title: Comparison of contrast-to-noise ratios of transmission and dark-field signal in grating-based X-ray imaging for healthy murine lung tissue.
abstract: OBJECTIVE
  An experimental comparison of the contrast-to-noise ratio (CNR) between transmission and dark-field signals in grating-based X-ray imaging for ex-vivo murine lung tissue.
  
  
  METHODS
  Lungs from three healthy mice were imaged ex vivo using a laser-driven compact synchrotron X-ray source. Background noise of transmission and dark-field signal was quantified by measuring the standard deviation in a region of interest (ROI) placed in a homogeneous area outside the specimen. Image contrast was quantified by measuring the signal range in rectangular ROIs placed in central and peripheral lung parenchyma. The relative contrast gain (RCG) of dark-field over transmission images was calculated as CNRDF / CNRT.
  
  
  RESULTS
  In all images, there was a trend for contrast-to-noise ratios of dark-field images (CNRDF) to be higher than for transmission images (CNRT) for all ROIs (median 61 vs. 38, p=0.10), but the difference was statistically significant only for peripheral ROIs (61 vs. 32, p=0.03). Median RCG was >1 for all ROIs (1.84). RCG values were significantly smaller for central ROIs than for peripheral ROIs (1.34 vs. 2.43, p=0.03).
  
  
  CONCLUSIONS
  The contrast-to-noise ratio of dark-field images compares more favorably to the contrast-to-noise ratio of transmission images for peripheral lung regions as compared to central regions. For any specific specimen, a calculation of the RCG allows comparing which X-ray modality (dark-field or transmission imaging) produces better contrast-to-noise characteristics in a well-defined ROI.
authors.affiliation: Institute for Clinical Radiology, Ludwig Maximilians-University Hospital Munich, Marchioninistr. 15, 81377 München, Germany. felix.schwab@med.uni-muenchen.de
authors.forename: Felix
authors.initials: F
authors.lastname: Schwab
authors.forename: Simone
authors.initials: S
authors.lastname: Schleede
authors.forename: Dieter
authors.initials: D
authors.lastname: Hahn
authors.forename: Martin
authors.initials: M
authors.lastname: Bech
authors.forename: Julia
authors.initials: J
authors.lastname: Herzen
authors.forename: Sigrid
authors.initials: S
authors.lastname: Auweter
authors.forename: Fabian
authors.initials: F
authors.lastname: Bamberg
authors.forename: Klaus
authors.initials: K
authors.lastname: Achterhold
authors.forename: Ali Ö
authors.initials: AÖ
authors.lastname: Yildirim
authors.forename: Alexander
authors.initials: A
authors.lastname: Bohla
authors.forename: Oliver
authors.initials: O
authors.lastname: Eickelberg
authors.forename: Rod
authors.initials: R
authors.lastname: Loewen
authors.forename: Martin
authors.initials: M
authors.lastname: Gifford
authors.forename: Ronald
authors.initials: R
authors.lastname: Ruth
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.forename: Konstantin
authors.initials: K
authors.lastname: Nikolaou
authors.forename: Franz
authors.initials: F
authors.lastname: Pfeiffer
authors.forename: Felix G
authors.initials: FG
authors.lastname: Meinel
mesh_terms: D000818:Animals; D002102:Cadaver; D005260:Female; D006801:Humans; D008029:Lighting / Q000379:methods*; D008168:Lung / Q000000981:diagnostic imaging*; D051379:Mice; D008810:Mice, Inbred C57BL; D012016:Reference Values; D012031:Refractometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017356:Synchrotrons; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*; D014961:X-Ray Diffraction / Q000295:instrumentation*