roi_tac
==========================================

.. py:function:: petpal.preproc.image_operations_4d.roi_tac(input_image_path: str, roi_image_path: str, region: int, out_tac_path: str, verbose: bool, time_frame_keyword: str = 'FrameReferenceTime')

   Function to write Tissue Activity Curves for a single region, given a mask,
   4D PET image, and region mapping. Computes the average of the PET image
   within each region. Writes a tsv table with region name, frame start time,
   and mean value within region.