title: An iterative deconvolution algorithm for image recovery in clinical CT: A phantom study.
abstract: OBJECTIVE
  To study the feasibility of using an iterative reconstruction algorithm to improve previously reconstructed CT images which are judged to be non-diagnostic on clinical review. A novel rapidly converging, iterative algorithm (RSEMD) to reduce noise as compared with standard filtered back-projection algorithm has been developed.
  
  
  METHODS
  The RSEMD method was tested on in-silico, Catphan(®)500, and anthropomorphic 4D XCAT phantoms. The method was applied to noisy CT images previously reconstructed with FBP to determine improvements in SNR and CNR. To test the potential improvement in clinically relevant CT images, 4D XCAT phantom images were used to simulate a small, low contrast lesion placed in the liver.
  
  
  RESULTS
  In all of the phantom studies the images proved to have higher resolution and lower noise as compared with images reconstructed by conventional FBP. In general, the values of SNR and CNR reached a plateau at around 20 iterations with an improvement factor of about 1.5 for in noisy CT images. Improvements in lesion conspicuity after the application of RSEMD have also been demonstrated. The results obtained with the RSEMD method are in agreement with other iterative algorithms employed either in image space or with hybrid reconstruction algorithms.
  
  
  CONCLUSIONS
  In this proof of concept work, a rapidly converging, iterative deconvolution algorithm with a novel resolution subsets-based approach that operates on DICOM CT images has been demonstrated. The RSEMD method can be applied to sub-optimal routine-dose clinical CT images to improve image quality to potentially diagnostically acceptable levels.
authors.affiliation: Translational Research, Department of Radiology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390-9061, USA. Electronic address: Nikolai.Slavine@UTSouthwestern.edu.
authors.forename: Nikolai V
authors.initials: NV
authors.lastname: Slavine
authors.affiliation: Clinical Medical Physics, Department of Radiology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9061, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Guild
authors.affiliation: Clinical Medical Physics, Department of Radiology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9061, USA.
authors.forename: Roderick W
authors.initials: RW
authors.lastname: McColl
authors.affiliation: Clinical Medical Physics, Department of Radiology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9061, USA.
authors.forename: Jon A
authors.initials: JA
authors.lastname: Anderson
authors.affiliation: Nuclear Medicine, Department of Radiology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9061, USA.
authors.forename: Orhan K
authors.initials: OK
authors.lastname: Oz
authors.affiliation: Translational Research, Department of Radiology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390-9061, USA.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Lenkinski
mesh_terms: D000465:Algorithms; D056973:Four-Dimensional Computed Tomography / Q000295:instrumentation*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D019047:Phantoms, Imaging; D059629:Signal-To-Noise Ratio
keywords: CNR and SNR improvement; Noisy CT image recovery; Rapid converging; Resolution subsets-based iterative method