A versatile and fast general protocol which can be used for any knee case unless otherwise specified on request. The basic Harrogate knee scan uses uniquely intermediate weighted sequences to focus on cartilage based pathologies, accepting that a small number of recalls and protocol redesigns will be required for other findings.
Patellofemoral tracking studies contain a standard knee and additional dynamic patellofemoral sequences.
Positioning
Knee either fully extended or 5 degrees flexed for comfort. The patella must point towards the sky. The knee must be placed as close to the isocentre as possible.
Scan
- Knee coil
- Base FOV 15cm ± 1cm depending on patient size
- Sagittal oblique aligned to the plane of the ACL based on using the external surface of the anterolateral femoral condyle as an angle guide
| Sequence | TE / TR | Slice / Gap / Matrix | Other |
|---|---|---|---|
| PDFS Axial | 32 / 3300 | 3mm / 0.5mm / 270x384 | Weak FS, Avg1 GRAPPA 2, Interpolate |
| PD Sagittal Oblique | 32 / 3300 | 3mm / 0.4mm / 384 x 512 | Avg1 GRAPPA 2, Interpolate |
| PDFS Sagittal Oblique | 32 / 3300 | 3mm / 0.5mm / 384 x 512 | Weak FS, Avg1 GRAPPA 2, Interpolate |
| T2FS Coronal | 40 / 4000 | 3mm / 0.5mm / 270x384 | Weak FS, Avg1 GRAPPA 2, Interpolate |
| PDFS Coronal | 20 / 2500 | 3mm / 0.5mm / 270x384 | Avg1 GRAPPA 2, Interpolate |
Variants
Suspected infection or bone tumour
| Sequence |
|---|
| T2FS Axial |
| T1 Sagittal Oblique |
| T2FS Sagittal Oblique |
| T1 Coronal |
| STIR Coronal |
Coping with metal work
- Increase slice thickness to 4mm
- Increase slice gap to 20%
- Use higher bandwidth STIR or PDFS sequences
- Use MARS algorithms (such as SEMAC)
Difficulty seeing the ACL
- Recall patient for additional sequences
- Coronal oblique angled to pitch of ACL across notch
- Repeat sagittal oblique sequences with different angle
- Ask MSK radiologist to review images on scanner before completion