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Getting the patient into the right position is one of the first things the radiation therapy team checks before treatment begins. The reason is pretty simple. Radiation needs to be delivered to a specific area, so even small changes in how a patient is positioned can make a difference. Surface Guided Radiation Therapy (SGRT) gives the team another way to keep an eye on that position using optical cameras that track the surface of the body.
So, what is happening behind those cameras? How does SGRT know when a patient has moved, and how does it help during treatment? In this blog, we’ll break down how SGRT works, from the optical cameras and 3D surface mapping to the reference position used to monitor the patient during radiation therapy.
What Is Surface Guided Radiation Therapy
Surface Guided Radiation Therapy, or SGRT, is a way of monitoring a patient’s position during radiation treatment. It uses optical cameras to look at the outside of the body and track changes in position.
This is often described as optical surface imaging radiation therapy because the system uses light and cameras to create a picture of the patient’s surface. Unlike X-rays or CT scans, the optical imaging itself does not expose the patient to additional radiation.
The goal is simple: give the radiation therapy team another way to see whether the patient is positioned as planned and whether they move during treatment.
How Does the Optical Camera System Work
The cameras are the part of the system that first captures the patient’s surface. But there is more happening behind the scenes than simply taking a picture.
Capturing the Patient’s Surface
Specialized cameras are positioned around the treatment area. They capture information about the shape and position of the patient’s external surface.
The system then processes this information to create a digital representation of the body surface. This is sometimes referred to as 3D surface mapping cancer treatment technology.
The important thing to understand is that SGRT is looking at the surface of the body. It is not taking an image of the tumor or looking inside the body.
Creating a Reference Surface
Before radiation treatment begins, the patient’s treatment team has already determined how they should be positioned. This planning can involve CT simulation, where images are taken to help create the radiation treatment plan.
The patient’s planned setup provides a reference for the SGRT system. During treatment, the live surface information from the cameras can be compared with this planned position.
This CT simulation reference position gives the system a baseline to work from. If the patient’s current position differs from that reference, the treatment team can see the change and decide whether an adjustment is needed.
Detecting Position Changes
This is where the system becomes especially useful. The cameras continuously collect surface information, allowing the software to look for changes in the patient’s position. A patient may shift slightly, move an arm, or change their posture without realizing it.
SGRT can detect these changes and provide information to the treatment team in real-time.
That does not mean the technology makes treatment decisions on its own. The radiation therapy team still evaluates the information and determines what action, if any, should be taken.
What Happens During an SGRT-Guided Treatment Session
The process can be broken down into a few simple steps.
1. The Patient Is Positioned
The patient is placed on the treatment table in the position established during treatment planning. The team makes sure the setup is appropriate before treatment begins.
2. The Cameras Scan the Surface
The surface tracking camera radiation systems capture the patient’s external surface. The system turns that information into a digital surface model that can be monitored.
3. The Live Position Is Compared With the Reference
The system compares the patient’s current surface with the reference position created during the planning process.
If the two do not line up as expected, the difference can be shown to the treatment team.
4. The Team Checks the Alignment
If there is a noticeable change, the radiation therapy team can assess the situation. They may reposition the patient or perform additional checks before continuing.
5. Position Is Monitored During Treatment
SGRT can continue tracking the patient’s surface while radiation is being delivered. This gives the team another way to notice movement during the treatment session.
Why Do Optical Cameras Matter in SGRT
The cameras are what allow SGRT to see the patient’s surface without touching the patient or using additional imaging radiation.
Think of it as creating a digital snapshot of the patient’s position, then continuously checking that position against the planned setup. If something changes, the system can alert the treatment team.
This makes real-time patient positioning technology an important part of how SGRT fits into modern radiation therapy. The technology gives the team more information about what is happening with the patient’s position rather than relying on a single check at the beginning of treatment.
Takeaway!
So, how does SGRT work? At its simplest, the process involves optical cameras capturing the patient’s body surface, software creating and comparing three-dimensional surface information, and the treatment team using that information to monitor positioning.
The system can check the patient’s setup against a planned reference position and continue watching for movement during treatment. For patients, that means a technology working quietly in the background while the radiation therapy team focuses on delivering treatment according to the plan.
At ROCVC, we understand that SGRT does not replace the careful planning that goes into radiation therapy. Instead, it gives treatment teams another way to monitor patient position and make the treatment process more controlled and precise.
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