MRI MRI Anatomy and Positioning 2 — Questions and Answers
Question 1: Which coil type provides the highest signal-to-noise ratio (SNR) for imaging small superficial structures such as the wrist?
- Body coil
- Head coil
- Dedicated extremity or surface coil (Correct answer)
- Phased-array spine coil
Correct answer: Dedicated extremity or surface coil
Dedicated extremity or surface coils placed close to the anatomy maximize SNR by minimizing the receive volume to the region of interest.
Question 2: The 'magic angle' artifact in MRI tendons occurs at approximately what angle relative to the main magnetic field?
- 15°
- 30°
- 45°
- 55° (Correct answer)
Correct answer: 55°
Magic angle artifact occurs when a tendon is oriented at approximately 55° (the magic angle) to B0, causing artificial T1/PD signal increase that can mimic pathology.
Question 3: For pituitary gland MRI, which plane is considered the primary imaging plane?
- Axial
- Sagittal
- Coronal (Correct answer)
- Oblique axial
Correct answer: Coronal
Coronal thin-slice images are the primary plane for pituitary imaging because they best demonstrate lateral extension, cavernous sinus invasion, and microadenomas.
Question 4: Which positioning aid is used to maintain the ankle in a 90° neutral position during MRI to optimally visualize the Achilles tendon?
- Sand bag
- Vacuum immobilization device
- Ankle positioning block or foam wedge (Correct answer)
- Compression bandage
Correct answer: Ankle positioning block or foam wedge
A foam wedge or ankle block holds the foot perpendicular to the leg, minimizing magic angle artifact and providing consistent Achilles tendon orientation.
Question 5: On a sagittal MRI of the cervical spine, the posterior longitudinal ligament appears as a thin structure along which surface of the vertebral bodies?
- Anterior
- Posterior (Correct answer)
- Lateral
- Superior
Correct answer: Posterior
The posterior longitudinal ligament runs along the posterior surfaces of the vertebral bodies inside the spinal canal, anterior to the thecal sac.
Question 6: When performing MR arthrography of the hip, the patient is typically positioned with the hip in which orientation?
- 30° internal rotation
- Neutral or slight internal rotation (Correct answer)
- Maximum external rotation
- Frog-leg lateral position
Correct answer: Neutral or slight internal rotation
Neutral to slight internal rotation during hip MR arthrography places the femoral neck parallel to the imaging plane and optimizes labral visualization.
MRI MRI Anatomy and Positioning 2
Which coil type provides the highest signal-to-noise ratio (SNR) for imaging small superficial structures such as the wrist?