Radiography Exam Anatomy and Pathology for Radiographers 2 — Questions and Answers
Question 1: On a standard AP pelvis radiograph, the normal radiographic 'teardrop' (U-figure) represents:
- The medial wall of the acetabulum and the floor of the acetabular fossa (Correct answer)
- The lesser trochanter of the femur
- The obturator foramen
- The sacroiliac joint space
Correct answer: The medial wall of the acetabulum and the floor of the acetabular fossa
The radiographic 'teardrop' (Kohler's teardrop figure) on AP pelvis radiography represents the medial wall and floor of the acetabulum, and is used to assess for medial displacement in acetabular fractures.
Kohler's teardrop is a U-shaped density on AP pelvis radiographs formed by the intersection of: the medial acetabular wall (outer limb), the acetabular fossa floor (inner limb), and the obturator sulcus (connecting the two). It is used to assess medial protrusion (protrusio acetabuli) in hip osteoarthritis and rheumatoid arthritis. Medial displacement of the femoral head relative to the teardrop indicates protrusio acetabuli. Disruption of the teardrop suggests acetabular fracture (central fracture-dislocation).
Question 2: Which pathological finding on a chest radiograph is most consistent with a tension pneumothorax?
- Tracheal and mediastinal shift away from the side of the pneumothorax with lung collapse (Correct answer)
- Pleural effusion with blunted costophrenic angle
- Bilateral interstitial edema with Kerley B lines
- Unilateral hilar enlargement
Correct answer: Tracheal and mediastinal shift away from the side of the pneumothorax with lung collapse
In tension pneumothorax, rising intrapleural pressure displaces the mediastinum and trachea away from the affected side, compresses the contralateral lung, and impairs venous return — a life-threatening emergency.
Tension pneumothorax occurs when a one-way valve mechanism allows air to enter the pleural space but not escape. Signs on CXR: (1) complete lung collapse on affected side, (2) trachea and mediastinal shift AWAY from the pneumothorax, (3) depression (flattening/inversion) of the ipsilateral hemidiaphragm, (4) widened intercostal spaces on affected side. This is a clinical diagnosis requiring immediate needle decompression — imaging should not delay treatment if clinically suspected.
Question 3: The 'boot-shaped heart' (coeur en sabot) appearance on a plain chest radiograph is classically associated with which congenital heart disease?
- Tetralogy of Fallot (Correct answer)
- Transposition of the great arteries
- Atrial septal defect
- Patent ductus arteriosus
Correct answer: Tetralogy of Fallot
Tetralogy of Fallot produces the 'boot-shaped heart' on CXR: right ventricular hypertrophy lifts the apex, combined with a small pulmonary artery segment creates the characteristic appearance.
Tetralogy of Fallot (ToF) has four components: (1) VSD, (2) pulmonary stenosis/right ventricular outflow tract obstruction, (3) overriding aorta, (4) right ventricular hypertrophy. On CXR: boot-shaped heart = RVH elevates apex + concave pulmonary arterial segment (small PA). Lung fields are oligemic (decreased pulmonary vascularity) due to reduced pulmonary blood flow. ToF is the most common cyanotic congenital heart disease after age 1. Contrast to Transposition of Great Arteries: egg-on-side heart, increased vascularity.
Question 4: Wrist radiographs in a patient with rheumatoid arthritis classically show which triad of findings?
- Periarticular osteoporosis, joint space narrowing, and marginal erosions (Correct answer)
- Osteophyte formation, subchondral sclerosis, and joint space narrowing
- Periosteal reaction, osteolysis, and soft tissue swelling
- Dense cortical bone, thick trabeculae, and subchondral cysts
Correct answer: Periarticular osteoporosis, joint space narrowing, and marginal erosions
Rheumatoid arthritis classically produces periarticular osteoporosis, uniform joint space narrowing (from pannus erosion of cartilage), and marginal bone erosions — differentiating it from osteoarthritis.
Rheumatoid arthritis (RA) radiographic findings: (1) Periarticular osteoporosis — juxta-articular bone density loss from hyperemia; (2) Symmetric joint space narrowing — pannus erodes cartilage uniformly; (3) Marginal erosions — 'naked area' erosions at cartilage edges; (4) Subluxations — ulnar deviation, boutonnière/swan neck deformities. Compare to osteoarthritis: non-inflammatory, asymmetric, osteophytes (bone spurs), subchondral sclerosis, subchondral cysts. RA involves the wrist/MCP/PIP joints; OA involves DIP/PIP/CMC joints.
Question 5: On a lateral cervical spine radiograph, the prevertebral soft tissue space at C3 normally measures no more than:
- 7 mm (or one-third the AP width of the adjacent vertebral body) (Correct answer)
- 20 mm
- 5 cm
- Equal to the vertebral body width
Correct answer: 7 mm (or one-third the AP width of the adjacent vertebral body)
The prevertebral soft tissue at the C3 level should be ≤7 mm (approximately one-third the width of the adjacent cervical vertebral body) on a standard lateral cervical spine radiograph.
Normal prevertebral soft tissue measurements on lateral cervical spine X-ray: C1-C4 ≤7 mm (one-third vertebral body width); C5-C7 ≤22 mm (vertebral body width). Widening indicates prevertebral hematoma (post-trauma), abscess, or cellulitis. A retropharyngeal hematoma can indicate significant cervical spine injury even with normal bone alignment. At C5-C7, the trachea creates normal soft tissue widening, so the threshold is higher. These measurements are critical in trauma evaluation.
Question 6: The 'Scotty dog' sign seen on oblique lumbar spine radiographs corresponds to which anatomical structures?
- The pedicle (eye), transverse process (nose), superior articular process (ear), pars interarticularis (neck), and inferior articular process (front leg) (Correct answer)
- The intervertebral disc (nose), vertebral body (head), and sacrum (tail)
- The spinous process (tail), lamina (body), and nerve root (leg)
- The costovertebral joint (eye) and rib (leg)
Correct answer: The pedicle (eye), transverse process (nose), superior articular process (ear), pars interarticularis (neck), and inferior articular process (front leg)
On oblique lumbar radiographs, the 'Scotty dog' silhouette is formed by: eye=pedicle, nose=transverse process, ear=superior articular process, neck=pars interarticularis, body=lamina, front leg=inferior articular process.
The Scotty dog anatomy on oblique lumbar spine: Head = transverse process and pedicle region; Eye = pedicle (seen end-on); Ear = superior articular process; Neck = pars interarticularis; Body = lamina; Fore leg = inferior articular process; Hind leg = opposite inferior articular process. A 'collar' on the Scotty dog (lucency through the neck/pars interarticularis) represents spondylolysis — a fatigue fracture of the pars. Bilateral spondylolysis can lead to spondylolisthesis (forward slippage of the vertebral body).
Radiography Exam Anatomy and Pathology for Radiographers 2
On a standard AP pelvis radiograph, the normal radiographic 'teardrop' (U-figure) represents: