In general all embodiments relate to implantable medical devices 16 including at least one injectable device and at least one anchor 12 for fixation of the injectable device to body tissue. The anchor 12 of the implantable medical device 16 fulfills the requirement for secure anchoring of the injectable device to body tissue. The medical device includes at least one contrast agent reservoir 20 with an outlet 36, wherein the reservoir 20 is filled with a contrast agent 14, which may be released through the outlet 36 into body tissue or cavities. The contrast agent 14 is able to be visible with known imaging methods comprising X-ray or MRI imaging or other well-known techniques to determine if a secure anchoring of the medical device 16 has been achieved.