The surgical viability and radiological monitoring of brain implants of bioactive micro-seeds in an animal model

Abstract

The interstitial implant is a therapeutic modality in brachytherapy of the head and neck. Presently, the seeds implanted in tumors in the central nervous system are metallic I-125. After the full emission of the radionuclide, the seed remains inert in the implanted area. Bioactive ceramic seeds have been prepared for this research group incorporating Sm-152 to be active in Sm-153. The main goal of the present study is the development of a the surgical technique for implanting the biodegradable radioactive micro-seeds in the brains of rabbits, as well as the observation of the clinical reactions of the animal after implantation of two sets of three seeds. The surgical procedure consisted of performing two separate perforations 10 mm from each other in the skull, permitting the implantation of two groups of three seeds, totaling six seeds. The results of the pilot study showed the effectiveness of the surgical procedure and of the biocompatibility of the seeds and the lack of presence of adverse reactions, functional sequels, or inflammation in a follow up 50 days post-surgery. Such seeds of reduced volume, 0.2 x 1.6 mm, could be monitored by computerized tomography 30 days after implanting.<br>Os implantes intersticiais podem ser utilizados em braquiterapia de cabeça e pescoço. Atualmente as sementes implantadas no CNS são de I-125 metálicas. Após o decaimento do radioisótopo, a semente fica inerte na região implantada. Sementes cerâmicas bioativas tem sido preparadas pelo grupo de pesquisa incorporando Sm-152. O presente estudo tem o objetivo de viabilizar a técnica cirúrgica de implantes de microsementes biodegradáveis não radioativas no cérebro de coelhos, bem como verificar as reações clínicas e funcionais do animal ao corpo estranho implantado. O procedimento cirúrgico compreendeu em proceder duas perfurações separadas em 10mm na calota craniana onde foi possível a implantação de dois conjuntos de três sementes, totalizando seis sementes. Os resultados do estudo piloto evidenciam a eficácia do procedimento cirúrgico e do material implantado, já que não foram encontradas reações adversas, seqüelas funcionais, ou resposta inflamatória durante 30 dias pós-cirurgia. Tais sementes de reduzido volume, 0.2x1.6mm, puderam ser monitoradas por tomografia computadorizada

Monte Carlo calculated TG‐60 dosimetry parameters for the emitter brachytherapy source

“…The specific activity of the produced 153 Sm is 750 mCi/mg. 8 In the previously published investigations, preliminary studies for the implant of biodegradable radioactive 153 Sm seeds in the liver, 4 brain, 9,10 and prostate 11 have been prepared. Several factors must be considered for radionuclide selection.…”

Characterization of ceramic seeds with samarium-153 for use in brachytherapy

“…where m is the mass of the element to be irradiated in grams, the factor Θ is isotopic abundance of target nucleus, A is the atomic mass of the element, N A is the Avogadro's number, Φ th is the thermal neutron flux, Φ epi is epithermal neutron flux, σ γ is the neutron capture cross section of the target nucleus in cm 2 , I γ is the resonance integral for the epithermal neutron flux of the target nucleus in cm 2 , λ is the decay constant of the produced radionuclide, t is the time of irradiation in seconds and d is the time to decay after irradiation in seconds. Another set of seeds was immersed in 15 mL vials fi lled with SBF (simulated body fl uid) and left for 20 days to verify its solubility in such fl uid.…”

Monte Carlo characterization of biocompatible beta‐emitting glass seed incorporated with the radionuclide as a SPECT marker for brachytherapy applications

“…Preliminary studies for the implant of biodegradable radioactive seeds in the liver and brain have been previously published. ( 13 , 14 , 15 ) Other investigators synthesized two sets of ceramic seeds by the sol‐gel technique with Si‐Ca‐Sm and Si‐Ca‐Ho incorporating natural samarium and holmium elements for use in brachytherapy. ( 16 , 17 , 18 , 19 )…”