Section 64L. The board of trustees of the hospital, with the approval of the commissioner, shall appoint a superintendent who shall be the chief executive officer of the hospital. The person appointed as superintendent shall have a doctoral degree or a master’s degree from an accredited college or university in the area of medicine, law, gerontology, psychology, rehabilitation, or hospital administration. The superintendent, with the approval of the trustees, may appoint and remove subordinate officers and employees as are necessary to carry out the purposes of the hospital. Such employees shall not be subject to section forty-five, forty-six, and forty-six C of chapter thirty or to any other limits on the number and classification of permanent and temporary positions.