Extracellular volume (ECV) - myocardium
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 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, pT1m 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:
- ATTR-amyloidosis – prognostic value
- acute myocardial infarction / myocardial necrosis
- myocardial scar tissue
Low values can occur in 4:
- lipomatous metaplasia/fat
- cardiac thrombus
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 2,4. There are only minor differences in regard to the myocardial region 6.
- 1. Moon JC, Messroghli DR, Kellman P, Piechnik SK, Robson MD, Ugander M, Gatehouse PD, Arai AE, Friedrich MG, Neubauer S, Schulz-Menger J, Schelbert EB. Myocardial T1 mapping and extracellular volume quantification: a Society for Cardiovascular Magnetic Resonance (SCMR) and CMR Working Group of the European Society of Cardiology consensus statement. (2013) Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance. 15: 92. doi:10.1186/1532-429X-15-92 - Pubmed
- 2. Daniel R. Messroghli, James C. Moon, Vanessa M. Ferreira, Lars Grosse-Wortmann, Taigang He, Peter Kellman, Julia Mascherbauer, Reza Nezafat, Michael Salerno, Erik B. Schelbert, Andrew J. Taylor, Richard Thompson, Martin Ugander, Ruud B. van Heeswijk, Matthias G. Friedrich. Clinical recommendations for cardiovascular magnetic resonance mapping of T1, T2, T2* and extracellular volume: A consensus statement by the Society for Cardiovascular Magnetic Resonance (SCMR) endorsed by the European Association for Cardiovascular Imaging (EACVI). (2017) Journal of Cardiovascular Magnetic Resonance. 19 (1): 1. doi:10.1186/s12968-017-0389-8
- 3. Ferreira VM, Piechnik SK, Robson MD, Neubauer S, Karamitsos TD. Myocardial tissue characterization by magnetic resonance imaging: novel applications of T1 and T2 mapping. (2014) Journal of thoracic imaging. 29 (3): 147-54. doi:10.1097/RTI.0000000000000077 - Pubmed
- 4. Philip Haaf, Pankaj Garg, Daniel R. Messroghli, David A. Broadbent, John P. Greenwood, Sven Plein. Cardiac T1 Mapping and Extracellular Volume (ECV) in clinical practice: a comprehensive review. (2017) Journal of Cardiovascular Magnetic Resonance. 18 (1): 1. doi:10.1186/s12968-016-0308-4 - Pubmed
- 5. Schelbert EB, Testa SM, Meier CG, Ceyrolles WJ, Levenson JE, Blair AJ, Kellman P, Jones BL, Ludwig DR, Schwartzman D, Shroff SG, Wong TC. Myocardial extravascular extracellular volume fraction measurement by gadolinium cardiovascular magnetic resonance in humans: slow infusion versus bolus. (2011) Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance. 13: 16. doi:10.1186/1532-429X-13-16 - Pubmed
- 6. Kawel N, Nacif M, Zavodni A, Jones J, Liu S, Sibley CT, Bluemke DA. T1 mapping of the myocardium: intra-individual assessment of the effect of field strength, cardiac cycle and variation by myocardial region. (2012) Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance. 14: 27. doi:10.1186/1532-429X-14-27 - Pubmed