Image-based data corrections for Positron Emission Mammography

ClearPEM is a rotating, dual planar detector PET system dedicated to breast and axilla imaging that needs data corrections in order to improve quantification and lesion detectability. Since the scanner does not have CT nor transmission sources, we are implementing data corrections that use emission-only data. Also, since in this work we are using an iterative list-mode reconstruction algorithm that projects the data directly through a 3D grid of points, all the corrections are applied in image space. We describe the current implementation and validation of image-based corrections for normalization, scatter, attenuation and randoms. Normalization correction uses sensitivity images generated by backprojecting data from a planar source. Energy-based scatter correction is applied using the Estimation of Trues Method because this method does not require information about attenuating media and takes into account the activity outside the FOV. Attenuation correction is calculated from the segmentation of the breast in the emission images. Randoms correction is performed by subtraction of a smoothed image obtained from the backprojection of the delayed coincidences. The implementation of other corrections is also being pursued in order to obtain fully quantitative images in breast imaging.