A collimator including an inner border whose inner perimeter defines an aperture, an outer border positioned outwards of the inner border, an enclosure being defined and bounded between the inner and outer borders, the enclosure being sufficiently filled with a radiopaque pliable material so as to block a predefined amount of radiation from passing through the enclosure, while allowing radiation to pass through the aperture, and at least one actuator attached to at least one point of the inner border operable to deform the inner border so as to modify a shape of the aperture.