(a) The requirement that periodic reports on the medical care being rendered be filed in the office of the district director, the frequency thereof being determined by order of the district director or sound judgment of the attending physician as the nature of the injury may dictate;

(b) The determination of the necessity, character and sufficiency of any medical care furnished or to be furnished the employee, including whether the charges made by any medical care provider exceed those permitted under the Act;

(c) The determination of whether a change of physicians, hospitals or other persons or locales providing treatment should be made or is necessary;

(d) The further evaluation of medical questions arising in any case under the Act, with respect to the nature and extent of the covered injury, and the medical care required therefor.