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Radiolabeled Nanoparticles for Cancer Diagnosis
Published in D. Sakthi Kumar, Aswathy Ravindran Girija, Bionanotechnology in Cancer, 2023
R. G. Aswathy, D. Sakthi Kumar
The most commonly employed radioisotopes for SPECT imaging include technetium (99Tc, t1/2: 6.0 h), indium (111In, t1/2: 2.8 days), and radioiodine (131I, t1/2: 8.0 days) and other radioisotopes as given in Table 3.1. Technetium-99m (99mTc, is an isotope of technetium, short-lived metastable radionuclide) is the most commonly employed radionuclide for nuclear imaging. Owing to the remarkable physical properties of 99mTc including the short half-life (6 h) and gamma photon emission (140 keV), this material is highly beneficial for efficient imaging as well as good for patient’s safety. Additionally, 99mTc holds latent chemical properties, which allow this material to be used in kits of numerous types for labeling for multipurpose diagnostic applications. SPECT is often used for imaging ligands, including antibodies, peptides, hormones, and selectins, which are labeled with 99mTc or with other radioisotopes. These molecules slowly diffuse into tissue and exhibit slow clearance from blood that extends for several hours to even days. Some SPECT isotopes with long half-life, such as thallium-201 (201Tl), tin-117m (117mSn), and iodine-125 (125I), are used for imaging of slow biological processes, including cell division, inflammatory process, and effect of therapeutic radiopharmaceuticals.
Radiopharmaceuticals for Diagnostics
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Jim Ballinger, Jacek Koziorowski
Technetium-99m (99mTc) is the most commonly used radionuclide for gamma imaging since its introduction ~1970, being used in ~ 85 per cent of nuclear medicine procedures worldwide. 99mTc (t½ 6 h; IT 99.99%; principal γ emission 140.5 keV; 89% abundance) has mainly been produced by decay of Molybdenum-99 (99Mo) in a 99Mo/99mTc generator system. 99Mo (t½ 66 h) is a nuclear fission product of Uranium-235, the [235U](n,f)[99Mo] reaction having a yield of 6.1 per cent. 99mTc is conveniently available on-site from a generator system in which a chromatographic column (generally aluminium oxide) is loaded with 99Mo which continually decays to 99mTc. The two radionuclides can be readily separated because 99Mo remains on the column when it is eluted with 0.9 per cent sodium chloride solution (saline), while 99mTc emerges in the eluate. The ratio between the half-lives of the parent and daughter radionuclides is such that maximal yields of 99mTc are obtained at 24-h intervals, perfect for once-a-day elution. Because of the gradual decay of 99Mo and concomitant reduced yield of 99mTc, the generator is generally replaced on a weekly basis. The generator is autoclaved by the manufacturer and, as long as the end-user maintains aseptic technique, the eluate remains sterile and suitable for direct injection into patients [1].
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.
PHWR Reactivity Device Incremental Macroscopic Cross Sections and Reactivities for a Molybdenum-Producing Bundle and a Standard Bundle
Published in Nuclear Technology, 2022
In diagnostic nuclear medicine, a radiopharmaceutical consisting of a radioactive atom bound to a substrate molecule is administered to a patient to obtain functional information about the patient’s organs and to diagnose various medical conditions. Technetium-99 m (99mTc) is the most commonly used radionuclide in diagnostic nuclear medicine, 99mTc is produced from the radioactive decay of its parent nuclide, molybdenum-99 (99Mo). 99mTc is used in approximately 30 million procedures per year, accounting for 80% of all nuclear medicine diagnostic procedures worldwide.1 Neither 99Mo nor its daughter product, 99mTc, exist naturally. The parent nuclide, 99Mo, is most commonly produced through the fission of uranium-235 (235U) in nuclear reactors with a fission yield of 6.1% (Ref. 2). 99Mo has a half-life of ~4 days, which means that it reaches saturation activity in ~20 days, after which it needs to be harvested.3
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
Radiopharmaceuticals based on technetium-99m (99mTc) have become important tools for the diagnosis of various diseases over the past four decades. Currently, hundreds of 99mTc-based compounds have been used in nuclear medicine, generating a volume of exams corresponding to almost 80% of the clinical routine of a nuclear medicine service [1]. The high rate of use of 99mTc-based radiopharmaceuticals is due to the excellent nuclear decay properties such as: physical half-life of 6.03 h and emission of pure gamma radiation (140 keV gamma ray energy). The availability of the 99mMo/99mTc generator allows: (i) distribution to remote sites; (ii) the possibility of the radiometal reaching several states of oxidation, (iii) coordination, giving rise to different radiopharmaceuticals, from simple reconstitution of kits of lyophilized reagents and (iv) the low rate of adverse reactions of these agents when compared to other contrast agents. These metallic radionuclides have received the most attention not only to their nuclear physical characteristics, but also to their inherent capacity to coordinate with a great variety of ligands (molecules, monoclonal antibodies, small peptides, nanoparticles, etc.) making it possible to produce a variety of complexes with specific characteristics, which is a major advantage of 99mTc for radiopharmaceutical development [2, 3].
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