The Measurement of Gadolinium Concentration in Rat Brain Tumor with NMR Analyzer for Neutron Capture Therapy

Abstract

Sufficient concentration of gadolinium or boron in brain tumor is key in performing effective neutron capture therapy. As we know, the effect of neutron capture reaction is determined by the concentration of gadolinium or boron in tumor, the density of the neutron flux and radiation time. And the ratios of gadolinium concentrations in the tumor to that in normal tissues and to that in blood are important keys for successful neutron capture therapy. Gadolinium-DTPA is a commercially available and clinically safe agent for contrast enhancement in magnetic resonance imaging. The pharmacodynamics of gadolinium-DTPA in rat blood and brain tumor after intravenous infusion shows fast peak and fast wash out(1). In order to perform effective gadolinium neutron capture therapy we must develop new gadolinium compounds which show significant and continuous uptake in brain tumor. We have reported continuous significant uptake of boron or gadolinium in rat brain tumor using porphyrin derivatives(2) or monoclonal antibody(3). These gadolinium porphyrin derivatives, named Gd-ATN-10, was developed for neutron capture therapy. This molecule contains the porphyrin structure and manganese and gadolinium-DTPA(Fig.1). Gadolinium is a paramagnetic metal, which increases the intensity of T1 weighted magnetic resonance imaging and decreases the T1 relaxation time.