Reconstruction of a three-dimensional image of a patient

A reconstruction node for reconstruction of a three-dimensional, 3D, image of a patient, the reconstruction node comprising processing circuitry configured to cause the reconstruction node to:

• obtain a projection set comprising a plurality of two-dimensional, 2D, projections of a first volume of the patient, the projections acquired using a first apparatus which is a Cone-Beam Computed Tomography, CBCT, apparatus;
• obtain a 3D image of a second volume of the patient, the 3D image reconstructed from projections acquired using a second apparatus, wherein the second volume of the patient at least partially overlaps with the first volume of the patient;
• use acquisition information relating to the obtained projection set to generate, from the obtained 3D image of the second volume of the patient, synthetic projections of the second volume of the patient;
• extend the projections of the first volume of the patient from the obtained projection set with information from the synthetic projections of the second volume of the patient;
• and
• use the extended projections to generate a 3D image of a third volume of the patient, wherein the third volume of the patient comprises a combination of the first volume of the patient and the second volume of the patient.