# T1 VFA

Class: NodeT1VFA

Calculate a T1 map using the variable flip angle (VFA) method. At least two images are required, however, more images are advised if a larger range of T1 values are expected. Flip angle (FA) and repetition time (TR) are detected automatically and it is required that the TR is the same in all images.

In addition to images with varying flip angle, a B1 map can also be provided to improve the accuracy. This is particularly useful at high field strengths. The B1 map represents a scaling of the FA, hence value 1 indicates that the nominal FA is achieved. 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 a linearized version of the spoiled gradient echo equation:

$$\displaystyle S = S0\frac{1-\exp(-T_R/T_1)}{1-\cos(FA \cdot B_1)\exp(-T_R/T_1)}\sin(FA\cdot B_1).$$

## Inputs

#### Dataset

Input images with varying FA.

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

Type: Image4DBool, Optional, Single

#### B1 Correction

Input B1 correction image.

Type: Image4DFloat, Optional, Single

## Outputs

#### T1

T1 map.

Type: Image4DFloat

#### S0

S0 map.

Type: Image4DFloat

## References

1. S.C.L. Deoni, T. M. Peters, and B. K. Rutt, “High-resolution T1 andT2 mapping of the brain in a clinically acceptable time with DESPOT1 and DESPOT2,” Magn. Reson. Med., vol. 53, no. 1, pp. 237–241, Jan. 2005.

Keywords: T1, longitudinal, map, relaxation, B1, flip, angle, mri, dce