Extracellular volume (ECV) - myocardium

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Extracellular volume (ECV) refers to the space or volume of a tissue, which is not occupied by cells. Apart from the usual extracellular space, which surrounds the cells of a specific tissue it also includes the intracapillary plasma volume . It measures the space, which is occupied by the extracellular matrix .

Measurement

A series of native T1 and postcontrast T1 images an acquired and co-registered. This can be done by an equilibrium infusion or after a bolus injection after waiting for a sufficient amount of time (15min) . T1 values can then be calculated pixel-wise from a signal intensity versus time curve fitting model . The administration of gadolinium leads to shortening of the T1 value. Extracellular volume can be then calculated using the following formula :

ECV = (1-hct) [(1/pT1my - 1/nT1my) / (1/pT1bp - 1/nT1bp)]

nT1 = native T1,  pT1m postcontrast T1, my = myocardium, bp = blood pool , hct = hematocrit

Interpretation

It is of interest in the myocardium as a biomarker for interstitial disease. In the absence of any diffuse infiltrative disease or myocardial edema, it can be also considered as a biomarker for myocardial fibrosis .

Apart from fibrosis, it is elevated in the following myocardial diseases :

Low values can occur in :

Influencing factors

Unlike native T1 extracellular volume (ECV) seems not to be dependent on field strength, but similar to native T1 it varies between systole and diastole . There are only minor differences in regard to the myocardial region .

See also