Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:CT and MRI imaging studies are very helpful during the first hours of evolution of the condition; it has been said that there are some lesions suggestive of vasculitis, including a disrupted white-grey matter connectivity, parenchymal punctiform lesions, or multiple focal lesions [17].
Category: