The validation of the treatment planning system BDTPS through an “ in-vivo ” comparison

Introduction. Boron Neutron Capture Therapy (BNCT) is a therapeutic technique, still under development, which exploits the interaction between thermal neutrons and B isotope administered to the patient using drugs. The reaction B(n,α) Li produces two high LET and short range fragments causing tumor cell damage. BNCT may be useful for treatment of locally advanced tumors that, in addition to the primary tumor mass, show microscopic infiltration into healthy tissue depths Correct boron level measurements both in tumor and in normal tissue are fundamental for therapeutic success. The method used in the past consists of an analysis of tissue samples taken during surgery [1][2][3]. However, the need to move towards non invasive techniques led to development of innovative methods. Nowadays, Positron Emission Tomography (PET) is able to provide boron concentration estimations through in vivo information [4][5]. The idea to couple the Treatment Planning System (TPS) to the information on the real boron distribution in the patient is the main added value of the new methodology set-up at DIMNP of University of Pisa, in collaboration with the JRC of Petten (NL). The methodology has been implemented in the new TPS, called BDTPS (Boron Distribution Treatment Planning System) [6], which takes into account the actual boron distribution in the human volume of interest, while the standard TPS assumes a uniform boron distribution, far from the reality. After an “in-phantom” validation at JRC (Petten) [7], an “in-vivo” validation of BDTPS was possible thanks to a Japanese researchers’ team collaboration. A Japanese 74 years old woman affected by parotid cancer was the medical case proposed for BDTPS implementation. Both CT and PET stacks, together with other information about the case, have been provided by the Tokai Research and Development Center of JAERI. Actually, BDTPS was implemented both in standard and in PET-based approach, in order to make possible an exhaustive comparative analysis between the two approaches. The first case, named Back, was necessary to derive the same results of Japanese standard system (JCDS) [8] used for the application.