| 1. |
- Carlsson Tedgren, Åsa, et al.
(author)
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Comparison of high-dose-rate Ir-192 source strength measurements using equipment with traceability to different standards
- 2014
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In: Brachytherapy. - : Elsevier. - 1538-4721 .- 1873-1449. ; 13:4, s. 420-423
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Journal article (peer-reviewed)abstract
- PURPOSE:According to the American Association of Physicists in Medicine Task Group No. 43 (TG-43) formalism used for dose calculation in brachytherapy treatment planning systems, the absolute level of absorbed dose is determined through coupling with the measurable quantity air-kerma strength or the numerically equal reference air-kerma rate (RAKR). Traceability to established standards is important for accurate dosimetry in laying the ground for reliable comparisons of results and safety in adoption of new treatment protocols. The purpose of this work was to compare the source strength for a high-dose rate (HDR) (192)Ir source as measured using equipment traceable to different standard laboratories in Europe and the United States.METHODS AND MATERIALS:Source strength was determined for one HDR (192)Ir source using four independent systems, all with traceability to different primary or interim standards in the United States and Europe.RESULTS:The measured HDR (192)Ir source strengths varied by 0.8% and differed on average from the vendor value by 0.3%. Measurements with the well chambers were 0.5% ± 0.1% higher than the vendor-provided source strength. Measurements with the Farmer chamber were 0.7% lower than the average well chamber results and 0.2% lower than the vendor-provided source strength. All of these results were less than the reported source calibration uncertainties (k=2) of each measurement system.CONCLUSIONS:In view of the uncertainties in ion chamber calibration factors, the maximum difference in source strength found in this study is small and confirms the consistency between calibration standards in use for HDR (192)Ir brachytherapy.
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| 2. |
- Dohlmar, Frida, et al.
(author)
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Validation of automated post-adjustments of HDR prostate brachytherapy treatment plans by quantitative measures and oncologist observer study
- 2023
-
In: Brachytherapy. - : Elsevier BV. - 1538-4721 .- 1873-1449. ; 22:3, s. 407-415
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Journal article (peer-reviewed)abstract
- PURPOSE: The aim was to evaluate a postprocessing optimization algorithm's ability to improve the spatial properties of a clinical treatment plan while preserving the target coverage and the dose to the organs at risk. The goal was to obtain a more homogenous treatment plan, minimizing the need for manual adjustments after inverse treatment planning. MATERIALS AND METHODS: The study included 25 previously treated prostate cancer pa-tients. The treatment plans were evaluated on dose-volume histogram parameters established clin-ical and quantitative measures of the high dose volumes. The volumes of the four largest hot spots were compared and complemented with a human observer study with visual grading by eight oncologists. Statistical analysis was done using ordinal logistic regression. Weighted kappa and Fleiss' kappa were used to evaluate intra-and interobserver reliability. RESULTS: The quantitative analysis showed that there was no change in planning target volume (PTV) coverage and dose to the rectum. There were significant improvements for the adjusted treatment plan in: V150% and V200% for PTV, dose to urethra, conformal index, and dose nonhomogeneity ratio. The three largest hot spots for the adjusted treatment plan were significantly smaller compared to the clinical treatment plan. The observers preferred the adjusted treatment plan in 132 cases and the clinical in 83 cases. The observers preferred the adjusted treatment plan on homogeneity and organs at risk but preferred the clinical plan on PTV coverage. CONCLUSIONS: Quantitative analysis showed that the postadjustment optimization tool could improve the spatial properties of the treatment plans while maintaining the target coverage.
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| 3. |
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| 4. |
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| 5. |
- Karlsson, Johannes, et al.
(author)
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Differences in outcome for cervical cancer patients treated with or without brachytherapy
- 2017
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In: Brachytherapy. - Philadelphia, USA : Elsevier. - 1538-4721 .- 1873-1449. ; 16:1, s. 133-140
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Journal article (peer-reviewed)abstract
- Purpose: To compare the clinical outcome of cervical cancer patients treated with primary radiotherapy with and without the addition of brachytherapy.Methods and Materials: In all, 220 patients with cervical cancer stage I-IV treated between 1993 and 2009 were included. Three or five 6.0 Gy fractions of brachytherapy were given in addition to the external beam radiotherapy to 134 patients, whereas 86 patients received external beam radiotherapy alone (EBRTA). In the EBRTA group, the patients received external boost instead of brachytherapy with a total dose to the tumor of 64-72 Gy.Results: The 5-year overall survival and cancer-specific survival rates of the complete series were 42.5% and 55.5%, respectively. The rates of primary complete remission, 5-year cancer-specific survival, and recurrence were 92.5%, 68.5%, and 31.3% for the brachytherapy group vs. 73.3%, 35.4%, and 37.2% for the EBRTA group. The survival (all types) of the patients receiving brachytherapy was significantly (p < 0.0001) better than for the patients treated with external boost, but the difference was most pronounced in FIGO stage II tumors. Higher FIGO stage, nonsquamous cell carcinoma histology, treatment with EBRTA, and lower total equal 2-Gy (EQD2) external dose were significantly associated with poorer survival, lower rate of remission, and higher recurrence rate in multivariate models.Conclusions: Primary tumor remission rate, recurrence rate, and all types of survival rates were improved in the brachytherapy group. Brachytherapy is important to achieve sufficient doses to the periphery and central part of the tumor and should always be considered in treatment of cervical carcinomas.
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| 6. |
- Karlsson, Mattias, et al.
(author)
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Monte Carlo dosimetry of the eye plaque design used at the St. Erik Eye Hospital for I-125 brachytherapy
- 2014
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In: Brachytherapy. - : Elsevier. - 1538-4721 .- 1873-1449. ; 13:6, s. 651-656
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Journal article (peer-reviewed)abstract
- PURPOSE: At St. Erik Eye Hospital in Stockholm, Sweden, ocular tumors of apical height above 6 mm are treated with brachytherapy, using iodine-125 seeds attached to a gold alloy plaque while the treatment planning is performed assuming homogeneous water surroundings. The aim of this work was to investigate the dose-modifying effects of the plaque and the seed fixating silicone rubber glue. METHODS AND MATERIALS: The impact of the gold plaque and silicone rubber glue was studied with the Monte Carlo N-particle transport code, version 5. RESULTS: For the 2 cm most proximal to the plaque surface along the plaques central axis, the eyeball received 104.6-93.0% of the dose in all-water conditions. CONCLUSIONS: The 0.3 mm thick layer of silicone rubber glue, used for seed fixation, attenuates photons little enough to allow characteristic X-rays from the gold alloy plaque to reach the eyeball. Close to the plaque, the dose rates were higher with the plaque and glue present, than in homogeneous water conditions. This is in contrast to what has been reported for more commonly used eye plaques, demonstrating the importance of investigating the dosimetry of individual treatment systems.
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| 7. |
- Persson, Maria, et al.
(author)
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Experience of using MOSFET detectors for dose verification measurements in an end-to-end Ir-192 brachytherapy quality assurance system
- 2018
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In: Brachytherapy. - : ELSEVIER SCIENCE INC. - 1538-4721 .- 1873-1449. ; 17:1, s. 227-233
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Journal article (peer-reviewed)abstract
- PURPOSE: Establishment of an end-to-end system for the brachytherapy (BT) dosimetric chain could be valuable in clinical quality assurance. Here, the development of such a system using MOSFET (metal oxide semiconductor field effect transistor) detectors and experience gained during 2 years of use are reported with focus on the performance of the MOSFET detectors. METHODS AND MATERIALS: A bolus phantom was constructed with two implants, mimicking prostate and head amp; neck treatments, using steel needles and plastic catheters to guide the Ir-192 source and house the MOSFET detectors. The phantom was taken through the BT treatment chain from image acquisition to dose evaluation. During the 2-year evaluation-period, delivered doses were verified a total of 56 times using MOSFET detectors which had been calibrated in an external Co-60 beam. An initial experimental investigation on beam quality differences between Ir-192 and Co-60 is reported. RESULTS: The standard deviation in repeated MOSFET measurements was below 3% in the six measurement points with dose levels above 2 Gy. MOSFET measurements overestimated treatment planning system doses by 2-7%. Distance-dependent experimental beam quality correction factors derived in a phantom of similar size as that used for end-to-end tests applied on a time-resolved measurement improved the agreement. CONCLUSIONS: MOSFET detectors provide values stable over time and function well for use as detectors for end-to-end quality assurance purposes in 192Ir BT. Beam quality correction factors should address not only distance from source but also phantom dimensions. (C) 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.
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| 8. |
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| 9. |
- Adamowicz, Tomasz, et al.
(author)
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Regularity of p(.)-superharmonic functions, the Kellogg property and semiregular boundary points
- 2014
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In: Annales de l'Institut Henri Poincare. Analyse non linéar. - : Elsevier Masson / Institute Henri Poincar�. - 0294-1449 .- 1873-1430. ; 31:6, s. 1131-1153
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Journal article (peer-reviewed)abstract
- We study various boundary and inner regularity questions for p(.)-(super)harmonic functions in Euclidean domains. In particular, we prove the Kellogg property and introduce a classification of boundary points for p(.)-harmonic functions into three disjoint classes: regular, semiregular and strongly irregular points. Regular and especially semiregular points are characterized in many ways. The discussion is illustrated by examples. Along the way, we present a removability result for bounded p(.)-harmonic functions and give some new characterizations of W-0(1,p(.)) spaces. We also show that p(.)-superharmonic functions are lower semicontinuously regularized, and characterize them in terms of lower semicontinuously regularized supersolutions.
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| 10. |
- Aleksanyan, Gohar, 1987-
(author)
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Optimal regularity in the optimal switching problem
- 2016
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In: Annales de l'Institut Henri Poincare. Analyse non linéar. - : Elsevier. - 0294-1449 .- 1873-1430. ; 33:6, s. 1455-1471
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Journal article (peer-reviewed)abstract
- In this article we study the optimal regularity for solutions to the following weakly coupled system with interconnected obstacles{min(−Δu1+f1,u1−u2+ψ1)=0min(−Δu2+f2,u2−u1+ψ2)=0 arising in the optimal switching problem with two modes. We derive the optimal C1,1-regularity for the minimal solution under the assumption that the zero loop set L:={ψ1+ψ2=0} is the closure of its interior. This result is optimal and we provide a counterexample showing that the C1,1-regularity does not hold without the assumption L=L0‾.
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| 11. |
- Allen, Mark, et al.
(author)
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The inhomogeneous boundary Harnack principle for fully nonlinear and p-Laplace equations
- 2023
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In: Annales de l'Institut Henri Poincare. Analyse non linéar. - : European Mathematical Society - EMS - Publishing House GmbH. - 0294-1449 .- 1873-1430. ; 40:1, s. 133-156
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Journal article (peer-reviewed)abstract
- We prove a boundary Harnack principle in Lipschitz domains with small constant for fully nonlinear and p-Laplace-type equations with a right-hand side, as well as for the Laplace equa-tion on nontangentially accessible domains under extra conditions. The approach is completely new and gives a systematic approach for proving similar results for a variety of equations and geometries.
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| 12. |
- Alvino, Angelo, et al.
(author)
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Well-posed elliptic Neumann problems involving irregular data and domains
- 2010
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In: ANNALES DE L INSTITUT HENRI POINCARE-ANALYSE NON LINEAIRE. - : GAUTHIER-VILLARS/EDITIONS ELSEVIER, 23 RUE LINOIS, 75015 PARIS, FRANCE. - 0294-1449 .- 1873-1430. ; 27:4, s. 1017-1054
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Journal article (peer-reviewed)abstract
- Non-linear elliptic Neumann problems, possibly in irregular domains and with data affected by low integrability properties, are taken into account. Existence, uniqueness and continuous dependence on the data of generalized solutions are established under a suitable balance between the integrability of the datum and the (ir)regularity of the domain. The latter is described in terms of isocapacitary inequalities. Applications to various classes of domains are also presented. (C) 2010 Elsevier Masson SAS. All rights reserved.
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| 13. |
- Benedicks, Michael, et al.
(author)
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Random perturbations and statistical properties of Henon-like maps
- 2006
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In: Annales de l'Institut Henri Poincare. Analyse non linéar. - : European Mathematical Society - EMS - Publishing House GmbH. - 0294-1449 .- 1873-1430. ; 23:5, s. 713-752
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Journal article (peer-reviewed)abstract
- For a large class of non-uniformly hyperbolic diffeomorphisms, we prove stochastic stability under small random noise: the unique stationary probability measure of the Markov chain converges to the Sinai-Ruelle-Bowen measure of the unperturbed attractor when the noise level tends to zero.
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| 14. |
- Björn, Anders, et al.
(author)
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BMO, integrability, Harnack and Caccioppoli inequalities for quasiminimizers
- 2010
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In: ANNALES DE L INSTITUT HENRI POINCARE-ANALYSE NON LINEAIRE. - : GAUTHIER-VILLARS/EDITIONS ELSEVIER, 23 RUE LINOIS, 75015 PARIS, FRANCE. - 0294-1449 .- 1873-1430. ; 27:6, s. 1489-1505
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Journal article (peer-reviewed)abstract
- In this paper we use quasiminimizing properties of radial power-type functions to deduce counterexamples to certain Caccioppoli type inequalities and weak Harnack inequalities for quasisuperharmonic functions both of which are well known to hold for p-superharmonic functions We also obtain new bounds on the local integrability for quasisuperharmonic functions Furthermore we show that the logarithm of a positive quasisuperminimizer has bounded mean oscillation and belongs to a Sobolev type space
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| 15. |
- Bona, J L, et al.
(author)
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Algebraic lower bounds for the uniform radius of spatial analyticity for the generalized KdV equation
- 2005
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In: Annales de L'Institut Henri Poincaré. - : European Mathematical Society - EMS - Publishing House GmbH. - 0294-1449. ; 22:6, s. 783-797
-
Journal article (peer-reviewed)abstract
- The generalized Korteweg-de Vries equation has the property that solutions with initial data that are analytic in a strip in the complex plane continue to be analytic in a strip as time progresses. Established here are algebraic lower bounds on the possible rate of decrease in time of the uniform radius of spatial analyticity for these equations. Previously known results featured exponentially decreasing bounds.
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| 16. |
- Ehrnström, Mats, et al.
(author)
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On Whitham's conjecture of a highest cusped wave for a nonlocal dispersive equation
- 2019
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In: Annales de l'Institut Henri Poincare (C) Analyse Non Lineaire. - : European Mathematical Society - EMS - Publishing House GmbH. - 0294-1449 .- 1873-1430. ; 36:6, s. 1603-1637
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Journal article (peer-reviewed)abstract
- We consider the Whitham equation u t +2uu x +Lu x =0, where L is the nonlocal Fourier multiplier operator given by the symbol m(ξ)=tanhξ/ξ. G. B. Whitham conjectured that for this equation there would be a highest, cusped, travelling-wave solution. We find this wave as a limiting case at the end of the main bifurcation curve of P-periodic solutions, and give several qualitative properties of it, including its optimal C 1/2 -regularity. An essential part of the proof consists in an analysis of the integral kernel corresponding to the symbol m(ξ), and a following study of the highest wave. In particular, we show that the integral kernel corresponding to the symbol m(ξ) is completely monotone, and provide an explicit representation formula for it. Our methods may be generalised.
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| 17. |
- Helsing, Johan, et al.
(author)
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Classification of spectra of the Neumann–Poincaré operator on planar domains with corners by resonance
- 2017
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In: Annales de l'Institut Henri Poincare. Annales: Analyse Non Lineaire/Nonlinear Analysis. - : European Mathematical Society - EMS - Publishing House GmbH. - 0294-1449 .- 1873-1430. ; 34:4, s. 991-1011
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Journal article (peer-reviewed)abstract
- We study spectral properties of the Neumann–Poincaré operator on planar domains with corners with particular emphasis on existence of continuous spectrum and pure point spectrum. We show that the rate of resonance at continuous spectrum is different from that at eigenvalues, and then derive a method to distinguish continuous spectrum from eigenvalues. We perform computational experiments using the method to see whether continuous spectrum and pure point spectrum appear on domains with corners. For the computations we use a modification of the Nyström method which makes it possible to construct high-order convergent discretizations of the Neumann–Poincaré operator on domains with corners. The results of experiments show that all three possible spectra, absolutely continuous spectrum, singularly continuous spectrum, and pure point spectrum, may appear depending on domains. We also prove rigorously two properties of spectrum which are suggested by numerical experiments: symmetry of spectrum (including continuous spectrum), and existence of eigenvalues on rectangles of high aspect ratio.
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| 18. |
- Indrei, E., et al.
(author)
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Regularity of solutions to fully nonlinear elliptic and parabolic free boundary problems
- 2016
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In: Annales de l'Institut Henri Poincare. Analyse non linéar. - : Elsevier. - 0294-1449 .- 1873-1430. ; 33:5, s. 1259-1277
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Journal article (peer-reviewed)abstract
- We consider fully nonlinear obstacle-type problems of the form. F(D2u,x)=f(x)a.e. in B1∩Ω,|D2u|≤Ka.e. in B1\Ω, where Ω is an open set and K>0. In particular, structural conditions on F are presented which ensure that W2,n(B1) solutions achieve the optimal C1,1(B1/2) regularity when f is Hölder continuous. Moreover, if f is positive on B-1, Lipschitz continuous, and u≠0⊂Ω, we obtain interior C1 regularity of the free boundary under a uniform thickness assumption on u=0. Lastly, we extend these results to the parabolic setting.
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| 19. |
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| 20. |
- Lewis, John L., et al.
(author)
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Regularity of flat free boundaries in two-phase problems for the p-Laplace operator
- 2012
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In: Annales de l'Institut Henri Poincare. Analyse non linéar. - : European Mathematical Society - EMS - Publishing House GmbH. - 0294-1449 .- 1873-1430. ; 29:1, s. 83-108
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Journal article (peer-reviewed)abstract
- In this paper we continue the study in Lewis and Nystrom (2010) [19], concerning the regularity of the free boundary in a general two-phase free boundary problem for the p-Laplace operator, by proving regularity of the free boundary assuming that the free boundary is close to a Lipschitz graph.
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| 21. |
- Lindgren, Erik, et al.
(author)
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On the two-phase membrane problem with coefficients below the Lipschitz threshold
- 2009
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In: Annales de l'Institut Henri Poincare. Analyse non linéar. - : European Mathematical Society - EMS - Publishing House GmbH. - 0294-1449 .- 1873-1430. ; 26:6, s. 2359-2372
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Journal article (peer-reviewed)abstract
- We study the regularity of the two-phase membrane problem, with coefficients below the Lipschitz threshold. For the Lipschitz coefficient case one can apply a monotonicity formula to prove the C-1,C-1-regularity of the solution and that the free boundary is, near the so-called branching points, the union of two C-1-graphs. In our case, the same monotonicity formula does not apply in the same way. In the absence of a monotonicity formula, we use a specific scaling argument combined with the classification of certain global solutions to obtain C-1,C-1-estimates. Then we exploit some stability properties with respect to the coefficients to prove that the free boundary is the union of two Reifenberg vanishing sets near so-called branching points.
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| 22. |
- Pinchover, Yehuda, et al.
(author)
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A Liouville-type theorem for the p-Laplacian with potential term
- 2008
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In: Annales de l'Institut Henri Poincare. Analyse non linéar. - : European Mathematical Society - EMS - Publishing House GmbH. - 0294-1449 .- 1873-1430. ; 25:2, s. 357-368
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Journal article (peer-reviewed)abstract
- In this paper we prove a sufficient condition, in terms of the behavior of a ground state of a singular p-Laplacian problem with a potential term, such that a nonzero subsolution of another such problem is also a ground state. Unlike in the linear case (p = 2), this condition involves comparison of both the functions and of their gradients.
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| 23. |
- Shahgholian, Henrik, et al.
(author)
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The obstacle problem with singular coefficients near Dirichlet data
- 2017
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In: Annales de l'Institut Henri Poincare. Analyse non linéar. - : Elsevier. - 0294-1449 .- 1873-1430. ; 34:2, s. 293-334
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Journal article (peer-reviewed)abstract
- In this paper we study the behaviour of the free boundary close to its contact points with the fixed boundary B boolean AND {x1 = 0} in the obstacle type problem {div(x(1)(a) del u) = X-{u>0} in B+, u=0 on B boolean AND {x(1) = 0} where a < 1, B+ = B boolean AND {x(1) > 0}, B is the unit ball in R-n and n > 2 is an integer. Let Gamma = B+ boolean AND partial derivative{u > 0} be the free boundary and assume that the origin is a contact point, i.e. 0 epsilon (Gamma) over bar. We prove that the free boundary touches the fixed boundary uniformly tangentially at the origin, near to the origin it is the graph of a C-1 function and there is a uniform modulus of continuity for the derivatives of this function.
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| 24. |
- Strömqvist, Martin, 1982-
(author)
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Harnack's Inequality for Parabolic Nonlocal Equations
- 2019
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In: Annales de l'Institut Henri Poincare. Analyse non linéar. - : European Mathematical Society - EMS - Publishing House GmbH. - 0294-1449 .- 1873-1430. ; 36:6, s. 1709-1745
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Journal article (peer-reviewed)abstract
- The main result of this paper is a nonlocal version of Harnack's inequality for a class of parabolic nonlocal equations. We additionally establish a weak Harnack inequality as well as local boundedness of solutions. None of the results require the solution to be globally positive.
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| 25. |
- Wahlberg, Karin, et al.
(author)
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Maternal polymorphisms in glutathione-related genes are associated with maternal mercury concentrations and early child neurodevelopment in a population with a fish-rich diet
- 2018
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In: Environment International. - : Elsevier BV. - 0160-4120 .- 1873-6750. ; 115, s. 142-149
-
Journal article (peer-reviewed)abstract
- Introduction: Glutathione (GSH) pathways play a key role the metabolism and elimination of the neurotoxicant methylmercury (MeHg). We hypothesized that maternal genetic variation linked to GSH pathways could influence MeHg concentrations in pregnant mothers and children and thereby also affect early life development. Methods: The GCLM (rs41303970, C/T), GCLC (rs761142, T/G) and GSTP1 (rs1695, A/G) polymorphisms were genotyped in 1449 mothers in a prospective study of the Seychellois population with a diet rich in fish. Genotypes were analyzed in association with maternal hair and blood Hg, fetal blood Hg (cord blood Hg), as well as children's mental (MDI) and motor development (PDI; MDI and PDI assessed by Bayley Scales of Infant Development at 20 months). We also examined whether genotypes modified the association between Hg exposure and developmental outcomes. Results: GCLC rs761142 TT homozygotes showed statistically higher mean maternal hair Hg (4.12 ppm) than G carriers (AG 3.73 and GG 3.52 ppm) (p = 0.037). For the combination of GCLC rs761142 and GCLM rs41303970, double homozygotes TT + CC showed higher hair Hg (4.40 ppm) than G + T carriers (3.44 ppm; p = 0.018). No associations were observed between GSTP1 rs1695 and maternal hair Hg or between any genotypes and maternal blood Hg or cord blood Hg. The maternal GSTP1 rs1695 rare allele (G) was associated with a lower MDI among children (β = −1.48, p = 0.048). We also observed some interactions: increasing Hg in maternal and cord blood was associated with lower PDI among GCLC rs761142 TT carriers; and increasing Hg in hair was associated with lower MDI among GSTP1 rs1695 GG carriers. Conclusions: Maternal genetic variation in genes involved in GSH synthesis is statistically associated with Hg concentrations in maternal hair, but not in maternal or fetal blood. We observed interactions that suggest maternal GSH genetics may modify associations between MeHg exposure and neurodevelopmental outcomes.
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