Imaging of normal lung, liver and parotid gland function for radiotherapy

Abstract

There is growing clinical evidence that functional imaging is useful for target volume definition and early assessment of tumour response to external beam radiotherapy. A subject that has perhaps received less attention, but is no less promising, is the application of functional imaging to the prediction or measurement of radiation adverse effects in normal tissues. In this manuscript, we review the current published literature describing the use of positron emission tomography (PET), four-dimensional computed tomography (4D-CT), single photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) to study normal tissue function in the context of radiotherapy to the lung, liver and head & neck. Published results to date demonstrate that functional imaging can be used to preferentially avoid normal tissues not easily identifiable on solely anatomical images. It is also a potentially very powerful tool for the early detection of radiotherapy-induced normal tissue adverse effects and could provide valuable data for building predictive models of outcome. However, one of the major challenges to building useful predictive models is that, to date, there are very little data available with combined images of normal function, 3D delivered radiation dose and clinical outcomes. Prospective data collection through well-constructed studies which use established morbidity scores is clearly a priority if significant progress is to be made in this area.

Acknowledgements

M. Partridge acknowledges NHS funding from the NIHR Biomedical Research Centre and funding from CR UK under grant C46/A10588. T. Yamamoto is grateful to Dr. Paul J. Keall at Stanford University for reviewing the paragraphs on 4D-CT ventilation imaging in Section 3 (Imaging of lung function) and providing helpful suggestions. Morten Høyer is supported by A.P. Moller and Chastine Mc-Kinney Møller Foundation. This work was supported by CIRRO – The Lundbeck Foundation Center for Interventional Research in Radiation Oncology, The Danish Council for Strategic Research and by research grants from the Danish Cancer Society and The Danish Council for Independent Research (FSS).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.