Again, this question is broad enough that we can only refer you to your Users Manual you received when you purchased your phantom. There are so many phantoms, applications and scanners that it would be nearly impossible to answer in just a few short sentences.Generally speaking, you will want the long axis of cylindrical type phantoms parallel to the axis of rotation. You will want the phantom centered in the scanner’s field of view (this is not so important for MRI scanners). The reason for this is so that you can move the camera head(s) as close as possible to the phantom during the scan. This will obtain better resolution than having the camera(s) far away from the phantom.You will have to determine how you actually “mount” or suspend the phantom in the scanner opening. Many people lay the phantom on a blanket or similar object on top of their scanner’s patient bed. Other institutions have made special holders that clamp onto or replace the head holder. Others have used the collimator changing cart as a support, with adapters to actually support the phantom.Once you have decided upon a mounting method, and while monitoring the phantom position on the persistence scope or computer monitor, the angulations and tilts of the phantom can be adjusted prior to the scan. While still in “persistence” mode, rotate the camera to top, bottom and sides of the phantom. Adjust the phantom position based on these images. Generally, you will look for the edges of the phantom to be parallel, or “square”, with the edges of the P-scope.