In the era of big data, medical imaging systems create millions of medical images daily. Securing these images during their transmission and storage is a challenging task. Encryption is a practical approach for securing medical images, as it ensures the security of these images while preserving their sensitive contents. Multiple-image encryption is preferable to single-image encryption, in which patches of medical images are encrypted simultaneously. A novel multi-medical image encryption algorithm based on stack representation and block division is proposed. During preprocessing, the medical images are stacked into a 3D cube to prepare for the encryption process. The cube experiences a block division phase, followed by individual confusion and diffusion phases for each block. These phases utilize different keys generated from a Baker chaotic map, incorporating swapping and XOR operations, which result in a fully encrypted cube. The scalability and effectiveness of the proposed algorithm are tested through experiments, revealing its promise as a secure approach for encrypting color and grayscale medical images. The proposed MIE algorithm is robust against various attacks, exhibiting superior performance in terms of speed and security compared to similar methods.