Targeting Tumors with Precision: The Impact of Respiratory Gating in Radiation Therapy

One major challenge in radiation therapy is dealing with the movement of tumors, particularly those in the chest and abdominal regions, which are affected by respiration. This movement can lead to inaccuracies in treatment delivery, potentially compromising outcomes. Respiratory gating is a technology that addresses this challenge by synchronizing radiation delivery with the patient’s breathing. This helps minimize the damage to surrounding healthy tissue while effectively treating a tumor with radiation.

Respiratory Gating for CT Simulation vs. Treatment

Respiratory gating techniques and technologies are used during CT Simulation and radiation therapy treatment. Before treatment, the patient will be precisely positioned in a CT Scanner with the use of patient positioning lasers. Guided by respiratory gating, the patient undergoes CT scans at specific points in the breathing cycle to develop a customized treatment plan. This treatment plan is then implemented during radiation therapy treatment, which allows for a synchronized delivery of radiation.

Types of Respiratory Gating

Deep Inspiration Breath Hold (DIBH) is a technique for respiratory gating, and its benefits have been reported in multiple studies. This method involves patients taking a deep breath and holding it, reducing the movement of the chest wall. The radiation is then delivered at specific points of the breathing cycle minimizing radiation exposure to the heart. DIBH also increases the distance between the tumor and the heart during treatment, which can help isolate the tumor.

There are two types of DIBH: voluntary DIHB and moderate DIHB. With Voluntary DIBH, patients are asked to hold their breath for 10 –20 seconds. The use of body marks and tattoos can help orient the patient during treatment.  Moderate DIHB uses devices such as Elekta’s Active Breathing Coordinator™ (ABC) and Motion View ™, incorporating a spirometer to assist the patient in a comfortable, consistent DIBH.

In recent years, technology has emerged to aid in respiratory gating. Surface Guided Radiation Therapy (SGRT) is a contact-free technology that uses cameras to monitor the patient’s movement from breathing. These systems can both verify the patient’s position before treatment during CT simulation and track motion throughout the treatment.

Vision RT is the inventor of Surface Guided Radiation Therapy (SGRT) with over 2,700 Horizon ™ systems in clinical use. These cameras work in tandem with AlignRT Advance, software that automatically pauses radiation delivery from the treatment delivery system.

Another leading technology company for SGRT is C-RAD. Their Catalyst+ products, coupled with an application software, offer high-resolution surface imaging with submillimeter accuracy and real-time motion management to ensure consistent breath-hold reproducibility. Augmented reality color projections on the patient’s skin allow for posture corrections. These products can be seamlessly integrated with treatment machines.

DYN’R Medical Systems’ SDX system uses both a spirometer and specialized glasses to give patients visual biofeedback to guide their breathing. Optimal gating modules for this system include: Siemens SOMATOM, Varian ProBeam, IBA Proteus PLUS, IBA Proteus ONE, and MEVION S250i.

Varian Medical Systems’ (Siemens Healthineers) Real-time Position Management (RPM) is a video-based system that uses an infrared camera, guided by a reflective marker block placed on the patient’s abdomen, to track breathing during DIBH. The RPM tracks the movement of the plastic marker block in three dimensions – vertical, longitudinal, and lateral. Any movement of the marker will be picked up by the infrared camera.

The company also offers an SRGT product IDENTIFY, which uses a series of three cameras to allow non-invasive tracking of the patient in real time. When installed in the CT Simulation room, IDENTIFY uses a Visual Coaching Device (VCD) to guide the patient’s breathing.

INDENTIFY can also be installed in the treatment room. Working alongside the Ethos adaptive radiotherapy (ART),  a series of ceiling mounted colored lights visually coaches the patient in breath hold during treatment.

Let’s look at some key benefits of respiratory gating in radiation therapy.

Improved Imaging

Respiratory gating during CT Simulation and radiation therapy helps produce clearer images of the tumor. For example, DYN’R Medical Systems’ SDX spirometry-based system allows for more stability of the organs and treatment area, which enhances image quality.

Increased Treatment Accuracy

Respiratory gating works by monitoring the patient’s breathing pattern and delivering radiation only when the tumor is in the optimal position, typically during a specific phase of the breathing cycle. This precise synchronization increases the accuracy of the treatment when targeting the tumor.

Reduced Normal Tissue Exposure

One of the key advantages of respiratory gating is its ability to spare healthy tissue from unnecessary radiation exposure. By delivering radiation only when the tumor is in the target position, respiratory gating minimizes radiation exposure to surrounding normal tissue. This reduction can lead to a lower risk of side effects and complications. A report published in the American Association of Physicists in Medicine (AAPM) demonstrated that respiratory gating reduced the volume of normal lung tissue receiving high doses of radiation, resulting in decreased radiation-induced lung toxicity.

Enhanced Patient Comfort

Respiratory gating allows for shorter treatment times compared to conventional radiation therapy methods. Since treatment is delivered only during specific phases of the breathing cycle, there is less need for repositioning or repeating treatment sessions. This not only improves treatment efficiency but also enhances patient comfort.

Expanded Treatment Options

The precise tumor targeting offered by respiratory gating enables the treatment of tumors located in challenging locations, such as those affected by respiratory motion. This expanded treatment capability opens new possibilities for patients who may not have been candidates for radiation therapy using conventional methods.

Improved Treatment Outcomes

Studies have shown that respiratory gating can improve treatment outcomes in certain cases. By increasing treatment accuracy and reducing normal tissue exposure, respiratory gating has been associated with higher local control rates and improved survival outcomes. A study published in the Journal of Thoracic Oncology reported improved overall survival rates in patients with lung cancer treated with respiratory gating compared to those treated with conventional radiation therapy.

Conclusion

Respiratory gating is a valuable technology that offers several benefits in radiation therapy treatment. From increased treatment accuracy to improved patient comfort, respiratory gating can enhance the quality of care for cancer patients and improve overall survival outcomes. New technologies combine the latest surface imaging techniques with precise patient setup, further optimizing the effectiveness of respiratory gating. As technology advances, healthcare providers should consider implementing respiratory gating to improve treatment outcomes and patient experiences. For more information on how to add respiratory gating to your practice, please feel free to contact us.