Exquisiteness of Synchrony Respiratory Motion Managing approaches with Cyberknife Real Time Tracking System

CyberKnife is an image-guided radiosurgery system that consists of a 6-MV LINAC mounted to a robotic arm coupled through a control loop to a digital diagnostic X-ray imaging system. The robotic arm can point the beam anywhere in space with 6 degrees of freedom, without being constrained to a conventional isocenter. The real-time respiratory tracking and compensation system is called Synchrony. Using external markers in conjunction with diagnostic x-ray images, Synchrony helps guide the robotic arm to move the radiation beam in real-time such that the beam always remains aligned with the target. With the aid of Synchrony, the tumor motion can be tracked in three-dimensional space, and the motion-induced dosimetric change to the target can be minimized with a limited margin. Synchrony Respiratory Tracking System in CyberKnife Treatment Delivery is intended to enable dynamic image-guided stereotactic radiosurgery and precision radiotherapy of lesions, tumors and conditions that move under the influence of respiration. The convergence of cutting-edge medical technology with advanced cybernetics in the realm of respiratory motion management has yielded remarkable strides in cancer treatment, particularly with Cyber Knife's Real-Time Tracking System

The Synchrony System tracks and compensates for the motion of targets in areas affected by respiration. These may include targets in the lung, liver, pancreas, and kidneys, among others. The Synchrony System compensates for the respiratory motion of the target by correlating the target motion with the respiratory motion of the patient and synchronizing beam delivery with the target motion. The treatment robot adjusts and compensates for these movements to ensure more accurate treatment.

This exquisite synchronization enables clinicians to deliver higher doses of radiation to tumors, maximizing therapeutic efficacy while reducing treatment duration and potential side effects. Furthermore, by accounting for respiratory motion in real-time, RTTS minimizes the need for gating or breath-holding techniques, enhancing patient comfort and compliance.

?Learning Objectives:

• What Is Synchrony Tracking System
• Tracking Targets that move with Respiration
• Mechanism of Motion Management with Synchrony
• Radiation Therapist Synchrony Respiratory Model building
• Treatment Delivery
• Conclusions

?What Is Synchrony Tracking System:

?The Synchrony Tracking System is a crucial component of CyberKnife Radiosurgery, which is a non-invasive alternative to traditional surgery for treating tumors and other medical conditions. In CyberKnife treatment, precise radiation beams are directed at the target area, requiring pinpoint accuracy to avoid damaging surrounding healthy tissue. However, patient movement, such as breathing, can cause the target area to shift slightly during treatment, which can be problematic.

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The Synchrony Tracking System addresses this challenge by continuously monitoring the patient's breathing patterns and adjusting the radiation beam accordingly in real time. It synchronizes the radiation delivery with the patient's respiratory motion, ensuring that the radiation is accurately targeted even as the patient breathes.

?Tracking Targets that Move with Respiration:

?Dynamic Tumor Tracking: This approach involves continuously adjusting the position of the treatment couch or radiation beam based on real-time imaging of the tumor's position. By dynamically tracking the tumor during treatment delivery, this technique compensates for respiratory motion and ensures accurate targeting. Each motion management technique has its advantages and limitations, and the choice of approach depends on factors such as the specific characteristics of the tumor, the patient's anatomy, and the available technology at the treatment facility. However, the overarching goal of all these methods is to improve the accuracy and effectiveness of radiotherapy while minimizing the risk to surrounding healthy tissue. For Example,Lung,Liver, Pancreas, and a few thoracic and abdominal cancer targets

?Mechanism of Motion Management with Synchrony:

?Internal movement ? Location of tumor using fiducials or tracking volume

?External movement

? Tracking LED Marker visualization system monitors external movements

?Correlation mode

? Relationship between internal and external movements Continuously predicts internal movement via external movement Robot compensates for motion

Radiation Therapist Synchrony Respiratory Model building:

?A Synchrony? model can be created in Manual Mode. The Manual Synchrony tab allows the user to build a Synchrony model using one of 3 methods:

A. Image-by-image Phase Selection where an image is automatically triggered at a respiratory phase determined by the system each time the acquisition button is pressed,

B. User-defined Respiratory Phase Selection, or

C. No Phase

?If centring the target to the mid-respiratory phase is needed, the user must type the translational offset values into the couch boxes and then select Move Couch. Remember that these values were automatically populated if using Automatic Synchrony modelling mode.

??????? First acquire peak and valley images

??????? Capture the middle of the respiratory cycle

??????? Shift couch as needed to respiratory center ensuring that the target is not out of range of robot corrections at either full inhale or full exhale

??????? Acquire points: user-defined or automatic

Synchrony Model Table

The Synchrony Model (mm) displays Offset values and other information for all acquired images in the current Synchrony model. Radiation Therapist uses this information to analyse the Synchrony model.

?When first switching to the Synchrony phase, the Synchrony Model (mm) table is empty and no Live X-ray images are displayed until begin building a Synchrony model. The Synchrony Correlation Error for all model points is updated dynamically when an image is added, removed, or re-correlated in the model.

Treatment Delivery:

The treatment delivery of the Synchrony Tracking System involves several key steps:

Initial Setup: Before treatment begins, the patient undergoes imaging scans (such as CT or MRI) to precisely locate the tumor or target area. These images are used to create a treatment plan tailored to the patient's specific anatomy and condition.

?Patient Positioning: The patient is positioned comfortably on the treatment table in a way that allows for precise alignment with the radiation delivery system.

?Tracking Respiratory Motion: The Synchrony Tracking System continuously monitors the patient's breathing patterns using either an external marker placed on the patient's body or internal imaging techniques. This monitoring provides real-time feedback on the motion of the target area due to breathing.

?Adjusting Radiation Delivery: As the patient breathes, the Synchrony Tracking System dynamically adjusts the position and timing of the radiation beam to compensate for the motion of the target area. This ensures that the radiation is delivered accurately to the intended target, even as it moves with respiration.

?Continuous Monitoring: Throughout the treatment session, the Synchrony Tracking System continues to monitor the patient's breathing and adjust the radiation delivery as needed to maintain precise targeting.

?Treatment Completion: Once the prescribed dose of radiation has been delivered to the target area, the treatment session is completed. The patient can typically resume normal activities immediately afterwards, as CyberKnife Radiosurgery is non-invasive and does not require recovery time associated with traditional surgery.

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Overall, the treatment delivery of the Synchrony Tracking System enables highly accurate and precise radiation therapy, even for tumors or target areas that move with respiration, while minimizing radiation exposure to healthy tissue.

?Conclusions

?The Synchrony Tracking System in CyberKnife offers several significant benefits for patients undergoing radiosurgery, particularly when treating tumors or targets that move with respiration:

?Enhanced Precision: Synchrony Tracking enables highly precise and accurate radiation delivery by continuously adjusting the position of the radiation beam in real-time to compensate for respiratory motion. This ensures that the radiation is consistently targeted at the tumor or treatment area, even as it moves with breathing.

?Minimized Radiation Exposure to Healthy Tissue: By dynamically tracking the movement of the target and adjusting the radiation delivery accordingly, Synchrony helps minimize radiation exposure to surrounding healthy tissue. This reduces the risk of collateral damage and side effects, making treatment safer for patients. Non-Invasive Treatment: Like other CyberKnife procedures, treatment with the Synchrony Tracking System is non-invasive and does not require incisions or anaesthesia. This minimizes the risk of complications and reduces recovery time compared to traditional surgery.

?Improved Patient Comfort: Patients undergoing treatment with Synchrony Tracking can breathe naturally during the procedure, as the system compensates for respiratory motion in real-time. This can enhance patient comfort and reduce anxiety associated with breath-hold techniques or other methods used to mitigate motion during treatment.

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Overall, the Synchrony Tracking System in CyberKnife Radiosurgery offers a range of benefits that contribute to improved treatment outcomes, increased patient comfort, and enhanced safety for patients with tumors or targets that move with respiration.

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References:

1)???? Pepin EW, Wu H, Zhang Y, Lord B. Correlation and prediction uncertainties in the cyberknife synchrony respiratory tracking system. Med Phys. 2011 Jul;38(7):4036-44. doi: 10.1118/1.3596527. PMID: 21859002; PMCID: PMC3139505.

2)???? https://www.accuray.com/software/synchrony/