Main Content
Alpha Angle Measurement By MRI
| Purpose | An automated method for alpha angle measurement to assist in the determination of femoroacetabular impingement |
| Tag(s) | #FAI, #alpha angle, #MRI |
| Panel | Musculoskeletal Panel |
| Define-AI ID | 19050022 |
| Originator | Martin Torriani |
| Lead | Martin Torriani |
| Panel Chair | Jay Patti |
| Panel Reviewers | Musculoskeletal Panel |
| License | Creative Commons 4.0 |
| Status | Public Commenting |
| RadElement Set | RDES110 |
Clinical Implementation
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. Many routine hip MRI protocols include imaging in a dedicated oblique-axial plane that is necessary for measurement of specific angles 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 MRI 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.
Considerations for Dataset Development
| Procedures(s) | {MRI, Hip} |
| View(s) | {Dedicated oblique axial} |
| Sex at Birth | {Male, Female} |
| Age | [18-50] |
Technical Specifications
Inputs
DICOM Study
| Procedure | MRI Hip |
| Views | Dedicated oblique axial |
| Data Type | DICOM |
| Modality | MRI |
| Body Region | Lower Extremity |
| Anatomic Focus | Hip |
Primary Outputs
Alpha Angle
| RadElement ID | RDE702 |
| Definition | Alpha angle |
| Data Type | Numeric |
| Value Set | N/A |
| Units | Degrees |
Future Development Ideas
- FAI can be of pincer type and would require measures of excessive acetabular coverage, which could be performed. In addition, 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.
Related Datasets
No known related public datasets at this time, please alert us if you know of any.