title: Model-based optoacoustic inversions with incomplete projection data.
abstract: OBJECTIVE
  Optoacoustic imaging is an emerging noninvasive imaging modality that can resolve optical contrast through several millimeters to centimeters of tissue with diffraction-limited resolution of ultrasound. Yet, quantified reconstruction of tissue absorption maps requires optoacoustic signals to be collected from as many locations around the object as possible. In many tomographic imaging scenarios, however, only limited-view or partial projection data are available, which has been shown to generate image artifacts and overall loss of quantification accuracy.
  
  
  METHODS
  In this article, the recently introduced interpolated-matrix-model optoacoustic inversion method is tested in different limited-view scenarios and compared to the standard backprojection algorithm. Both direct (TGSVD) and iterative (PLSQR) regularization methods are proposed to improve the accuracy of image reconstructions with their performance tested on simulated and experimental data.
  
  
  RESULTS
  While for full-view tomographic data the model-based inversion has been generally shown to attain higher reconstruction accuracy compared to backprojection algorithms, the incomplete tomographic datasets lead to ill-conditioned forward matrices and, consequently, to error-prone inversions, with strong artifacts following a distinct ripple-type pattern. The proposed regularization techniques are shown to stabilize the inversion and eliminate the artifacts.
  
  
  CONCLUSIONS
  Overall, it has been determined that the regularized interpolated-matrix-model-based optoacoustic inversions show higher accuracy than reconstructions with the standard backprojection algorithm. Finally, the combination of model-based inversion with PLSQR or TGSVD regularization methods can lead to an accurate reconstruction of limited-projection angle optoacoustic data and practical systems for optoacoustic imaging in many realistic cases where the full-view dataset is unavailable.
authors.affiliation: Institute for Biological and Medical Imaging, Technische Universität München und Helmholtz Zentrum München, Ingoldstädter Landstrafsse 1, D-85764 Neuherberg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Buehler
authors.forename: Amir
authors.initials: A
authors.lastname: Rosenthal
authors.forename: Thomas
authors.initials: T
authors.lastname: Jetzfellner
authors.forename: Alexander
authors.initials: A
authors.lastname: Dima
authors.forename: Daniel
authors.initials: D
authors.lastname: Razansky
authors.forename: Vasilis
authors.initials: V
authors.lastname: Ntziachristos
mesh_terms: D000162:Acoustics; D000465:Algorithms; D016477:Artifacts; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods*; D055620:Optical Phenomena; D019047:Phantoms, Imaging