Surface-guided is more than a tool for treating DIBH patients

Maybe you’ve heard or seen the acronym SGRT (surface guided radiotherapy) around over the last few years and equate it with a clever way of treating patients in DIBH, well there’s a lot more to SGRT than that.  SGRT is rapidly becoming standard of care worldwide.  If you can treat it on a linac you can use SGRT to make the whole process quicker, safer and more accurate for you and your patients.

For most centres with or looking at SGRT solutions the initial goal is usually to have a safe and accurate way to treat patients in DIBH, but did you realise you can use it for other gated treatments as well as motion management for free breathing patients?

I think we’ve all had that moment when we’ve set up our patient, come out of the bunker, imaged and something is off.  Maybe an iso move applied in the wrong direction or you suspect the patient has relaxed or moved since you left the room.  If you use SGRT you’ll be alerted to positional errors before you leave the room or take your images, saving on time and radiation dose.  In radiotherapy we’re all about safety and accuracy when we’re delivering radiation but with the increase in hypo-fractionated treatments post pandemic we need to be even more vigilant and SGRT is here to help.

Let’s start with a group of patients that’s always tricky to set up.  Extremities.  If you’re a therapeutic radiographer like me you’ll know no two set-ups are the same, there are tattoos in odd places, vac bags which are awkward to store, get on the couch, let alone get the patient into in a reproducible position.  So how about having an image of the patient’s skin surface from CT to match them up to?  You can drop the tattoos and minimise the immobilisation, making the patient more comfortable and reduce the amount of manual handling required hopefully making each treatment a little quicker than it would have been.  And as you image and treat the patient the motion management part of the SGRT system will let you know if the patient has moved.  So, although the SGRT system is like another pair of eyes on the patient it’s not deskilling you it’s giving you the confidence that you are delivering a safe and accurate treatment.

As you’d imagine a large group of non-gated patients are those receiving treatment to their right breast.  This is the perfect group to start using SGRT with.  You can use the SGRT system to not only assist you in setting up your patient but also to monitor their intrafraction motion.  SGRT will help with reproducing arm positions and minimising pitch and roll during set-up which means reduced repositioning and reimaging leading to faster treatment times; and motion monitoring during treatment to ensure the patient hasn’t moved, relaxed and their breathing is within tolerance.  And I’m going to say it again, it’s giving you the confidence that you are delivering a safe and accurate treatment.

How about a single fraction spine? Yes, they’re usually an easy set-up but what if you set the couch height incorrectly? Anything out of tolerance will show on your SGRT system, and it won’t let you proceed with treatment until the discrepancy is rectified or you override.  Or the patient is in pain and moves out of tolerance mid beam?  You’ve got it, the SGRT system kicks in and holds the beam for you.  You’re also delivering a large dose in one session, and you may well add a decent margin to accommodate movement but what about the potential increased side effects from doing this?  If you’re using motion monitoring, could you reduce margin and side effects?  You might not need to give extra medications or need a face to face follow up for side effects.  Using SGRT could give your patient a better quality of life post treatment. 

What triggers a beam hold?  Let’s talk about what makes an SGRT system work before I answer that one.  For the SGRT vendor I am a clinical applications specialist for we have up to three ceiling mounted scanners in each treatment room, they consist of a projector and camera.  The camera detects the near invisible light projected onto the surface of the patient’s skin, and the non-rigid algorithm and true volumetric calculations give us the live skin surface and isocentre.  This is done continuously so you have real-time tracking of over 2 million points on the patient’s surface.  The continuous calculation of the isocentre shift, detects if your patient is slowly relaxing or any sliding movements. With Catalyst+HD from C-RAD AB, Uppsala, deviations are immediately projected as red or yellow light directly onto the patient’s skin, ensuring a fully patient centric and interactive workflow.  One of the main advantages of the deformable algorithm over a rigid one is that the system can use a large area as a region of interest (ROI), for example the whole thorax, yet be focused on the surface nearest the isocentre.  If you want to know a bit more about this, get in touch or have a read of my article published in RAD Magazine last year, there’s also a link on the C-RAD website.

Stopping the beam is triggered by the live patient surface going out of tolerance.  With the SGRT system that I’m clinical application specialist for the beam hold is triggered by several factors.  For non-gated patients if the isocentre or the surface tolerances are exceeded Catalyst+HD will hold the beam.  With gated patients if the isocentre or the surface tolerances are exceeded, or the breath-hold is not in the gating window Catalyst+HD will hold the beam.  You can adjust those tolerances per patient if you need to which is extremely flexible if you have a patient who needs tighter or larger tolerances. 

So, as you can see there are many reasons why SGRT is not only a solution for your DIBH patients but is beneficial for all your patients.  SGRT elevates patient-centred care, it enhances patient comfort, it improves patient through put and it drives patient safety.

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