According to the Catholic Church, can a tattoo be considered a sacramental?

**According to the Catholic Church, can a tattoo be considered a sacramental?** I have a friend who is thinking about getting a tattoo on each shoulder, containing the image of the Medal of St. Benedict . There are several different blessings for this medal now. Any priest may bless the Medal of St. Benedict and some blessings have the word image in lieu of the word medal. If a priest were to bless this image would it be considered a sacrament, according to the Catholic Church. Although I am bring up the case of the Medal of St. Benedict, any other image in use in this question could hold also. In the case of lack of official Catholic Church teachings on this subject could a priest simply bless such holy images? Is there any Church prohibitions against this? Are priests allowed to bless tattoos? After all there are also blessings for people in the Rituale Romanum! Here follows the image of the Medal of St. Benedict that my friend is considering. St. Benedict Medal