A revision of the γ-evaluation concept for the comparison of dose distributions.
The Chi index described in the article 'A revision of the γ-evaluation concept for the comparison of dose distributions' by Bakai et al (Phys. Med. Biol. 2003 48 3543-53) indicates that smooth acceptance tubes, defining upper and lower limits of dose difference and distance to agreement, can be pre-defined for a given dose distribution based on the local dose gradient. Mathematical analysis and simulations indicate that the Chi index as described by Bakai et al does not produce smooth acceptance criteria in rapidly varying dose gradients. Instead, 'horns' are generated in the acceptance tubes which lead to the production of unacceptably large acceptance criteria and the possibility of false negatives.
Crown Princess Mary Cancer Centre, Westmead, NSW, Australia.
Trevor
T
Moodie
Jonathan
J
Sykes
Romuald
R
Gajewski
D000465:Algorithms; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008954:Models, Biological; D011785:Quality Assurance, Health Care / Q000379:methods*; D011835:Radiation Protection / Q000379:methods*; D011874:Radiometry / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*