Tumors can move during treatment (usually due to patient respiration) and between treatments (usually due to day-to-day variations in patient setup). Image-guided radiotherapy (IGRT) uses advanced imaging techniques to verify patient position and tumor position at the time of treatment. Knowing exactly where the tumor is allows clinicians to reduce the volume of tissue exposed to radiation, targeting only the tumor and sparing the surrounding normal tissue. Radiating less normal tissue reduces the toxicity of radiotherapy, improving the patient’s quality of life, and it may make it possible to deliver higher radiation doses to the tumor and thereby increase the likelihood of local tumor control.

How it Works

When patients are positioned on a treatment couch, an X-ray system mounted on a robotic arm is rotated around the body, to gather images that pinpoint a tumor’s exact location. These images are then compared with existing images (MRI, CT, or other kinds of scans) in order to determine if the tumor has moved since the last treatment. Because tissues and organs can settle around bones differently each time a patient lies down on a treatment table, tumors can end up in different positions from one treatment session to another. 

In addition, tumors can move several centimeters due to a patient’s normal respiratory cycle. The advanced imaging capabilities of our multifunctional linear accelerator produce low-dose, high-resolution X-ray images that pinpoint tumor position. The multifunctional linear accelerator employs other technologies—an electronic portal imaging device and a respiratory gating system—to enable clinicians to verify patient positioning and to account for tumor motion caused by respiration.  

Patient Benefits

  • Through more precise targeting of the beam, dosage levels can be increased and target volumes (the three-dimensional areas to receive treatment) can be reduced--so tumors get a higher dose of radiation and healthy surrounding tissues get very little. This may increase treatment effectiveness. At the very least, it can reduce treatment times and the possible side effects of radiotherapy.
  • Smaller lesions can be treated more easily and effectively.
  • State-of-the-art motion management techniques allow patients to breathe naturally during treatment sessions, increasing treatment accuracy, reducing stress, and increasing patient comfort.

Physician/Clinic Benefits

  • Advanced imaging capability produces a variety of imaging modalities in order to view the tumor and surrounding anatomy including radiographic (two-dimensional), fluoroscopic (moving, in real-time), cone-beam CT (three-dimensional).
  • The multifunctional linear accelerator can deliver very high dose rates—up to 1000 MU (monitor units) per minute—so treatment times can be reduced, which reduces the burden on cancer patients.
  • The multifunctional linear accelerator offers the most precise isocenter, or beam focal point, available—a sphere that is 1mm in diameter.
  • The equipment has a highly accurate, high-resolution multileaf collimator (beam-shaping device).
  • IGRT incorporates a top-of-the-line portal imaging device that produces high-resolution images for patient positioning, treatment verification and quality assurance.
  • Clinicians are able to deliver the most advanced treatments in the same amount of time as a standard treatment, with increased ability to account for patient and tumor movement.
  • Doctors can use the multifunctional linear accelerator to treat smaller lesions and metastases, as well as larger tumors. This means that some cancers that would have been considered untreatable with radiation can now be treated this way, rather than with more invasive techniques such as surgery or chemotherapy.

© 2018 Intermountain Healthcare. All rights reserved. The content presented here is for your information only. It is not a substitute for professional medical advice, and it should not be used to diagnose or treat a health problem or disease. Please consult your healthcare provider if you have any questions or concerns.