A method of monitoring a patient includes: obtaining an input image having a plurality of regions of interest by a processing unit； and determining a plurality of positions for the respective plurality of regions of interest by the processing unit； wherein the act of determining the plurality of positions comprises: accessing a plurality of templates； comparing the plurality of templates with respective areas in the input image using a comparator in the processing unit； and determining the plurality of positions based at least in part on a result of the act of comparing.
