SACROILIAC JOINTS X-RAY | AP AXIAL VIEW / PROJECTION | ALTERNATIVE PROJECTION

AP Axial Sacroiliac joints Patient's position, Respiration, Pathology demonstrate shielding and shielding.

Taking sacroiliac joints in ap axial the patient is in supine position, provide pillow for head and knee support under knee for patient comfort. For patient position the legs is fully extended. Demonstrated pathology are dislocation or subluxation of the Sacroiliac joints (SI joints) and fracture. During exposure respiration is suspended to minimize patient motion. Use of gonadal shielding for males. For females it not possible to use lead shield (ovarian shielding) because it will directly obscure the area being radiograph.

What are the Technical and Central Ray Factors?

Image receptor size - 24 x 30 cm or 10 x 12 inches.
Moving or stationary grid are applicable.
85 kV decrease or increase by  5 kV depending on body habitus.
mAs 9.
Central Ray is 30° to 35° cephalad (towards the head).
Males requires 30° CR angulation.
Females requires 35° CR angulation, with an increase in the lumbosacral curve.
Central Ray is Directed to a middle point about 2 inches below the ASIS.
SID is 40 inches or 100 cm.

Collimation and Part Position:

Collimation is to area of interest but be sure that side of margins do not cut off sacroiliac joints.
Align the midsagittal plane to CR and to middle of x-ray table/ bucky / grided cassette.
Ensure that pelvis is not rotated.
ASIS table distance equal on both sides.
Angulated CR is directed or projected to middle of the IR.

RADIOGRAPHIC CRITERIA:

Stucture Shown on Radiograph: Sacroiliac joints, L5 to S1 junction and the entire sacrum is evident.
Proper Patient Position: No rotation when spinous process of L5 is in middle of vertebral body and symmetric appearance of bilateral wings (ala) of sacrum.
Sacroiliac joints are equally distant from midline of vetebrae.

Collimation, CR, and Exposure Criteria: 

Correct Central Ray angulation when sacroiliac joints spaces and the L5 to S1 junction and sacral foramina should appear open.
Proper Collimation: Sacroiliac (SI) joints and the first two segments of sacrum must be in center of radiograph or in the collimated field.
Exposure Criteria: Optimal density should visualize all of the sacrum and the margins of the SI joints spaces.
Bony margins and trabecular markings should be visible and sharp, indication no motion.

ALTERNATIVE PA AXIAL PROJECTION:

If patient cannot assume the AP position (supine), patient can be taken in prone (PA Projection) with a reverse central ray agulation 30° to 35° caudad angle. The Central Ray (CR) will be centered to the level of L4 or slightly above the iliac crest.