4D-MRI analysis of lung tumor motion in patients with hemidiaphragmatic paralysis

Abstract Purpose To investigate the complex breathing patterns in patients with hemidiaphragmatic paralysis due to malignant infiltration using four-dimensional magnetic resonance imaging (4D-MRI). Patients and methods Seven patients with bronchial carcinoma infiltrating the phrenic nerve were examined using 1.5T MRI. The motion of the tumor and of both hemi-diaphragms were measured on dynamic 2D TrueFISP and 4D FLASH MRI sequences. Results For each patient, 3–6 breathing cycles were recorded. The respiratory-induced mean cranio-caudal displacement of the tumor was 6.6mm (±2.8 SD). The mean displacement anterior–posterior was 7.4mm (±2.6), while right–left movement was about 7.4mm (±4.5). The mediastinum moved sidewards during inspiration, realizing a "mediastinal shift". The paralyzed hemidiaphragm and the tumor showed a paradox motion during respiration in five patients. In two patients, the affected hemidiaphragm had a regular, however minimal and asynchronous motion during respiration. Respiratory variability of both tumor and diaphragm motions was about 20% although patients were instructed to breath normally. The findings showed significant differences compared to breathing patterns of patients without diaphragm dysfunction. Conclusion 4D-MRI is a promising tool to analyze complex breathing patterns in patients with lung tumors. It should be considered for use in planning of radiotherapy to account for individual tumor motion.