title: Gemstone spectral imaging: determination of CT to ED conversion curves for radiotherapy treatment planning.
abstract: The monochromatic images acquired by Gemstone spectral imaging (GSI) mode on the GE CT750 HD theoretically determines the computed tomography (CT) number more accurately than that of conventional scanner. Using the former, the CT number is calculated from (synthesized) monoenergetic X-ray data. We reasoned that the monochromatic image might be applied to radiotherapy treatment planning (RTP) to calculate dose distribution more accurately. Our goal here was to provide CT to electron density (ED) conversion curves with monochromatic images for RTP. Therefore, we assessed the reproducibility of CT numbers, an important factor on quality assurance, over short and long time periods for different substances at varying energy. CT number difference between measured and theoretical value was investigated. The scanner provided sufficient reproducibility of CT numbers for dose calculation over short and long time periods. The CT numbers of monochromatic images produced by this scanner had reasonable values for dose calculation. The CT to ED conversion curve becomes linear with respect to the relationship between CT numbers and EDs as the energy increases. We conclude that monochromatic imaging from a fast switching system can be applied for the dose calculation, keeping Hounsfield units (HU) stability.
authors.affiliation: Osaka University Graduate School of Medicine. m.yagi@radonc.med.osaka-u.ac.jp.
authors.forename: Masashi
authors.initials: M
authors.lastname: Yagi
authors.forename: Takashi
authors.initials: T
authors.lastname: Ueguchi
authors.forename: Masahiko
authors.initials: M
authors.lastname: Koizumi
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ogata
authors.forename: Sachiko
authors.initials: S
authors.lastname: Yamada
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Iori
authors.initials: I
authors.lastname: Sumida
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Akino
authors.forename: Koji
authors.initials: K
authors.lastname: Konishi
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Isohashi
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Tomiyama
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Yoshioka
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ogawa
mesh_terms: D000465:Algorithms; D004583:Electrons; D006801:Humans; D058958:Organs at Risk / Q000528:radiation effects; D019047:Phantoms, Imaging; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
references.citation: Radiology. 2011 Apr;259(1):173-83
references.pmid: 21292866
references.citation: Med Phys. 1988 Sep-Oct;15(5):726-31
references.pmid: 3185409
references.citation: Neuroradiology. 1976;11(1):15-21
references.pmid: 934468
references.citation: J Comput Assist Tomogr. 1987 Jan-Feb;11(1):144-50
references.pmid: 3805401
references.citation: Med Phys. 1986 May-Jun;13(3):340-3
references.pmid: 3724694
references.citation: Br J Radiol. 2002 Dec;75(900):937-49
references.pmid: 12515702
references.citation: J Comput Assist Tomogr. 1977 Oct;1(4):487-93
references.pmid: 615229
references.citation: Radiology. 2011 Jun;259(3):720-9
references.pmid: 21357524
references.citation: Med Phys. 1986 May-Jun;13(3):334-9
references.pmid: 3724693
references.citation: Phys Med Biol. 2011 Jul 21;56(14):4499-515
references.pmid: 21719949
references.citation: Int J Radiat Oncol Biol Phys. 2007 Mar 15;67(4):1201-10
references.pmid: 17336221
references.citation: Neuroradiology. 1976;11(1):23-8
references.pmid: 934469
references.citation: Med Phys. 2009 Apr;36(4):1359-69
references.pmid: 19472643
references.citation: Phys Med Biol. 1976 Sep;21(5):733-44
references.pmid: 967922
references.citation: Med Phys. 2009 Aug;36(8):3818-29
references.pmid: 19746815
references.citation: Med Phys. 1990 May-Jun;17(3):327-41
references.pmid: 2385190
references.citation: Med Phys. 1982 Jul-Aug;9(4):464-72
references.pmid: 7110075
references.citation: Med Phys. 2011 Apr;38(4):2222-32
references.pmid: 21626956
references.citation: Med Phys. 2011 Mar;38(3):1178-88
references.pmid: 21520830
references.citation: Med Phys. 1981 Sep-Oct;8(5):659-67
references.pmid: 7290019
references.citation: Med Phys. 2008 Mar;35(3):849-65
references.pmid: 18404922
references.citation: Br J Radiol. 1973 Dec;46(552):1016-22
references.pmid: 4757352
references.citation: Radiother Oncol. 2001 Aug;60(2):191-201
references.pmid: 11439214