The radiation therapy department is a fully computerized and provides services using high-energy linear accelerators and a dedicated spiral CT scanner for tumor localization.
Our Cancer Services include two high-energy linear accelerators which are capable of being used with three-dimensional treatment planning. This combination enables the highest possible radiation dose to be administered to the cancer with minimal radiation to the adjacent normal tissue, preventing or minimizing the side effects of radiation.
In January 2000, our 2100EX Linear Accelerator was commissioned. With its multi-leaf collimator, this machine provides enhanced therapy modalities and improves efficiency in daily patient treatment. New treatment planning, record and verify and physics systems is also included.
External Beam Radiation
External beam radiation therapy is delivered using one of two linear accelerators and is operated by licensed professional radiation therapists.
Radiation treatments are painless, but accurate placement of the beam is essential. Special devices are used to position and immobilize the patient during treatment. The actual treatment time is very short. The patient only hears the machine working and does not feel any sensation from the treatment itself.
The 2100EX linear accelerator is utilized in treating various tumors with either 6 or 18 MV (million volts) of radiation. This linear accelerator also utilizes an automated multi-leaf system to shape the beam to conform to the tumor shape. The radiation beam placement and its relationship to the patient's tumor are constantly visualized on a monitor during the actual treatment. This ensures the most accurate treatment is delivered to the patient.
Conformal Radiation Therapy
With conformal therapy, we are able to map out the two-dimensional shape of a tumor and use multiple beams of radiation from different angles to maximize radiation to the tumor while protecting healthy surrounding tissues.
Calculation of the tumor size and shape is computed within millimeters. Healthy surrounding tissue is spared and the toxicity of the treatment is decreased, allowing for fewer side effects and more effective treatment.
Intensity Modulated Radiation Therapy (IMRT)
This therapy divides each radiation beam into multiple rays called beamlets and assigns different intensities to individual rays. The amount of radiation each beamlet releases into the tumor is adjusted in proportion to the tumor's thickness.
IMRT is different from conformal radiation in that it looks at the tumor in three-dimensions rather than two and modifies the treatment of that tumor according to the shape and depth.
Clinical Advantages to IMRT
Improves radiation dose uniformity: Reduces the risk that thicker areas of the cancer will receive inadequate doses of radiation and the incidence of "hot spots," overexposure to thinner cancer tissues.
Creates concave dose patterns: Radiation patterns can be sculpted with computers according to the exact shape of the tumor, allowing cancers that wrap around critical organs, such as the spinal cord and the optic nerves, to be treated.
Assigns weightings to targets and critical structures: Radiation oncologists have a wider range of dosage options to choose from when selecting radiation doses for tumors and surrounding areas. This allows each patient to be treated with a plan that best suits their cancer.
Treats multiple targets simultaneously: Separate doses of radiation can be given to different targets at the same time. This saves the patient and facility an extra treatment session to achieve optimal radiation.
Steps Involved in IMRT
Phase 1:
Simulation: By performing a CT simulation of the patient, radiation oncologists visualize the tumor and surrounding structures in three dimensions to devise a treatment strategy. A patient's CT is done inside the Cancer Center in the radiation therapy department.
Phase 2:
Inverse treatment planning: Computer software creates treatment plans to match target volume and dose distribution specified by the radiation oncologist. Next, the target volume is outlined and critical surrounding structures are identified. The radiation oncologist then determines optimal radiation doses for the patient and works with the physicists to determine treatment fields and table angles for treatment. Treatment goal information is entered into the computer and is available for the radiation oncologist to review and approve.
Phase 3:
Treatment delivery: Radiation treatment can be delivered one of three ways: by the "Step-and-shoot" method, Dynamic method or Tomotherapy. Digitally reconstructed radiographs (DRR) are obtained to verify that the patient setup is correct before the first session begins. The patient is then ready to receive daily treatments. Beam intensities are modulated through multi-leaf collimators (MLC), which are computer controlled tungsten leaves that shift to form specific patterns and take the place of lead alloy blocks used in conventional radiation therapy.
Benefits of IMRT over traditional radiation therapy:
- Lower complication rates
- Better tumor coverage
- Higher dosing potential resulting in increased probability of cure
Brachytherapy
Glendale Memorial Cancer Services has been in the forefront of treatment utilizing radioactive isotopes placed directly into the tumors for effective treatment. These procedures allow the delivery of very high doses of radiation within the cancer site with hardly any radiation occurring outside the cancer.
We utilize high dose rate brachytherapy, which requires placement of radioactive isotopes within the cancer site during treatment, and subsequent removal of the isotope rendering the patient free of residual radioactivity. In selected cases, radioactive pellets or seeds are implanted within the tumor site. These seeds remain permanently in the tumor, destroying the cancer cells when they try to multiply.
Patient Evaluations During Treatment
Radiation oncologists will see patients under treatment at periodic intervals to evaluate the patient's progress during the treatment and prescribe medication treatment for any side effects that may develop.
