General | |
---|---|
Symbol | 90Y |
Names | yttrium-90, 90Y, Y-90 |
Protons (Z) | 39 |
Neutrons (N) | 51 |
Nuclide data | |
Half-life (t1/2) | 64.60±0.43 h [1] |
Isotopes of yttrium Complete table of nuclides |
Yttrium-90 (90
Y
) is a radioactive isotope of yttrium. [2] Yttrium-90 has found a wide range of uses in radiation therapy to treat some forms of cancer. [3] Along with other isotopes of yttrium, it is sometimes called radioyttrium.
90
Y
undergoes beta particles emissions/decay (β− decay) to zirconium-90 with a half-life of 64.1 hours [3] and a decay energy of 2.28 MeV with an average beta energy of 0.9336 MeV. [4] It also produces 0.01% 1.7 MeV [5] photons during its decay process to the 0+ state of 90Zr, followed by pair production. [6] The interaction between emitted electrons and matter can lead to the emission of Bremsstrahlung radiation.
Yttrium-90 is produced by the nuclear decay of strontium-90 which has a half-life of nearly 29 years and is a fission product of uranium used in nuclear reactors. As the strontium-90 decays, chemical high-purity separation is used to isolate the yttrium-90 before precipitation. [7] [8] Yttrium-90 is also directly produced by neutron activation of natural yttrium targets (Yttrium is mononuclidic in 89Y) in a nuclear research reactor.
90Y plays a significant role in the treatment of hepatocellular carcinoma (HCC), leukemia, and lymphoma, although it has the potential to treat a range of tumors. [9] Trans-arterial radioembolization is a procedure performed by interventional radiologists, in which 90Ymicrospheres are injected into the arteries supplying the tumor. [10] The microspheres come in two forms: resin, in which 90Y is bound to the surface, and glass, in which 90Y is directly incorporated into the microsphere during production. [11] Once injected, the microspheres become lodged in blood vessels surrounding the tumor and the resulting radiation damages the nearby tissue. [12] The distribution of the microspheres is dependent on several factors, including catheter tip positioning, distance to branching vessels, rate of injection, properties of particles, like size and density, and variability in tumor perfusion. [12] Radioembolization with 90Y significantly prolongs time-to-progression (TTP) of HCC, [13] has a tolerable adverse event profile, and improves patient quality of life more than do similar therapies. [14] 90Y has also found uses in tumor diagnosis by imaging the Bremsstrahlung radiation released by the microspheres. [15] Positron emission tomography after radioembolization is also possible. [16]
Following treatment with 90Y, imaging is performed to evaluate 90Y delivery and absorption to evaluate coverage of target regions and involvement of normal tissue. This is typically performed using Bremsstrahlung imaging with single-photon emission computed tomography CT (SPECT/CT), or using 90Y position imaging with positron emission tomography CT (PET/CT).
As 90Y undergoes beta decay, broad spectrum bremsstrahlung radiation is emitted and is detectable with standard gamma cameras or SPECT. [17] [18] These modalities provide information about radioactive uptake of 90Y, however, there is poor spatial information. [17] [18] Consequently, it is challenging to delineate anatomy and thereby evaluate tumor and normal tissue uptake. This led to the development of SPECT/CT, which combines the functional information of SPECT with the spatial information of CT to allow for more accurate 90Y localization. [17] [18]
PET/CT and PET/MRI have superior spatial resolution compared to SPECT/CT because PET detects positron pairs produced from the decay of emitted positrons, negating the requirement for a physical collimator. [17] [18] This allows for better assessment of microsphere distribution and dose absorption. However, both PET/CT and PET/MRI are less widely available and more costly. [17] [18]
Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, regional chemical composition, and absorption. Different tracers are used for various imaging purposes, depending on the target process within the body.
Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to reveal internal structures hidden by the skin and bones, as well as to diagnose and treat disease. Medical imaging also establishes a database of normal anatomy and physiology to make it possible to identify abnormalities. Although imaging of removed organs and tissues can be performed for medical reasons, such procedures are usually considered part of pathology instead of medical imaging.
Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults and is currently the most common cause of death in people with cirrhosis. HCC is the third leading cause of cancer-related deaths worldwide.
Nuclear medicine, is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear imaging is, in a sense, radiology done inside out, because it records radiation emitted from within the body rather than radiation that is transmitted through the body from external sources like X-ray generators. In addition, nuclear medicine scans differ from radiology, as the emphasis is not on imaging anatomy, but on the function. For such reason, it is called a physiological imaging modality. Single photon emission computed tomography (SPECT) and positron emission tomography (PET) scans are the two most common imaging modalities in nuclear medicine.
A radioligand is a microscopic particle which consists of a therapeutic radioactive isotope and the cell-targeting compound - the ligand. The ligand is the target binding site, it may be on the surface of the targeted cancer cell for therapeutic purposes. Radioisotopes can occur naturally or be synthesized and produced in a cyclotron/nuclear reactor. The different types of radioisotopes include Y-90, H-3, C-11, Lu-177, Ac-225, Ra-223, In-111, I-131, I-125, etc. Thus, radioligands must be produced in special nuclear reactors for the radioisotope to remain stable. Radioligands can be used to analyze/characterize receptors, to perform binding assays, to help in diagnostic imaging, and to provide targeted cancer therapy. Radiation is a novel method of treating cancer and is effective in short distances along with being unique/personalizable and causing minimal harm to normal surrounding cells. Furthermore, radioligand binding can provide information about receptor-ligand interactions in vitro and in vivo. Choosing the right radioligand for the desired application is important. The radioligand must be radiochemically pure, stable, and demonstrate a high degree of selectivity, and high affinity for their target.
Transcatheter arterial chemoembolization (TACE) is a minimally invasive procedure performed in interventional radiology to restrict a tumor's blood supply. Small embolic particles coated with chemotherapeutic drugs are injected selectively through a catheter into an artery directly supplying the tumor. These particles both block the blood supply and induce cytotoxicity, attacking the tumor in several ways.
Neuroimaging is the use of quantitative (computational) techniques to study the structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Increasingly it is also being used for quantitative research studies of brain disease and psychiatric illness. Neuroimaging is highly multidisciplinary involving neuroscience, computer science, psychology and statistics, and is not a medical specialty. Neuroimaging is sometimes confused with neuroradiology.
A gallium scan is a type of nuclear medicine test that uses either a gallium-67 (67Ga) or gallium-68 (68Ga) radiopharmaceutical to obtain images of a specific type of tissue, or disease state of tissue. Gallium salts like gallium citrate and gallium nitrate may be used. The form of salt is not important, since it is the freely dissolved gallium ion Ga3+ which is active. Both 67Ga and 68Ga salts have similar uptake mechanisms. Gallium can also be used in other forms, for example 68Ga-PSMA is used for cancer imaging. The gamma emission of gallium-67 is imaged by a gamma camera, while the positron emission of gallium-68 is imaged by positron emission tomography (PET).
Copper-64 (64Cu) is a positron and beta emitting isotope of copper, with applications for molecular radiotherapy and positron emission tomography. Its unusually long half-life (12.7-hours) for a positron-emitting isotope makes it increasingly useful when attached to various ligands, for PET and PET-CT scanning.
TheraSphere is a radiotherapy treatment for hepatocellular carcinoma (HCC) that consists of millions of microscopic, radioactive glass microspheres being infused into the arteries that feed liver tumors. These microspheres then embolize, lodging themselves in the liver's capillaries and bathing the malignancy in high levels of yttrium-90 radiation. It is currently approved as a Humanitarian Device, meaning effectiveness has not been proven, for patients as a neoadjuvant to surgery or transplantation by the U.S. Food and Drug Administration and is being used at a number of clinical centers in the United States.
Selective internal radiation therapy (SIRT), also known as transarterial radioembolization (TARE), radioembolization or intra-arterial microbrachytherapy is a form of radionuclide therapy used in interventional radiology to treat cancer. It is generally for selected patients with surgically unresectable cancers, especially hepatocellular carcinoma or metastasis to the liver. The treatment involves injecting tiny microspheres of radioactive material into the arteries that supply the tumor, where the spheres lodge in the small vessels of the tumor. Because this treatment combines radiotherapy with embolization, it is also called radioembolization. The chemotherapeutic analogue is called chemoembolization, of which transcatheter arterial chemoembolization (TACE) is the usual form.
Nuclear medicine physicians, also called nuclear radiologists or simply nucleologists, are medical specialists that use tracers, usually radiopharmaceuticals, for diagnosis and therapy. Nuclear medicine procedures are the major clinical applications of molecular imaging and molecular therapy. In the United States, nuclear medicine physicians are certified by the American Board of Nuclear Medicine and the American Osteopathic Board of Nuclear Medicine.
SIR-Spheres microspheres are used to treat patients with unresectable liver cancer. These are mostly patients with hepatocellular carcinoma (HCC), metastatic colorectal cancer (mCRC), or metastatic neuroendocrine tumours (mNET).
Preclinical imaging is the visualization of living animals for research purposes, such as drug development. Imaging modalities have long been crucial to the researcher in observing changes, either at the organ, tissue, cell, or molecular level, in animals responding to physiological or environmental changes. Imaging modalities that are non-invasive and in vivo have become especially important to study animal models longitudinally. Broadly speaking, these imaging systems can be categorized into primarily morphological/anatomical and primarily molecular imaging techniques. Techniques such as high-frequency micro-ultrasound, magnetic resonance imaging (MRI) and computed tomography (CT) are usually used for anatomical imaging, while optical imaging, positron emission tomography (PET), and single photon emission computed tomography (SPECT) are usually used for molecular visualizations.
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