Bootstrap Framework 3.3.6

[paul_robertson]

Hello All,



Recently we have started seeing in a few patients a marked difference in diaphragm level compared to the planning CT (1-3cm sup). We use a set-up workflow similar to most posters on this forum and CBCT everyday. We are seeing some bony mismatch but a very small amount. We have gone through all the steps and are a bit stumped why it is consistently present in a small number of patients.



Any ideas why this might be?



Kind regards,



Paul

[marko_laaksomaa]

Hi Paul

Could you clarify what do you mean with difference in diapraghm level and what kind of bony mismatch, please.

Regards Marko

[michael_tallhamer_msc_dabr]

Paul,
You may be seeing the results in different body mechanics due to different types of breathing during the breath hold

i.e. Diaphragmatic (belly), Thoracic (chest expansion minimal diaphragm drop), Clavicular (upper lung only) or Paradoxical (chest compression during breath) breathing.

You may need to do additional breath coaching with these patients to ensure they are taking the same type of breath as during CT.

A good practice is to tell them to take a slow breath in through their nose until the naturally stop breathing (filling their lung volume without a gasping style breath). Then when they reach max inhale stop there. This requires very minimal effort, fills the lung volume more completely, helps them hold their breath longer, and requires no additional muscle exertion to help keep the breath in.
In that position you can then instruct them to fill “a little bit more” or “let a little out” to dial in the anatomy without fear of them not being able to accommodate as this is a fairly comfortable position for them and with a little extra effort they should be able to accommodate either request.

Hope that helps.

Mike

[marko_laaksomaa]

Hello Paul

Interesting and important finding. Relevant questions with individual patients may be that how systematical those diaphragm level displacements are, is there a heart shift towards the treatment field at the time diaphragm has shifted superiorly, does SGRT give you any extra information of wrong type of BH at the time diaphragm has shifted so that you could correct the error with the aid of SGRT? Here is one publication where the writers have among other things investigated the displacements between apex and diaphragm and they also found more than 2 cm errors between those structures in SI direction and additionally demonstrated this findings significance for the heart location: Geometrical uncertainty of heart position in deep-inspiration breath-hold radiotherapy of left-sided breast cancer patients, Koivumäki et al, 2017.

Marko