Sodium pertechnetate is the inorganic compound with the formula NaTcO₄. This colourless salt contains the

pertechnetate The pertechnetate ion () is an oxyanion with the chemical formula . It is often used as a convenient water-soluble source of isotopes of the radioactive element technetium (Tc). In particular it is used to carry the 99mTc isotope (half-life 6 hou ...

anion, . The radioactive anion is an important

radiopharmaceutical Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotopes. Radiopharmaceuticals can be used as diagnostic and therapeutic agents. Radiopharmaceuticals emit radiation themselves, which ...

for

diagnostic Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine " cause and effect". In systems engin ...

use. The advantages to include its short

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...

of 6 hours and the low radiation exposure to the patient, which allow a patient to be injected with activities of more than 30 millicuries. is a precursor to a variety of derivatives that are used to image different parts of the body.

Chemistry

is the starting material for most of the chemistry of technetium. Pertechnetate salts are usually colorless. is produced by oxidizing technetium with nitric acid or with hydrogen peroxide. The pertechnetate anion is similar to the

permanganate A permanganate () is a chemical compound containing the manganate(VII) ion, , the conjugate base of permanganic acid. Because the manganese atom is in the +7 oxidation state, the permanganate(VII) ion is a strong oxidizing agent. The ion is a tr ...

anion but is a weaker

oxidizing agent An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...

. It is tetrahedral and diamagnetic. The standard electrode potential for / is only +0.738 V in acidic solution, as compared to +1.695 V for /. Because of its diminished oxidizing power, is stable in alkaline solution. is more similar to . Depending on the reducing agent, can be converted to derivatives containing Tc(VI), Tc(V), and Tc(IV). In the absence of strong complexing ligands, is reduced to a +4 oxidation state via the formation of hydrate.

Pharmaceutical use

The half-life of is long enough that labelling synthesis of the

and scintigraphic measurements can be performed without significant loss of radioactivity. The energy emitted from is 140 keV, which allows for the study of deep body organs. Radiopharmaceuticals have no intended pharmacologic effect and are used in very low concentrations. Radiopharmaceuticals containing are currently being applied in the determining morphology of organs, testing of organ function, and scintigraphic and emission tomographic imaging. The gamma radiation emitted by the radionuclide allows organs to be imaged ''in vivo'' tomographically. Currently, over 80% of radiopharmaceuticals used clinically are labelled with . A majority of radiopharmaceuticals labelled with are synthesized by the reduction of the pertechnetate ion in the presence of ligands chosen to confer organ specificity of the drug. The resulting compound is then injected into the body and a "gamma camera" is focused on sections or planes in order to image the spatial distribution of the .

Specific imaging applications

is used primarily in the study of the thyroid gland - its morphology, vascularity, and function. and

iodide An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine de ...

, due to their comparable charge/radius ratio, are similarly incorporated into the thyroid gland. The pertechnetate ion is not incorporated into the

thyroglobulin Thyroglobulin (Tg) is a 660 kDa, dimeric glycoprotein produced by the follicular cells of the thyroid and used entirely within the thyroid gland. Tg is secreted and accumulated at hundreds of grams per litre in the extracellular compartment ...

. It is also used in the study of blood perfusion, regional accumulation, and cerebral lesions in the brain, as it accumulates primarily in the

choroid plexus The choroid plexus, or plica choroidea, is a plexus of cells that arises from the tela choroidea in each of the ventricles of the brain. Regions of the choroid plexus produce and secrete most of the cerebrospinal fluid (CSF) of the central nerv ...

. Sodium pertechnetate cannot pass through the blood–brain barrier. In addition to the salivary and thyroid glands, localizes in the stomach. is renally eliminated for the first three days after being injected. After a scanning is performed, it is recommended that a patient drink large amounts of water in order to expedite elimination of the radionuclide. Other methods of administration include intraperitoneal, intramuscular, subcutaneous, as well as orally. The behavior of the ion is essentially the same, with small differences due to the difference in rate of absorption, regardless of the method of administration.

Other reactions involving the pertechnetate ion

*Radiolysis of in nitrate solutions proceeds through the reduction to which induces complex disproportionation processes: :

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*Pertechnetate can be reduced by to give . *Pertechnetate is also reduced to Tc(IV/V) compounds in alkaline solutions in nuclear waste tanks without adding catalytic metals, reducing agents, or external radiation. Reactions of mono- and disaccharides with yield Tc(IV) compounds that are water-soluble.

References

{{Thyroid hormone receptor modulators Pertechnetates Sodium compounds Peripherally selective drugs Technetium-99m