Thanks to [Best Landsat-5 TM band combination for detecting fire scars](https://gis.stackexchange.com/questions/108546/best-landsat-5-tm-band-combination-for-detecting-fire-scars/108569#108569) I am able to calculate burnt area in an absolute way (Normalized Burn Ratio).

Does a ratio or delta operation exist to calculate the regrowth area between two scenes?