(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: To develop a multi-stage stereotactic radiosurgery delivery technique for large liver tumor using IMRT of linac platform.
Methods: A patient has a large (183 cm³) secondary liver tumor which was treated in fractionated treatment in linac was selected for this study. This large liver tumor was contoured and divided into 5 sub-targets with volumes ranging from 32.9-40.7 cm³. Each sub-target is to be treated sequentially in each other day. The prescription dose was 25 Gy to total target which is identical to prescription dose used in fractionated treatment. IMRT plans were retrospectively generated for the total liver tumor volume and optimized to achieve 95% coverage. Fluence of each beam was exported and split according to the radiological path length inside the sub-target. Beam fluence of staged plans for individual sub-targets was generated with the combination of the weighted beam fluence. Then, the sub-plan MLC sequence was generated with the sub-plan fluence of each beam. Dose-volume analysis was used to evaluate the PTV coverage and normal tissue sparing.
Results: The sum-up physical dose of multi-stage sub-plans is identical to the planed whole target dose. The physical normal tissue dose is similar between fractionated dose to the multi-stage dose. Compared with fractional plan, the high dose to sub-target in multi-stage treatment has better ablative effect to target area.
Conclusion: The Linac system can deliver a multi-staged conformal dose to treat large liver tumors. Physical dose coverage was shown to be similar compared to that of fractionated treatment. The biological dose may provide better target control.
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