Radiation therapy (RT) has a well-established role in the therapeutic approach of patients with an several thoracic malignancies.

Currently, lung-based computed tomography (CT) dosimetric parameters are the most significant factors associated with radiation-induced lung toxicity. Up to now, three-dimensional conformal-RT (3D-CRT) and intensity modulated RT (IMRT) planning of thoracic targets are based on doses delivered to the “anatomical” lung defined on the simulation CT scan, regardless of regional difference in lung function.

The majority of patients treated for an intra-thoracic target suffer from pre-existing lung diseases (i.e. smoking related damages, chronic pulmonary diseases, etc.), which are frequently associated with inhomogeneous lung perfusion and pulmonary functions. The presence of the tumour itself can contribute to functional inhomogeneity.

Noteworthy, it could be important to take into account of these regional lung function variations. It has been already showed that different lung regions contribute differently to the pulmonary function, and the radiation dose delivered to non-perfused regions contributes less to functional lung radiation-induced damage. The identification (and sparing) of more functioning areas may be of major interest in order to reduce the risk of severe lung toxicities.

The aim of the present review is to report the current use of SPECT imaging in the RT scenario for the optimization of RT of intra-thoracic targets.