Akciğer Kanserlerinde Stereotaktik Ablatif Beden Radyoterapisinin Toksisite ve Doz - Yanıt İlişkisinin Matematiksel Model ile Görüntü ve Dozimetrik Analizi

Abstract

In conventional radiotherapy applications, clinicians and physicist rely upon mathematical dose - response models for applied doses to tumor and periphery healthy tissues. However in stereotactic ablative body radiotherapy (SABR), reliable dose - response model is controversial because of the changing treatment techniques. In this thesis study, the effects of SABR on to diseased area and healthy tissues in lungs were examined and based a mathematical dose response relation for non smal cell lung cancer (NSCLC). For this reason, 19 appropriate NSCLC patients with treated in Cyberknife were chosen. The part of 7 patients in this 19 patients were anayzed dosimetrically on to Brainlab ExacTrac gating phantom with EBT3 gafchromic films. Compared doses for GTV with minimum 0.90 %, maximum 1.02 % and mean 0.96 %, normal lung volume 4.01 % found statistical significantly less compared to the treatment planning system (TPS) results. Chest wall was also examined, and less then TPS about 2.22 %, but it is not statistically significant. Conturs of residues and ground glass opasities were drawn by radiation oncologists on follow - up computer tomography (CT) scans and they compared to the isodose lines in treatment CT with deformable registration. In comparasion, residues were taken as treatment response and ground glass opasities were taken as radiation induced lung damage (RILD), showed polynomial function behaviour to dose values to their fractions in these doses. First 6 months after treatment, RILD curve is likely to be a cubic and treatment response curve is likely to be a quartic polynomial. On the other hand, second 6 months after treatment, RILD curve is likely to be a quadratic and treatment response curve is likely to be a cubic polynomial. Lastly we also compared Hounsfield Unit (HU) changes in follow - up CT’ s to the treatment CT as a funtion of isodose bins in first 6 monts, second 6 months and third 6 months after treatment finished. Analyses of follow - up BT’ s showed that both imaging analyses and mathematical HU modelling give nearly same results. It was observed that, 40 Gy is important for treatment activity and 35 Gy is important for RILD possibility. Using mathematical HU modelling for seeing treatment activity and RILD may possibility be an effective and useful technique in cylindrical colimator based robotic stereotactic ablative lung radiotherapy.