Mode scanning: Heating pattern synthesis with ultrasound phased arrays

Modes, the characteristic symmetric focal patterns of an ultrasound phased array, prove especially useful for hyperthermia. Modes cancel the complex pressure fields exactly along the central axis, eliminating axial constructive interference both proximal and distal to the treatment volume. A simple calculation exploits planar or rotational array symmetry and produces the driving signals which generate modal focal patterns. Results show that temporal mode scanning improves heating patterns considerably, expanding the maximum treatable size of the tumour volume.