Anterior chest wall protocol (MRI)

The MRI anterior chest wall protocol encompasses a set of MRI sequences for the routine assessment of the sternoclavicular joints and/or the anterior chest wall.

Note: This article aims to frame a general concept of an MRI protocol for the assessment of sternoclavicular joints and/or the anterior chest wall. Protocol specifics will vary depending on MRI scanner type, specific hardware and software, radiologist and perhaps referrer preference, patient factors e.g. implants, specific indications and time constraints.

Indications

First-class indications are suspected disorders of the sternoclavicular joints. The protocol can be adjusted for the assessment of sternal tumors or other processes of the anterior chest wall.

1.5 vs 3 tesla

An MRI examination of the sternoclavicular joints can generally be performed on both 1.5 and 3 tesla.

Patient positioning

An MRI of the sternoclavicular joints can be conducted with the patient in a prone or supine position.

The examination in the prone position reduces motion artifacts .

Technical parameters

Coil

Multi-phased-array coils are recommended. The size of the coil depends on the area of interest.

• anterior surface coil, medium flexible coil
• posterior coil

Scan geometry

• in-plane spatial resolution: ≤0.4 x 0.4 mm
• field of view (FOV):  240-300 mm, as small as possible
• slice thickness: ≤3 mm

Planning

• coronal images:             
  • angulation: perpendicular to the sternum and anterior chest wall
  • volume: from the presternal skin, including the whole sternum and both sternoclavicular joints
  • slice thickness: ≤3 mm
• axial images:
  • angulation: perpendicular to the sternum and anterior chest wall
  • volume:  the depends on the pathology
  • slice thickness: ≤3 mm
• sagittal images:
  • angulation: strictly sagittal to the body axis 
  • volume:  depends on the pathology
  • slice thickness: ≤3 mm

Sequences

Sequences can be adjusted in respect to scanner specifications, and image quality in particular sequences. As with other musculoskeletal imaging water-sensitive sequences are an integral component, as STIR, fat-saturated T2 weighted or intermediate-weighted images. At least one T1-weighted sequence should be included.

Standard sequences

A typical MRI of the sternoclavicular joints or anterior chest wall might look like as follows :

• fat-saturated intermediate, T2-weighted or STIR
  • purpose: articular discs, bone marrow edema, inflammation
  • technique:  IM FS fast spin echo / T2 FS fast spin echo / STIR
  • planes: coronal, axial
• T1-weighted
  • purpose: bone and/or soft-tissue characterization
  • technique:  T1 fast spin echo
  • planes: coronal

Optional sequences

• T2-weighted
  • purpose: bone and soft tissue characterization, tumors
  • technique: T2 fast spin echo, T2 Dixon
  • planes: sagittal * (option for tumors)
• T1-weighted C+ (fat-saturated)
  • purpose: for the assessment of synovitis or osteitis
  • technique:  T1 fast spin echo
  • planes: coronal, axial

(*) indicates optional planes

Practical points

• a typical protocol will consist of 3-5 sequences, depending on if contrast is given or not
• an alternative to intermediate-weighted (fat-saturated) sequences would be a T2-weighted or proton density-weighted Dixon variant, which includes a fluid sensitive fat-saturated and a non-fat-saturated image stack
• likewise, the protocol can be supplemented with diffusion-weighted imaging (DWI) for the assessment of tumors or chest wall invasion
• for the assessment of the sternoclavicular articular disks preferably fat-saturated intermediate-weighted images should be acquired, for the general assessment of inflammatory lesions or other indications as tumors fat-saturated T2 weighted images or STIR images are preferred