What is the likely lesion here?
This space occupying lesion is likely the cause of the patient's confusion. The differential diagnosis is still wide from primary tumour, metastasis, cerebral abscess...
What investigation could give more information while the patient is in the scanner?
IV contrast can be used in CT and MRI to give more information about the behaviour of lesions. For the rate the contrast is given, patients should have at least a 20G (pink) cannula if contrast is likely.
What risks does contrast include?
The immediate risk is of anaphylaxis which is why a doctor should be present during the scan. Out-of-hours it is usually the requesting clinician, or their junior! There is also a risk of kidney injury (contrast induced nephropathy) which is why renal function must be known before scanning.
No evidence of ischaemic or haemorrhagic stroke. No extra-axial bleeds or collections.
Ring shaped lesion in left occipital lobe with hypodense centre and surrounding hypodensity.