AbstractID: 8524 Title: Registration and normalization affect on IMRT Plan/Film QA
Purpose: To verify that the calculated dose distribution is delivered accurately during intensity-modulated radiation therapy (IMRT)
an automated Plan/Film validation protocol has been developed1. Precision of Plan/Film Normalization and Registration is being
analyzed in order to increase an accuracy of IMRT QA.
Materials and Methods: Bluebox (TARGETQA) film phantom and Radiation Therapy Film Dosimetry System (RIT) were used to
compare calculated (CORVUS) and delivered (MIMiC, NOMOS) dose distributions. To compensate for film dosimetry uncertainties
Plan Dose Scale Factor (PDSF) was corrected in high dose low gradient area. EDR–2 KODAK films were cut to fit into the phantom
and irradiated using Hybrid Patient Plans.
To assess the impact of normalization on Plan/Film analysis PDSF was gradually changed from it’s optimized value. To analyze how
registration points positioning affects Plan/Film registration accuracy they were shifted from its’ original positions.
Results: A percentage of image pixels with Plan/Film dose differences less than 5% was used as a criterion of acceptance. Total of
546647 pixels in each image was analyzed for Plan/Film dose differences. Mean dose difference was 0.49%, with 0.95% of the pixels
exceeding our criterion. Dose difference exceeding increased to 23.4% when registration point was moved away by 5 mm from it’s
correct position and to 33% when PDSF was decreased by 7.5% from it’s correct value.
Normalization and registration are important factors in Plan/Film analysis. They should be optimized to achieve reliable results in
IMRT QA.
1. A.Kapulsky et al., An Automated Phantom-Film QA Procedure For IMRT Treatments, AAPM 2001