Use of 4D-CT for radiotherapy planning and reality in France: Data from a national survey.

PURPOSE: Lung and some digestive tumours move during a respiratory cycle. Four-dimensional scanography (4D-CT) is commonly used in treatment planning to account for respiratory motion. Although many French radiotherapy centres are now equipped, there are no guidelines on this subject to date. We wanted to draw up a description of the use of the 4D-CT for the treatment planning in France. METHODS AND MATERIAL: We conducted a survey in all French radiotherapy centres between March and April 2017. RESULTS: One hundred and seventy-two were contacted. The participation rate was 88.37%. The use of the 4D-CT seems to be common and concerned planning for 15.28% of kidney and adrenal cancers, 19.72% of pancreatic cancers, 27.78% of oesophageal cancers and 73.24% of lung cancers in case of normofractionated treatments. The use of the 4D-CT was also widespread in the case of stereotactic body radiation therapy: with 61.11% in the case of pulmonary irradiation and 34.72% in the case of hepatic irradiation. Many centres declared they carried out several 4D-CT for treatment planning (29, 55% in case of stereotactic body radiation therapy for lung tumours and 20% for liver tumours). Private centres tend to repeat 4D-CT more. CONCLUSION: Although the use of the 4D-CT appears to be developing, it remains very heterogeneous. To date, the repetition of the 4D-CT has been very poorly studied and could be the subject of clinical studies, allowing to define in which indications and for which populations there is a real benefit.

[Use of 4D-CT: Main technical aspects and clinical benefits]. / Utilisation de la scanographie quadridimensionnelle : principaux aspects techniques et intérêts cliniques.

The four-dimensional scannography, also called 4D-CT, was created in the early 2000s. This method enables the aquistion of CT-scans synchronised with the patient's breathing. It allows an anatomical observation depending on the time. Different systems have been marketed. They are commonly used in treatment planning. It allows to take into account respiratory motion, considering the changes of shape and position of the tumor and organs. In the age of new techniques and stereotactic irradiations, 4D-CT is a valuable tool for estimating the uncertainties associated with respiratory movements, This technique also presents some limitations, including artifacts. The quality of the examination can be degraded in some patients with irregular respiration. Here we propose a summary of this technique detailing its principle of operation, its advantages and its main limits.