Optimizing Of Spoiler Thickness For Total Body Irradiation (TBI) Utilizing Tomotherapy Technology

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Ziadat, Bashar
Wang, C.-K. Chris
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Delivering total body irradiation (TBI) with a Tomotherapy unit presents a unique challenge: minimizing lung dose while achieving a high skin dose. Acrylic spoilers offer a potential solution by slightly attenuating the incident photon beam, and therefore, reduce the lung dose. The spoilers can also increase the skin dose by producing electrons via Compton scattering interactions of the incident photon beams. This study aimed to identify the optimal spoiler thickness for clinical application for TBI with a Tomotherapy unit. The dosimetric effects of these spoilers were investigated computationally and experimentally. The results of this study show that, among the various thicknesses (0.0, 0.635, 0.953, and 1.588 cm) of the spoiler), the thickest (i.e. 1.588 cm) spoiler yielded the lowest lung dose and the highest skin dose. This conclusion is further supported by the experimentally obtained dose data from the EBT3 films that were mounted on the ArcCHECK phantom and irradiated with the Tomotherapy machine. The ion chamber measurements within the ArcCHECK system demonstrated good agreement with the TPS calculations, exhibiting a maximum error of only 0.5% for lung dose. Furthermore, the dose data measured with the ion chamber also show that lowest lung dose was achieved with the thickest spoiler.
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