# T1 IR

Class: NodeT1IR

Calculate a T1 map using spin echo inversion recovery (IR) data. Atleast two images are required, however, more images are advised if a larger range of T1 values are expected. Inversion times, inversion flip angle (FA) and repetition time (TR) are detected automatically and it is required that the FA and TR is the same in all images. An optional mask can also be provided to limit the calculations to a region.

Produces a T1 map[ms], and S0 which is a proton and T2 weighted image. The parameter values are obtained by fitting the data to the signal equation:

$$\displaystyle S = S_0(1–(1-\cos(FA))\exp(-T_1/T_I)+\exp(-T_R/T_1))$$

## Inputs

#### Dataset

At least two inut images with different inversion times.

Type: Image4DFloat, Required, Multiple (Minimum = 2)

A mask which defines the region in which the T1 values will be calculated.

Type: Image4DBool, Optional, Single

## Outputs

#### T1

The T1 map.

Type: Image4DFloat

#### S0

The S0 map.

Type: Image4DFloat

## Settings

#### Model Selection

For phase sensitive IR use the Real model, otherwise use the magnitude model.

Values: Real, Magnitude

## References

1. Gowland and V. L. Stevenson, “T1: the longitudinal relaxation time,” in Quantitative MRI of the brain: Measuring changes caused by disease, P. S. Tofts, Ed. Chichester: Wiley, 2003, pp. 111–41.

Keywords: T1, IR, spin, echo, inversion, recovery, longitudinal, relaxation