Skin dose study of chest wall treatment with tomotherapy.

PURPOSE: The tangential-beam technique frequently presents challenges in homogeneity of radiation dose to the target. To ensure an adequate dose to the skin, a bolus is often used. Tomotherapy has already been shown to improve target conformity and homogeneity in other disease sites. Because of the tangential delivery technique and lack of flattening filter in TomoTherapy accelerators, we hypothesize that during chest wall irradiation using tomotherapy, the skin dose will be adequate without bolus.

MATERIALS AND

METHODS

This study compares the dosimetric differences between tomotherapy chest wall irradiation and traditional linear accelerator-based tangential-beam technique. Tomotherapy treatment plans with and without bolus were compared with tangentialbeam plans. Plans were also generated for phantom studies, and point doses were measured using MOSFET dosimetry to verify the adequate skin dose. Monte Carlo simulations of static beams of both techniques were performed, and dosimetry was compared.

RESULTS

Monte Carlo simulations and measurements confirmed that beams from tomotherapy deliver a higher skin dose than a standard linear accelerator. Skin dose also increases with the incident angle of the beams.

CONCLUSION

Because of the characteristics of the tomotherapy beam and delivery technique, chest wall treatment plans from tomotherapy showed adequate skin dose [more than 75% of prescribed planning target volume (PTV) dose] even without bolus.