Postoperative delirium (POD) is a frequent disorder of consciousness, arousal and attention in elderly patients following surgery. The glymphatic system is a newly discovered waste cleaning system of the brain. Glymphatic transport of CSF has been shown to be impaired by perioperative factors. Reduced glymphatic transport has been related to a vicious cycle of neuroinflammatory marker build-up, leading to increased glymphatic transport impairment, leading eventually to neuronal damage and hence cognitive impairment. Therefore, glymphatic transport impairment has been suggested to be an important mechanism underlying POD. But not everyone who undergoes surgery presents POD, so what makes certain patients susceptible to POD? It has been suggested that glymphatic transport may already be impaired at preoperative baseline, which, with the added burden of perioperative strain on the system, 'tilts' the patient into POD. The primary aim of the current study is to measure glymphatic transport in patients preoperatively and assess whether patients who present POD ('POD patients') show impairments in preoperative glymphatic transport, relative to patients who do not present POD ('noPOD patients'). Two aspects of glymphatic transport will be assessed using two noninvasive MR techniques - fast-acquisition BOLD-fMRI and DTI-MR. POD will be assessed using the 3D-CAM questionnaire and patients will also be assessed preoperatively for symptoms of depression, state/trait anxiety and cognitive status using standardised self-report measures.