Comparison of linac-based fractionated stereotactic radiotherapy and tomotherapy treatment plans for intra-cranial tumors

Abstract: This study compares and analyzes stereotactic radiotherapy using tomotherapy and linac-based fractionated stereotactic radiotherapy in the treatment of intra-cranial tumors, according to some cases. In this study, linac-based fractionated stereotactic radiotherapy and tomotherapy treatment were administered to five patients diagnosed with intra-cranial cancer in which the dose of 18—20 Gy was applied on 3—5 separate occasions. The tumor dosing was decided by evaluating the inhomogeneous index (II) and conformity index (CI). Also, the radiation-sensitive tissue was evaluated using low dose factors V₁, V₂, V₃, V₄, V₅, and V₁₀, as well as the non-irradiation ratio volume (NIV). The values of the II for each prescription dose in the linac-based non-coplanar radiotherapy plan and tomotherapy treatment plan were (0.125±0.113) and (0.090±0.180), respectively, and the values of the CI were (0.899±0.149) and (0.917±0.114), respectively. The low dose areas, V₁, V₂, V₃, V₄, V₅, and V₁₀, in radiation-sensitive tissues in the linac-based non-coplanar radiotherapy plan fell into the ranges 0.3%—95.6%, 0.1%—87.6%, 0.1%—78.8%, 38.8%—69.9%, 26.6%—65.2%, and 4.2%—39.7%, respectively, and the tomotherapy treatment plan had ranges of 13.6%—100%, 3.5%—100%, 0.4%—94.9%, 0.2%—82.2%, 0.1%—78.5%, and 0.3%—46.3%, respectively. Regarding the NIV for each organ, it is possible to obtain similar values except for the irradiation area of the brain stem. The percentages of NIV_10%, NIV_20%, and NIV_30% for the brain stem in each patient were 15%—99.8%, 33.4%—100%, and 39.8%—100%, respectively, in the fractionated stereotactic treatment plan and 44.2%—96.5%, 77.7%—99.8%, and 87.8%—100%, respectively, in the tomotherapy treatment plan. In order to achieve higher-quality treatment of intra-cranial tumors, treatment plans should be tailored according to the isodose target volume, inhomogeneous index, conformity index, position of the tumor upon fractionated stereotactic radiosurgery, and radiation dosage for radiation-sensitive tissues.