Sodium (Tc-99m) Pertechnetate PDF

Sodium (Tc-99m) Pertechnetate FS SABAYA Nomenclature Sodium (Tc-99m) Pertechnetate CHEMICAL FORMULA AND STRUCTURE Chemical element with atomic # 43 in a periodic table Transition metal in group VIIA with Mn, Tc and Re Formula: Na99mTcO4 Structure: contains the pertechnetate anion,...

Sodium (Tc-99m) Pertechnetate FS SABAYA Nomenclature Sodium (Tc-99m) Pertechnetate CHEMICAL FORMULA AND STRUCTURE Chemical element with atomic # 43 in a periodic table Transition metal in group VIIA with Mn, Tc and Re Formula: Na99mTcO4 Structure: contains the pertechnetate anion, TcO4- Anion Description: TcO4- is a large monovalent oxyanion where technetium (Tc) is in the highest oxidation state of +7. CHEMISTRY CONT.… Oxidation # of Tc in TcO4- is +7 Most stable oxidation states are +7 (as pertechnetate ) and +4 (in absence of chelating agents e.g. TcO2) Other oxidation states often found in presence of chelating agents -Most commonly +5, +3 and +1 99mTc(VII): -Is readily reduced by reducing agents (most commonly Sncl2.2 H2O (stannous chloride dihydrate) CHEMISTRY CONT.… - Is readily bound by chelating agents in reduced states - Forms basis of many other radiopharmaceuticals 99mTcO4- is hydrophilic/ lipophobic Electron Configuration of Tc (Z = 43): [Kr]4d55s2 Molecular weight of the TcO4- anions is approximately 163 Daltons (The full molecular weight of Sodium Pertechnetate (NaTcO₄) is slightly higher, accounting for the sodium cation) Classified as simple salt PREPARATION Na99mTcO4 is eluted from 99Mo/99mTc generator using 0.9% (normal) saline as eluent Sterile, non-pyrogenic, physiologically compatible solution Concentration ~ 10-9M 99mTcO4- PHYSICAL CHARACTERISTICS 99mTc decays to 99Tc via a process called Isomeric transition Definition: 99mTc is a metastable nuclear isomer of technetium-99. The "m" in 99mTc stands for "metastable," meaning it is in an excited energy state compared to its stable isotope, 99Tc. Decay Process: 99mTc undergoes isomeric transition to reach a lower, more stable energy state, transforming into 99Tc. During this transition, it releases energy in the form of gamma radiation (140 keV photon), which is detectable and useful for medical imaging. Half-Life: The half-life of 99mTc is approximately 6.02 hours, meaning after 6 hours, half of the initial 99mTc will have decayed to 99Tc. Technetium-99 (99Tc ): A Long-Lived Decay Product Decay of 99Tc: Once 99mTc undergoes isomeric transition, it becomes 99Tc, which is a different form of technetium with a very long half-life of about 2.12 x 105 years (212,000 years). Decay Mode: 99Tc decays by beta emission rather than gamma emission, releasing a low-energy beta particle (electron) and transforming into a more stable element, Ruthenium-99 ( 99Ru). i.e 99mTc---6.02h-------99Tc --------2.12 x 105 years------99Ru T1/2 99mTc = 6.02 h, 99Mo = 67 h (2.8 days) Primary radiation; γ at energy of 140 KeV Silver-gray metal Not soluble in hydrochloric acid QUALITY CONTROL Visual inspection -Eluate should be clear, colorless and free from visible, foreign, particulate matter QC CONT.. Radiochemical purity (RP) = or > 95% 99mTcO4- using ITLC-SG/saline 99Mo content < 0.15 kBq 99Mo per 1.0 MBq 99mTc at time of administration Al3+ content < 10μg/ml (Calorimetric test) QC CONT.… pH (4.5 to 7.5) Radionuclidic Purity Less than HPB limits at time of administration Expiry 8 to 18 hours after elution Others Sterility and pyrogenicity should be retrospectively checked PHARMACOKINETICS Routes of administration Primary intravenous May also be oral, -Pertechnetate ion rapidly diffuses from gastrointestinal tract into circulatory system - Diffusion based on concentration gradient BIODISTRIBUTION Tissue and blood distribution Binding to plasma protein Rapidly equilibrates with extracellular space Equilibrates with red blood cells Excreted to the kidneys BIODISTRIBUTION CONT.… Localizes in; Thyroid gland (Active transport into follicular cells) Gastric mucosa (Actively concentrated by mucoid cells) Salivary glands (Actively concentrated by salivary gland ductal epithelial cells) BIODISTRIBUTION CONT.… Choroid plexus Mucous membrane Sweat glands Brain lesions (simple diffusion across compromised BBB) ELIMINATION FROM THE BODY Excreted via; Kidneys (Urine) Intestines (faeces)