Calculating MADI will produce a single band image. You can accomplish this calculation in the raster calculator. This is the expression you will need to use in the raster calculator if you are using composite (stacked) imagery:
"your_modis_image.tif - Band_1" / "your_modis_image.tif - Band_7"
Otherwise, if your imagery is composed of non-stacked bands:
"your_modis_image_band1.tif" / "your_modis_image_band7.tif"