MRI — Magnetic Resonance Imaging

Magnetic resonance imaging is an advanced diagnostic imaging modality that does not rely on ionising radiation. Instead, the scanner generates a powerful magnetic field that temporarily aligns protons within the water molecules of the patient's body tissues. Radiofrequency pulses are then emitted, causing these protons to absorb energy and alter their alignment.

When the radiofrequency pulses cease, the protons return to their baseline state, releasing energy detected by the scanner's sensors. Computer algorithms translate these signals into high-resolution, cross-sectional images that provide exquisite contrast between normal and abnormal soft tissues.

Accurate imaging is central to effective cancer care. An MRI provides clear anatomical detail that helps doctors detect small tumours, establish precise cancer stages, and assess whether a tumour has invaded neighbouring nerves, blood vessels, or tissue planes. Surgeons rely on MRI scans to plan complex operations, while radiation oncologists use them to delineate target boundaries, helping to protect nearby healthy organs from unnecessary radiation exposure.

MRI itself is an imaging procedure rather than a biomarker test. However, it often incorporates a specialised contrast dye containing gadolinium, administered intravenously, to highlight blood flow and illuminate tumours. Multiparametric MRI combines anatomical and functional sequences, such as diffusion-weighted imaging, to assess cellular density within lesions.

MRI is frequently used in diagnosing and staging tumours of the central nervous system (brain and spinal cord), musculoskeletal sarcomas, breast cancer, prostate cancer, rectal cancer, and liver metastases. It is also used in gynaecological cancers, such as cervical and uterine malignancies.

The anatomical detail from an MRI informs whether a tumour is surgically resectable and helps define surgical margins. In radiotherapy planning, MRI images are frequently fused with CT scans to guide precision treatment beams. Follow-up scans are also used after therapy to distinguish residual tumour from post-treatment scar tissue.