Cardiac MRI — suspected myocarditis
Full short-axis and long-axis cine coverage, with mapping and late enhancement across the same slices.
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
- Chest pain with raised troponin and unobstructed coronary arteries.
- New unexplained heart failure or arrhythmia with a suspected inflammatory cause.
- Suspected vaccine- or drug-associated myocarditis.
- Follow-up of proven myocarditis to document resolution before return to competitive activity.
- Suspected cardiac sarcoidosis, where the same tissue-characterisation toolkit applies.
Technique
- Tissue characterisation is the point: native T1 mapping, T2 mapping and/or T2-weighted oedema imaging, plus extracellular volume where haematocrit is available.
- Late gadolinium enhancement typically in a subepicardial or mid-wall distribution, imaged in two orthogonal planes to confirm.
- Cine imaging for regional wall motion abnormality and pericardial effusion.
- Mapping normal ranges are scanner- and sequence-specific; a value is meaningless without the local reference.
Where it goes wrong
- Relying on late enhancement alone and omitting oedema-sensitive mapping, which under-calls acute inflammation.
- Using published mapping thresholds from a different field strength or vendor.
- Scanning very late after the acute episode, when oedema has resolved and only residual scar remains — timing is part of the vetting decision.
- Poor gating in a tachycardic, unwell patient degrading exactly the quantitative sequences the study depends on.
Contrast
Extracellular gadolinium agent at a typical dose of about 0.1-0.2 mmol/kg, with late enhancement imaging after a delay of roughly 10-15 minutes.
Acquisition
- Breathing
- ECG-gated breath-hold acquisitions.
- 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