Dosimetrische und planungstechnische Untersuchungen der TomoTherapy (Accuray)

TomoTherapy offers a unique possibility of intensity-modulated radiation therapy. An high-energy, photon fan beam is formed by a binary multi-leaf collimator and a large number of such projections from different gantry angles are accumulated on a planning target volume. This technique achieves a homogeneous dose distribution in the target volume, mostly tumor tissue, with steep gradients to normal tissue. The advantages of the unique radiation technology of TomoTherapy were combined to develop a new method of robust whole-body radiation and to implement it in clinical routine. Reference conditions for absolute dosimetry prescribed by german and international dosimetry protocols cannot be achieved with the radiation therapy device TomoTherapyHD in several respects. Monte Carlo simulations answer questions that reduce uncertainties in absolute dosimetry. The uncertainties of dosimetry in small fields are examined in many publications. In this work, a fluence-weighted subfield size of helical TomoTherapy plans is defined for the first time. This parameter offers the possibility of describing the complexity of a radiation treatment plan and is a parameter for verifying the accuracy of measurement systems for patient quality assurance in clinical dosimetry. In this cumulative dissertation, background information on the described issues are described and the corresponding results are presented. This work contributes to further improving the quality assurance of radiation therapy and minimizing inaccuracies in clinical dosimetry.