Measurement of Tumor Diameter-dependent Mobility of Lung Tumors by Dynamic MRI

Background And Purpose: To assess the influence of tumor diameter on tumor mobility and motion of the tumor bearing hemithorax during the whole breathing cycle in patients with stage I non-small-cell lung cancer (NSCLC) using dynamic MRI.

Patients And Methods: Breathing cycles of thirty-nine patients with solitary NSCLCs were examined using a trueFISP sequence (three images per second). Patients were divided into three groups according to the maximal tumor diameter in the transverse plane (<3, 3-5 and >5 cm). Continuous time-distance curves and deep inspiratory and expiratory positions of the chest wall, the diaphragm and the tumor were measured in three planes. Motion of tumor-bearing and corresponding contralateral non-tumor bearing regions was compared.

Results: Patients with a tumor >3 cm showed a significantly lower diaphragmatic motion of the tumor bearing compared with the non-tumor bearing hemithorax in the craniocaudal (CC) directions (tumors 3-5 cm: 23.4+/-1.2 vs 21.1+/-1.5 cm (P<0.05); tumors >5 cm: 23.4+/-1.2 vs 20.1+/-1.6 cm (P<0.01). Tumors >5 cm in the lower lung region showed a significantly lower mobility compared with tumors <3 cm (1.8+/-1.0 vs 3.8+/-0.7 cm, P<0.01) in the CC directions.

Conclusions: Dynamic MRI is a simple non-invasive method to differentiate mobility of tumors with different diameters and its influence on the surrounding tissue. Tumor diameter has a significant influence on tumor mobility and this might be taken into account in future radiotherapy planning.