| Περίληψη: | The present thesis, entitled “Application development for personalized dosimetry in pediatric examinations of Nuclear Medicine based on Monte Carlo simulations and the use of computational models”, aims to develop and certify innovative personalized dosimetry tools in pediatric nuclear medicine examinations (SPECT, PET, multimodal SPECT/PET/CT), as well as to optimize therapeutic approaches, using Monte Carlo simulations with high resolution computational anthropomorphic phantoms, enriched with personalized anatomical information of each patient.
First, an extensive literature research was performed for the dosimetry applications in preclinical and clinical pediatric medical procedures in Chapter 2. The literature investigation is continued in Chapter 3 with the most indicative applications of: 1) Monte Carlo simulations for estimation of pediatric dosimetry, 2) small animal computational phantoms, 3) pediatric computational phantoms, extensively used for medical applications, and 4) Machine Learning techniques that are used for the assessment of individualized absorbed doses.
As the use of radiopharmaceuticals in imaging and therapy is increasing, it becomes important to achieve a higher level of accuracy in internal dosimetry on small animal studies as well. In Chapter 4, first we validated our tools and methods by performing dosimetric calculations to create a small-animal database for nuclear medicine. Commonly used radiopharmaceuticals were examined / studied to define the absorbed dose rates for several organs of interest in preclinical studies. Furthermore, we extended the dosimetric calculations for common PET and SPECT exams, to specify the impact on the absorbed dose calculation by the size of each different organ.
Then clinical applications in pediatric nuclear medicine were studied. We used the previous described methods for calculating the absorbed dose per organ that takes into account the specific anatomy of each patient and calculates the “Specific Absorbed Dose Rates” (SADRs) for each organ, according to the specified biodistribution of each radiopharmaceutical.
Moreover, as the Computed Τomography (CT) scanners have now been integrated into multi-modality PET/CT and SPECT/CT devices, their impact on radiation exposure, especially in pediatric applications has dramatically increased. In order to quantify this impact, dosimetry simulations and calculations were performed, including updated pediatric protocols of head, chest and abdomen/pelvis exams. When anatomical difference is observed, the difference in the absorbed dose per organ for each body type is reported.
The goal of this Ph.D. thesis was a) to create a dosimetry database that contains simulated pediatric data produced by Nuclear Medicine and CT acquisitions, and b) to match any new pediatric patient to the “best” fitted anatomical model of the database according to the characteristics of its internal organs. This method results to a more accurate organ dose assessment.
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