A feasibility study of dynamic verification for tumor target delineation and dose delivery using a six degrees of freedom motion phantom

Background: the dynamic phantom is one of the best tools to study the impact ofmotion on tumor target delineation and absorbed dose verification during dosedelivery. materials and methods: this study, a 6-dof (degrees of freedom)phantom was designed following the stacked serial kinematics and assembled by sixcommercial motion stages to generate 6-dof motion, which were rotx (pitch,around x), roty (roll, around y), transz (anterior–posterior), rotz (yaw, around z),transy (superior–inferior) and transx (left–right). tumor targets were designed bysix plastic spheres for the delineation test. also, an ionization chamber arraydetector and rw3 solid water were combined to measure the absorbed dose fordose verification tests. results: the maximum translation speeds for linex andliney were 50mm/s and 35mm/s for linez, while the maximum rotationspeeds for rotx, roty, rotz were 5.33° per second, 6° per second and 15° persecond respectively. spiral-ct and 4d-ct images acquired in the static anddynamic states successfully showed the influences of tumor motion on targetdelineation. in the absorbed dose verification, all cases did not pass thegamma test; the pass rate for the 6-dof motion case was only 34.2% and thepass rates of all other cases were less than 90%. conclusion: the phantomdesigned in this study is able to simulate complex tumor motion and can be used tostudy the influence of tumor motion in radiotherapy.