Publications by authors named "Elisabeth Mara"

4 Publications

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Rubella and tick-borne encephalitis vaccination rates among staff and students at Austrian University of Applied Sciences.

Cent Eur J Public Health 2021 Mar;29(1):18-22

University of Applied Sciences Wiener Neustadt, Wiener Neustadt, Austria.

Objectives: Rubella and tick-borne encephalitis (TBE) are infectious diseases caused by viruses. Rubella is an air-borne infection. TBE, on the other hand, is transmitted by virus-infected ticks. Both diseases show specific symptoms after an incubation period of approximately 10 days. The Austrian vaccination plan recommends vaccinations against both viruses, as only these can protect against both infectious diseases. Because of both, an increase in measles infections and the high endemic rate of TBE in Austria, our goal was to evaluate the vaccination rate, antibody titre and general level of knowledge with respect to these two infections amongst adults in order to identify possible nescience regarding booster vaccination and general titre rates.

Methods: One hundred ninety-nine people participated in the study of the TBE and rubella titre determination. We used indirect ELISA and asked the volunteers to complete a questionnaire.

Results: The analysis of the results showed a vaccination coverage rate of over 90% for both diseases.

Conclusion: Our findings lead to the conclusion that the protection through immunization is very high and the vaccines used are extremely effective, particularly as some individuals do not adhere to the recommended vaccination schedule.
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http://dx.doi.org/10.21101/cejph.a6014DOI Listing
March 2021

RBE variation in prostate carcinoma cells in active scanning proton beams: In-vitro measurements in comparison with phenomenological models.

Phys Med 2020 Sep 29;77:187-193. Epub 2020 Aug 29.

Department of Radiation Oncology, Medical University Vienna, Austria. Electronic address:

Purpose: In-vitro radiobiological studies are essential for modelling the relative biological effectiveness (RBE) in proton therapy. The purpose of this study was to experimentally determine the RBE values in proton beams along the beam path for human prostate carcinoma cells (Du-145). RBE-dose and RBE-LET (dose-averaged linear energy transfer) dependencies were investigated and three phenomenological RBE models, i.e. McNamara, Rørvik and Wilkens were benchmarked for this cell line.

Methods: Cells were placed at multiple positions along the beam path, employing an in-house developed solid phantom. The experimental setup reflected the clinical prostate treatment scenario in terms of field size, depth, and required proton energies (127.2-180.1 MeV) and the physical doses from 0.5 to 6 Gy were delivered. The reference irradiation was performed with 200 kV X-ray beams. Respective (α/β) values were determined using the linear quadratic model and LET was derived from the treatment planning system at the exact location of cells.

Results And Conclusion: Independent of the cell survival level, all experimental RBE values were consistently higher in the target than the generic clinical RBE value of 1.1; with the lowest RBE value of 1.28 obtained at the beginning of the SOBP. A systematic RBE decrease with increasing dose was observed for the investigated dose range. The RBE values from all three applied models were considerably smaller than the experimental values. A clear increase of experimental RBE values with LET parameter suggests that proton LET must be taken into consideration for this low (α/β) tissue.
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http://dx.doi.org/10.1016/j.ejmp.2020.08.012DOI Listing
September 2020

Investigating the impact of alpha/beta and LET on relative biological effectiveness in scanned proton beams: An in vitro study based on human cell lines.

Med Phys 2020 Aug 15;47(8):3691-3702. Epub 2020 May 15.

Department of Radiation Oncology/Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria.

Purpose: A relative biological effectiveness (RBE) of 1.1 is commonly used in clinical proton therapy, irrespective of tissue type and depth. This in vitro study was conducted to quantify the RBE of scanned protons as a function of the dose-averaged linear energy transfer (LET ) and the sensitivity factor (α/ß) . Additionally, three phenomenological models (McNamara, Rørvik, and Jones) and one mechanistic model (repair-misrepair-fixation, RMF) were applied to the experimentally derived data.

Methods: Four human cell lines (FaDu, HaCat, Du145, SKMel) with differential (α/ß) ratios were irradiated in a custom-designed irradiation setup with doses between 0 and 6 Gy at proximal, central, and distal positions of a 80 mm spread-out Bragg peak (SOBP) centered at 80 mm (setup A: proton energies 66.5-135.6 MeV) and 155 mm (setup B: proton energies 127.2-185.9 MeV) depth, respectively. LET values at the respective cell positions were derived from Monte Carlo simulations performed with the treatment planning system (TPS, RayStation). Dosimetric measurements were conducted to verify dose homogeneity and dose delivery accuracy. RBE values were derived for doses that resulted in 90 % (RBE ) and 10 % (RBE ) of cell survival, and survival after a 0.5 Gy dose (RBE ), 2 Gy dose (RBE ), and 6 Gy dose (RBE ).

Results: LET values at sample positions were 1.9, 2.1, 2.5, 2.8, 4.1, and 4.5 keV/µm. For the cell lines with high (α/ß) ratios (FaDu, HaCat), the LET did not impact on the RBE. For low (α/ß) cell lines (Du145, SKMel), LQ-derived survival curves indicated a clear correlation of LET and RBE. RBE values up to 2.9 and RBE values between 1.4 and 1.8 were obtained. Model-derived RBE predictions slightly overestimated the RBE for the high (α/ß) cell lines, although all models except the Jones model provided RBE values within the experimental uncertainty. For low (α/ß) cell lines, no agreement was found between experiments and model predictions, that is, all models underestimated the measured RBE.

Conclusions: The sensitivity parameter (α/ß) was observed to be a major influencing factor for the RBE of protons and its sensitivity toward LET changes. RBE prediction models are applicable for high (α/ß) cell lines but do not estimate RBE values with sufficient accuracy in low (α/ß) cell lines.
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http://dx.doi.org/10.1002/mp.14212DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7496287PMC
August 2020

Phantom design and dosimetric characterization for multiple simultaneous cell irradiations with active pencil beam scanning.

Radiat Environ Biophys 2019 11 20;58(4):563-573. Epub 2019 Sep 20.

Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria.

A new phantom was designed for in vitro studies on cell lines in horizontal particle beams. The phantom enables simultaneous irradiation at multiple positions along the beam path. The main purpose of this study was the detailed dosimetric characterization of the phantom which consists of various heterogeneous structures. The dosimetric measurements described here were performed under non-reference conditions. The experiment involved a CT scan of the phantom, dose calculations performed with the treatment planning system (TPS) RayStation employing both the Pencil Beam (PB) and Monte Carlo (MC) algorithms, and proton beam delivery. Two treatment plans reflecting the typical target location for head and neck cancer and prostate cancer treatment were created. Absorbed dose to water and dose homogeneity were experimentally assessed within the phantom along the Bragg curve with ionization chambers (ICs) and EBT3 films. LET distributions were obtained from the TPS. Measured depth dose distributions were in good agreement with the Monte Carlo-based TPS data. Absorbed dose calculated with the PB algorithm was 4% higher than the absorbed dose measured with ICs at the deepest measurement point along the spread-out Bragg peak. Results of experiments using melanoma (SKMel) cell line are also presented. The study suggested a pronounced correlation between the relative biological effectiveness (RBE) and LET, where higher LET leads to elevated cell death and cell inactivation. Obtained RBE values ranged from 1.4 to 1.8 at the survival level of 10% (RBE). It is concluded that dosimetric characterization of a phantom before its use for RBE experiments is essential, since a high dosimetric accuracy contributes to reliable RBE data and allows for a clearer differentiation between physical and biological uncertainties.
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http://dx.doi.org/10.1007/s00411-019-00813-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6768893PMC
November 2019