Imaging methods and computer-readable media

One aspect of the invention provides an imaging method including: (a) acquiring a first fluorescent image of an object of interest impregnated with fluorescent nanodiamonds; (b) applying a magnetic field to the fluorescent nanodiamonds in order to decrease fluorescence of the fluorescent nanodiamonds; (c) acquiring a second fluorescent image of the object of interest; and (d) subtracting the second fluorescent image from the first fluorescent image to produce a resulting image. Another aspect of the invention provides an imaging method including: (a) applying a time-varying magnetic field to an object of interest impregnated with fluorescent nanodiamonds to modulate the fluorescence of the fluorescent nanodiamonds; (b) acquiring a plurality of fluorescent images of the object of interest; and (c) for each corresponding pixel in the plurality of fluorescent images, calculating a fluorescence intensity using a lock-in technique.