SGRT Forum

Hi

One of the most challenging tasks in the (SGRT) setup seems to be to correct plus- signed pitch of the chest wall. The reasons for this in systematic cases may lead to CT workflow (see. Intrafractional baseline drift during free breathing breast cancer radiation therapy, 2017). Anyway, what kind of tricks do you do in the setup to relax (or press towards couch) the caudal part of sternum?

Regards Marko

Are your patients setup on vac loc/wingboard or breastboard? If so, pitch can be corrected by having patient move up in their vac loc or down in their vac loc. Sometimes pitch can also mean treatment side arm needs to come up or down a little.

Hi Ellen

Thank you for your reply! We use breast board with couple degree tilt. We have also noticed that in a tensed patient position typically both sternum and the arm are too cranially in the setup images in contrast to vertebra. In some cases we get this information from AlignRT as pitch, some cases not (therefore daily Offline review is still in use). In some cases despite we get this information from AlignRT, it is difficult to correct this pitch. Is it in those cases because it is difficult to copy in the quick patient setup the DICOM position that is acquired at the moment patient is naturally relaxed with the couple minutes delay time?  Seems like the situation is inversed the same in the BH cases: if FB VRT/DICOM surface is acquired at the position patient has just taken several BH:s, it may be diffucult to copy this tensed position in the setup process. These kind of things we have focused on a lot, but there is still work left with these things.

Regards Marko

Hi Marko,

We set up our patients on a breast board as well. We were originally seeing a lot of pitch variance in our port films prior to having Vision RT. One of the things that drastically helped or assisted in fixing the pitch was getting new breast boards/tightening the brackets on the existing ones.

During simulation prior to scanning or having the physician come in we have the patient bring their arms up into the treatment position. We have them try to relax into the table. We then call the physician in, this gives the patient enough time to focus on just letting themselves sink into the table. Once patient's borders are marked we have the patient bring their arms down and wiggle a bit and then bring arms back up.

From sim we are given a nipple line/ML number which coincides with where the laser falls on the side ruler of the breast board (verifying that both sides of the board are marked the same). This helps with sup/inf positioning of the patient which assists with pitch as mentioned by Ellen. Something else to consider is when using Align RT we have found that adjusting the patients rotation and roll to be as close to zero, helps with getting less of a pitch. We do rotation and roll first, then translations and if pitch is still not within tolerance we adjust patient up or down on the board.

Sorry for the lengthy reply. Hope this helps. :)

Hello Jotsna

Thank you for your reply. Interesting information about fixation, it still seems to have impact on entire process. Good idea to bring the arms down and even ask patient to sit down just before CT. It may help the work at the future setup process. We also use indexing values in the fixation- middle tattoo mark should meet the measured value (measured at the CT) at the fixation.

The specific case I tried to explain was that when the patient is at the treatment couch and laser is at the indexed value, then middle tattoo mark is too cranially in comparison to laser. AlignRT shows +pitch, (as it should show) and LAT setup image shows that sternum is too cranially. What do we do? If we ask patient to go up or down, in my opinionm pitch remains the same. Gently press to the lower part of sternum helps a bit but not entirely. We will continue with this in practice and let us know what happens.

Regards Marko

Hi

Last week there was a patient case which fits well to this topic. FB breast treatment was the case. kV/kV imaging was berformed, no couch shifts were needed with  DICOM surface setup, all the bony structures were perfectly aligned in the images. Then some errors appeared to machine software at the time treatment was supposed to begin. Patient was at the setup position during the delay time. It took about 7 minutes and we were ready to continue. New images were acquired before treatment. AlignRT DICOM RTDs were shifted during that delay time such that VRT  showed -0.4cm, LNG was +0.4cm and PITCH was now +2. In the kV/kV images sternum was shifted 0.4cm towards vertebra and 0.4 cm caudally in comparison to vertebra, lower part of the sternum was ventrally than the upper vertebra. All the AlignRT values were then seen in the images in this case. Addition to those shoulder joint was shifted 1 cm caudally during that time. If we think it that way that this new position would be a position in DRR (acquired at the CT), one could not entirely copy that kind of patient position at the treatment setup no matter what. The good thing was that surface guidance device showed everything right what was happening for the patient position during that time and gave support for the knowledge that intra-fractional errors can be related to time and this may have effect to the inter-fractional error if this delay has happened at the CT.

Regards Marko

Just curious if your center has tried setting the patient to the same table parameters from their initial treatment verification check before the first treatment? We do this and you can tell if the patient needs to go up or down based on skin marks. Also, we find that sometimes the shoulders are shrugged and relaxing them can help. Another solution that sometimes works is readjusting the knee sponge placement. We like to use the video feature for set up. If you don’t have the newest upgrade you can take a treatment capture to see a snapshot of patient position- ex: arm position. The green surface is how they are that day in comparison to the pink at simulation. Lastly, depending on your process, the patients gown can block part of the cameras from seeing the ROI and may need to be moved to expose more skin. Apologies if you already know this and have tried all of these strategies. I hope this helps!

Thank you for your reply. These all are very good things to do to relax the patient at the setup which are mentioned here in the answers. However, these systematic displacements (sternum pitch, sternum displacement vs. vertebra in AP or CC direction, arm position…) are at least partly related to difference of the time patient lies at the couch on the fixation device at the CT and at the linac, before imaging: Intra-fraction motion monitoring during fast modulated radiotherapy delivery in a closed-bore gantry linac - ScienceDirect, Intra-fraction respiratory motion and baseline drift during breast Helical Tomotherapy | Elsevier Enhanced Reader. But yes, we have relaxed the shoulders, asked the patient to relax, used acquired couch parameters together with AlignRT, have new breast boards and so on. To ask patient to sit up for a while before scanning at the CT could help. I think we all have these challenges in our daily practice, more or less. Different kind of bending of the couch at the linac and at the CT may have slight affect to pitch error?

Regards Marko

https://www.sciencedirect.com/science/a ... 0622#b0045
https://reader.elsevier.com/reader/sd/p ... 1205111117

So, based on those informative studies it is no wonder, if at the setup, after automatic drive to the planned couch parameters at the linac (takes 10- 20 sec from the moment patient was placed onto fixation), patient surface in FB shows displacement in AP (patient sternum is too ventrally compared to vertebrae) and in PITCH? if it is compared to FB DICOM surface (taken possibly after 10 minutes from the moment patient was placed onto fixation at the CT). Then there may be a need to “artificially” relax the patient at the setup. Fortunately we have AlignRT to show these kind of things to help us to improve our workflows, daily positioning and treatment accuracy.
Marko