Evaluation of Dose Distribution in Field Junction Area and Risk Organs for Supine and Prone Treatment Techniques in Craniospinal Irradiation

OBJECTIVE The aim of this study is to investigate dose distributions in junction regions and organs at risk in asymmetric collimation techniques and divergence matching techniques used in craniospinal treatments. METHODS In the anthropomorphic phantom, the junction area and organ at risk doses were determined for eight different craniospinal irradiation (CSI) techniques with the help of thermoluminescent dosimeter (TLD) and treatment planning system (TPS). These techniques differ in terms of the parameters of the table being angled/un-angled, using block/multi-leaf collimator, and being in supine/prone position. RESULTS There was no statistically significant difference between TPS and TLD doses of all techniques. The lowest doses of cribriform plate are 1.82 Gy in PM, and 1.84 Gy in PAM. The lowest dose in lenses is 0.19 Gy in PB. The lowest dose of thyroid is 1.27 Gy in PB and highest dose of PAM is 1.35 Gy. Average small intestine dose of 1.92 Gy in non-table angle decreases to 1.08 Gy with table angle. The highest kidney doses are 0.14 Gy in SM. Ovaries take an average dose of 0.09 Gy in non-table angled and average of 0.13 Gy in table-angled techniques. CONCLUSION It has been determined that CSI technique in supine without table angle and protected with special blocks, is superior to other techniques due to its better dose homogeneity in treatment volume, providing immobilization in daily use and ease of application

Evaluation of air cavities on dose distributions with air-filled apparatuses having different volumes using Gafchromic EBT3 films in brachytherapy

WOS: 000450073600010Aim: The data used in brachytherapy planning are obtained from homogeneous mediums. In practice, the heterogeneous tissues and materials affect the dose distribution of brachytherapy. It is aimed to investigate the effect of air cavities on brachytherapy dose distribution using a specially designed device. Material and methods: In this study, the special device designed with different volumes of air and water to be irradiated and measured at different depths using EBT3 Gafchromic films. EBT3 Gafchromic films were preferred for this study because they can be cut to the shape of the experimental geometry, are water resistance and double directional usability. Results: In our study, sudden dose increases and decreases were observed at the water-air-water interfaces. Increases were 9, 11.8 and 15% in the 13, 18 and 22 mm apparatus, respectively. These effects were expected and the results were consistent with the literature and within the tolerance limits stated in the clinical dose guidelines. The most important result is that the percent depthdose curve of the radiation passing through the air to the water and only passing through the water medium is different The average differences were 1.97, 2.97 and /31% for the 13, 18 and 22 mm apparatus, respectively. Conclusion: Although the effect of heterogeneity may be neglected according to clinical guidelines, it is suggested that the dose effect of heterogeneity is taken into account so that the dose can be estimated sensitively. Brachytherapy plans using dose data without unisidering air gaps may cause erroneous dose distributions due to heterogeneity of tissue

Evaluation of the effect of intensity‐modulated radiotherapy (IMRT) and volumetric‐modulated arc radiotherapy (VMAT) techniques on survival response in cell lines with a new radiobiological modeling

Abstract Background The optimal radiobiological model, which assesses the biological effects of novel radiotherapy techniques that concurrently modify multiple physical factors, has not yet been defined. This study aimed to investigate the impact of intensity‐modulated radiotherapy (IMRT) and volumetric‐modulated arc therapy (VMAT) on cellular response in head and neck cancer and melanoma models. Methods Clonogenic analysis, DNA double‐strand break analysis, apoptosis, and cell cycle analysis were performed on cancer stem cell models, cancer models, and normal tissue cell models to assess radiation sensitivity. Results The segmented radiation approach used in IMRT applications enhanced radiosensitivity and cytotoxicity in the cancer models, while changes in dose rate had varying effects on cytotoxicity depending on the tumor cell type. VMAT increased cellular resistance, favoring treatment outcomes. Conclusions The biological processes were influenced differently by dose rate, IMRT, and VMAT depending on the tumor cell type. The selection of the most appropriate technique is crucial in representing new radiotherapy approaches. The obtained data can serve as a model to address clinical questions in daily practice. The integration of non‐standard outcomes with standard applications should be considered in clinical settings