title: Nanoscale measurements of proton tracks using fluorescent nuclear track detectors.
abstract: OBJECTIVE
  The authors describe a method in which fluorescence nuclear track detectors (FNTDs), novel track detectors with nanoscale spatial resolution, are used to determine the linear energy transfer (LET) of individual proton tracks from proton therapy beams by allowing visualization and 3D reconstruction of such tracks.
  
  
  METHODS
  FNTDs were exposed to proton therapy beams with nominal energies ranging from 100 to 250 MeV. Proton track images were then recorded by confocal microscopy of the FNTDs. Proton tracks in the FNTD images were fit by using a Gaussian function to extract fluorescence amplitudes. Histograms of fluorescence amplitudes were then compared with LET spectra.
  
  
  RESULTS
  The authors successfully used FNTDs to register individual proton tracks from high-energy proton therapy beams, allowing reconstruction of 3D images of proton tracks along with delta rays. The track amplitudes from FNTDs could be used to parameterize LET spectra, allowing the LET of individual proton tracks from therapeutic proton beams to be determined.
  
  
  CONCLUSIONS
  FNTDs can be used to directly visualize proton tracks and their delta rays at the nanoscale level. Because the track intensities in the FNTDs correlate with LET, they could be used further to measure LET of individual proton tracks. This method may be useful for measuring nanoscale radiation quantities and for measuring the LET of individual proton tracks in radiation biology experiments.
authors.affiliation: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Graduate School of Biomedical Sciences, The University of Texas, Houston, Texas 77030.
authors.forename: Gabriel O
authors.initials: GO
authors.lastname: Sawakuchi
authors.affiliation: Department of Nuclear Physics, University of Sao Paulo, SP 05508-090, Brazil.
authors.forename: Felisberto A
authors.initials: FA
authors.lastname: Ferreira
authors.affiliation: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030.
authors.forename: Conor H
authors.initials: CH
authors.lastname: McFadden
authors.affiliation: Biophysics Program, Harvard University, Cambridge, Massachusetts 02138.
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Hallacy
authors.affiliation: Department of Medical Physics, The Ottawa Hospital Cancer Centre, Ottawa, Ontario K1H 8L6, Canada.
authors.forename: Dal A
authors.initials: DA
authors.lastname: Granville
authors.affiliation: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Graduate School of Biomedical Sciences, The University of Texas, Houston, Texas 77030.
authors.forename: Narayan
authors.initials: N
authors.lastname: Sahoo
authors.affiliation: Crystal Growth Division, Landauer, Inc., Stillwater, Oklahoma 74074.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Akselrod
mesh_terms: D003198:Computer Simulation; D004735:Energy Transfer; D005453:Fluorescence; D021621:Imaging, Three-Dimensional; D018613:Microscopy, Confocal / Q000295:instrumentation* / Q000379:methods*; D009010:Monte Carlo Method; D061766:Proton Therapy; D011522:Protons; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*
chemical_list: D011522:Protons