# Name

recons3d_sirt - calculate 3-D reconstruction from a set of projections

# Usage

vol = recons3d_sirt(stack, list_proj, radius [, lambda, maxit, symmetry, tolerance])

## Input

- stack
name of the stack file containing projection data, projections have to be squares, i.e.,

**nx=ny**- list_proj
- list of projections to be included in the reconstruction
- lambda
- relaxation constant, (default - 1.0e-4), it has to be adjusted for each reconstruction
- maxit
- maximum number of iterations (default = 100, should be sufficient)
- symmetry
- point-group symmetry to be enforced, each projection will enter the reconstruction in all symmetry-related directions. The possibilities are

- "cn"
- "dn"
- "i"
- default is "c1" (no symmetry)

- tolerance
- stopping criterion, the program will terminate when the relative improvement of the structure is less than the tolerance set

## Output

- vol
- the 3-D reconstructed volume

# Description

Internally, this program subtracts from all input projection their averages computed

*outside*of a circular area with radius set to**radius**.The output structure is reconstructed within a sphere with radius set to

**radius**. Outside the sphere the background is set to zero.- If the number of iterations is set to one, a simple back-projection will be computed.

# Method

Simultaneous Iterative Reconstruction Technique

# Reference

# Author / Maintainer

Pawel A. Penczek

# Keywords

- category 1
- INVERSION
- category 2
- SPATIAL

# Files

reconstruction.py

# See also

# Maturity

- beta
- it is not finished.

# Bugs

None. It is perfect.