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Moving beyond "Bright" or "Dark." In this level, we explore the physics of T1 and T2 mapping to calculate Extracellular Volume (ECV)—the most sensitive way to detect diffuse fibrosis and infiltrative diseases like amyloidosis.
Late Gadolinium Enhancement (LGE) is the gold standard for scar, but it relies on a relative difference between scarred and healthy tissue. If the entire heart is diseased (diffuse fibrosis), there is no "normal" tissue to compare against, and the whole heart may appear dark.
ECV Mapping solves this by measuring the T1 relaxation time of every pixel. Since contrast agents distribute exclusively in the extracellular space, we can mathematically subtract the blood pool signal to find exactly how much space exists between the heart cells.
"Amyloidosis is the classic 'High ECV' diagnosis. Even without obvious LGE, an ECV of >40% is nearly pathognomonic for cardiac amyloid. Remember to always correct for hematocrit!"