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Low-dose CT allows for accurate proton therapy treatment planning

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Date: January 19, 2024 12-1 PM Eastern Time

Speakers: Masoud Elhamiasl

To practice daily adaptive proton therapy, a new CT image acquisition must be performed at every treatment session. However, the series of these repeated CT scans results in additional accumulated patient dose. Thus, minimizing exposure as low as reasonably achievable is crucial. We hypothesize that the signal-to-noise ratio provided by conventional CT protocols is higher than needed for proton therapy treatment planning. In this study, we assess the effect of reducing CT imaging dose on proton therapy dose calculation, plan optimization, and delineation of target volumes and organs at risk. To verify our hypothesis, a CT dose reduction simulation tool was developed and validated to simulate lower-dose CT scans from an existing standard-dose scan. The simulated lower-dose CTs were then used for proton therapy treatment planning and the results were compared with those of the standard-dose scan. The results show that low-dose CT can be used not only for proton therapy dose calculation and plan optimization but also for the delineation of target volumes and organs at risk. Furthermore, a strong overlap between the contours based on the low-dose and standard-dose CT was observed where the error is smaller than inter-observer variability.