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Joyce M. Hansen - One of the best experts on this subject based on the ideXlab platform.
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Radiation Sterilization: Dose Is Dose
Biomedical Instrumentation & Technology, 2020Co-Authors: Joyce M. Hansen, Niki Fidopiastis, Trabue Bryans, Michelle Luebke, Terri RymerAbstract:Abstract In the Radiation Sterilization arena, the question often arises as to whether Radiation resistance of microorganisms might be affected by the energy level of the Radiation source and the rate of the dose delivered (kGy/time). The basis for the question is if the microbial lethality is affected by the Radiation energy level and/or the rate the dose is delivered, then the ability to transfer dose among different Radiation sources could be challenged. This study addressed that question by performing a microbial inactivation study using two Radiation sources (gamma and electron beam [E-beam]), two microbial challenges (natural product bioburden and biological indicators), and four dose rates delivered by three energy levels (1.17 MeV [gamma], 1.33 MeV [gamma], and 10 MeV [high-energy E-beam]). Based on analysis of the data, no significant differences were seen in the rate of microbial lethality across the range of Radiation energies evaluated. In summary, as long as proof exists that the specified dose is delivered, dose is dose.
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Revision of the ISO and EN Radiation Sterilization standards
Radiation Physics and Chemistry, 2002Co-Authors: Arne Miller, Joyce M. HansenAbstract:Abstract The Radiation Sterilization standards, ISO 11137 and EN 552, are now being revised under “ISO lead”, with the aim of producing only one international standard, although in four parts: (1) requirements, (2) dose-setting methods, (3) dose-substantiation methods and (4) dosimetry. Several aspects of the old standards that have caused problems, when they were used in practice, are addressed in the revision. Input from users of the standards is necessary in order that the standards be developed as useful tools in the documentation of Radiation Sterilization.
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ISO Radiation Sterilization standards
Radiation Physics and Chemistry, 1998Co-Authors: Byron J. Lambert, Joyce M. HansenAbstract:Abstract This presentation provides an overview of the current status of the ISO Radiation Sterilization standards. The ISO standards are voluntary standards which detail both the validation and routine control of the Sterilization process. ISO 11137 was approved in 1994 and published in 1995. When reviewing the standard you will note that less than 20% of the standard is devoted to requirements and the remainder is guidance on how to comply with the requirements. Future standards developments in Radiation Sterilization are being focused on providing additional guidance. The guidance that is currently provided in informative annexes of ISO 11137 includes: device/packaging materials, dose setting methods, and dosimeters and dose measurement, currently, there are four Technical Reports being developed to provide additional guidance: 1. 1. AAMI Draft TIR, “Radiation Sterilization Material Qualification” 2. 2. ISO TR 13409-1996, “Sterilization of health care products — Radiation Sterilization — Substantiation of 25 kGy as a Sterilization dose for small or infrequent production batches” 3. 3. ISO Draft TR, “Sterilization of health care products — Radiation Sterilization Selection of a Sterilization dose for a single production batch” li]4. ISO Draft TR, “Sterilization of health care products — Radiation Sterilization-Product Families, Plans for Sampling and Frequency of Dose Audits.”
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Reducing Sample Sizes of Aami Gamma Radiation Sterilization Verification Experiments and Dose Audits
Quality Engineering, 1996Co-Authors: George W. Phillips, Wayne A. Taylor, Harold E. Sargent, Joyce M. HansenAbstract:"Guideline for Gamma Radiation Sterilization" provides sampling plans for performing initial dose verification experiments and quarterly dose audits. Alternative sampling plans are presented which provide equivalent protection. The first group..
Mark R. Forwood - One of the best experts on this subject based on the ideXlab platform.
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reducing the Radiation Sterilization dose improves mechanical and biological quality while retaining sterility assurance levels of bone allografts
Bone, 2013Co-Authors: Huynh Nguyen, A I Cassady, M B Bennett, Evelyne Gineyts, David A F Morgan, Mark R. ForwoodAbstract:BACKGROUND:Bone allografts carry a risk of infection, so terminal Sterilization by gamma irRadiation at 25kGy is recommended; but is deleterious to bone quality. Contemporary bone banking significantly reduces initial allograft bioburden, questioning the need to sterilize at 25kGy. METHODS:We inoculated allograft bone with Staphylococcus epidermidis and Bacillus pumilus, then exposed them to gamma irRadiation at 0, 5, 10, 15, 20 and 25kGy. Mechanical and biological properties of allografts were also assessed. Our aim was to determine an optimal dose that achieves sterility assurance while minimizing deleterious effects on allograft tissue. RESULTS:20-25kGy eliminated both organisms at concentrations from 101 to 103CFU, while 10-15kGy sterilized bone samples to a bioburden concentration of 102CFU. IrRadiation did not generate pro-inflammatory bone surfaces, as evidenced by macrophage activation, nor did it affect attachment or proliferation of osteoblasts. At doses =10kGy, the toughness of cortical bone was reduced (P<0.05), and attachment and fusion of osteoclasts onto irradiated bone declined at 20 and 25kGy (P<0.05). There was no change in collagen cross-links, but a significant dose-response increase in denatured collagen (P<0.05). CONCLUSIONS:Our mechanical and cell biological data converge on 15kGy as a threshold for Radiation Sterilization of bone allografts. Between 5 and 15kGy, bone banks can undertake validation that provides allografts with an acceptable sterility assurance level, improving their strength and biocompatibility significantly. CLINICAL RELEVANCE:The application of Radiation Sterilization doses between 5 and 15kGy will improve bone allograft mechanical performance and promote integration, while retaining sterility assurance levels. Improved quality of allograft bone will promote superior clinical outcomes.
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Validation of 11 kGy as a Radiation Sterilization Dose for Frozen Bone Allografts
Journal of Arthroplasty, 2010Co-Authors: Huynh Nguyen, D. A. F. Morgan, Mark R. ForwoodAbstract:A Radiation Sterilization dose (RSD) of 25 kGy is deleterious to bone allografts. This study aimed to establish a lower RSD for bone allografts using method 1 of International Standard Organisation 11137.2:2006. This provides a database to select an RSD corresponding to an allograft's bioburden, given that the bioburden's gamma resistance is equal to or less than the standard. This can be verified by irradiating 100 allografts at a dose selected to provide a sterility assurance level of 10(-2). The bioburden of our allografts was 0, which prescribed a verification dose of 1.3 kGy. After irradiating 100 allografts, sterility tests returned no positive cultures. We therefore validated an RSD of 11 kGy for allografts with that bioburden. According to the standard, this RSD provides a sterility assurance level of 10(-6) for bone allografts.
Huynh Nguyen - One of the best experts on this subject based on the ideXlab platform.
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reducing the Radiation Sterilization dose improves mechanical and biological quality while retaining sterility assurance levels of bone allografts
Bone, 2013Co-Authors: Huynh Nguyen, A I Cassady, M B Bennett, Evelyne Gineyts, David A F Morgan, Mark R. ForwoodAbstract:BACKGROUND:Bone allografts carry a risk of infection, so terminal Sterilization by gamma irRadiation at 25kGy is recommended; but is deleterious to bone quality. Contemporary bone banking significantly reduces initial allograft bioburden, questioning the need to sterilize at 25kGy. METHODS:We inoculated allograft bone with Staphylococcus epidermidis and Bacillus pumilus, then exposed them to gamma irRadiation at 0, 5, 10, 15, 20 and 25kGy. Mechanical and biological properties of allografts were also assessed. Our aim was to determine an optimal dose that achieves sterility assurance while minimizing deleterious effects on allograft tissue. RESULTS:20-25kGy eliminated both organisms at concentrations from 101 to 103CFU, while 10-15kGy sterilized bone samples to a bioburden concentration of 102CFU. IrRadiation did not generate pro-inflammatory bone surfaces, as evidenced by macrophage activation, nor did it affect attachment or proliferation of osteoblasts. At doses =10kGy, the toughness of cortical bone was reduced (P<0.05), and attachment and fusion of osteoclasts onto irradiated bone declined at 20 and 25kGy (P<0.05). There was no change in collagen cross-links, but a significant dose-response increase in denatured collagen (P<0.05). CONCLUSIONS:Our mechanical and cell biological data converge on 15kGy as a threshold for Radiation Sterilization of bone allografts. Between 5 and 15kGy, bone banks can undertake validation that provides allografts with an acceptable sterility assurance level, improving their strength and biocompatibility significantly. CLINICAL RELEVANCE:The application of Radiation Sterilization doses between 5 and 15kGy will improve bone allograft mechanical performance and promote integration, while retaining sterility assurance levels. Improved quality of allograft bone will promote superior clinical outcomes.
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Validation of 11 kGy as a Radiation Sterilization Dose for Frozen Bone Allografts
Journal of Arthroplasty, 2010Co-Authors: Huynh Nguyen, D. A. F. Morgan, Mark R. ForwoodAbstract:A Radiation Sterilization dose (RSD) of 25 kGy is deleterious to bone allografts. This study aimed to establish a lower RSD for bone allografts using method 1 of International Standard Organisation 11137.2:2006. This provides a database to select an RSD corresponding to an allograft's bioburden, given that the bioburden's gamma resistance is equal to or less than the standard. This can be verified by irradiating 100 allografts at a dose selected to provide a sterility assurance level of 10(-2). The bioburden of our allografts was 0, which prescribed a verification dose of 1.3 kGy. After irradiating 100 allografts, sterility tests returned no positive cultures. We therefore validated an RSD of 11 kGy for allografts with that bioburden. According to the standard, this RSD provides a sterility assurance level of 10(-6) for bone allografts.
Clare M. Rimnac - One of the best experts on this subject based on the ideXlab platform.
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Alterations in damage processes in dense cancellous bone following gamma-Radiation Sterilization.
Journal of biomechanics, 2010Co-Authors: Stephanie J. Dux, Daniel S. Ramsey, E.h. Chu, Clare M. Rimnac, Christopher J. HernandezAbstract:Abstract Structurally intact cancellous bone allograft is an attractive tissue form because its high porosity can provide space for delivery of osteogenic factors and also allows for more rapid and complete in-growth of host tissues. Gamma Radiation Sterilization is commonly used in cancellous bone allograft to prevent disease transmission. Commonly used doses of gamma Radiation Sterilization (25–35 kGy) have been shown to modify cortical bone post-yield properties and crack propagation but have not been associated with changes in cancellous bone material properties. The purpose of this study was to determine the effects of irRadiation on the elastic and yield properties and microscopic tissue damage processes in dense cancellous bone. Cancellous bone specimens (13 control, 14 irradiated to 30 kGy) from bovine proximal tibiae were tested in compression to 1.3% apparent strain and examined for microscopic tissue damage. The yield strain in irradiated specimens (0.93±0.11%, mean±SD) did not differ from that in control specimens (0.90±0.11%, p =0.44). No differences in elastic modulus were observed between groups after accounting for differences in bone volume fraction. However, irradiated specimens showed greater residual strain ( p =0.01), increased number of microfractures ( p =0.02), and reduced amounts of cross-hatching type damage ( p
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The effect of gamma Radiation Sterilization on the fatigue crack propagation resistance of human cortical bone.
The Journal of bone and joint surgery. American volume, 2004Co-Authors: Erika Jasmin Mitchell, Allison M. Stawarz, Ramazan Kayacan, Clare M. RimnacAbstract:Background: Clinical evidence has suggested that the rate of fracture in allografts sterilized with gamma Radiation may be higher than that in controls. Gamma Radiation Sterilization has been shown to affect the post-yield properties of bone but not the elastic modulus. Since most allograft fractures occur with subcritical loads during activities of daily living, it may be that the fatigue properties of irradiated allografts are diminished. In this study, the fatigue crack propagation behavior of cortical bone sterilized with gamma Radiation was compared with that of gender and age-matched controls. We hypothesized that gamma Radiation significantly reduces the resistance of cortical bone to fatigue crack growth. Methods: Specimens for fatigue crack propagation testing were machined from four pairs of fresh-frozen human femora obtained from four individuals (a younger male, younger female, older male, and older female donor). Half of the specimens were sterilized with 31.7 kGy of gamma Radiation. The specimens were cyclically loaded to failure in a servohydraulic testing system, and crack growth was monitored. The cyclic stress intensity factor and the fatigue crack growth rate were calculated to examine the kinetics of fatigue crack growth. Following testing, the damage zone around the fracture plane was analyzed histologically. Results: The morphology and kinetics of crack growth in irradiated specimens differed from the control data. Overall, the irradiated bone was significantly less resistant to fatigue crack growth than was control tissue (p < 0.05). There was less microdamage associated with fracture in the irradiated specimens than in the control specimens, with the exception of the bone from the older female donor. Conclusions: Gamma Radiation Sterilization significantly reduces the fatigue crack propagation resistance of cortical bone. Irradiated specimens also demonstrate a smaller amount of microdamage along the fracture plane. These findings may be due to ultrastructural alterations in the collagen matrix caused by Radiation. Clinical Relevance: This study suggests that, despite having pre-yield mechanical properties that are similar to those of nonirradiated bone, gamma-Radiation-sterilized allograft may be more predisposed to fracture even under the subcritical loads that occur during the activities of daily living.
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Fracture resistance of gamma Radiation sterilized cortical bone allografts.
Journal of orthopaedic research : official publication of the Orthopaedic Research Society, 2001Co-Authors: Ozan Akkus, Clare M. RimnacAbstract:Gamma Radiation is widely used for Sterilization of human cortical bone allografts. Previous studies have reported that cortical bone becomes brittle due to gamma Radiation Sterilization. This embrittlement raises concern about the performance of a Radiation sterilized allograft in the presence of a stress concentration that might be surgically introduced or biologically induced. The purpose of this study was to investigate the effect of gamma Radiation Sterilization on the fracture resistance of human femoral cortical bone in the presence of a stress concentration. Fracture toughness tests of specimens sterilized at a dose of 27.5 kGy and control specimens were conducted transverse and longitudinal to the osteonal orientation of the bone tissue. The formation of damage was monitored with acoustic emission (AE) during testing and was histologically observed following testing. There was a significant decrease in fracture toughness due to irRadiation in both crack growth directions. The work-to-fracture was also significantly reduced. It was observed that the ability of bone tissue to undergo damage in the form of microcracks and diffuse damage was significantly impaired due to Radiation Sterilization as evidenced by decreased AE activity and histological observations. The results of this study suggest that, for cortical bone irradiated at 27.5 kGy, it is easier to initiate and propagate a macrocrack from a stress concentration due to the inhibition of damage formation at and near the crack tip.
Neil B. Beals - One of the best experts on this subject based on the ideXlab platform.
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Fatigue performance of ultra-high-molecular-weight polyethylene: effect of gamma Radiation Sterilization
Biomaterials, 1996Co-Authors: Willard L. Sauer, Kevin Weaver, Neil B. BealsAbstract:Ultra-high-molecular-weight polyethylene (UHMWPE) failure presents a significant materials concern in the orthopaedic community. Clinical failure following joint arthroplasty can result from the biological response to wear debris as well as structural failure owing to UHMWPE fatigue. In this study, cantilever rotating beam fatigue testing was conducted on GUR 415 UHMWPE in both the unsterilized and gamma Radiation sterilized conditions. Calculations of flexural fatigue stresses were based on extreme fibre stresses and assumed negligible plastic deformation. Both material conditions exhibited similar fatigue strengths at 250,000 cycles (approximately 41 MPa) and at one million cycles (approximately 36 MPa), but a large difference developed after two million cycles. At ten million cycles, the unsterilized condition exhibited a fatigue strength of approximately 31 MPa, while the gamma-sterilized condition exhibited a reduced fatigue strength of approximately 18 MPa, an approximate decrease of 42%. High-cycle fatigue testing was necessary to fully characterize this behaviour owing to the pronounced difference in fatigue behaviour beyond two million cycles. These results suggest that gamma Radiation Sterilization of UHMWPE medical implants reduces their resistance to cyclic loading and, subsequently, may contribute to the associated fatigue-related failures which have been reported clinically.
