A head clamp for Magnetic Resonance and X-ray imaging is generally C-shaped including a base and two legs carrying pin clamp members. A course and fine adjustment system allows one of the clamp members to move inwardly relative to the other and then to be finely adjusted so as to apply a clamping force to the skull. The C-shaped support member comprises a truss with a C-shaped inner band adjacent the skull, an outer band generally following the shape of inner band and a plurality of openings defining spaced bars between the inner band and the outer band. The adjustment system comprises a screw that adjusts the width of the C-shaped member at the base and at one leg and includes a gauge to measure force applied with the mechanism located outside the field of view of the head both vertically and horizontally.