Effective dose estimation and risk assessment in patients treated with iodine 131I using Monte Carlo simulation

Abstract

<p>The most frequently used radiopharmaceutical for treatment of thyroid diseases such as Thyroid Cancer and Hyperthyroidism is radioactive iodine 131I. It has a very high success rate in treatment of patients with thyroid diseases and also it has been proven to be safe and relatively inexpensive treatment modality. Whenever radiation is used in the treatment of the benign or cancer diseases dosimetry is essential. The main aim of this study is to perform external measurements of dose rate after administered activity and to simulate dosimetry of internal organs and risk assessment using MCNP 4b code, either for thyroid cancer and Hyperthyroid patients. To search safety optimization in this kind of therapy, it was recognized the necessity of more accurate knowledge of dose levels received by stomach and other organs. Of great importance is to know the effective dose that will be reached in gastric and other surrounding organs such as liver, lung, bladder etc. Additional aim was to provide information to be used in the improvement of radiation therapy, radiation safety practices and improvement of the fundamentals of radiation protection as defined by ICRP: justification, optimization and application of dose limits. The significance of this research is that the doses to internal organs can be determined and it worth to mention that such internal dosimetry calculation has been performed&nbsp;&nbsp; rare in the field of nuclear medicine. In accordance with the calculations carried out during this study and reference available in the literature that the therapy with radioiodine will be improved at the Institute of pathophysiology and nuclear medicine. Designed quality programs will be useful also for regulatory and accreditation bodies in the process of accreditation and radiation protection strategy. This work is divided into interconnected chapters. Chapter 2 to 4 contains the literature review and theoretical background of the study. Chapter 3 covers material and methods and aspect of Monte Carlo transport code focused on MCNP 4b code. Chapter 4 provides the results and discussion of the findings. Conclusions and recommendations are discussed in Chapter 5. Chapter 6 contains references used in this work.</p>

<p>Cilj terapije sa radiaoktivnim jodom 131I kod pacijenata koji boluju od nekih tipova tiroidnih carcinoma i hipertiroidizma je isporuka doze i apsorpcija doze u tiroidnoj žlezdi. Terapija sa radioaktivnim jodom sprovodi se u obliku rastvora Na131I (natrijum jodida) u tečnoj formi ili aplicira se u formi kapsule. Efektivna doza je rezultat apsorbovane doze u tiroidnom tkivu, ali i ostali unutra&scaron;nji organi prime izvesnu dozu. Kapsule koje sadrže natrijum jodid ostaju u stomaku oko 15 minuta pre nego &scaron;to započne apsorpcija, vreme dovoljno dugo za rizično izlaganje. Ova činjenica je jedan od ciljeva doktorske teze, odrediti efektivnu dozu u stomaku i nekoliko unutra&scaron;njih okolnih organa modelovanje transporta i interakcije gama zračenja i beta čestica emitovanih iz radionuklida 131I je kori&scaron;ćen Monte Karlo kod (MCNP4b). Radiojod je modelovan kao tačkasti izvor na dnu stomaka. Proračunavana je apsorbovana energija po jedinici transformacije u stomaku i okolnim organima. Ekvivalentna doza u tim organima je izračunata da bi se odredila efektivna doza primenom odgovarajućih težinskih faktora. Dobijeni rezultati imaju značaja za za&scaron;titu od zračenja, ali su važni i za ustanovljavanje novih kalibracionih procedura kao deo sigurnosne kontrole i kontrole kvaliteta u proizvodnji i kontroli radiofarmaceutika kao i procedure administriranja radiofarmaceutika i primene bolnčikih puteva. Smatramo da če rezultati ovog istraživanja pobolj&scaron;ati bezbednosnu kulturu u na&scaron;em sistemu zdravstvene za&scaron;tite kao i u državnim organima koji kreiraju i donose regulative.</p>