Monte Carlo Dose Distribution of Gadolinium NCT for Brain Tumors of Different Site and Level of Necrosis

Abstract

Almost all the energy released in the gadolinium-157 thermal neutron capture is emitted through prompt gamma rays with a spectrum up to 7.9 MeV. Low energy internal conversion electrons, mainly in the range 80–280 keV, are also emitted. An FDA approved carrier, Gd-DTPA, the gadolinium contrast agent for magnetic resonace imaging (MRI), is currently used clinically. Gadolinium uptake in brain tumors is provided by simple diffiusion through the disrupted blood-brain barrier. The dynamics of the uptake and washout phases are not identical because there are biological processes favoring the transport of gadolinium carriers into the extravascular space.¹ Doses of GdDTPA larger than those commonly used for MRI, or multiple injections can produce high gadolinium concentrations in tumor.