Total body irradiation using helical tomotherapy: Set-up experience and in-vivo dosimetric evaluation

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Helical Tomotherapy (HT) offers potential advantages for total body irradiation (TBI) due to its ability to achieve homogeneous and conformal dose distributions.
• Precise patient repositioning is crucial for effective TBI, and HT may offer improvements over conventional techniques.

Purpose of the Study:

• To detail the implementation of Helical Tomotherapy for total body irradiation.
• To describe treatment preparation, planning, and dosimetric monitoring of TBI delivered between October 2016 and March 2019.

Main Methods:

• Irradiation protocols were established using physical phantoms to assess dose homogeneity and positioning accuracy.
• Sixteen patients received TBI at 12Gy in 6 fractions over 3 days.
• Pre-treatment quality assurance and in-vivo dosimetry using optically stimulated luminescence dosimeters (OSLD) were performed.

Main Results:

• Pre-treatment verifications demonstrated accurate dose distributions.
• In-vivo dosimetry with OSLD showed consistent measurements, with mean relative dose differences of +0.96% (armpit) and -2% (hands).
• Phantom studies illustrated the impact of positioning inaccuracies up to 2cm shifts.

Conclusions:

• The methodology for setting up an HT-based TBI protocol, including dosimetric evaluation and QA, was successfully implemented.
• Strong agreement between planned and delivered doses validates the reliability of OSLD for in-vivo dosimetry in HT-based TBI.