Correlation between parameters describing tumour motion and its location in the lungs.

Characterizing respiratory-induced tumour motion is an important step in the effective image-guided radiation treatment of moving tumours, especially for tumours in the lung and lower abdomen. This study characterized tumour motion based on a piecewise linear model representing tumour motion at defined stages of the breathing cycle. Lung tumour locations were categorized based on broncho-pulmonary segments. Association rules between tumour motion characteristics and their locations in the lung were discovered and parameterized through statistical analysis. Results show there is a correlation between tumour motion characteristics and tumour location in the lungs. Generally, tumours with small motion (amplitude < 10 mm) are observed most frequently in the apex region of lung or when attached to a fixed structure, such as the chest wall or aorta. Tumours with relatively large motion (amplitude > 20 mm) are located close to the diaphragm or mid-level periphery of the lungs close to the chest wall.