Investigation of a phase-only correlation technique for anatomical alignment of portal images in radiation therapy.

A new image registration algorithm based on phase-only correlation is applied to portal images in radiation therapy to detect translational shift. The phase-only correlation shows a sharp peak in the correlation distribution as compared to the broad peak computed from conventional correlation using fast Fourier transform. In this paper, the algorithm of phase-only correlation is described and its applicability and robustness are tested when applied to portal images used in clinical radiation oncology. The results achieved give evidence that the phase-only correlation will deliver an alternative approach for image registration and image comparison, that may be applicable in routine clinical practice.