Production and Use of 99mtc in Nuclear Medicine in Australia – Radiology Example

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"Production and Use of 99mtc in Nuclear Medicine in Australia" is a decent example of a paper on radiology. Technetium-99m (TC-99m) is a radioactive tracer isotope with gamma-ray energy of approximately 140 keV and is utilized widely in Nuclear Medicine. The gamma-ray energy makes TC-99m suitable for detection. Besides that, TC-99m biological half-life and physical half-life, and this enable to clear very fast from the body after the process of imaging. More importantly, the gamma is not supplemented by beta emission; therefore, it is a single energy, which allows for more precision in aligning the imaging detectors.

  Basically, the production of 99mTc happens through the bombardment of molybdenum 98Mo together with neutrons. The resulting 99Mo goes through a process of decaying with a half-life of approximately 66 hours to a Tc metastable state. The process facilitates the production of 99mTc for nuclear medicine. Moreover, 99mTc can be produced from 99Mo; in this case, 99mTc is utilized in the form of Pertechnetate. Production of Parent Radionuclide As mentioned earlier, the production of 99mTc is achieved by bombarding 98Mo with neutrons so as to produce 99MO, and Technetium is achieved after 99MO  undergoes  Beta decay (Bryan, 2009).

Akin to all other Technetium isotopes, 99mTc is not stable and normally ends up as Ruthenium-99 after Beta decay. The first discovery of 99mTc was in 1938 as the molybdenum cyclotron bombardment product, wherein a radionuclide known as Molybdenum-99 was produced after 2.75 days then decayed to Technetium-99m.   According to Srivastava and Mausner (2014) radionuclides may be grouped into two; those which are neutron- deficient and neutron-rich. Therefore, radionuclides that are neutron-deficient are normally produced through the bombardment of the target with helium particles, deuterons, or protons while those that are neutron-rich are produced in a nuclear reactor.

Furthermore, radionuclides (radioactive nuclides) are produced artificially by converting the stable nuclide into state instability through bombarding nuclear particles primarily alphas, protons, neutrons, gammas, deuterons, or other nuclear particles. Physical Characteristics Beta-decay is typified by converting neutron to a proton within the nucleus then followed later by electron emission. This electron’ s maximum energy known as the beta particle is similar to the variance in the rest masses of the final as well as initial atoms.

However, in the majority of the emissions, a percentage of the existing energy is taken away by a neutrino with the objective of ensuring that the actual beta energy is below the maximum. As mentioned by Troutner (1987), the beta emitters are typified by the unceasing spectrum of energy that ranges from zero to the maximum. In this case, the average energy is close to 30% of the maximum energy. Pertechnetate Tc-99m pertechnetate  is one of the  Tc-99m radiopharmaceuticals  utilized in renal imaging as well as thyroid function’ s clinical imaging. Franken et al.

(2010) posit that this gamma emitter is conveyed by the sodium iodide symporter; however, it is not included in the thyroglobulin. Tc-99m pertechnetate  is considered to be a powerful tool for studying the activity of the sodium iodide symporter in different parts of the organs.   Some of the Tc-99m pertechnetate  characteristics include six hours biological half-life, photon energy of 140 keV, physical half-life, and normal distribution in the salivary glands, thyroid, and stomach. The equation below shows how pertechnetate normally reduces to Tc4+ and the stannous ion (Sn2+) is transformed into a stannic ion (Sn4+). As shown in the equation, the oxidizing agent is pertechnetate while the reducing agent is the stannous ion.

The Tc4+ is considered to be the most suitable chemical form for reacting with an anion such as DTPA, MDP, or PYP. TC4+ when added to pyrophosphate4 forms Tc-pyrophosphate How 99mtc-Pertechnetate is used to Create Other Radiopharmaceuticals Ponto (1998) posits that the majority of the 99mTc radiopharmaceutical products are created by 99mTc-pertechnetate, which contains excessive 99Tc amounts of as well as oxidizing impurities for preparing products that relatively have small stannous amounts. Tc-99m pertechnetate is beneficial for synthesizing different radiopharmaceuticals for the reason that Tc may adopt numerous oxidation states.

In view of this, radiopharmaceutical specificity is dictated by ligands and oxidation state. The desired radiopharmaceutical synthesis from 99mTc radiopharmaceutical, which is the reducing agent, as well as the sought-after ligands must happen in one container following elution; then, the reaction has to be carried out in the solvent which could be intravenously injected like the saline solution. Other radiopharmaceuticals Other radiopharmaceuticals such as Cr-51 RBCs could be prepared by incubating anticoagulated whole blood (20 to30 ml) together with sodium chromate (50 to 100 μ Ci).

In this case, the anticoagulation of the blood normally happens with ACD or heparin solution. Incubation should take place for 15 minutes, and termination of the reaction takes place by adding a small quantity of ascorbic acid that transforms an unreacted chromate ion into a chromous ion. The objective of this is to prevent cell labeling from going on following the injection of the material into the patient. The Sodium Chromate binds irreversibly as well as avidly to the hemoglobin molecule’ s beta-globin chains; thus, creating labeled cells with exceptional in vivo stability.

The RBC's labeling using Tc-99m as well involves the radioisotope binding to the b hemoglobin molecule’ s beta-globin chains. In this regard, the cells could be labeled in vitro or in vivo through various procedures. Use in Nuclear Medicine Including Clinical Indications for Scans As evidenced in Gandhi, Babu, Subramanyam, and Sundaram's (2013) study, Tc-99m macro aggregated albumin (MAA) is one and the same for lung perfusion scintigraphy; more importantly, it is the part of the pulmonary thromboembolism evaluation study.   As mentioned by Gandhi, Babu, Subramanyam, and Sundaram (2013), Tc-99m MAA is an extremely important radiopharmaceutical that may be utilized for scores of other clinical indications in addition to the normally utilized indication in pulmonary embolism for lung perfusion scan.

For instance, Tc-99m MAA may be utilized for calculating FEV1  when planning for lung surgery,   can also be used in selective internal radiation therapy (SIRT) planning, hepatopulmonary syndrome (HPS), pulmonary artery, and so forth.   99mTc‐DTPA is utilized as a kidney imaging agent. Tc-99m has been utilized for medical imaging in over 90 percent of cases all across the globe because of its ideal nuclear characteristics.

A parathyroid scan can be carried out through the injection of dual radioisotopes; in this case, the radioisotope commonly utilized is the TI-201 tracers as well as Tc99 pertechnetate. The present imaging agents’ designs are rooted in selecting the suitable biomolecules to function carefully as the actual vectors in Tc‐99m vivo delivery to certain biological targets like the transporters as well as receptors. Tc99 can be evidenced in some of the figures below. Figure one shows a stenting scan of the Pre-left pulmonary artery.

The figure shows a Tc-99m MAA tracer distribution is significantly reduced in the left segments of the bronchopulmonary as observed in Gandhi, Babu, Subramanyam, and Sundaram's (2013) study. Conclusion In conclusion, nuclear medicine as evidenced in this report utilizes radiation so as to offer diagnostic information concerning specific organs’ functionality or may be utilized to treat them. These days, the use of radioisotopes for diagnostic procedures has become routine. Tc-99m is these days utilized to treat a number of medical conditions such as cancer, whereby the targeted cells are destroyed or weakened through radiation.

References

Bryan, N. (2009). Introduction to the Science of Medical Imaging. Cambridge, United Kingdom: Cambridge University Press.

Franken, P., Guglielmi, J., Vanhove, C., Koulibaly, M., Defrise, M., Darcourt, J., & Pourcher, T. (2010). Distribution and dynamics of (99m)Tc-pertechnetate uptake in the thyroid and other organs assessed by single-photon emission computed tomography in living mice. Thyroid, 20(5), 519-526.

Gandhi, S. J., Babu, S., Subramanyam, P., & Sundaram, P. S. (2013). Tc-99m macro aggregated albumin scintigraphy – indications other than pulmonary embolism: A pictorial essay. Indian Journal of Nuclear Medicine, 28(3), 152–162.

Ponto, J. A. (1998). Technetium-99m Radiopharmaceutical Preparation Problems: 12 Years of Experience. Journal of Nuclear Medicine Technology, 26(4), 262-264.

Srivastava, S. C., & Mausner, L. F. (2014). Therapeutic Radionuclides: Production, Physical Characteristics, and Applications. In R. P. Baum, Therapeutic Nuclear Medicine (pp. 11-50).

Troutner, D. E. (1987). Chemical and physical properties of radionuclides. Nuclear Medicine and Biology, 14(3), 171-176.

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