T1 Estimation

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Calculate a T1 map using spin echo inversion recovery (IR) data. The input must be a multi-channel image, where each volume has an associated flip angle (FA) and repetition time (TR). At least two volumes are required, however, more are advised if a larger range of T1 values are expected. Flip angle (FA) and repetition time (TR) can be supplied via the metadata for each volume, or as input numerical arrays. 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:

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

where \(n\) is the number of images used.

Inputs

Dataset

An image or a list of images (for batch processing) where channel dimensions are used for the different \(TI\) values. At least two volumes are needed and they should have the same \(TR\) and echo time.

Type: Image, List, Required, Single

Mask

Mask(s) used to confine the region in which the signal model is fitted.

Type: Mask, List, Optional, Single

Outputs

T1

The estimated \(T1\) parameter map.

Type: Image, List

S0

The estimated \(S_0\) parameter map.

Type: Image, List

Settings

Configure

IR Method Selection

The type of signal model used, i.e. whether it is the real signal (Phase Sensitive) or magnitude signal that has been measured.

Values: Phase Sensitive, Magnitude

Batch Size Integer

The number of voxels that are computed per batch. This is a trade-off between performance and memory consumption.

Keep Metadata Boolean

Keep or discard metadata in the parameter maps.

Configure NonLinear

Tolerance Float

The threshold change in the objective function. Changes smaller than this value imply that the fitting has converged.

Max Iterations Integer

Maximum number of iterations.

Return Convergence Map Boolean

Return a binary mask, where all true voxels have converged in the fit. This can be used to exclude voxels that did not converge.

Metadata

Repetition Time Source Selection

Select the \(TR\)-value source for the calculation. The \(TR\)-values can be taken from the metadata, or can be supplied as an input Numeric Array.

Values: Metadata, Numeric Array Input

Inversion Time Source Selection

Select the \(TI\)-value source for the calculation. The \(TI\)-values can be taken from the metadata, or can be supplied as an input Numeric Array.