Depends on the setting and the disposability of the MRI. Perfusion CT works well, too, and is considerably faster. It may also depend what exactly you want to assess: penumbra before thrombectomy or some functional prediction. By the way, what does LCPD mean exactly?

Thank you so much

I mean Legg calve Perthes disease

Perfusion MRI is the best way to evaluate hip at children with LCP between 4 and 8 years. Before 4 years old or after 8 years (age of onset) the treatment don't change very much the final result (after Salter and Harring opinion) and perfusion MRI isn't really necessary at first visit.