LATERAL POSITION: LUMBAR SPINE

Pathology Demonstrated:

• Fractures on lumbar spine, spondylolisthesis, neoplastic processes, and osteoporosis of lumbar vertebrae are demonstrated.

Technical Factors:

• Film size - 35 x 43 cm (14 x 17 inches), lengthwise, or 30 x 35 cm (11 x 14 inches)
• Moving or stationary grid
• 85 to 95 kV range
• Lead mat on table behind patient
• mAs for female is 50
• mAs for male is 65

Shielding:

• Shield gonads without obscuring area of interest.

Patient Position:

• Position patient lateral recumbent, provide pillow for head, knee flexed, with support between knees and ankles to better maintain a true lateral position and ensure patient comfort.

Part Position:

• Align midcoronal plane to central and midline of x-ray table or grid.
• Place radiolucent support under waist as needed to place the long axis of the spine near parallel to the table (palpate the spinous processes to determine see note:)
• Ensure the pelvis and torso are in true lateral position.

Central Ray:

• Direct central ray perpendicular to long axis of spine.
• Larger IR (30 x 35cm): Center to level of iliac crest (L4 - L5). This position includes lumbar vertebrae, sacrum, and possibly coccyx.
• Center image receptor to central ray.
• Smaller film (30 x 35 cm): Center to L3 at the level of the lower costal margin. (1.5 inches above iliac crest.) This position includes the five lumbar vertebrae. Center IR to CR.
• SID is 40 inches or 100 cm.

Collimation:

• Closely collimate on lateral borders. (Light field appears small because of proximity of the patient to the x-ray tube and the divergence of the x-ray beam.)

Respiration:

• Suspend breathing on expiration.

Note: Although the average male patient (and some female patients requires no CR angle, a patient with a wider pelvis and a narrow thorax may require a 5° to 8° caudad angle even with support. If patient has a lateral curvature (scoliosis) of the spine (as determined by viewing of the spine from the back with the patient in the erect position and with hospital gown open), patient should be place in whichever lateral position places the "sag" or convexity of the spine, down to better open the intervertebral spaces.

Radiographic Criteria:

Structure Shown:

• Intervertebral foramina L1 to L4, vertebral bodies, intervertebral joints, spinous processes, and L5 to S1 junction are visible.
• Depending on the image receptor size used, the entire sacrum also may be included.
  

Position:

• Vertebral column is aligned parallel to the IR, as indicated by the following: intervertebral foramina appearing open; intervertebral joint spaces appearing open;
• No rotation is indicated by superimposed greater sciatic notches and posterior vertebral bodies.

Collimation and CR:

• The vertebral column should be centered to the collimated field of IR, at the level of L3.

Exposure Criteria:

• Optimal density and contrast should clearly demonstrated the vertebral bodies and joint spaces.
• Sharp bony margins indicate no motion.