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The purpose of the study was to compare the results of gamma value based film analysis according to the used type of self-developer film and software product.

The aim of this study was to investigate the radiobiological effects of flattening filter (FF) and flattening filter-free (FFF) modes of linear electron accelerators and to understand whether there is any difference between the effects of these modes. We evaluated the number of chromosome aberrations following irradiation of lymphocytes from healthy volunteers with X-ray photons at two energy levels, 6 and 10 MV; the dose rate ranged between 5.50 and 23.08 Gy/min and absorbed doses ranged between 0.5 and 8 Gy. A 60Co curve was employed for comparison. Metaphases from the lymphocyte cultures were prepared using standard cytogenetic techniques and chromosome analysis was performed. Our results allow the performance of biodosimetry at higher energies and doses than the currently used reference dosimetry. We observed significant differences in aberration frequencies when different irradiation techniques were used. FFF mode has a higher radiobiological effect than the FF mode. Linear-quadratic dose response calibration curves were constructed and relative biological effectiveness (RBE) values were calculated. Average RBE values using 6 MV (5.50 Gy/min) as a reference radiation were 1.28 for 60Co γ irradiation, 1.11 for 6 FFF and 0.79–0.92 for 10 FFF. Since there are compelling differences between radiation modalities in cases of hypofractionation, these results may be even more important in a therapeutic situation. In case of an accidental overdose of a patient, use of the appropriate calibration curves for biodosimetry are also essential for quantifying the overdose. [ABSTRACT FROM AUTHOR]

In the case of dynamic radiotherapy plans, the fractionation schemes can have dosimetric effects. Our goal was to define the effect of the fraction dose on the plan quality and the beam delivery.

We present evaluation of junction of coplanar external beam photon fields and its portal dosimetric analysis for breast cancer with positive lymph nodes. In our work, we compared twelve patients affected by breast cancer with axillary and supraclavicular lymph nodes, using conformal external beam plans from a dosimetric point of view. 3-3 plans were prepared per patient. Three methods were used for the conformal technique to investigate the potential of lymph nodes treatment field's collimations. During the evaluation of the portal dosimetry images, it was concluded that the junction plane at isocenter appeared as a discrete coldline, when fitted the regional field with or without collimation manually and by the software. However, the coverage of the isocenter plane is strongly influenced by the linear accelerator and the fitted field edges. Based on our results, in order to avoid uncertainties arising from field junctions and the overdosed areas of the target volume, it is more appropriate to choose another advanced irradiation technique such as intensity-modulated radiation therapy.

In treatment planning of small-sized lung tumors treated with stereotactic body radiotherapy (SBRT) in Eclipse treatment planning system with the Normal tissue objective (NTO) tool sharp dose gradients beyond the target volume can be achived. NTO has 5 variable parameters, so it is difficult to know which settings are optimal. The purpose of this study was to characterize the effects of changing NTO parameters on lung SBRT dose distributions. Ten lung SBRT cases were replanned using different NTO parameters. Dose calculation was performed using AAA and AXB algorithms as well. Differences between AAA and AXB plans were statistically significant. Plans were evaluated based on plan quality metrics. According to this analysis the fall-off of 0.15 and the priority of 500 have satisfied our institutional criteria best. Using NTO during planning is recommended in clinical practice.

Flattening filter free mode (FFF) has been introduced in radiotherapy during the past decades, however, not much has been reported on its radiobiological effect. The purpose of our study was to compare the radiobiological effects of flattening filter and flattening filter free photon beams on chromosomal aberrations in peripheral blood lymphocytes. In our study the blood of the same healthy donor was irradiated with linear accelerator using both conventional flattening filter (FF) and FFF photon beams at dose rate of 3.57-23.08 Gy/min, using 6 or 10 MV. The dose-response calibration curves for dicentric + ring chromosomes induced by irradiation were fitted with linear-quadratic model. CABAS (Chromosomal Aberration Calculation Software) was used to prepare the curves. The coefficients and equations of the curves were calculated and compared with the results of other authors. We found significant differences in the number of aberrations at different irradiation parameters. Based on our results, FFF mode has a 10-20% higher biological effect than FF mode. These results can be used during radiotherapy or to estimate the biological doses in case of an accidental exposure to radiation.

The aim of the study was to compare the different stereotactic treatment plans and dose calculation algorithms for small targets with film dosimetry in anthropomorphic phantom. Treatment plans were prepared for multiple targets with single setup isocenter. Plans for three different irradiation techniques were generated using conformal arc with four non-coplanar arcs, RapidArc with two coplanar full arcs and RapidArc with four non-coplanar arcs in the Varian Eclipse v13.7.16 TPS. Conformal arc and RapidArc plans were calculated using AAA, Acuros XBDm and XBDw algorithms. Conformity index, gradient index and dose maximum were calculated for all PTVs. All measurements were made on the Varian TrueBeam linear accelerator. Comparison between computed and measured dose distributions was performed with gamma evaluation criteria of 3%, 3 mm; 3%, 1 mm and 2%, 2 mm. According to our results, the Eclipse AAA and AXB algorithms provide accurate dose distributions for homogeneous cranial irradiation.

Lung cancer is known for its outstanding incidence and mortality rates. One of the cornerstones of the treatment of this disease is radiation therapy. A remarkable development was observed in this field through the latest decades. Intensity-modulated and image-guided radiotherapy (IMRT and IGRT) are now widely accessible in Hungarian centers, and should be increasingly applied in case of thoracic irradiations as well. Application of modern radiotherapy techniques in the treatment of lung cancer allows better clinical results and lower rates of side effects. In this work the authors give an overview of this above mentioned development regarding different clinical stages.

In this paper we present our early experience with a method for the management of respiratory motion in radiotherapy for early-stage lung cancer. Forty-six patients were irradiated with a total dose of 60 Gy. Tumor response on control CT, survival, local and distant progression as well as early and late side effects were registered. Complete and partial remission, stable and progressive disease was 17 (37.0%), 15 (32.6%), 11 (23.9%) and 3 (6.5%). Isolated local recurrence and distant metastasis appeared in 4 (8.7%) and 2 (4.3%) cases, while simultaneous local and distant progression was diagnosed in 3 (6.5%) patients. The probability of 2-year local recurrence-free, progression-free, and overall survival was 76.8%, 64.0%, and 83.2%. Grade 1 (G1) and G2 early side effects occurred at 15 (32.6%) and 3 (6.5%) patients without ≥G3 side effects. G1 and G2 late side effects were observed in 10 (21.7%) and 7 (15.2%) cases. G1-2 post-irradiation fibrosis occurred in 11 (23.9%) cases. Twenty months after the irradiation, G5 respiration failure was developed in one patient. The implemented technique of respiratory motion management for the radiotherapy of early-stage lung cancer resulted in promising local freedom from relapse and survival with favorable side effect profile. Further follow-up is needed to assess longterm side effects and survival results.

The aim of our work is to present the imaging techniques used at the National Institute of Oncology for taking into consideration the breathing motion at radiation therapy treatment planning. Internationally recommended imaging techniques, such as 4D CT, respiratory gating and ITV (Internal Target Volume) definition were examined. The different imaging techniques were analysed regarding the delivered dose during imaging, the required time to adapt the technique, and the necessary equipment. The differences in size of PTVs (Planning Target Volume) due to diverse volume defining methods were compared in 5 cases. For 4D CT breath monitoring is crucial, which requires special equipment. To decrease the relatively high exposure of 4D CT it is possible to scan only a few predefined breathing phases. The possible positions of the tumour can be well approximated with CT scans taken in the inhale maximum, the exhale maximum and in intermediate phase. The intermediate phase can be exchanged with an ordinary CT image set, and the extreme phase CT images can be ensured by given verbal instructions for the patient. This way special gating equipment is not required. Based on these 3 breathing phases an ITV can be defined. Using this ITV definition method the margin between the CTV (Clinical Target Volume) and the PTV can be reduced by 1 cm. Using this imaging protocol PTV can be reduced by 30%. A further 10% PTV reduction can be achieved with respiratory gating. In the routine clinical practice respiratory motion management with a 3-phase CT-imaging protocol the PTV for early-stage lung cancer can be significantly reduced without the use of 4D CT and/or respiratory gating. For special, high precision treatment techniques 4D CT is recommended.