St. Luke is one of the four evangelists and the writer of the Acts of the Apostles. St. Luke is the patron saint of artists, physicians and students. His feast day is October 18.
A well-known prayer to St. Luke:
Most charming and saintly Physician, you were animated by the heavenly Spirit of love. In faithfully detailing the humanity of Christ, you also showed his divinity and his genuine compassion for all human beings. Inspire our physicians with your professionalism and with the divine compassion for their patients. Enable them to cure the ills of both body and spirit that afflict so many in our day. Amen.
http://www.itmonline.org/bodytheology/stluke.htm