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Discuss cardiac sparing for left breast patients with SGRT.
By julie_morzy
It has been our experience, that we sometimes struggle with arm position and surface aligning simultaneously. Our physicians have requested to correct arm position prior to treating. When setting up our patients, all deltas are in tolerance allowing for us to believe the system is doing its job. Our physicians have written on the RX to image daily prior to treating. At this time , we physically move the arm position and treat in DICOM not creating a daily VRT. For those of you who image daily, what images are you taking: KV pair? , MVpair?  SCV and MV tangent, etc.? And then are you just applying the shifts based on bony anatomy/ and surface?  and capturing a VRT? Looking forward to some feedback. Does any other institution struggle with this? Thank you.
By marko_laaksomaa Finland flag
Hi Julie

The most important thing in the RT setup is to daily achieve the posture and the position of of the patient in the setup image to correspond the position and the posture of the patient in the reference image, as accurately as possible. In the breast case optimal situation is such that the entire bony structure on the chest wall (including vertebra and shoulder joint) and the breast tissue should locate typically inside +- 5 mm accuracy, depending on hospitals IGRT tolerances. At the time AlignRT has led the accuracy inside your given IGRT tolerances, you can rely on the system and skip the images or take only tangential images to just verify the accuracy. We sometimes have situations that we have to perform daily AP+LAT imaging protocol, since there is that much variation in the patient posture or isocenter. In FB breast cases this is not a problem with AlignRT. However, also in FB cases the goal is to go with the tangential images only, since it is 2-3 min. faster than AP+LAT and 4-5 min. faster than AP+LAT+tangential, which protocol is needed if there is displacement of the structures in the AP+LAT images and thereby difficulties to select the correct location for the online match and the couch shifts (which we finally want to lead to good accuracy in the tangential image). In addition, in some cases we have noticed that the system itself (with good setup and with good setup surfaces) can be more accurate than the rtts online match corrections based on AP+LAT images, to lead excellent accuracy in the tangential image ribs.

In my ideology, I prefer DICOM as a gold standard, just like your physicists. Still, rather often we notice that for reason or another we can not go on with the DICOM setup, since that much often we rtts notice it to lead small but annoying systematic errors, noticed during the first three fractions. The systematic errors can exist in the arm position, isocenter, vertebra rotation, displacement between breast and the bony structures, what ever. Based on the ROI comparison, the assumption that we have wrong kind of ROI and that is the reason why we can not stick with the DICOM seems not relevant. There is cases (not investigated how often) that we have to skip DICOM and acquire new surfaces for the setup. We have found that the arm position correction is easier and more accurate with the treatment capture than with the arm ROI. Which one do you use? In general I would like to setup the arm with the treatment capture where we see the entire arm up to the wrist, and also therefore I am not afraid of taking VRT surface for the setup. DICOM ends to mandibula level in CC direction

Now in your case you may need to find out is this arm position problem systematic or not, use offline image evaluation. If it is systematic, you could at the setup process with the treatment capture leave the arm to the posture you have found optimal (there is now offset in the treatment capture in the arm position or in the arm ROI delta towards the direction you evaluated from the images offline earlier) and if it was now ok in the images and everything else in the AP+LAT images was ok, acquire new gated reference capture for the next day setup. Verify with the tangential image that the soft tissue locates in its correct position also. Use this as a reference for the next day setup and acquire still at least once more AP+LAT (+tangential) image. Of course this procedure to acquire new reference surfaces and/or to verify the accuracy of new reference surface in the next day setup should in optimal cases be based on CBCT, where you can verify everything at the same time and even more reliable, but for example with the Varian linacs CBCTs you can not see both entire lymph node area and the soft tissue entirely with one scan at the images due to limited field size in CC direction, as far as I know...

So, do not consider DICOM as a gold standard for the setup, in the cases where it clearly leads to systematic errors in the images. RTTs are the one which daily setup the patients with the system and daily check the images online, so we are the best experts to say which part is working in those processes and which one is not. So bravely say those ills that you have noticed in the workflow in the meetings and discussions with the physicists, since finally the shared goal is the practical and accurate RT.

Thanks to this forum, we have been able to take along the workflow where we use one DICOM or VRT reference surface for the setup and go to the other field to acquire daily reference surface there for the treatment, no matter did we shift the couch based on online match or not. Hopefully you get other answers also and hopefully there was something useful. Have a nice day.

Best regards Marko
By stephen_davison
Hi Julie, we're tattooless with our breasts, so we position patient on couch, eyeball them straight and set to our expected couch positions (derived from CT plan).

We then use Align . We'd correct any gross rotational error, then get couch deltas as close as we can. We then take a treatment capture to check arm position and double check hip position to fine tune the set up. We then go back to monitoring and fine tune deltas again.

One thing we struggle with is pitch occasionally, so if its an issue we get it as close as we can and see what the images look like.

We use MV glancings for imaging unless theres an SCF when we'd also do a AP/PA kV. We are discussing changing the imaging to possibly an angled kV pair. We match to chest wall primarily, but with an eye on the breast contour as well.

Any shift from imaging we take a VRT for that treatment only. We try to stick to the DICOM surface if possible. If we find a consistent imaging shift we would then use an appropriate VRT for daily set up, which would be confirmed by imaging for 2 consecutive days. If those are all in tolerance, we'd then go to weekly imaging. We also take an MV during image daliy to keep an eye on the set up offline. Any offline check 0.4cm or more would trigger pre-imaging again.

Seems to be working well, and anecdotally, we're manually handling the patients much less. (I guess we're not just pushing tattoos and skin around as much?!)

Any questions just ask

Stephen, Inverness