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Habib Zaidi - One of the best experts on this subject based on the ideXlab platform.
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Fetal and Maternal Absorbed Dose Estimates for Positron-Emitting Molecular Imaging Probes
2016Co-Authors: Tianwu Xie, Habib ZaidiAbstract:PET and hybrid (PET/CT and PET/MR) imaging currently play a piv-otal role in clinical diagnosis, staging and restaging, treatment, and surveillance of several diseases. As such, limiting the radiation exposure of special patients, such as pregnant women, from PET procedures is an important challenge that needs to be appropriately addressed because of the high sensitivity of the developing embryo/ fetus to ionizing radiation. Therefore, accurate radiation dose cal-culation for the embryo/fetus and pregnant patient from common Positron-Emitting radiotracers is highly desired.Methods: To obtain representative estimates of radiation dose to the human body, re-alistic biologic and physical models should be used. In this work, we evaluate the S values of 9 Positron-Emitting Radionuclides (11C, 13N, 15O, 18F, 64Cu, 68Ga, 82Rb, 86Y, and 124I) and the absorbed and effective doses for 21 Positron-Emitting labeled radiotracers using realistic anthropomorphic computational phantoms of early preg
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Pediatric radiation dosimetry for Positron-Emitting Radionuclides using anthropomorphic phantoms.
Medical physics, 2013Co-Authors: Tianwu Xie, Wesley E. Bolch, Choonsik Lee, Habib ZaidiAbstract:Purpose: Positron emission tomography (PET) plays an important role in the diagnosis, staging, treatment, and surveillance of clinically localized diseases. Combined PET/CT imaging exhibits significantly higher sensitivity, specificity, and accuracy than conventional imaging when it comes to detecting malignant tumors in children. However, the radiation dose from Positron-Emitting radionuclide to the pediatric population is a matter of concern since children are at a particularly high risk when exposed to ionizing radiation. Methods: The authors evaluate the absorbed fractions and specific absorbed fractions (SAFs) of monoenergy photons/electrons as well as S-values of 9 Positron-Emitting Radionuclides (C-11, N-13, O-15, F-18, Cu-64, Ga-68, Rb-82, Y-86, and I-124) in 48 source regions for 10 anthropomorphic pediatric hybrid models, including the reference newborn, 1-, 5-, 10-, and 15-yr-old male and female models, using the Monte Carlo N-Particle eXtended general purpose Monte Carlo transport code. Results: The self-absorbed SAFs and S-values for most organs were inversely related to the age and body weight, whereas the cross-dose terms presented less correlation with body weight. For most source/target organ pairs, Rb-82 and Y-86 produce the highest self-absorbed and cross-absorbed S-values, respectively, while Cu-64 produces the lowest S-values because of the low-energy and high-frequency of electron emissions. Most of the total self-absorbed S-values are contributed from non-penetrating particles (electrons and Positrons), which have a linear relationship with body weight. The dependence of self-absorbed S-values of the two annihilation photons varies to the reciprocal of 0.76 power of the mass, whereas the self-absorbed S-values of Positrons vary according to the reciprocal mass. Conclusions: The produced S-values for common Positron-Emitting Radionuclides can be exploited for the assessment of radiation dose delivered to the pediatric population from various PET radiotracers used in clinical and research settings. The mass scaling method for Positron-emitters can be used to derive patient-specific S-values from data of reference phantoms. (C) 2013 American Association of Physicists in Medicine.
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Effect of emaciation and obesity on small-animal internal radiation dosimetry for Positron-Emitting Radionuclides
European Journal of Nuclear Medicine and Molecular Imaging, 2013Co-Authors: Tianwu Xie, Habib ZaidiAbstract:Purpose Rats are widely used in biomedical research involving molecular imaging and therefore the radiation dose to animals has become a concern. The weight of laboratory animals might change through emaciation or obesity as a result of their use in various research experiments including those investigating different diet types. In this work, we evaluated the effects of changes in body weight induced by emaciation and obesity on the internal radiation dose from common Positron-Emitting Radionuclides.
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assessment of s values in stylized and voxel based rat models for Positron Emitting Radionuclides
Molecular Imaging and Biology, 2013Co-Authors: Tianwu Xie, Habib ZaidiAbstract:Purpose Positron emission tomography (PET) is a powerful tool in small animal research, enabling noninvasive quantitative imaging of biochemical processes in living subjects. However, the dosimetric characteristics of small animal PET imaging are usually overlooked, although the radiation dose may be significant. The variations of anatomical characteristics between the various computational models may result in differences in the dosimetric outcome.
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Age-dependent small-animal internal radiation dosimetry.
Molecular imaging, 2013Co-Authors: Tianwu Xie, Habib ZaidiAbstract:Rats at various ages were observed to present with different radiosensitivity and bioavailability for radiotracers commonly used in preclinical research. We evaluated the effect of age-induced changes in body weight on radiation dose calculations. A series of rat models at different age periods were constructed based on the realistic four-dimensional digital rat whole-body (ROBY) computational model. Particle transport was simulated using the MCNPX Monte Carlo code. Absorbed fractions (AFs) and specific absorbed fraction (SAFs) of monoenergetic photons/electrons and S values of eight Positron-Emitting Radionuclides were calculated. The SAFs and S values for most source-target pairs were inversely correlated with body weight. Differences between F-18 S values for most source-target pairs were between -1.5% and -2%/10 g difference in body weight for different computational models. For specific radiotracers, the radiation dose to organs presents a negative correlation with rat body weight. The SAFs for monoenergetic photons/electrons and S values for common Positron-Emitting Radionuclides can be exploited in the assessment of radiation dose delivered to rats at different ages and weights. The absorbed dose to organs is significantly higher in the low-weight young rat model than in the adult model, which would result in steep secondary effects and might be a noteworthy issue in laboratory animal internal dosimetry.
Tianwu Xie - One of the best experts on this subject based on the ideXlab platform.
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Fetal and Maternal Absorbed Dose Estimates for Positron-Emitting Molecular Imaging Probes
2016Co-Authors: Tianwu Xie, Habib ZaidiAbstract:PET and hybrid (PET/CT and PET/MR) imaging currently play a piv-otal role in clinical diagnosis, staging and restaging, treatment, and surveillance of several diseases. As such, limiting the radiation exposure of special patients, such as pregnant women, from PET procedures is an important challenge that needs to be appropriately addressed because of the high sensitivity of the developing embryo/ fetus to ionizing radiation. Therefore, accurate radiation dose cal-culation for the embryo/fetus and pregnant patient from common Positron-Emitting radiotracers is highly desired.Methods: To obtain representative estimates of radiation dose to the human body, re-alistic biologic and physical models should be used. In this work, we evaluate the S values of 9 Positron-Emitting Radionuclides (11C, 13N, 15O, 18F, 64Cu, 68Ga, 82Rb, 86Y, and 124I) and the absorbed and effective doses for 21 Positron-Emitting labeled radiotracers using realistic anthropomorphic computational phantoms of early preg
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Pediatric radiation dosimetry for Positron-Emitting Radionuclides using anthropomorphic phantoms.
Medical physics, 2013Co-Authors: Tianwu Xie, Wesley E. Bolch, Choonsik Lee, Habib ZaidiAbstract:Purpose: Positron emission tomography (PET) plays an important role in the diagnosis, staging, treatment, and surveillance of clinically localized diseases. Combined PET/CT imaging exhibits significantly higher sensitivity, specificity, and accuracy than conventional imaging when it comes to detecting malignant tumors in children. However, the radiation dose from Positron-Emitting radionuclide to the pediatric population is a matter of concern since children are at a particularly high risk when exposed to ionizing radiation. Methods: The authors evaluate the absorbed fractions and specific absorbed fractions (SAFs) of monoenergy photons/electrons as well as S-values of 9 Positron-Emitting Radionuclides (C-11, N-13, O-15, F-18, Cu-64, Ga-68, Rb-82, Y-86, and I-124) in 48 source regions for 10 anthropomorphic pediatric hybrid models, including the reference newborn, 1-, 5-, 10-, and 15-yr-old male and female models, using the Monte Carlo N-Particle eXtended general purpose Monte Carlo transport code. Results: The self-absorbed SAFs and S-values for most organs were inversely related to the age and body weight, whereas the cross-dose terms presented less correlation with body weight. For most source/target organ pairs, Rb-82 and Y-86 produce the highest self-absorbed and cross-absorbed S-values, respectively, while Cu-64 produces the lowest S-values because of the low-energy and high-frequency of electron emissions. Most of the total self-absorbed S-values are contributed from non-penetrating particles (electrons and Positrons), which have a linear relationship with body weight. The dependence of self-absorbed S-values of the two annihilation photons varies to the reciprocal of 0.76 power of the mass, whereas the self-absorbed S-values of Positrons vary according to the reciprocal mass. Conclusions: The produced S-values for common Positron-Emitting Radionuclides can be exploited for the assessment of radiation dose delivered to the pediatric population from various PET radiotracers used in clinical and research settings. The mass scaling method for Positron-emitters can be used to derive patient-specific S-values from data of reference phantoms. (C) 2013 American Association of Physicists in Medicine.
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Effect of emaciation and obesity on small-animal internal radiation dosimetry for Positron-Emitting Radionuclides
European Journal of Nuclear Medicine and Molecular Imaging, 2013Co-Authors: Tianwu Xie, Habib ZaidiAbstract:Purpose Rats are widely used in biomedical research involving molecular imaging and therefore the radiation dose to animals has become a concern. The weight of laboratory animals might change through emaciation or obesity as a result of their use in various research experiments including those investigating different diet types. In this work, we evaluated the effects of changes in body weight induced by emaciation and obesity on the internal radiation dose from common Positron-Emitting Radionuclides.
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assessment of s values in stylized and voxel based rat models for Positron Emitting Radionuclides
Molecular Imaging and Biology, 2013Co-Authors: Tianwu Xie, Habib ZaidiAbstract:Purpose Positron emission tomography (PET) is a powerful tool in small animal research, enabling noninvasive quantitative imaging of biochemical processes in living subjects. However, the dosimetric characteristics of small animal PET imaging are usually overlooked, although the radiation dose may be significant. The variations of anatomical characteristics between the various computational models may result in differences in the dosimetric outcome.
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Age-dependent small-animal internal radiation dosimetry.
Molecular imaging, 2013Co-Authors: Tianwu Xie, Habib ZaidiAbstract:Rats at various ages were observed to present with different radiosensitivity and bioavailability for radiotracers commonly used in preclinical research. We evaluated the effect of age-induced changes in body weight on radiation dose calculations. A series of rat models at different age periods were constructed based on the realistic four-dimensional digital rat whole-body (ROBY) computational model. Particle transport was simulated using the MCNPX Monte Carlo code. Absorbed fractions (AFs) and specific absorbed fraction (SAFs) of monoenergetic photons/electrons and S values of eight Positron-Emitting Radionuclides were calculated. The SAFs and S values for most source-target pairs were inversely correlated with body weight. Differences between F-18 S values for most source-target pairs were between -1.5% and -2%/10 g difference in body weight for different computational models. For specific radiotracers, the radiation dose to organs presents a negative correlation with rat body weight. The SAFs for monoenergetic photons/electrons and S values for common Positron-Emitting Radionuclides can be exploited in the assessment of radiation dose delivered to rats at different ages and weights. The absorbed dose to organs is significantly higher in the low-weight young rat model than in the adult model, which would result in steep secondary effects and might be a noteworthy issue in laboratory animal internal dosimetry.
Martin W. Brechbiel - One of the best experts on this subject based on the ideXlab platform.
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mapping biological behaviors by application of longer lived Positron Emitting Radionuclides
Advanced Drug Delivery Reviews, 2013Co-Authors: Yang Zhou, Kwamena E Baidoo, Martin W. BrechbielAbstract:Abstract With the technological development of Positron emission tomography (PET) and the advent of novel antibody-directed drug delivery systems, longer-lived Positron-Emitting Radionuclides are moving to the forefront to take important roles in tracking the distribution of biotherapeutics such as antibodies, and for monitoring biological processes and responses. Longer half-life Radionuclides possess advantages of convenient on-site preparation procedures for both clinical and non-clinical applications. The suitability of the long half-life Radionuclides for imaging intact monoclonal antibodies (mAbs) and their respective fragments, which have inherently long biological half-lives, has attracted increased interest in recent years. In this review, we provide a survey of the recent literature as it applies to the development of nine-selected longer-lived Positron emitters with half-lives of 9–140 h (e.g., 124I, 64Cu, 86Y and 89Zr), and describe the biological behaviors of radionuclide-labeled mAbs with respect to distribution and targeting characteristics, potential toxicities, biological applications, and clinical translation potentials.
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Radioimmunoimaging with longer-lived Positron-Emitting Radionuclides: potentials and challenges.
Bioconjugate chemistry, 2009Co-Authors: Tapan K. Nayak, Martin W. BrechbielAbstract:Radioimmunoimaging and therapy has been an area of interest for several decades. Steady progress has been made toward clinical translation of radiolabeled monoclonal antibodies for diagnosis and treatment of diseases. Tremendous advances have been made in imaging technologies such as Positron emission tomography (PET). However, these advances have so far eluded routine translation into clinical radioimmunoimaging applications due to the mismatch between the short half-lives of routinely used Positron-Emitting Radionuclides such as (18)F versus the pharmacokinetics of most intact monoclonal antibodies of interest. The lack of suitable Positron-Emitting Radionuclides that match the pharmacokinetics of intact antibodies has generated interest in exploring the use of longer-lived Positron emitters that are more suitable for radioimmunoimaging and dosimetry applications with intact monoclonal antibodies. In this review, we examine the opportunities and challenges of radioimmunoimaging with select longer-lived Positron-Emitting Radionuclides such as (124)I, (89)Zr, and (86)Y with respect to radionuclide production, ease of radiolabeling intact antibodies, imaging characteristics, radiation dosimetry, and clinical translation potential.
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radioimmunoimaging with longer lived Positron Emitting Radionuclides potentials and challenges
Bioconjugate Chemistry, 2009Co-Authors: Tapan K. Nayak, Martin W. BrechbielAbstract:Radioimmunoimaging and therapy has been an area of interest for several decades. Steady progress has been made toward clinical translation of radiolabeled monoclonal antibodies for diagnosis and treatment of diseases. Tremendous advances have been made in imaging technologies such as Positron emission tomography (PET). However, these advances have so far eluded routine translation into clinical radioimmunoimaging applications due to the mismatch between the short half-lives of routinely used Positron-Emitting Radionuclides such as 18F versus the pharmacokinetics of most intact monoclonal antibodies of interest. The lack of suitable Positron-Emitting Radionuclides that match the pharmacokinetics of intact antibodies has generated interest in exploring the use of longer-lived Positron emitters that are more suitable for radioimmunoimaging and dosimetry applications with intact monoclonal antibodies. In this review, we examine the opportunities and challenges of radioimmunoimaging with select longer-lived po...
Michael J. Welch - One of the best experts on this subject based on the ideXlab platform.
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Positron-Emitting isotopes produced on biomedical cyclotrons.
Current medicinal chemistry, 2005Co-Authors: Paul Mcquade, Douglas J. Rowland, Jason S. Lewis, Michael J. WelchAbstract:This review will discuss the production and applications of Positron-Emitting Radionuclides for use in Positron Emission Tomography (PET), with emphasis on Radionuclides that can be produced onsite with a biomedical cyclotron. In PET the traditional Radionuclides of choice are 11C, 13N, 15O and 18F and although they will be briefly discussed in this article, the emphasis of this review will be on non-standard PET Radionuclides that are generating increased interest by the medical research community.
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Non-standard isotope production and applications at Washington University
AIP Conference Proceedings, 2001Co-Authors: Timothy J. Mccarthy, Deborah W. Mccarthy, Richard Laforest, Heather M. Bigott, Frank Wüst, David E. Reichert, Michael R. Lewis, Michael J. WelchAbstract:The Positron Emitting Radionuclides, oxygen-15, nitrogen-13, carbon-11, and fluorine-18 have been produced at Washington University for many years utilizing two biomedical cyclotrons; a Cyclotron Corporation CS15 and a Japan Steel Works 16/8 cyclotron. In recent years we have become interested in the production of non-standard PET isotopes. We were initially interested in copper-64 production using the 64Ni(p,n)64Cu nuclear reaction, but now apply this technique to other Positron Emitting copper isotopes, copper-60 and copper-61. Copper-64 is being produced routinely and made available to other institutions. In 1999 over ten Curies of copper-64 were produced, making copper available to thirteen institutions, as well as research groups at Washington University. We are currently developing methods for the routine productions of other PET radioisotopes of interest, these include; bromine-76, bromine-77, iodine-124, gallium-66, and technetium-94m.
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Metal Radionuclides for PET Imaging
Positron Emission Tomography, 1Co-Authors: Paul Mcquade, Deborah W. Mccarthy, Michael J. WelchAbstract:There are many possible metal-based Positron-Emitting Radionuclides that can be utilized in Positron tomography. At the present time, the most promising nuclides are copper, gallium, and yttrium. It is highly likely that radiopharmaceuticals labeled with these nuclides will be generally utilized in clinical practice over the next several years.
Raffaella Rossin - One of the best experts on this subject based on the ideXlab platform.
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Molecular imaging of cancer with radiolabeled peptides and PET.
Anti-cancer agents in medicinal chemistry, 2012Co-Authors: Amy L. Vāvere, Raffaella RossinAbstract:Radiolabeled peptides hold promise for diagnosis and therapy of cancer as well as for early monitoring of therapy outcomes, patient stratification, etc. This manuscript focuses on the development of peptides labeled with 18F, 64Cu, 68Ga and other Positron-Emitting Radionuclides for PET imaging. The major techniques for radionuclide incorporation are briefly discussed. Then, examples of Positron-Emitting peptides targeting somatostatin receptors, integrins, gastrin-releasing peptide receptors, vasointestinal peptide receptors, melanocortin 1 receptors and others are reviewed.
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Synthesis, in vitro and in vivo evaluation of radiolabeled nanoparticles.
The quarterly journal of nuclear medicine and molecular imaging : official publication of the Italian Association of Nuclear Medicine (AIMN) [and] the, 2008Co-Authors: Monica Shokeen, Raffaella RossinAbstract:Recent advances in the field of nanomedicine offer the promise of better diagnostic and therapeutic options. Synthetic chemists are making strides in developing nanoparticle constructs that can be used as platforms for attaching different functionalities for the purposes of molecular imaging and targeted drug delivery. As new nanoparticles are developed, it is imperative to evaluate their biological effectiveness by in vitro and in vivo screening techniques. While the in vitro results give insight into the cellular structure and function at sub-cellular level, the in vivo and ex vivo data give vital information about the pharmacokinetics of these novel particles, along with their ability to reach the desired target. This three-way information is pertinent to developing effective drugs and imaging probes for targeting key cancer/inflammation biomarkers such as the alphavbeta3 integrin. Labeling nanoparticles with Positron Emitting Radionuclides can speed up this evaluation. In fact, small animal Positron Emission Tomography (PET) scanners allow researchers to quantitatively image the uptake of candidate nanocarriers at the target site with high sensitivity. In addition to conventional ex vivo biodistribution techniques, the pharmacokinetic profile of new nanomaterials with potential medical application can be obtained with dynamic and/or longitudinal PET studies on a relatively small number of laboratory animals. This article will focus on some of the approaches to label nanoparticles with Positron Emitting Radionuclides along with in vitro and in vivo protocols that have been optimized and are being used for evaluating nanoparticles.