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This forum post is linked to our recent SGRTuesdays webinar series, which runs monthly on the last Tuesday of each month. Each session covers essential knowledge, research, and practical tips to enhance precision in radiotherapy treatments.

Please feel free to use this thread to ask any questions you might have for our speakers. (You do not need to have attended the webinar to post)

[Matthew Williams]

I was interested to hear about the DIBH issue mentioned in the second presentation from Waterford, with greater vert displacement inferiorly at the position of monitoring at CT, but very small displacement at the level of the breast. We've recently encountered a similar issue a couple of times, and it is challenging.
A solution of removing the visual aid was mentioned, I'd like to understand this a little better - were operators just visualising monitoring the surface for agreement? (as opposed to the numerical readout). Did you consider using a different ROI as an alternative?
Matthew Williams,
Clinical Scientist,
Velindre Cancer Service, Cardiff

[marko_laaksomaa]

Good afternoon from Finland

I am not the speaker. Therefore, I am sorry that I answer, but I feel I have something to give to this issue.

We are talking about belly breathers again, I suppose. I think we should take the belly breathing into account in the ROI delineation. Cranial belly should include to ROI in those cases, if it is the only thing that remarkably moves in DIBH. Please, check our ROI, suggested to us by VisionRT some years ago, without finding any reason to change it so far, https://journals.viamedica.pl/rpor/article/view/91429. This kind of ROI is slightly wider to take account belly movement in these belly breathing DIBH- cases from the caudal part of it.

In the presentation example in the Waterford, it is noticeable that in the FB- and DIBH- images diaphragm moves remarkably in DIBH, nothing else is moving much. Patient benefits of DIBH in that kind of case then, as the speakers mention.

I think what is most important in these kind of cases is to check the diaphragm level in CBCT. Does it match with DRR diaphragm level after bony match in the CBCT- images? Spine vs. sternum distance is not telling the true realized BHL in this kind of case, since sternum is not moving much in DIBH. I think to take RTC monitoring away is very good instant-solution, but not the only or future fraction- solution, even though it gives more space to patient to take natural DIBH, when searching the optimal BHL (in the CBCT- images). After this behaviour we likely need new reference surfaces for the future fractions, RTC monitoring, and ROI adjustement to take account the movement of the belly in DIBH.


Best regards Marko