Comparison of different registration landmarks for MRI‐CT fusion in radiotherapy for lung cancer with post‐obstructive lobar collapse

The registration of the two sets of images based on the spine and pulmonary artery landmarks and the geometric center difference of the mean displacement in the X, Y, and Z directions (X, Y, and Z represent the directions of the body from left to right, superior to inferior, and anterior to posterior) between their MRI‐CT fusions were compared, respectively. Fifty‐five lung cancer patients with post‐obstructive lobar collapse were enrolled in this study. Before radiation, two sets of simulating images according to the spine and the pulmonary artery registrations were obtained for each patient using MRI‐CT fusion. The differences of mean displacement in the X, Y, and Z directions based on spine and pulmonary artery landmarks were of −0.29, 0.25, and 0.18 cm, respectively. The mean displacements of the pulmonary artery based images in the three directions were smaller than that in the spine registration images (P < 0.05). By the method of pulmonary artery landmark, MRI‐CT has better registration accuracy and can better help confirm the target volume.