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- Juul, FE, et al.
(författare)
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Rates of repeated colonoscopies to clean the colon from low-risk and high-risk adenomas: results from the EPoS trials
- 2023
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Ingår i: Gut. - : BMJ. - 1468-3288 .- 0017-5749. ; 72:5, s. 951-957
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Tidskriftsartikel (refereegranskat)abstract
- High-quality colonoscopy (adequate bowel preparation, whole-colon visualisation and removal of all neoplastic polyps) is a prerequisite to start polyp surveillance, and is ideally achieved in one colonoscopy. In a large multinational polyp surveillance trial, we aimed to investigate clinical practice variation in number of colonoscopies needed to enrol patients with low-risk and high-risk adenomas in polyp surveillance.DesignWe retrieved data of all patients with low-risk adenomas (one or two tubular adenomas <10 mm with low-grade dysplasia) and high-risk adenomas (3–10 adenomas, ≥1 adenoma ≥10 mm, high-grade dysplasia or villous components) in the European Polyp Surveillance trials fulfilling certain logistic and methodologic criteria. We analysed variations in number of colonoscopies needed to achieve high-quality colonoscopy and enter polyp surveillance by endoscopy centre, and by endoscopists who enrolled ≥30 patients.ResultsThe study comprised 15 581 patients from 38 endoscopy centres in five European countries; 6794 patients had low-risk and 8787 had high-risk adenomas. 961 patients (6.2%, 95% CI 5.8% to 6.6%) underwent two or more colonoscopies before surveillance began; 101 (1.5%, 95% CI 1.2% to 1.8%) in the low-risk group and 860 (9.8%, 95% CI 9.2% to 10.4%) in the high-risk group. Main reasons were poor bowel preparation (21.3%) or incomplete colonoscopy/polypectomy (14.4%) or planned second procedure (27.8%). Need of repeat colonoscopy varied between study centres ranging from 0% to 11.8% in low-risk adenoma patients and from 0% to 63.9% in high-risk adenoma patients. On the second colonoscopy, the two most common reasons for a repeat (third) colonoscopy were piecemeal resection (26.5%) and unspecified reason (23.9%).ConclusionThere is considerable practice variation in the number of colonoscopies performed to achieve complete polyp removal, indicating need for targeted quality improvement to reduce patient burden.Trial registration numberNCT02319928.
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- Gebski, M., et al.
(författare)
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Ultra-thin VCSELs based on monolithic subwavelength high-index contrast surface gratings
- 2017
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Ingår i: 2016 IEEE Photonics Conference, IPC 2016. ; , s. 653-654
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Konferensbidrag (refereegranskat)abstract
- We present for the first time the measured power reflectance of GaAs monolithic high index contrast surface gratings (MHCGs) and computer simulations of various reduced-vertical-dimension VCSEL designs that employ these MHCG structures. We demonstrate the first optically-pumped MHCG DBR VCSELs with emission near 980 nm.
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- Reginski, K, et al.
(författare)
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Investigations of optical properties of active regions in vertical cavity surface emitting lasers grown by MBE
- 2002
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 412:1-2, s. 107-113
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Tidskriftsartikel (refereegranskat)abstract
- The design of the vertical cavity surface emitting lasers (VCSELs) needs proper tuning of many different optical parameters of those structures. So, the optimisation of the VCSELs requires deep understanding of optical processes occurring in the active regions of such lasers. In a series of MBE processes, active regions of VCSELs as well as the whole VCSELs were grown. The active regions of the VCSEL structures were designed for lambda = 1000 nm and 980 nm emission. They consisted of a pair of distributed Bragg reflectors (DBRs) composed of AlAs and GaAs quarter wavelength layers and a cavity made of GaAs. The cavities contained one or several quantum wells (QWs) made of In0.2Ga0.8As. To optimise the optical characteristics of the active regions, several experimental methods have been applied. The Bragg reflectors and the whole microcavities were investigated by optical reflectivity. For selective excitation of a QW in a cavity active layer, a Ti-sapphire tuneable laser has been used. The fine tuning between the QW emission and the cavity Fabry-Perot resonance has been investigated by photoluminescence at varying temperatures of the sample. For monitoring the temporal evolution of the luminescence from the active region of the laser, time-resolved spectroscopy has been employed. The combination of many methods of optical investigations enabled a comprehensive characterisation and as a result an optimisation of the whole laser structure. (C) 2002 Elsevier Science B.V. All rights reserved.
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- Wongmanerod, S, et al.
(författare)
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Many-body effects in highly p-type modulation-doped GaAs/AlxGa1-xAs quantum wells
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:4, s. 2794-2798
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Tidskriftsartikel (refereegranskat)abstract
- Many-body effects have been optically investigated for modulation-doped quantum wells at high acceptor densities. The observed band-gap shrinkage, up to approximate to 20 meV, is consistent with calculations based on the Hartree and random-phase approximations including the finite well width effect. A recombination near the Fermi edge with light-hole character is strikingly enhanced at high acceptor densities. An interpretation based on carrier-carrier interaction is proposed. Finally, the exciton is found to be quenched for hole densities higher than approximate to 2x10(12) cm(-2).
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