An asymmetric half-wedged field technique for the treatment of inferiorly extended head and neck cancers.

Adequate dose coverage of the target volume of head and neck cancer patients can be difficult to achieve with lateral opposing fields when the patient's neck is short and the disease involves the lower cervical region. Rotation of the couch away from the side of the gantry, such that the beams are angled towards the inferior aspect of the patient, can result in a better dose distribution. However, if the neck separation is large, unacceptable dose inhomogeneities will still exist. The conventional approach in these situations is to treat with parallel opposed lateral fields junctioned with anterior/posterior opposed low neck fields. We present a variation on the couch rotation technique as an alternative. Asymmetric jaws and half-wedged fields are used to obtain a homogeneous dose within an inferiorly extended target volume. The advantages of this technique are a simple set up and the capability of adding spinal cord shielding without shielding midline primary tumour.