Parametric Mapping in Paediatric Magnetic Resonance Imaging

Overview

Magnetic resonance imaging (MRI) is increasingly an important tool for diagnosis and management of cardiac diseases in children. One of the uses of MRI is tissue characterisation, in which the signal characteristics of the cardiac muscle (myocardium) can be determined with special techniques, known as parametric mapping. There is increasing evidence that parametric mapping may be able to identify regions of scarring in the myocardium, or detection of oedema/inflammation in the setting. This in turn can help predict disease course and add value to the management of patients. There is also evidence that other structures that are visualised in parametric mapping aside from the heart (e.g. liver and spleen) can also help improve diagnostic accuracy and guide management. Currently the majority of studies describing the use of parametric mapping is focused on adults, with limited data on its use in children. The parametric mapping values can also differ amongst different machines, so calibration with normal subjects are also required.

Magnetic resonance Imaging (MRI) can provide tissue characterisation without radiation and need for invasive biopsy. Parametric mapping techniques (T1 mapping, extracellular volume fraction, T2 mapping, T2\* mapping) are methods of quantitative analysis of tissue properties, and are currently commercially available. T1 mapping, extracellular volume fraction (ECV) and T2\* mapping provides knowledge about the tissue properties of the myocardium, interstitium and adjacent structures,and can provide information for diagnosis of fibrosis, inflammatory and infiltrative diseases. T2 mapping is useful for assessing oedema, which may be useful in monitoring disease activity such as myocarditis. Parametric mapping has proven clinical utility in iron deposition, amyloid disease, Anderson-Fabry disease and myocarditis. In addition to assessment of cardiac muscle, tissue characterisation can also be performed in adjacent organs that are included in the field of view of parametric mapping (e.g. liver and spleen). Parametric mapping may provide important diagnostic information for decision making, patient monitoring and management planning. The investigators aim to 1. recruit healthy volunteers as controls to establish normal local reference ranges for parametric mapping values 2. recruit patients undergoing clinically indicated cardiac MRI to perform parametric mapping, and compare the parametric mapping values between normal controls and patients.