Varian Linear Accelerators
The powerful dual energy Varian linear accelerators are an example of the advances that keep
in the forefront of cancer care and research. This linear accelerator generates photon energies of 6 and 18 million electron volts as well as five different electron energies.
Special features include:
A multi-leaf collimator that allows precise, computer-controlled blocking of normal tissues – an integral component of the conformal 3-D treatment program and Intensity Modulated Radiation Therapy.
On-board imaging to provide image guided radiation therapy through continuous radiographic monitoring of patients during treatment.
- Cone Beam CT imaging, an additional tool in image guided radiation therapy (IGRT) using KV x-rays for diagnostic quality images used in the localization of tumors throughout the body.
Total body irradiation treatment capability for bone marrow transplantation.
IMRT treatment of the prostate, breast, head and neck and other sites.
Image guided Radiotherapy for prostate treatment.
Image Guided Radiation Therapy (IGRT)
Tumors are not stationary as both patients and their organs move. This motion can result in the radiation beam missing its target. Mercy Cancer Center Radiation Oncology has the most advanced method to evaluate and correct for this motion with its Varian Linear Accelerators, including the Varian Trilogy which encompasses two different imaging options. While many forms of IGRT are possible, the most advanced and accurate employs a diagnostic quality cone beam CT scan that can locate the tumor just prior to delivering the radiation beam. If the tumor has moved, the radiation beams can then be corrected before treatment begins. This allows the physicians at MCCRO to more precisely deliver radiation to the tumor while sparing more healthy surrounding tissue.
This combination of treatment device and imaging allows for daily IGRT for any patient who requires this therapy. Each of our four linear accelerators is capable of providing Image Guided Radiation Therapy. Other IGRT techniques we use are ultrasound localization for prostate treatments, portal imaging and PortalVision.
Intensity Modulated Radiation Therapy (IMRT)
Mercy Cancer Center Radiation Oncology has been providing radiotherapy treatment since 1988. In the 2003, we acquired a dedicated CT-based simulator system (AcQsim) to enhance our three-dimensional conformal radiotherapy program. We are also pleased to provide intensity modulated radiation therapy (IMRT) which is capable of providing targeted treatment while sparing normal tissue.
IMRT is especially useful for the treatment of tumors of the prostate, head and neck, brain and para-spinal regions. This technique has been used to reduce the incidence and severity of side effects of radiation including compromise of visual function, mucositis and xerostomia. Patients who have been treated in the past and had already received a maximum amount of radiation deliverable by conventional means are candidates for IMRT. IMRT allows these patients to receive additional radiation safely, which can result in prolonged survival and an improved quality of life.
Three dimensional (3-D) conformal therapy is limited to the use of radiation beams of uniform intensity whose contours correspond to the “beam’s eye view” of a tumor from different directions. This technology allows the most accurate shaping and shielding of the radiation beam. However, when a tumor is not well separated from the surrounding organs at risk, there may be no practical combination of uniform intensity beams that will safely treat the tumor and spare the healthy organs. In such instances, adding intensity modulation to beam shaping allows much tighter conformity to targets.
In IMRT, the beam intensities can vary dramatically across each treatment field to produce the desired results. The multi-leaf collimator is computer controlled and can shape the radiation field during the treatment to produce the required intensity modulation. Intensity modulated radiation therapy allows exceptional preservation of normal tissue.
Side effects of IMRT are the same as those of conventional radiation therapy but tend to occur less frequently and with less intensity in the short and long term. IMRT and conformal radiation therapy can be delivered anywhere in the body, as long as the affected area is properly immobilized. Also like conventional radiation therapy, any size tumor can be treated.
CyberKnife Radiosurgery Center
Some cancer patients may be candidates for treatment with CyberKnife, also located at the Mercy Cancer Center.