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[teddi_lynce]

Good morning,

I am curious as to whether centers are using the CIVCO breast board for their DIBH patients. We have found that we have issues with pitch when we do have the patients on the CIVCO board, so therefore have tried to start using the wingboard instead.  With that being said, our protocol developed by the physicist, requires that we set up to FB but do not set the VRT using OSM, we set the table vert instead.  Then switch to BH and have the patient take the breath and try not to adjust the table vert moving forwards. This was designed due to the fact that the table vert seemed to be more stable then the patients VRT due to the change in pitch daily.  My concern is one, what should our tolerance be on moving the couch vertically to match the appropriate breath hold? My second concern is, if we set up the patient with the wingboard, would it be more accurate to set all parameters, including VRT, with the FB surface then switch to BH surface and have patient adjust breath to match all deltas?

Thank you so much for your input,

Teddi Lynce BS, RT(T)

[marko_laaksomaa]

Hello Teddi

At the beginning of our AlignRT DIBHs we did the setup to FB DICOM surface (also in vertical) and then  switched to BH- DICOM surface and did small adjustments to the couch in SI and LAT based on patients BH. We noticed displacement errors between vertebra and sternum in both AP and SI- directions, indicating the unsuccessful breath hold level. Then also our physicists created a workflow where we do not change the couch vertical value after good BHL in the LAT image together with good FB- and BH- surfaces were found. This is because we have evaluated that the vertebra location in vertical direction remains better the same if the couch vertical is not changed daily based on FB- surface. Thereby the correct BHL, in other words the accuracy between vertebra and sternum is more reproducible. Both vertebra and sternum are locked to certain coordinates. Still the challenge has been the pitch, which I consider is the displacement between sternum and vertebra in SI- direction. This is not necessarily visible in the AlignRT and offline review evaluation has been needed to see how systematic the error is and how to correct it. I think that most of the errors nowadays comes already from the FB- setup, if the patient is setup to more tensed position and this error remains in the BH. It is often said that patient takes the BH wrong, which may be true but several pitch- errors comes already from the unsuccessful setup, which may be due to different setup conditions at the CT. Those are mostly small errors and insignificant in WB DIBH treatments, but as this pitch in SI- direction shifts the vertebra in SI- direction (and SGRT follows the surface) it may have negative influence on WBLN and mastectomy treatment realization in the lymph node area. May be fixation has something to do with this in the random error cases, but  in the systematic cases I could focus on CT- workflows. Do small studies between the fixations and test it on your own how much vertebra location varies daily in vertical direction in DIBH.

Regards Marko

[ellen_herron_bsrtt]

Hi Teddi,

We use civco breast board with a vac loc on top. Through experience, we have leaned that pitch can be translated to the patient needing to slide up or down in their vac loc . Pitch can also be adjust by moving the arm (shoulder) up or down, especially if your ROI includes a sclav field.

We set to FB reference and when all parameters are correctly set, then we switch to BH reference. In BH position our vertical is never adjusted except by having the patient take in more or less air.

My thoughts are if you are trusting the system to tell you the lng and lat positions correctly then you might as well trust it for correct vertical position (Free breath position).

Once you figure out the pitch issue, I would set all parameters, including vert to your FB reference. Most of the time the patients fall right into their threshold when switching to the BH position.

Good luck!

[marko_laaksomaa]

I have an example about pitch from this week with AlignRT DIBH. There was no need to do any small adjustments to couch in LNG and LAT at the time patient was at BH in BH DICOM and arm position was perfectly aligned in the treatment capture in the first two fractions. AlignRT guided the isocenter near sternum and shoulder joint based on AP+LAT images, leading to good accuracy in the tangential image. In LNG direction there was 7 mm residual displacement error to vertebra, indicating pitch. For the third fraction offline review (OLR) evaluation was done. After matching the images in OLR to vertebra, both sternum and shoulder joint were 7 mm too cranially as was also the soft tissue in the tangential image in both two first fractions. This ment that patient should relax her arms and chest wall in LNG direction. On the third fraction we asked her to do so and slightly lowered the arms and pressed the chest wall towards her knees. We went with the same couch vertical and with the same FB and BH surfaces (with tight thresholds of +- 1mm/°, vrt +-3 mm for FB surface setup and +-2mm vrt,+-3mm/° in other directions for BH surface) as former days and patient fell into her thresholds well again. Now there has been only minor displacement betwen the named structures at the AP+LAT or tangential setup images after FB- setup correction was done based on OLR, so possible systematic 7 mm residual error for the vertebra in SI was then mostly corrected. My point was that it is possible that the patient falls into BH DICOM thresholds with excellent accuracy, tangential images are prime but still there can be more than 5 mm systematic error in the spine in SI for the reason of certain kind of pitch. First question is that how much do we finally have to care about that possibility and  how willing we are to hunt that systematic error?  Second question is that can you beat the displacement errors between vertebra and sternum in SI (one aspect of pitch) in the images entirely even with the SGRT without offline review? Most of our DIBHs goes well, but based on results so far I can not be sure that the realization of the lymph node area goes that well that we could go to weekly IGRT protocoll and leave fractions without imaging in WBLN and mastectomy DIBHs. This pitch error is very diverse and patient-specific/individual topic particularly in DIBH and therefore maybe none of us can not give exact answer to solve it entirely. We just bring different kind of aspects from different kind of units to this forum. Personally I consider successful CT workflow more important in this issue than the modern fixations itself, for the reason that I have get that often identical results for the structure displacements near PTV and isocenter variation at clinical studies for the breast patients with different kind of (test) fixation devices.

See: Optimization of whole breast irradiation setup: comparison between two different positioning systems,E. Sanfilippo, 2016.

Best regards Marko

[marko_laaksomaa]

Hello Teddy

It is much possible that with the fixation without tilt (wingboard) there is a possibility that with “averaged couch vertical instead of FB surface vertical”, wingboard is not so sensitive to cause pitch errors/BH level errors in the images as tilted breast board at the situations where patient is in wrong position at the fixation in SI direction without remarkable posture errors. This is because in those situations the vertebra location with wingboard in vertical direction does not change. The advantage of tilted board is for example that the center pod covers larger area of the chest wall in SI direction.

When comparing the workflows between averaged couch vertical and FB surface vertical, the advantage of averaged couch vertical is in the situations when at the FB setup patient chest wall/sternum position in vertical direction is for reason or other as a matter of fact nearer the BH surface than planned. This is what we see in the FB breast images sometimes, please check out AlignRT results in the SGRT forum. With the AlignRT we see this kind of situation between the BHs if patient normal breathing has not recovered back to original values. This knowledge is significant at the CT workflow or at the time FB setup reference is acquired. This kind of situation is possible also with the DIBH at the FB setup and in those cases setup based on surface vertical does not lead to optimal BHL in the images. I think these errors are still mostly systematical and possible to correct at the beginning of the treatment. The advantage of using surface vertical instead of averaged couch vertical is that with both fixation devices it does not matter if the patient is slightly at the wrong position at the fixation if there is no significance  posture errors.

Challenges working with the both setup methods are still the situations when at the FB setup there is more than 3 mm displacement in the FB surface vertical or couch vertical.  Is it for example because of swollen area on the ROI or  is it because patient is at wrong location in the SI- direction on the tilted fixation or should we still setup the patient arms or chest wall…? So far this exceeding of 3 mm threshold in FB surface vertical with our averaged couch vertical setup workflow needs AP+LAT images. Fortunately these situations are rather rare. The optimal case is of course that after good surfaces for FB and BH setup are saved, neither acquired couch vertical or FB surface vertical does not vary at the daily setup.

Lastly there was VMAT DIBH AlignRT patient at this week, whose treatment is at 10th fraction now. We took CBCT some days ago and noticed that there is 7 mm swelling in the entire breast. With the upside down T- ROI patient setup has been accurate now in FB and in DIBH and with whole breast ROI we see that 5-7 mm swelling with the AlignRT also. So in this case additional ROI for the soft tissue gives exactly the same information as CBCT and daily verification is not needed with CBCT. Theoretical, the more our FB setup ROI includes that kind of swelling soft tissue, the more we could have displacement error to the sternum in the isocenter vertical and possibilities to fail in the bony chest wall setup with the roll increases.



If you are interested in to study these things together and get a longer aswer, please send me an e-mail.

Best regards Marko