Respiratory Gating and Deep Inspiration Breath Hold (DIBH)
Accurately tracking tumor position is a critically important factor when maximizing
radiation dose to the tumor and limiting normal tissue exposure.
What is respiratory gating?
Gating is a system that tracks a patient’s normal respiratory cycle with an infrared
camera and chest/abdomen marker. The system is coordinated to only deliver
radiation when the tumor is in the treatment field.
The respiratory gating radiotherapy technique can apply to moving
tumors, such lung and liver cancer. Real-time Position
ManagementTM(RPM) respiratory gating system, which gates the beam
delivery during treatment to account for organ motion.
The infrared camera tracks tumors that move during treatment as the
patient breathes in and out, then the linac accelerator controlled x -ray
beam treats the tumor within the gated phase to assure the accuracy of
treatment position. The non-invasive infrared tracking marker box is
placed on patient’s body. We have the big bore CT simulator with fourdimensional CT capability, it can record combines continuous monitor
chest wall movement during treatment with pre-plotted target trajectories
to ensure the maximum dose is delivered to the target while avoiding
critical organs. In this case, we can treat patients with high accuracy while
minimize treatment errors.
Radiation beam is gated to when the target falls within the treatment
field, patient can breathe normally and remain comfortable and high
compliance during the treatment. This technique will takes about five to
ten minutes more than the regular treatment time.
What can a patient expect when treated with the respiratory-gated system?
The patient is first imaged on the CT Simulator while tracking the movement of the
lightweight chest/abdomen marker with the infrared camera. Images are analyzed
using 4D software (the fourth dimension being time) to accurately determine tumor
motion relating to breathing.
When the patient arrives for treatment, the chest/abdomen marker will be placed in
the same location as set for imaging. The infrared camera will track the patient’s
breathing cycle as he or she is allowed to breathe in a relaxed manner. The gating
system will automatically detect when to give radiation according to the patient’s
specific respiratory cycle. The beam will be held off for disruptions in the breathing
cycle, such as coughing or sneezing. Using the respiratory gating system, the patient
will receive better tumor control and less normal tissue complications without
sacrificing comfort.
What is DIBH treatment?
Respiratory Deep Inspiration Breath Hold (DIBH) is a specific radiation therapy
technique for Breast treatment to spare doses to the heart and lungs. Using the DIBH
technique, the radiation is delivered only at certain points during the patient’s
breathing cycle of inspiration and expiration. The patient is asked to take a deep
breath in and hold their breath for about 20 seconds.
This, in turn, will limit the
amount of the heart and lung that is exposed to the radiation beam, since taking a deep
breath in will allow these organs to move out of the treatment field (See sample
picture of heart position completely out of the yellow line with DIBH). DIBH can be
also used to minimize internal organ motion for other body sites, such as the stomach,
pancreas, and liver.