DR ERR - Density Reference - Error between two volumes

PURPOSE

Calculates the mean relative error and the discepancy between two volumes. A scaling factor and additive constant is determined to scale the first volume such that the errors are minimized.

SEE ALSO

DR DIFF

[Density Reference - Error & Difference between two volumes]

USAGE

.OPERATION: DR ERR

.FIRST FILE: 3DR004
[Enter name of first volume]

.SECOND FILE: 3DR005
[Enter name of second volume.]

NOTES

1. Error formulas:
   Mean relative error: E = SUM |F*V2-V1-CON| / SUM |V1-AV1|
   Discrepancy: E = SQRT [SUM |(F*V2-V1-CON)**2| / SUM |(V1-AV1)**2|]
   Where:
   V1,V2 = Voxel values of volume 1 and volume 2.
   F = Optimum scaling factor.
   CON = Offset between the two volumes.
   AV1 = Average voxel under mask in volume 1
   

2. For more details about the error measures see :
   Colsher J.G. Iterative Three-dimensional Image Reconstruction from Tomographic Projections, Computer Graph. & Image Proc. 6, (1977) 513-537.
   Herman G.T. Two Direct Methods for reconstructing pictures from their projections: A comparative study. Computer Graph. & Image Proc. 1,(1972) 123-144

SUBROUTINES

COMP3D

CALLER

VTIL2