Cardiac MRI — function and late gadolinium enhancement
Short-axis stack covering both ventricles from base to apex, plus two-, three- and four-chamber long-axis views.
Timings, volumes and delays here are representative values drawn from published guidance. Scanner generation, injector, cardiac output and local preference all move them. Confirm against your department's own protocol before you rely on a number.
When to use it
- Cardiomyopathy work-up where the pattern of fibrosis distinguishes ischaemic from non-ischaemic aetiology.
- Viability assessment before revascularisation, where transmural extent of scar predicts functional recovery.
- Accurate ventricular volumes and ejection fraction when echocardiography is limited or discordant, including before device implantation.
- Suspected infiltrative disease such as amyloid, sarcoid or iron overload.
- Hypertrophic cardiomyopathy risk assessment and assessment of arrhythmogenic cardiomyopathy.
Technique
- Balanced steady-state free precession cines in short-axis and long-axis planes, with slice thickness and gap chosen so the whole ventricle is covered without omission.
- Late gadolinium enhancement with a segmented inversion-recovery gradient-echo sequence, inversion time set by a Look-Locker or TI-scout to null normal myocardium; phase-sensitive reconstruction reduces sensitivity to a mis-set inversion time.
- Native and post-contrast T1 mapping and T2 mapping where tissue characterisation beyond focal scar is needed; T2* for iron.
- Cross-cut long-axis views should be repeated to confirm any focal enhancement in two planes.
Where it goes wrong
- Inversion time set incorrectly, which either hides subendocardial scar or creates artefactual bright myocardium.
- Imaging late enhancement too early after injection, when blood pool and myocardium have not separated.
- Arrhythmia or poor gating blurring the cines, making volumes and ejection fraction unreliable — atrial fibrillation should be known before booking.
- Basal slice mis-selection causing systematic over- or under-estimation of ventricular volume.
- Mapping values compared across scanners, field strengths or sequences without local reference ranges.
Contrast
Extracellular gadolinium agent at a typical dose of about 0.1-0.2 mmol/kg depending on agent and on whether mapping is included; late enhancement imaging conventionally begins around 10-15 minutes after injection.
- Where extracellular volume is being calculated, pre- and post-contrast T1 maps must be acquired with the same sequence and a same-day haematocrit.
Acquisition
- Breathing
- End-expiratory breath-holds of roughly 8-15 seconds per acquisition, ECG gated. Free-breathing motion-corrected alternatives exist for patients who cannot comply.
- Reconstruction
- Ventricular volumes and mass from the short-axis cine stack; enhancement quantified against remote myocardium.
- Preparation
- Breath-hold capacity and rhythm are the two determinants of study quality: state atrial fibrillation, frequent ectopy or inability to hold breath. Cardiac devices are common in this population; establish conditionality, generator model and local device-scanning arrangements before booking rather than at the scanner. For stress perfusion, withhold caffeine for the locally specified interval and check for reactive airways disease before adenosine or regadenoson.
Phases
Each phase is authored once and shared across every protocol that uses it, so the physiology below is the same wherever you meet it.
- Non-contrast (unenhanced)No injection. Acquired before any contrast is given.
Shows intrinsic tissue attenuation, and nothing else. The transferable principle is that contrast is anti-signal for anything that is already dense: calcification, acute haemorrhage, urinary and biliary calculi, iodine-containing or haemorrhagic fluid, and intrinsic fat all lose conspicuity, or become uninterpretable, once surrounding tissue enhances. It is also the only baseline against which enhancement can be measured, so any protocol that quantifies enhancement or washout (a lesion "enhances by X HU", adrenal absolute washout, renal mass characterisation) is arithmetically impossible without it. Conversely, an unenhanced series adds dose and no information whenever the question is purely about vascularity or perfusion.
- Delayed / equilibrium (washout) phaseQuestion-dependent: ~3–5 min for hepatic equilibrium/washout, ~15 min for adrenal absolute-washout calculations. Confirm locally.
Intravascular and interstitial compartments have equilibrated and contrast is being cleared, so most normal tissue is falling in attenuation. The transferable principle is that the diagnostic information is now in the RATE OF CHANGE rather than in the absolute density: tissues with rapid capillary exchange and a small interstitium wash out quickly, whereas fibrous, myxoid or otherwise expanded interstitial spaces retain contrast and become relatively dense. That single mechanism underlies delayed enhancement of scar and fibrosis, retained enhancement in cholangiocarcinoma and haemangioma fill-in, and the arithmetic of adrenal washout — all of which require a matched earlier acquisition to be interpretable at all.
Safety checks this protocol carries
Derived from the contrast agent and phases above, not authored here — which is why they cannot drift apart from what the protocol actually does.
- Prior contrast reaction and elective premedication· nurse pre scan
- Kidney function and gadolinium-based contrast· radiographer at scan
- Intravenous access adequate for the planned injection· radiographer at scan
- Metformin and iodinated contrast· radiographer at scan
- MR safety screening for implants and foreign bodies· radiographer at scan
- Sedation or anaesthesia for a child· nurse pre scan
- Kidney function and intravenous iodinated contrast· radiographer at scan