Feasibility Study Of Multiple Isocenter Supine Overall Radiotherapy Technology In Clinical Craniospinal Axis Irradiation Application

Objective：This paper aims to improve patient compliance and comfort in craniospinal axisirradiation with better reliability in IMRT treatment. The feasibility of overall radiotherapytechnology based on supine situation in craniospinal axis irradiation has been explored.Methods:16patients with craniospinal axis irradiation are selected for this trial.Allpatients are fixed by thermoplastic head membrane and vacuum pad.9patients weresupine positioning with three isocenter and IMRT plan.7patients were prone positioningby ship type pillow fixed and fixed SSD plan.Move the bed in long axis after setup tocheck: whether the distances between3coordinate center are in accordance with that inplan;whether the coordinate centers coincide with the isocenter of machine.The coordinatecenter should only be shifted by bed movement in long axis to ensure the acquracy of beamconnection.CBCT images are collected and compared with target in CT plan by boneregistration and manual fine tuning fusion. Errors at X、Y、Z direction in three setup centersare counted. CBCT is performed before and after treatment once a week. Plans are verifiedbefore treatment.Results:14patients among16cases complete this trial, while2patients with proneposition give up the treatment as CBCT verification takes long time.Data results: the setuperror in supine position: Head and neck segment-X0.39±0.09cm，Y0.21±0.07cm，Z0.41±0.10cm; thoracic segments-X0.31±0.09cm， Y0.20±0.05cm， Z0.30±0.07cm;lumbosacral segments-X0.32±0.06cm，Y0.22±0.05cm，Z0.38±0.09cm;the setup errorin prone position：Head and neck segment-X0.57±0.16cm，Y0.27±0.13cm，Z0.55±0.22cm;thoracic segments-X0.40±0.17cm，Y0.26±0.09cm，Z0.37±0.13cm;lumbosacralsegments-X0.42±0.16cm，Y0.32±0.16cm，Z0.54±0.20cm. T value in neck segment is-3.77in X direction and-2.17in Z direction, p＜0.05; p＜0.05at X/Y/Z direction in lumbosacral segment means statistical significance.Conclusion: Supine positioning technology in craniospinal axis irradiation has advantagein setup error, patient compliance and comfort compared to traditional prone positioning.The operation process is simple and reliable. This paper provides the feasible basis forfurther clinical IMRT treatment.