Table 1.

Meaning of equation variables.

Symbol	Meaning
M0,PCr	Equilibrium longitudinal magnetisation of PCr
$M_{\text{PCr}}^{\text{Ctrl}}$	Measured steady-state longitudinal PCr magnetisation, with mirrored control saturation applied.
$T_{\text{R}}^{\text{Short/Long}}$	Short and long TR, where both $T_{\text{R}}^{\text{Short/Long}}<5{\text{T}}_1.$
$M_{\text{PCr}}^{\prime }$	Longitudinal PCr magnetisation, with on-resonance saturation of γ-ATP applied. TR ≈ 5T1
$M_{\text{PCr}}^{\prime }(T_{\text{R}}^{\text{Short}}/T_{\text{R}}^{\text{Long}})$	Measured steady-state longitudinal PCr magnetisation, with on-resonance saturation of γ-ATP applied.
$T_{\text{1}}^{\prime }$	Measured T1 in the presence of on-resonance saturation of γ-ATP applied.
$T_{\text{1}}^{*}$	Intrinsic T1, i.e. without the effect of exchange.