Anatomy Demonstrated; Sacrum, L5-S1 joint and coccyx. No rotation is indicated by superimposed greater sciatic notches and femoral heads. 

Patient Positioning; Place patient in the lateral recumbent position with head on pillow and knees flexed. Align long axis of sacrum and coccyx to CR and midline of IR. Suspend respiration during exposure to reduce motion. 

IR: 10x12 - portrait. Four-sided collimation.  

SID: 40 inches. A lead mat should be placed on the table behind the patient to reduce scatter. 

CR: Perpendicular to IR. Direct CR 3-4 inches posterior to ASIS (this is the same centering for the sacrum. 

Clinical indications: Pathology of the sacrum and coccyx, including fracture. The sacrum and coccyx are commonly imaged together. Seperate AP projections are required because of different CR angles but the lateral projection can be obtained with one exposure centering to include both the sacrum and coccyx. This projection is recommended to reduce gonadal doses.