title: Attenuation correction using asymmetric fanbeam transmission CT on two-head SPECT system.
abstract: For transmission computed tomography (TCT) systems using a centered transmission source with a fan-beam collimator, the transmission projection data are truncated. To achieve sufficiently large imaging field of view (FOV), we have designed the combination of an asymmetric fan-beam (AsF) collimator and a small uncollimated sheet-source for TCT, and implemented AsF sampling on a two-head SPECT system. The purpose of this study is to evaluate the feasibility of our TCT method for quantitative emission computed tomography (ECT) in clinical application. Sequential Tc-99m transmission and Tl-201 emission data acquisition were performed in a cardiac phantom (30 cm in width) with a myocardial chamber and a patient study. Tc-99m of 185 MBq was used as the transmission source. Both the ECT and TCT images were reconstructed with the filtered back-projection method after scatter correction with the triple energy window (TEW) method. The attenuation corrected transaxial images were iteratively reconstructed with the Chang algorithm utilizing the attenuation coefficient map computed from the TCT data. In this AsF sampling geometry, an imaging FOV of 50 cm was yielded. The attenuated regions appeared normal on the scatter and attenuation corrected (SAC) images in the phantom and patient study. The good quantitative accuracy on the SAC images was also confirmed by the measurement of the Tl-201 radioactivity in the myocardial chamber in the phantom study. The AsF collimation geometry that we have proposed in this study makes it easy to realize TCT data acquisition on the two-head SPECT system and to perform quantification on Tl-201 myocardial SPECT.
authors.affiliation: Institute of Resource Development and Analysis, Kumamoto University, Japan. akojima@kaiju.medic.kumamoto-u.ac.jp
authors.forename: Akihiro
authors.initials: A
authors.lastname: Kojima
authors.forename: Seiji
authors.initials: S
authors.lastname: Tomiguchi
authors.forename: Koichi
authors.initials: K
authors.lastname: Kawanaka
authors.forename: Daisuke
authors.initials: D
authors.lastname: Utsunomiya
authors.forename: Shinya
authors.initials: S
authors.lastname: Shiraishi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakaura
authors.forename: Noboru
authors.initials: N
authors.lastname: Katsuda
authors.forename: Masanori
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Nobutoku
authors.initials: N
authors.lastname: Motomura
authors.forename: Takashi
authors.initials: T
authors.lastname: Ichihara
mesh_terms: D000368:Aged; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005240:Feasibility Studies; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation* / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods