Spine and Pelvis
29 Thoracic Spine
Anatomy & Pathology
Anatomy and Key Landmarks
- Vertebral body
- Vertebral arch (pedicles, laminae)
- Vertebral foramen and canal
- Spinous processes (long, inferiorly angled)
- Transverse processes
- Superior and inferior articular processes
- Zygapophyseal (facet) joints
- Intervertebral disks and foramina
- Costal facets and demifacets on vertebral bodies (T1–T12 pattern varies)
- Costotransverse facets (T1–T10)
- Costovertebral joints (rib head to body facet/demifacet)
- Cervicothoracic junction (C7–T1)
Common Pathology
- Osteophytes and spondylosis
- Compression fractures (osteoporosis, trauma)
- Scheuermann disease (juvenile kyphosis)
- Scoliosis and kyphotic deformity
- Metastatic disease
- Costovertebral arthritis
Projections
AP Thoracic Spine
CR Location & Positioning
- SID: 40 inches (102 cm) unless protocol differs
- Patient position: Supine or upright AP; shoulders level; arms at sides
- Adjustments: Flex hips and knees if supine to reduce kyphosis; center MSP to IR; place top of IR 1.5–2 inches (4–5 cm) above shoulders to include T1–T12; use anode-heel effect or compensating filter for uniform density
- CR: Perpendicular to T7, midline, about halfway between jugular notch and xiphoid
- Pt. Instructions: Suspend on expiration or use shallow breathing per protocol
- Exposure: Tight collimation; grid; technique to penetrate upper chest and not burn out lower thorax
Evaluation Criteria
- Coverage (what anatomy must be included and how you verify it’s complete): All 12 thoracic vertebrae centered; T1 through T12 visible or documented with additional view if needed
- Rotation checks (how symmetry or alignment tells you if positioning is correct): Spinous processes midline; SC joints equidistant to spine; vertebral column centered on image
- Motion checks (how sharpness confirms patient cooperation/exposure timing): Sharp endplates and pedicles; no breathing motion unless intentional shallow breathing used
- Technique checks (what contrast density, soft tissue visibility, and artifacts to look for): Uniform brightness from upper to lower T-spine (filter/heel effect); clear bony detail; minimal scatter
- Clinical aim (when applicable): Survey alignment, compression deformities, costovertebral relationships, hardware follow-up
Lateral Thoracic Spine
CR Location & Positioning
- SID: 40–48 inches (increase SID to reduce magnification if possible)
- Patient position: Left lateral preferred (heart closer to IR) recumbent or upright
- Adjustments: Pillow to keep spine horizontal; flex hips/knees; arms at 90° to body to clear ribs; center posterior half of thorax at T7; elevate waist to open disk spaces; place lead strip posterior to absorb scatter
- CR: Perpendicular to T7, posterior half of thorax; angle 10° cephalad (average female) or 15° (average male) only if spine not horizontal
- Pt. Instructions: Suspend on expiration or use gentle breathing technique with long exposure if immobilized
- Exposure: Tight collimation; long exposure/low mA for breathing technique; grid
Evaluation Criteria
- Coverage: T1–T12 centered; note that T1–T3 may be obscured by shoulders and may require swimmer’s
- Rotation checks: Posterior ribs superimposed; vertebral bodies in true lateral profile
- Motion checks: Sharp vertebral margins; if breathing technique used, ribs and lung markings blurred while vertebrae remain sharp
- Technique checks: Open intervertebral disk spaces (waist support effective); adequate penetration through shoulders and lower thorax; reduced posterior scatter (lead strip)
- Clinical aim: Show intervertebral foramina, disk spaces, and vertebral alignment; assess compression fractures and canal caliber indirectly
Cervicothoracic Lateral (Swimmer’s, Twining)
CR Location & Positioning
- SID: 60–72 inches preferred
- Patient position: Lateral (upright preferred or recumbent)
- Adjustments: Raise arm nearest IR above head; depress far shoulder (weight if safe); head in true lateral; MSP parallel to IR
- CR: Perpendicular to C7–T1 (about 2 inches above jugular notch); 3–5° caudal if far shoulder cannot depress
- Pt. Instructions: Suspend breathing; remain still
- Exposure: Compensating filter recommended; grid; short time or controlled breathing only if immobilized
Evaluation Criteria
- Coverage: C5 through at least T3 with C7–T1 clearly demonstrated
- Rotation checks: Humeral heads separated anteroposteriorly and minimally superimposed on spine; vertebral bodies in true lateral
- Motion checks: Sharp vertebral outlines despite shoulder density
- Technique checks: Sufficient penetration between shoulders; visible disk spaces at C7–T1
- Clinical aim: Visualize the CT junction when standard lateral T-spine or cervical lateral does not demonstrate C7–T1
Thoracic Zygapophyseal Joints (Obliques)
CR Location & Positioning
- SID: 40 inches (or department standard)
- Patient position: PA oblique (RAO/LAO) or AP oblique (RPO/LPO) upright or recumbent
- Adjustments: Rotate body 20° from lateral so the coronal plane is 70° to IR; center spine to IR; top of IR 1.5–2 inches (4–5 cm) above shoulders to center at T7; arm positions to avoid humeral superimposition per approach
- CR: Perpendicular to T7, centered to spine
- Pt. Instructions: Suspend on expiration
- Exposure: Tight 7 × 17 inch (18 × 43 cm) collimation; grid
Evaluation Criteria
- Coverage: All 12 thoracic levels demonstrated across the series with joints visualized
- Rotation checks: Zygapophyseal joints nearest the IR open on PA obliques; joints farthest from IR open on AP obliques
- Motion checks: Joint margins crisp without breathing blur
- Technique checks: Adequate contrast to see joint spaces and articular processes; soft tissue detail present
- Clinical aim: Direct evaluation of facet (zygapophyseal) joints for arthropathy, subluxation, or postoperative assessment
Hows & Whys of Thoracic Spine Radiography
Anatomy
- Which thoracic features create rib articulations?
Costal facets or demifacets on vertebral bodies for rib heads and costotransverse facets (T1–T10) for rib tubercles. - Which joints allow rib gliding with respiration?
Costovertebral and costotransverse joints are synovial gliding joints. - Which normal curvature characterizes the thoracic spine?
A kyphotic (primary) curve concave anteriorly.
Positioning
- Why flex hips and knees for the AP thoracic spine?
To reduce thoracic kyphosis so the spine lies closer to the IR, improving alignment and uniform exposure. - Why use the anode-heel effect or a compensating filter on the AP?
To even out density from the thinner upper thorax to the thicker lower thorax so all vertebrae display similar brightness. - Why place a lead strip posterior to the patient on the lateral?
To absorb scatter exiting the patient and table, improving contrast and preventing premature AEC termination. - Why elevate the waist on the lateral?
To make the spine horizontal and open intervertebral disk spaces rather than closing them with a sagging torso. - Why consider a breathing technique for the lateral?
To blur ribs and lung markings while keeping vertebrae sharp, improving visualization of the thoracic spine. - Why perform a swimmer’s view for the thoracic series?
To demonstrate the obscured upper thoracic segments and the C7–T1 junction when shoulder superimposition hides them. - Why rotate 20° from lateral (70° to IR) for obliques?
Because thoracic zygapophyseal joints open best at ~70°; PA shows joints closest to the IR, AP shows joints farthest.
Technique & Image Evaluation
- How can you tell AP positioning and beam centering were correct?
All 12 vertebrae are included and centered; spinous processes are midline; density is uniform superior to inferior. - How can you tell the lateral is a true lateral?
Posterior ribs are superimposed; vertebral bodies are in profile; disk spaces are open with proper waist support. - How can you tell a breathing technique worked on the lateral?
Ribs and lung markings are blurred, but the vertebral bodies, pedicles, and endplates remain sharp. - How can you tell swimmer’s positioning is adequate?
C7–T1 disk space is seen; humeral heads are offset (one anterior, one posterior) with minimal overlap on the vertebral column. - How can you tell the obliques are at the correct angle?
Target zygapophyseal joints are uniformly open along the length imaged with clear articular margins.
Clinical Applications
- When would you add obliques to a thoracic series?
When facet arthropathy, suspected subluxation, or postoperative facet assessment is indicated. - When should CT or MRI supplement radiographs?
When acute trauma requires fracture detail (CT) or when neurologic symptoms suggest cord/soft-tissue pathology (MRI).
