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At least 955 records · Page 53Linked to original sources
PubMed2000

Radio frequency perforation of cardiac tissue: modelling and experimental results.

Radio frequency (RF) current delivered through a thin catheter can be used to perforate the pulmonary valve or the atrial septum to treat pulmonary atresia in newborns. To understand better the mechanisms of RF perforation, a numerical model is developed, and experiments are performed in isolated canine cardiac tissue. The model consists of a cylindrical domain with a tissue layer between two blood layers. The finite-difference method is used to compute both the potential and temperature distributions. When the tissue temperature exceeds 100 degrees C in all points that are directly in front of the catheter, these points are considered to be instantly vaporised, and the catheter advances over these points. The computed temperature time course coincides with measured temperature at small voltages (< 16 V). Simulated perforation occurs when the voltage exceeds a threshold of 70-80 V for a catheter diameter of 0.30-0.44 mm, which coincides with experimental observations in the myocardium. A voltage exceeding this perforation threshold tends to decrease tissue damage. Shorter electrodes (0.7 mm as against 2.4 mm) with smaller diameters produce a more rapid perforation. In conclusion, numerical simulations provide insights into aspects of RF perforation, such as electrode size, current, speed of perforation and collateral damage.

Animals↗
PubMed1986

Radio-anatomic study of the carotid axis with regard to the implantation of microsurgical vascular anastomoses.

The authors report a radio-anatomic study of the carotid axis in the context of the implantation of microsurgical vascular anastomoses. The information derived from 36 dissections and 50 arteriographic studies suggests the preferential use of the superior thyroid, facial and lingual branches. Section and turning-down of the external carotid and direct end-to-side implantation on the common carotid could provide fall-back solutions when the collaterals are slender. Because of anatomic variations and frequent atheromatous lesions, arteriographic study before implantation appears essential.

Adult↗
PubMed1999

Thermal distribution of radio-frequency inductive hyperthermia using an inductive aperture-type applicator: evaluation of the effect of tumour size and depth.

A new radio-frequency (RF) inductive hyperthermia device using an inductive aperture-type applicator (IATA) is proposed. This paper reports the evaluation of the heating characteristics of the IATA using a computer simulation and clinical thermal parameters obtained during treatment of superficial and subsurface-seated tumours. The configuration of the IATA is a one-turn square column-like coil whose bottom plate is set to face the heating target. The IATA has advantages over RF capacitive-type heating, such as: generating less heat in the subcutaneous fat layer; less convergency of electric line of force at the edge of the applicator; and no physical contact with the target lesion. The induced magnetic fields and electrical currents within the heating substance are simulated using computer-assisted design software for electro-magnetic analysis. A total of 40 superficial and subsurface tumours are treated with the IATA. Invasive thermometry is performed continuously for 110 sessions using multi-sensor probes of an optical thermometer. Thermal parameters (Tmax, Tmin, Tave) are assessed based on the tumour size and depth. The treated tumours are categorised into three groups according to tumour depth: group 1 (< 3 cm, n = 28), group 2 (3-5 cm, n = 35) and group 3 (> 5 cm, n = 47). The computer simulation shows that induced electrical currents run without convergency, parallel to the surface of the heating material. All thermal parameters of group 3 are significantly higher than those of group 1 and 2 (p < 0.05), indicating that the larger lesions tend to abtain a higher temperature distribution. In conclusion, RF inductive hyperthermia using the IATA results in effective temperature distributions in superficial and subsurface tumours, with large tumours being most effectively heated.

Aged↗
PubMed1994

Radio-immunotherapy dosimetry with special emphasis on SPECT quantification and extracorporeal immuno-adsorption.

Results from therapeutic trials with radiolabelled monoclonal antibodies are difficult to compare, because of lack of accurate macroscopic and microscopic dosimetry for both tumours and normal tissues. Requirements for such a dosimetry are covered in the paper. Accurate in vivo dosimetric measurement techniques for verification of calculated absorbed doses are also needed to verify treatment planning. In the review, important topics related to dosimetry in therapeutic trials in RIT are covered, such as, absorbed-dose calculations and activity-quantification techniques for planar imaging and SPECT. The latter is particularly discussed, including a summary of different correction techniques. Absorbed-dose calculations and treatment-planning techniques are also discussed. Possible ways of enhancing the therapeutic ratio are reviewed, especially the novel technique with extracorporeal immuno-adsorption. The review could form the basis of the development of future treatment-planning protocols and for dosimetry calculations in radio-immunotherapy, considering some of the most important parameters for approaching an accurate in vivo dosimetry.

Antibodies, Monoclonal↗
PubMed1993

Profiling of arachidonic acid metabolites in rabbit platelets by radio gas chromatography.

A method for profiling arachidonic acid metabolites by radio gas chromatography (GC) is described. The incubation mixture of rabbit platelets with [14C]arachidonic acid was purified on a Sep-Pak C18 cartridge and derivatized with diazomethane, O-methylhydroxylamine and dimethyl-isopropylsilylimidazole. The recovery of total 14C-radioactivity was 93.1 +/- 7.2%. Loss of radioactivity during derivatization was negligible. Baseline separations for [14C]arachidonic acid and its metabolites were obtained in a single run within 45 min by GC using a synchronized accumulating radioisotope detector (GC/SARD). The recovery of radioactivity from the GC column was virtually 100%. The chemical structures of the metabolites were confirmed by GC/mass spectrometry; peaks of arachidonic acid metabolites were assigned by comparison of the methylene unit values with those of radioactive peaks in GC/SARD analyses. The intra-assay coefficients of variation in GC/SARD analyses were less than 10%. The method was used to map the profile of arachidonic acid metabolites formed by rabbit platelets in the presence of indomethacin, baicalein or glutathione.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1997

Effect of erythromycin on gastric emptying in healthy individuals assessed by radio-opaque markers and plasma acetaminophen levels.

We simultaneously recorded gastric emptying of radio-opaque markers (ROMs) and monitored serial changes in plasma acetaminophen (AAP) levels to demonstrate the relationship between the ROM and the AAP methods, and we investigated the effect of a single intravenous dose of erythromycin (EM) on gastric emptying in healthy human subjects. After an overnight fast, subjects were randomized to receive either placebo or EM lactobionate (Abbott, North Chicago, IL, USA) 250 mg intravenously in a single dose, given immediately before a standard meal. Subjects ingested 1.5 g of AAP and ROMs with the test meal. A supine plain abdominal radiograph was taken 1, 2, 3, and 6 h after ingestion of the test meal. Peripheral blood samples were obtained 0, 0.5, 1, 1.5, 2, 3, and 6 h after ingestion of the test meal. EM significantly accelerated gastric emptying of ROMs. By 6 h, no markers remained in the stomach in any of the subjects in the placebo or EM groups. By 120 min, half of the ROMs had passed into the duodenum in 12.5% of subjects after placebo, whereas EM injection resulted in gastric emptying of half of the ROMs in all subjects. There was no difference in plasma AAP concentration between the placebo and EM groups. There were significant correlations between maximum plasma AAP concentration and gastric emptying of ROMs 120 min after ingestion (r = 0.546; P = 0.019), and between time of maximum plasma AAP concentration and gastric emptying of ROMs 120 min after ingestion (r = -0.568; P = 0.014). The time taken to reach the peak concentrations ranged from 30 to 90 min after ingestion, whereas most ROMs were emptied 120 min after ingestion. We conclude that the gastric emptying assessed by ROMs and by serial changes in plasma AAP level are good, non-invasive, clinically applicable tests, with a significant correlation between the two tests. A single intravenous dose of EM had a prokinetic effect on gastric emptying, assessed by ROMs, in healthy human subjects.

Acetaminophen↗
PubMed1993

Anaplastic carcinoma of the thyroid following radio-iodine therapy.

We describe a 79 year old lady who presented with a cytologically confirmed anaplastic carcinoma of the thyroid gland eleven years after administration of radio-iodine for thyrotoxicosis. This is, we believe, the first such occurrence documented in the Irish literature.

Aged↗
PubMed2004

Dendroremediation of trinitrotoluene (TNT). Part 2: fate of radio-labelled TNT in trees.

BACKGROUND, AIM AND SCOPE: Problems of long-term existence of the environmental contaminant 2,4,6-trinitrotoluene (TNT) and necessities for the use of trees ('dendroremediation') in sustainable phytoremediation strategies for TNT are described in the first part of this paper. Aims of the second part are estimation of [14C]-TNT uptake, localisation of TNT-derived radioactivity in mature tree tissues, and the determination of the degree of TNT-degradation during dendroremediation processes. METHODS: Four-year-old trees of hybrid willow (Salix spec., clone EW-20) and of Norway spruce (Picea abies) were cultivated in sand or ammunition plant soil (AP-soil) in wick supplied growth vessels. Trees were exposed to a single pulse application with water solved [U-14C]-TNT reaching a calculated initial concentration of 5.2 mg TNT per kg dry soil. Two months after application overall radioactivity and extractability of 14C were determined in sand/soil, roots, stem-wood, stem-bark, branches, leaves, needles, and Picea May sprouts. Root extracts were analysed by radio TLC. RESULTS: 60 days after [14C]-TNT application, recovered 14C is accumulated in roots (70% for sand variants, 34% for AP-soil variant). 15-28% of 14C remained in sand and 61% in AP-soil. 3.3 to 14.4% of 14C were located in aboveground tree portions. Above-ground distribution of 14C differed considerably between the angiosperm Salix and the gymnosperm Picea. In Salix, nearly half of above-ground-14C was detected in bark-free wood, whereas in Picea older needles contained most of the above-ground-14C (54-69%). TNT was readily transformed in tree tissue. Approximately 80% of 14C was non-extractably bound in roots, stems, wood, and leaves or needles. Only quantitatively less important stem-bark of Salix and Picea and May shoots of Picea showed higher extraction yields (up to 56%). DISCUSSION: Pulse application of [14C]-TNT provided evidence for the first time that after TNT-exposure, in tree root extracts, no TNT and none of the known metabolites, mono-amino-dinitrotoluenes (ADNT), diaminonitrotoluenes (DANT), trinitrobenzene (TNB) and no dinitrotoluenes (DNTs) were present. Extractable portions of 14C were small and contained at least three unknown metabolites (or groups) for Salix. In Picea, four extractable metabolites (or groups) were detected, where only one metabolite (or group) seemed to be identical for Salix and Picea. All unknown extractables were of a very polar nature. CONCLUSIONS: Results of complete TNT-transformation in trees explain some of our previous findings with 'cold analytics', where no TNT and no ADNT-metabolites could be found in tissues of TNT-exposed Salix and Populus clones. It is concluded that 'cold' tissue analysis of tree organs is not suited for quantitative success control of phytoremediation in situ. RECOMMENDATIONS AND OUTLOOK: Both short rotation Salicaceae trees and conifer forests possess a dendroremediation potential for TNT polluted soils. The degradation capacity and the large biomass of adult forest trees with their woody compartments of roots and stems may be utilized for detoxification of soil xenobiotics.

Biodegradation, Environmental↗
PubMed2004

The usefulness of radio-guided surgery in secondary hyperparathyroidism.

Recent reports have shown that radio-guided surgery with an intraoperative gamma probe (IGP) is useful for identifying parathyroid adenomas. The aim of this study was to evaluate the usefulness of IGP mapping in patients with secondary hyperparathyroidism. Seven patients with secondary hyperparathyroidism underwent technetium-99m methoxyisobutylisonitrile (Tc-99m MIBI) scintigraphy immediately before undergoing surgical resection of all parathyroid tissues. We compared the sensitivity of Tc-99m MIBI scintigraphy alone with that of the combination of Tc-99m MIBI scintigraphy and IGP mapping. The sensitivity of the combination of Tc-99m MIBI scintigraphy and IGP mapping was 100% (28 of 28 lesions) and was significantly higher than that of Tc-99m MIBI scintigraphy alone (71.4%, 20 of 28 lesions). The combination of the Tc-99m MIBI scintigraphy and IGP mapping has increased sensitivity for identifying parathyroid lesions during parathyroidectomy in patients with secondary hyperparathyroidism.

Adult↗
PubMed2001

Acute toxicity and changes in quality of life during a combined radio-chemotherapy of glioblastomas with topotecan (Hycamtin).

BACKGROUND: Because of the pronounced radioresistance of glioblastoma multiforme the prognosis of this disease remains poor. Therefore, we investigated the impact of an additional simultaneous chemotherapy with the topoisomerase-I inhibitor topotecan (Hycamtin) on the quality of life and toxicity of radiotherapy. PATIENTS AND METHODS: In this multicenter trial patients with histologically proven glioblastoma multiforme underwent a simultaneous radio-chemotherapy. Including pilot phase 60 patients, 41 male and 19 female, were treated. Age ranged from 26 to 76 years, the mean was 57 years. Conventional fractionated conformal radiotherapy was performed with daily doses of 2.0 Gy to a total dose of 60 Gy. 1 hour prior to irradiation 0.5 mg (absolute dose) of topotecan were administered intravenously resulting in a cumulative dose of 15 mg. Besides hematologic and non-hematologic toxicity, quality of life was assessed by Karnofsky index and Spitzer index. Additionally local control and survival time were recorded. RESULTS: 57 patients completed the combined therapy. Median administered dose of radiation was 60 Gy (16-76 Gy). Median cumulative topotecan dose was 15 mg (7.5-18.5 mg). Grade-III toxicity was found in six cases (two hematologic, two motoric disorder, one infection, one nausea) and grade-IV toxicity in three cases (one esophagitis, one motoric disorder, one mental disorder). Two patients died of septic disease most likely caused by steroid induced immunosuppression. Mean Karnofsky index and Spitzer index initially, at the end of therapy and 6 weeks after therapy showed values of 87%, 81% and 80% and 19 points, 18 points and 19 points, respectively. Median survival time was 15 months. CONCLUSION: This multimodal approach for patients with glioblastoma multiforme is well tolerated. Quality of life remains preserved and outpatient treatment is possible. The relatively long median survival time even for patients bearing macroscopic tumors is promising.

Adult↗
PubMed1999

Percutaneous ethanol injection and radio-frequency ablation for the treatment of nonresectable colorectal liver metastases - techniques and results.

BACKGROUND: Percutaneous ethanol injection (PEI) and radio-frequency (RF) ablation are possible palliative treatment modalities for patients with non-resectable liver metastases of colorectal carcinomas. The different techniques are explained and reviewed. RESULTS: PEI did not show promising results for the treatment of liver metastases. RF results were more encouraging; some studies showed improved mean survival times for patients when a complete necrosis of the metastases could be achieved. The maximum diameter of the necrotic area possible in a single session is about 5 cm. CONCLUSION: PEI and RF are palliative last-line treatment strategies for patients with non-resectable liver metastases and should only be applied if chemotherapy is not sufficient or not possible. The long-term efficacy of RF ablation in this group of patients has to be evaluated.

Catheter Ablation↗
PubMed2001

Results of surgery and radio-hyperthermo-chemotherapy for patients with soft-tissue sarcoma.

BACKGROUND: Between 1990 and 1999, we performed radio-hyperthermo-chemotherapy (RHC) in 44 patients with high-grade soft-tissue sarcomas of the limbs. METHODS: Radiotherapy involved the delivery of radiation at a dose of 2 Gy once daily on 16 days, to give a total dose of 32 Gy. Hyperthermia was conducted once a week, with a total of five sessions. Chemotherapy was performed by implanting a reservoir and administering cisplatin (3 mg/kg) three times, and pinorubin (an adriamycin derivative; 1 mg/kg) twice by intra-arterial infusion, at weekly intervals. These drugs were administered alternately during hyperthermia sessions. RESULTS: Tumor shrinkage was observed in 98% (43/44) of the patients. Of the 36 patients with M0 tumors, 30 were disease-free at final follow-up, 2 had no evidence of disease, 1 was alive with disease, and 3 had died of the disease. Amputation was required only in the first patient, and the affected limb was preserved in the other 43 patients. The surgical margin was wide in 9 patients and marginal in 29 patients, and intralesional excision was performed in 5 patients. There was recurrence in only 1 of the 44 patients. CONCLUSION: RHC is currently the most potent and relatively safe treatment method for high-grade soft-tissue sarcomas that is available clinically.

Adolescent↗
PubMed2002

Selective lymph node dissection following hyperfractionated accelerated radio-(chemo-)therapy for advanced head and neck cancer.

BACKGROUND: 2-year results of a German multicenter randomized trial showed that accelerated chemoradiation with MMC/5-FU to 70.6 Gy is more effective than accelerated radiation to 77.6 Gy alone at equivalent levels of acute and late radiation morbidity. Frequency, histopathology and impact on local tumor control of selective lymph node dissection were analyzed. PATIENTS AND METHODS: Between February 1996 and October 2000 at Tübingen University 42 randomized patients plus 45 non-randomized patients with stage III/IV MO head and neck cancer were treated according to this protocol. After completion of hyperfractionated accelerated (chemo-)radiation a selective lymph node dissection was performed, if the primary tumor was in complete remission and clinical plus computed tomography proved residual lymph node disease. 17 of 38 patients with residual node metastasis underwent uni- or bilateral selective node dissection, the remaining patients had residual primary tumors, clinical deterioration or refused neck dissection. RESULTS: After a median follow-up of 26 months, the Kaplan-Meier analysis showed a 2-year overall survival of 49%, disease-specific survival of 64% and loco-regional tumor control of 60%, respectively. 3-year loco-regional tumor control in randomized patients was 52% compared to 58% in non-randomized patients (log rank p = 0.23). 2-year loco-regional tumor control in stage cT4cN0 was 76% compared to 57% in cT2-4 cN1-3 tumors. Subgroup analysis of patients with involved nodes revealed a 2-year loco-regional tumor control of 74% after complete remission of primary tumor and neck disease, 53% after complete remission of primary tumor and partial remission of neck disease. In patients with selective lymph node dissection loco-regional tumor control was 62%. Histopathological examination showed viable tumor in eight of 17 patients. CONCLUSIONS: Selective lymph node dissection of residual neck masses after completion of hyperfractionated accelerated radio-(chemo-)therapy is likely to contribute to loco-regional tumor control in advanced head and neck cancer.

Adult↗
PubMed2004

[Present state of radio frequency ablation of liver tumors in Germany].

INTRODUCTION: Radio frequency ablation (RFA) represents a new technique for local destruction of liver tumors. Indication and procedure are poorly validated at present. METHOD: To record the actual nationwide RFA application in Germany, a survey of 2026 hospitals with standardized questionnaires was conducted. RESULTS: With a respond rate of 17.5%, results from 58 hospitals covering 1700 ablated patients were analyzed. In 25.9% of them, RFA is already used in potentially curative resectable tumors, in 22.4% even when incomplete ablation for tumor mass reduction is expected. Of the 58 hospitals, 75% combine resection and RFA to reach a so-called R-0 situation. The maximal tumor sizes they quoted for achieving complete ablation ranged from <3 cm to 11 cm. In contraindications for RFA, the tumor size, number of tumors, critical localization of the tumor, and disorders of liver function were mentioned the most. CONCLUSION: This survey documents significant discrepancies in indication, application, procedure, and results in RFA for liver tumors. The lack of general standards and an overestimation of the method may lead to uncritical application, neglect of standard therapy, or unsatisfying results.

Chemotherapy, Adjuvant↗
PubMed2002

Radio frequency glow discharge optical emission spectroscopy: a new weapon in the depth profiling arsenal.

While the array of analytical methods routinely applied for depth profile analysis was fairly static over the decades of the 1980s and 1990s, there appears to be an emerging technique that has a number of very positive and complementary attributes, and warrants serious consideration by the thin film community. Radio frequency glow discharge optical emission spectroscopy (rf-GD-OES) is a technique that provides depth-resolved elemental composition information on a wide variety of sample types. In a manner very much like most depth profiling methods, the rf-GD plasma utilizes an ion sputtering step to ablate sample material in a layer-by-layer fashion. Different from the more commonly applied methods, the device operates at elevated pressures [2-10 Torr Ar (266-1,330 Pa)] and has the inherent capability of sputtering electrically insulating materials directly, without any auxiliary means of charge compensation. In addition, sputtering rates on the order of 1 micro m/min provide rapid analysis, with depth resolving powers that are comparable to high-vacuum sputtering methods. Three examples of the use of the rf-GD-OES method are presented as examples of its analytical potential: (1) boron-implanted silicon wafer, (2) a barrier-type alumina film, and (3) a porous-type alumina film. It is believed that the method holds a great deal of promise as part of the arsenal of weapons in the thin films laboratory.

Festschrift↗
PubMed2004

Sampling procedure and a radio-indicator study of mercury determination in whole blood by using an AMA 254 atomic absorption spectrometer.

A sampling procedure appropriate for the determination of mercury in whole blood was tested by using both inactive controls and a 197Hg mercury radio-indicator. To exclude the influence of the instrumental device (an AMA 254 single-purpose mercury atomic absorption spectrometer) on the determination of mercury in whole blood, the function of the instrument was checked by using rat blood with metabolised 197Hg. The measurement procedure was found to be free of errors. However, the study showed that the material used for the sampling vessels is a crucial parameter for obtaining accurate analytical results. The stability of solutions and samples was tested towards polyethylene (PE) and polypropylene (PP) vessels. PE displayed a time-dependent increase in the mercury content both in the samples and in the blood control material. The probable cause of this increase was direct contamination from the material of the vessel and/or diffusion of mercury from the environment through the vessel walls related to a strong complexing affinity of the sample matrix. This assumption was confirmed by supplying the vessels with the complexing agent Na2EDTA (0.05 mol L(-1)). Commercial PP vessels for blood sampling (Sarstedt S-Monovette Metall Analytik) did not give rise to statistically significant variations in mercury content in the samples and blood control material over a 30-day period.

Adsorption↗
PubMed2005

Radio frequency glow discharge source with integrated voltage and current probes used for sputtering rate and emission yield measurements at insulating samples.

Radio frequency glow discharge optical emission spectroscopy (RF-GD-OES) is routinely used for the chemical analysis of solid samples. Two independent electrical signals from the discharge are required for quantification. When sputtering insulating samples, the voltage over the discharge is not directly measurable. The coupling capacity of the sample is required in order to calculate the discharge voltage. A procedure is outlined where the coupling capacity is determined using an electrical measurement without discharge. The calculated time-dependent discharge voltage and current are evaluated using a plasma equivalent circuit. An insulating sample is sputtered at constant cathode voltage and current. The emission yield for an aluminium line is comparable to that of conducting reference material.

Journal Article↗
PubMed2006

Non-metal element detection by radio-frequency glow-discharge optical-emission spectrometry (rf-GD-OES) for determination of sol-gel-immobilized nucleotides.

A new method is presented for qualitative and quantitative determination of non-metal elements present in organic analyte species immobilized in a sol-gel matrix. Nucleic acids were chosen as well-defined relevant biomolecules for which element ratios could be used for detection and identification. Solid, lyophilized powders of ribose-form nucleotides (AMP, ADP, and ATP) were immobilized/entrapped in a methlytrimethoxysilane (mTMOS) sol-gel matrix and monitored for P (I) 214.9 nm, C (I) 193.0 nm, O (I) 130.2, and N (I) 149.3 nm emission by radio-frequency glow-discharge optical-emission spectroscopy (rf-GD-OES). Using the sol-gel method, analytical blanks were obtained by use of un-doped sol-gels. Empirical formula calculations by use of P (I) and C (I), P (I) and N (I), and P (I) and O (I) emission response ratios demonstrate the versatility of the technique as an element and species-specific detector. Results show there is high correlation between phosphorus and oxygen emission responses and the extent of phosphorylation, demonstrating the capacity of the method to produce vital qualitative and quantitative information for the specific nucleotide. Absolute sub-nanogram detection limits were achieved for all the elements studied.

Gels↗