Dosimetric evaluation of hot-lab procedures during the preparation of radiopharmaceuticals
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Date
2024-06-26
Authors
Ντίνος, Ευθύμιος
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Abstract
This dissertation delves into the intricate realm of Nuclear Medicine Physics, aiming to unravel its fundamental principles and their practical implications. Beginning with an exploration of Nuclear Physics basics, the study emphasizes the indispensable nature of understanding nuclear structure and radioactivity for comprehending subsequent top ics. Through a narrative on dosimetry, the thesis underscores the critical role of accurately calculating energy deposition and absorbed dose to ensure patient safety and treatment efficacy in medical settings employing ionizing radiation. Central to Nuclear Medicine is the nuanced selection of radioisotopes, discussed in the context of their energy characteristics and half-life, which significantly influence diagnostic and therapeutic outcomes. The methods of radioisotope production, including cyclotrons, nuclear reactors, and radionuclide generators, are examined, shedding light on their applications and limitations within the field. Furthermore, the study engages in a discourse on radiopharmaceuticals, elucidating their pivotal role in diagnostic and therapeutic procedures. Highlighting the properties and applications of Technetium-99m and Yttrium-90, the discussion unveils the intricate interplay between radioisotope properties, production methods, and clinical utility.
The Nuclear Medicine department layout in hospitals, particularly the Hot Lab, plays a crucial role in the safety of patients and staff. It's important to classify areas within the department based on radiation exposure levels, as outlined by organizations like the Greek Atomic Energy Committee. Within the department, various areas are designated as controlled or supervised depending on the procedures performed. The Hot Lab, where radiopharmaceuticals are synthesized and handled, is a controlled area with strict access policies. Other areas, like patient waiting rooms and staff offices, are supervised. The Hot Lab is equipped with specialized tools such as fume hoods and dose calibrators to ensure safe handling of radioactive materials. Its design includes features like foot-operated sinks and shielded crypts for radiation protection.
Monte Carlo simulations are valuable for dosimetric studies in Nuclear Medicine. Tools like Geant4 and GATE facilitate simulations, allowing researchers to study radiation interactions with matter and optimize procedures. The basic steps of a Monte Carlo simulation involve defining the geometry of the system, specifying physical pro cesses, implementing tools for interaction (actors), initializing the simulation, defining radiation sources, and executing the simulation. Afterward, researchers analyze the simulation results to draw conclusions about radiation exposure and safety. In this experiment focused on dosimetry within the Hot Lab, the synthesis of 99mTc-based radiopharmaceuticals is studied in four steps. This includes generator elution, solution extraction, mixing the solution with the pharmacological substance, and patient dose extraction. Monte Carlo simulations help unravel dosimetric intricacies in these processes.
In analyzing the absorbed dose values throughout each step of the study, several key observations emerge. The highest doses are received during the first step, gradually decreasing in subsequent steps due to lower source activity. The thyroid gland in many instances absorbed higher doses, highlighting its radiation sensitivity. Annual dose estimates remained within safety limits, with the lens of the eye being the most radiosensitive. Tungsten, denser than lead, proves more effective in shielding aggainst gamma rays, but its density poses challenges in shield design. With the disclosure of the results, the importance of protocol adherence is emphasized, given potential cumulative exposures from multiple daily processes. Considering potential malpractices, neglecting tungsten shields in specific steps significantly increases absorbed doses. Study of such lapses further underscores the necessity of proper shielding protocols to mitigate unnecessary exposures. Looking ahead, refining simulations using Python offers efficiency improvements. Additionally, future studies may explore extremity dose estima tions and simulate diverse processes or theoretical scenarios to better understand radiation exposure risks. Continuous vigilance and adherence to ALARA principle remain paramount in minimizing occupational radiation risks in Nuclear Medicine settings.
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Keywords
Dosimetry, Hot-lab, Monte Carlo simulations, Radiopharmaceuticals