Neutron capture therapy with Gadolinium-157

Allen, BJ; McGregor, BJ; Martin, RF

Neutron capture therapy with Gadolinium-157

Date

1989

Authors

Allen, BJ

McGregor, BJ

Martin, RF

Abstract

The nuclear characteristics of the boron-IO neutron capture reaction that make it so suitable for neutron capture therapy are the high capture cross-section (3838 barns), the high linear energy transfer (LET > 100 keV/um) and short range (6 — 10 um) of the reaction products [8]. If the boron-IO atom is taken up by the cancer cell, on average 2.33 MeV of high LET radiation is deposited within the cell per capture event, causing double strand breaks (dsb) in the DNA and mitotic impotence. There are other neutron capture reactions with larger cross-sections but these produce gamma-rays and have been considered to be of little importance to radiotherapy. However these reaction invariably lead to internal conversion and subsequent emission of Auger electrons. Experiments with 1251 have demonstrated that dsb can be induced upon decay of 1251 that is either covalently incorporated into DNA [10] or noncovalently associated with DNA [11]. Monte Carlo studies of 1251 decay by electron capture or internal conversion indicate that in the condensed phase 21 Auger electrons are emitted per decay with total energy of 19.8 kev [2]. The range of the majority of these electrons is of molecular dimensions and the ionisation density exceeds that of a 5 MeV alpha particle [1]. Further, charge effects caused by the generation of electrons may well be the major cause of damage [4]. Thus critical damage to DNA can result from highly localised, microscopic stochastic patterns of energy deposition. Internal conversion also occurs following neutron capture in 157Gd [7], and because this isotope has a neutron capture cross-section 67 times larger than 10B it was of interest to see whether DNA dsbs could be induced by neutron capture of DNA bound 157Gd. neutron capture event, and the electron holes so created in the K and L shells are filled by Auger and Coster-Kronig transitions, with the concomitant emission of low energy electrons with very short range. In a recent experiment at the Moata reactor [9], we were able to demonstrate that Auger electron emission from neutron capture in 157Gd was able to induce double strand breaks in plasmid DNA. It is therefore of interest to calculate the neutron-gamma-ray transport in tissue to evaluate the effect of the 7.937 MeV binding energy released in the capture reaction. © 1989Urbun &Vogel GMBH

Description

Physical copies held by ANSTO Library at DDC: 616.9440642/30

Keywords

Neutron capture therapy, Cross sections, Energy transfer, keV range 01-10, Monte Carlo Method, Auger electron spectroscopy, DNA, Gadolinium 157, Radiation doses, RBE, Radiopharmaceuticals, Thermal neutrons, Toxicity

Citation

Allen, B. J., McGregor, B. J., & Martin, R. F. (1989). Neutron capture therapy with gadolinium-157. Paper presented to the Third International Symposium on Neutron Capture Therapy, Bremen 31 May-3 June 1988, in Strahlenther und Onkologie, 165(2-3), 156-158.