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PubMed2006

[Drug application forms in chronic pain therapy].

The choice of the appropriate application form is a critical prerequisite to ensure therapeutic success in pain therapy. Tablets, capsules, and oral liquids are the classical application forms. Slow release formulas have optimized the therapy of chronic pain and offer the possibility of an oral basic medication with only two applications a day. Transdermal delivery systems of highly effective opioids offer particular advantages in chronic and stable pain conditions. Oromucosal delivery systems are an option for a rapidly effective rescue medication, while suppositories are not an application form of first choice because of their low acceptance by the patients and poorly reproducible bioavailability. PCA (patient controlled analgesia) needs to be reserved for patients lacking other therapeutic options. For many of those application forms specific information about prescription and application is needed to ensure good therapeutic results.

Analgesics↗

PubMed1989

Applications and admissions to UK dental schools through UCCA: 1968-1987.

Applications and admissions to UK dental schools through the UCCA system have been analysed for the 20-year period from 1968 to 1987. Applications rose from 1225 in 1968 to a peak of 3065 in 1974. By 1987, applications had fallen to 2050, 67% of the peak number. The ratio of male:female applicants has declined from 4:1 in 1968 to 1.6:1 in 1987. The number of dental students accepted through UCCA has varied much less during the 20-year period, rising from 831 in 1968 to a peak of 989 in 1980, and falling back to 893 in 1987. The number of dental students admitted to dental schools through UCCA in the 4 years including and after 1984 was 7.4% less than in the 4 years prior to 1984. This suggests that the 1984 cut of 10% was not fully achieved. The ratio of male:female students admitted has fallen from 3.4:1 in 1968 to 1.4:1 in 1987. In every year studied, the male:female ratio of UCCA applicants was higher than for accepted dental students. This could suggest that female applicants to dental school have higher academic or personal qualities than their male counterparts.

Educational Measurement↗

PubMed2000

Therapeutic application of T cell receptor mimic peptides or cDNA in the treatment of T cell-mediated skin diseases.

An 8-amino acid peptide encoding a sequence of the transmembrane region of the T cell receptor alpha chain (TCR-alpha) was shown to inhibit T cell function by preventing functional assembly of the T cell receptor (mimic peptide). To avoid systemic immunosuppression by peptide application in vivo, we used a topical application of the peptide. In the system of murine contact sensitivity, topical application of the peptide inhibited the elicitation of contact sensitivity following application of a contact allergen in sensitized animals. Alternatively, when naked DNA encoding the peptide sequence was injected into skin before application of a contact allergen to sensitized animals, local immunosuppression was also observed. To investigate the effects of this peptide in humans, patients with psoriasis, atopic eczema, lichen planus, or contact dermatitis were treated topically with mimic peptide or control peptide. All patients except for one reported a marked improvement or cure of their skin disease following application of the TCR-alpha peptide, but not controls. These data indicate that TCR-alpha peptide or cDNA treatment might be a proper treatment for human T cell-mediated dermatoses substituting for corticosteroids.

Allergens↗

PubMed2001

Plasma concentrations of lignocaine and prilocaine after a 24-h application of analgesic cream (EMLA) to leg ulcers.

BACKGROUND: Although the lignocaine (lidocaine)-prilocaine cream EMLA has been extensively studied for the relief of acute treatment-related pain from sharp leg ulcer debridement, no data exist on systemic absorption from prolonged application in patients with chronically painful ulcers. OBJECTIVES: To study the plasma concentrations of lignocaine and prilocaine resulting from prolonged application of EMLA to leg ulcers. METHODS: A single 24-h application of 5-10 g (median 6.75) of EMLA was given to 10 patients with painful leg ulcers measuring 50-100 cm2. Venous blood samples, drawn between 0.5 and 27 h after cream application, were analysed by gas chromatography using a nitrogen-sensitive detector. RESULTS: The peak plasma levels were in the range 185-705 ng mL(-1) and 62-277 ng mL(-1) for lignocaine and prilocaine, respectively, and were observed 2-4 h (in one patient 6-8 h) after application. The peak plasma concentration of lignocaine, but not of prilocaine, increased significantly with increasing dose. The cream was well tolerated by the patients. CONCLUSIONS: The results indicate that a 24-h application of 5-10 g EMLA results in peak plasma concentrations of the two local anaesthetics, which combined are less than one-fifth of those associated with toxic reactions. The analgesic efficacy of EMLA for the relief of chronic ulcer pain deserves further study.

Aged↗

PubMed2002

Intranasal application of purified protein derivative suppresses the initiation but not the exacerbation of allergic rhinitis in mice.

BACKGROUND: Several epidemiological and experimental studies have demonstrated that exposure to pathogens such as those from the genus Mycobacterium leads to the suppression of allergic sensitization and inflammation. However, little is known as to whether pathogen-derived soluble antigens have the potential to modulate the pathogenesis of allergic rhinitis. OBJECTIVE: We sought to determine whether application of purified protein derivative (PPD) from Mycobacterium tuberculosis can suppress the initiation and/or exacerbation of allergic rhinitis using a recently developed murine model. METHODS: First, we investigated whether a single intranasal application of PPD could elicit cytokine production in the nose by RT-PCR. BALB/c mice were repeatedly sensitized with Schistosoma mansoni egg antigen (SEA) intranasally without an adjuvant. PPD was applied through different routes either before or after sensitization. The production of SEA-specific antibodies, nasal eosinophilia and cytokines by nasal lymphocytes was compared among mice that had or had not received PPD treatment. RESULTS: IFN-gamma, but not IL-4, was detected in the nasal tissue 12 to 48 h after a single intranasal application of 10 microg PPD. Repeated intranasal application of PPD prior to and during sensitization with SEA significantly inhibited the production of both SEA-specific IgE/IgG1 and nasal eosinophilia. Moreover, it partially inhibited the production of IL-4 by nasal lymphocytes in response to SEA. Conversely, this treatment led to a significant increase in IFN-gamma production. On the other hand, PPD applied through the footpad had no effect over the same period. Repeated intranasal application of PPD after sensitization with SEA had no exacerbative effect on allergic inflammation. CONCLUSION: These results indicate that the local application of PPD, and the subsequent induction of IFN-gamma, inhibits the initiation, but not the exacerbation, of allergic rhinitis in mice. This suggests that pathogen-derived antigens have potential for use in the prevention and prophylaxis of allergic rhinitis.

Administration, Intranasal↗

PubMed2003

The histological features of microwave coagulation therapy: an assessment of a new applicator design.

Microwave ablation of tumours within the liver may become an adjunct or alternative to resection in patients with primary or secondary cancers. This technique combines the benefits of a large, localized coagulative effect with a single insertion of the applicator, in a significantly shorter time than comparable treatments. A new range of microwave applicators were developed and tested in animal models and both ex-vivo and in-vivo specimens of human liver at resection. At laparotomy, the applicator tip was inserted into normal liver parenchyma and tumours, with each specimen subjected to irradiation for 180 s or more and at varying power outputs. On sectioning an area of spherical blanching was observed around the applicator cavity. Microscopically a zone of coagulative necrosis was seen adjacent to the site of probe insertion. Damage to blood vessels and bile ducts occurred distal to the probe cavity suggesting the passage of heated fluid, a finding that was diminished by temporary occlusion of the hepatic vasculature (a Pringle manoeuvre). Ultra-structural damage was confirmed within the burn zone and selected liver enzymes were shown to be functioning beyond this region. We suggest this indicates the surrounding liver parenchyma is functioning normally and therefore the volume of microwave-induced damage is controllable. We are confident that the new applicator design will allow the effective treatment of larger tumours in a safe and controlled manner with a single application of energy.

Animals↗

PubMed2005

Effects of temporal application parameters on lesion dimensions during transvenous catheter cryoablation.

UNLABELLED: Lesion dimension of cryoablation. BACKGROUND: Transvenous catheter cryoablation is a novel technique for treating cardiac arrhythmias. However, the relative importance of temporal application parameters on lesion dimension and clinical efficacy has not been studied. METHODS AND RESULTS: We investigated the effects of (1) application duration: single 2.5 (2.5x1) versus single 5 versus double 2.5 (2.5x2) versus double 5 (5x2) minutes, (2) number of freeze-thaw cycles: single versus double, and (3) electrode contact area: horizontal versus vertical orientation, on the lesion diameter and depth during catheter cryoablation (10F, 6.5-mm tip-electrode, CryoCor, San Diego) in a thigh muscle preparation. A total of 175 lesions (horizontal=90, vertical=85) were created in thigh muscle preparations on 10 swine. The lesion diameter and depth were significantly greater using 2.5x2 and 5x2 application modes as compared with 2.5x1 applications (P<0.05). Horizontal tip-electrode orientation produced larger lesion diameter (P<0.05), but not lesion depth as compared with vertical orientation. Multivariate analysis demonstrated that both tip-electrode orientation and duration of freeze >2.5 minutes were independent predictors for lesion diameter (P<0.001). However, only duration of freeze >2.5 minutes was an independent predictor for lesion depth (P<0.001). CONCLUSIONS: The dimensions of lesions created by catheter cryoablation are affected by mode of cryoablation application and electrode orientation. Increasing the duration of application, employing multiple freeze-thaw cycles at shorter cycle durations, and orienting the catheter to enhance/increase tissue contact can create a larger lesion.

Animals↗

PubMed2000

Bioavailability and pharmacokinetic profile of glyceryl trinitrate and of glyceryl dinitrates during application of a new glyceryl trinitrate transdermal patch.

The pharmacokinetics and bioavailability of glyceryl trinitrate (GTN, CAS 55-63-0) and of its main metabolites, i.e. 1,2-glyceryl dinitrate (1,2-GDN, CAS 621-65-8) and 1,3-glyceryl dinitrate (1,3-GDN, CAS 623-87-0), were compared during a single 24-h application of a new GTN transdermal patch (Epinitril 10, hereinafter called EPI-10) or a reference patch (hereinafter called ND-10) releasing 10 mg GTN in 24 h. The study was an open, randomized balanced cross-over study on 24 healthy male volunteers to whom the patches were applied to the antero-lateral part of the thorax in two periods separated by a 3-day wash-out. Blood samples were collected before administration, during the 24-h patch application and at 0.5, 2 and 3 h after patch removal. Assayed in plasma were GTN, 1,2-GDN and 1,3-GDN using validated GC/MS methods with stable isotope-labeled internal standards (15N3-GTN, 15N2-1,2-GDN, and 15N2-1,3-GDN). The ratios of the AUCs of GTN, 1,2-GDN and 1,3-GDN measured during application of EPI-10 or of ND-10 were within the 0.85-1.25 limits required to assess equivalence of the extent of bioavailability. The ratios of the Cmax were within said limits for the signal metabolite 1,2-GDN and only slightly below (0.78-1.16) for the parent GTN. EPI-10 can therefore be considered equivalent to ND-10 also with regard to the rate of bioavailability. Under both patches GTN reached steady-state levels after 3-6 h of patch application and remained on sustained levels during the whole 24-h application. The plasma levels of 1,2-GDN were about 6 times higher than those of GTN. The plasma levels of 1,3-GDN were similar to those of GTN. Upon removal of the patches the concentrations of the three nitrates fell to negligible values within 3 h. Both patches were well tolerated at the application site. For its small size, thinness and transparency, EPI-10 is very patient friendly, a quality that improves compliance with the therapeutic regimen.

Adhesiveness↗

PubMed1999

A new long-range through-the-scope balloon applicator for photodynamic therapy in the esophagus and cardia.

BACKGROUND AND STUDY AIMS: Photodynamic therapy (PDT) is a new local, endoscopically controlled therapeutic technique based on the sensitization of malignant and precancerous lesions prior to light-induced tissue destruction. PDT of Barrett's esophagus with severe dysplasia, or of mucosal carcinomas and superficial squamous-cell cancer of the esophagus, requires light application devices allowing homogeneous illumination of the tissue surface in spite of esophageal motility and respiratory movement. On the basis of a commercially available through-the-scope balloon system, we developed a long-range light applicator for homogeneous and circumferential irradiation during PDT, and describe here the initial clinical experience with the device. PATIENTS AND METHODS: The new balloon applicator consists of a flexible cylindrical diffuser fiber with a length of up to 10 cm, depending on the lesion to be illuminated, and an inflatable balloon based on the type of balloon used for esophageal dilation. The balloon is made of a transparent polyurethane membrane with negligible absorption (<5%) at lambda = 600-700 nm, and it can be positioned through the biopsy channel of a conventional endoscope, with direct endoscopic visualization of the targeted lesion. The light intensity distribution perpendicular to the optical axes of the diffuser was measured for red laser light (lambda = 632.8 nm) and for green laser light (lambda = 542 nm). The study of photodynamic treatment included two women and four men (aged 48-79 years) with histologically proved high-grade dysplasia (n = 2) or mucosal cancer in Barrett's esophagus (n = 2) and superficial squamous-cell cancer (SCC) (n = 2), who had undergone EUS staging showing uT0 or uT1N0. Laser light irradiation was conducted after oral ingestion of 5-aminolevulinic acid (5-ALA) or intravenous administration of meta-(tetrahydroxyphenyl)chlorin (mTHPC). RESULTS: Both in vitro and in vivo, precise positioning of the new application system at the targeted tissue and homogeneous illumination were feasible, safe and effective. The total efficiency of transmitted light at wavelengths of lambda = 632.8 nm and lambda = 542 nm was 85-90%. A high degree of homogeneity was measured with applicator lengths of between 15 mm and 95 mm, and the maximum deviation from the mean intensity extended over a range of 40% over the total length of 80 mm. High-grade dysplasia was eradicated in all patients, and in addition mucosal cancer was successfully destroyed in three-quarters of them, requiring an average of 1.3 treatment sessions, with a mean follow-up of 12 months (range 10-15 months). CONCLUSIONS: This centering balloon system may in the future be capable of improving light application techniques during esophageal photodynamic therapy, making PDT a more reliable alternative modality for minimally invasive treatment of high-grade dysplasia and early Barrett's esophagus or squamous-cell carcinoma, as compared with esophagectomy.

Adenocarcinoma↗

PubMed2002

[Fluorescence staining of oral and laryngeal cancer after application of 5-aminolevulinic acid].

BACKGROUND: Cancer of the oral cavity, oropharynx and larynx are the most common malignancies in the head and neck region. The prognosis for the patients concerned is highly dependent on an early detection and fast surgical treatment. Fluorescence guided examinations may serve as a possible diagnostic tool for better demarcation and delimitation of head and neck cancer. Therefore, the presented study was aimed at the detection of a selective Protoporphyrin IX (PPIX) accumulation in malignant oral, oropharyngeal and laryngeal lesions following topical and systemic application of 5-aminolevulinic acid (5-ALA). PATIENTS: We investigated 193 patients with suspected lesions in the oral cavity and oropharynx (n = 126) as well as in the larynx (n = 67). The patients received a varying dose (rinsing 200 mg, inhalation 30 mg, 2,5 - 25 mg/kg BW by mouth) of 5-ALA in aqueous solution. Both fluorescence pictures and macroscopic findings under white light were recorded using a target integrating, color CCD camera. Fluorescence contrasts between tumor and normal tissue were registered by an optical multichannel analyser. RESULTS: Our results have shown that after topical and systemic application of 5-ALA, PPIX fluorescence could be identified within the mucosa of the oral cavity, oropharynx and the larynx of all patients with a duration of up to 48 hours after systemic application. Malignant lesions usually showed higher intensities of PPIX-fluorescence than surrounding innocuous mucosa. A maximum fluorescence contrast between normal tissue and neoplastic lesions was observed at 1.5 hours after topical application and 3 hours after systemic application. CONCLUSIONS: It will be the aim of further investigations to verify the optimal time of incubation and dosing of systemical 5-ALA application to enhance fluorescence contrasts and set the basis for fluorescence guided resections.

Administration, Inhalation↗

PubMed2004

[Individual silicon applicator for nasopharyngeal brachytherapy].

BACKGROUND: Beyond surgery, conventional radiation therapy, and chemotherapy brachytherapy may enrich treatment of primary, residual, or recurrent head and neck cancer. Nasopharyngeal cancer is a proper indication for intracavitary brachytherapy which can be performed using a commercial applicator system or an individual applicator. METHODS AND PATIENTS: Technique for manufacturing an individual nasopharyngeal silicon applicator and its experiences in 3 patients (2 times brachytherapy in treatment regime of primary nasopharyngeal cancer, 1 time for nasopharyngeal lymphoma treatment) are presented. RESULTS: Under general anaesthesia in all 3 patients nasopharyngeal imprinting after placement of two suction tubes was performed with shore 12 silicon and followed by manufacturing the individual silicon applicator with two included tubes after plaster cast of the imprinting form has been performed. This silicon applicator enabled safe endocavitary brachytherapy using the high-dose-rate-afterloading-method. Tumor control was achieved in all 3 patients. CONCLUSIONS: The presented individual silicon applicator is suited for intracavitary brachytherapy of the nasopharynx being an valuable contribution in the primary treatment regime of nasopharyngeal cancer.

Adult↗

PubMed2005

Commercial applications of nuclear transfer cloning: three examples.

Potential applications of cloning go well beyond the popularly envisioned replication of valuable animals. This is because targeted genetic modifications can be made in donor cells before nuclear transfer. Applications that are currently being pursued include therapeutic protein production in the milk and blood of transgenic cloned animals, the use of cells, tissues and organs from gene-modified animals for transplantation into humans and genetically modified livestock that produce healthier and safer products in an environmentally friendly manner. Commercial and social acceptance of one or more of these early cloning applications will lead to yet unimagined applications of nuclear transfer technology. The present paper summarises progress on three additional applications of nuclear transfer, namely the development of male livestock that produce single-sex sperm, the transfer of immune responses from animals to their clones to permit the production of unlimited supplies of unique polyclonal antibodies, and the generation of genetically modified animals that accurately mimic human diseases for the purpose of developing new therapies. However, the myriad applications of cloning will require appropriate safeguards to ensure safe, humane and responsible outcomes of the technology.

Animals↗

PubMed1995

Military and government applications of human-machine communication by voice.

This paper describes a range of opportunities for military and government applications of human-machine communication by voice, based on visits and contacts with numerous user organizations in the United States. The applications include some that appear to be feasible by careful integration of current state-of-the-art technology and others that will require a varying mix of advances in speech technology and in integration of the technology into applications environments. Applications that are described include (1) speech recognition and synthesis for mobile command and control; (2) speech processing for a portable multifunction soldier's computer; (3) speech- and language-based technology for naval combat team tactical training; (4) speech technology for command and control on a carrier flight deck; (5) control of auxiliary systems, and alert and warning generation, in fighter aircraft and helicopters; and (6) voice check-in, report entry, and communication for law enforcement agents or special forces. A phased approach for transfer of the technology into applications is advocated, where integration of applications systems is pursued in parallel with advanced research to meet future needs.

Aircraft↗

PubMed2004

Application of advanced synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy to animal nutrition and feed science: a novel approach.

Synchrotron radiation-based Fourier transform IR (SR-FTIR) microspectroscopy has been developed as a rapid, direct, non-destructive and bioanalytical technique. This technique, taking advantage of synchrotron light brightness and a small effective source size, is capable of exploring the molecular chemistry within the microstructures of a biological tissue without the destruction of inherent structures at ultraspatial resolutions within cellular dimensions. This is in contrast to traditional 'wet' chemical methods, which, during processing for analysis, often result in the destruction of the intrinsic structures of feeds. To date there has been very little application of this technique to the study of feed materials in relation to animal nutrient utilisation. The present article reviews four applications of the SR-FTIR bioanalytical technique as a novel approach in animal nutrition and feed science research. Application 1 showed that using the SR-FTIR technique, intensities and the distribution of the biological components (such as lignin, protein, lipid, structural and non-structural carbohydrates and their ratios) in the microstructure of plant tissue within cellular dimensions could be imaged. The implication from this study is that we can chemically define the intrinsic feed structure and compare feed tissues according to spectroscopic characteristics, functional groups, spatial distribution and chemical intensity. Application 2 showed that the ultrastructural-chemical makeup and density of yellow- and brown-seeded Brassica rape could be explored. This structural-chemical information could be used for the prediction of rapeseed quality and nutritive value for man and animals and for rapeseed breeding programmes for selecting superior varieties for special purposes. More research is required to define the extent of differences that exist between the yellow- and brown-seeded Brassica rape. Application 3 showed with the SR-FTIR technique that chemical differences in the ultrastructural matrix of endosperm tissue between Harrington (malting-type) and Valier (feed-type) barley in relation to rumen degradation characteristics could be identified. The results indicated that the greater association of the protein matrix with the starch granules in the endosperm tissue of Valier barley may limit the access of ruminal micro-organisms to the starch granules and thus reduce the rate and extent of rumen degradation relative to that of Harrington barley. It is the first time that the microstructural matrix in the endosperm of barley has been revealed by using the SR-FTIR technique, which makes it possible to link feed intrinsic structures to nutrient utilisation and digestive behaviour in ruminants. Application 4 showed with the SR-FTIR technique that the chemical features of various feed protein (amide I) secondary structures (such as feather, wheat, oats and barley) could be quantified. With a multi-component fitting program (Lorentz function), the results showed feather containing about 88% beta-sheet and 4% alpha-helix, barley containing about 17% beta-sheet and 71% alpha-helix; oats containing about 2% beta-sheet and 92% alpha-helix; and wheat containing about 42% beta-sheet and 50% alpha-helix. The relative percentage of the two may influence protein value. A high percentage of beta-sheet may reduce the access of gastrointestinal digestive enzymes to the protein structure. Further study is required on feed protein secondary structures in relation to enzyme accessibility and digestibility. In conclusion, the SR-FTIR technique can be used for feed science and animal nutrition research. However, the main disadvantage of this technique is the requirement for a special light source; a synchrotron beam.

Animal Feed↗

PubMed2002

Field study investigation of applicant use of influence tactics in a selection interview.

Employees often evaluate leadership potential when selecting applicants for jobs that require leadership ability (e.g., supervisors, firefighter captains). Research has shown that influencing others is an important part of being an effective leader, yet employers rarely explicitly consider applicants' use of influence tactics when evaluating applicants' leadership potential. The purpose of this study was to explore applicant use of influence tactics in an employment interview and to determine how such use relates to interview ratings. The authors observed firefighter applicants' behavior during a selection role-play interview and recorded their use of influence tactics. Results indicated that firefighter applicants used soft tactics (e.g., ingratiation, rational persuasion) significantly more frequently than they used hard tactics (e.g., pressure, coalition). Soft tactic use was positively correlated with interview ratings.

Analysis of Variance↗

PubMed1994

Effects of applicant overeducation, job status, and job gender stereotype on employment decisions.

Employment preferences of personnel representatives in electronics firms regarding job applicants who had varying levels of education were investigated. The applicants had either obtained a 4-year college degree, completed 2 years of college, or completed high school. The stimulus jobs required the equivalent of a high school education but varied in terms of status and gender stereotype. The personnel representatives tended to recommend college-educated applicants for higher status jobs and male stereotypic jobs and applicants who had high school degrees for lower status and female stereotypic jobs. Contrary to the results of most previous research on overeducation, the performance of the applicants who were college graduates was expected to be higher than that of the less educated applicants.

Educational Status↗

PubMedDate not supplied

Directional power deposition from direct-coupled and catheter-cooled interstitial ultrasound applicators.

This research represents an experimental investigation of the directional power deposition capabilities of interstitial ultrasound applicators intended for applications in hyperthermia and thermal surgery for cancerous or benign disease. Direct-coupled and catheter-cooled ultrasound applicators were fabricated using cylindrical piezoceramic transducers sectored to produce 90 degrees, 180 degrees or 270 degrees active acoustic zones. The applicators were characterized through measurements of acoustic power output and intensity beam distributions in degassed water, in vitro temperature measurements in a perfused kidney model, and in vivo temperature distributions in pig thigh muscle. The angular power deposition patterns obtained in water were closely correlated to the resultant temperature distributions measured in the perfused kidney and in vivo pig thigh muscle. These sectored catheter-cooled and direct-coupled devices both demonstrated the ability to generate high temperatures (>50 degrees C) at sustained high power output levels (6-12 W) without degradation of the ultrasound transducers. Directional control of the energy deposition from the sectored ultrasound applicators was verified with corresponding temperature profiles in both the in vitro and in vivo experiments, as well as with angularly shaped thermal lesions. This is significant in that it demonstrates that heating in the angular expanse can be controlled with interstitial ultrasound applicators, thus providing more conformal thermal therapy by directing the thermal energy in the targeted tissue while protecting non-targeted tissue from thermal damage.

Animals↗

PubMedDate not supplied

Characterization of the SAR-distribution of the Sigma-60 applicator for regional hyperthermia using a Schottky diode sheet.

INTRODUCTION: Characterization of the performance of an hyperthermia applicator by phantom experiments is an essential aspect of quality assurance in hyperthermia. The objective of this study was to quantitatively characterize the energy distribution of the Sigma-60 applicator of the BSD2000 phased array system operated within the normal frequency range of 70-120 MHz. Additionally, the accuracy of the flexible Schottky diode sheet to measure E-field distributions was assessed. MATERIAL AND METHODS: The flexible Schottky diode sheet (SDS) consists of 64 diodes mounted on a flexible 125 microm thick polyester foil. The diodes are connected through high resistive wires to the electronic readout system. With the SDS E-field distributions were measured with a resolution of 2.5 x 2.5 cm in a cylindrical phantom, diameter of 26 cm and filled with saline water (2 g/l). The phantom was positioned symmetrically in the Sigma-60 applicator. RF-power was applied to the 4-channel applicator with increasing steps from 25W to a total output of 400 W. RESULTS: The complete system to measure the E-field distribution worked fine and reliably within the Sigma-60 applicator. The E-field distributions measured showed that the longitudinal length of the E-field distribution is more or less constant, e.g. 21-19 cm, over the frequency range of 70-120 MHz, respectively. As expected, the radial E-field distributions show a better focusing towards the centre of the phantom for higher frequencies, e.g. from 15.3-8.7 cm diameter for 70-120 MHz, respectively. The focusing target could be moved accurately from the left to the right side of the phantom. Further it was found that the sensitivity variation of nine diodes located at the centre of the phantom was very small, e.g. < 3% over the whole frequency range. CONCLUSION: The SAR distributions of the Sigma-60 applicator are in good agreement with theoretically expected values. The flexible Schottky diode sheet proves to be an excellent tool to make accurate, quantitative measurements of E-field distributions at low (25 W) and medium (400 W) power levels. An important feature of the SDS is that it enables one to significantly improve quantitative quality assurance procedures and to start quantitative comparisons of the performance of the different deep hyperthermia systems used by the various hyperthermia groups.

Equipment Design↗