SqrtHessianRowSum Parameters :=
  
  ; The script requires an input image to be used as:
  ; - image estimate at which the square root of the Hessian row sum should be computed, or
  ; - an image template to specify the geometry of the approximate Hessian
  input image filename := 

  ; The output filename of the sqrt Hessian row-sum computation
  output filename := 

  ; bool to indicate if an approximate Hessian should be used or the true Hessian.
  ; This changes the usage of the `input image filename :=` key.
  ; Default value is 1
  use approximate Hessian := 1

  ; Define the objective function. 
  ; This should be the same objective function as used for reconstructions
  objective function type:= PoissonLogLikelihoodWithLinearModelForMeanAndProjData
  PoissonLogLikelihoodWithLinearModelForMeanAndProjData Parameters:=

    ; Measured data and additive sinograms
    input file := 
    additive sinogram := 

    Bin Normalisation type := From ProjData
    Bin Normalisation From ProjData :=
    ; normalistion sinogram
      normalisation projdata filename:= 
    End Bin Normalisation From ProjData:=

    ; Optional definition of a projector
    projector pair type := Matrix
    projector pair using matrix parameters :=
      matrix type := Ray Tracing
      ray tracing matrix parameters :=
        number of rays in tangential direction to trace for each bin := 50
      end ray tracing matrix parameters :=
    end projector pair using matrix parameters :=


    ; The use of a prior in the computation of the sqrt Hessian row sum is optional
    ; but will not work with an approximate Hessian row sum computation as priors do not have an approximate Hessian
    ; Default value is 0
    compute with penalty := 0

    prior type := Quadratic
    Quadratic Prior Parameters:=
      penalisation factor := 0.0
      only 2D:= 0
    END Quadratic Prior Parameters:=

  end PoissonLogLikelihoodWithLinearModelForMeanAndProjData Parameters:=

  ; Set the verbosity level (STIR default = 2)
  ; verbosity := 1

END :=
