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Discuss cardiac sparing for left breast patients with SGRT.
By chris_mcguinness

I'm curious if other sites are using auto beam hold for all DIBH breast patients or manually stopping the beam if the deltas exceed thresholds. If you are using auto beam hold what tolerances are you using for DIBH breast treatments? Do you use different tolerances for an APBI patient compared to a whole breast patient? What is your policy for patients who often exceed tolerances causing the beam to trip frequently during a treatment? That is, do you loosen the thresholds so they don't exceed them, or do you turn off auto beam hold for those patients and allow RTTs to visually monitor the thresholds and beam off if necessary? Is there an upper limit to how much you will loosen the tolerances? And finally, if you have had challenges using auto beam hold for certain patients have you figured out ways to improve things so it is more reliable other than simply opening up the tolerances?

Thanks for help with all these questions and for sharing your experience!

By stephen_davison
Hi Chris, we use the standard 3mm/degree tolerances, which work well in the vast majority of patients. If a lady is struggling to hold the breath hold reliably we will widen the tols up to 5mm. We've never turned off the beam hold and I cant see us doing that at all. We've not had a situation where extra coaching, or widening the tols hasnt worked
Same 3mm tols used for all patients
We spend a lot of time at pre-treatment assessing if the patients can reliably hold breath hold, and will exclude those who cant.
The only other thing we've found is adjusting the ROI can help, but its very patient shape specific.

Sorry I cant be more help

Stephen, Inverness
By muenster
Hello Chris,

we use the 3 mm/degree tolerances as well. It works for all patients with very rare exceptions. We also don't widen the tolerances. Turning off the beam hold might occur in very rare circumstances, where the Gantry Position blocking an Align RT camera might cause a "false" beamhold.

After having similar starting problems as you mentioned, we started to implement a "training appointment" before the planing CT. At that seperate appointment we position the patient on our treatment board and show how we excpect him to breathe and how he can train this at home. This helped a lot to better the quality of our planing CT's by achieving a higher distance between respiratory center position and deep inspiration height and having less nervous patients who can follow the commands way better.

This also enabled us to filter better for patients that are unsuited for DIBH treatment, if they are unable to achieve sufficent inspiration lenghts/durations or too small differences between respiratory center position and DIBH for a real treatment benefit.

Our ROIs are L-shaped and include the whole treated brest, front and side, excluding Arm/Axilla, with a connected stripe below both breast across the body. After our current experiences it is vital for the ROI to function properly to not include the other breast if not also treated.
By lindsey_fox
We always use auto beam hold for DIBH breast patients. This is nice when someone is borderline out of tolerance and they flicker back and forth across the threshold, our TrueBeam will not only auto beam hold but also auto beam on once they're back in tolerance. That way the therapist can verbally coach the patient to breathe in a little more and continue treating, without having to beam off, let the patient breathe, get them back in breath hold, mode back up, etc. Of course, sometimes the patient does need a break and will have to free breath for a while before continuing. If someone can't get back in tolerance, the therapists will re-setup the patient by lining them back up to the free-breathing surface, then get them into breath hold, and if they can't get quite back into tolerance on the breath hold surface, they will adjust the couch to get them there. We use 3mm/3deg tolerance and we don't open it up for DIBH patients. This way we know the breast/target is at least within tolerance. If we get a patient that can not reliably repeat the breath hold or constantly struggles to maintain it, then it's time to talk to the physician about whether or not the patient should be re-planned on the free breathing scan. However, I think this can be avoided with good education, patient practicing the breath hold before sim, consistent coaching (exact same verbal cues) between RTTs, and screening during the sim to determine if the patient can hold their breath for at least 20 seconds (less than that and they won't make it through a double-exposure portal image.)

We use the same tolerance for APBI, however, we treat those in free-breathing because our physician wants to align those using CBCT, and we're not confident in the accuracy of AlignRT during a CBCT with the imaging arms out. (If someone knows how to do this, let me know!)
By chris_mcguinness
Thanks for the responses everyone. Lindsey, you mentioned issues using AlignRT for CBCT where the imaging arms are out. A similar issue I've seen for VMAT or IMRT breast treatments is the deltas change as the gantry blocks the camera on the ipsilateral side. Our strategy has been to increase the ROI to extend beyond midline and include some of the contralateral breast. Have others tried this and is that a recommended solution to this issue? Would it be possible to create a separate ROI to use during the CBCT in a similar way? With both kV arms out it might obscure the cameras too much to compensate with a larger ROI though. Has anyone tried that or found ways around this issue?
By peter_park United Kingdom flag
Hi, in my clinic, we are preparing to use Elekta Response (Auto Beam Hold) with AlignRT on SBRT patients (Lung and Liver). Is there anyone out there who has experience doing gating treatment or breath hold treatment using the similar system? One of my concern is that often, during VMAT delivery, there are specific gantry angles where AlignRT loses it's signal (not so much of an issue for a fixed beam treatment like breast). Usually, if manual beam on/off is used, therapist won't stop the beam moving through that specific sector. However with Auto Beam Hold, I'm afraid that the beam would always get stuck in that sector making smooth delivery difficult. Any feedback would be greatly appreciated.
By muenster
Hello Peter,

we are currently using the exact same setup - Elekta Linac/Versa HD, Align RT + automated beamhold and VMAT/SBRT treatments in the chest/upper body - though not yet on Lung/Liver. In our experience an automated beamhold caused by the gantry position can be almost completely avoided by planning the Treatment ROI accordingly. If the System has enough body surface to register the patient, the gantry will not cause too much of a difference in the translations/rotations to cause a beamhold. This of course has effects on the framerate and the automated beamhold if it drops below around 5 fps. So don't make the ROIs too large and keep an eye on the fps. The ROI should cover both sides and the front of the patient and have enough size and meaningful structures to register properly. Working with breath hold allows to work better within narrower tolerances (here 3 mm/3° in Align RT, though we try to get as close as possible to zero before starting CBCT/treatment). But with a good ROI this also worked easily with free breathing and a gated reference capture. Try to avoid including structures like arms/axillae/chin that are too ”moveable” for the ROI. If in doubt use the treatment capture/postural video function to confirm the position of the arms. Hope this helps a bit.
By stephen_davison
We've had issues with this when using MV/kV pairs, so all the arms are out at the same time.
Advice from vision RT was that if the arms are blocking the side cameras, then your ROI needs to reflect what the Front camera at the feet looking down the bed can see more than the other cameras. I tried making my ROI bigger initially and all it did was make the area the cameras couldnt see bigger! If it cant see a certain percentage of the ROI, it just gives up!
Try using an ROI that the front camera can see, like an inverted T to include the sternal area, and under the breasts, but dont go around the sides too much where the front camera cant see. Dont go too high up the sternum or the camera cant see the chest dipping away either.
As with most SGRT things, its the ROI thats critical, and especially in these cases varies from patient to patient depending on biody shape and whats being obscured from the cameras

You can also create an imaging ROI so that you only use this when the arms are out, and you can go back to the normal treatment ROI once imaging is completed so your ROI reflects what your actually treating. (when drawing on your ROI, theres an option to ADD SELECTION to achieve this).