Introduction to MRI scans

MRI scanning, or magnetic resonance imaging, uses powerful magnets and radio waves rather than X-rays to generate detailed images of the body. It provides exceptional contrast between different soft tissues and can create images in multiple planes without moving the patient. Unlike CT, MRI does not involve ionising radiation, which makes it particularly valuable for repeated imaging or for younger patients.

In interventional neuroradiology, MRI plays a central role in the assessment of brain and spinal conditions. It is highly sensitive for detecting ischaemia in stroke, small vascular malformations, and brain or spinal cord pathology that may not be visible on CT. It also contributes to the evaluation of aneurysms and subarachnoid haemorrhage, as it can demonstrate vessel walls, surrounding brain tissue, and the effects of blood products at different stages. MRI is especially valuable in detecting aneurysms located in regions that may be obscured by bone on CT, such as the skull base or posterior circulation, where its superior soft tissue contrast provides clearer information.

Magnetic resonance angiography (MRA) is a specialised application that allows blood vessels to be imaged with or without intravenous contrast. Contrast-enhanced MRA uses gadolinium-based agents to improve vascular detail, while non-contrast techniques rely on blood flow signals to depict arteries and veins. This makes MRA particularly useful for detecting aneurysms, arteriovenous malformations, and vessel stenosis, as well as for long-term follow-up and surveillance, often avoiding the need for repeated radiation exposure.

The advantages of MRI and MRA are their excellent soft tissue detail, the absence of radiation, and the ability to evaluate both vessels and surrounding structures in a single examination. They are also especially effective in areas where CT is limited by bone. Limitations include longer scanning times, sensitivity to patient movement, and contraindications in patients with certain implants or severe claustrophobia. Metallic devices such as coils or stents can cause artefacts, although these are often less pronounced than in CT. For this reason, MRI and MRA are typically used in planned or follow-up settings, while CT and CTA are preferred for rapid emergency imaging.