title: Quantitative analysis of emphysema in 3D using MDCT: influence of different reconstruction algorithms.
abstract: OBJECTIVE
  The aim of the study was to compare the influence of different reconstruction algorithms on quantitative emphysema analysis in patients with severe emphysema.
  
  
  METHODS
  Twenty-five patients suffering from severe emphysema were included in the study. All patients underwent inspiratory MDCT (Aquilion-16, slice thickness 1/0.8mm). The raw data were reconstructed using six different algorithms: bone kernel with beam hardening correction (BHC), soft tissue kernel with BHC; standard soft tissue kernel, smooth soft tissue kernel (internal reference standard), standard lung kernel, and high-convolution kernel. The only difference between image data sets was the algorithm employed to reconstruct the raw data, no additional radiation was required. CT data were analysed using self-written emphysema detection and quantification software providing lung volume, emphysema volume (EV), emphysema index (EI) and mean lung density (MLD).
  
  
  RESULTS
  The use of kernels with BHC led to a significant decrease in MLD (5%) and EI (61-79%) in comparison with kernels without BHC. The absolute difference (from smooth soft tissue kernel) in MLD ranged from -0.6 to -6.1 HU and were significant different for all kernels. The EV showed absolute differences between -0.05 and -0.4 L and was significantly different for all kernels. The EI showed absolute differences between -0.8 and -5.1 and was significantly different for all kernels.
  
  
  CONCLUSIONS
  The use of kernels with BHC led to a significant decrease in MLD and EI. The absolute differences between different kernels without BHC were small but they were larger than the known interscan variation in patients. Thus, for follow-up examinations the same reconstruction algorithm has to be used and use of BHC has to be avoided.
authors.affiliation: Department of Radiology, Johannes Gutenberg University Hospital, Langenbeckstr. 1, 55131 Mainz, Germany. juliazapo@web.de
authors.forename: Julia
authors.initials: J
authors.lastname: Ley-Zaporozhan
authors.forename: Sebastian
authors.initials: S
authors.lastname: Ley
authors.forename: Oliver
authors.initials: O
authors.lastname: Weinheimer
authors.forename: Svitlana
authors.initials: S
authors.lastname: Iliyushenko
authors.forename: Serap
authors.initials: S
authors.lastname: Erdugan
authors.forename: Ralf
authors.initials: R
authors.lastname: Eberhardt
authors.forename: Adelheid
authors.initials: A
authors.lastname: Fuxa
authors.forename: Jürgen
authors.initials: J
authors.lastname: Mews
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Kauczor
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging*; D011857:Radiographic Image Interpretation, Computer-Assisted; D012129:Respiratory Function Tests; D012984:Software; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*