CAMRT Radiography Practice Exam

To best demonstrate the left SI joint, which position with CR perpendicular is recommended?

1. AP

2. RPO

3. LPO

4. Crosstable lateral

The correct answer is: RPO

To effectively demonstrate the left SI joint, the recommended position is the right posterior oblique (RPO) position with the central ray (CR) directed perpendicular to the image receptor. In this position, the patient is rotated approximately 25 to 30 degrees to the right side, which places the left SI joint closest to the imaging receptor. This orientation helps to open up and better visualize the left sacroiliac joint, providing clearer images for assessment. The CR should be centered over the left SI joint, thereby allowing for optimal exposure of the joint space. Using the RPO position provides a clear view of the anatomy of the left SI joint by minimizing superimposition from the surrounding structures, which is essential for accurate evaluation and diagnosis. This positioning technique is standard practice in radiographic imaging for maximizing joint visualization.