Total Body Irradiation in Rapid ARC Sweeping Beam Technique
Purpose: Total body irradiation (TBI) is an external radiation therapy technique with which the entire body will receive the therapeutic dose during a treatment procedure. The main purpose of this research is to realize the sweeping beam technique to achieve TBI through the rapid arc technology of the Varian TrueBEAM linear accelerator. Following the CT images of the whole body prosthesis, irradiations have been performed through the treatment planning system (Eclipse 13.0, the most time-consuming process) in order to meet the dose requirements.
Materials and Methods: Experimentally we have carried out the total body irradiation in anterior/posterior views with a 6/10-MV photon beam. The distance from LIANC (TrueBeam) to a pediatric phantom or Alderson phantom is set to 312/219 cm, the Gafchromic-EBT3 films are placed at different positions of the pediatric phantom or Alderson phantom body for dose measurements, some radiation safety tools such as beam spoiler tray are employed to reduce the excessive radiation dose for radiation safety. A treatment planning system has also been investigatedto optimize the dose volume histogram of photon interactions throughout some OAR’s body parts. The patient/phantom is positioned on a low couch on the floor, the longitudinal axis of the body in the rotational plane of the linac. In the eclipse treatment planning system, the beam arrangement has been created through VMAT (volumetric modulated arc therapy) planning. Through the volumetric modulated arc, the gantry rotation has 40⁰-320⁰ clockwise and 320⁰-40⁰ counterclockwise fields with AP(anterior-posterior) and PA(posterior-anterior). The patient couch has setup at 90 degrees. After applying for four arc fields in AP and PA positions, have received a Plan Sum One Dose value.
Results: The PTV (Planning Target Volume) D95%, D90%, and D50% were 7.42, 8.40, and 12.64 Gy respectively, also minus PTV-lungs of D95%, D90%, and D50% were 8.59, 9.91, and 12.77 Gy. The obtained DVH (dose volume histogram) of right-left Lungs and PTV-lungs at D95% and D90% have less than 7 Gy and 10 Gy. The Dmean of the Right and left lungs were 8.66 and 8.57 Gy respectively.
Conclusions: This treatment technique can be used clinically and can be applied with each standard linac and in standard treatment rooms. Dose calculations were performed by the treatment planning system. Using the such technique, one can optimize the treatment planning for the maximum dose in tumors while the unnecessary dose can be reduced.
Keywords - Total Body Irradiation, Film Dosimetry, VMAT (Volumetric Modulated ARC Therapy), Treatment Planning System.