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All clinical experience with NCT to date is with boron-10; hence this method is known as boron neutron capture therapy (BNCT). [1] Use of another non-radioactive isotope, such as gadolinium , has been limited to experimental animal studies and has not been done clinically.
Gadolinium crystallizes in the hexagonal close-packed α-form at room temperature. At temperatures above 1,235 °C (2,255 °F), it forms or transforms into its β-form, which has a body-centered cubic structure. [10] The isotope gadolinium-157 has the highest thermal-neutron capture cross-section among any stable nuclide: about 259,000 barns.
Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus. [1] Since neutrons have no electric charge, they can enter a nucleus more easily than positively charged protons , which are repelled electrostatically .
No cancer therapy is without the risk of side effects. Neutron therapy is a very powerful nuclear scalpel that has to be utilized with exquisite care. For instance, some of the most remarkable cures it has been able to achieve are with cancers of the head and neck. Many of these cancers cannot effectively be treated with other therapies.
Gadolinium has a larger capture cross-section, around 49,000 barns, and this occurs on the orders of microseconds after the free neutron is emitted. Additionally, the capture event in gadolinium produces an 8 MeV cascade of 2- 3 gammas. [6] The nature of neutron producing processes associated in neutrino interactions is poorly understood ...
The parent isotope germanium-68 is the longest-lived (271 days) of the radioisotopes of germanium. It has been produced by several methods. [1] In the U.S., it is primarily produced in proton accelerators: At Los Alamos National Laboratory, it may be separated out as a product of proton capture, after proton irradiation of Nb-encapsulated gallium metal. [2]
Gadolinium isotopes have 10 metastable isomers, with the most stable being 143m Gd (t 1/2 = 110 seconds), 145m Gd (t 1/2 = 85 seconds) and 141m Gd (t 1/2 = 24.5 seconds). The primary decay mode at atomic weights lower than the most abundant stable isotope, 158 Gd, is electron capture, and the primary mode at higher atomic weights is beta decay.
Gallium scan showing panda (A) and lambda (B) patterns, considered specific for sarcoidosis in the absence of histological confirmation. In the past, the gallium scan was the gold standard for lymphoma staging, until it was replaced by positron emission tomography (PET) using 18 F-fluorodeoxyglucose (FDG).