Spine and Pelvis
Thoracic Spine
Anatomy
Students should be able to identify the following structures on radiographic images:
body, vertebral arch, vertebral foramen, intervertebral disks, transverse processes, spinous process, laminae, pedicle, superior articular process, inferior articular process, zygapophyseal joints (AKA. apophyseal jts. or interarticular facet joints), facet or demifacet, costovertebral joint, costotransverse joints, intervertebral foramina.
Routine Projections (ARRT Required)
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
Supplemental Projections
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).
