# T2/T2* Map

Class: NodeT2Map

Calculates a T2 or T2* map from spin echo or gradient echo data with multiple echo times. At least two images are required, however, more images are advised if a larger range of T2/T2* values are expected. Echo times (TE) are detected automatically and it is required that other parameters affecting the contrast must be the same for all images. An optional mask can also be provided to limit the calculations to a region.

Produces a T2 / T2 * map[ms], and S0 which contains all weighting that is independent of T2/T2*. The parameter values are obtained by fitting the data to the signal equation

$$S = S_0\exp(-T_E/T_2)$$

in which T2 also can be T2*. Two algorithms can be applied. Either a nonlinear algorithm that performs a nonlinear least squares fit to the data, or a linear least squares fit which fits the linear model that results from taking the logarithm of the equation above.

## Inputs

#### Echo Series

Input image series with different echo times.

Type: Image4DFloat, Required, Multiple

Type: Image4DBool, Optional, Single

## Outputs

#### T2

Resulting T2 map.

Type: Image4DFloat

## Settings

#### Method Selection

Use the linearized or the nonlinear algorithm.

Values: Linear, NonLinear

## References

1. P.A. Boulby and F. Rugg-Gunn, “T2: the Transverse Relaxation Time,” in Quantitative MRI of the brain: Measuring changes caused by disease, P. S. Tofts, Ed. Wiley, 2003, pp. 143–201.

Keywords: T2, T2*, T2star, star, transverse, relaxation, parameter, map, linear, nonlinear