The Varian® On-Board Imager® (OBI), standard on the Trilogy™ linear accelerator, makes Dynamic Targeting image-guided radiation therapy (IGRT) more efficient and convenient.
Whether clinicians want to image the patient daily or weekly, the Varian OBI provides flexible imaging protocols that meet every need.
The OBI kV imaging system delivers improved tumor targeting using high resolution, low dose digital imaging in the treatment room. Users can confidently manage patients and target movement—both before and during treatments. A choice of imaging modalities is available on the system, including 2D radiographic, fluoroscopic, or 3D cone-beam CT imaging. The use of kV imaging can result in lower patient dose and better image quality than megavoltage imaging.
Clinicians need the best possible image information to make fast accurate decisions when comparing reference images to set-up images prior to treatment. This information is the basis for key decision making: whether to continue treatment as is or change course.
The planning and delivery of tightly defined dose distributions in 3D is a challenge that has been solved. Yet aligning the treatment beam to the target volume remains a key challenge to improving outcomes because patients, tumors, and normal tissues move.
OBI provides the tools to manage both Interfraction motion (changes in position caused by day-to day set-up conditions) and Intrafraction motion (changes in position during a treatment session because of normal respiratory and organ motion).
To minimize both types of motion, the OBI facilitates pretreatment, online imaging as an integral part of the clinical process.
The OBI identifies the patient's position at the time of treatment so that small couch adjustments ensure optimal positioning. All tasks in the patient repositioning process can be performed remotely—saving time and simplifying the process.
The system has two modes of operation: radiographic repositioning using fast reliable automated tools for anatomical registration or radio opaque marker registration, and cone-beam CT repositioning.
Tumors that move because of respiratory motion may be more effectively treated using the Real-time Position Management™ (RPM) system. Gating automatically turns the treatment beam on and off at intervals synchronized with the patients' respiratory pattern, effectively freezing the moving target.
Varian's OBI is mounted on the treatment machine via robotically controlled arms that operate along three axes of motion, for optimal tumor view. All positioning is automated. By using the robotic technology and control software to position the OBI and patient couch, the system offers the automation, speed, and flexibility necessary to make the IGRT process clinically practical for thousands of cancer patients.