## 3 Cardiovascular Disease
### Myocardial Infarction
#### 3.3.3 Imaging Myocardial Infarction  
Cardiovascular magnetic resonance (CMR) is clinically established as the gold standard non-invasive imaging modality for the assessment of myocardial injury in the context of ischaemic heart disease and heart failure. In addition to highly reproducible 3D volumetric assessment of biventricular dimensions and function, CMR offers a spectrum of non-contrast and contrast enhanced myocardial tissue characterisation functions. [PERSON] et al. proposed a short-inversion-time inversion-recovery (STIR) magnetic resonance imaging sequence with preparatory radio-frequency pulses to eliminate signal from flowing blood to distinguish between normal and abnormal myocardial tissues and image focal high signal intensity consistent with myocardial oedema following an acute myocardial infarction [95]. Here, a segmented rapid acquisition with relaxation enhancement (turbo spin echo) readout is used, with the inversion-recovery delay adjusted to null fat. To enable a more quantifiable and reproducible assessment of myocardial oedema and inflammation post-MI, 2D and more recently free breathing 3D whole heart myocardial T2 mapping sequences have been proposed [96; 97]. It is also possible to take advantage of native myocardial T1 values to differentiate between normal and pathological myocardium including myocardial fibrosis, oedema, inflammation and infiltrative processes such as Fabry disease, amyloidosis and hemosiderosis [98; 99; 100]. Furthermore, recent pre and post contrast myocardial T1 mapping techniques have enabled a non-invasive and quantifiable assessment of the myocardial extracellular volume (ECV), a technique that was previously only feasible through invasive histopathological analysis [102]. This is particularly important in assessing pathological remodelling within the myocardial extracellular matrix, such as extracellular volume expansion caused by oedema, inflammation, infiltrative processes and diffuse and focal fibrosis [102]. Contrast-Enhanced Imaging  
Leveraging the differential washout time of gadolinium-based contrast agents within normal and pathological myocardial tissue (e.g., fibrotic scar tissue), T1-weighted inversion recovery prepared late gadolinium enhancement (LGE) CMR is able to directly visualise the transmural extent and pattern of myocardial scar (e.g., following acute myocardial infarction) with a high degree of accuracy, offering both prognostic and therapeutic guidance to clinicians [103]. Collagen  
Recent studies have demonstrated that early gadolinium enhancement (EGE) myocardial imaging identifies both reversibly and irreversibly injured myocardium following an acute MI, thus detecting and quantifying potential areas at risk [104; 105; 106]. However, none of these techniques are able to directly visualise and assess individual components of the extracellular matrix and its underlying biological processes. To overcome this limitation, targeted molecular imaging of individual extracellular matrix components is required. One example is EP-3533, the same collagen-binding agent used for atherosclerotic imaging [107]. In a mouse model of myocardial infarction, [PERSON] et al. demonstrated significantly longer washout time for EP-3533 compared to gadopentetate dimeglumine in regions of post-MI scarring and in normal myocardium, with good correlation on histologic sections stained for collagen and EP-3533 enhanced areas seen on inversion-recovery CMR images (Figure 15) [107]. Furthermore, there was a two-fold higher concentration of EP-3533 within post infarction tissues compared to normal myocardium. Elastin  
In a separate approach, [PERSON] et al. used ESMA to image elastin fibres for in vivo assessment of extracellular matrix remodelling in a mouse model of myocardial infarction [108].