CT elbow (protocol)

The CT elbow protocol serves as an examination for the bony assessment of the elbow and is usually performed as a non-contrast study. It can be also combined with a CT arthrogram for the evaluation of chondral and osteochondral injuries.

Note: This article aims to frame a general concept of a CT protocol for the assessment of the elbow. Protocol specifics will vary depending on CT scanner type, specific hardware and software, radiologist and perhaps referrer preference, patient factors e.g. implants, specific indications.

Contrast doses apply for CT examinations in adults.

A typical CT of the elbow might look like as follows:

Indications

Typical indications include the following ^1-5:

• elbow trauma
  • distal humeral fractures
  • proximal radial and ulnar fractures
  • elbow dislocation
  • coronoid process fractures/posteromedial instability
• elbow stiffness/osteoarthritis
• inflammatory or infectious processes
• bone and soft tissue tumours (if MRI is contraindicated)
• postoperative follow up, implants and their complications
• interventions (e.g. CT-guided biopsy)

Purpose

The purpose of an elbow CT in the setting of a traumatic injury or suspected fracture is their timely diagnosis as well as their classification and characterisation ^1,2.

In the setting of elbow stiffness, CT can demonstrate osteoarthritis, bony spurs, joint incongruency, loose bodies and ankylosis ³.

In the setting of inflammatory or neoplastic processes, the purpose of a CT pelvis is the localisation and characterisation of the respective process, its extent and its relation to the adjacent tissues as well as the detection of potential complications.

Technique

• patient position
  • supine position 
  • the arm in question is raised above the head
  • the affected elbow should be close to the centre of the scanning table
  • if possible elbow extended palm facing upwards
  • upper body and head bent to the contralateral side
  • contralateral arm next to the body
• tube voltage
  • ≤120 kVp
• tube current
  • as suggested by the automated current adjustment mode (≤150 mAs)
• scout
  • mid-upper arm to mid-forearm
• scan extent
  • including the humeral metaphysis and the proximal third of the ulna and radius
  • might vary depending on the indication
• scan direction
  • caudocranial
• scan geometry
  • field of view (FOV): ≤150 mm (should be adjusted to increase in-plane resolution)
  • slice thickness: ≤0.625 mm, interval: ≤0.3 mm
  • reconstruction kernel: bone kernel (e.g. I70), soft tissue kernel (e.g. I40)
• contrast injection considerations
  • non-contrast (e.g. fractures)
  • single acquisition with monophasic injection (venous)
    • contrast volume: 70-100ml with 30-40 mL saline chaser at 3-5 mL/s
    • scan delay: 45-60 seconds
• multiplanar reconstructions
  • sagittal images: perpendicular to the interepicondylar line aligned through the humerus and proximal ulna
  • coronal images: parallel to the interepicondylar line and the humeral shaft
  • axial images: parallel to the joint line from the capitulum and trochlea perpendicular to the humerus
  • additional multiplanar reformations on a bent elbow
    • axial images:perpendicular to the forearm
    • coronal images: parallel to the ulna and radius

Practical points

• patient positioning prior to scanning might reduce and facilitate multiplanar reconstructions
• reconstructions in both standard kernel and high-resolution kernels
• depending on the exact indication the scan might require an extension of the scan field
• dose optimisation ¹
  • use iterative reconstruction algorithms if available
• imaging of implants ¹
  • use metal artifact reduction algorithms
  • use monochromatic reconstructions in dual-energy CT scans
  • use additional wide window setting
  • might require a higher tube voltage