An apparatus comprising an implantable medical device (102), IMD, and a container for storing the IMD (102) prior to implantation in body tissue, the IMD (102) comprising transmitter/receiver circuitry (202) and at least one antenna (110) for wireless communication, which apparatus comprises at least one member (308) positioned in proximity to the IMD (102) when stored in the container, and in that the electrical material properties of the member (308) are such that the input impedance of the antenna (110) is adjusted to improve receive and transmit properties of the antenna (110) when the IMD (102) is stored in the container. A container for storing an IMD (102) having an antenna (110), which container comprises a packaging tray (302) for housing the IMD (102), the packaging tray (302) comprising a support (304) for supporting the IMD (102), which container comprises at least one member (308) positioned in proximity to the support (304), and in that the electrical material properties of the member (308) are such that the input impedance of the antenna (110) of a IMD (102) supported by said support (304) is adjusted to improve receive and transmit properties of the antenna (110). A method for packaging an IMD (102) prior to implantation in body tissue.Linvention concerne un appareil comportant un dispositif médical implantable (102), IMD, et un contenant pour stocker lIMD (102) avant implantation dans un tissu cellulaire. LIMD (102) comporte des circuits émetteurs/récepteurs (202) et au moins une antenne (110) pour une communication sans fil, lappareil comporte au moins un organe (308) positionné à proximité de lIMD (102) lorsquil est stocké dans le contenant, et les propriétés matérielles électriques de lorgane (308) sont telles que limpédance dentrée de lantenne (110) est ajustée pour améliorer les propriétés de réception et démission de lantenne (110) lorsque lIMD (102) est stocké dans le contenant. Le contenant pour stocker un IMD (102) ayant une antenne (110)
