TITLE:
Evaluation and Commissioning of Commercial Monte Carlo Dose Algorithm for Air Cavity
AUTHORS:
Hideharu Miura, Norihisa Masai, Kouichi Yamada, Junichi Sasaki, Ryoong-Jin Oh, Hiroya Shiomi, Muhammad Nauman Usmani, Toshihiko Inoue
KEYWORDS:
Monte Carlo; Pencil Beam; Air Cavity; Treatment Planning
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.3 No.1,
January
27,
2014
ABSTRACT: The purpose of
this study was to compare the Pencil Beam (PB) with Monte Carlo (MC) calculated dosimetric results using phantoms for
air cavity region. Measurements in Tough water phantom with air gaps were used
to verify the calculated dose. The plane-parallel ionization chamber was moved
from 2 mm to 20 mm behind air gap. Calculations were performed for various air gaps
(1.0, 2.0, 3.0 and 4.0 cm) and field sizes (4.2 × 4.2, 6.0 × 6.0 and 9.8 × 9.8 cm2). The lateral missing tissue
measurement was performed using the radiochromic RT-QA film. Dose difference
between PB and chamber measurement near an air gap was greater for smaller
field size, larger air gap thickness, and shallower depth behind air gap. As
the distance from the phantom edge became shorter, the dose differences of the
PB calculation and film measurement became larger. MC calculations were found
within 3% agreement to the measured dose distributions. Our results demonstrate
an excellent agreement between ionization chamber and radiochromic RT-QA film
measurements and MC calculations.