetic resonance tomography by means of an endorectal coil--the results in rectal tumors].

PURPOSE: To assess the value of high-resolution MRI of the rectum using an endorectal coil. METHODS: 10 volunteers and in 31 patients with suspected rectal tumors were examined. In 17 patients (n = 17) with rectal carcinoma, of which 15 subsequently underwent radical surgery, the preoperatively obtained tumor stage was compared with histology. In 12 patients (n = 12) with rectal adenoma (severe and medium graded epithelial dysplasias according to the WHO) who underwent endoscopy the results of the endorectal surface coil examination were compared with endoscopy and histology. In 4 patients (n = 4) with large rectal adenomas the surface coil was used before and as follow-up after endoscopic electro laser resection and the absence of adenoma after therapy also in the deeper layers of the rectal wall could be confirmed. RESULTS: Visualization of anatomical structures of rectum and adjacent structures is improved by the use of the endorectal surface coil. The diagnosis of carcinoma and adenoma of the rectum and the documentation of the exact extension can be reached with high accuracy (85%). CONCLUSION: MRI with an endorectal surface coil may play an important role in the preoperative diagnosis of rectal carcinoma. This method is useful for primary diagnosis and follow-up of large rectal adenoma after endoscopic electro laser resection.

Adenoma↗
PubMed1996

[Radiation exposure in interventional radiology as exemplified by the chemoembolization of hepatocellular carcinoma and laser angioplasty of the pelvic arteries].

PURPOSE: Estimation of radiogenic risks for patient and radiologist in chemoembolisation of hepatocellular carcinoma (HCC) and laser angioplasty of the pelvic arteries. METHODS: In 5 chemoembolisations of HCC (4 males, one female) and 6 laser angioplasties of the pelvic arteries (5 males, one female) the surface doses received by patient and operator were measured using thermoluminescent dosimeters in standardised positions. The organ doses of the patient were derived by conversion factors employed on the measured surface doses. Effective dose was determined according to the recommendations of ICRP 60. RESULTS: The risk of lethal malignant disease and genetic disorder derived from the doses in the patient was found to be of the magnitude of 10(-4)-10(-5). The thresholds for transient erythema of the skin and depression of hematopoiesis can be reached after high expositions. A theoretical maximum of 700 laser angioplasties of the pelvic arteries allowable in one year was calculated based on the dose to the operator's left hand. For chemoembolisation of HCC, the dose to the left eye lens would reach the yearly maximum after approximately 1000 procedures. Remarkable risks for malignant disease of skin and thyroid as well as detectable opacities of the eye lens can occur after frequent interventions for many years. CONCLUSIONS: Because of the lower life expectancy the patient's risk for stochastic effect can be seen as minimal. No clinically relevant deterministic effects will occur. In the case of frequent interventions, the dose absorbed by the radiologist is likely to exceed the prescribed dose limit and to cause remarkable risk for stochastic and non-stochastic effects after many years.

Aged↗
PubMed1996

[Calculated organ doses and effective dosage for computerized tomography examination of the thorax and abdomen: are these doses realistic?].

PURPOSE: To analyse how far dose calculations for the CT examination of the thorax and abdomen can lead to faulty estimations of organ doses and effective dose due to differences in the topographic anatomy between mathematical phantom and man. METHODS: For the CT examination of the thorax, upper abdomen, pancreas, pelvis and the entire abdomen, organ doses were calculated with conversion factors, first with regard to the topographic relation within the phantom, then with additional regard to the real anatomy of the man. RESULTS: In the phantom, the abdomen lies outside the scan volume in case of CT-examination of the thorax and the whole intestine outside the scan volume in case of CT-examination of the upper abdomen and the pancreas, whereas the entire intestine is directly exposed in case of CT-examination of the pelvis. Dependent on whether dose calculations take real anatomy into account, doses of special organs can differ by a factor greater than 15. The calculated effective doses differ by a factor less than 1.5. CONCLUSIONS: Calculations of organ doses for the CT examination of the thorax and abdomen can lead to considerable errors due to different topographic relations between phantom and man. In contrast the calculated effective dose is realistic. Hence, dose calculations with the help of mathematical phantom is an efficient method to estimate the total radiogenic risk.

Female↗
PubMed1996

[Early clinical experiences with MR-guided laser-induced thermotherapy (LITT) of liver metastases in preoperative care].

PURPOSE: To evaluate the LITT-induced changes with the aid of MRT and correlate these with histopathological findings. MATERIAL AND METHODS: Five patients with solitary colorectal liver metastases were treated by means of MR-guided LITT before liver resection. Application time and energy of the Nd:YAG laser (1064 nm) was 10-20 minutes and 4.5-8.8 W. MRT monitoring during the LITT was carried out with temperature-sensitive T1 weighted sequences (FLASH-2-D, turbo FLASH). The extent of the induced necrosis as seen on MR was compared with the unfixed specimen and with the histopathological findings. RESULTS: The extent of necrosis visible by MRT correlated with the histopathological findings with an accuracy of 95.3% +/- 4.2%. Following single treatments (three cases) the metastases suffered a reduction of 24%-55% of their original volume. In two patients a second application produced laser-induced necrosis of 78% and 98% of volume. In these two patients a temperature sound was used for measuring regional heating and showed an exact correlation with MR thermometry. CONCLUSION: The results of pre-operative MR-guided LITT indicates the potential of this form of treatment for obtaining reproducible tumor necrosis of liver metastases.

Aged↗
PubMed1996

[Magnetic resonance tomography in patients with Parkinson's disease and Parkinson-plus syndromes].

PURPOSE: To define characteristic MR-findings in patients with clinically typical extrapyramidal movement disorders. METHODS: 15 patients with Parkinson's disease (PD), 9 with multisystem atrophy (MSA), and 6 with progressive supranuclear palsy (PSP) underwent MRI using a 1.5 T. Magnetom unit. Two investigators analysed the images with special regard to global and/or focal atrophy and to changes in signal intensity of the CNS in the consensus mode. Normal images of 10 subjects served as controls to patient's images. RESULTS: In all patients with PSP and MSA characteristic pathological findings on MRI were observed including regional changes within the extrapyramidal nuclei. In contrast all patients with PD had an unremarkable MRI study of the CNS. CONCLUSION: MRI enables us to define characteristic morphological changes of the brain in patients with extrapyramidal movement disorders. Early recognition of these findings avoids misdiagnoses in patients who are difficult to diagnose.

Adult↗
PubMed1996

[Teleradiology: use of multimedia PC for access to electronic patient records and teleconsultation].

A PC-platform is presented using internet technology on Ethernet (local) or ISDN (external) for access to digital hospital infrastructures comprising electronic multimedia patient records integrating information systems of all clinical departments. In addition, a videoconferencing system is implemented for teleconsulting, and a document camera allows transmission of analogue data. In combination with the multimedia-PC. Ethernet as well as ISDN offer satisfying performance for transmission of medical data including images. In 20 cases, visualisation of the electronic patient record, an average CT with report and 58 GIFF Images', or transfer of an ACR-NEMA file from CT, took seconds (Ethernet) or up to 3.5 minutes (ISDN - 58 CT images and report).

Computer Communication Networks↗
PubMed1996

[Skull injury in childhood: comparison of ultrasonography with conventional X-rays and computerized tomography].

PURPOSE: The purpose of our study was to compare the value of ultrasound, conventional x-ray diagnosis and CT in detecting skull fractures and intracranial haemorrhage in children suffering from a head injury. MATERIAL AND METHODS: We examined 210 children who had a head injury. In all cases the calvarium was investigated by ultrasound using a 7.0 MHz linear transducer. In children with an open fontanel (n = 190) the cerebrum was screened additionally by ultrasound following a standard protocol. The sonographic findings were correlated to the x-ray examination (n = 21) and CT (n = 13). RESULTS: Ultrasound enabled diagnosis of linear calvarial fractures (n = 29), depressed fractures (n = 6) and intracranial haemorrhage (n = 8). X-Ray and CT examination confirmed the diagnosis of linear calvarial fractures in 16 cases, of depressed fractures in 6 cases. CT confirmed the sonographic diagnosis of intracranial haemorrhage in 8 cases. CONCLUSION: Ultrasound as a primary method can replace the conventional x-ray in detecting calvarial fracture and posttraumatic sequelae. Additional CT examination depends on the sonographic and neurological status.

Age Factors↗
PubMed1996

[Intravenous spiral CT angiography for assessment before orthotopic liver transplantation: comparisons between tomography, MIP, 3-dimensional surface imaging and intra-arterial DSA].

UNLABELLED: To analyse the efficacy of intravenous spiral CT angiography (SCTA) for the evaluation before orthotopic liver transplantation (oLT) compared with DSA. METHODS: Spiral CT was performed on 31 potential recipients of a liver graft in order to examine hepatic vessels, coeliac axis, splenic artery and superior mesenteric artery. The arterial vessels were reconstructed in "Maximum Intensity Projection (MIP)" and "Shaded Surface Display (SSD)"-technique. The axial images, MIP and SSD were compared in 25 patients with DSA with regard to the visualisation of the vascular anatomy, detectability of stenosis and vascular diameters. RESULTS: The type of arterial liver supply could be determined via SCTA in all patients. Stenosis of the coeliac axis was seen in ten patients on the DSA, MIP and SSD and in eight patients on the axial images. Occlusion of the hepatic artery was clearly visualised in two patients on the DSA, axial images and MIP and in one patient on the SSD. There was no false positive diagnosis with SCTA. SSD was seen as the best technique to visualise the vessels without overshadowing. There were no significant differences between the diameters measured from the axial images, MIP and SSD images in transversal direction and the DSA images (p > 0.05). CONCLUSION: SCTA is a greatly promising method for the imaging of vessels supplying the liver before oLT, and may convey more diagnostic information than DSA.

Adult↗
PubMed1996

[The efficacy of lead shielding in patient dosage reduction in computed tomography].

PURPOSE: Investigation of the efficacy of lead apron, testis capsule and thyroid collar for dose reduction in uterus, ovaries, testes and thyroid gland in computed tomography examinations. METHODS: At an Alderson-Rando phantom dose of uterus, ovaries, testes and thyroid gland was measured with thermoluminescent dose meters. CT of the upper abdomen, the whole abdomen and the skull were simulated without and with lead shielding. As lead shielding, a lead apron was attached around the pelvis of the phantom in case of CT of the upper abdomen, a testis capsule was used in CT of the whole abdomen and a thyroid collar in CT of the skull. RESULTS: In CT of the upper abdomen the lead apron did not lead to any recognisable dose reduction in uterus and ovaries. In CT of the whole abdomen the testis capsule led to a dose reduction in testes of 95% (1.39 mSv) and in CT of the skull the thyroid collar to a dose reduction in thyroid gland of 23% (0.19 mSv). CONCLUSIONS: In abdominal CT examinations the testis capsule is an important instrument to reduce the dose of the testes whereas the lead apron is not appropriate for a dose reduction in the uterus and ovaries. In CT of the skull the thyroid collar can remarkably reduce the scattered radiation exposure of the thyroid gland and should be recommended.

Female↗
PubMed1996

[Can the high-resolution 13-MHz ultrasonography facilitate the preoperative localization and marking of microcalcification clusters?].

PURPOSE: The value of 13 MHz ultrasound regarding the preoperative localisation in combination with mammography were investigated into. MATERIAL AND METHOD: Out of 112 mammaographically detected calcifications, 30 (30 patients) were clusters of microcalcifications. Out of these, 23 were classified as suspicious of malignancy and were preoperatively localised with a 7.5 and 13 MHz probe. Upon marking the skin, a fine needle was inserted, and after due correction blue dye or coal solution was instilled. RESULTS: Following mammographically shown position, 23 clusters of microcalcifications could be localised using the 13 MHz probe. A localisation with the 7.5 MHz probe was impossible in all cases. A single correction of the needle's site was necessary with 35% (8/23) of patients. The maximum distance of the needle's tip in case of misposition measured 11 mm. CONCLUSION: Giving a known mammographic position and a sonographic perceptibility of clusters of microcalcifications in a maximal depth of penetration of 2 cm, 13 MHz high resolution ultrasound examination in combination with mammography prove to be a valuable means in facilitating the preoperative localisation.

Breast Diseases↗
PubMed1996

[Experimental results of excimer-laser-PTA in an experimental ex vivo vascular model].

PURPOSE: To evaluate parameters and characteristics of excimer-laser-angioplasty on ex-vivo vessel models. MATERIAL AND METHODS: 450 tissue ablations were performed on pig aortas, human arteries and fibrin-fixed plaque material. A pulsed 308nm-XeCl-laser delivering 120 ns pulses was tested. Ablations were analysed depending on frequency (10-40 Hz), energy density (30-70 ml/mm2), catheter-material-angle (0-90 degrees) and object-catheter-distance (0-40 mm). RESULTS: Vessel recanalisation speeds of up to 0.5 mm/s were achieved on fibrosed to slightly calcified human vessel models. In perforation tests on normal to slightly fibrosed human vessel walls and vessels of pigs ablation speeds of 0.01-0.5 mm/s were measured. Perforations on calcified vessels were successful in 50% of cases after two minutes application time. Vessel perforations were not detected without the support of mechanical power. At catheter-material angles < or = 30 degrees a minor damage of the intima could be found. There was no evidence of necrosis or coagulation in our studies. CONCLUSION: In-vitro tests of human plaque material yield reproducible vessel recanalisation distances of up to 25 mm at a variable speed from 0.1-0.2 mm/s.

Angioplasty, Laser↗
PubMed1996

Keratinization and necrosis. Morphologic aspects of lymphatic metastases in ultrasound.

RATIONALE AND OBJECTIVE: The authors performed a retrospective study in ultrasound to investigate new aspects in the sonomorphology of lymph node metastases of the neck. In this study, it could be demonstrated the first time that the histologic characteristics of the metastases determine the sonographic appearance. In addition to criteria such as the longitudinal/ transversal quotient, sonomorphology could support a more precise differential diagnosis of neck lymph nodes. METHODS: In 105 of 145 patients with histologically proved head and neck carcinomas, 187 lymph node metastases were detected by ultrasound. Sonomorphology was compared with the corresponding histology. RESULTS: Five sonomorphologic groups could be differentiated. (1) Thirty-one percent of the metastases were homogenous. (2) Concerning the more complex morphology of lymph node metastases in ultrasound, echolucent forms could be differentiated from echogenic textures: low- or nondifferentiated and nonkeratinizing metastases appeared echolucent and cyst-like, with dorsal signal amplification. (3) Nonkeratinizing lymphomas with necrosis showed single or multiple echolucent intranodal lesions. (4) In correlation with an increasing keratinization, the echogenecity of the lymph nodes increased and intranodal echogenic inclusions appeared. (5) An extended keratinization correlated with a central echogenecity. CONCLUSIONS: The morphologic assessment of lymph nodes in ultrasound allows for primary histologic and prognostic evaluation of lymph node metastases.

Aged↗