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Determination of radiochemical purity of radiopharmaceuticals TechneScan HDP by chromatography using different mobile and stationary phases
RAUS, Klára
Nuclear medicine is a relatively young medical field. The nuclear medicine department performs both diagnostic tests and therapies using open radiation sources whereas the diagnostic use currently prevails. The imaging method used is called scintigraphy and uses a scintillation camera capturing the distribution of administered radiopharmaceutical. Using a scintillation detector, which is incorporated in a gamma camera, the distribution of the radiopharmaceutical in the target tissue can be observed, either after a certain period of time from the administration of the radiopharmaceutical (static scintigraphy) or over time (dynamic scintigraphy). One of the most common examinations performed at the nuclear medicine department is bone scintigraphy. The examination is carried out using osteotropic radiopharmaceutical that binds to bones, thus revealing pathologies caused by the change of metabolic activity. The examination in itself takes place through external detection of the administered radiopharmaceutical. Bone scintigraphy is a very useful examination that is used to detect bone metastases in cancer diseases, to diagnose primary malignant bone tumors, to detect infectious processes in the bones, to diagnose joint diseases, metabolic diseases of the skeleton, and bone injuries. The examination in itself is performed by using radiopharmaceuticals. Once administered, the radiopharmaceutical serves as a diagnostic indicator. This is a medicine that incorporates a radionuclide that emits ionizing radiation. The radionuclides used in nuclear medicine are artificially prepared and transported either as ready-to-use products or as radionuclide generators to the nuclear medicine department. The generator that is the most commonly used at the nuclear medicine department is the 99Mo/99mTc generator. The above mentioned radionuclide generator consists of a glass chromatography column which is located in a lead shielding cylinder. The column contains the adsorbent material (alumina) in which the parent radionuclide is adsorbed. Due to different chemical properties of the parent and the daughter element the daughter radionuclide can be washed out (eluted) by means of a suitable solution. In practice, the radiopharmaceuticals are commonly prepared using kits that are commercially available. The kits are labeled by using sodium pertechnetate solution obtained from the 99Mo/99mTc generator. Prior to the administration of the radiopharmaceutical to the patient it is necessary to carry out the determination of radiochemical purity. The most commonly used is a paper chromatography and thin layer chromatography. In the Czech Republic, 99mTc labelled diphosphonates (e.g. the kits TechneScan HDP, 6-MDP or 8-MDP are used for bone scintigraphy. These osteotropic radiopharmaceuticals are prepared in a shielded laminar box in the radiopharmaceutical laboratory at the nuclear medicine department. The preparation is subject to the manufacturer's instructions. After preparation, prior to administration to the patient, the determination of radiochemical purity needs to be performed. The determination of radiochemical purity of the radiopharmaceutical TechneScan HDP is carried out by using thin layer chromatography (ITLC-SG) by means of 13.6% solution of sodium acetate and methyl ethyl ketone as eluent. However, this determination is demanding for the normal operation of the department in terms of design as well as costs. Therefore, a suitable alternative method was sought. The new method consists in paper chromatography by using 0.9% solution of sodium chloride and acetone as eluent. After 50 determinations of radiochemical purity using pharmacopoeial and alternative methods was found that the alternative method is applicable for the routine determination of radiochemical purity during normal operation of the nuclear medicine department
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