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

.. py:function:: petpal.preproc.regional_tac_extraction.roi_tac(input_image_path: str, roi_image_path: str, region: list[int] | int, out_tac_path: str | None = None, time_frame_keyword: str = 'FrameReferenceTime') -> petpal.utils.time_activity_curve.TimeActivityCurve

   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.

   :param input_image_path: Path to the 4D PET image from which the regional TAC will be
                            extracted.
   :type input_image_path: str
   :param roi_image_path: Path to the segmentation image containing ROIs. Must be in the same
                          space as input_image.
   :type roi_image_path: str
   :param region: The region or regions that will be extracted as a TAC. If a list
                  of regions are provided, the function combines all listed regions and calculates the
                  TAC from the merged region.
   :type region: list[int] | int
   :param out_tac_dir: Path to the TSV where the regional TAC will be written to.
   :type out_tac_dir: str
   :param time_frame_keyword: Keyword corresponding to either 'FrameReferenceTime' or
                              'FrameTimesStart' to get the frame timing. Default 'FrameReferenceTime'.
   :type time_frame_keyword: str

   :returns: *region_tac (TimeActivityCurve)* -- The mean time activity curve for the region.