On MRI of the knee, the anterior cruciate ligament (ACL) is evaluated on which sequence and orientation MOST accurately?
- A Axial T2 fat-saturated sequence
- B Coronal STIR sequence
- C Sagittal T1 or PD (proton density) sequence oblique to the ACL ✓
- D Axial gradient-echo sequence
Correct answer: C. Sagittal T1 or PD (proton density) sequence oblique to the ACL
Explanation
The ACL is best visualized on sagittal oblique sequences oriented parallel to the ACL fibers (typically angled 15-20 degrees lateral to the sagittal plane) using T1 or proton-density fat-saturated sequences. This orientation shows the ACL as a band of low signal running from the tibial intercondylar eminence to the lateral femoral condyle. Coronal STIR is useful for bone marrow edema (pivot shift pattern) but not optimal for ACL. Axial T2 FS shows the ACL in cross-section. Gradient-echo is susceptibility-weighted and not the primary ACL sequence.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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