The paper describes a procedure for lossless coding of medical images that uses a non-linear integer-to-integer wavelet transform generated by a lifting scheme and featuring progressive transmission capability. The quantization module implements a new modality for the coding of the wavelet coefficients that is more effective than the classical zerotree coding. Lossless image compression with progressive transmission capabilities plays a key role in medical image acquisition and handling. The contradictory requirements of exact data reconstruction possibility and of efficient and economic handling and transmission of large sets of images over large distances have to be met simultaneously. The experimental results, obtained on a set of 20 multimodal medical images, show that the algorithm outperforms other existing image lossless coding algorithms. Therefore it is a good candidate for telematics applications like teleradiology and PACS.