Programmatic Assessment of Potential Induced Radioactivity in Electron Beam Sterilization of Healthcare Products.

ISO 11137-1:2006 Sterilization of Healthcare Products-Radiation requires that the potential for induced radioactivity be evaluated for medical devices irradiated with electrons with energy more than 10 MeV. For a manufacturing operation where new devices are being developed, a practical program for making such an evaluation should be engrained in the process, including the device design phase, where selection of materials can make a difference in the potential for activation to occur as a result of the irradiation process. The program, which is based on general assumptions as to the likely activation processes and generalized process assessments is being implemented in three phases: (1) incorporating materials consideration in the design phase, (2) evaluating potential activation empirically, including measurement at the point of irradiation, and (3) implementing routine procedures for the program, including developing a data base of results for consideration in future design efforts.

A solid target system with remote handling of irradiated targets for PET cyclotrons.

A solid target system was developed for a PET cyclotron. The system is compatible with many different target materials in the form of foils and electroplated/sputtered targets which makes it useful for production of a wide variety of different PET radionuclides. The target material is manually loaded into the system. Remote handling of irradiated target material is managed with a pneumatic piston and a vacuum technique which allows the targets to be dropped into a shielded transport container. To test the target performance, proton irradiations (12.8 MeV, 45 µA) of monoisotopic yttrium foils (0.64 mm, direct water cooling) were performed to produce 89Zr. The yields were 2200±200 MBq (1 h, n=13) and 6300±65 MBq (3 h, n=3).

Determination of alpha activity in solid samples by leaching or digestion.

The analysis of solid environmental samples by α-particle spectrometry generally involves processes requiring an initial treatment to destroy the complexes in the matrix, and dissolve the radionuclides of interest. This study compared the activities obtained for several natural radionuclides ((238)U, (234)U, (230)Th, (226)Ra, and (210)Po) in previously well-characterized materials, using two procedures: acid leaching and digestion in a microwave oven. The measured activities were in general very similar for the two procedures, with a strong statistical correlation between the two sets of values.

Reduction of ß-radiation exposure during preparation of 188Re-labelled Lipiodol for hepatocellular carcinoma treatment.

Rhenium-188 (188Re) is of widespread interest for treating various diseases because of its attractive physical and chemical properties. The routine preparation of therapeutic doses of 188Re-labelled tracers can result in significant radiation exposure to the operator. We studied the impact of automating the preparation of 188Re-Lipiodol on the radiochemist's exposure, as well as the importance of the model of syringe shielding. To monitor radiation exposure continuously readable electronic personal dosimeters were used. Thermoluminescence dosimeters were fixed to the probable most exposed fingers of the radiochemist during preparation of the radiotracer and during the syringing. Dose rates were measured using a Babyline. Automation of the synthesis reduced personal dose equivalents from 2.60±4.35 to 1.61±1.20 µSv/GBq [Hp(10)] and from 38.37±55.28 to 21.84±16.14 µSv/GBq [Hp(0.07)]. Dose to the extremities was also reduced (-80% for the right hand; -58% for the left one). The Lemer-Pax PSWG syringe shield led to a slightly lower dose to the hands compared with the Medisystem (1.1±0.27 vs. 1.34±0.6 mSv/GBq for the right finger). Automation of the synthesis leads to a significant decrease in radiation exposure to the operator. The Lemer-Pax PSWG syringe shield provides better hand protection than the smaller Medisystem Mediclic.

Cross-section measurements and nuclear model calculation for proton induced nuclear reaction on zirconium.

Proton induced nuclear reactions were measured with stacked-foil technique on natural zirconium targets up to 16.7MeV. Excitation functions were measured for the production of (90,92m,95m,95g,96)Nb and (88)Y. Cumulative cross-section, thick target yields and activation functions were deduced and compared with the available experimental data, as well as with the nuclear models codes; ALICE-IPPE, EMPIRE and TALYS. The integral yields for thick targets were deduced from the measured excitation function of the produced radionuclides.

Production study of high specific activity NCA Re-186g by proton and deuteron cyclotron irradiation.

Very high specific activity (A(S)) (186g)Re could be produced by either proton or deuteron cyclotron irradiation on highly enriched (186)W target in no-carrier-added (NCA) form, leading to a A(S) very close to the theoretical carrier free (CF) value of 6.88GBqmicrog(-1). Thick target yields (TTYs), obtained irradiating both thick metal W targets of natural isotopic composition and highly enriched pressed powdered (186)W targets, were measured at different particles energies taking into account high accuracy and precision on both yield and beam energy. The measurement of radionuclidic purity of (186g)Re obtained activating highly enriched (186)W by both p and d beams were also carried out and accurately compared. The excitation function as thin-target yields (tty, i.e. proportional to the reaction cross-sections) and the integrated TTYs for all Re (A=181, 182, 183, 184, 186 and their metastable levels), W and Ta co-produced radionuclides will be presented elsewhere in deep details.

Determinação dos fatores de recuperação do 111In e do 99mTc na quantificação de atividade com imagens SPECT / Determination of 111In and 99mTc recovery in the quantification of activity with SPECT imaging

OBJETIVO: Determinar, experimentalmente, os coeficientes de recuperação do 111In e do 99mTc usando imagens SPECT. MATERIAIS E MÉTODOS: Quatro diferentes concentrações de 111In e de 99mTc foram usadas para quantificar a atividade em esferas de diferentes tamanhos. As imagens foram obtidas com um equipamento híbrido SPECT/CT, com dois detectores. A reconstrução das imagens foi realizada usando o método iterativo ordered subset expectation maximization (OSEM). A correção de atenuação foi realizada com o uso de um mapa de atenuação e a correção de espalhamento foi realizada usando a técnica das janelas de energia. RESULTADOS: Os resultados mostraram que o efeito do volume parcial foi observado de forma mais significativa para as esferas com volume < 6 ml. Para o 111In, os resultados mostram uma dependência com relação às concentrações usadas nas esferas e ao nível de background usado. Para o 99mTc, pôde-se observar uma tendência à subestimação dos resultados quando os níveis mais altos de background foram utilizados. CONCLUSÃO: É necessário usar os fatores de correção para compensar o efeito do volume parcial em objetos com volume < 6 ml para ambos os radionuclídeos. A subtração das contagens espúrias presentes nas imagens SPECT foi o fator que mais influenciou na quantificação da atividade nessas esferas.

OBJECTIVE: To experimentally determine the 99mTc and 111In activity recovery coefficients in SPECT imaging. MATERIALS AND METHODS: Four different 99mTc and 111In concentrations were utilized for quantifying activity in spheres of four different sizes. Images were obtained with a hybrid dual-head SPECT-CT imaging system. The ordered subset expectation maximization (OSEM) iterative method was utilized for images reconstruction. An attenuation map was utilized for attenuation correction, and the multiple energy window technique for scattering correction. RESULTS: Results for spheres < 6 ml in volume were significantly affected by the partial volume effect. For 111In quantification, results show a dependence on sphere concentrations and background levels. For 99mTc quantification, there was a tendency towards values underestimation with higher background levels. CONCLUSION: Correction factors must be utilized for compensating the partial volume effect on objects with < 6 ml in volume for both radionuclides. Background subtraction to compensate spurious count present on SPECT images has a significant influence on the quantification of activity, especially for the smaller objects.

Dose rate estimation around a 60Co gamma-ray irradiation source by means of 115mIn photoactivation.

Photoactivation of nuclear isomer (115m)In with a halflife of 4.48 h occurs by (60)Co gamma-ray irradiation. This is because the resonance gamma-ray absorption occurs at 1078 keV level for stable (115)In, and that energy gamma-rays are produced by Compton scattering of (60)Co primary gamma-rays. In this work, photoactivation of (115m)In was applied to estimate the dose rate distribution around a (60)Co irradiation source utilizing a standard dose rate taken by alanine dosimeter. The (115m)In photoactivation was measured at 10 to 160 cm from the (60)Co source. The derived dose rate distribution shows a good agreement with both alanine dosimeter data and Monte Carlo simulation. It is found that angular distribution of the dose rate along a circumference at radius 2.8 cm from the central axis shows +/- 10% periodical variation reflecting the radioactive strength of the source rods, but less periodic distribution at radius 10 and 20 cm. The (115m)In photoactivation along the vertical direction in the central irradiation port strongly depends on the height and radius as indicated by Monte Carlo simulation. It is demonstrated that (115m)In photoactivation is a convenient method to estimate the dose rate distribution around a (60)Co source.

Avaliação in vitro da infiltração de fluidos pela interface implante-pilar intermediário de três sistemas com conexão do tipo cone Morse e da capacidade de vedação de um material / In vitro evaluation of fluid penetration at the implant-abutment interface of three cone Morse systems and sealing ability of a material

A infiltração de fluido e bactérias nos espaços internos dos implantes foi observada em pilares intermediários parafusados, tanto em situações in vitro quanto in vivo devido à microfenda existente entre o implante e o pilar intermediário. Esse fato pode estar relacionado com a inflamação dos tecidos periimplantares e também com a produção de mau odor. O objetivo do presente estudo in vitro foi avaliar e comparar a ocorrência de infiltração de fluidos pela interface implante-pilar intermediário em três sistemas de implante com conexão do tipo cone Morse, e a capacidade de vedação de um adesivo anaeróbico, utilizando o radioisótopo Tecnécio-99m como marcador. Na primeira etapa, dez conjuntos implante-pilar intermediário de cada sistema foram imersos em solução contendo esse marcador, após a aplicação do torque recomendado pelo fabricante, e foram mantidos em pressão constante de 2 atm por um minuto. Na segunda etapa, um adesivo anaeróbico foi aplicado no pilar intermediário antes do mesmo ser parafusado ao seu respectivo implante. Após a aplicação da pressão, o infiltrado presente no interior dos implantes foi coletado com pontas de papel. Esse material foi depositado em tubos de ensaio para posterior leitura da radioatividade presente. A infiltração de fluido pela interface implante-pilar intermediário mostrou ser um fenômeno mensurável em todas as amostras dos três sistemas de implante com conexão do tipo cone Morse testados...

A quantidade de infiltrado variou entre os sistemas e entre as amostras. A inconstância das amostras foi observada em todos os sistemas, no entanto, foi observado que o valor de infiltrado encontrado no Grupo 1 foi significantemente maior (p<0,05) do que o encontrado no Grupo 2, e não houve diferença estatística significante entre os Grupos 1 e 3, e entre os Grupos 2 e 3. Também foi observado que, com o uso do adesivo anaeróbico, os sistemas apresentaram diminuição da quantidade de infiltrado, sendo que a análise estatística dos valores obtidos com e sem o seu uso, mostraram significância a 1%. Além disso, com o uso do adesivo anaeróbico os três sistemas de implante testados passaram a ter comportamento semelhante, não tendo sido encontrada diferença estatística significante entre eles (p=0,5451). Considerando os limites deste estudo, pode-se concluir que os três sistemas de implante com conexão do tipo cone Morse testados permitiram a passagem de fluido do meio externo para o interior dos implantes, e que o material testado não foi capaz de impedir a penetração de fluido, apesar de ter reduzido significantemente a quantidade de infiltrado em todos os sistemas.

It has been observed that in implants with screw-retained abutments, in in vitro as well as in vivo conditions, bacteria and fluids can penetrate the inner implant space as consequence of an existing microgap at the implant-abutment interface. This fact can be related to peri-implant tissue inflammation and malodor. The aim of the present study was to evaluate and compare the occurrence of fluid penetration throught implant-abutment interface in three cone Morse implant systems and sealing ability of an anaerobic adhesive using a radioisotope as trace. In the first phase, ten implant-abutment sets of each system were immersed in a solution with radioisotope, after manufacture recommended torque application. All assemblies were kept in a constant pressure of 2 atm for one minute. In the second phase, an anaerobic adhesive was applied before the abutments been torque-tightened to the same implant. After the pressure application, material inside implant bodies was colleted using a paper cone that was transferred to tubes for posterior verification of radioactivity.

Fluid penetration at the implant-abutment interface was seen to be a recordable phenomenon in each assembly of the three cone Morse systems tested in this study. The quantity of infiltrated varied between systems and assemblies. The variable of the samples was observed in all systems, however, it was noted that the value of infiltrate found in Group 1 was significantly higher than that found in Group 2, and there was no statistical significant difference between the groups 1 and 3, and between groups 2 and 3. It was also noted that, using the adhesive anaerobic, the implant systems showed reduce infiltrate, and statistical analysis presented significance to 1%. Moreover, with the use of anaerobic adhesive, all three implant systems tested presented similar pattern, and no significant statistical difference was found (p=0,5451). Considering the limits of this study, the following conclusions can be drawn: the three cone Morse implant systems tested allowed the passage of fluid from external to the inside of the implants, and that the material tested was not capable of preventing the fluid penetration, despite having reduced significantly the amount of infiltrate in all systems

Excitation function for 63Cu(n,p)63Ni reaction in neutron energy range up to 15 MeV.

The excitation function for the (63)Cu(n,p)(63)Ni reaction has been measured by activation method using the 4.5 MV Dynamitron accelerator of the Fast Neutron Laboratory of Tohoku University. Copper plates and hollow spherical copper shells were irradiated by neutrons of various energy up to 14.9 MeV produced by the T(p,n), D(d,n), and T(d,n) reactions. The (63)Ni produced in the irradiated copper target was chemically separated. The beta-rays emitted from the extracted (63)Ni were measured by a liquid scintillation method. The cross sections obtained were compared with the evaluated data files of JENDL-3.3, ENDF/B-VI and FENDL/A-2.0. Consequently, it is found that FENDL/A-2.0 is consistent with our experimental data in the energy range studied in this work. The effect of proton shell appeared in the excitation function obtained is also discussed.

A possible in vivo generator 103Pd/103mRh--recoil considerations.

The use of Auger emitters as potential radiopharmaceuticals is increasingly investigated. One such radionuclide of interest is (103m)Rh. This can be produced from (103)Ru or from (103)Pd in an in vivo generator. A potential problem with this concept is the recoil of the (103m)Rh out of the carrier molecule and even out of the target cell. In order to determine whether this would happen in the (103)Pd/(103m)Rh case calculations were done to prove that this does not happen. From theoretical considerations it seems that the (103)Pd/(103m)Rh in vivo generator system would be possible.

Ratio of aerosol and gases of radioactive chlorine and particle size distribution of aerosol formed by high-energy proton irradiation.

To estimate internal doses due to the inhalation of radionuclides produced by the nuclear spallation of the air nuclei in high-energy proton accelerator facilities, the physicochemical properties of radionuclides are very important. Thus, the ratio of aerosol and gases of 38Cl and 39Cl formed by irradiating argon gas-added air with a 48 MeV proton beam has been measured. Radionuclides of 38Cl and 39Cl exist as aerosol, acid gas and non-acid gas. The percentages of activity of 38Cl and 39Cl aerosols are about 80%. The number size distributions of non-radioactive aerosol were characterised by two peaks with diameters of 10-20 nm and larger than 20 nm. As a result predicted by a simple surface model, it was found that the activity size distribution of 38Cl aerosols can be regarded as that having a single peak at 120 nm.

Neutron-induced 63Ni in copper samples from Hiroshima and Nagasaki: a comprehensive presentation of results obtained at the Munich Maier-Leibnitz Laboratory.

Those inhabitants of Hiroshima and Nagasaki who were affected by the A-bomb explosions, were exposed to a mixed neutron and gamma radiation field. Few years later about 120,000 survivors of both cities were selected, and since then radiation-induced late effects such as leukemia and solid tumors are being investigated in this cohort. When the present study was initiated, the fast neutron fluences that caused the neutron doses of these survivors had never been determined experimentally. In principle, this would have been possible if radioisotopes produced by fast neutrons from the A-bomb explosions had been detected in samples from Hiroshima and Nagasaki at distances where the inhabitants survived. However, no suitable radioisotope had so far been identified. As a contribution to a large international effort to re-evaluate the A-bomb dosimetry, the concentration of the radionuclide (63)Ni (half-life 100.1 years) has been measured in copper samples from Hiroshima and Nagasaki. These measurements were mainly performed at the Maier-Leibnitz-Laboratory in Munich, Germany, by means of accelerator mass spectrometry. Because the (63)Ni had been produced in these samples by fast A-bomb neutrons via the reaction (63)Cu(n,p)(63)Ni, these measurements allow direct experimental validation of calculated neutron doses to the members of the LSS cohort, for the first time. The results of these efforts have already been published in a compact form. A more detailed discussion of the methodical aspects of these measurements and their results are given in the present paper. Eight copper samples that had been significantly exposed to fast neutrons from the Hiroshima A-bomb explosion were investigated. In general, measured (63)Ni concentrations decreased in these samples with increasing distance to the hypocenter, from 4 x 10(6 ) (63)Ni nuclei per gram copper at 391 m, to about 1 x 10(5 ) (63)Ni nuclei per gram copper at about 1,400 m. Additional measurements performed on three large-distant copper samples from Hiroshima (distance to the hypocenter 1,880-7,500 m) and on three large-distant copper samples from Nagasaki (distance to the hypocenter 3,931-4,428 m) that were not exposed significantly to A-bomb neutrons, suggest a typical background concentration of about 8 x 10(4 ) (63)Ni nuclei per gram copper. If the observed background is accounted for, the results are consistent with state-of-the-art neutron transport calculations for Hiroshima, in particular for those distances where the victims survived and were included in the life span study cohort.

Neutron-induced dosimetry reaction cross-section measurements from the threshold up to 20 MeV.

New measured results were obtained for the (58)Ni(n,p)(58)Co, (58)Ni(n,2n)(57)Ni, (58)Ni(n,x)(57)Co, (60)Ni(n,p)(60)Co, (59)Co(n,2n)(58)Co, (59)Co(n,p)(59)Fe, (63)Cu(n,alpha)(60)Co, (204)Pb(n,n')(204 m)Pb and (204)Pb(n,2n)(203)Pb reaction cross-sections. These reactions may be of interest for dosimetry. Measurements were taken at the 7 MV Van de Graaff accelerator at IRMM, Geel, using the activation technique in combination with high-resolution gamma ray spectrometry. The present results are compared with other measurements, evaluated data and model calculations.

Excitation functions of (p,x) reactions on natural nickel between proton energies of 2.7 and 27.5 MeV.

Excitation functions have been measured for a number of proton induced nuclear reactions on natural nickel in the energy range from 27.5 MeV down to their threshold energy, using the activation method on stacked foils. Excitation functions for the reactions leading to the formation of (60)Cu, (61)Cu, (56)Ni, (57)Ni, (55)Co, (56)Co, (57)Co and (58)Co are presented and compared with earlier reported experimental data. Comparison with the recommended data reported by the International Atomic Energy Agency [Gul et al., 2001. Charged particle cross section database for medical radioisotope production. IAEA-TECDOC-1211, IAEA Vienna, Austria] is also presented when possible.

Spatial distributions of residuals produced inside a spallation target.

The spallation target model of an accelerator driven system (ADS), consisting of six 5 cm thick and 16 cm in diameter Pb segments, was constructed. Three sets of 17 Bi samples (1/2 inch in diameter and 1 mm thick) were placed in 3 Pb disc-shaped holders inside the target at 5, 10 and 15 cm from its front. After irradiation with 660 MeV proton beam gamma-spectra of radioisotopes produced in Bi were collected several times for each sample with the use of HPGe detectors in order to identify the radioisotopes and to determine their absolute activities. Their spatial distributions were then compared with respective values obtained in the calculations made with the use of FLUKA and/or MCNPX code. A fair agreement with the experiment has been observed.

Development of a quantum molecular dynamic (QMD) model to describe fission and fragment production.

In this paper is presented the development of a QMD model for the description of the spallation reaction at energies from a few MeV to a few hundred MeV. The QMD model is developed using a new evaporation-fission model, the generalised evaporation model (GEM2). The spectrum of particles and residual nuclide mass and charge distributions in reactions of protons and neutrons with heavy targets (238U, 208Pb, 207Pb and 2206Pb) has been calculated using the QMD+GEM2 model.

Efeitos da braquiterapia intra-arterial com samário-153 sobre a neoproliferação intimal / Effects of intra-arterial brachytherapy with Samarium- 153 over intimal neoproliferation

Estudos experimentais e em humanos o balão de angioplastia pode levar à estenose pela migração e proliferação das células musculares lisas e a síntese de matriz extracelular. Estudos têm mostrado a ação da braquiterapia contra esses mecanismos. Nós desenhamos este estudo para avaliar a inibição do tecido de proliferação pelo Samário-153(153Sm). Quarenta e três coelhos hipercolesterolêmicos foram submetidos à lesão de ambas artérias ilíacas e separados em três grupos: com a dose de 15 Gy (n=14), com 60 Gy (n=36) e controle (n=36). A análise histológica morfométrica mostrou significante redução da neo-íntima com 15 Gy, quando comparado com os outros grupos. A dose de 60 Gy teve modificações estruturais e tissulares sugestivas de radiolesão.As previous demonstrated by experimental and human models, balloon dilation during angioplasty could lead to injury and stenosis due to smooth muscle cell migration and proliferation as well as extracellular matrix synthesis. Brachytherapy has been usefull against these factors. We pourposed was this study to evaluate neointimal tissue proliferation inhibition by Samarium-153 (153 Sm). Forty-three hypercholesterolemic rabbits underwent balloon injury in their both iliac arteries. They were separated into three groups: throught 15 Gy irradiation doses (n=14), 60 Gy (n=36) and control group (n= 36). Histopathologic and morphometric analysis showed a significant neointimal reduction with 15 Gy, comparing to others groups to control and 60 Gy dosis. The 60 y doses determined structure and tissue changes as the ones of radiation lesion...