Acquires three-directional, three-dimensional, phase-contrast data over time (the fourth dimension)

Allows assessment of intracardiac flow in three dimensions

Measures the direction and magnitude of the diffusion of water molecules

In the myocardium, water diffusion occurs preferentially along the long axis of cardiomyocytes

Used to characterise myocardial microstructure

PET and MRI hardware in the same gantry allows for simultaneous PET-MR acquisition

Wide potential given exploration for novel PET tracers for cardiac application and emerging MRI methods

Insight into complex intracardiac flow in several disease states

Quantification of valvular flow—both forward and backward (regurgitant) flows, for example, mitral regurgitation

Accurate assessment systemic to pulmonary blood flow

Visualisation and identification of shunt in congenital heart disease

Identification and assessment of peak velocity through aortic valve in three-dimension for confirming pressure gradient in aortic stenosis

Emerging role in left ventricular diastolic assessment

Myocardial infarction: depiction of oedema and scar tissue, changes to the helical cardiomyocyte arrangement and myocardial sheetlet orientations

Hypertrophic cardiomyopathy: detect early microstructural changes and detection of fibre disarray which can identify patients at greater risk of arrhythmias and sudden cardiac death

Dilated cardiomyopathy: assessment of myocardial sheetlet mobility between diastole and systole, which is significantly reduced in patients with DCM

Congenital heart disease: DTI can help elucidate how microstructural abnormalities in impacts on clinical outcomes

Evaluation of cardiac masses using PET and MRI

Assessment of cardiac sarcoidosis, although requires strict dietary preparation. May help to improve diagnosis and allow for risk stratification

Emerging role of coronary imaging with CMRA and PET imaging of high-risk plaque

Offline multiplanar assessment of vascular, valvular and intracardiac flow

Allows to quantify transvalvular flow for all four valves for the same averaged cardiac cycle—this improves precision for Qp:Qs assessment

Valve tracking allows to improve valvular flow assessment

Fast acceleration techniques have made it possible to acquire 4D-flow in 6–10 min

Non-invasive method of examining in vivo myocardial microstructure

Non-contrast sequence

Can be acquired free-breathing

Relatively quick acquisition time

Simultaneous acquisition allows precise co-registration of images and cross-validation of findings

PET allows absolute quantification of biological processes which can be combined with multiparametric data derived from MRI on anatomy, morphology and tissue characterisation

Can use MRI data to motion correct PET data

Potential to reduce ionising radiation dose

Lower temporal resolution when compared with standard two-dimensional phase-contrast imaging

Cumbersome quality checks and corrections are necessary for postprocessing

Susceptibility to artefacts from bulk motion during the cardiac cycle as well as myocardial strain during diffusion encoding, which significantly impacts on signal-to-noise ratio

Newer sequences require more powerful gradient hardware

Expensive and requires access to cyclotron or generator for PET tracers

Ionising radiation to patients

Challenges with attenuation correction

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