Compared to 4D-CT, 4D-T2w MRI should better characterise respiratory motion in radiotherapy, due to its superior soft tissue contrast. However, 4D-T2w MRI is difficult to acquire due to the long echo and repetition time required. Here, 4D-T2w MRI is obtained by applying motion information from a 4D-T1w volume to a static 3D-T2w volume. For three patients, 4D-T2w MRI was compared to 4D-T1w MRI. Diaphragm positions were consistent to <1.5mm. A method to calculate 4D-T2w MRI, with potential application to an MR-linac, is presented and verified.