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AEA survey on image-guided radiotherapy protocols and doses in the European region

Purpose: This survey was part of a safety initiative under the IAEA technical cooperation (TC) programme for Europe. The purpose was to provide the participating radiotherapy centers with the feedback on where the values of the IGRT acquisition settings used at their institution stand in comparison with the values used in other radiotherapy centers in the region. Materials and Method: A survey form designed by an international team of IGRT experts has been distributed to the radiotherapy centers participating in the regional TC program for Europe through the national counterparts in October 2018. After a TC meeting in November 2019, the participating parties were asked to provide an update. Results: 51 radiotherapy centers from 19 countries from Eastern, Central and Southern Europe responded to the survey, submitting data for 86 medical linear accelerators. 67% of them are fitted with kV imaging system. Even so, MV imaging remains an important issue. There was a 5-fold difference between the MU spent per planar image between the participating centers. For kV imaging, values for five anatomical sites (head, head & neck, thorax, abdomen, pelvis) were collected separately. The results for kV planar imaging markedly differ. For lateral pelvis imaging, most centers use tube voltage of either 100 or 120 kV, while for lateral thoracic imaging, values from 80 kV to 140 kV are used. Tube current-exposure time product shows the opposite trend, with the biggest variation (5-40 mAs) in the values used for lateral pelvic imaging. With kV CBCT, almost all centers use 20 mA for thoracic area, while values 25-80 mA are used for abdominal and pelvic area. This also reflects in the CTDI values, with the values for imaging in the thoracic region having a sharp maximum at 4 mGy, while the values for abdominal region vary from 5 to 25 mGy. The centers acknowledge the importance of quality assurance of imaging systems ; they however quote very different protocols they follow, from vendor-provided to various international (EFOMP) and national (AAPM) protocols. CTDI displayed values are not commonly verified. Conclusions: Lack of standardization and potential for optimization of IGRT protocols was observed. The values of the image acquisition settings differ markedly between centers. Another important result of the survey is that medical physicists working in radiotherapy expressed they feel a lack of expertise in the medical imaging, which is an issue worth tackling.

image-guided radiotherapy, planar imaging, cone-beam CT, quality assurance, IGRT doses.

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