title: Systematic Comparison of Reduced Tube Current Protocols for High-pitch and Standard-pitch Pulmonary CT Angiography in a Large Single-center Population.
abstract: OBJECTIVE
  Benefits of iterative reconstruction (IR) algorithms combined with dose-reduction techniques have been shown at computed tomography pulmonary angiography (CTPA) in several medium to small patient collectives. In this study, we performed a systematic comparison of image quality to combinations of reduced tube current (RC) and IR for both standard-pitch (SP) single-source and high-pitch (HP) dual-source CTPA in a large, single-center population.
  
  
  METHODS
  Three hundred eighty-two consecutive patients (October 2010 through December 2012) received clinically indicated CTPA with one of four consecutively changed protocols: (1) HPSC: 180 mAs, weighted filtered back projection, pitch = 3; (2) HPRC: 90 mAs, IR, pitch = 3; (3) SPSC: 180 mAs, weighted filtered back projection, pitch = 1.2; and (4) HPRC: 90 mAs, IR, pitch = 1.2. Tube potential was 100 kV. Vascular attenuation and standardized signal-to-noise ratio (sSNR) were measured in the pulmonary trunk (sSNRPT) and on segmental artery level (sSNRS1, sSNRS10). Dose-length-product was recorded per series. Two independent investigators rated image quality. Kolmogorov-Smirnov test, Kruskal-Wallis test, and kappa statistics were used for statistical analysis. Median values are presented per group.
  
  
  RESULTS
  Image quality was consistent between all groups (observer 1: P = 0.118; observer 2: P = 0.122). Inter-reader consistency was very good (κ = 0.866, P < 0.001). Dose-length-product was significantly reduced in HP and RC groups (P < 0.001 for each; SPSC: 139.5 mGycm; HPRC: 92 mGycm; SPSC: 211 mGycm; HPRC: 137 mGycm). sSNR was comparable (sSNRPT overall: P = 0.052; sSNRS1 overall: P = 0.161; and sSNRS10 overall: P = 0.259).
  
  
  CONCLUSIONS
  Substantial dose reduction can be within a routine clinical setting without quantifiable loss of image quality either by HP pulmonary angiography or by a combination of IR and RC in either HP or SP acquisition.
authors.affiliation: Institute for Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, House 23c, 60590 Frankfurt, Germany. Electronic address: Doktorb@gmx.ch.
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Bucher
authors.affiliation: Institute for Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, House 23c, 60590 Frankfurt, Germany.
authors.forename: Matthias J
authors.initials: MJ
authors.lastname: Kerl
authors.affiliation: Institute for Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, House 23c, 60590 Frankfurt, Germany.
authors.forename: Moritz H
authors.initials: MH
authors.lastname: Albrecht
authors.affiliation: Institute for Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, House 23c, 60590 Frankfurt, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Beeres
authors.affiliation: Institute for Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, House 23c, 60590 Frankfurt, Germany.
authors.forename: Hanns
authors.initials: H
authors.lastname: Ackermann
authors.affiliation: Institute for Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, House 23c, 60590 Frankfurt, Germany.
authors.forename: Julian L
authors.initials: JL
authors.lastname: Wichmann
authors.affiliation: Institute for Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, House 23c, 60590 Frankfurt, Germany.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Vogl
authors.affiliation: Institute for Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, House 23c, 60590 Frankfurt, Germany.
authors.forename: Ralf W
authors.initials: RW
authors.lastname: Bauer
authors.affiliation: Institute for Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, House 23c, 60590 Frankfurt, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Lehnert
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D016477:Artifacts; D000072226:Computed Tomography Angiography / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000592:standards; D007275:Injections, Intravenous; D007479:Iopamidol / Q000008:administration & dosage / Q000031:analogs & derivatives; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods / Q000592:standards; D012189:Retrospective Studies; D059629:Signal-To-Noise Ratio; D013997:Time Factors; D055815:Young Adult
chemical_list: D003287:Contrast Media; C057937:iomeprol; D007479:Iopamidol
keywords: Pulmonary CT angiography; high-pitch CT acquisition; reduced tube current protocol