The invention relates to a device and method for inserting a needle in an animal body for effecting radiation therapy in the body, including a template for positioning the needles to be inserted, needle drive structure for drive a needle through said template towards a desired location in the body, and real-time imaging structure for creating and presenting an image of the desired location and the position of said needle during the insertion of said needle. Due to the fact that the bevelled tip of a hollow needle cause the needle to diverge away from the "line of insertion or movement" and away from the actual desired position in the animal body adversely affecting the dosimetry quality of the implanted seeds a more accurate insertion of the needle is required. According to the invention the device is provided with adjusting structure for adjusting a movement of said needle towards said desired location during insertion.