Lumbar Spine Radiography: Positioning and Technique

Written on March 17, 2026 in English with a size of 3.67 KB

AP Lumbar Spine Projection

IR: 14x17” LW
Position: Supine with knees flexed; MSP centered to IR. Alternatively, prone to place intervertebral disk spaces more parallel to the divergence of the beam.
CR: Perpendicular at the level of the iliac crest (L4). For 11x14 IR, center 1.5” above the iliac crest (L3).
Technique: 75–92 kV; 8–20 mAs. Higher kV with lower mAs reduces patient dose.
AEC: Center cell; collimate on all four borders.
SID: 40” minimum.
Respiration: Suspended on expiration.
Analysis: Vertebral bodies, pedicles, laminae, intervertebral joints, spinous and transverse processes clearly seen. No rotation is indicated by SI joints equidistant from spinous processes, spinous process in the midline of the vertebral column, and transverse processes of equal length. Optimal density and contrast to show bony detail and psoas muscles.

IR: 14x17” LW
Position: Left lateral recumbent; MCP perpendicular to IR.
CR: Perpendicular to the spine at the level of the iliac crest and MCP.
Technique: 90–100 kVp; 25–55 mAs.
AEC: Center cell.
SID: 40”.
Respiration: Expiration.
Analysis: T12–S1 vertebral bodies in profile; open intervertebral foramina and disk spaces. True lateral; iliac crests should be superimposed as well as vertebral bodies. Optimal density and contrast demonstrating soft tissue and bony markings. Spinal column aligned parallel to IR. No rotation is indicated by superimposed greater sciatic notches and posterior vertebral bodies.

Joints	Classification	Mobility Type	Movement Type
Z-Joints	Synovial	Diarthrodial	Plane (Gliding)
Intervertebral Joints	Cartilaginous (Symphysis)	Amphiarthrodial	Slightly moveable

IR: 14x17” LW
Position: Semi-supine or semi-prone; 45° obliquity (average). Use 50° oblique for L1/L2 Z-joints and 30° for L5–S1 Z-joints.
CR: Perpendicular to IR, 2” medial to the elevated ASIS and 1.5” above the iliac crest (lower rib margin and L3 level).
Technique: 85–95 kVp; 8–20 mAs.
AEC: Center cell; collimate on all four borders.
SID: 40” minimum.
Respiration: Suspended on expiration.
Analysis: T12–S1 included. "Scotty dog" appearance: eye and nose over the center of the vertebral body; Z-joints open and uniformly visible. RPO/LPO show the downside; RAO/LAO show the upside. Over-rotation is indicated if the pedicle is closer to the midline of the vertebral border. Under-rotation is indicated if the pedicle is lateral on the vertebral body border with more of the lamina demonstrated.

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