Inovativne tehnike kraniospinalne iradijacije - kontrola doze na spojevima zračnih snopova
Keywords:craniospinal irradiation, geometric inaccuracy, dose distributin, overdosage, subdosage
A particularly important issue in delivery of craniospinal irradiation (CSI) is reduction of geometric inaccuracy at the beam junctions. Overlapping at the beam junctions can result in overdosage (Hot Spot) and serious normal tissue complication (NTCP - Normal Tissue Complication Probability). Gaping at the beam junction can result in underdosage (Cold Spot) significantly increase the possibility of tumor recurrence (TCP - Tumor Control Probability). A modification of the craniospinal irradiation technique was proposed with the aim to improve dose control at the beam junctions and reduce appearance of cold and hot spots.
Based on results obtained by the portal imaging study carried out in the actual treatment situation, a simulation of the geometric inaccuracy and its effect to dose distribution was made. Results are compared with the results obtained by simulation of hot and cold spots in the treatment plan.
Results do not show significant deviation in the distribution of radiation dose, nor the deviation of the local dosage maximum at the beam junction. There is noticeable deviation of the dose distribution within few individual fractions as a result of geometric inaccuracy during treatment delivery reduced according to local protocol. The proposed modification, combined with a strict portal verification protocol, improves the irradiation technique regarding to dose control at the beam junctions.
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