Washington state center harnesses C-RAD technology to enhance patient setup and motion monitoring

Washington’s Seattle Cancer Care Alliance
Nov 23, 2020 8 minute read

Seattle Cancer Care Alliance South Lake Union implements Surface Image Guided Radiation Therapy

Washington’s Seattle Cancer Care Alliance
Washington’s Seattle Cancer Care Alliance

An effort spearheaded by physicists at Seattle’s Washington’s Seattle Cancer Care Alliance (SCCA) South Lake Union (Seattle, Washington) led to a more streamlined, integrated solution for patient positioning and motion management. In early 2017, the center implemented C-RAD’s Catalyst HD system to enable Surface Image Guided Radiation Therapy (SGRT), a non-ionizing imaging technique to guide patient positioning during setup, monitor intra-fraction motion and guide gated treatment deliveries.

The team selected the C-RAD Catalyst HD system for SGRT (see sidebar: What is SGRT?) because of its seamless integration with the clinic’s Elekta linacs and MOSAIQ® Oncology Information System. It could also be used for both simulation and treatment, allowing the clinic to have a single system throughout the patient journey.

SCCA’s previous method for breath-hold treatments involved using two different patient motion management systems for simulation and treatment. This required the transcription and translation of data between the two systems, which was time-consuming and cumbersome.

“Using the single C-RAD Catalyst system to deal with all the information rather than two separate systems is far preferable.”

“Using the single C-RAD Catalyst system to deal with all the information rather than two separate systems is far preferable,” says Juergen Meyer, PhD, Clinical Physics Lead at SCCA South Lake Union. “The C-RAD system provides a more integrated, efficient workflow and offered some unique features that influenced our decision, such as its ability to project information onto the patient and the quality of the deformable registration algorithm it uses.”

The C-RAD systems were installed in SCCA South Lake Union and University of Washington Medicine Center (UMWC) Northwest in 2016. In February 2017, following physicist and therapist training, implementation began using a phased approach designed to build confidence in the new method and to ensure a comfortable transition for the radiation therapists.

“SGRT implementation was a team effort for us,” Dr. Meyer says. “Initially, the physics team drove it in close collaboration with the chief therapist. SGRT champions were allocated for each machine to help get everyone on board, and then the radiation therapists drove the advanced implementation stages, based on their comfort levels and the clinical utility of the technology.

“As soon as we started to experience the benefits of the new system, everyone was very happy with the change,” he adds. “We did much of our learning by doing, but a SGRT task group [TG302] has been established to provide guidelines that will hopefully expedite implementation for others.”

Phased implementation

SCCA’s C-RAD implementation steps entailed building trust, a hybrid approach, further hybridization and “the leap” to use C-RAD by itself.

Step Trush

SGRT setup workflow

The VSim starts with a sternal reference instead of going straight to the isocenter (ISO) reference. Since the C-RAD algorithm weights the isocenter heavily, it was found that the sternal reference provides the most accurate setup for visualizing rotations. Patients are very accurately lined up with the sternal reference (within 1 mm, 1°) and then the nominal shifts to ISO are applied. The C-RAD Catalyst shifts are displayed and checked before they are applied. If the rotations are out of tolerance, or if orthogonal pair imaging shows that shifts are required, then a new reference image is acquired.

“In the beginning, images were obtained for three days when a new reference image was captured to check that everything was OK,” says SCCA South Lake Union radiation therapist Chris Norris. “This was reduced to two days because we are consistently setting up patients very accurately using SGRT.”

“We achieved significantly higher positional accuracy and improved precision with the C-RAD Catalyst HD system.”

SCCA uses SGRT technology to guide patients during a deep inspiration breath hold (DIBH) for left breast radiotherapy.

Members of the SCCA treatment team
Members of the SCCA treatment team

“We predetermine the required breath depth during simulation and planning,” he says. “We can then reproduce this breath hold precisely during treatment, using a virtual tracking point on the patient’s sternum and audio-visual feedback to the patient. When we conducted a study to evaluate the accuracy and stability of DIBH using SGRT compared to our previous radiofrequency transponder method, we achieved significantly higher positional accuracy and improved precision with the Catalyst HD system.”3

Integration with Elekta linacs ensures an efficient, streamlined workflow for patient positioning and motion monitoring, as well as automatic treatment gating for DIBH treatments using Elekta’s Response gating interface.

Workflows transformed with SGRT

“Our main motivation for adopting SGRT was for breast patients,” Dr. Meyer notes, “but in principle, SGRT could be used for all patient setups. For example, we find it particularly helpful for prone patients, to correct any posture changes prior to CBCT imaging.

“SGRT has transformed our workflows, improving efficiency and enhancing setup accuracy.”

“There is an initial investment to implement SGRT, but it has transformed our workflows, improving efficiency and enhancing setup accuracy,” he continues. “Building staff confidence during implementation was really important for maximum uptake in the clinic. When the therapists see the information SGRT provides, it gives them the confidence to use it in different situations.

“SGRT continues to develop with the introduction of new features, such as collision avoidance and patient identification,” Dr. Meyer adds. “These developments make good use of the technology and will further impact patient safety in the years to come.”

To learn more about SGRT, click here or contact your local Elekta representative.


  1. Meyer, J, Smith, W, Geneser, S. (2020) Characterizing a deformable registration algorithm for surface-guided breast radiotherapy. Med. Phys. 47 (2): 352-362.
  2. Stanley, DN, McConnell, KA, Kirby, N et al (2017) Rad Onc Phys. Comparison of initial patient setup accuracy between surface imaging and three-point localization: A retrospective analysis.
  3. Kalet, AM, Cao, N, Smith, WP. (2019) Accuracy and stability of deep inspiration breath hold in gated breast radiotherapy – A comparison of two tracking and guidance systems. Physica Medica 60: 174–181.

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