In addition to UT Southwestern Radiation Oncology’s stereotactic therapy capabilities, the following advanced technologies are in use at UT Southwestern:
- 4-D CT Simulation
- Image-Guided Radiation Therapy (IGRT)
- Intensity-Modulated Radiation Therapy (IMRT)
Radiation Oncology uses state-of-the-art, 4-D CT (computed tomography) scanners that reproduce the tumor size, location, and movement for each patient. This simulation is used to test various treatment fields and immobilization devices that position the patient during radiation therapy. With this moving picture, the treatment team can mold multiple beams of radiation to fit the precise size and shape of a tumor, thus treating it with extreme accuracy.
Brachytherapy is a form of radiation therapy in which a radioactive source is placed in direct contact with the tumor or treatment area. Implantable seeds or gel, as well as temporary exposures using paddles or other devices, are all examples of brachytherapy.
- High dose rate (HDR) brachytherapy
- The newest form of brachytherapy treatment, and is most often used for gynecological cancers, head and neck cancers, and skin cancers. A device or holder is placed on the area to be treated, or into the area through a natural body orifice. The device is then connected to the HDR machine and a small but intense radiation source is loaded into it. The dose is delivered in approximately five to 10 minutes. Once the treatment session is complete, the radiation source is withdrawn back into the machine and the device is removed from the treatment area. The patient is discharged to return several days later for additional treatments.
- Low dose rate (LDR) brachytherapy
- Has been replaced by HDR brachytherapy for treatment of some cancers, but remains a cutting-edge technology for treatment of other cancers. UT Southwestern is currently pioneering a technique to treat recurrent brain tumors by depositing radioactive iodine “seeds” (similar to those used in prostate treatment) in the brain using minimally invasive, “through the nose” natural orifice surgery. The department also uses P-32 liquid phosphorus for relief of cystic brain tumors.
Calypso uses implantable electromagnetic transponders to continuously report the position of the tumor target during treatment. This enables physicians to exactly target tumors while sparing surrounding healthy tissue and structures such as the bladder. In an outpatient procedure similar to a biopsy, the transponders are implanted into the treatment area. Each transponder is about as small as a grain of rice. The transponders communicate with the Calypso 4-D Localization System using safe radiofrequency waves, allowing the radiation therapist to monitor the positioning of the target and make adjustments.
Cancer is frequently a moving target. Physicians employ a variety of imaging tools to match the location of tumors at the time of treatment with the planning location, in order to ensure accuracy. Imaging tests, such as cone-beam CT scans, are performed in the same room as the patient’s treatment, either immediately prior to or during treatment.
This state-of-the-art treatment allows doctors to use multiple radiation beams of varying lengths and intensity. The radiation beams may be moved dozens or hundreds of times during treatment, resulting in a radiation field that is “sculpted” in three dimensions. Rather than creating a uniform field of radiation, the radiation is delivered to precisely conform to the actual shape of the tumor, thus sparing surrounding healthy tissue.
Imaging systems located directly on the treatment machines, such as cone beam CT (CBCT), enable therapists to verify the positioning of the patient in real time – before, during, and after treatment – to verify targeting accuracy.
RapidArc continuously changes the gantry speed, dose rate, and shape of the treatment aperture to deliver treatments two to eight times faster than conventional therapy, reducing a typical 10- to 15-minute treatment to less than one minute in some cases. The advantage of the new technology is primarily to make therapy more convenient for patients who must undergo multiple treatments. Prostate patients frequently are candidates for RapidArc therapy. RapidArc does not reduce the total number of treatments patients require.