Embodiments of the present description provide a medical apparatus for use in supporting a patient lying in a supine position during a radial cardiac catheterization procedure. More particularly, embodiments of the present description provide an arm board a patient's arm during a radial cardiac catheterization procedure. The arm board is a substantially planar member having a support surface on which the patient's arm can be stabilized during a catheterization procedure. Desirably, the arm board has both a radiolucent portion and a radiopaque portion, thereby reducing and/or eliminating a doctor's exposure to radiation during radial cardiac catheterization procedures without impairing the ability to obtain the necessary medical images. Also provided is a medical apparatus and a method for its use.