title: Accurate tissue characterization in low-dose CT imaging with pure iterative reconstruction.
abstract: BACKGROUND
  We assess the ability of low-dose hybrid iterative reconstruction (IR) and 'pure' model-based IR (MBIR) images to maintain accurate Hounsfield unit (HU)-determined tissue characterization.
  
  
  METHODS
  Standard-protocol (SP) and low-dose modified-protocol (MP) CTs were contemporaneously acquired in 34 Crohn's disease patients referred for CT. SP image reconstruction was via the manufacturer's recommendations (60% FBP, filtered back projection; 40% ASiR, Adaptive Statistical iterative Reconstruction; SP-ASiR40). MP data sets underwent four reconstructions (100% FBP; 40% ASiR; 70% ASiR; MBIR). Three observers measured tissue volumes using HU thresholds for fat, soft tissue and bone/contrast on each data set. Analysis was via SPSS.
  
  
  RESULTS
  Inter-observer agreement was strong for 1530 datapoints (rs > 0.9). MP-MBIR tissue volume measurement was superior to other MP reconstructions and closely correlated with the reference SP-ASiR40 images for all tissue types. MP-MBIR superiority was most marked for fat volume calculation - close SP-ASiR40 and MP-MBIR Bland-Altman plot correlation was seen with the lowest average difference (336 cm3) when compared with other MP reconstructions.
  
  
  CONCLUSIONS
  Hounsfield unit-determined tissue volume calculations from MP-MBIR images resulted in values comparable to SP-ASiR40 calculations and values that are superior to MP-ASiR images. Accuracy of estimation of volume of tissues (e.g. fat) using segmentation software on low-dose CT images appears optimal when reconstructed with pure IR.
authors.affiliation: Department of Radiology, University College Cork, Cork, Ireland.
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Murphy
authors.affiliation: Department of Radiology, University College Cork, Cork, Ireland.
authors.forename: Patrick D
authors.initials: PD
authors.lastname: McLaughlin
authors.affiliation: Department of Radiology, University College Cork, Cork, Ireland.
authors.forename: Maria
authors.initials: M
authors.lastname: Twomey
authors.affiliation: Department of Radiology, University College Cork, Cork, Ireland.
authors.forename: Vincent E
authors.initials: VE
authors.lastname: Chan
authors.affiliation: Department of Radiology, University College Cork, Cork, Ireland.
authors.forename: Fiachra
authors.initials: F
authors.lastname: Moloney
authors.affiliation: Department of Radiology, University College Cork, Cork, Ireland.
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Fung
authors.affiliation: Department of Radiology, University College Cork, Cork, Ireland.
authors.forename: Faimee E
authors.initials: FE
authors.lastname: Chan
authors.affiliation: Department of Radiology, University College Cork, Cork, Ireland.
authors.forename: Tafline
authors.initials: T
authors.lastname: Kao
authors.affiliation: Department of Radiology, University College Cork, Cork, Ireland.
authors.forename: Siobhan B
authors.initials: SB
authors.lastname: O'Neill
authors.affiliation: Department of Radiology, University College Cork, Cork, Ireland.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Watson
authors.affiliation: Department of Radiology, University College Cork, Cork, Ireland.
authors.forename: Owen J
authors.initials: OJ
authors.lastname: O'Connor
authors.affiliation: Department of Radiology, University College Cork, Cork, Ireland.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Maher
mesh_terms: D000328:Adult; D000465:Algorithms; D015519:Bone Density; D003287:Contrast Media; D003424:Crohn Disease / Q000000981:diagnostic imaging*; D003974:Diatrizoate Meglumine; D005260:Female; D006801:Humans; D007472:Iohexol; D008297:Male; D011446:Prospective Studies; D000069079:Radiation Exposure; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D003974:Diatrizoate Meglumine; D007472:Iohexol
keywords: Hounsfield units; computed tomography; image reconstruction; iterative reconstruction; radiation