TBI with a translational technique: A 15-year experience

• Published in: Physica medica 2016-09, Vol.32, p.254-254
• Main Authors: Koligliatis, T, Komi, P, Vasilakou, E, Pappas, N, Tsilimidou, A, Kouvati, K, Zambatis, B
• Format: Article
• Language: English
• Subjects: Radiology
• ISSN: 1120-1797; 1724-191X
• DOI: 10.1016/j.ejmp.2016.07.543

Introduction TBI has been long used as a conditioning regimen prior to BMT. There are both stationary and translational techniques depended on the facilities available in a radiotherapy department. Purpose To present our 15 years of experience on TBI with a translational technique. Dose computations, practical approaches and technical limitations are discussed. Materials and methods The translational TBI technique (theratron Co60 unit and a moving couch) has been employed for patient irradiation prior to BMT. 252 patients, varying in age from 6 to 55 years old (mean 35 ± 5), have been treated, submitted from the majority of BMT departments in Greece. The computations take place using a commercial TPS (theraplan-plus) to calculate the dose to either lung taking patient in-homogeneities into account. Patient translation has been approached with photon beams next to each other ((50 × 30) cm, SSD = 149 cm), along the axis of the patient, with a 2 cm space interval. The average dose to each lung is then obtained from DVH and each filter thickness determined. Bolusing is used to minimize patient thickness variation. Results The average dose to each lung is ∼750 cGy whereas the midline dose at the umbilicus is 1200 cGy (2 fractions × 3 days). Filter thickness may not be constant (i.e. 1 mm lead strip added close to lung middle). Electron beams (10–12 MeV) are employed to irradiate the area of the thoracic wall under the filter to reach a dose of 1000 cGy. The estimated overall lung burden is ∼850 cGy for 60% of either lung. A limitation of this technique is the size of a patient due to maximum field size available (maximum = 55 cm) and in some cases patient thickness (maximum = 30 cm). Conclusion The translational TBI technique provides superior dose uniformity compared to stationary ones at the expense of time and longer preparation.