Surface potential uniformity and sensitivity of large-area PTFE electret discs of different thicknesses produced by a modified corona poling rotating system for dosimetry applications

In this study, large-area (6-cm diameter) Teflon polytetrafluoroethylene (PTFE) discs of different thicknesses (0.2-, 0.5- and 1 -mm) were negatively and positively charged by using the “modified single point-to-plane corona poling rotating system”. The effects of some crucial parameters of the PTFE disc as well as the modified corona poling rotating system on the PTFE surface potential uniformity such as: (a) PTFE disc thickness, (b) PTFE disc polarity and (c) needle-to-PTFE disc distance were successfully reported. Accordingly, closer needle-to-PTFE disc distance, positive charging mode and thinner PTFE disc provided a better PTFE surface potential uniformity. However, the effects of PTFE charge polarity and needle distance on the electrostatic charge potential uniformity were much more remarkable in comparison with the effects of PTFE thickness. Additionally, the surface potential distribution profiles of charged PTFE discs were totally flat and independent of the PTFE thickness at 5- and 13-[Formula: see text]mm needle distances for the negative and positive charging modes, respectively. At the optimized charging conditions, large-area PTFE electret disc (0.5-mm-thick) with positive uniform surface charge potential especially at the edges up to [Formula: see text] 1.8[Formula: see text]kV with stability up to 77 days studied was produced by applying a new multiple heat treatment protocol to the PTFE disc for radon dosimetry. As also observed in this study, the sensitivity of PTFE electret dosimeters to a defined radon gas concentration increases as the PTFE thickness increases. Meanwhile, 0.5-mm-thick PTFE electret disc produced was selected to be used as a high quality electret dosimeter with acceptable and superior parameters for different applications in particular medium-term radiation dosimetry in both low and high dose rate ionizing radiation fields.

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High-Dose Interstitial Brachytherapy for Glioblastoma Multiforme

Tumori Journal ◽

10.1177/030089169408000109 ◽

1994 ◽

Vol 80 (1) ◽

pp. 44-49 ◽

Cited By ~ 4

Author(s):

Enrico Micheletti ◽

Giovanni Baroncelli ◽

Beniamino La Face ◽

Piero Feroldi ◽

Marco Galelli ◽

...

Keyword(s):

Glioblastoma Multiforme ◽

Performance Status ◽

Treatment Protocol ◽

Target Volume ◽

High Dose Rate ◽

High Dose ◽

Treatment Schedule ◽

Ecog Performance Status ◽

Short Treatment ◽

Long Term Prognosis

Aims and background The long-term prognosis for survival of patients with inoperable glioblastoma multiforme (GBL) is very poor. Conventional external radiotherapy gives only transitory result. This severe prognosis led us to elaborate a high-dose rate (HDR), after-remote-loading brachytherapy treatment protocol: our aim was both therapeutic and psychologic Methods Five patients with GBL (T1 G4 UICC) were treated with stereotactic biopsy followed by HDR brachytherapy. A unique coaxial after-loading catheter was stereotactically inserted through the center of the target volume. The treatment schedule considered 5 fractions, 5 Gy/fraction at the dose specification surface, 2 fractions per day. Results The treatment was well tolerated. Tumor progression started again at the 8th to the 16th week from the end of the treatment. ECOG performance status at the 8th week was better than before the therapy in 2 of 5 patients and was stable in 2 of 5 patients. Order neuroperformance status was stable in 2 patients at 8 weeks. At the 16th week there was neurologic deterioration. The average survival was 21 weeks. Conclusions Our approach seems to be of some interest for the pal-lation of GBL, and it offers some advantages, in particular regarding the short treatment period. Our procedure can be improved: a multicatheter implant and a more fractionated schedule could be taken into account.

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Additional Invasive Techniques in Scar Management

Textbook on Scar Management ◽

10.1007/978-3-030-44766-3_40 ◽

2020 ◽

pp. 343-349

Author(s):

E. de Bakker ◽

M. C. E. van Leeuwen ◽

O. W. M. Meijer ◽

F. B. Niessen

Keyword(s):

Radiation Therapy ◽

Dose Rate ◽

Treatment Protocol ◽

High Dose Rate ◽

Secondary Malignancy ◽

High Dose ◽

External Radiation ◽

Recurrence Rates ◽

High Dose Rate Brachytherapy ◽

Significant Burden

AbstractRadiation therapy is a last resort option for recurring and therapy-resistant keloid scars. It represents a significant burden to the patient and both financially and logistically to the healthcare system. Radiation therapy yields excellent results, both functionally and aesthetically and in low recurrence rates. An efficacious treatment protocol consists of excision of the entire keloid, followed by rapid administration of the first radiation dose. The most commonly used techniques are external radiation, low-dose-rate brachytherapy, and high-dose-rate brachytherapy. Brachytherapy is associated with fewer side effects and a lower recurrence rate in comparison with external radiation. The use of high-dose-rate brachytherapy is more convenient because it allows an outpatient setting and prevents unnecessary radiation damage to the surrounding tissue. Although more research is needed, a biological effective dose (BED) of 20–30 Gy, for example, 2 × 6 Gy, seems sufficient for most cases. The most commonly seen complications are erythema, temporary and permanent pigmentation disturbances, and telangiectasia. Although it is necessary to mention the risk of inducing secondary malignancy in the treated area, only a few cases have been described, out of which none were caused by brachytherapy.

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