A table with 6 degrees of freedom is regarded as essential in order to adjust the patient position to correct for positioning errors and the like. However, this imposes a significant cost, has a redundant axis in a conventional linac treatment system, and adds to the volume of the table. We disclose a way of dealing with rotation of the patient in an axis about which the source has a limited range of rotation, without needing a rotational adjustment of the table. An apparatus comprises a radiotherapy delivery apparatus having a radiation source adapted to emit a beam of radiation and to rotate around at least one axis that intersects with the beam, the rotation being confined to a limited range of rotation, an associated imaging device, and a control means controlling both the source and the imaging device, together with a treatment planning computer that accepts an image of a patient and parameters defining the machine capabilities, and creates a treatment plan based on both, wherein the source is capable of rotation in that axis through a range of at least x degrees, and a parameter is passed to the treatment planning computer defining the source's available range as x-e where e>；0, and the control means is adapted to detect the patient position using the imaging device, determine a rotation r of the patient around the axis relative to the image used by the treatment planning computer, and if r<；e compensate for the rotation by offsetting the source by a rotation equal to r. The limited range of rotation is typically less than 360 degrees although this need not necessarily be the case. An example of the type of radiotherapy apparatus to which this invention is applicable is shown in our earlier patent application WO2005/041774, but it can equally be applied to other types.Une table ayant 6 degrés de liberté est considérée comme étant essentielle pour régler la position du patient afin de corriger les erreurs de positionnement, et analogues. Cependant, ceci imp
