SGRT Forum

We have been performing SGRT using OSMS and AlignRT at our institution for about one year, primarily for breast radiotherapy. My therapist team recently asked me if it would be OK to forego the addition of isocenter skin markings during the first first fraction any instead rely on SGRT for daily alignment.

I have been going back and forth on this. When I think through our treatment procedure and the way we verify the accuracy of the reference surface, I am comfortable that we do adequate verification that our reference surface produces good alignment internally as well. That said, no software solution is infallible and I like the idea of having a simple back-up way to verify positioning. Perhaps this is doubly important because the SGRT system we use (AlignRT/OSMS) does not have a convenient, off-line means to audit the day-to-day use of the system. In the absence of a way to monitor quality off-line, the use of skin marks as on-line QA of AlignRT/OSMS seems really valuable to me.

How about all of you? What do you do at your institution, and how did you arrive at your decision? I would love therapist and physicist input.

Dustin

We are actually in the process of going completely markless at our center.  Although we don't use marks for our breast patients we still verify medial SSD and light fld daily before treatment. We also move to our table parameters first as a general guideline for setup (every patient for ALL setups are indexed to the table). With these 3 checks along with the accuracy of VRT on breast patients we have concluded marks are no longer needed. If we every have a doubt or question about anything then we film to verify, same as we would if we had marks. If your therapists are on board, then go for it!

We have gone markless and tattoo less with the introduction of AlignRT.

I think your question Dustin is a sound one, however may I invite you to think about this slightly differently?  Drawing markings and SSD's on the patients skin I guess is fine if you then image and do not move your couch based on that image.  Do you only look at images post radiation delivery daily?

If in fact you image and shift prior to delivery per fraction those marks begin to mean less and less.   If you image and shift, do your therapists then re-enter the treatment room and re-draw the position of the fields post imaging?  For me the anatomical position of the fields is key, the SGRT system is a tool to help to get you very close to that and then monitor during delivery of the radiation.  You know you will be in the correct position as your imaging shows you this.  You can also check coverage/swelling/weight loss from your daily cone beams.  I think its more a protocol and process shift to drop your markings.

To make yourself happier could you audit the first fraction of say the last 30 patient XVi's and table shifts post imaging?  We also use a skin render from CT for a visual check on fraction 1.  Very happy to talk through our process if this will help at all?

Half a year after the introduction of AlignRT we have gone markless and tattoo less as well. I fully agree with the good arguments of Jacqui. Skin marks will never be a good and satisfying landmark for precise positioning. We used them, because we had no alternative. Now we have one! AlignRT, as the skin marks, serves as a "first guess". For precise, final positioning we still use daily kV-kV imaging and correct position based on anatomical matching. First data show that the "first guess" by AlignRT is in most of the cases already a good one!  In our institute we have two dosimetrical identical machines and both are equipped with AlignRT. So in case of a technical issue with AlignRT we still can continue to treat patients on the other machine. I guess with the introduction of new smart technology in our clinics we should also consider to give up some old "technology" like skin marks to the benefit of both, patients and RTTs!

Thank you everyone for your thoughtful replies!

Some of you have referred to scenarios that involve daily radiographic imaging and CBCT. In these situations, I agree that skin markings are not necessary  because the surface guidance is ultimately confirmed (or overridden) by radiographic imaging every day.

My main concern is for patients who do not get radiographic imaging on a daily basis. I think Ellen gave a great answer for this one, a combination of indexing and a quick SSD verification makes a great redundant positioning check in addition to SGRT.

We are going completely markless in October.  We are having a problem with some abdomen set ups, what does your ROI look like on an abdomen.  We have tried a few ways of drawing the ROI but none of them seem to work well.

Well, I am afraid that all of us will be confronted with problems with abdomen setups. This is inherently related to the technology used. If you have a flat surface, or one with few structures in it, like a flat belly, then your system cannot find a proper solution (in longitudinal direction) and you always have to caution the proposed solution. But "fortunately" not all bellies are flat... But even then it is probably still near impossible to provide universal guidelines on how to draw you ROIs.
I try to provide a few hints that might help....
- Don't include in your ROI any clothing or hairy regions.
- Don't include in your ROI any "artefacts" or parts of body structures which might not be contoured in a coherent way in your ROI, e.g. stoma
- Important. Try to move your patient to the proper treatment position without using AlignRT. You need to have a good undertstanding of the location of your isocenter. Then, with the help of anatomical landmarks and your room laser you can find the position within a few cm. Use AlignRT for the final fine tuning of the position. But be aware that the longitudinal position might be wrong by even >10cm. So always use "common sense" to validate the final position and it might be best to verify with kV-kV imaging.

If you provide me your email, I can send you a few sample ROIs.

Hi Daniel,

We too have been using Align RT for quite awhile but have kept with status quo with skin marks still on patients. My boss wants hard data on the accuracy of align RT before we can do away with skin marks all together. You said that from your "<span style="color: #515151; font-family: 'Hind Vadodara', sans-serif; -webkit-text-size-adjust: 100%;">First data show that the “first guess” by AlignRT is in most of the cases already</span><span style="color: #515151; font-family: 'Hind Vadodara', sans-serif; -webkit-text-size-adjust: 100%;"> good". Can you quantify your "good". What analysis have you done so far? </span>

Would love to hear.

Tanya

Hi Tanja

as mentioned, for final positioning kV-imaging is (still) our gold standard. We do kV-imaging for every single fraction. So it is important to understand that we use AlighRT (as a substitute for skin marks) for initial positioning before kV-imaging. To find the proper position quickly it helps to have pictures of the patients from CT with the laser projected on the skin to indicate the location of the isocenter.

To convince ourselfs that AlignRT performs at least as good as skin marks (for initial positioning) I analysed performed delta shifts resulting from the kV-image match with refrence DRRs for about 700 fraction for patients we positioned initially on skin marks and 700 fractions for patients initially positioned with AlignRT only (to do so you can skill mark your patients, but don't use the marks). The analysis of our sample shows comparable results, slightly better for AlingRT. As with skin marks, AlignRT performs not always in a perfect way and proper selection of ROIs is crucial. But we can conclude that AlignRT only based initial positioning before kV-imaging is as reliable as skin marks and outperforms skin marks often with difficult cases. Given the large benefit in confort for patients as well as for RTTs when omitting skin markings, we decided to go markerless. Once again, we don't say, for the moment, that AlignRT can be used to find the final (treatment) position without kV-imaging. This will anyhow never be possible for internal moving targets like e.g. prostate. I guess it is understandable that one has to convince himself that going without skin marks is reliable and safe after we have used skin marks for decades. But it is worse to do so as the advantages, and the gain in time, when going markerless are really substantial.

In case you are using Aria, you can extract the delta shifts quite easily from Oflline Review. I will present some of the results at the upcoming SGRT users meeting in London.

I hope this helps a bit.

Daniel

Good morning Daniel,

I would be really interested in seeing your numbers and was wondering if you had published this data. We are at the very outset of the SGRT pathway and looking for initial data to justify the investment.

Many thanks,

Becky