3D/Conformal Radiation Therapy
Conformal radiation therapy utilizes imaging and computer software tools to help the physician better design radiation treatment beams. This procedure involves the construction of an immobilization device to be used during treatment planning and treatment. Three-dimensional imaging (such as computed tomography) is done with the patient in the immobilization device and the patient goes home. The physician then plans treatment beams on the images. Once appropriate beams are designed, the patient returns to the radiation department (generally one week following the initial scan) for a confirmation "physical simulation", followed by the initiation of treatment.
This therapy is most often used to treat primary choroidal melanoma and retinoblastoma. We construct an eye plaque made out of gold, which holds radioactive Iodine-125 seeds. Each plaque is custom made to provide individualized treatment for each tumor. At the time of surgery, the plaque is positioned on the outside of the eye against the base of the tumor. The plaque emits radiation over 5 days to kill the tumor cells so that the patient’s eye can be preserved. Then, the eye plaque is removed.
Duke University Medical Center was one of the founding institutions of the Collaborative Ocular Melanoma Study (COMS), designed to evaluate the efficacy of eye plaque therapy. Therefore, we have extensive experience with Iodine-125 plaque therapy for choroidal melanomas and preoperative irradiation for tumors that are too large for eye plaques. The Department also has extensive experience in the treatment of retinoblastoma.
High Dose Rate Brachytherapy/ Low Dose Radiation
Brachytherapy entails the placement of a radioactive source in a cavity (intracavitary therapy) in close proximity to the tumor or in the tissues themselves (interstitial therapy) to deliver a high dose of radiation to a limited volume. Recently radioactive sources with very high specific activity have become available, such as iridium, which deliver a high dose of radiation in a very short period of time. This is referred to as High Dose Rate (HDR). The HDR unit is small, self-contained and can be moved about. While the unit is not in use, the radioactive source is in the safe and poses no risk of radiation exposure.
During a procedure the radioactive source is out of the safe and there is the risk of radiation exposure to the health care personnel. To avoid this, the procedures are often carried out with the patient in an existing, shielded accelerator room with the health care personnel outside of the room. Having a HDR unit in a shielded booth adjacent to the operating room would expand the utilization of this resource. Having the unit in an area adjacent to the operating rooms would permit using it for patients that are found to have gross or microscopic residual disease at surgery. At the time of surgery catheters can be placed in the area of the tumor and with the patient still under anesthesia the patient is brought to the booth adjacent to the operating room. With the catheters in place the radioactive source is passed through the catheters for the specified time necessary to deliver the desired dose of radiation. This unit can also be used for some of the cases currently being done with conventional, LDR radioactive sources. HDR does not replace LDR Brachytherapy but it expands this type of resource.
LDR refers the use of inserted or implanted radioactive sources for various cancers, such as the treatment of cervical cancers using intracavitary implantation of Cs-137 brachytherapy sources, PSI, and eye plaque treatment, etc.
The intraoperative radiation therapy program is a joint effort of the Departments of Radiation Oncology, Surgery, Gynecologic Oncology, and Anesthesiology. In this highly specialized technique, radiation therapy is administered, via a high dose rate after loading machine, during surgery.
Treatment to tumors located in the thoracic and abdominal regions, such as lung and liver, is challenging because of respiratory organ motions. The traditional approach is to expand each treatment field to ensure the entire tumor volume is included in the radiation field. To minimize radiation damage to extra normal tissues due field expansion, Duke has adopted respiratory control techniques to synchronize the radiation beam with tumor motion. With this technique, the treatment margin added to accommodate the organ motion could be reduced to minimize the radiation dose to normal tissues. Advanced technologies are used to achieve this goal, such as the use of Varian RPM system to monitor respiratory pattern, On-Board Imager to verify target motion, and electronic portal imaging system to verify real-time radiation delivery.
Image-Guided Radiation Therapy (IGRT)
Image-Guided Radiation Therapy (IGRT) is a process of using various imaging technologies to locate a tumor target prior to a radiation therapy treatment. This process is aimed to improve treatment accuracy so that the need for wide target margins, which have traditionally been used to compensate for errors in localization. As a result, the amount of healthy tissue exposed to radiation can be reduced, minimizing the incidence of side effects. At Duke, physicians applied advanced imaging techniques using CT, MRI, PET/CT, and SPECT to accurately delineate treatment target. Moreover, they are able to use state-of-art in-room on-board imaging and cone-beam CT technologies to visualize the treatment tumor three-dimensionally prior to the delivery of radiation beam. IGRT is complementary to IMRT. IMRT is used to improve the radiation delivery precision and IGRT is used to improve the radiation delivery accuracy.
Intensity Modulated Radiation Therapy (IMRT)
Tumors to be treated are often surrounded by normal tissue and/or organs. The dose tolerances to the normal critical organs are one of the limiting factors to radiation dose prescribed to tumor. With the IMRT technique, one will be able to shape the radiation dose to the target and then minimize the dose to critical organs. Therefore, the expected dose could be prescribed to tumor while limiting the radiation damage to the normal tissue within the tolerance. The IMRT involves a complicated treatment planning process (called inverse planning) and a dedicated delivery process using dynamic multi-leaf collimator (MLC). A comprehensive quality assurance program specific for both machine and patient was very critical and was developed at Duke to ensure the quality treatment of IMRT. We use the latest Varian Eclipse inverse planning system and the Clinac 21EX machine with120-leaf MLC to deliver fine radiation dose to the target.
Prostate Seed Implant (PSI)
PSI is a treatment procedure for the use of permanently implanted radioactive sources for treatment of prostate cancer. This procedure was conducted with team efforts from both Radiation oncology and Urology. It is also one of low-dose rate brachytherapy procedures.
Total Body Irradiation (TBI)
Radiation given to the whole body as a preparatory regimen for bone marrow transplant in the treatment of hematologic cancers and other disorders.
Total Skin Electron Beam (TSEB)
Radiation given to all of the skin with an electron beam technique for various skin cancers.