MRI Sequences

An MRI "sequence" is a particular recipe of magnetic and radio-wave pulses that makes the same anatomy look different in a deliberate way. Every spinal MRI is built from several sequences, because no single one shows everything. Understanding the common names — T1, T2, STIR and others — helps explain why your scan contains many sets of images that look quite different from each other even though they show the same spine.

By changing the timing of the pulses, radiologists control which tissues appear bright and which appear dark. On a T1-weighted sequence, fat looks bright and fluid looks dark; it is good for showing anatomy and bone marrow. On a T2-weighted sequence, fluid looks bright, which makes the water-rich spinal fluid, swelling and healthy discs stand out — useful for seeing nerve compression and disc changes. Fat-suppressed sequences such as STIR deliberately darken fat so that areas of swelling, bruising, infection or inflammation "shine through" and become obvious. Additional sequences can be tuned to detect bleeding, or to trace the nerves.

From your side, the sequences are simply the reason the scan is made up of several separate runs, each with its own pattern of knocking and buzzing noises and each lasting a few minutes. You do not have to do anything different — the radiographer selects the combination needed for your particular question. It is helpful to know that the varied, sometimes rhythmic sounds are just the machine switching between these different recipes.

Using several sequences is what gives MRI its power. Comparing how a structure behaves across T1, T2 and fat-suppressed images lets the radiologist work out what a change actually is — for instance whether a bright area in a vertebra is harmless fat, a fresh fracture, an infection or a tumour. This cross-checking between sequences is central to reaching an accurate spinal diagnosis, and it is why the report may refer to findings "on T2" or "on STIR."

• —Royal College of Radiologists — iRefer: Making the Best Use of Clinical Radiology
• —MHRA — Safety Guidelines for Magnetic Resonance Imaging Equipment in Clinical Use
• —British Association of Spine Surgeons (BASS)

This information is for general patient education and is not a substitute for an individual consultation. Always seek personalised advice from a qualified spinal specialist.