RT Journal Article
SR Electronic
T1 Comparison of the Characteristics of Two Types of Parallel-plate Ionization Chamber Under Small-field Electron Irradiation
JF Anticancer Research
JO Anticancer Res
FD International Institute of Anticancer Research
SP 1967
OP 1972
DO 10.21873/anticanres.16356
VO 43
IS 5
A1 YANAGI, YUYA
A1 MONZEN, HAJIME
A1 KUBO, KAZUKI
A1 SUGIYAMA, JUNKO
A1 NOMA, KAZUO
A1 ITO, TAKAAKI
A1 SAKAI, YUSUKE
A1 NAKAMURA, KENJI
A1 KIDA, TETSUO
A1 DOI, HIROSHI
A1 NISHIMURA, YASUMASA
YR 2023
UL http://ar.iiarjournals.org/content/43/5/1967.abstract
AB Background/Aim: This study compared two types of parallel-plate ionization chamber to clarify the pitfalls of dosimetry in electron radiation therapy. Materials and Methods: The ion recombination correction factor and polarity effect correction factor, sensitivity, and percentage depth doses (PDDs) of PPC05 and PPC40 parallel-plate ionization chambers were compared in a small-field electron beam. The output ratios were measured for 4-20 MeV electron beams with field sizes of 10 cm × 10 cm, 6 cm × 6 cm, and 4 cm × 4 cm. Furthermore, the films were placed in water and positioned in the beam with their surface perpendicular to the beam axis, and lateral profiles were obtained for each beam energy and each field. Results: Regarding PDDs, at depths greater than the peak dose, the percentage depth dose for PPC40 was smaller than that for PPC05 in small fields and at beam energies greater than 12 MeV, which could be attributed to the lack of lateral electron equilibrium at small depths and multiple scattering events at large depths. The output ratio of PPC40 was approximately 0.025–0.038, which was lower than that of PPC05 in a 4 cm × 4 cm field. For large fields, the lateral profiles were similar, regardless of the beam energy, however, for small fields, the flatness of the lateral profile was beam energy dependent. Conclusion: The PPC05 chamber, which has a smaller ionization volume, is therefore more suitable than the PPC40 chamber for small-field electron dosimetry, in particular at high beam energies.