# T1 IR

Class: NodeT1IR

Calculates 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 of interest.

Produces a T1 map in the same units as TR, and $$\text{S}_0$$ which is a proton and T2 weighted image. The parameter values are obtained by fitting the data to the signal equation:

$$$S_i = S_0(1–(1-\cos(FA))e^{-T1/TI_i}+e^{-TR/T1}),~~~~i = 1, 2, ..., n \tag{1}$$$

where $$n$$ is the number of images used.

IR example

## Inputs

#### Dataset

A set IR images with equal TR, flip angle and varying inversion time (at least 2 diffrent inversion times). Note that TE should be the same for all images too.

MetaData: The fields RepetitionTime, FlipAngle and InversionTime must be present in the metadata for all images. The flip angle must be given in degrees.

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

An (optional mask) that specifies which pixels to analyse.

Type: Image4DBool, Optional, Single

## Outputs

#### T1

A T1 map calculated for the voxels specified by the mask or in all voxels if no mask is provided. The T1 map has the same unit as the TR, TIs, typically given in ms.

Type: Image4DFloat

#### S0

A proton and T2 weighted image.

Type: Image4DFloat

## Settings

#### Model Selection

Selects the model to use.

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.

1. P. A. 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 estimation, inversion recovery, T1 map