Search results for "radiation dose"

Dosimetric effect of respiratory motion on planned dose in whole-breast volumetric modulated arc therapy using moderate and ultra-hypofractionation.

2021

Abstract Background and purpose The interplay effect of respiratory motion on the planned dose in free-breathing right-sided whole-breast irradiation (WBI) were studied by simulating hypofractionated VMAT treatment courses. Materials and methods Ten patients with phase-triggered 4D-CT images were included in the study. VMAT plans targeting the right breast were created retrospectively with moderately hypofractionated (40.05 Gy in 15 fractions of 2.67 Gy) and ultra-hypofractionated (26 Gy 5 fractions of 5.2 Gy) schemes. 3D-CRT plans were generated as a reference. All plans were divided into respiratory phase-specific plans and calculated in the corresponding phase images. Fraction-specific d…

Fitness costs of increased cataract frequency and cumulative radiation dose in natural mammalian populations from Chernobyl

2015

AbstractA cataract is a clouding of the lens that reduces light transmission to the retina and it decreases the visual acuity of the bearer. The prevalence of cataracts in natural populations of mammals and their potential ecological significance, is poorly known. Cataracts have been reported to arise from high levels of oxidative stress and a major cause of oxidative stress is ionizing radiation. We investigated whether elevated frequencies of cataracts are found in eyes of bank voles Myodes glareolus collected from natural populations in areas with varying levels of background radiation in Chernobyl. We found high frequencies of cataracts in voles collected from different areas in Chernob…

The peculiarities of the radiation damage accumulation kinetics in the case of defect complex formation

2020

Abstract The kinetics of radiation defect accumulation under irradiation by heavy particles is theoretically analysed under the assumption of defect complex genesis, particularly, the ones of anion and cation vacancies. The obtained analytical mathematical model and revealed peculiarities of radiation dose dependencies can be used for analysis of the experimental results for different crystalline materials for solid-state electronics and photonics.

Efficacy of raw implementation and reduction dose protocols in CT colonoscopy: a single centre 4 years retrospective review

2015

Aims and objectives Methods and materials Results Conclusion Personal information References

Patient centring and scan length: how inaccurate practice impacts on radiation dose in CT colonography (CTC).

2019

Objective: The aim of this study was to acknowledge errors in patients positioning in CT colonography (CTC) and their effect in radiation exposure. Materials and methods: CTC studies of a total of 199 patients coming from two different referral hospitals were retrospectively reviewed. Two parameters have been considered for the analysis: patient position in relation to gantry isocentre and scan length related to the area of interest. CTDI vol and DLP were extracted for each patient. In order to evaluate the estimated effective total dose and the dose to various organs, we used the CT-EXPO ® software version 2.2. This software provides estimates of effective dose and doses to the other vario…

Cumulative radiation CT dose in young traumatic patients: a single centre 5 years retrospective review

2014

Acute and late toxicity and preliminary outcomes report of moderately hypofractionated helical tomotherapy for localized prostate cancer: a mono-inst…

2019

Aims: To assess toxicity and clinical outcomes of moderately hypofractionated helical tomotherapy (HT) for the curative treatment of localized prostate cancer (PC). Methods: From December 2012 to May 2018, 170 patients were treated with definitive intent for PC. Thirty-four percent were low risk, 30% intermediate risk (IR) and 36% high risk (HR). All patients received 70 Gy in 28 fractions to the prostate; 61.6 Gy were delivered to the seminal vesicles for IR; pelvic lymph nodes irradiation for a total dose of 50.4 Gy was added in the HR subgroup. Toxicity was assessed using CTCAE V4.0, and biochemical failure was defined following Phoenix criteria. Time-to-event data were analyzed using th…

Complete written/oral information about dose exposure in CT: is it really useful to guarantee the patients' awareness about radiation risks?

2018

Aims and objectives: According to the European directive 2013/59/Euratom, starting from February 2018, the information relating to patient exposure will be part of computed tomography (CT) reports, but the impact of this information on patients has not been deeply evaluated. Aim of our study was to evaluate patients’ perception of radiation exposure related to routine CT and their understanding after communication of their dose exposure. Materials and methods: A survey, investigating patient’s knowledge of radiation dose, was given to all adult patients (> 18 years) undergoing a CT examination both before and after CT scan. The first survey was the same for all patients. After CT scan, a se…

Robustness of radiation beam profile measurements

2023

In this master’s thesis, profile measurements of PTW Semiflex 3D and PTW Semiflex ionisation chambers in addition to IBA MatriXX matrix detector were compared to each other using different measurement set-ups. The ionisation chamber measure- ments were done in a water phantom in horizontal and vertical orientations. Using two different set-ups in the horizontal orientation. The first horizontal set-up used the current clinical quality assurance program in Tampere University Hospital with the wire of the chamber lying deep in the water phantom. The second horizontal measurements were done with more of the wire in the radiation field by having the wire closer to the surface of the water. Meas…

Änderungen der Gitterstruktur hochpolymerer Einkristalle durch Bestrahlung im Elektronenmikroskop

1965

Die durch Bestrahlung mit Elektronen von 40 bis 80 kV hervorgerufenen Anderungen der Gitterstruktur von Polyathylen(PA)- und Polyoxymethylen(POM)-Einkristallen wurden unterrsucht. Dazu wurden Lage, Intensitat und Linienbreite der Reflexe im Elektronenbeugungsdiagramm in Abhangigkeit von der Bestrahlungsdosis gemessen. Vergleichende Untersuchungen wurden an einem Paraffin (C28H58) durchgefuhrt. Aus den Anderungen der Linienbreite konnte geschlossen werden, das im Falle des PA durch die Vernetzung zwischen benachbarten Ketten Gitterstorungen II. Art (parakristalline Storungen) hervorgerufen werden. Sie fuhren auch zu einer betrachtlichen Aufewitung des Gitters. Im Falle des Paraffins dagegen …