From the link:
if the word osasto is important:
head of department/section
chief of department/section
department head
chief specialist (erikoislääkäreiden esimies)
or if the word ylilääkäri is important:
chief physician
senior medical officer (viranomainen)
physician-in-chief
head physician
chief of service (Chief of Service, Emergency Room, Am.)
head (Head, Paediatric Department)
chief (Chief Paediatrician)
chief medical officer
clinical director