Measurement of α particle energy loss in biological tissue below 2 MeV

The energy loss of α particles crossing biological tissue at energies between 0.8 and 2.2 MeV has been measured. This energy range is very important for Boron Neutron Capture Therapy, based on the 10B(n,α)7Li reaction, which emits α particles with energies of 1.78 and 1.47 MeV. One of the methods used for the measurement of the boron concentration in tissue is based on the deconvolution of the α spectra obtained from neutron irradiation of thin (70 µm) tissue samples. For this technique, a knowledge of the behaviour of the energy loss of the particles in the irradiated tissue is of critical importance. In particular, the curve of the residual energy as a function of the distance travelled in the tissue must be known. In this paper, the results of an experiment carried out with an 241Am source and a series of cryostatic sections of rat-lung tissue are presented. The experimental measurements are compared with the results of Monte Carlo calculations performed with the MCNPX code

Boron Neutron Capture Therapy activity of diffused tumors at Triga Mark II in Pavia

The Boron neutron Capture Therapy research in Pavia has a long tradition: it begun more than 20 years ago at the Triga Mark II reactor of the University. A technique for the treatment of the hepatic metastases was developed, consisting in explanting the liver treated with 10B, irradiating it in the thermal column of the reactor, and reimplanting the organ in the patient. In the last years, the possibility of applying BNCT to the lung tumours using epithermal collimated neutron beams and without explanting the organ, is being explored. The principal obtained results of the BNCT research will be presented, with particular emphasis on the following aspects: a) the project of a new thermal column configuration to make the thermal neutron flux more uniform inside the explanted liver, b) the Monte Carlo study by means of the MCNP code of the thermal neutron flux distribution inside a patient’s thorax irradiated with epithermal neutrons, and c) the measurement of the boron concentration in tissues by (n,α) spectroscopy and neutron autoradiography

Studio di efficacia in vivo della Boron Neutron Capture Therapy applicata ai tumori polmonari diffusi

La BCNT è una radioterapia sperimentale adatta al trattamento di tumori diffusi inoperabili. Lo studio della BNCT dei tumori diffusi del polmone è in corso a Pavia, i risultati ne dimostrano la fattibilità. Il passo successivo è l’irraggiamento di ratti con metastasi polmonari nella colonna termica del reattore di Pavia per verificare l’efficacia del trattamento. Tramite simulazioni di Monte Carlo è stato studiato il set up di irraggiamento: la configurazione prevista permette di impartire dosi di radiazione terapeutiche al tumore, e sotto le soglie di tolleranza ai tessuti sani circostanti. Il tempo di irraggiamento è 10 minuti circa, compatibile con la durata dell’anestesia

Dose calculation in Sprague-Dawley rats affected by limb osteosarcoma for BNCT in vivo tests at the TRIGA reactor in Pavia

Osteosarcoma is the most common non-hematologic primary cancer that affects bones. The patients are typically very young, being the first incident peak between 10 and 20 years old. The conventional treatment is multiagent chemotherapy combined with extensive surgical resection, which can require the amputation of the entire limb. Nevertheless, the infiltrative growth of the tumour leads to a high incidence of local and distant recurrences that reduce the percentage of cured patients to less than 60%. Because of these poor outcomes, the identification of a new treatment option is very timely. A research project on the BNCT for osteosarcoma is ongoing at the University of Pavia. To perform the experiments, a suitable animal model has been developed, using immunosuppressed Sprague-Dawley rats inoculated with 2•107 UMR-106 cells through the femoral condyle. To load the tumour cells with 10B, innovative carriers, based on liposomes and nanoparticles and developed at the Universities of Florence and of Piemonte Orientale, are used. The in vivo experiments are performed at the thermal neutron facility of the TRIGA research nuclear reactor in Pavia. The original thermal column has been modified to house an irradiation chamber characterized by a non collimated neutron field with a low contamination of epithermal and fast neutrons as well as of photons. To spare the healthy organs of the animal, the irradiation set-up has been designed and optimized using the simulation code MCNP. In particular, a suitable neutron shield made of 95% 6Li enriched carbonate is used. The talk will show the results of the treatment planning, in particular the dose estimations obtained by the Monte Carlo calculations in the tumour and in the radiosensitive organs

Carborane-Conjugated 2-Quinolinearcarboxamide Ligands of the Translocator Protein for Boron Neutron Capture Therapy

Potential boron neutron capture therapy (BNCT) agents have been designed on the basis of the evidence about translocator protein (TSPO) overexpression on the outer mitochondrial membrane of tumor cells. The structure of the first TSPO ligand bearing a carborane cage (compound 2d) has been modified in order to find a suitable candidate for in vivo studies. The designed compounds were synthesized and evaluated for their potential interaction with TSPO and tumor cells. In vitro biological evaluation showed in the case of fluoromethyl derivative 4b a nanomolar TSPO affinity very similar to that of 2d, a significantly lower cytotoxicity, and a slightly superior performance as boron carrier toward breast cancer cells. Moreover, compound 4b could be used as a 19F magnetic resonance imaging (MRI) agent as well as labeled with 11C or 18F to obtain positron emission tomography (PET) radiotracers in order to apply the “see and treat” strategy in BNCT