Classical T2 mapping based on 2D multi-echo spin-echo sequences achieves only limited across-slice resolutions. For clinical use, acquisitions with high isotropic resolution are however desirable, resulting in clinically prohibitive scan times. To this end, we propose a 3D multi-echo gradient and spin echo sequence with CAIPIRINHA and an additional model-based acceleration for T2 estimation. The combination of these techniques allows for whole-brain T2 mapping with 1.6mm-isotropic resolution in 3:26 min. The proposed framework was tested both in phantom and in vivo experiments.