Why is tight linac integration important for delivering Surface Guided Radiation Therapy (SGRT) treatments?

The integration of the SGRT system with the linac is critical to safely deliver radiation therapy without significantly increasing the treatment delivery time. An integrated SGRT/linac workflow will provide many benefits, including:

  • Helping to avoid patient mistreatments by integrating patient selection to ensure the patient selected on the treatment device is the patient selected on the SGRT system.
  • Eliminating the need to setup the patient separately for multiple table angles by integrating treatment field selection to ensure that the linac table orientation and isocenter are automatically sent to the SGRT system.
  • Reducing data transcription errors by integrating patient position correction to ensure that couch corrections are accurately sent from the SGRT system to the treatment device.
  • Helping to improve patient safety through integration of the beam control to ensure that the beam is quickly paused and restarted as required due to patient moving out of position or during the respiratory cycle for a gated treatment.

How does C-RAD Catalyst interface to Elekta’s linear accelerators?

C-RAD tightly integrates to Elekta linear accelerators using the following interfaces:

The first interface, cElekta, manages patient and treatment field selection within Elekta’s Record and Verify system, MOSAIQ. cElekta is used by Catalyst to retrieve patient setup information when a patient’s treatment and field is selected at the Elekta linear accelerator treatment console. By utilizing a direct interface, the risk of selecting an incorrect patient or treatment field is minimal, and the workflow speed is increased.

Unique among SGRT systems, the cElekta interface also simplifies the SGRT patient setup by automatically using the table rotation included in the treatment field. While other SGRT systems require patient data or reference images to be collected for each table rotation position, Catalyst calculates patient data as required for each table position allowing for faster patient setup and increased treatment flexibility.

The second interface, cMosaiq, sends the patient’s position correction data for use by the Elekta Precise Table and, if the linac has a Medical Intelligence robotic couch top, the HexaPOD. cMosaiq can be used to position the patient prior to Cone Beam CT and to correct the patient’s position to compensate for any movement after the Cone Beam CT. cMosaiq also directly interfaces to the MOSAIQ Couch Move Assist (CMA) interface.

The third interface, cElektaResponse, enables Catalyst to pause the patient treatment during delivery. Elekta’s Response is a fast, hardwired interface that immediately stops linac motion and puts the radiation delivery into standby pausing the delivery until, depending on the treatment delivery process, either Catalyst or a therapist allows the treatment to continue, or a therapist stops the treatment.

In 2014, Cui et al (1) published that the combination of Catalyst and the Elekta linac system beam on delay was 0.22 seconds and that gated treatment delivery was dosimetrically accurate with only a moderate increase in total delivery time.

The fourth interface ensures that all the patient information is accurately recorded into the patient’s medical record. All healthcare information systems with an EMR, including Elekta’s MOSAIQ, include importing capabilities that are used to collect patient reports, typically transmitted in a PDF format. Each of the Catalyst software modules contain reports that may be exported and imported into a patient’s medical record.

Is a gated treatment delivered using C-RAD Catalyst together with Elekta’s linear accelerator clinically acceptable?

Catalyst enables an Elekta linear accelerator to deliver a more precise, safer treatment. Elekta’s gating interface, Response, is a hardwired device allowing validated gating devices to pause treatment delivery, and Catalyst can use the Response interface to pause treatment delivery for a patient position out of tolerance, to deliver a free-breathing gated treatment, or to deliver a deep-inspiration breath hold treatment.

In 2014, publication of the physics validation (1) performed at the Swedish Cancer Institute (Seattle, Washington USA) demonstrates that the combination of the Elekta Synergy with Catalyst can be used to deliver a VMAT treatment. And in 2016, a clinical evaluation (2) was published by the LMU University (Munich, Germany) showing the efficacy of using DIBH delivered with Catalyst in reducing heart dose.



(1) Cui, G., Housley, D.J., Chen, F., Mehta, V.K. and Shepard, D.M. (2014), Delivery efficiency of an Elekta linac under gated operation. Journal of Applied Clinical Medical Physics, 15: 2-11. https://doi.org/10.1120/jacmp.v15i5.4713

(2) Schönecker, S., Walter, F., Freislederer, P. et al.Treatment planning and evaluation of gated radiotherapy in left-sided breast cancer patients using the CatalystTM/SentinelTM system for deep inspiration breath-hold (DIBH). Radiat Oncol 11, 143 (2016). https://doi.org/10.1186/s13014-016-0716-5