not shown of the jacket 1 a clasp 3 can also be seen in fig2 the anchor point 2 in fig2 is the same as that which can be seen in fig3 and includes a base plate 4 and a connection or connection section 9 the base plate 4 is embedded within the filling material of the vacuum jacket 1 or vacuum mattress wherein the connection section 9 protrudes upwards out through the upper material of the jacket 1 the resultant opening in the jacket is sealed using an air or gas tight seal by embedding the base plate 4 it is enveloped on all sides by the filling material of the jacket 1 and rigidly fixed once the jacket has been evacuated rigidly fixing the base plate 4 with respect to the jacket 1 and therefore with respect to the patient ultimately leads to the reference array 5 being rigidly and immovably fixed with respect to the parts of the patient 39 s body to be treated on its upper side the reference array 5 includes for example three markers 8 the markers can be reflective passive markers that can be detected using infrared cameras markers for visible light also can be used or markers which passively or actively indicate their position within electrical or magnetic fields each of the above markers 8 can be localized by the navigation system navigation systems are well known in the art.