METHODS
Marker placed 10 patient's films were taken, transferred to
planning system and distance between markers was measured.
Port images were taken by EPID and Template Matching option
was used for matching ports with digitally reconstructed
radiograph. The distance between markers and the changes
were determined with analytic process. Systematical and random
set-up errors were determined.
RESULTS
No important changes on marker positions and no radiation
toxicity was observed. Verifying the treatment positions according
to markers in terms of position correction gain was
better compared to verifying according to bone anatomy
(p<0.05). Target focused position verifying was the best way
for reducing both systematical and random set-up errors.
CONCLUSION
The decrease in standard deviation of systematical and random
errors provides statistically meaningful decrease in minimum
PTV margins.
Keywords: Gold marker; a-Si EPID; elektronic portal imaging; setup errors
