Alpha Angle Measurement by CT

Purpose	An automated method for alpha angle measurement to assist in the determination of femoroacetabular impingement
Tag(s)	#FAI, #alpha angle, #CT
Panel	Musculoskeletal Panel
Define-AI ID	19050028
Originator	Martin Torriani
Lead	Martin Torriani
Panel Chair	Jay Patti
Panel Reviewers	Musculoskeletal Panel
License	Creative Commons 4.0
Status	Public Commenting
RadElement Set	RDES119

                               

Value Proposition

Femoroacetabular impingement (FAI) is an entity in which abnormal osseous morphology of the femoral neck (CAM FAI) or acetabulum (pincer FAI) may cause osseous impact that leads to fibrocartilage (labrum) tears, cartilage loss, early degenerative changes and pain. Using multiplanar reformatted images, hip CT protocols can produce images that allow for detection of CAM FAI, however the measurement process is laborious and may present intra- and inter-observer variability. AI meeting this use case would help to make these measures more efficient and improve patient care by providing an initial assessment on the potential presence of CAM FAI.

Narrative(s)

A 30-year-old patient presents for hip CT due to pain. An algorithm evaluates the image and may also compare this exam with multiple prior exams. The algorithm detects if alpha angle is abnormal (> 55 degrees) to assist the radiologists in the interpretation and raise the possibility of FAI.

Workflow Description

Identification of appropriate pulse sequence containing oblique axial images.Identification of best oblique axial image on which to perform measures. Placement of measurement calipers on axial image. Output of alpha angle.

Procedures(s)	{CT Hip}
View(s)	{Dedicated oblique axial}
Sex at Birth	{Male, Female}
Age	[18-50]

Inputs

DICOM Study

 

Procedure	CT Hip
Views	Dedicated oblique axial
Data Type	DICOM
Modality	CT
Body Region	Lower Extremity
Anatomic Focus	Hip

Primary Outputs

 

Alpha Angle

RadElement ID	RDE775
Definition	Alpha angle
Data Type	Numeric
Value Set	N/A
Units	Degrees

• FAI can be of pincer type and would require measures of excessive acetabular coverage, which could be performed.
• Recent studies show that CAM FAI may require assessment of alpha angle on multiple images, which could require a 3D acquisition of the hip for this purpose.
• Dedicated Use Case for FAI or alpha angle on radiographs.
  
  

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