Explore chapters and articles related to this topic
Subsurface Processes
Published in Stephen M. Testa, Geological Aspects of Hazardous Waste Management, 2020
Another term that needs to be defined before we proceed is the term “chemical species,” which refers to the actual molecular form that the contaminant (or any substance) takes in the porous medium and strongly affects how that contaminant will migrate through the subsurface. As an example, technetium (Tc) is both a highly radioactive contaminant and a toxic metal contaminant. Under reducing conditions (usually occurring when molecular oxygen is absent and organic matter is present, often a condition prevailing below the water table), Tc is generally immobile as a metal. However, under oxidizing conditions, as occurs in the unsaturated zone or vadose zone, between the earth’s surface and the water table, Tc forms a complex species with oxygen, called a pertechnetate ion, TcO4−, which is highly mobile and is not held up, or retarded, by most soils, sediments, or rocks. Strategies for waste disposal, handling, and remediation require knowledge of the speciation of the contaminant, information gained almost exclusively through experimental studies under relevant conditions.
Images from Radioactivity: Radionuclide Scans, SPECT, and PET
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
Many radionuclides have been identified that both emit an appropriate gamma ray energy and form a chemical compound of interest. Technetium-99m can now be attached to so many useful compounds that it is extremely widely used in nuclear medicine imaging. Gamma camera scans with technetium-99m and other radionuclides are used to image the skeleton, urinary tract, lungs, heart, liver, and thyroid gland, among other applications. For example, the distribution of technetium-99m-labeled red blood cells can be used to trace the flow of blood and indicate the quality of circulation throughout the body. Others radiopharmaceuticals are taken up preferentially by a particular organ or by tumors. For example, a chemical compound called technetium-99m-HIDA normally is concentrated in the gallbladder. Thus, an abnormal absence of radioactive tracer compound could indicate impaired circulation in a region of the body (in the first case) or blockage of the gallbladder (in the second). In scintimammography, a technetium-99m tracer compound can be used to image tumors in breast cancer.
Radioisotope Production and Application
Published in Paul R. Bolton, Katia Parodi, Jörg Schreiber, Applications of Laser-Driven Particle Acceleration, 2018
Technetium-99m: The metastable nuclear state 99mTc emits a single gamma photon so it is useful for 3D images (SPECT) as well as for 2D images (planar scintigraphy). The advantage of Technetium is that it is suitable for many applications, such as in medronic acid with 99mTc, a molecule that is often used to study bone abnormalities and metastases by imaging (gamma imaging) the gamma emission pattern. 99mTc is obtained by the β-decay of 99Mo, as already indicated. The precursor/tracer radionuclide pair 99Mo/99mTc is the radiotracer most widely used in the world.
Technetium-99m metastable radiochemistry for pharmaceutical applications: old chemistry for new products
Published in Journal of Coordination Chemistry, 2019
Bianca Costa, Derya Ilem-Özdemir, Ralph Santos-Oliveira
The chemical element technetium whose symbol is Tc has atomic number 43 and is located in group 7 (7B) of the periodic table. All isotopes of technetium are radioactive. The two most prevalent isotopes are 99mTc formed from the decay of 99Mo and 99Tc, the decay product of 99mTc. 99Tc (βmax: 274 keV) is a significant by-product of U-235 fission (6% thermal neutron yield). With a half-life of 2.1 × 105 years, 99Tc can build up in the environment and can be obtained in macroscopic quantities. In the metallic form, 99Tc is a transition metal, silvery gray. Like the other transition metals, 99Tc presents peculiar properties, such as varied colors, various oxidation numbers and different coordination numbers, which result from the existence of a sub-level “d” partially filled in the valence layer [11].
A Feasibility Study on the Transmutation of 100Mo to 99mTc with Laser-Compton Scattering Photons
Published in Nuclear Technology, 2018
Jiyoung Lee, Haseeb ur Rehman, Yonghee Kim
Technetium-99m is an important medical radioisotope used in over 40 million nuclear-medicine procedures performed throughout the world each year. Its short half-life of 6 h linked with an easily detectable but relatively safe 142.7 keV gamma decay has made it an ideal radioisotope for medical applications. When coupled with suitable chemical compounds, it allows for the diagnosis and examination of specific physiological processes, making it essential for noninvasive medical procedures worldwide. Today, about 80% to 85% of all 99mTc used in these procedures is obtained as decay product of 99Mo. Consequently, the world’s demand of 99Mo is estimated to be between 10 000 and 12 000 six-day curiesaA 6-day curie is the measurement of the remaining radioactivity of 99Mo six days after it leaves the processing facility. per week.1
Molybdenum-99 from Molten Salt Reactor as a Source of Technetium-99m for Nuclear Medicine: Past, Current, and Future of Molybdenum-99
Published in Nuclear Technology, 2023
Jisue Moon, Kristian Myhre, Hunter Andrews, Joanna McFarlane
The radionuclide 99mTc is a metastable nuclear isomer used in tens of millions of medical diagnostic procedures annually. However, because of its short half-life (i.e., 6 h), this important medical isotope cannot be stored and must be used immediately upon production or repeatedly produced from generators that bear its parent isotope. Technetium-99m is produced from molybdenum-99, which itself is a result of uranium-235 fission.