We extend the sharing scheme proposed by Mignotte in 1983 based upon Chinese remainder theorem (CRT) to devise a threshold secret sharing scheme for digital images. Given a secret image I and a set of n participants sharing I, our scheme encrypts I into n shadows in such a way that any group of r shadows can recover I while that of less than r shadows cannot where 2 les r les n. As compared to the similar work by Meher and Patra in 2006, which is not a threshold scheme, our design satisfies the threshold requirements so that it is more technically sound. Our work reveals a new research area of applying CRT in secret image sharing.