1. Hsiao-Ju Fu Yuk-Wah Tsang Chih-Chia Chang
The isodose curve of the simulated phantom for breast cancer patients treated with field-in-field （FIF） and irregular surface compensator （ISC）
Hsiao-Ju Fu Yuk-Wah Tsang Chih-Chia Chang
Department of Radiation Oncology, Ditmanson Medical Foundation Chia-Yi Christian Hospital
Introduction:
PBC（ Pencil Beam Convolution） 、 AAA （Anisotropic Analytical Algorithm） and Acuros were adopted to calculate the surface dose on the phantom. The calculation errors of the three algorithms were evaluated using the result of the measurement by ultrathin TLD and EBT2 films.
Materials and methods:
Treatment plans with a prescribed dose of 180 cGy and seven fields were designed. Grid size was selected in 2.5㎜. IMRT plan and calculation surface doses by the three algorithms using Eclipse treatment planning system were generated in the phantom that simulated a typical nasopharyngeal carcinoma with bilateral neck adenopathy. Then ultrathin TLD and EBT2 films were used to measure the surface dose.
Result :
In this experiment the variance coefficient of ultrathin TLD was within 3% error. The points
on calibration curve of Gafchromic film were within 1% error. Two readings of the two
measurement tools showed a good linearity relationship. The errors between the
calculation and the measurement with PBC、AAA and Acuros in the phantom were 3.72
％、5.25％ and -2.31％ for ultrathin TLD, respectively；-10.09％、3.52％ and 3.06％ for
EBT2 films, respectively.
Conclusion and Discussion :
From the experimental results, PBC has the most discrepancy between calculation and
measurement results while Acuros has the most accurate results and AAA always shows
overestimated. The future work for this research will find out the most correct algorithm
and modify the contour of the body to evaluate the skin dose using the treatment planning
system directly and get the skin dose indeed affecting the skin reaction.
Key words: surface dose, ultrathin TLD, Gafchromic film, Pencil Beam Convolution,
Anisotropic Analytical algorithm, Acuros