Cardiac iron overload protocol (MRI)

The cardiac MRI iron overload protocol encompasses a set of different MRI sequences for the cardiac assessment in case of suspected iron overload cardiomyopathy.

Note: This article aims to frame a general concept of a cardiac MRI protocol in the above setting.

Protocol specifics will vary depending on additional clinical questions, differential diagnosis, MRI scanner type, specific hardware and software, radiologist and perhaps referrer preference, patient factors e.g. arrhythmia or breathing problems or implants, specific indications and time constraints.

Indications

• iron overload cardiomyopathy

1.5 vs 3 tesla

The mainstay for the assessment of iron overload is T2* mapping this should currently performed at 1.5 tesla.

Patient preparation

Checking indications, contraindications, explanation of the examination and obtaining informed consent is obvious as in other examinations.

Beyond that patient preparation for cardiac MRI includes the following:

• instruction how to breathe
• an electrocardiogram signal need to be acquired

Patient positioning

A cardiac MRI is conducted in the supine position.

Technical parameters

Coil

Multi-phased-array coils are recommended.

• anterior surface coil, posterior coil
• cardiac coil

Scan geometry

• in-plane spatial resolution: will vary with the sequence
• field of view (FOV):  will vary, for most planes a FOV ≤320 mm is recommended
• slice thickness: varies with the sequence and is usually 6-10 mm

Planning

The cardiac imaging planes differ from the normal axial, coronal and sagittal body planes :

• overview
  • angulation: strictly axial
  • volume: from the thoracic inlet to the diaphragm
•  ​horizontal long axis view or 4-chamber view (4ch)
  • angulation: along the left ventricular long axis through the apex and the centers of the mitral and tricuspid valves
• left ventricular vertical long axis view or 2-chamber view (2ch)
  • angulation: along the left ventricular long axis through the left ventricular apex and the center of the mitral valve
• sagittal left ventricular outflow tract (LVOT) or 3-chamber view (3ch)
  • angulation: through the left ventricular apex,  the center of the mitral valve and the left ventricular outflow tract and aortic valve
• short-axis view (sax)
  • angulation: perpendicular to the left ventricular long axis

Sequences

Standard sequences

• T2 black-blood or SSFP
  • purpose: overview, depiction of the cardiac surroundings and greats vessels, assessment of mediastinal lymphadenopathy in suspected sarcoidosis
  • technique: T1 black-blood, T2 black-blood, SSFP ideally over 1-2 breath-holds
  • planes: axial
• cine imaging
  • purpose: left ventricular wall motion, left ventricular volumetry
  • technique: cine SSFP or spoiled GRE
  • planes: 2ch, 4ch, 3ch and short-axis views
• T2* mapping
  • purpose: cardiac tissue characterization (iron overload)
  • technique: single breath-hold GRE, multi-echo with 8 equally distributed echo times
  • planes: short-axis views

Optional sequences

• late gadolinium enhancement (C+)
  • purpose: for the evaluation of myocardial viability (myocardial necrosis, myocardial fibrosis and myocardial scar tissue)
  • technique: 2D and 3D IR GRE, PSIR
  • planes: 2ch, 4ch, 3ch and short-axis views
  • inversion time (TI) as determined by TI scout (Look-Locker) or fixed TI (PSIR)

(*) indicates optional planes, sequences or modules

Practical points

The following considerations can be made in certain conditions:

• single shot modules or free breathing with real-time image acquisition in patients with difficulties to hold their breath
• abdominal bands in profound respiratory motion
• peripheral pulse gating in patients with a weak ECG signal
• postponing the exam in patients with severe pleural effusion and related ghosting artefacts and breathing problems until after pleural drainage
• cine imaging
  • cardiac volumes should be obtained as in every cardiac MRI
• late gadolinium enhancement
  • should be performed in case of decreased ejection fraction