An image processing device comprising: an electronic processor; a display operatively connected with the electronic processor; and at least one non-transitory storage medium storing instructions readable and executable by the electronic processor to perform an image reconstruction process including: reconstructing an imaging data set comprising counts along lines of response (LORs) to generate a full-volume image at a standard resolution; selecting a region of interest by operations including at least providing a region selection graphical user interface via which a user-chosen ROI is defined in the full-volume image; selecting a sub-set of the counts of the imaging data set for reconstructing the ROI; reconstructing only the sub-set of the counts to generate a ROI image representing the ROI at a higher resolution than the standard resolution; and displaying the ROI image on the display, wherein selecting the sub-set of the counts comprises: selecting an initial sub-set of the counts; and adding or removing counts to or from the initial sub-set to optimize a cost function, wherein the cost function provides a metric of a quality of the image that would be generated by reconstructing the chosen sub-set, balanced against reconstruction time. an electronic processor; a display operatively connected with the electronic processor; and at least one non-transitory storage medium storing instructions readable and executable by the electronic processor to perform an image reconstruction process including: reconstructing an imaging data set comprising counts along lines of response (LORs) to generate a full-volume image at a standard resolution; selecting a region of interest by operations including at least providing a region selection graphical user interface via which a user-chosen ROI is defined in the full-volume image; selecting a sub-set of the counts of the imaging data set for reconstructing the ROI; reconstructing only the sub-set of the counts to generate a ROI image representing the ROI at a higher resolution than the standard resolution; and displaying the ROI image on the display, wherein selecting the sub-set of the counts comprises: selecting an initial sub-set of the counts; and adding or removing counts to or from the initial sub-set to optimize a cost function, wherein the cost function provides a metric of a quality of the image that would be generated by reconstructing the chosen sub-set, balanced against reconstruction time. reconstructing an imaging data set comprising counts along lines of response (LORs) to generate a full-volume image at a standard resolution; selecting a region of interest by operations including at least providing a region selection graphical user interface via which a user-chosen ROI is defined in the full-volume image; selecting a sub-set of the counts of the imaging data set for reconstructing the ROI; reconstructing only the sub-set of the counts to generate a ROI image representing the ROI at a higher resolution than the standard resolution; and displaying the ROI image on the display, wherein selecting the sub-set of the counts comprises: selecting an initial sub-set of the counts; and adding or removing counts to or from the initial sub-set to optimize a cost function, wherein the cost function provides a metric of a quality of the image that would be generated by reconstructing the chosen sub-set, balanced against reconstruction time. selecting an initial sub-set of the counts; and adding or removing counts to or from the initial sub-set to optimize a cost function, wherein the cost function provides a metric of a quality of the image that would be generated by reconstructing the chosen sub-set, balanced against reconstruction time.