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    An institutional experience: quality assurance of a treatment planning system on electron beam
    (Kare Publ, 2013) Yaray, Kadir; Ozguven, Yildiray; Alkaya, Fadime; Yucel, Birsen; Soyuer, Serdar
    OBJECTIVES This study aims to application of the IAEA TRS-430 QA procedures of Eclipse (TM) v7.5 TPS for electron energies. In addition, the trends of the deviations found in the conducted tests have been determined. METHODS The calculations of TPS and measurements irradiations of the treatment device have been compared. As a result, the local dose deviation values and their confidence limit values have been obtained. RESULTS All confidence limit values were detected that it was increased depending on expanding depth. But each confidence limit values were found to show different change depending on expanding field size. Results of CT based inhomogeneity corrections and complex surface shapes tests were found outside tolerances, especially delta 3. CONCLUSION The QA of our clinic's TPS has been done and it has been found that there aren't drawbacks in its use in treatment. Only the errors found in our study for the parameters used in treatment planning has to be considered.
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    Concentration modulated skin marker for radiotherapy treatment planning process
    (ELSEVIER SCI LTD, 2013) Ozguven, Yildiray; Yucel, Birsen; Ozyurek, Betul; Karakus, Gulderen; Ozguven, Yucel
    Background and purpose: For conformal radiotherapy, it is feasible to achieve high accuracy in contouring the outline of the target volume in treatment planning process. In contouring process, target volume is occasionally defined by means of either surgical clips or skin marker during patient anatomical data acquisition. Treatment planning systems are predicting invalid radiation dose distributions by using surgical clips and skin marker within the patient. Purpose of this study is the production of new skin marker which affects less dose distributions of electron beam. Materials and methods: The influences of lead and commercial markers on dose calculations in a 3D treatment planning systems were investigated in terms of electron beam energy and dose profile depth. Dose deviation with commercial marker was observed to smaller than lead marker. However this dose deviation was still at big value. In order to reduce of this value, barium sulfate suspension and ultrasound gel were mixed with different volumetric ratio. With the purpose of acception the most suitable marker for radiation therapy, obtained new suspensions were investigated in terms of visibility and dose deviation. Results: B:G/1:10 marker was determined to cause optimum visibility and the lowest dose deviation on dose calculations in terms of electron beam energy and dose profile depth. Conclusions: Appropriate marker, mixture of substances such as barium sulfate suspension and ultrasound gel can be produced. This marker is both ease of usage and practical and economical. Each clinic can prepare marker which is peculiar to suspension with different concentration of substance for specific visibility. But, it should be taken into account resultant dose deviation to beam calculation depending on barium sulfate concentration. (C) 2012 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
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    The effects of therapeutic x-ray doses on mechanical, chemical and physical properties of poly methyl methacrylate
    (INFORMA HEALTHCARE, 2013) Dogan, Derya Ozdemir; Ozguven, Yildiray; Karakus, Gulderen; Sahin, Onur; Polat, Nilufer Tulin; Yucel, Birsen; Dogan, Mansur
    Aim. The aim of this study was to investigate the effect of radiation doses very close to the human dose for oral cancers on mechanical, chemical and physical properties for poly methyl-methacrylate (PMMA). Methods. PMMA samples were divided into four different groups: no irradiated group, 25-Gy irradiated group, 50-Gy irradiated group and 75-Gy irradiated group. Each group contained nine samples. After 24 h, a three-point loading test was applied to each PMMA groups. The transverse strength and the elastic modulus were calculated using the test results. The results were analyzed statistically by using one-way analysis of variance. The structural characterizations of the PMMA samples were carried out by a Fourier Transform Infrared (FTIR) spectrophotometer to evaluate the chemical structure differences. Results. The transverse strength values of 25-Gy, 50-Gy and 75-Gy radiation groups were significantly higher than that of the no radiation group (p < 0.05). There was no significant difference among the elastic modulus values of the study groups (p > 0.05). The FTIR findings demonstrated that the irradiation process did not change the chemical structure of the PMMA polymeric materials. Conclusion. The therapeutic radiation doses increase the mechanical properties of the PMMA; however, the chemical and structural properties have no effect. When the findings of this study are taken into account, it can be said that patients can wear dentures during the radiotherapy.
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    The Impact of Everolimus and Radiation Therapy on Pulmonary Fibrosis
    (Mdpi, 2020) Eren, Mehmet Fuat; Eren, Ayfer Ay; Sayan, Mutlay; Yucel, Birsen; Elagoz, Sahende; Ozguven, Yildiray; Vergalasova, Irina
    Background and objectives:Everolimus (EVE) is a mammalian target of the rapamycin (mTOR) inhibitor that is widely used in cancer patients. Pulmonary toxicity, usually manifesting as interstitial pneumonitis, is a serious adverse effect of this drug. Radiation therapy, which is often administered in conjunction with chemotherapy for synergistic effects, also causes pulmonary fibrosis. In view of pulmonary damage development in these two forms of cancer treatment, we have examined the effect of EVE administration individually, in combination with radiation given in varying sequences, and its relation to the extent of pulmonary damage.Materials and Methods:We performed an experimental study in albino rats, which were randomized into five groups: (1) control group, (2) EVE alone, (3) EVE 22 h after radiation, (4) EVE 2 h after irradiation, and (5) only radiation. Sixteen weeks after thoracic irradiation, rat lung tissue samples were examined under light microscopy, and the extent of pulmonary damage was estimated. After this, we calculated median fibrosis scores in each group.Results:The highest fibrosis score was noted in Group 4. Among the five groups, the control group had a significantly lower median fibrosis score compared to the others. When the median fibrosis score of the group that received concurrent EVE with radiation therapy (RT) (Group 4) was compared with that of the control group, the difference was statistically significant (p= 0.0022). However, no significant differences were achieved among the study groups that received EVE only or RT only, whether concurrently or sequentially (p> 0.05).Conclusion:EVE is an effective treatment option for the management of several malignancies and is often combined with other therapies, such as radiation, for a more efficient response. However, an increased risk of pulmonary fibrosis should also be anticipated when these two modalities are combined, as they both can cause pulmonary damage, especially when administered concurrently.