Physics Just the Basics Series #09 - T1 mapping and ECV-Presentation

Video Transcription

Video Summary

The webinar introduced the basics of cardiac MRI T1 mapping and extracellular volume (ECV) mapping, with a focus on the two major T1 mapping families: MOLLI and SASHA. The speaker explained what T1 relaxation means, why it can vary across tissues, and how MRI measures it indirectly through RF pulses and signal recovery curves. T1 maps provide pixel-wise information that can help identify disease processes such as fibrosis, infarction, edema, and inflammation.<br /><br />The talk then described how ECV is derived from native and post-contrast T1 maps by converting to R1 values, calculating delta R1, and combining this with hematocrit and blood pool measurements. ECV is useful because it reflects extracellular space and is relatively independent of field strength.<br /><br />A major part of the lecture compared MOLLI and SASHA in terms of accuracy and precision. MOLLI generally provides higher precision but is more sensitive to heart rate, off-resonance, flip angle, B1 inhomogeneity, motion, and magnetization transfer effects, which can bias T1 values. SASHA is more accurate and less sensitive to many of these issues, though its images are often noisier and less precise. The speaker also emphasized that ECV is often less biased than native T1, but values should not be directly compared across different sequences because sequence-related biases differ.<br /><br />Practical recommendations included careful shimming, reviewing error maps, being cautious with motion and arrhythmias, and avoiding direct comparison of absolute T1 or ECV values between MOLLI and SASHA.

Keywords

cardiac MRI

T1 mapping

extracellular volume

ECV mapping

MOLLI

SASHA

native T1

post-contrast T1

fibrosis

magnetization transfer