title: High-Performance Soft-Tissue Imaging in Extremity Cone-Beam CT.
abstract: OBJECTIVE
  Clinical performance studies of an extremity cone-beam CT (CBCT) system indicate excellent bone visualization, but point to the need for improvement of soft-tissue image quality. To this end, a rapid Monte Carlo (MC) scatter correction is proposed, and Penalized Likelihood (PL) reconstruction is evaluated for noise management.
  
  
  METHODS
  The accelerated MC scatter correction involved fast MC simulation with low number of photons implemented on a GPU (107photons/sec), followed by Gaussian kernel smoothing in the detector plane and across projection angles. PL reconstructions were investigated for reduction of imaging dose for projections acquired at ~2 mGy.
  
  
  RESULTS
  The rapid scatter estimation yielded root-mean-squared-errors of scatter projections of ~15% of peak scatter intensity for 5·106photons/projection (runtime ~0.5 sec/projection) and 25% improvement in fat-muscle contrast in reconstructions of a cadaveric knee. PL reconstruction largely restored soft-tissue visualization at 2 mGy dose to that of 10 mGy FBP image.
  
  
  CONCLUSIONS
  The combination of rapid (5-10 minutes/scan) MC-based, patient-specific scatter correction and PL reconstruction offers an important means to overcome the current limitations of extremity CBCT in soft-tissue imaging.
authors: Dept. of Biomedical Engineering, Johns Hopkins University, Baltimore, MD USA 21205.
authors: W
authors: W
authors: Zbijewski
authors: Dept. of Biomedical Engineering, Johns Hopkins University, Baltimore, MD USA 21205.
authors: A
authors: A
authors: Sisniega
authors: Dept. of Biomedical Engineering, Johns Hopkins University, Baltimore, MD USA 21205.
authors: J W
authors: JW
authors: Stayman
authors: Dept. of Biomedical Engineering, Johns Hopkins University, Baltimore, MD USA 21205.
authors: A
authors: A
authors: Muhit
authors: Russell H. Morgan Dept. of Radiology, Johns Hopkins University, Baltimore, MD USA 21287.
authors: G
authors: G
authors: Thawait
authors: Carestream Health Inc., Rochester NY.
authors: N
authors: N
authors: Packard
authors: Carestream Health Inc., Rochester NY.
authors: R
authors: R
authors: Senn
authors: Carestream Health Inc., Rochester NY.
authors: D
authors: D
authors: Yang
authors: Carestream Health Inc., Rochester NY.
authors: J
authors: J
authors: Yorkston
authors: Russell H. Morgan Dept. of Radiology, Johns Hopkins University, Baltimore, MD USA 21287.
authors: J A
authors: JA
authors: Carrino
authors: Dept. of Biomedical Engineering, Johns Hopkins University, Baltimore, MD USA 21205 ; Russell H. Morgan Dept. of Radiology, Johns Hopkins University, Baltimore, MD USA 21287.
authors: J H
authors: JH
authors: Siewerdsen
keywords: Monte Carlo; cone-beam CT; extremities imaging; nonlinear reconstruction; scatter correction