Table 1.

A summary of technical and physiological pitfalls and their effects on accuracy and precision in T ₁ and ECV mapping

Pitfall	Mechanism	Effect on T 1 mapping		Effect on ECV mapping		Solutions (developing or speculative)
		Acc.	Prec.	Acc.	Prec.
Look–Locker correction	Assumes continuous, low-flip-angle spoiled GRE; MOLLI T 1 mapping can violate these assumptions	••	•	••	•	Pauses in seconds, saturation recovery sequence, shallower flip angle
Partial volume	Coarse in-plane resolution leads to inclusion of multiple tissues in some voxels, causing T 1 errors	••	••	••	••	Conservative ROI drawing, finer in-plane resolution, (black-blood mapping, slower segmented acquisition)
Prep. pulse factors	Adiabatic prep. pulses, robust to B 0 and B 1 inhomogeneity, are long and lead to T 2 decay and T 1 bias	•••	••	•	•	Appropriate pulse design and/or optimised B 0 and B 1 shimming
Multishot bSSFP readout	Sensitive to T 2 and off-resonance and requires catalysation before each imaging readout	•••	••	•	•	Appropriate catalysation scheme, coarser in-plane-resolution, shorter TR. Alternatively, use spoiled GRE
Field strength	B 0 and B 1 inhomogeneity ↑ with field strength, T 1↑, T 2↓, SNR↑	••	•	•	•	Appropriate B 0 and RF shimming, trading off SNR for shallower flip angle, longer pause intervals
k-space filling	Linear ordering causes saturation, centric ordering leads to artefacts	•	•	•	•	Linear ordering is adequate, (paired ordering may offer benefits)
Signal-to-noise	Noise level affects sampled T 1-weighted data when fitting	••	••	••	•	Consider thicker slices, coarser in-plane resolution, using a 3T system
Poor breath-holding	Misregistration of source images and T 1 error	••	••	••	••	Patient coaching, image registration, (free-breathing T 1 mapping)
Cardiac motion	Mistimed acquisitions and misregistration of images	••	••	••	••	Fit acquisition into diastolic/systolic pause, image registration
Flowing blood	Mixture of magnetisation histories in left-ventricular blood	•	•	•	•	Pauses in seconds; position patient carefully or avoid short bore MRI systems, if possible
Magnetisation transfer (MT)	Exchange between free and bound water pools distorts T 1 recovery, causing T 1 underestimation	••	•	•	•	Lower flip angle, longer TR, saturation recovery sequence. (Alternatively, MT may improve sensitivity to disease)

This table provides an overview of the pitfalls listed in the text, with no intended significance in the order they appear. The pitfalls are listed with the mechanisms by which they influence T ₁ and ECV mapping, qualitative ratings of how they affect T ₁ and ECV accuracy and precision, and possible strategies for eliminating or mitigating them, with developing or speculative solutions shown in brackets. Given the popularity of the original modified Look–Locker inversion recovery (MOLLI) T ₁ mapping sequence, it is considered the standard here, with other sequences being offered as potential solutions to pitfalls. Ratings are given as one to three blots, with • being mild, •• being moderate, and ••• being severe; however, it should be clear that none of the pitfalls dominate, and their relative importance is highly dependent on the application

ECV extracellular volume, GRE gradient recalled echo, RF radiofrequency, ROI region of interest, SNR signal-to-noise ratio, TR repetition time, and bSSFP balanced steady-state free-precession