[Superimposition alpha-autoradiography for basic study of neutron capture therapy (author's transl)].
Since Locher suggested the possibility of neutron capture therapy, a number of investigators have been making efforts to establish clinical application of this treatment. For success of this therapy one of the keys is to develop a proper boron compound with selective accumulation and high concentration in the tumor. So far, sodium mercaptoundecahydrododecaborate, Na2B12H11SH is the best candidate for this purpose with its high concentration and selectivity shown by chemical analysis. Nevertheless, histological study of boron uptake to know fine distribution in tissue is inevitable for evidence of effectiveness of clinical therapy. Cytological effects in neutron capture therapy largely depend on close association of B-10 with the tumor cell. B-10, being non-radioactive isotope, can not be used as a tracer for autoradiographical study of boron distribution in tissue. Instead, alpha particles produced by (n, alpha) reaction can be used for autoradiography which demonstrates not only location of boron in tissue but tracks by alpha particles expected to occur in actual neutron irradiation. Dielectric organic polymer has been calling attention for its ability to register heavy particles which was utilized for alpha autoradiography. Autoradiography by use of plastic film without nuclear emulsion has advantages; (1) simple procedures, (2) no darkroom needed, (3) a lower background obtainable, (4) little influence of temperature and moisture, (5) long standing material and so on. The disadvantage of this procedure is that tissue sections are easily damaged by strong alkalinity used for chemical etching. To solve this problem an overlapping histologic technique was worked out, permitting one to determine the relation of the heavy particle tracks to the intra and extracellular structures. Na2B12H11SH, a boron compound already in practical use, has been restudied by using this new technique. Autoradiograms showed favorable results with abundant alpha tracks over the tumor tissue in close relation to the cells and with very few tracks over the normal brain parenchyma. This technique is a useful means not only for further development of boron compounds but for other alpha emitters.
D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000378:metabolism; D001932:Brain Neoplasms / Q000378:metabolism / Q000532:radiotherapy*; D051379:Mice; D009502:Neutrons; D051381:Rats