title: Radiation dose and image quality in K-edge subtraction computed tomography of lung in vivo.
abstract: K-edge subtraction computed tomography (KES-CT) allows simultaneous imaging of both structural features and regional distribution of contrast elements inside an organ. Using this technique, regional lung ventilation and blood volume distributions can be measured experimentally in vivo. In order for this imaging technology to be applicable in humans, it is crucial to minimize exposure to ionizing radiation with little compromise in image quality. The goal of this study was to assess the changes in signal-to-noise ratio (SNR) of KES-CT lung images as a function of radiation dose. The experiments were performed in anesthetized and ventilated rabbits using inhaled xenon gas in O2 at two concentrations: 20% and 70%. Radiation dose, defined as air kerma (Ka), was measured free-in-air and in a 16 cm polymethyl methacrylate phantom with a cylindrical ionization chamber. The dose free-in-air was varied from 2.7 mGy to 8.0 Gy. SNR in the images of xenon in air spaces was above the Rose criterion (SNR > 5) when Ka was over 400 mGy with 20% xenon, and over 40 mGy with 70% xenon. Although in human thorax attenuation is higher, based on these findings it is estimated that, by optimizing the imaging sequence and reconstruction algorithms, the radiation dose could be further reduced to clinically acceptable levels.
authors.affiliation: Department of Physics, University of Helsinki, Helsinki 00370, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Strengell
authors.affiliation: Department of Oncology, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Keyriläinen
authors.affiliation: Department of Physics, University of Helsinki, Helsinki 00370, Finland.
authors.forename: P
authors.initials: P
authors.lastname: Suortti
authors.affiliation: Université de Picardie Jules Verne, Inserm U1105 and CHU Amiens, France.
authors.forename: S
authors.initials: S
authors.lastname: Bayat
authors.affiliation: Department of Clinical Physiology and Nuclear Medicine, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: A R A
authors.initials: AR
authors.lastname: Sovijärvi
authors.affiliation: Department of Physics, University of Helsinki, Helsinki 00370, Finland.
authors.forename: L
authors.initials: L
authors.lastname: Porra
mesh_terms: D000818:Animals; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008168:Lung / Q000528:radiation effects*; D011786:Quality Control; D011817:Rabbits; D011829:Radiation Dosage; D013382:Subtraction Technique; D017356:Synchrotrons; D046509:Tissue Culture Techniques; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: K-edge subtraction; computed tomography; dosimetry; image quality; lung imaging