[Show abstract][Hide abstract] ABSTRACT: Background:
This study was designed to compare the quality assurance (QA) results of four dosimetric tools used for intensity modulated radiation therapy (IMRT) and to suggest universal criteria for the passing rate in QA, irrespective of the dosimetric tool used.
Materials and methods:
Thirty fields of IMRT plans from five patients were selected, followed by irradiation onto radiochromic film, a diode array (Mapcheck), an ion chamber array (MatriXX) and an electronic portal imaging device (EPID) for patient-specific QA. The measured doses from the four dosimetric tools were compared with the dose calculated by the treatment planning system. The passing rates of the four dosimetric tools were calculated using the gamma index method, using as criteria a dose difference of 3% and a distance-to-agreement of 3 mm.
The QA results based on Mapcheck, MatriXX and EPID showed good agreement, with average passing rates of 99.61%, 99.04% and 99.29%, respectively. However, the average passing rate based on film measurement was significantly lower, 95.88%. The average uncertainty (1 standard deviation) of passing rates for 6 intensity modulated fields was around 0.31 for film measurement, larger than those of the other three dosimetric tools.
QA results and consistencies depend on the choice of dosimetric tool. Universal passing rates should depend on the normalization or inter-comparisons of dosimetric tools if more than one dosimetric tool is used for patient specific QA.
Radiology and Oncology 09/2015; 49(3):307-13. DOI:10.1515/raon-2015-0021 · 1.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Prestressed concrete (PSC) is one of the most reliable, durable and widely used construction materials, which overcomes the weakness of concrete in tension by the introduction of a prestress force. Smart strands enabling measurement of the prestress force have recently been developed to maintain PSC structures throughout their lifetime. However, the smart strand cannot give a representative indication of the whole prestress force when used in multi-strand systems since each strand sustains a different prestress force. In this paper, the actual distribution of the prestress force in a multi-strand system is examined using elastomagnetic (EM) sensors to develop a method for tracking representative indicators of the prestress force using smart strands.
[Show abstract][Hide abstract] ABSTRACT: We develop a regenerable anti-fouling membrane via the formation of a dynamic peel-and-stick of hydrophilic poly(ethylene glycol) (PEG) layer onto the surface of a poly(tetrafluoroethylene) (PTFE) membrane, using thermo-responsive reversible covalent bonding. In order to attach a peelable-and-stickable hydrophlilic layer onto a membrane surface, a maleimide end-modified PEG layer is coupled with a furan-modified PTFE membrane by reversible Diels–Alder (DA) cycloaddition reaction. The combined results of attenuated total reflection Fourier-transform infrared (ATR FT-IR), X-ray photoelectron spectroscopy (XPS) and field-emission scanning electron microscopy (FE-SEM) measurements clearly reveal that the maleimide end-modified PEG is successfully coupled with the furan-modified PTFE membrane surface by DA reaction. In addition, the hydrophilic PEG layer is readily and repeatedly reformed on the membrane surface by a thermally driven dynamic peel-and-stick process. The PEG-coupled PTFE membrane shows effective anti-fouling performance against a highly concentrated silica colloidal aqueous solution. In particular, the anti-fouling property is remarkably recovered after regeneration of the hydrophilic layer through the peel-and-stick process.
[Show abstract][Hide abstract] ABSTRACT: We develop an anti-scaling ultrafiltration/microfiltration (UF/MF) membrane by introducing a high-density positive charge to a poly(vinylidene fluoride) (PVDF) membrane to suppress membrane scaling in Ca2+/silica-rich wastewater. Positively charged modifiers are synthesized by conjugating an amphiphilic polymer (Brij S10) and branched poly(ethylene imine) (b-PEI) at various molar ratios, and these are then implanted to PVDF membranes during the phase-inversion process. Attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectra reveal that the positive modifiers successfully anchors onto the surface of the membrane by hydrophilic-hydrophobic phase recognition. As introducing the positive charge on the membrane surface, the membranes show positive surface charge and their pure water permeability (PWP) increases due to the protonation of b-PEI. Anti-scaling properties are also confirmed to be improved by filtration tests using a metal ions/silica-rich feed solution, which results from the repulsion of metal ion by the positively charged branch on the membrane. In addition, the water flux recovery by simple membrane backwashing of the modified membrane is double that of the neat PVDF membrane.
[Show abstract][Hide abstract] ABSTRACT: Prestressed Concrete Wire and Strand (PC) strands are the most used materials to introduce prestress in a Pre-Stressed Concrete (PSC) structure. However, it is difficult to evaluate the final prestress force of the PC strand after prestressing or its residual prestress force after completion of the structure on site. This impossibility to assess eventual loss of prestress of the PC strand has resulted in a number of serious accidents and even in the collapse of several structures. This situation stresses the necessity to maintain the prestress force residual or after prestressing for the evaluation of the health of the concrete structure throughout its lifespan. Recently, several researchers have studied methods enabling one to verify the prestress force by inserting an optical fiber sensor inside the strand but failed to provide simple techniques for the fabrication of these devices to fulfill measurement performance from the design prestress to failure. Moreover, these methods require the additional installation of electrical resistance strain gages, displacement sensors and load cells on the outer surface of the structure for long-term precise measurement. This paper proposes a method enabling one to evaluate precisely and effectively the prestress force of the PC strand and intends to verify the applicability of the proposed method on actual concrete structures. To that end, an innovative PC strand is developed by embedding a Fiber Bragg Grating (FBG) sensor in the core wire of the PC strand so as to enable short term as well as long term monitoring. The measurement performance of the developed strand is then evaluated experimentally and the reliability of the monitoring data is assessed.
[Show abstract][Hide abstract] ABSTRACT: Conventional laser accelerated proton beam has broad energy spectra. It is not suitable for clinical use directly, so it is necessary for employing energy selection system. However, in the conventional laser accelerated proton system, the intensity of the proton beams in the low energy regime is higher than that in the high energy regime. Thus, to generate spread-out-Bragg peak (SOBP), stronger weighting value to the higher energy proton beams is needed and weaker weighting value to the lower energy proton beams is needed, which results in the wide range of weighting values. The purpose of this research is to investigate a method for efficient generating of the SOBP with varying magnetic field in the energy selection system using a carbon-proton mixture target. Energy spectrum of the laser accelerated proton beams was acquired using Particle-In-Cell simulations. The Geant4 Monte Carlo simulation toolkit was implemented for energy selection, particle transportation, and dosimetric property measurement. The energy selection collimator hole size of the energy selection system was changed from 1 to 5 mm in order to investigate the effect of hole size on the dosimetric properties for Bragg peak and SOBP. To generate SOBP, magnetic field in the energy selection system was changed during beam irradiation with each beam weighting factor. In this study, our results suggest that carbon-proton mixture target based laser accelerated proton beams can generate quasi-monoenergetic energy distribution and result in the efficient generation of SOBP. A further research is needed to optimize SOBP according to each range and modulated width using an optimized weighting algorithm.
Australasian physical & engineering sciences in medicine / supported by the Australasian College of Physical Scientists in Medicine and the Australasian Association of Physical Sciences in Medicine 08/2014; 37(4). DOI:10.1007/s13246-014-0292-7 · 0.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper, the results of basic tests conducted to evaluate the flexural behavior of lap-spliced joints that exploit the remarkable bonding performance of ultra-high performance concrete (UHPC) are presented. The effects of varying the lap-spliced length and joint length on the flexural behavior of the test members were examined. The failure pattern, load–deflection relationship, and load–strain relationship obtained by the static loading test were then analyzed with respect to the details of the joints. The results suggest lower bounds for the major test variables. A modified model, which considers the bonding performance of UHPC at the joint interface and the yield behavior of the reinforcement, is suggested on the basis of analytical models proposed for UHPC sections in previous studies. The corresponding results for this model are then compared with the test results.
Canadian Journal of Civil Engineering 07/2014; 41(7). DOI:10.1139/cjce-2013-0281 · 0.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose
We evaluated the glass dosimeter suitability as an external audit program in proton therapy beam. A feasibility test of the glass dosimeter postal dose intercomparison was performed for high-energy proton beam use in radiation oncology with the collaboration of five proton therapy centers (Shizuoka Cancer Center, University of Florida Proton Center, MD Anderson Cancer Center, Loma Linda University Medical Center, and University of Pennsylvania School of Medicine).
Material and methods
The dosimetric properties of a GD-301 glass dosimeter were investigated for its potential use for postal dosimetry. Measurements were performed in a water phantom using a stair-like holder specially designed for this study. The depth-dose distribution measured with the glass dosimeter was compared to those from GEANT4 Monte-Carlo simulation. The GEANT4 code was also used to simulate the influence of holder material in the absorbed dose by inserting the glass dosimeter in a water phantom within the stair-like holder. We investigated the methodology of the absorbed dose determination with the glass dosimeter system establishing the calibration factor and various correction factors (non-linearity, fading, energy, holder). The participating proton therapy centers were asked to irradiate the glass dosimeter to 2 Gy with similar setup and conditions.
The repeatability and dose rate dependence is within 1.2% and 1.5%, respectively. Depth-dose distributions in the pristine Bragg curve and the spread-out Bragg curve were estimated to be within 3%, compared with depth-dose measured with the ionization chamber. The difference in absorbed dose between the glass dosimeter and ionization chamber was within ±2% as a function of proton beam quality, residual ranges were between 2.1 and 9.0 cm. The influence of the holder material in absorbed doses of the proton beams is less than 1%. In the accuracy evaluation of the glass dosimeter system established in blind test, we obtained within 2.5% agreements with the ionization chamber dosimetry for the proton beam. In this feasibility study, the results on the proton beam output check are relatively good within ±6% for all participating centers.
We believe that the glass dosimeter system has considerable potential to be used for a postal dose audit program in proton beam.
[Show abstract][Hide abstract] ABSTRACT: One-lung ventilation (OLV) is accomplished with a double-lumen tube (DLT) or a bronchial blocker (BB). The authors compared the effectiveness of lung collapse using DLT, BB, and BB with the disconnection technique.
Prospective, randomized, blind trial.
A university hospital.
Fifty-two patients undergoing elective pneumothorax surgery.
Patients were assigned randomly to 1 of 3 groups: The DLT group (group 1), the BB group (group 2), and the BB with the disconnection technique group (group 3). The authors modified the disconnection technique in group 3 as follows: (1) turned off the ventilator and opened the adjustable pressure-limiting valve, allowing both lungs to collapse and (2) after loss of the CO2 trace on the capnograph, inflated the blocker cuff and turned on the ventilator, allowing only dependent-lung ventilation.
Five and ten minutes after OLV, the degree of lung collapse was assessed by the surgeon, who was blinded to the isolation technique. The quality of lung collapse at 5 and 10 minutes was significantly better in groups 1 and 3 than in group 2. No significant differences were observed for the degree of lung collapse at any time point between groups 1 and 3. The average time for loss of the CO2 trace on the capnograph was 32.3±7.0 seconds in group 3.
A BB with spontaneous collapse took longer to deflate and did not provide equivalent surgical exposure to the DLT. The disconnection technique could be helpful to accelerate lung collapse with a BB.
Journal of cardiothoracic and vascular anesthesia 11/2013; 28(4). DOI:10.1053/j.jvca.2013.07.019 · 1.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We develop a sustainable anti-biofouling ultrafiltration membrane nanocomposites by covalently immobilizing silver nanoparticles (AgNPs) onto poly(vinylidene fluoride) (PVDF) membrane mediated by a thiol-end functional amphiphilic block copolymer linker. Field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDXS) measurements reveal that the AgNPs are highly bound and dispersed to the PVDF membrane due to the strong affinity of the AgNPs with the thiol-modified block copolymeric linkers, which have been anchored to the PVDF membrane. The membrane performs well under water permeability and particle rejection measurements, despite the high deposition of AgNPs on the surface of membrane. The Ag-PVDF membrane nanocomposite significantly inhibits the growth of bacteria on the membrane surface, resulting in enhanced anti-biofouling property. Importantly, the AgNPs are not released from the membrane surface due to the robust covalent bond between the AgNPs and the thiolated PVDF membrane. The stability of the membrane nanocomposite ensures a sustainable anti-biofouling activity of the membrane.
[Show abstract][Hide abstract] ABSTRACT: The aim of this work was to study the feasibility of proton radiography (pRad) as a patient-specific range compensator (RC) quality assurance (QA) tool and to validate its clinical utility by performing QA on RCs having three kinds of possible defects. In order to achieve pRad for a single EBT film, proton beam currents were modulated with new weighting factors, maximizing the linearity of optical-density-to-thickness ratio. Two RCs, examined to be accurately manufactured as planned, were selected to estimate the feasibility of our pRad. The optical densities of the EBT film on which the RC was irradiated with the modulated proton beam were digitized to pixel values (pv) and then converted to thickness using a thickness-pv calibration curve. The thickness information on the pRad was compared with plan data that had been extracted from treatment planning system. The mean thickness difference (TD) over the flat RC regions was calculated as 0.39 mm, and the standard deviation as 0.22 mm, and the proton scattering effect was analyzed by step phantom measurement. Even proton scattering effected a TD of over 1 mm in the large gradient region, the percentage of pixels over the acceptance criterion was only within 1.11% and 3.49%, respectively, when a 1 mm distance to agreement tolerance limit was applied. The QA results for both precisely and imprecisely manufactured RCs demonstrated the high potential utility and clinical applicability of the pRad-based RC QA tool.
Physics in Medicine and Biology 09/2013; 58(18):6511-6523. DOI:10.1088/0031-9155/58/18/6511 · 2.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Korea Institute of Construction Technology has developed a precast FRP-concrete composite deck to be applied to cable-stayed bridges. This deck is a precast structural system in which concrete is disposed at the upper part and a hollow FRP tube is disposed at the bottom to play the role of tensile reinforcement and form. This paper presents the prototype of the so-developed FRP-concrete composite deck fabricated for trial construction. Electrical resistance sensors and optical fiber sensors were installed on the prototype to evaluate its structural stability and serviceability during the 17 months of operation through a series of field loading tests. From the field loading test results, the FRP-concrete composite deck was verified to secure sufficient structural stability and serviceability along the 17 months of operation even after the repeated passage of the heavy construction trucks. Besides, it appeared also that, for long-term monitoring, the optical fiber sensor provided more reliable measurement than the electrical resistance sensor glued to the structure.
[Show abstract][Hide abstract] ABSTRACT: To investigate the accuracy of Eclipse treatment planning system (TPS) dose calculations at the surface. It is desirable to know the accuracy of the proton treatment planning system in predicting dose at superficial region. All measurements were performed in a clinical proton beam at the National Cancer Center in Korea. Proton treatment plans were developed for a superficial planning target volume (PTV) contoured on a cylindrical polymethylmethacrylate phantom specially designed for this study. Dose was then measured at the surface and also in the PTV for these treatment plans and compared against the TPS calculations. For our study, a model GD-301 glass dosimeters were used. The proton treatment planning system overestimated the superficial dose without use of bolus as much as by 7–14% when compared to glass dosimeter. On the other hand, with use of bolus to cover the superficial region, surface dose between the calculation from Eclipse and measurement using the glass dosimeter are approximately within 3%.
[Show abstract][Hide abstract] ABSTRACT: PURPOSE: To evaluate the retinal thickness and volume measured with the enhanced depth imaging (EDI) method compared with those measured with the conventional method using spectral-domain optical coherence tomography (OCT). DESIGN: Retrospective, observational, case-control study. METHODS: Clinical records of 20 healthy subjects and those of 35 patients with chorioretinopathy (central serous chorioretinopathy, polypoidal choroidal vasculopathy, Vogt-Koyanagi-Harada disease, and reticular pseudodrusen) were analyzed retrospectively. All subjects underwent spectral-domain OCT using both the conventional and the EDI OCT raster scan protocols. The raster scan was composed of 31 B-scans that were 9.0 mm in length and 240 μm apart. Retinal thickness and volume of 9 Early Treatment Diabetic Retinopathy Study subfields were investigated. Intraclass correlation coefficients, Bland-Altman plots, and Wilcoxon signed-rank test results were used for the analysis. RESULTS: Sixty-five eyes of 35 patients with chorioretinal diseases and 40 eyes of 20 normal healthy subjects were evaluated. The automatically measured retinal thickness and volume of 9 Early Treatment Diabetic Retinopathy Study subfields with conventional and EDI raster scan showed an intraclass correlation coefficient of 0.861 to 0.995 and 0.873 to 0.995, respectively. The 95% limits of agreement between the 2 protocols in the measurement of central subfield were -14.52 to 12.88 μm in retinal thickness and -0.014 to 0.013 mm(3) in retinal volume. The differences of segmentation error rate between the 2 protocols were statistically insignificant (P > .05), except in eyes with reticular pseudodrusen in the subgroup analysis (P = .006). No significant differences were observed in measured values between healthy eyes and unaffected fellow eyes. CONCLUSIONS: The EDI OCT raster scan showed high agreement with conventional OCT in the measurement of retinal thickness and volume and could be used to evaluate both the retina and choroid in normal eyes and in eyes with some forms of chorioretinal disorder.
American Journal of Ophthalmology 06/2013; 156(3). DOI:10.1016/j.ajo.2013.04.027 · 3.87 Impact Factor