A mounting structure for mounting an x-ray tube on a CT rotatable gantry is disclosed. The mounting structure includes base plates that are boltable to the CT rotatable gantry and have bearing strut connections formed thereon. Spherical bearing struts are provided in the mounting structure to mechanically couple the x-ray tube to the base plates, with the spherical bearing struts each having a first end secured in a respective bearing strut connection of the x-ray tube casing and a second end secured in a respective bearing strut connection of the base plates. The spherical bearing struts constrain a gantry-load direction displacement of the x-ray tube and enable rotation and displacement of the x-ray tube around at least one axis of rotation or in one direction other than a gantry load direction, so as to accommodate thermal displacements in the x-ray tube created during operation thereof.