Dosimetric Consequences From Minimal Displacements In Abpi With Savi Applicators

Purpose: To highlight the importance of provide proper solid immobilization initially and in every
treatment in ABPI with brachytherapy. Materials and Methods: 100 patients receiving brachytherapy
treatments in ABPI using the Savi applicators were considered for the study. The CT scans used in the
initial plan was compared with every scan obtained before each treatment. Each of these scans were exported in the planning system and registered with the initial plan. Dosimetric evaluations were
performed with their consequences to the ribs and the skin surface. Results: Making the dosimetric
comparison for the critical points on the ribs and skin due to very small changes in the interfractionation
position revealed dramatic differences in the maximum dose to these critical organs. The
cavity's volume manifested changes between fractions as well as the distances to the two critical
organs. Therefore the maximum dose manifested variance between 10 and 32 in both of the sites
Conclusions: This study demonstrates that using CT scan before each treatment will minimize the risk
of delivering undesired high doses to the critical organs. This reveals the urgent need of increasing and
improving the immobilization methods when treating ABPI with Savi. In 30 of the cases re-planning was
necessary between fractions therefore we conclude that in each case the treatment and planning teams
must be prepared for re-plan as needed.