PMID- 35103331
OWN - NLM
STAT- MEDLINE
DCOM- 20220413
LR  - 20230531
IS  - 2473-4209 (Electronic)
IS  - 0094-2405 (Print)
IS  - 0094-2405 (Linking)
VI  - 49
IP  - 4
DP  - 2022 Apr
TI  - A reconstruction approach for proton computed tomography by modeling the integral 
      depth dose of the scanning proton pencil beam.
PG  - 2602-2620
LID - 10.1002/mp.15482 [doi]
AB  - PURPOSE: To present a proton computed tomography (pCT) reconstruction approach 
      that models the integral depth dose (IDD) of the clinical scanning proton beam 
      into beamlets. Using a multilayer ionization chamber (MLIC) as the imager, the 
      proposed pCT system and the reconstruction approach can minimize extra ambient 
      neutron dose and simplify the beamline design by eliminating an additional 
      collimator to confine the proton beam. METHODS: Monte Carlo simulation was 
      applied to digitally simulate the IDDs of the exiting proton beams detected by 
      the MLIC. A forward model was developed to model each IDD into a weighted sum of 
      percentage depth doses of the constituent beamlets separated laterally by 1 mm. 
      The water equivalent path lengths (WEPLs) of the beamlets were determined by 
      iteratively minimizing the squared L2-norm between the forward projected and 
      simulated IDDs. The final WEPL values were reconstructed to pCT images, that is, 
      proton stopping power ratio (SPR) maps, through simultaneous algebraic 
      reconstruction technique with total variation regularization. The reconstruction 
      process was tested with a digital cylindrical water-based phantom and an ICRP 
      adult reference computational phantom. The mean of SPR within regions of interest 
      (ROIs) and the WEPL along a 4 mm-wide beam ( WEPL4mm ) were compared with the 
      reference values. The spatial resolution was analyzed at the edge of a cortical 
      insert of the cylindrical phantom. RESULTS: The percentage deviations from 
      reference SPR were within +/-1% in all selected ROIs. The mean absolute error of 
      the reconstructed SPR was 0.33%, 0.19%, and 0.27% for the cylindrical phantom, 
      the adult phantom at the head and lung region, respectively. The corresponding 
      percentage deviations from reference WEPL4mm were 0.48 +/- 0.64%, 0.28 +/- 0.48%, and 
      0.22 +/- 0.49%. The full width at half maximum of the line spread function (LSF) 
      derived from the radial edge spread function (ESF) of a cortical insert was 
      0.13 cm. The frequency at 10% of the modulation transfer function (MTF) was 
      6.38 cm(-1) . The mean signal-to-noise ratio (SNR) of all the inserts was 2.45. 
      The mean imaging dose was 0.29 and 0.25 cGy at the head and lung region of the 
      adult phantom, respectively. CONCLUSION: A new pCT reconstruction approach was 
      developed by modeling the IDDs of the uncollimated scanning proton beams in the 
      pencil beam geometry. SPR accuracy within +/-1%, spatial resolution of better than 
      2 mm at 10% MTF, and imaging dose at the magnitude of mGy were achieved. 
      Potential side effects caused by neutron dose were eliminated by removing the 
      extra beam collimator.
CI  - (c) 2022 American Association of Physicists in Medicine.
FAU - Chen, Xinyuan
AU  - Chen X
AD  - Department of Biomedical Engineering, Washington University in St. Louis, St. 
      Louis, Missouri, USA.
FAU - Medrano, Maria
AU  - Medrano M
AD  - Department of Electrical and Systems Engineering, Washington University in St. 
      Louis, St. Louis, Missouri, USA.
FAU - Sun, Baozhou
AU  - Sun B
AD  - Department of Radiation Oncology, Washington University School of Medicine in St. 
      Louis, St. Louis, Missouri, USA.
FAU - Hao, Yao
AU  - Hao Y
AD  - Department of Radiation Oncology, Washington University School of Medicine in St. 
      Louis, St. Louis, Missouri, USA.
FAU - Reynoso, Francisco J
AU  - Reynoso FJ
AD  - Department of Radiation Oncology, Washington University School of Medicine in St. 
      Louis, St. Louis, Missouri, USA.
FAU - Darafsheh, Arash
AU  - Darafsheh A
AD  - Department of Radiation Oncology, Washington University School of Medicine in St. 
      Louis, St. Louis, Missouri, USA.
FAU - Yang, Deshan
AU  - Yang D
AD  - Department of Radiation Oncology, Washington University School of Medicine in St. 
      Louis, St. Louis, Missouri, USA.
FAU - Zhang, Tiezhi
AU  - Zhang T
AD  - Department of Radiation Oncology, Washington University School of Medicine in St. 
      Louis, St. Louis, Missouri, USA.
FAU - Zhao, Tianyu
AU  - Zhao T
AD  - Department of Radiation Oncology, Washington University School of Medicine in St. 
      Louis, St. Louis, Missouri, USA.
LA  - eng
GR  - R01 EB029431/EB/NIBIB NIH HHS/United States
GR  - R01 HL148210/HL/NHLBI NIH HHS/United States
GR  - R01 CA212638/CA/NCI NIH HHS/United States
GR  - T32 EB014855/NH/NIH HHS/United States
GR  - R01 CA212638/NH/NIH HHS/United States
GR  - T32 EB014855/EB/NIBIB NIH HHS/United States
PT  - Journal Article
DEP - 20220214
PL  - United States
TA  - Med Phys
JT  - Medical physics
JID - 0425746
RN  - 0 (Protons)
RN  - 059QF0KO0R (Water)
SB  - IM
MH  - Monte Carlo Method
MH  - Phantoms, Imaging
MH  - *Proton Therapy
MH  - *Protons
MH  - Tomography, X-Ray Computed/methods
MH  - Water
PMC - PMC9248291
MID - NIHMS1819800
OTO - NOTNLM
OT  - Monte Carlo simulation
OT  - model-based reconstruction
OT  - proton computed tomography
OT  - stopping power ratio
COIS- CONFLICT OF INTEREST The authors have no conflict of interest to report.
EDAT- 2022/02/02 06:00
MHDA- 2022/04/14 06:00
PMCR- 2022/07/01
CRDT- 2022/02/01 08:45
PHST- 2021/12/28 00:00 [revised]
PHST- 2021/05/03 00:00 [received]
PHST- 2021/12/29 00:00 [accepted]
PHST- 2022/02/02 06:00 [pubmed]
PHST- 2022/04/14 06:00 [medline]
PHST- 2022/02/01 08:45 [entrez]
PHST- 2022/07/01 00:00 [pmc-release]
AID - 10.1002/mp.15482 [doi]
PST - ppublish
SO  - Med Phys. 2022 Apr;49(4):2602-2620. doi: 10.1002/mp.15482. Epub 2022 Feb 14.