Anatomy

• What is lordosis?
  Lordosis refers to the normal inward curvature of the lumbar spine. When this curve becomes exaggerated, it is known as hyperlordosis and may cause postural or alignment issues.
• What does the “Scotty Dog” represent on an oblique image of the lumbar spine?
  The Scotty Dog appearance is created by the alignment of bony landmarks on oblique lumbar images, used to identify normal anatomy and detect pathology such as spondylolysis.
• What anatomical structure forms the “eye” of the Scotty Dog?
  The pedicle forms the eye of the Scotty Dog. Its position helps assess correct obliquity — if it moves anteriorly, the patient is under-rotated; if posteriorly, over-rotated.
• What anatomical structure forms the “neck” of the Scotty Dog?
  The pars interarticularis forms the neck of the Scotty Dog. A fracture through this region represents spondylolysis.
• What anatomical structure forms the “ear” of the Scotty Dog?
  The superior articular process forms the ear.
• What anatomical structure forms the “nose” of the Scotty Dog?
  The transverse process forms the nose.
• What anatomical structure forms the “front leg” of the Scotty Dog?
  The inferior articular process forms the front leg.
• What anatomical structure forms the “body” of the Scotty Dog?
  The lamina forms the body of the Scotty Dog.
• Which portion of the lumbar vertebra is most prone to spondylolysis?
  The pars interarticularis is the weakest portion and subject to stress fractures.
• Which landmark corresponds to the level of L4?
  The highest point of the iliac crest aligns with the level of L4.
• What structure forms the intervertebral foramen?
  The superior and inferior vertebral notches of adjacent vertebrae form the intervertebral foramen.

Positioning

• Why are the hips and knees flexed for the AP projection?
  Flexing the hips and knees flattens the lumbar curve and opens the intervertebral disk spaces.
• Why is the midsagittal plane centered to the midline of the IR for the AP projection?
  Centering ensures both SI joints are equidistant from the spine, preventing rotation that can mimic pathology.
• Why should the exposure be made at the end of expiration?
  Suspending respiration at the end of expiration elevates the diaphragm, removing aerated lung from the upper lumbar region and producing more uniform contrast across the spine.
• Why is a support placed under the waist for the lateral projection?
  A support aligns the spine horizontally, preventing closed disk spaces from sagging.
• Why is the central ray angled caudally for the L5–S1 spot?
  The angulation aligns the beam parallel to the joint space to open the lumbosacral disk.
• Why are posterior obliques performed at 45°?
  This degree places the zygapophyseal joints parallel to the image receptor for optimal visualization.

Technique & Image Evaluation

• How can you tell the AP image is not rotated?
  The spinous processes are centered, and the sacroiliac joints are equidistant from the midline.
• How can you tell if the lumbar spine is rotated on the AP image?
  Rotation is evident if the spinous processes are not centered within the vertebral bodies or if the SI joints are asymmetric.
• How can you tell if the lumbar spine is in true lateral on the lateral image?
  Posterior vertebral borders and iliac crests appear nearly superimposed.
• How can you tell if the technique is appropriate?
  Adequate kVp and mAs produce visualization of soft tissue and bony detail without overexposure of the spinous processes or underexposure of the vertebral bodies.
• How can you tell the obliquity was correct on the oblique projection?
  The pedicle (Scottie dog’s eye) is centered within the vertebral body; anterior or posterior shift indicates incorrect rotation.
• How can you verify exposure and contrast on a lumbar image?
  Bone and soft tissue are both visible, with clear trabecular detail and no burnout in vertebral bodies.

Clinical Applications

• Why is the AP projection preferred for routine lumbar imaging?
  It provides consistent visualization of the lumbar vertebrae with minimal patient strain.
• Why is the lateral L5–S1 spot essential in some studies?
  It isolates the lumbosacral joint space where disk disease or spondylolisthesis frequently occur.
• Why are obliques useful in evaluating back pain?
  They demonstrate facet joints and pars defects often responsible for chronic pain syndromes.