Abstract: The invention provides a method of embolus therapy comprising administering into the vasculature of a perfused zone of tissue in a human or non-human animal subject a composition comprising particles of a size or formulation selected to generate emboli at a target site within said subject, characterised in that as said particles are used solid water-insoluble particles of a non-radioactive diagnostically effective compound or vesicles encapsulating a non-radioactive diagnostically effective compound or a solution thereof, and in that embolus location is detected by a diagnostic imaging technique.