Optimizing Breast Setups in Proton Therapy Using SGRT

Transcript:

So, some learning objectives. We’re going to do an overview of our proton therapy center, and then we’re going to talk about the role SGRT plays in ensuring accurate patient setups in proton beam therapy. And then specifically, we’re going to talk about our breast workflow. Then we’re going to talk about some challenges and how we overcome those. And then we’re going to talk about some benefits, and then summary at the end. Let’s get started.

So, some background information, some key terms, and knowledge to get you all informed and understanding. So we have 180 degree Hitachi ProBeam gantries. We have four different treatment rooms and one proton beam. We have a six degrees of freedom couch, which you can see here is attached to a robotic arm. This is the gantry. This is where the protons come out of. We have our X-ray panels here, and we have our X-ray tubes built into the floor, and so we have oblique X-ray kV imaging.

Over here, we have our CT scanner. So what we can do is called CT onrails, which is where we move the treatment table over to the CT scanner, do a quick CT scan, and then move the patient back over, and we can realign them using our planning CT scan and the CT scan from today.

So, something to note, we do still use tattoos. I know, it’s a hot topic today, and we hopefully will soon be moving away from that. We do use UV tattoos, which are pink in color, and we have a black light that our therapists use daily to help line up the patients. They are less noticeable, but nonetheless, they are a tattoo. The reason that we do this is because not all of our patients that are simmed for protons actually get proton treatment. You guys probably know with insurance, all that lovely things. So because our patients can potentially go photons or to our regional sites, we do have to tattoo them in order for those other sites to treat the patient because those sites do not utilize SGRT, unfortunately.

Patient immobilization. Our breast patients are positioned on an index breast board with a chin mask in place and a small back lock used for immobilization. So whichever side of the breast that we are treating, that arm is raised up above their head holding a handle, and the opposite arm is at their side holding what we call a slhandle or a slanted handle. These are all going to be indexed to the table for consistent positioning, and it’s helpful for us once we get into our SGRT workflow. Something to note here is that our bilateral breast patients are immobilized in a five-point mask. So what’s important here is that we do not include the ROI when importing SGRT to cover the part that is above the mask. So we only want to encompass the tissue that is below.

Fractionation. So what I’m going to consider our standard breast will be our press chest wall with or without nodes. This will be 15 fractions, and those patients will have a chin mask and a back lock for immobilization. Like I said, our bilateral breasts, these are going to have a five-point mask. And then our partial breast PBIs, these are going to be three to five fractions, but something to note is they will not have any patient-specific immobilization. They will still be on the breast board like our standard breast, but without that patient-specific immobilization.

So some key terms here. We have Setup 270. This field is used to establish the patient’s treatment position. This is where we take our X-rays, where we get the patient on the table, kind of loaded up and everything looking perfect before we begin treatment. So 270 is referring to the table angle. Like I said, we only have 180 degree gantries, so we have to move the table to different treatment angles.

So then CT Sim/DICOM Body Only. This is referring to the patient’s external anatomy. This comes from the treatment planning scan, and we will see that in a few moments here. And then the ROI, region of interest. This is created based off the body only, and this will encompass the treatment area.

So why is SGRT useful? So this helps us make sure that the patient is lined up, and where we have lined them up post X-ray alignment, they will stay in a certain threshold before delivering treatment, and especially during couch rotations. So this will monitor the patient’s position relative to isocenter at each treatment angle and ensuring rotations like table 180 to maintain isocenter alignment within four millimeters translational and three degrees for robotics. And again, this three camera infrared system provides continuous surface tracking during treatment and detects drift from isocenter instantly. And especially before beam delivery with having four treatment rooms, we do have longer beam wait times, and so making sure that the patient has not moved during those long beam waits is crucial for us to have an accurate and successful treatment. Overall, these principles show that we use SGRT to enhance confidence before and during beam delivery and ensuring that we will have the most accurate treatments.

So, this is our standard screen. We’re going to do a little overview in parts of the tools that we use daily for breast treatments. So up here, where we have this little person icon, we’ll have the patient’s name and date of birth, and potentially their MRN number. We will have the play button here, then we have the treatment plan. So you can see this patient has had two replans. This is the initial planning scan. We call it F1, which stands for fraction one, breast left. So each replan a patient has will create a different CT Sim DICOM body-only structure because, again, it’s based off that initial CT scan.

Then over here, we have the CT Sim body only. That is going to be the purple pixely outline of the patient. And F19 breast, this is our ROI name. So this is coming from the plan that they are on, and this is going to be the white structure here. To the right, we have our vert, long, lat, magnitude, yaw, roll, and pitch. Our translationals are going to include our vert, long, and lat, and then our robotics will be our roll, pitch, and yaw. Down below, we have our surface deformation and video, which we saw earlier during those presentations. Reference is for post x-ray alignment. Treatment is comparing our patient’s current surface to that treatment planning scan, and then couch 270 is referring to the table angle that the patient is at.

So how do we implement this into our daily breast standard of practice? So this is all before x-ray alignment. I just want to emphasize that. This is going to be whenever we get the patient on the table at setup 270. What do we do? How do we do it? Why do we do it?

So initial setup, we’re going to start with that setup 270 field, and we are going to align the patient using tattoos and room lasers. Then we are going to shift the couch to its planned iso-center. So those are from our dosimetry team and our patient’s information note. Then we’re going to use the SROT surface capture. We are going to select the treatment button. Then this will compare the live surface to the reference CT Sim DICOM body only. So now we’re going to evaluate what it looks like. So for translation tolerance, we have four millimeters. In robotics, we have three degrees. Then we’re going to apply these corrections and therefore manually adjust the patient if needed, if it’s over three degrees. Then after we’ve made these adjustments, we will do another treatment capture, which will then hopefully all look fabulous. Then we are able to step around the corner and take x-rays.

From the last talk, we talked about the postural video, so we use that as well. This helps us before taking x-rays to hopefully help aid with visualizing the arm positioning, because that can be a bit of a struggle. Even though the patient is in a vac lock, this can still be helpful in helping consistency of arm placement during setup, and it reduces time by minimizing the need for repositioning. So as you can see here, we have the three different cameras, and you can see the different longitudinals or intra-post, you name it.

So post x-ray alignment. So our x-ray alignment, we are lining up to the chest wall, sternum, anterior ribs. We’re looking at the arm. We’re looking at potentially the chin to make sure that eye is up and out of the way for treatment. So we have the process on your right and the purpose on the left. Our auto-selected ROI is going to be ensuring that the correct treatment plan is selected. Then we’re going to enable that play button, which is going to activate real-time surface tracking. Then we will select deformation, which was at the bottom next to surface and video. So the deformation is going to give us a percentage. So this is going to let us know, because we cannot see soft tissue on our x-rays, what does that actually look like compared to the actual treatment plan that the physician planned. Then we’re going to analyze this. We can see some different colors. We can see green, we can see red, we can see blue. We’ll get into that a little bit later, okay?

So then we’re going to view the results, identify the magnitude, and the location of the surface deviation. Sometimes we can run into troubles, which we’ll get into later, but we will also report screenshot. So this is big because it gives our physicians the ability to see what exactly we are treating on a day-to-day basis. So this is super helpful if the patient is getting a replan and the physician’s like, “Hey, could I possibly pull up these documents?” And we can easily have them at their reach at any moment. So the physician could evaluate for a replan and decide if the deviations are consistent enough to justify a replan. So seeing if this is a daily issue or whatnot.

So this is going to be an example of a report screenshot. So this is exactly what the physician will see whenever they ask for those documents or pull up that file for the patient. So again, the patient’s name would be right here. You can see that the play button is pushed here, which is why it’s now a pause. We have the plan name, we have the ROI. We can see that these are all within our tolerance. They are within the green. Again, our translationals are going to be four millimeters, and our robotics are going to be three degrees.

So basically, whenever we press deformation, this little box will pop up. This will show what we’re mainly focused on is the percentage here. We obviously want that closer to 100 as possible, but we understand that over 85% will still be an accurate treatment. And something to note here is that this is a standard breast. So this patient’s currently on fraction 19, and the tolerance limits for this patient’s treatment are going to be above and below five centimeters. So you can see this is all green. Fabulous. Then we’re going to come over here to the corner and we’re going to report screenshot. So just by pressing that button, it will automatically save to our database for our physician’s review.

Now, this is an example of a PBI. The key thing to note here is that everything is the same over here. We have the patient’s treatment plan. We have the name of the ROI. We’ve pressed the treatment button. Now we are looking at the deformation. Again, this top percentage is at 90%, which is pretty great. And you’ll notice here the tolerance limits. So these are going to be above and below three millimeters. So this is adjustable for us to move based off of what the patient’s treatment is. And as you can see, the CT sim body only is kind of adjusted. So we can do that because it is a 3D structure when it is imported. So we can get a better view, especially if there’s any color mapping or whatnot. We can get a better view and see where that is. And again, you would report screenshot, and it would go to the physician for treatment.

So some problem-solving color mapping. As you can see here, we have some red and some green, and you can see our VER is out of our tolerance. And in the top corner here, our percentage is looking around 54%. So that is not treatment approval okay. So what we can do from here– So let’s explain a few things before we get too excited. I’m excited.

Red means there’s too much tissue. Blue means that there is a lack of tissue. So concerns a large area of red or blue within the ROI suggests that the breast position is not in the same position. So striations can also occur. What is striation? It’s almost like a lightning bolt within the ROI. So what you can see is almost like a zebra print of red, blue, red, blue, red, blue within the breast. So this is very concerning, and the physician will most likely be called because of this. So we do not take this lightly whenever we are analyzing these before treatment.

So we’re going to have issues because of a flip magnet. Magnets are used for our breast patients with implants to help the nurses or whoever is filling those with solution, help locate that, the breast position differing, or sometimes just patient movement. So normally what our go-to steps are, if the percentage is below 85%, we will– So the steps here, we press play, we’ll analyze. We’ll see that the stats are below our 85% threshold percentage. Then we’ll take an additional X-ray. Sometimes the patient just moves, and that’s okay because we can realign and get them back into the right spot, or we can potentially call physics for guidance. So our physicist would pull up the plan and external beam and analyze the discrepancies within the ROI to see as if they feel it is significant for their plan, or we can just continue on like normal. The physics team will also make a note of this, and so will we in our treatment log to journal about this, so whoever is treating the patient next could know beforehand.

So how is SGRT beneficial for patients and therapists? For patients, there is no additional dose during setup. So we do still take X-rays post initial setup, but this hopefully will minimize that by getting us closer to that isocenter alignment, and it’s improved patient positioning. So actively comparing the patient’s current surface from today to that initial planning scan will hopefully give us that perfect, most accurate alignment that we can, and it lets us see better soft tissue alignment. Again, we cannot see soft tissue on our X-rays, unfortunately. But this gives us a window into, okay, if we did, this is what it would look like. More consistent arm and body positioning, again, using the postural video that helps us aid in positioning an arm for treatment, and then reduced risk of setup errors. So sometimes with our breast patients, they are indexed differently on the table on whether or not they’re photons or proton simmed. So sometimes getting those gross errors out of the way or realizing before we take any X-rays that we need to adjust something, we can easily without giving them any extra radiation.

And for therapists, so this allows us to set up without solely relying on X-ray alignment. So it gives me peace of mind, especially coming from a photon background of being like, “What? We can’t see this.” And it’s like, no, we have this software that we can use that will give our therapists confidence and allow them to see what exactly we’re treating a little bit better. So then we can see the patient from multiple angles simultaneously, while also this is used pre- and post-X-ray alignment. We use this also to monitor the patient during treatment. So after we’ve analyzed the deformation, after we’ve reported screenshot, then we will take a reference, which will then capture the patient’s current surface and make sure that they are perfectly aligned for treatment. Also with the postural video, we could use that for checking clearance. So even though we are checking clearance with the table, patient, and the gantry while we are in the treatment room, it’s also helpful to give you peace of mind if they were to move because yes, the breast that we are treating is the ROI, and that’s what we are most focused on making sure is not moving during treatment, which leaves us room for error when it comes to the patient’s arm. So they could move their arm whenever we are outside of the treatment room and us not necessarily catch that. But we can turn on our postural video during treatment and make sure to see if the patient has moved or not. And then it supports efficient and reproducible setups. So again, using the CT sim DICOM body only, we are coming directly from the patient’s treatment planning scan and today’s current anatomy and comparing those and making sure that those line up perfectly.

So to summarize, SGRT is used prior to X-ray alignment using the treatment button, which would compare the patient’s current anatomy to that initial CT planning scan. Then it’s also used post X-ray alignment by pressing the play button deformation and analyzing the patient’s surface. Again, we are going to adjust the tolerances here to either 0.5 or 0.3, depending if they are a standard breast or PBI. And acceptable percentages for treatment are 85%. However, this is up to physics or the physician’s discrepancies. And SGRT is used during the patient’s entire treatment to monitor movement. This is especially helpful during long beam waits. And if the surface capture is out of the four-millimeter translational or the three-degree robotic tolerance, we can easily pause the beam from outside of the room and take an additional X-ray and realign. If we do realign, we do check the deformation and take another reference capture for the remainder of treatment.