PMID- 27370135
OWN - NLM
STAT- MEDLINE
DCOM- 20170303
LR  - 20181202
IS  - 2473-4209 (Electronic)
IS  - 0094-2405 (Linking)
VI  - 43
IP  - 7
DP  - 2016 Jul
TI  - Dual ring multilayer ionization chamber and theory-based correction technique for 
      scanning proton therapy.
PG  - 4150
LID - 10.1118/1.4953633 [doi]
AB  - PURPOSE: To develop a multilayer ionization chamber (MLIC) and a correction 
      technique that suppresses differences between the MLIC and water phantom 
      measurements in order to achieve fast and accurate depth dose measurements in 
      pencil beam scanning proton therapy. METHODS: The authors distinguish between a 
      calibration procedure and an additional correction: 1-the calibration for 
      variations in the air gap thickness and the electrometer gains is addressed 
      without involving measurements in water; 2-the correction is addressed to 
      suppress the difference between depth dose profiles in water and in the MLIC 
      materials due to the nuclear interaction cross sections by a semiempirical model 
      tuned by using measurements in water. In the correction technique, raw MLIC data 
      are obtained for each energy layer and integrated after multiplying them by the 
      correction factor because the correction factor depends on incident energy. The 
      MLIC described here has been designed especially for pencil beam scanning proton 
      therapy. This MLIC is called a dual ring multilayer ionization chamber (DRMLIC). 
      The shape of the electrodes allows the DRMLIC to measure both the percentage 
      depth dose (PDD) and integrated depth dose (IDD) because ionization electrons are 
      collected from inner and outer air gaps independently. RESULTS: IDDs for which 
      the beam energies were 71.6, 120.6, 159, 180.6, and 221.4 MeV were measured and 
      compared with water phantom results. Furthermore, the measured PDDs along the 
      central axis of the proton field with a nominal field size of 10 x 10 cm(2) were 
      compared. The spread out Bragg peak was 20 cm for fields with a range of 30.6 and 
      3 cm for fields with a range of 6.9 cm. The IDDs measured with the DRMLIC using 
      the correction technique were consistent with those that of the water phantom; 
      except for the beam energy of 71.6 MeV, all of the points satisfied the 1% dose/1 
      mm distance to agreement criterion of the gamma index. The 71.6 MeV depth dose 
      profile showed slight differences in the shallow region, but 94.5% of the points 
      satisfied the 1%/1 mm criterion. The 90% ranges, defined at the 90% dose position 
      in distal fall off, were in good agreement with those in the water phantom, and 
      the range differences from the water phantom were less than +/-0.3 mm. The PDDs 
      measured with the DRMLIC were also consistent with those that of the water 
      phantom; 97% of the points passed the 1%/1 mm criterion. CONCLUSIONS: It was 
      demonstrated that the new correction technique suppresses the difference between 
      the depth dose profiles obtained with the MLIC and those obtained from a water 
      phantom, and a DRMLIC enabling fast measurements of both IDD and PDD was 
      developed. The IDDs and PDDs measured with the DRMLIC and using the correction 
      technique were in good agreement with those that of the water phantom, and it was 
      concluded that the correction technique and DRMLIC are useful for depth dose 
      profile measurements in pencil beam scanning proton therapy.
FAU - Takayanagi, Taisuke
AU  - Takayanagi T
AD  - Hitachi Ltd., Hitachi Research Laboratory, Hitachi 319-1221, Japan.
FAU - Nihongi, Hideaki
AU  - Nihongi H
AD  - Hitachi Ltd., Hitachi Works, Hitachi 317-8511, Japan.
FAU - Nishiuchi, Hideaki
AU  - Nishiuchi H
AD  - Hitachi Ltd., Hitachi Research Laboratory, Hitachi 319-1221, Japan.
FAU - Tadokoro, Masahiro
AU  - Tadokoro M
AD  - Hitachi Ltd., Hitachi Works, Hitachi 317-8511, Japan.
FAU - Ito, Yuki
AU  - Ito Y
AD  - Hitachi Ltd., Hitachi Works, Hitachi 317-8511, Japan.
FAU - Nakashima, Chihiro
AU  - Nakashima C
AD  - Hitachi Ltd., Hitachi Works, Hitachi 317-8511, Japan.
FAU - Fujitaka, Shinichiro
AU  - Fujitaka S
AD  - Hitachi Ltd., Hitachi Research Laboratory, Hitachi 319-1221, Japan.
FAU - Umezawa, Masumi
AU  - Umezawa M
AD  - Hitachi Ltd., Hitachi Research Laboratory, Hitachi 319-1221, Japan.
FAU - Matsuda, Koji
AU  - Matsuda K
AD  - Hitachi Ltd., Hitachi Works, Hitachi 317-8511, Japan.
FAU - Sakae, Takeji
AU  - Sakae T
AD  - Proton Medical Research Center, University of Tsukuba, Tsukuba 305-8576, Japan.
FAU - Terunuma, Toshiyuki
AU  - Terunuma T
AD  - Proton Medical Research Center, University of Tsukuba, Tsukuba 305-8576, Japan.
LA  - eng
PT  - Journal Article
PL  - United States
TA  - Med Phys
JT  - Medical physics
JID - 0425746
RN  - 059QF0KO0R (Water)
SB  - IM
MH  - Air
MH  - Algorithms
MH  - Calibration
MH  - Computer Simulation
MH  - Electrodes
MH  - Monte Carlo Method
MH  - Phantoms, Imaging
MH  - Proton Therapy/*instrumentation/*methods
MH  - Radiometry/*instrumentation/*methods
MH  - Water
EDAT- 2016/07/03 06:00
MHDA- 2017/03/04 06:00
CRDT- 2016/07/03 06:00
PHST- 2016/07/03 06:00 [entrez]
PHST- 2016/07/03 06:00 [pubmed]
PHST- 2017/03/04 06:00 [medline]
AID - 10.1118/1.4953633 [doi]
PST - ppublish
SO  - Med Phys. 2016 Jul;43(7):4150. doi: 10.1118/1.4953633.