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Repainting and breathing cycle

IP.com Disclosure Number: IPCOM000248371D
Publication Date: 2016-Nov-22
Document File: 4 page(s) / 190K

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Abstract

When using particle beam scanning technologies for irradiating potentially moving targets, problems of interplay are generally occuring. With a particle beam therapy system, the target can be irradiated multiple times by delivering so-called multiple paintings. Studies have demonstrated that in order to reduce the effect of the interplay, the paintings had to be spread on the different phases of the movement of the target.

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Repainting

Field: radiotherapy, particle therapy

Author: Yves Claereboudt

Abstract: Using particle beam scanning technologies on potentially moving targets bring problems of interplay.  Studies have demonstrated that in order to reduce the effect of interplay, paintings had to be spread on the different phases of the movement of the target.

1.     State of the art

For target which movement is induced by the breathing cycle, two main methods have been identified to obtain this spread.

1.1.  Free breathing

In this technique, we have the patient breath freely and insure a large enough number of paintings so that painting gets randomly spread on the breathing cycle.

As shown above, this technique works fine when the duration of the painting is relatively small compared to the duration of the breathing cycle.

However, a major problem is that the frequency of the breathing cycle (0.5 to 0.1 Hz) and the frequency of the repainting cycle (10 to 0.1 Hz) can for some patient be very close to one another.

In such case, the repainting strategy might not work as intended because the same part of the target could get painted at about the same phase of each breathing cycle. For such cases, there is no gain in repainting.

The problem also occurs when the duration of a breathing cycle divided by the duration of a painting is a small integer (e.g. 2 or 3). In such case, there is no benefit of increasing the number of painting above that small integer.

There is no obvious solution to such problem as this is really patient and tumor specific. It might occur unexpectedly for some patients and influence negatively the quality of their treatment.

1.2.  Synchronized breathing

With this technique we have the patient breath synchronously with an external signal and force the spreading of the paintings on the different phases of the cycle.

Although this technique works, a significant portion of the breathing cycle will be spent waiting for the correct phase to start the next painting.

 


2.     Invention

This invention defines innovative techniques to spread the paintings on the different phases of the breathing cycle without introducing waiting times in between paintings.

The invented techniques are linked to improvement of the synchronized technique where the patient breathing cycle is controlled and/or monitored (e.g. through audio or video coaching).

The general idea is to split a painting in smaller blocs that can then be more easily spread on the different phase...