An algorithm for hiding patient's data from JPEG ultrasound images, applied directly on DCT (Discrete Cosine Transform) coefficients is presented. The algorithm can detect textual information using the amount of energy, computed using only AC coefficients, without converting medical images/video back to the spatial (uncompressed) domain. In order to offer a high quality care for patients, textual information containing the patient data is hidden or eliminated. Further, the processed medical images can be accessed and analyzed, for a second-opinion, by physicians, or in medical research, keeping the patients privacy provided of the ultrasound medical images. The algorithm has been implemented and verified with good performances.