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Abstract
PURPOSE Renewed interest is being expressed in intravascular brachytherapy (IVBT). A number of unresolved issues exist in the discipline. Providing a homogeneous and adequate dose to the target remains difficult in IVBT. The guidewire that delivers the device to the target, arterial plaques, and stent struts are all known to reduce the dose delivered to target. The viability and efficacy of a proposed IVBT delivery system designed to resolve the issue of guidewire attenuation is evaluated and compared to that of a popular and commercially available IVBT device. METHODS AND MATERIALS Monte Carlo simulations are conducted to determine distributions of absorbed dose around an existing and proposed IVBT delivery system. RESULTS For the Novoste Beta-Cath 3.5F (TeamBest®), dose in water varies by 10% as a function of angle in the plane perpendicular to the delivery catheter due to off-centering of seeds in the catheter. Dose is reduced by 52% behind a stainless steel guidewire and 64% behind a guidewire, arterial plaque, and stent strut for the Novoste Beta-Cath 3.5F. Dose is not perturbed by the presence of a guidewire for the proposed device and is reduced by 46% by an arterial plaque and stent strut. CONCLUSIONS Dose attenuation by guidewire is likely the single greatest source of dose attenuation in IVBT in terms of absolute dose reduction and is greater than previously reported for the Novoste Beta-Cath 3.5F. The Novoste Beta-Cath 3.5F delivers an inhomogeneous dose to target. A delivery system is proposed, which resolves the issue of guidewire attenuation in IVBT and should reduce treatment times.
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Affiliation(s)
- Joseph M DeCunha
- Department of Physics, Medical Physics Unit, McGill University, Montreal, Quebec, Canada.
| | - Shirin A Enger
- Medical Physics Unit, Department of Oncology, Faculty of Medicine, McGill University, Montreal, Quebec, Canada; Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
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DeCunha J, Janicki C, Enger SA. A retrospective analysis of catheter-based sources in intravascular brachytherapy. Brachytherapy 2017; 16:586-596. [PMID: 28190783 DOI: 10.1016/j.brachy.2017.01.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 01/09/2017] [Accepted: 01/09/2017] [Indexed: 10/20/2022]
Abstract
PURPOSE Coronary artery disease involves the deposition of plaque along the walls of a coronary artery leading to narrowed or blocked vessels (stenosis) and is one of the main causes of death in developed countries. Percutaneous transluminal coronary angioplasty (PTCA) is used to reverse stenosis. Restenosis (renarrowing) of the treated vessel is a major complication of PTCA. A metal mesh tube (stent) can be placed inside the vessel to prevent restenosis. Tissue stress incurred during PTCA and stenting can provoke neointimal cell proliferation leading to in-stent restenosis (ISR). Intravascular brachytherapy (IVBT), a form of internal radiotherapy, is used to treat ISR. Renewed interest in IVBT is being expressed as a treatment for patients with ISR in drug-eluting stents. Current treatment planning (TP) of IVBT is extremely limited and assumes human tissue can be approximated by water. The interactions of arterial plaque, guidewires, and the stent have been shown to attenuate radiation significantly but are ignored in TP. Other models have determined the degree of attenuation by each factor in isolation. For the first time, we create a model with several inhomogenities present to determine whether attenuation by multiple inhomogenities combines linearly or if a larger dose reduction than anticipated is realized. We are also able to evaluate a spatial distribution of dose around the source and in arterial walls. METHODS AND MATERIALS A dosimetric analysis of two commercially available IVBT systems was performed in a Monte Carlo-based particle simulation (Geant4). Absorbed dose was calculated using a model of a human coronary artery with a calcified plaque and stent. Dose delivered in water was also calculated to evaluate the accuracy of a water approximation. RESULTS Dose as a function of θ shows significant variation around IVBT sources. For the Guidant Galileo, dose is reduced by 20% behind stent struts and as much as 66% in a region occluded by the guidewire, plaque, and stent. For the Novoste Beta Cath device, delivered dose is reduced by 19% and 58%, respectively, in the same regions. CONCLUSIONS Our findings show that the water approximation used in clinical practice to calculate dose is inaccurate when inhomogeneities are present. Methods proposed for calculating dose perturbations in IVBT may underestimate the magnitude of dose reduction. Increasing source dwell time seems unlikely to resolve dosimetric issues in IVBT. The effectiveness of currently existing β-emitting devices may be reduced in patients with complex lesions at the treatment site. Investigation of new radioisotopes and off-centering devices should be considered to improve dose outcomes.
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Affiliation(s)
- J DeCunha
- Department of Physics, Medical Physics Unit, McGill University, Montreal, Quebec, Canada.
| | - C Janicki
- Montreal Neurological Institute and Hospital, McGill University, Montreal, Quebec, Canada
| | - S A Enger
- Medical Physics Unit, Department of Oncology, Faculty of Medicine, McGill University, Montreal, Quebec, Canada; Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
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Satoh H, Tohno S, Minami T, Oishi T, Hayashi M, Tohno Y. Gender-related differences in a process of the age-dependent alterations of the elements in monkey sino-atrial node. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2010; 14:249-256. [PMID: 21165321 PMCID: PMC2997408 DOI: 10.4196/kjpp.2010.14.5.249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Revised: 08/02/2010] [Accepted: 09/05/2010] [Indexed: 05/30/2023]
Abstract
Gender differences in the trace elements of monkey sino-atrial (SA) node were investigated in a process of age-dependent alterations. Sixty hearts from Japanese and rhesus monkeys (30 male and 30 female) used were aged ranging from 1-day- to 30-year-old. The elements were analyzed using an inductively coupled plasma-atomic emission spectrometer (ICP-AES). Advancing age decreased all the trace elements. Ca, P, S and Mg significantly decreased. The correlation coefficients of Ca and P were -0.178±0.081 (p<0.05) and -0.088±0.022 (p<0.05) in male (n=30), and -0.095±0.026 (p<0.05) and -0.069±0.017 (p<0.05) in female (n=30), respectively. The age-dependent coefficients for Fe/Ca, Zn/Ca, Fe/P, Fe/S, Zn/S, Fe/Mg and Zn/Mg were exhibited markedly in male, but all was less in female. In gender-related differences, only a ratio of P/Ca (p<0.05) was significantly observed with ageing. The trace elements such as Cu, Se and Sn were less detected in the SA nodes. These results indicate that the age-dependent changes in the ratios of elements are appeared more rapidly in male monkey SA node, and the gender difference is observed in ratio of P/Ca. The different attenuations may be involved with the age- and gender-related SA nodal functions.
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Affiliation(s)
- Hiroyasu Satoh
- Department of Pharmacology, Division of Molecular and Cellular Biology, Kashihara, Nara University 634-8521, Japan
| | - Setsuko Tohno
- Department of Anatomy, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Takeshi Minami
- Laboratory of Environmental Biology, Department of Life Science, Faculty of Science and Engineering, Kinki University, Higashi-Osaka, Osaka 577-8502, Japan
| | - Takao Oishi
- Department of Cellular and Molecular Biology, Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan
| | - Motoharu Hayashi
- Department of Cellular and Molecular Biology, Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan
| | - Yoshiyuki Tohno
- Department of Anatomy, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
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Eidelman N, Boyde A, Bushby AJ, Howell PGT, Sun J, Newbury DE, Miller FW, Robey PG, Rider LG. Microstructure and mineral composition of dystrophic calcification associated with the idiopathic inflammatory myopathies. Arthritis Res Ther 2009; 11:R159. [PMID: 19857267 PMCID: PMC2787294 DOI: 10.1186/ar2841] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2009] [Revised: 09/17/2009] [Accepted: 10/26/2009] [Indexed: 11/29/2022] Open
Abstract
INTRODUCTION Calcified deposits (CDs) in skin and muscles are common in juvenile dermatomyositis (DM), and less frequent in adult DM. Limited information exists about the microstructure and composition of these deposits, and no information is available on their elemental composition and contents, mineral density (MD) and stiffness. We determined the microstructure, chemical composition, MD and stiffness of CDs obtained from DM patients. METHODS Surgically-removed calcinosis specimens were analyzed with fourier transform infrared microspectroscopy in reflectance mode (FTIR-RM) to map their spatial distribution and composition, and with scanning electron microscopy/silicon drift detector energy dispersive X-ray spectrometry (SEM/SDD-EDS) to obtain elemental maps. X-ray diffraction (XRD) identified their mineral structure, X-ray micro-computed tomography (microCT) mapped their internal structure and 3D distribution, quantitative backscattered electron (qBSE) imaging assessed their morphology and MD, nanoindentation measured their stiffness, and polarized light microscopy (PLM) evaluated the organic matrix composition. RESULTS Some specimens were composed of continuous carbonate apatite containing small amounts of proteins with a mineral to protein ratio much higher than in bone, and other specimens contained scattered agglomerates of various sizes with similar composition (FTIR-RM). Continuous or fragmented mineralization was present across the entire specimens (microCT). The apatite was much more crystallized than bone and dentin, and closer to enamel (XRD) and its calcium/phosphorous ratios were close to stoichiometric hydroxyapatite (SEM/SDD-EDS). The deposits also contained magnesium and sodium (SEM/SDD-EDS). The MD (qBSE) was closer to enamel than bone and dentin, as was the stiffness (nanoindentation) in the larger dense patches. Large mineralized areas were typically devoid of collagen; however, collagen was noted in some regions within the mineral or margins (PLM). qBSE, FTIR-RM and SEM/SDD-EDS maps suggest that the mineral is deposited first in a fragmented pattern followed by a wave of mineralization that incorporates these particles. Calcinosis masses with shorter duration appeared to have islands of mineralization, whereas longstanding deposits were solidly mineralized. CONCLUSIONS The properties of the mineral present in the calcinosis masses are closest to that of enamel, while clearly differing from bone. Calcium and phosphate, normally present in affected tissues, may have precipitated as carbonate apatite due to local loss of mineralization inhibitors.
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Affiliation(s)
- Naomi Eidelman
- Paffenbarger Research Center, American Dental Association Foundation, National Institute of Standards and Technology, 100 Bureau Drive, Stop 8546, Gaithersburg, MD 20899, USA
| | - Alan Boyde
- Biophysics OGD, Dental Institute, Queen Mary University of London, New Road, London E1 1BB, UK
| | - Andrew J Bushby
- Department of Materials, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Peter GT Howell
- Prosthetic Dentistry Unit, UCL Eastman Dental Institute, 256 Gray's Inn Road, London WC1X 8LD, UK
| | - Jirun Sun
- Polymers Division, National Institute of Standards and Technology, 100 Bureau Drive, Stop 8543, Gaithersburg, MD 20899, USA
- Current address: Paffenbarger Research Center, American Dental Association Foundation, National Institute of Standards and Technology, 100 Bureau Drive, Stop 8546, Gaithersburg, MD 20899, USA
| | - Dale E Newbury
- Surface and Microanalysis Science Division, National Institute of Standards and Technology, 100 Bureau Drive, Stop 8371, Gaithersburg, MD 20899, USA
| | - Frederick W Miller
- Environmental Autoimmunity Group, Office of Clinical Research, 10 Center Drive, MSC 1301, National Institute of Environmental Health Sciences, National Institutes of Health, Bethesda, MD 20892, USA
| | - Pamela G Robey
- National Institute of Dental and Craniofacial Research, National Institutes of Health, 30 Convent Drive, Bethesda, MD 20892, USA
| | - Lisa G Rider
- Environmental Autoimmunity Group, Office of Clinical Research, 10 Center Drive, MSC 1301, National Institute of Environmental Health Sciences, National Institutes of Health, Bethesda, MD 20892, USA
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