In a Dutch hospital you normally need a referral from your GP or a medical specialist. Many private clinics let you book an appointment directly.
Check your insurance first
Without a referral, basic Dutch health insurance usually does not reimburse the examination, so you pay the full amount yourself. Always read the conditions of your supplemental policy, and ask your insurer for written confirmation if anything is unclear.
Why a referral is still worth having
A referral also gives the radiologist your clinical background, which helps them choose the right protocol and interpret the images in context. If you have symptoms, start with your GP.