Yoğunluk Ayarlı Tüm Cilt Elektron Işınlama Tekniğinin Geliştirilmesi
Project no. 20037 · Status: Kapanmış (Yayın bekleniyor) · 2018
Summary
Objective: In total skin electron irradiation(TSEI) of the patients with higher abdominal thickness, the anterior skin areas other than the abdominal area move away from the treatment device and receive a different dose than that of the prescribed dose. It is aimed to eliminate the dose irregularity in the anterior skin areas by the intensity modulated total skin electron irradiation(IM-TSEI) method which is developed in this study. Method: First, the tissue equivalence of the black ABS material was determined. Abdominal thicknesses of 3, 6, 9, 12 and 15cm were simulated using human phantom and abdominal phantoms of different thicknesses produced with ABS. The properties of classical Stanford TSEI technique were determined and the characteristics of IM-TSEI technique were defined. In the IM-TSEI technique a new angle pair, 12FF, and treatment time were determined based on the thickness of the abdominal region at the anterior beam positions and the SSD was adjusted based on the sternum point. Since there were no contour irregularities such as abdominal thickness in the posterior treatment positions SSD was adjusted to the posterior waist point as in the conventional TSEI, and the treatment angle pair and treatment times creating a homogeneous profile were used. The parameters affected by abdominal thickness were determined and depth-dependent dose change measurements were performed. IM-TSEI application parameters for different abdominal thicknesses were determined by combined dose measurements and calculation of treatment times. The quality assurance of the IM-TSEI method was done using an anthropomorphic human phantom with 3, 6, 9, 12 and 15 cm abdominal thicknesses by TLD skin dose and intra-phantom film measurements. Results: As a result of statistical analyzes, it was determined that IM-TSEI method provided more homogeneous doses including abdominal region along the vertical axis by compensating for the external contour irregularities in the anterior region of the body at the thicknesses of 6cm and above according to TSEI technique with profile measurements.Human phantom skin dose measurements showed that IM-TSEI method provided more homogeneous dose distributions for all abdominal thicknesses compared to classical TSEI method and TSEI method did not meet homogeneity criteria for abdominal thicknesses of 9cm and above. The full treatment percentage depth dose curves of the two techniques were consistent with each other, and the intra-phantom doses were consistent with the TSEI technique doses. In addition, it was determined that there was no statistically significant difference between the two techniques in abdominal thicknesses of less than 9 cm regarding average skin doses and body anterior skin doses, so both techniques could be used. In the IM-TSEI technique, the absolute dose difference between the anterior body region and the average skin doses was less than the prescribed dose at abdominal thicknesses of 9 cm and above. With TLD measurements, it was determined that intensity modulation by IM-TSEI technique corrected irregularities in the anterior body surface doses due to abdominal thickness. Conclusion: Although IM-TSEI technique can be used safely in all abdominal thicknesses, it is more advantageous than TSEI technique in thicknesses of 9 cm and above.