title: Accelerated statistical reconstruction for C-arm cone-beam CT using Nesterov's method.
abstract: OBJECTIVE
  To accelerate model-based iterative reconstruction (IR) methods for C-arm cone-beam CT (CBCT), thereby combining the benefits of improved image quality and/or reduced radiation dose with reconstruction times on the order of minutes rather than hours.
  
  
  METHODS
  The ordered-subsets, separable quadratic surrogates (OS-SQS) algorithm for solving the penalized-likelihood (PL) objective was modified to include Nesterov's method, which utilizes "momentum" from image updates of previous iterations to better inform the current iteration and provide significantly faster convergence. Reconstruction performance of an anthropomorphic head phantom was assessed on a benchtop CBCT system, followed by CBCT on a mobile C-arm, which provided typical levels of incomplete data, including lateral truncation. Additionally, a cadaveric torso that presented realistic soft-tissue and bony anatomy was imaged on the C-arm, and different projectors were assessed for reconstruction speed.
  
  
  RESULTS
  Nesterov's method provided equivalent image quality to OS-SQS while reducing the reconstruction time by an order of magnitude (10.0 ×) by reducing the number of iterations required for convergence. The faster projectors were shown to produce similar levels of convergence as more accurate projectors and reduced the reconstruction time by another 5.3 ×. Despite the slower convergence of IR with truncated C-arm CBCT, comparison of PL reconstruction methods implemented on graphics processing units showed that reconstruction time was reduced from 106 min for the conventional OS-SQS method to as little as 2.0 min with Nesterov's method for a volumetric reconstruction of the head. In body imaging, reconstruction of the larger cadaveric torso was reduced from 159 min down to 3.3 min with Nesterov's method.
  
  
  CONCLUSIONS
  The acceleration achieved through Nesterov's method combined with ordered subsets reduced IR times down to a few minutes. This improved compatibility with clinical workflow better enables broader adoption of IR in CBCT-guided procedures, with corresponding benefits in overcoming conventional limits of image quality at lower dose.
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205.
authors.forename: Adam S
authors.initials: AS
authors.lastname: Wang
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205.
authors.forename: J Webster
authors.initials: JW
authors.lastname: Stayman
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Otake
authors.affiliation: Siemens Healthcare XP Division, Erlangen, 91052, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Vogt
authors.affiliation: Siemens Healthcare XP Division, Erlangen, 91052, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Kleinszig
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205.
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Siewerdsen
mesh_terms: D000465:Algorithms; D054893:Cone-Beam Computed Tomography / Q000295:instrumentation / Q000379:methods*; D006257:Head / Q000000981:diagnostic imaging; D006801:Humans; D008954:Models, Biological; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011860:Radiography, Abdominal / Q000295:instrumentation / Q000379:methods; D013223:Statistics as Topic; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D013997:Time Factors