The goal of this study is to investigate the encapsulation of fluid collections in patients with ANP using serial MRI. The main questions it aims to answer are: * Evaluating the timing of encapsulation of necrotic fluid collection using serial non-enhanced MRI. * Identifying the factors that affect the timing of encapsulation of necrotic fluid collections Participants will undergo serial MRI scans (all with the same protocol) performed starting at day 15. Subsequent scans will be performed at 5 days interval till the clinically significant encapsulation (for all the collections in an individual patient) is seen or patients are excluded from the protocol due to intervention.