Internal occupational dosimetry for the occupational worker exposed to [18F] FDG from the Cyclotron-PET/CT Laboratory of the Universidad de Costa Rica / Dosimetría ocupacional interna para el personal trabajador expuesto a [18F] FDG del ciclotrón-PET/CT en el Laboratorio de la Universidad de Costa Rica

ABSTRACT: The aim of this work is to provide a methodology for evaluating the committed effective dose E(50) due to the incorporation of [18F] FDG in the occupationally exposed worker (OEW) of the Cyclotron-PET/CT Laboratory of the Centro de Investigación en Ciencias Atómicas, Nucleares y Moleculares (CICANUM) at Universidad de Costa Rica using in vivo measurements. The measurement system was calibrated to perform in vivo measurements and defined as the corresponding bioassay function for the radiopharmaceutical used. The conversion factor was assessed with a known activity of 18F in the geometry and measurement time established. Among the most relevant results, the measurement parameters and the calibration procedure were defined. A value of 1.73 x 103 Bq/cps for in vivo brain measurements was obtained as a conversion factor. This study provides a methodology, to evaluate the committed effective dose due to the incorporation of 18F-FDG in a radionuclide production and diagnostic center

Production, quality control, biodistribution assessment and preliminary dose evaluation of [177Lu]-tetra phenyl porphyrin complex as a possible therapeutic agent / Produção, controle de qualidade, avaliação de biodistribuição e avaliação da dose preliminar de [177Lu] -tetra complexo fenil porfirina como um possível agente terapêutico

Due to interesting therapeutic properties of ¹⁷⁷Lu and tumor avidity of tetraphenyl porphyrins (TPPs), ¹⁷⁷Lu-tetraphenyl porphyrin was developed as a possible therapeutic compound. ¹⁷⁷Lu of 2.6-3 GBq/mg specific activity was obtained by irradiation of natural Lu₂O₃sample with thermal neutron flux of 4 × 10¹³ n.cm^-2.s^-1. Tetraphenyl porphyrin was synthetized and labeled with ¹⁷⁷Lu. Radiochemical purity of the complex was studied using Instant thin layer chromatography (ITLC) method. Stability of the complex was checked in final formulation and human serum for 48 h. The biodistribution of the labeled compound in vital organs of wild-type rats was studied up to 7 d. The absorbed dose of each human organ was calculated by medical internal radiation dose (MIRD) method. A detailed comparative pharmacokinetic study was performed for ¹⁷⁷Lu cation and [¹⁷⁷Lu]-TPP. The complex was prepared with a radiochemical purity: >97±1% and specific activity: 970-1000 MBq/mmol. Biodistribution data and dosimetric results showed that all tissues receive approximately an insignificant absorbed dose due to rapid excretion of the complex through the urinary tract. [¹⁷⁷Lu]-TPP can be an interesting tumor targeting agent due to low liver uptake and very low absorbed dose of approximately 0.036 to the total body of human...

Devido às propriedades interessantes do ¹⁷⁷Lu e da avidez tumoral das tetrafenil porfirinas (TPP), desenvolveu-se a ¹⁷⁷Lu-tetrafenil porfirina como composto terapêutico potencial. ¹⁷⁷Lu de atividade específica de 2,6-3 GBq/mg foi obtido por irradiação de amostra de Lu₂O₃ com fluxo térmico de nêutrons de 4 × 10¹³ n.cm^-2.s^-1. Sintetizou-se a tetrafenil porfirina e marcou-se com ¹⁷⁷Lu. A pureza radioquímica do complexo foi estudada usando método de Cromatografia Instantânea de Camada Delgada ( ITLC). A estabilidade do complexo foi checada na formulação final e no ser humano por 48 h. A biodistribuição do composto marcado em órgãos vitais de ratos do tipo selvagem foi estudada por mais de 7 dias. A dose absorvida para cada órgão humano foi calculada pelo método da Dose Médica de Radiação Interna (MIRD). Estudo farmacocinético comparativo detalhado foi efetuado para o cátion ¹⁷⁷Lu e para o [¹⁷⁷Lu]-TPP. O complexo foi preparado com pureza radioquímica >97±1% e atividade específica de 970-1000 MBq/mmol. Os dados de biodistribuição e os resultados dosimétricos mostraram que todos os tecidos receberam uma dose absorvida aproximadamente insignificante devido à rápida excreção do complexo pelo trato urinário. O [¹⁷⁷Lu]-TPP pode ser um agente interessante de direcionamento do tumor devido à baixa captação pelo fígado e pela dose bem baixa absorvida, de, aproximadamente, 0,036 do corpo humano total...

Are Medical Personnel Safe from Radiation Exposure from Patient Receiving Radioiodine Ablation Therapy? / 핵의학분자영상

Radioiodine ablation therapy has been considered to be a standard treatment for patient with differentiated thyroid cancer after total thyroidectomy. Patients may need to be hospitalized to reduce radiation exposure of other people and relatives from radioactive patients receiving radioiodine therapy. Medical staffs, nursing staffs and technologists sometimes hesitate to contact patients in radioiodine therapy ward. The purpose of this paper is to introduce radiation dosimetry, estimate radiation dose from patients and emphasize the safety of radiation exposure from patients treated with high dose radioiodine in therapy ward. The major component of radiation dose from patient is external exposure. However external radiation dose from these patients treated with typical therapeutic dose of 4 to 8 GBq have a very low risk of cancer induction compared with other various risks occurring in daily life. The typical annual radiation dose without shielding received by patient is estimated to be 5 to 10 mSv, which is comparable with 100 to 200 times effective dose received by chest PA examination. Therefore, when we should keep in mind the general principle of radiation protection, the risks of radiation exposure from patients are low and the medical personnel are considered to be safe from radiation exposure.

Dosimetria em folículos tireoidianos devido aos elétrons de baixa energia do iodo usando o método Monte Carlo / Dosimetry in thyroid follicles due to low-energy electrons of iodine using the Monte Carlo method", "_i": "en

OBJETIVO: Avaliar a dose absorvida em folículos tireoidianos devido aos elétrons de baixa energia, como oselétrons Auger e os de conversão interna, além das partículas beta, para os radioisótopos de iodo (131I, 132I,133I, 134I e 135I) usando o método Monte Carlo. MATERIAIS E MÉTODOS: O cálculo da dose foi feito ao nível folicular, simulando elétrons Auger, conversão interna e partículas beta, com o código MCNP4C. Os folículos (colóide e células foliculares) foram modelados como esferas, com diâmetros do colóide variando de 30 a 500 μm. A densidade considerada para os folículos foi a da água (1,0 g.cmû³). RESULTADOS: Considerando partículas de baixa energia, o percentual de contribuição do 131I na dose total absorvida pelo colóide é de aproximadamente 25%, enquanto os isótopos de meia-vida física curta apresentaram contribuição de 75%. Para as células foliculares, esse percentual é ainda maior, chegando a 87% para os iodos de meia-vida curtae 13% para o 131I. CONCLUSÃO: Com base nos resultados obtidos, pode-se mostrar a importância de se considerar partículas de baixa energia na contribuição para a dose total absorvida ao nível folicular (colóide e células foliculares) devido aos radioisótopos de iodo (131I, 132I, 133I, 134I e 135I).

OBJECTIVE: To evaluate the absorbed dose in thyroid follicles due to low-energy electrons such as Auger and internal conversion electrons, besides beta particles, for iodine radioisotopes (131I, 132I, 133I, 134I and 135I)utilizing the Monte Carlo method. MATERIALS AND METHODS: The dose calculation was performed at follicularlevel, simulating Auger, internal conversion electrons and beta particles, with the MCNP4C code. The follicles(colloid and follicular cells) were modeled as spheres with colloid diameter ranging from 30 to 500 μm, and with the same density of water (1.0 g.cmû³). RESULTS: Considering low-energy particles, the contributionof 131I for total absorbed dose to the colloid is about 25%, while the contribution due to short-lived isotopesis 75%. For follicular cells, this contribution is still higher achieving 87% due to short-lived iodine and 13%due to 131I. CONCLUSION: The results of the present study demonstrate the importance of considering lowenergyparticles in the contribution for the total absorbed dose at follicular level (colloid and follicular cells) due to iodine radioisotopes (131I, 132I, 133I, 134I and 135I).