title: Characterization of the nanoDot OSLD dosimeter in CT.
abstract: OBJECTIVE
  The extensive use of computed tomography (CT) in diagnostic procedures is accompanied by a growing need for more accurate and patient-specific dosimetry techniques. Optically stimulated luminescent dosimeters (OSLDs) offer a potential solution for patient-specific CT point-based surface dosimetry by measuring air kerma. The purpose of this work was to characterize the OSLD nanoDot for CT dosimetry, quantifying necessary correction factors, and evaluating the uncertainty of these factors.
  
  
  METHODS
  A characterization of the Landauer OSL nanoDot (Landauer, Inc., Greenwood, IL) was conducted using both measurements and theoretical approaches in a CT environment. The effects of signal depletion, signal fading, dose linearity, and angular dependence were characterized through direct measurement for CT energies (80-140 kV) and delivered doses ranging from ∼5 to >1000 mGy. Energy dependence as a function of scan parameters was evaluated using two independent approaches: direct measurement and a theoretical approach based on Burlin cavity theory and Monte Carlo simulated spectra. This beam-quality dependence was evaluated for a range of CT scanning parameters.
  
  
  RESULTS
  Correction factors for the dosimeter response in terms of signal fading, dose linearity, and angular dependence were found to be small for most measurement conditions (<3%). The relative uncertainty was determined for each factor and reported at the two-sigma level. Differences in irradiation geometry (rotational versus static) resulted in a difference in dosimeter signal of 3% on average. Beam quality varied with scan parameters and necessitated the largest correction factor, ranging from 0.80 to 1.15 relative to a calibration performed in air using a 120 kV beam. Good agreement was found between the theoretical and measurement approaches.
  
  
  CONCLUSIONS
  Correction factors for the measurement of air kerma were generally small for CT dosimetry, although angular effects, and particularly effects due to changes in beam quality, could be more substantial. In particular, it would likely be necessary to account for variations in CT scan parameters and measurement location when performing CT dosimetry using OSLD.
authors.affiliation: The University of Texas MD Anderson Cancer Center, Houston, Texas 77030; Graduate School of Biomedical Sciences, The University of Texas Health Science Center Houston, Houston, Texas 77030; and The Methodist Hospital, Houston, Texas 77030.
authors.forename: Sarah B
authors.initials: SB
authors.lastname: Scarboro
authors.affiliation: The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Graduate School of Biomedical Sciences, The University of Texas Health Science Center Houston, Houston, Texas 77030.
authors.forename: Dianna
authors.initials: D
authors.lastname: Cody
authors.affiliation: The University of Texas MD Anderson Cancer Center, Houston, Texas 77030.
authors.forename: Paola
authors.initials: P
authors.lastname: Alvarez
authors.affiliation: The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Graduate School of Biomedical Sciences, The University of Texas Health Science Center Houston, Houston, Texas 77030.
authors.forename: David
authors.initials: D
authors.lastname: Followill
authors.affiliation: The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Graduate School of Biomedical Sciences, The University of Texas Health Science Center Houston, Houston, Texas 77030.
authors.forename: Laurence
authors.initials: L
authors.lastname: Court
authors.affiliation: The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Graduate School of Biomedical Sciences, The University of Texas Health Science Center Houston, Houston, Texas 77030.
authors.forename: Francesco C
authors.initials: FC
authors.lastname: Stingo
authors.affiliation: Biomedical Physics Graduate Program, David Geffen School of Medicine at UCLA, Los Angeles, California 90095 and Toshiba American Medical Systems, Tustin, California 92780.
authors.forename: Di
authors.initials: D
authors.lastname: Zhang
authors.affiliation: The Department of Radiological Sciences, David Geffen School of Medicine at UCLA, Los Angeles, California 90095.
authors.forename: Michael
authors.initials: M
authors.lastname: McNitt-Gray
authors.affiliation: The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Graduate School of Biomedical Sciences, The University of Texas Health Science Center Houston, Houston, Texas 77030.
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Kry
mesh_terms: D002138:Calibration; D003198:Computer Simulation; D016014:Linear Models; D009010:Monte Carlo Method; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods; D017711:Nonlinear Dynamics; D062791:Optically Stimulated Luminescence Dosimetry / Q000295:instrumentation* / Q000379:methods; D011829:Radiation Dosage; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods; D035501:Uncertainty
references.citation: Phys Med Biol. 2008 Oct 21;53(20):R351-79
references.pmid: 18799833
references.citation: Med Phys. 2008 Apr;35(4):1261-6
references.pmid: 18491518
references.citation: Med Phys. 2009 Jun;36(6):2154-64
references.pmid: 19610304
references.citation: JAMA. 2010 Jul 14;304(2):208-9
references.pmid: 20628137
references.citation: Health Phys. 2011 Sep;101(3):299-310
references.pmid: 21799346
references.citation: Med Phys. 2011 Jul;38(7):3955-62
references.pmid: 21858992
references.citation: Med Phys. 2011 Jul;38(7):4396-405
references.pmid: 21859040
references.citation: Phys Med Biol. 2011 Sep 21;56(18):6065-82
references.pmid: 21873767
references.citation: Phys Med Biol. 2012 May 7;57(9):2505-15
references.pmid: 22493180
references.citation: Lancet. 2012 Aug 4;380(9840):499-505
references.pmid: 22681860
references.citation: Med Phys. 2012 Nov;39(11):6580-4
references.pmid: 23127052
references.citation: Radiat Prot Dosimetry. 2013 Jan;153(1):23-31
references.pmid: 22653437
references.citation: Med Phys. 2013 Jun;40(6):062102
references.pmid: 23718600
references.citation: Med Phys. 2013 Aug;40(8):081917
references.pmid: 23927331
references.citation: Phys Med Biol. 2013 Sep 7;58(17):5885-97
references.pmid: 23920245
references.citation: Med Phys. 1992 Nov-Dec;19(6):1427-33
references.pmid: 1461205
references.citation: Health Phys. 2003 Jul;85(1):47-59
references.pmid: 12852471
references.citation: Med Phys. 2013 Nov;40(11):112102
references.pmid: 24320455
references.citation: Phys Med Biol. 1997 Jul;42(7):1335-49
references.pmid: 9253043
references.citation: Br J Radiol. 2005 Apr;78(928):328-34
references.pmid: 15774593
references.citation: Phys Med Biol. 2005 Dec 7;50(23):5619-28
references.pmid: 16306656
references.citation: Radiat Prot Dosimetry. 2006;118(1):28-31
references.pmid: 16046555
references.citation: N Engl J Med. 2007 Nov 29;357(22):2277-84
references.pmid: 18046031
references.citation: Med Phys. 2007 Dec;34(12):4594-604
references.pmid: 18196786
references.citation: Br J Radiol. 2008 May;81(965):362-78
references.pmid: 18440940
references.citation: Med Phys. 2009 May;36(5):1690-9
references.pmid: 19544786