title: Image quality improvement using an image-based noise reduction algorithm:  initial experience in a phantom model for urinary stones.
abstract: OBJECTIVE
  To determine signal-to-noise (SNR), contrast-to-noise ratio, and segmentation error measurements in various low-dose computed tomographic (CT) acquisitions of an anthropomorphic phantom containing urinary stones before and after implementation of a structure-preserving diffusion (SPD) denoising algorithm, and to compare the measurements with those of standard-dose CT acquisitions.
  
  
  METHODS
  After institutional review board approval, written informed consent was waived and 36 calcium oxalate stones were evaluated after CT acquisitions in an anthropomorphic phantom at variable tube currents (33-137 mA s). The SPD denoising algorithm was applied to all images. Signal-to-noise ratio, contrast-to-noise ratio, and expected segmentation error were determined using manually drawn regions of interest to quantify the effect of the noise reduction on the image quality.
  
  
  RESULTS
  The value of segmentation error measurements using the SPD denoising algorithm obtained at tube currents as low as 33 mA s (up to 75% dose reduction level) were similar to standard imaging at 137 mA s. The denoised images at reduced doses up to 75% dose reduction have higher SNR than the standard-dose images without denoising (P < 0.005). Stepwise regression showed significant (P < 0.001) effect of dose length product on SNR, and segmentation error measurements.
  
  
  CONCLUSIONS
  Based on objective noise-related image quality metrics, the SPD denoising algorithm may be useful as a robust and fast tool, and it has the potential to improve image quality in low-dose CT ureter protocols.
authors.affiliation: Applied Imaging Science Laboratory, Department of Radiology, Brigham and Women's Hospital, Boston, MA 02115, USA.
authors.forename: Shadpour
authors.initials: S
authors.lastname: Demehri
authors.forename: Pascal
authors.initials: P
authors.lastname: Salazar
authors.forename: Michael L
authors.initials: ML
authors.lastname: Steigner
authors.forename: Stefan
authors.initials: S
authors.lastname: Atev
authors.forename: Osama
authors.initials: O
authors.lastname: Masoud
authors.forename: Philippe
authors.initials: P
authors.lastname: Raffy
authors.forename: Scott A
authors.initials: SA
authors.lastname: Jacobs
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Rybicki
mesh_terms: D000465:Algorithms; D002129:Calcium Oxalate / Q000737:chemistry; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D016015:Logistic Models; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods*; D052878:Urolithiasis / Q000000981:diagnostic imaging
chemical_list: D002129:Calcium Oxalate