Analysis of setup errors in the head and neck tumor by Tomo therapy using MVCT scanning / 实用肿瘤学杂志

ABSTRACT

Objective To investigate the setup errors of head and neck tumor patients with head mask-ing by TomoTherapy with megavoltage CT (MVCT),and to measure the CTV -PTV margins.Methods There were 34 patients with head and neck tumor .All patients had received MVCT scanning before radiation was deliv-ered.The MVCT images were registered with the kilovoltage CT (kVCT)images,the setup errors of the left -right (x),anterior-posterior(y),superior-inferior(z)and transverse profile rotation(Roll)were obtained by matc-hing MVCT with kVCT,followed by calculating the reasonable CTV -PTV margins with the formula M=2.5∑+0.7σ.Results Six hundred and forty MVCT images in total were received for the patients ,the systemic ±random errors in x,y,z and Roll directions were ( -0.15 ±0.55) mm,(0.30 ±0.56) mm,(0.35 ±0.71) mm and (-0.07 ±0.52)°,the CTV-PTV margin in x,y and z directions were 3.31 mm,5.32 mm and 3.35 mm.Con-clusion we demonstrate a theoretic foundation for our CTV -PTV margins in head and neck tumor patients by analyzing the setup errors ,and it also can provide necessary quality assurance for precise radiation .