Purpose: The entrance beam fluence of therapeutic proton scanning
beams can be monitored using a gantry-attachable plastic scintillating plate
(GAPSP). This study evaluated the clinical application of the GAPSP using
amethod that measures intensity modulated proton therapy (IMPT) beams for
patient treatment.
Methods: IMPT beams for the treatment of nine patients, at sites
that included the spine, head and neck, pelvis, and lung, were measured using
the GAPSP, composed of an EJ-212 plastic scintillator and a CMOS camera. All energy
layers distinguished by the GAPSP were accumulated to determine the dose
distribution of the treatment field. The evaluated fields were compared with
reference dose maps verified by quality assurance.
Results: Comparison of dose distributions of evaluation treatment
fields with reference dose distributions showed that the 3%/1 mm average gamma
passing rate was 96.4%, independent of the treatment site, energy range and
field size. When dose distributions were evaluated using the same criteria for
each energy layer, the average gamma passing rate was 91.7%.
Conclusions: The GAPSP is a suitable, low-cost
method for monitoring pencil beam scanning proton therapy, especially for
non-spot scanning or additional collimation. The GAPSP can also estimate the
treatment beam by the energy layer, a feature not common to other proton
dosimetry tool.
Seonghoon Jeong
Proton Therapy
Center, National Cancer Center, Goyang, Republic of Korea
Myonggeun Yoon⁎ , Jaehyeon Seo
Department of
Bio-Convergence Engineering, Korea University, Seoul, Republic of Korea
Kwangzoo Chung,⁎ , Sung Hwan Ahn , Boram Lee,
Department of Radiation
Oncology, Samsung Medical Center, Seoul, Republic of Korea
Physica
Medica 77(2020)181-186