Imaging the Lung in Radiotherapy: Where 4D Meets Multimodality

The increasing research and clinical interest in the intrafractional motion management of lung tumour radiation treatment is in part fuelled by the availability of multiple 4D modalities that resolve temporal information of the tumour motion. These improved imaging modalities allow the escalation of dose to the tumour besides enhancing the conformality of the dose to a moving tumour, which could improve the local control rate. Magnetic resonance imaging (MRI; including dynamic MRI and hyperpolarized ³He tagging), 4DCT, fluoroscopy and EM transponders are reviewed in this article. The working mechanisms, advantages/disadvantages and unique information of these techniques and their contribution to the management of lung cancer are discussed.