Is a person considered an adulterer if he imagines images of other people during intercourse, and is this a sin that warrants the torment of Hellfire?

It is impermissible for a woman to imagine another man while having intercourse with her husband if she intentionally brings about these imaginations. However, if they occur without her intention and she does not dwell on them, then there is no sin upon her; for the Messenger of Allah, peace and blessings be upon him, said: "Indeed, Allah has forgiven my nation for whatever they whisper to themselves, as long as they do not act upon it or speak of it." She must repel these imaginations and divert her mind from them.