Tüm Beden Işınlamalarında Farklı Tedavi Planlama Tekniklerinin Dozimetrik Olarak Karşılaştırılması

Abstract

The purpose of Total Body Irradiation (TBI) in radiotherapy is to suppress the immune system of the patient by destroying bone marrow cells, prepare the host for bone marrow transplantation and enhance the antitumor effect. Addition of TBI to chemotherapy improves treatment outcomes by delivery of a homogeneous dose to the entire body. In this study, dosimetric comparison of three different TBI techniques which can be applied in a standard linear accelerator chamber is studied. Extended Source to Surface Distance (SSD) Field-in-Field (I), Extended SSD Volumetric Modulated Arc Therapy (VMAT) (II) and Standard SSD VMAT (III) techniques are chosen for this comparison. The purpose of selecting these three techniques is to avoid the use of patient specific dose modulation equipment thus avoiding the risk of error, further workload and increased setup time. Percent depth dose and dose profile measurements were taken under treatment conditions for each specified technique. After the treatment plans were generated, dose homogeneity and critical organ doses were confirmed on the Rando phantom with radiochromic films and optically stimulated luminescence dosimetry (OSLD). The treatment dose for the plans prepared with three different techniques was 12 Gy. Mean lung dose in the first two techniques were both 8.5 Gy; In technique III, it was 7 Gy. The gamma index (5%/5 mm) was used for the analysis of radiochromic films and the passing rates for the techniques I, II and III were found to be 90%, 87% and 94% respectively. OSLD results were within ± 5% agreement between measurements and the calculations for the first two techniques. It was found to be within ± 3% for technique III. In conclusion, all three techniques are feasible to be applied in clinic. The Standard SSD VMAT technique is better in sparing lung tissue.