Biomedical photoacoustic tomography (PAT) is a soft-tissue imaging modality which combines the high spatial resolution of ultrasound (US) with the contrast and spectroscopic opportunities afforded by imaging optical absorption. Planar US arrays composed of piezoelectric or optical detector elements with small element sizes and fast acquisition times are readily available, making them an attractive option for imaging applications. An exact and efficient, FFT-based PAT reconstruction algorithm,

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... at converts acoustic measurements recorded over a plane to a PAT image, is known. However, to capture sufficient data for an exact PAT reconstruction with a planar geometry requires an infinitely wide array. In practice it will be finite, resulting in a loss of resolution and introducing artefacts into the image. To overcome this limitation it is proposed that acoustic image sources, provided by enclosing the target in a reverberant cavity, are used to generate a periodically repeating sound field. Measurements of this periodic sound field can be used to reconstruct a PAT image exactly from measurements of reverberation made over a finite aperture. The existing FFTbased PAT reconstruction algorithm with only minor additional modifications can be used to generate the image in this case.