Extracellular volume - myocardium

Last revised by Joachim Feger on 20 Nov 2021

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 1,2. It measures the space, which is occupied by the extracellular matrix 1-4.

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) 1-5. T1 values can then be calculated pixel-wise from a signal intensity versus time curve fitting model 2. The administration of gadolinium leads to a shortening of the T1 value. Extracellular volume can be then calculated using the following formula 4:

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


nT1 = native T1,  pT1 = postcontrast T1, my = myocardium, bp = blood pool, hct = hematocrit

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 1-4.

Apart from fibrosis, it is elevated in the following myocardial diseases 1-4:

Low values can occur in 4:

Unlike native T1, extracellular volume seems not to be dependant on field strength, but similar to native T1 it varies between systole and diastole 2,4. There are only minor differences in regard to the myocardial region 6.  

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